Patent Publication Number: US-2021167345-A1

Title: Battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2019-0157487, filed on Nov. 29, 2019, in the Korean Intellectual Property Office, and entitled: “Battery Pack,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a battery pack. 
     2. Description of Related Art 
     A secondary battery may be charged and discharged, unlike a primary battery that may not be recharged. A secondary battery may be used as an energy source for mobile devices, electric vehicles, hybrid vehicles, electric bicycles, uninterruptible power supplies, and so on, and is used in the form of a single battery cell depending on types of external devices to be applied, or is used in the form of a battery pack in which multiple battery cells are connected to each other to be composed of one unit. 
     Small mobile devices such as mobile phones may operate for a predetermined period of time with an output and capacity of a single battery, but when electric vehicles and hybrid vehicles that consume much power require long-time driving and high-power driving, a battery pack may be used due to an output and a capacity, and the battery pack may increase an output voltage or an output current according to the number of built-in battery cells. 
     SUMMARY 
     The embodiments may be realized by providing a battery pack including battery cells bounded by an imaginary rectangular envelope including a pair of long sides and a pair of short sides extending to linearly surround an outer periphery of the battery cells across an outer circumference of the battery cells; and bus bars that electrically connect at least some of the battery cells to each other, the bus bars being arranged to extend in a zig-zag shape along a short side direction of the imaginary rectangular envelope. 
     Each of the battery cells may be a circular battery cell, and the battery cells may be arranged in an offset manner such that one battery cell is partially between adjacent battery cells. 
     The battery cells may be arranged such that a straight line of battery cells extend along a long side direction of the imaginary rectangular envelope; and a zig-zag line of battery cells extend along the short side direction of the imaginary rectangular envelope. 
     The bus bars may be arranged in the zig-zag shape while connecting adjacent battery cells along the short side direction of the imaginary rectangular envelope. 
     The bus bars may be arranged such that some of the bus bars are arranged in the zig-zag shape along the short side direction of the imaginary rectangular envelope; and remaining ones of the bus bars are arranged to extend lengthwise in the long side direction of the imaginary rectangular envelope. 
     A number of bus bars arranged in the zig-zag shape along the short side direction of the imaginary rectangular envelope may be greater than a number of bus bars arranged to extend lengthwise in the long side direction of the imaginary rectangular envelope. 
     The battery cells may include a low-potential battery cell having a lowest potential and a high-potential battery cell having a highest potential, and first and second output terminals may be respectively connected to the low-potential battery cell and the high-potential battery cell. 
     The first and second output terminals may be arranged along a long side direction of the imaginary rectangular envelope. 
     The battery pack may further include first and second fuse terminals respectively connected to a pair of adjacent battery cells between the low-potential battery cell and the high-potential battery cell in an electrical connection direction in which the bus bars are arranged. 
     The bus bars may include a low voltage portion extending from the first output terminal to the first fuse terminal; and a high voltage portion extending from the second output terminal to the second fuse terminal. 
     The first and second fuse terminals may be respectively close to the first and second output terminals in the electrical connection direction in which the bus bars are arranged. 
     The low voltage portion and the high voltage portion may be formed asymmetrically with respect to a virtual line that crosses between the first and second fuse terminals and is parallel to the short side direction of the imaginary rectangular envelope. 
     A number of bus bars in the high voltage portion may be larger than a number of bus bars in the low voltage portion. 
     The high voltage portion may include a high voltage deflection portion that crosses the virtual line toward the low voltage portion in the long side direction of the imaginary rectangular envelope. 
     The low voltage portion may include a low voltage deflection portion close to a side opposite to the high voltage deflection portion in the short side direction of the imaginary rectangular envelope and spaced apart from the high voltage deflection portion. 
     The low voltage deflection portion may be arranged at a position proximate to the first and second fuse terminals in the short side direction of the imaginary rectangular envelope, and the high voltage deflection portion may be arranged at a position distal to the first and second fuse terminals in the short side direction of the imaginary rectangular envelope. 
     The high voltage deflection portion may extend longer in the long side direction of the imaginary rectangular envelope than in the short side direction of the imaginary rectangular envelope, and the low voltage deflection portion may extend relatively longer in the short side direction of the imaginary rectangular envelope than in the long side direction of the imaginary rectangular envelope. 
     The bus bars may be alternately arranged over and below the battery cells in a height direction of the battery cells. 
     The battery pack may further include a cell holder in which the battery cells are accommodated, wherein the bus bars are alternately arranged over and below the cell holder in the height direction of the battery cells. 
     The battery pack may include arrays of the bus bars arranged to extend in the zig-zag shape along the short side direction of the imaginary rectangular envelope, the arrays being repeatedly arranged along a long side direction of the imaginary rectangular envelope. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will be apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
         FIG. 1  is an exploded perspective view of a battery pack according to an embodiment; 
         FIGS. 2 and 3  illustrate perspective views of battery cells of  FIG. 1 ; 
         FIG. 4  is a view of the battery cell of  FIG. 3  and showing cooling flow paths; 
         FIG. 5  is a view of an arrangement of multiple bus bars or an electrical connection of battery cells in which multiple bus bars are arranged; 
         FIGS. 6A to 6C  are views of electrical connections according to a comparative example; 
         FIG. 7  is an exploded perspective view of a structure of a cell holder in which battery cells are assembled; 
         FIG. 8  is an exploded perspective view of an exhaust hole and an exhaust pipe of  FIG. 7 ; 
         FIG. 9  is a view of assembly of a bus bar and a cell holder; 
         FIG. 10  is a view of a structure of a circuit board illustrated in  FIG. 1 ; 
         FIG. 11  is a view of a potting resin and an adhesive resin respectively formed in a filling hole and a coupling opening region of  FIG. 10 ; 
         FIG. 12  is a cross-sectional view taken along line XII-XII of  FIG. 10 ; 
         FIG. 13  is a view of first and second opening regions of  FIG. 10 ; 
         FIGS. 14 and 15  illustrate a separation member of  FIG. 1  showing opposite surfaces of upper and lower separation members, respectively; 
         FIG. 16  is a view of a spatial separation of a cooling medium and an exhaust path of a cooling flow path, which is made by the separation member; and 
         FIG. 17  is a perspective view of an upper duct and a lower duct. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art. 
     In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or element, it can be directly on the other layer or element, or intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout. 
     As used herein, the terms “or” and “and/or” include any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     Hereinafter, a battery pack according to an embodiment will be described with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view of a battery pack according to an embodiment;  FIGS. 2 and 3  illustrate perspective views of battery cells of  FIG. 1 ;  FIG. 4  is a view of the battery cell of  FIG. 3  and showing cooling flow paths;  FIG. 5  is a view of an arrangement of multiple bus bars or an electrical connection of battery cells in which multiple bus bars are arranged;  FIGS. 6A to 6C  are views schematically showing electrical connections according to a comparative example;  FIG. 7  is an exploded perspective view of a structure of a cell holder in which battery cells are assembled;  FIG. 8  is an exploded perspective view of an exhaust hole and an exhaust pipe illustrated in  FIG. 7 ;  FIG. 9  is a view of assembly of a bus bar and a cell holder;  FIG. 10  is a view of a structure of a circuit board of  FIG. 1 ;  FIG. 11  is a view of a potting resin and an adhesive resin respectively formed in a filling hole and a coupling opening region of  FIG. 10 ;  FIG. 12  is a cross-sectional view taken along line XII-XII of  FIG. 10 ;  FIG. 13  is a view of first and second opening regions of  FIG. 10 ;  FIGS. 14 and 15  illustrate a separation member of  FIG. 1  showing opposite surfaces of upper and lower separation members, respectively;  FIG. 16  is a view of a spatial separation of a cooling medium and an exhaust path of a cooling flow path, which is made by the separation member; and  FIG. 17  is a perspective view of an upper duct and a lower duct. 
     Referring to  FIGS. 4 and 5 , a battery pack according to an embodiment may include battery cells  10  of one group (e.g., a first group of battery cells  10 ) surrounded or bounded by an imaginary rectangular envelope S 1  and S 2  including a pair of long sides S 1  and a pair of short sides S 2  extending to linearly surround an outer periphery of the battery cells  10  of one group across an outer circumference of the battery cells  10  of one group forming the battery pack. Bus bars  120  of one group (e.g., a first group of bus bars  120 ) that electrically connect the battery cells  10  of one group to each other and may be arranged to electrically connect at least some of the battery cells  10  of one group and may be arranged in a transverse direction (e.g., approximately a short side direction Z 2  that is different from a long side direction Z 1  of the envelope S 1  and S 2 ), e.g., the bus bars may extend in a zig-zag shape. 
     Hereinafter, a battery pack according to an embodiment will be described more specifically. 
     Referring to  FIGS. 2 to 5 , the battery cells  10  may each include an upper end portion  10   a  and a lower end portion  10   b  in a height direction and may be a circular battery cell  10  having an outer circumferential surface  10   c  of a cylindrical shape between the upper end portion  10   a  and the lower end portion  10   b . First and second electrodes  11  and  12  having different polarities may be respectively on the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . In an implementation, the first and second electrodes  11  and  12  of the battery cell  10  may respectively correspond to a first polarity (e.g., cathode) and a second polarity (e.g., anode) of the battery cell  10  which are opposite to each other. In an implementation, one of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , e.g., the lower end portion  10   b , may form the first electrode  11  as a whole, and the other, e.g., the upper end portion  10   a , may have a central portion that is the second electrode  12  and a rim portion that is the first electrode  11 . In an implementation, in the battery cell  10  illustrated in  FIG. 3 , the whole lower end portion  10   b  and the rim portion of the upper end portion  10   a  may be covered with a can N integrally extending so that the whole lower end portion  10   b  and the rim portion of the upper end portion  10   a  form the first electrode  11  to have the same polarity, and the central portion of the upper end portion  10   a  corresponding to a cap assembly E electrically insulated from the can N forming the first electrode  11  may form the second electrode  12  having a different polarity from the first electrode  11 . 
     In an implementation, a circuit board  130  extending across the multiple battery cells  10  may have a coupling hole CH (see  FIG. 1 ) exposing rim portions of the upper end portions  10   a  of a pair of adjacent battery cells  10  therein, and the rim portions of the upper end portions  10   a  of the battery cells  10  exposed through the coupling hole CH may form the first electrodes  11  of the same polarity. In an implementation, the adjacent battery cells  10  exposed through the same coupling hole CH may be arranged in a vertically inverted pattern in a height direction of the battery cells  10 , and the rim portions of the upper end portions  10   a  of the battery cells  10  may form the first electrodes  11  of the same polarity, regardless of the vertical arrangement of the battery cells  10 . As can be seen in  FIG. 3 , the can N forming the first electrode  11  may extend from the rim portion of the upper end portion  10   a  to the lower end portion  10   b  as a whole, and thereby, all of the rim portion of the upper end portion  10   a  of the battery cell  10  and the rim portion of the lower end portion  10   b  of the battery cell  10  have the first electrodes  11  of the same polarity regardless of a vertical arrangement of the battery cell  10 . 
     As will be described in greater detail below, upper end portions  10   a  of the adjacent battery cells  10  may be electrically connected to each other by a bus bar  120 , and lower end portions  10   b  of the adjacent battery cells  10  may be electrically connected to each other by another bus bar  120 . In an implementation, the bus bar  120  may connect the central portions of the upper end portions  10   a  of the adjacent battery cells  10 , and the bus bar  120  may connect the central portions of the lower end portions  10   b  of the adjacent battery cells  10 . As illustrated in  FIG. 3 , the central portion of the upper end portion  10   a  may be the cap assembly E forming the second electrode  12 , and the central portion of the lower end portion  10   b  may be formed as the can N forming the first electrode  11 , and the central portion of the upper end portion  10   a  of the battery cell  10  or the central portion of the lower end portion  10   b  of the battery cell  10  may form the first electrode  11  or the second electrode  12 . Throughout the present specification, that the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  respectively have the first electrode  11  and the second electrode  12  or respectively form the second electrode  12  and the first electrode  11  may indicate that the central portions of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  respectively have the first electrode  11  and the second electrode  12  or respectively have the second electrode  12  and the first electrode  11 . In addition, throughout the present specification, connecting the upper end portions  10   a  to the lower end portions  10   b  of the adjacent battery cells  10  through that the bus bars  120  may indicate connecting the central portions of the upper end portions  10   a  to each other through the bus bars  120  and connecting the central portions of the lower end portions  10   b  to each other through the bus bars  120 . 
     Throughout the present specification, the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  may be divided according to positions rather than the first and second electrodes  11  and  12  and may respectively indicate an end portion formed at an upper position and an end portion formed at a lower position in a height direction. In an implementation, the upper end portions  10   a  of the adjacent battery cells  10  may form the first electrode  11  or the second electrode  12  having the same polarity or may also form the first and second electrodes  11  and  12  having different polarities depending on the specific arrangement of the battery cells  10 . 
     Referring to  FIG. 2 , in one embodiment, the adjacent battery cells  10  may be arranged in an inverted pattern in a height direction, and accordingly, the upper end portions  10   a  of the adjacent battery cells  10  may form the first and second electrodes  11  and  12  having different polarities, and the lower end portions  10   b  of the adjacent battery cells  10  may also form the first and second electrodes  11  and  12  having different polarities. 
     The battery cells  10  may be electrically connected to other adjacent battery cells  10 , and the first and second electrodes  11  and  12  of the battery cells  10  may be connected in series to electrodes having different polarities while the battery cells  10  adjacent in an electrical connection direction are arranged in an inverted pattern in a height direction. In an implementation, each of a group of the battery cells  10  forming a battery pack may be connected in series with the adjacent battery cell  10 , and a battery pack according to an embodiment may not include a parallel connection between the adjacent battery cells  10 . Accordingly, in one embodiment, the adjacent battery cells  10  in an electrical connection direction may be arranged in a vertically inverted pattern, and a series connection between the first and second electrodes  11  and  12  having different polarities may be formed by connecting the upper end portions  10   a  to each other or connecting the lower end portions  10   b  to each other. In an implementation, along the electrical connection direction, the battery cells  10  may alternate in an up or down direction, e.g., in which the first electrode  11  of one battery cell  10  faces upwardly and the first electrode of the next battery cell  10  faces downwardly. 
     Throughout this specification, the electrical connection direction of the battery cells  10  indicates a direction in which the adjacent battery cells  10  are electrically connected to each other and may include different directions interconnected through an arrangement of multiple bus bars  120  rather than indicating a certain one direction (e.g., would not indicate a simple linear direction). 
     In an implementation, the electrical connection direction of the battery cell  10  may be formed in a zig-zag shape. As will be described in greater detail below, the battery cell  10  may a circular battery cell, and multiple battery cells  10  may be densely arranged by arranging the battery cells  10  at alternate positions so as to be between adjacent battery cells  10  (e.g., the battery cells  10  may be in an offset arrangement such that the battery cells may be tightly packed). As such, the multiple battery cells  10  arranged at alternate positions may be electrically connected to each other by the multiple bus bars  120  arranged in a zig-zag shape, and the electrical connection direction of the zig-zag shape may be formed in a direction in which the multiple bus bars  120  are arranged. 
     Referring to  FIG. 2 , a group of the battery cells  10  forming a battery pack may be electrically connected to each other in the electrical connection direction in which the multiple bus bars  120  are arranged, and the battery cell  10  forming one end in the electrical connection direction and the battery cell  10  forming the other end may respectively correspond to a low-potential battery cell  10  (having the lowest potential) and a high-potential battery cell  10  (having the highest potential) among a group of battery cells  10 . In an implementation, first and second output terminals  121  and  122  may be respectively connected to the low-potential battery cell  10  and the high-potential battery cell  10 . 
     The first and second output terminals  121  and  122  may mediate an electrical connection between a group of the battery cells  10  electrically connected to each other and an external device, and a group of the battery cells  10  may supply a discharge power to an external load through the first and second output terminals  121  and  122  or may receive a charging power from an external charger through the first and second output terminals  121  and  122 . 
     First and second fuse terminals  123  and  124  may be between the first and second output terminals  121  and  122  to be connected to a fuse box forming a charge/discharge path by being between the first and second output terminals  121  and  122 . The fuse box may form a charge/discharge path between the first and second output terminals  121  and  122 , and the charge/discharge path of a group of the battery cells  10  may pass through a fuse box (through the first and second fuse terminals  123  and  124  connected to the fuse box. A fuse for blocking an overcurrent may be installed in the fuse box and may block the charge/discharge path in response to the overcurrent. 
     In an implementation, the first and second fuse terminals  123  and  124  may be connected to the battery cell  10  between the low-potential battery cell  10  at one end and the high-potential battery cell  10  at the other end in an electrical connection direction of the battery cells  10  in which the multiple bus bars  120  are arranged, and may be formed in pairs to be respectively connected to a pair of the battery cells  10  electrically connected to each other through a fuse box connected to the first and second fuse terminals  123  and  124 . In an implementation, the first and second fuse terminals  123  and  124  may respectively correspond to fuse terminals close to the first and second output terminals  121  and  122  in an electrical connection direction of the battery cells  10  in which multiple bus bars  120  are arranged. 
     Cooling flow paths F may be between the adjacent battery cells  10 . A cooling medium flowing through the cooling flow paths F may be in contact with the battery cells  10  to cool the battery cells  10 . The cooling flow path F may penetrate a space between the adjacent battery cells  10  in a height direction of the battery cell  10  and extend to the outside of the battery cell  10 , and the cooling flow path F formed to penetrate almost the whole battery pack may be in fluid communication with the outside of the battery pack through an inlet and an outlet of the cooling flow path F. In this case, the cooling flow path F may extend across the battery pack to penetrate almost the whole battery pack in the height direction of the battery cell  10 . The cooling flow path F will be described below in greater detail. 
     Referring to  FIG. 3 , a vent portion  13  may be formed at at least one end portion of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . When the end portion of the battery cell  10  in which the vent portion  13  is formed among the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  is referred to as one end portion of the battery cell  10 , the vent portion  13  may be formed along a rim of the one end portion of the battery cell  10 . In an implementation, the vent portion  13  may be formed along a rim of the second electrode  12  formed at a central position of the one end portion of the battery cell  10 , and may be formed along a rim of the one end portion of the battery cell  10 . 
     In an implementation, the vent portion  13  may include multiple vent portions  13  spaced apart from each other along a rim in one end portion of the battery cell  10 . The vent portion  13  may be for relieving an internal pressure of the battery cell  10 , e.g., the vent portion  13  may correspond to a portion formed with a relatively weak strength in one end portion of the battery cell  10 . When the internal pressure of the battery cell  10  increases above a preset critical pressure (corresponding to a breakage pressure of the vent portion  13 ), the vent portion  13  may be broken to relieve the internal pressure. 
     Referring to  FIG. 1 , exhaust gas emitted through the vent portion  13  according to the internal pressure of the battery cell  10  may be emitted to the outside of a battery pack along an exhaust path of which one side is closed by a block region  144  of the separation member  140 . In an implementation, the block region  144  corresponding to the vent portion  13  of the battery cell  10  may be formed in the separation member  140 , and the exhaust gas exhausted through the vent portion  13  may be emitted to the outside of a battery pack through an exhaust path formed between the block region  144  of the separation member  140  and the battery cell  10 . The separation member  140  and the exhaust path will be described in greater detail below. 
     Hereinafter, an arrangement of the battery cells  10  and a position of the cooling flow path F between the battery cells  10  according to an embodiment will be described with reference to  FIG. 4 . 
     The cooling flow path F may be between the adjacent battery cells  10 . In an implementation, the battery cell  10  may be a circular battery cell, and the battery cells  10  may be arranged at alternate positions to be between the adjacent battery cells  10 , and thereby, the multiple battery cells  10  may be densely arranged, and by densely arranging the battery cells  10  by using spaces between the adjacent battery cells  10 , an invalid or unused space may be reduced and a battery pack having a high energy density per area may be provided. 
     In an implementation, the battery cells  10  may be arranged in or along a column direction Z 1  of the battery cells  10 , and the battery cells  10  in adjacent rows may be arranged at alternate positions so that the battery cells  10  in adjacent rows are therebetween. In an implementation, the column direction Z 1  of the battery cells  10  may indicate one direction in which the battery cells  10  are arranged when the battery cells  10  are arranged linearly in one direction. The column direction Z 1  of the battery cells  10  may be different from a direction in which the multiple battery cells  10  are electrically connected to each other, e.g., an electrical connection direction of the battery cells  10 , and the column direction Z 1  of the battery cells  10  may indicate one direction in which the battery cells  10  are arranged without considering an electrical connection state of the battery cells  10 . 
     In an implementation, the battery cells  10  may be linearly arranged in the column direction Z 1  and may be arranged in a zig-zag shape in a transverse direction (e.g., Z 2 ) crossing the column direction Z 1 . In an implementation, an arrangement of the battery cells  10  of which outer circumferential surfaces are arranged adjacent may be formed linearly in the column direction Z 1  and may be formed in a zig-zag shape in a transverse direction crossing the column direction Z 1 . In this case, the arrangement of the battery cells  10  of which outer circumferential surfaces are arranged adjacent may indicate an arrangement of the battery cells  10  of which outer circumferential surfaces are arranged close to each other and may indicate, e.g., an arrangement of the battery cells  10  of which outer circumferential surfaces are arranged close to each other so that an interval between the outer circumferential surfaces of the adjacent battery cells  10  becomes a smallest interval SG. In an implementation, the smallest interval SG may be set for the purpose of ensuring electrical insulation between the adjacent battery cells  10  and ensuring sufficient heat dissipation, e.g., the smallest interval SG may be set to approximately 1 mm. 
     In an implementation, a group of battery cells  10  forming a battery pack may be surrounded or bounded by (e.g., contained entirely within) a rectangular envelope (e.g., imaginary rectangular envelope) S 1  and S 2  including a pair of long sides S 1  and a pair of short sides S 2  extending to linearly surround an outer periphery of the group of battery cells  10  across an outer circumference of the group of battery cells  10 , the column direction Z 1  in which the battery cells  10  are arranged linearly may correspond to a direction parallel to the long side S 1  of the envelope S 1  and S 2 , and a transverse direction in which the battery cells  10  are arranged in a zig-zag shape may correspond to a direction close to the short side S 2  of the envelope S 1  and S 2 . 
     Referring to  FIG. 4 , the battery cells  10  in first and second rows R 1  and R 2  may be densely arranged toward each other so that the battery cells  10  in the first row R 1  are (e.g., at least partially) between the battery cells  10  in the second row R 2 , and similarly, the battery cells  10  in the second row R 2  and a third row R 3  may be densely arranged toward each other so that the battery cells  10  in the second row R 2  are (e.g., at least partially) between the battery cells  10  in the third row R 3 . 
     Any one of the battery cells  10  may be between the adjacent battery cells  10  and the three battery cells  10  may be arranged so that outer circumferences thereof are adjacent, and in this case, the cooling flow path F may be between the three battery cells  10  of which circumferences are adjacent. The cooling flow path F may be in an extra region, which is not occupied by the battery cells  10 , between the three battery cells  10  of which outer circumferences are adjacent, e.g., a valley region therebetween. 
     In an implementation, the cooling flow path F may be between the battery cells  10  in the first and second rows R 1  and R 2  adjacent to each other, and one cooling flow path F may be between two battery cells  10  in the first row R 1  and one battery cell  10  in the second row R 2 , and the one cooling flow path F may also be between two battery cells  10  in the second row R 2  and one battery cell  10  in the first row R 1 . Similarly, the cooling flow path F may be between the battery cells  10  in the second and third rows R 2  and R 3  adjacent to each other, and one cooling flow path F may be between two battery cells  10  in the second row R 2  and one battery cell  10  in the third row R 3 , and the one cooling flow path F may also be between two battery cells  10  in the third row R 3  and one battery cell  10  in the second row R 2 . 
     Referring to  FIG. 4 , six cooling flow paths F may be in the outer circumferential direction of one battery cell  10  included in the second row R 2 . In an implementation, one battery cell  10  in the second row R 2  may form many valley regions between six battery cells  10  (battery cells  10  in the first to third columns R 1 , R 2 , and R 3 ) in the outer circumferential direction, and a total of six valley regions may be formed by sequentially forming valley regions between two battery cells  10  in an outer circumferential direction, and a total of six cooling flow paths F may be formed by forming the cooling flow paths F for each valley region. 
     Hereinafter, an arrangement of the multiple bus bars  120  or an electrical connection of the battery cells  10  in which the multiple bus bars  120  are arranged will be described with reference to  FIGS. 4 and 5 . Referring to  FIG. 5 , an upper bus bar  120   a  (see  FIG. 1 ) and a lower bus bar  120   b  (see  FIG. 1 ) are illustrated together, and all electrical connections of the upper bus bar  120   a  and the lower bus bar  120   b  are illustrated, for the sake of easy understanding. Hereinafter, the upper bus bar  120   a  and the lower bus bar  120   b  will be collectively referred to as the bus bar  120  without distinction. However, in one embodiment, an electrical connection illustrated in  FIG. 5  may be implemented through the upper bus bar  120   a  and the lower bus bar  120   b  alternately arranged above and below the cell holder  110 . Meanwhile, numbers illustrated in  FIG. 5  may indicate an order of the battery cells  10  counted in an electrical connection direction. 
     Referring to  FIGS. 4 and 5 , the multiple bus bars  120  electrically connecting adjacent battery cells  10  to each other may be arranged in a zig-zag shape. In an implementation, the battery cells  10  may circular battery cells, and the battery cells  10  may be arranged at alternate positions so as to be between adjacent battery cells  10 , and thus, the multiple battery cells  10  may be densely arranged. 
     In an implementation, assuming that a group of battery cells  10  forming a battery pack is surrounded by the imaginary rectangular envelope S 1  and S 2  including a pair of long sides S 1  and a pair of short sides S 2  extending to linearly surround an outer periphery of the group of battery cells  10  across an outer circumference of the group of battery cells  10 , the group of battery cells  10  forming a battery pack may include an arrangement in the column direction Z 1  linearly extending in parallel with a long side direction Z 1  and an arrangement in a transverse direction extending in a zig-zag shape approximately in a short side direction Z 2 . In an implementation, the transverse direction extending of the zig-zag shape may correspond to a direction closer to the short side direction Z 2  than to the long side direction Z 1  of the group of battery cells  10  and may correspond to a direction close to the short side direction Z 2  shorter than the long side S 1 . In this case, the multiple bus bars  120  electrically connecting the adjacent battery cells  10  may be arranged in a zig-zag shape while connecting the adjacent battery cells  10  along the arrangement of the battery cells  10  in the transverse direction extending in a zig-zag shape. 
     In an implementation, the arrangement of the multiple bus bars  120  or the electrical connection direction of the battery cells  10  in which the multiple bus bars  120  are arranged may not formed in the column direction Z 1  parallel to the long side direction Z 1 , but rather may be formed in a transverse direction closer in direction to the short side direction Z 2  (shorter than the long side S 1 ), and thus, a potential (voltage) difference between the battery cells  10  of one array electrically connected to each other in the transverse direction Z 2  and the battery cells  10  of an adjacent array electrically connected to each other in the transverse direction may be reduced, e.g., by reducing a potential difference between the battery cells  10  of an adjacent array in the column direction Z 1 , a risk of an electrical short-circuit between the adjacent battery cells  10  may be reduced, and safety of a battery pack may be increased. In an implementation, the battery cells  10  of the one array and the adjacent array may be electrically connected through an arrangement of the bus bars  120  extending in a transverse direction in a zig-zag shape, and the battery cells  10  of the one array and the adjacent array may be arranged adjacent in the column direction Z 1  crossing the transverse direction. In this case, a greatest potential difference (highest voltage) between the battery cells  10  arranged adjacent in the column direction Z 1 , e.g., a greatest potential difference (highest voltage) between the battery cell  10  (seventh battery cell) included in the one array and the battery cell  10  (18 th  battery cell) included in an adjacent array may be calculated by multiplying the number of bus bars  120  electrically connecting the battery cells  10  (e.g.,  11 ) and a full charging voltage (e.g., 4.2 V) of each of the battery cells  10 . This may be because a difference may occur between the adjacent battery cells  10  connected by the bus bars  120  by a full charging voltage. In an implementation, the greatest potential difference (the highest voltage) between the adjacent battery cells  10  may be 46.2 V. As will be described below, a battery pack according to an embodiment may be formed as a 72-cell structure including 72 battery cells  10 , and include a high-voltage deflection unit HVe for compatibility with a 64-cell structure including 64 battery cells  10 , and in this case, a greatest potential difference (highest voltage) between the adjacent battery cells  10 , e.g., a 19 th  battery cell  10  and a 40 th  battery cell  10  may be 88.2 V. Even in this case, when compared to that the greatest potential difference (highest voltage) between the adjacent battery cells  10  exceeds 200 V or approaches 200 V in the comparative examples illustrated in  FIGS. 6A to 6C , it may be determined that safety of a battery pack is increased. 
     If the multiple bus bars  120  were to be arranged in the column direction Z 1  rather than a transverse direction Z 2 , a relatively large number of battery cells  10  may be arranged, and a relatively large number of bus bars  120  may be arranged for the number of relatively large number of battery cells  10 . Thus, the highest voltage between the adjacent battery cells  10  may increase by that amount, and a risk of an electrical short-circuit between the adjacent battery cells  10  may be increased. 
     Referring to  FIG. 5 , in one embodiment, a group of the bus bars  120  forming a battery pack may include the bus bars  120  extending in a zig-zag shape in the transverse direction, and the bus bar  120  in the column direction Z 1 , and an arrangement of the bus bars  120  or an electrical connection direction of the battery cells  10  in which the bus bars  120  are arranged may be considered as following or roughly extending along the transverse direction. In an implementation, whether the group of bus bars  120  forming the battery pack follows the transverse direction Z 2  or the column direction Z 1  may be determined through a relative comparison of the number of bus bars  120  in the transverse direction Z 2  (e.g., a number of bus bars  120  having a long axis roughly aligned with the transverse direction Z 2 ) and the number of bus bars  120  in the column direction Z 1  (e.g., a number of bus bars  120  having a long axis roughly aligned with the column direction Z 1 ). In an implementation, one bus bar  120  may be arranged in the column direction Z 1  per five bus bars  120  approximately in the transverse direction Z 2 , and in this case, an arrangement of the bus bars  120  or an electrical connection direction of the battery cells  10  in which the bus bars  120  are arranged may be considered as following the transverse direction Z 2 , rather than the column direction Z 1 . 
     In an implementation, the arrangement of the bus bars  120  or the electrical connection direction of the battery cells  10  in which the bus bars  120  are arranged may be formed in a transverse direction Z 2  and extending in a zig-zag shape. The arrangement of the bus bars  120  extending in the transverse direction Z 2  may be repeated in the column direction Z 1  by using the arrangement of the bus bars  120  extending in the transverse direction Z 2  as a unit. In an implementation, the first and second output terminals  121  and  122  may be arranged or spaced apart in the column direction Z 1 , e.g., in or along the long side direction Z 1  of the envelope S 1  and S 2 . The first and second output terminals  121  and  122  may be arranged in or along the long side direction Z 1  of the envelope S 1  and S 2  surrounding the group of battery cells  10 , and thereby, an electrical connection in a transverse direction Z 2  (e.g., closer in direction to to the short side direction Z 2  of the envelope S 1  and S 2 ) may be formed, and accordingly, the greatest potential difference (highest voltage) between the adjacent battery cells  10  may be reduced. 
     As in the comparative example illustrated in  FIGS. 6A to 6C , the first and second output terminals  121  and  122  may be arranged or spaced apart in or along the short side direction Z 2  of the envelope S 1  and S 2  surrounding the group of battery cells  10 , a voltage of the adjacent battery cells  10  may be relatively increased compared to the embodiment illustrated in  FIG. 5 , and the greatest potential difference (highest voltage) may occur in the portions indicated by the dashed line oval in  FIGS. 6A to 6C , and a greatest potential difference (highest voltage) exceeding 200 V or approaching 200 V may occur. In the comparative examples illustrated in  FIGS. 6A to 6C , the greatest potential difference (highest voltage) may be 210 V, 180.6 V, and 273 V, respectively. 
     In the comparative examples illustrated in  FIGS. 6A to 6C , an arrangement of the multiple bus bars  120  or an electrical connection direction of the battery cells  10  in which the multiple bus bars  120  are arranged may be formed in the column direction Z 1  (parallel to the long side direction Z 1  of the envelope S 1  and S 2 ) rather than a transverse direction Z 2  (closer in direction to the short side direction Z 2  of the envelope S 1  and S 2 ). Thus, a potential difference between the adjacent battery cells  10  may increase, and a risk of an electric short-circuit between the adjacent battery cells  10  may be increased. In the comparative example of  FIG. 6C , an electrical connection direction of the battery cells  10  may be formed in a transverse direction closer in direction to the short side direction Z 2  of the envelope S 1  and S 2 , and an arrangement of the bus bars  120  arranged in the transverse direction may be repeated in the column direction Z 1  parallel to the long side direction Z 1  of the envelope S 1  and S 2  by using the arrangement of the bus bars  120  arranged in the transverse direction as one unit, and by repeating the arrangement of the bus bars  120  arranged in the transverse direction while reciprocating in the column direction Z 1 . The greatest potential difference (highest voltage) between the adjacent battery cells  10  in the portion indicated by the dashed line oval may increase. In an implementation, as illustrated in  FIG. 5 , an arrangement of the bus bars  120  arranged in the transverse direction may be repeated along the column direction Z 1  parallel to the long side direction Z 1  of the envelope S 1  and S 2 , but the arrangement of the bus bars  120  arranged in the transverse direction may be repeated only in one direction from one short side S 2  of the envelope S 1  and S 2  to the other short side S 2  of the envelope S 1  and S 2  in the column direction Z 1  and may not repeat while reciprocating between both short sides S 2  in one direction and an opposite direction. In an implementation, as illustrated in  FIG. 5 , the connection structure of the bus bars  120  may extend across an entire width of the battery pack in the transverse direction Z 2  in the zig zag arrangement. In an implementation, arrays of battery cells  10  that are aligned along the transverse direction Z 2  may be connected by arrays of bus bars  120  that extend in the zig zag arrangement generally along the transverse direction Z 2 . A battery cell at an end of an array of battery cells  10  may be connected to an adjacent battery cell  10  at an end of an adjacent array of battery cells  10  via a bus bar  120  that extends lengthwise in the column direction Z 1  between the adjacent arrays of battery cells  10 . 
     Referring to  FIG. 5 , in one embodiment, a group of the bus bars  120  forming a battery pack or a group of the battery cells  10  forming a battery pack may include a low voltage portion LV from the first output terminal  121  connected to the low-potential battery cell  10  having the lowest potential to the first fuse terminal  123 , and a high voltage portion HV from the second output terminal  122  connected to the high-potential battery cell  10  having the highest potential to the second fuse terminal  124 . In this case, the first and second fuse terminals  123  and  124  may indicate the fuse terminals  123  and  124  relatively close to the first and second output terminals  121  and  122  in an electrical connection direction of the battery cells  10  among a pair of the fuse terminals  123  and  124  connected to a fuse box, respectively, and may indicate the fuse terminals  123  and  124  connected to the first and second output terminals  121  and  122  in the electrical connection direction without passing through a fuse box. 
     In an implementation, the low voltage portion LV and the high voltage portion HV may cross between the first and second fuse terminals  123  and  124 , and may be asymmetrically arranged with respect to a virtual line O parallel to the short side direction Z 2  of the envelope S 1  and S 2  (e.g., passing through a center of the battery pack). In an implementation, the high voltage portion HV may include a high voltage deflection portion HVe biased toward the low voltage portion LV (e.g., crossing the virtual line O in the long side direction Z 1  of the envelope S 1  and S 2 ), and the low voltage portion LV may include a low voltage deflection portion LVe biased toward an opposite side from the high voltage deflection portion HVe in the short side direction Z 2  by avoiding the high voltage deflection portion HVe. In an implementation, the high voltage deflection portion HVe and the low voltage deflection portion LVe may be arranged opposite to each other in the short side direction Z 2  of the envelope S 1  and S 2 . The low-voltage deflection portion LVe may be arranged at a position relatively close to (e.g., proximate to) the first and second fuse terminals  123  and  124  in the short side direction Z 2  of the envelope S 1  and S 2 . The high voltage deflection portion HVe may be arranged at a location relatively distant from (e.g., distal to) the first and second fuse terminals  123  and  124 . In an implementation, the high voltage deflection portion HVe and the low voltage deflection portion LVe may extend relatively long in the long side direction Z 1  and the short side direction Z 2  of the envelope S 1  and S 2 . In an implementation, the high voltage deflection portion HVe may extend relatively longer in the long side direction Z 1  than the short side direction Z 2  so as to be biased toward the low voltage portion LV. The low voltage deflection portion LVe may extend relatively longer in the short side direction Z 2  than in the long side direction Z 1  while avoiding the high voltage deflection portion HVe. 
     In an implementation, the high voltage portion HV and the low voltage portion LV may have an asymmetric arrangement about the virtual line O, and thereby, compatibility that a battery management system (BMS) may be shared with each other may be provided in a structure (64-cell structure) in which a group of the battery cells  10  forming a battery pack is 64 and a structure (72-cell structure) in which a group of the battery cells  10  forming a battery pack is 72. In an implementation, the BMS may include a pin-map corresponding to positions of the battery cells  10  and a fuse box, and in the 64-cell structure, a fuse box is between a 32nd pin (32nd battery cell in an electrical connection direction of the battery cell  10 ) and a 33rd pin (33rd battery cell in the electrical connection direction of the battery cell  10 ). In an implementation, in the 64-cell structure, a fuse box may be located at an intermediate position in the electrical connection direction of the battery cells  10 , that is, between the 32nd battery cell  10  and the 33rd battery cell  10 . 
     In an implementation, even in the 72-cell structure illustrated in  FIG. 5 , a structure in which the fuse box is between the 32nd pin (32nd battery cell  10  in the electrical connection direction of the battery cell  10 ) and 33rd pin (33rd battery cell  10  in the electrical connection direction of the battery cell  10 ) is implemented as in the 64-cell structure, and thereby, the BMS may be used as a common component in the 64-cell structure and the 72-cell structure. That is, the BMS including the same pin-map may be commonly applied to the 64-cell structure and the 72-cell structure. 
     In an implementation, in the 72-cell structure designed to have compatibility of the BMS with the 64-cell structure, a battery management system (BMS), the number of bus bars  120  (or the battery cells  10  of the high voltage portion HV) of the high voltage portion HV may be relatively greater than the number of bus bars  120  (or the battery cells  10  of the low voltage portion LV) of the low voltage portion LV in an electrical connection direction of the battery cells  10  by using a fuse box as a boundary, and the high voltage portion HV including a relatively large number of bus bars  120  may include the high voltage deflection portion HVe biased toward the low voltage portion LV, and the low voltage portion LV may include the low voltage deflection portion LVe so as to avoid the high voltage deflection portion HVe. 
     Referring to  FIG. 7 , the battery cells  10  may be assembled to (e.g., accommodated in) the cell holder  110 . In an implementation, the cell holder  110  may have one side on or in which the battery cells  10  are assembled, and have the other side on which a hollow protrusion portion  115  connected to the cooling flow path F between the adjacent battery cells  10  protrudes. As will be described below, the hollow protrusion portion  115  may extend through the circuit board  130  on the other side of the cell holder  110 . Hereinafter, the cell holder  110  will be described in greater detail. 
     The cell holder  110  may include an upper holder  110   a  (to or in which the upper end portion  10   a  of the battery cell  10  is fitted), and a lower holder  110   b  (to or in which the lower end portion  10   b  of the battery cell  10  is fitted). In addition, except for the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  fitted to the upper holder  110   a  and the lower holder  110   b , a center position may be exposed between the upper holder  110   a  and the lower holder  110   b  in a height direction of the battery cell  10 . In this case, the cooling flow path F may be between the adjacent battery cells  10 , and the central position of the battery cell  10  exposed between the upper holder  110   a  and the lower holder  110   b  may be cooled by being directly exposed to a cooling medium flowing through the cooling flow path F. In an implementation, the cooling medium may be, e.g., low-temperature air introduced from the outside of the battery pack. In an implementation, the cooling medium may include a cooling medium in a gaseous state other than air, and may include, e.g., refrigerant gas. 
     The upper holder  110   a  and the lower holder  110   b  may include an assembly rib  111  fitted or coupled to each of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , and the assembly rib  111  may regulate an assembly position of the battery cell  10  while surrounding the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . The assembly rib  111  may protrude inwardly from a (e.g., plate-shaped) body of the cell holder  110  toward the battery cell  10  in a height direction of the battery cell  10 , and may support the battery cell  10  while surrounding the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . 
     Terminal holes  112  exposing the first and second electrodes  11  and  12  of the battery cell  10  may be in the cell holder  110 . The first and second electrodes  11  and  12  of the battery cell  10  exposed through the terminal hole  112  may be electrically connected to the other adjacent battery cells  10  through the bus bar  120 . In an implementation, the terminal hole  112  may be within a region surrounded by the assembly rib  111  to which the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  including the first and second electrodes  11  and  12  are assembled, in the cell holder  110 . 
     As illustrated in  FIG. 3 , in one embodiment, the vent portion  13  may be in at least one of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , and the vent the portion  13  may be along a rim of one end portion surrounding the second electrode  12  at one end portion of the battery cell  10 . In this case, referring to  FIG. 7 , the terminal hole  112  may be formed to have a sufficient size (e.g., diameter) so as to expose the vent portion  13  (along the rim of the one end portion surrounding the second electrode  12  of the battery cell  10 ) together with the second electrode  12  of the battery cell  10 . In an implementation, the adjacent battery cells  10  may be arranged in the inverted pattern in a height direction, and accordingly, the vent portion  13  of the battery cell  10  may be on the upper end portion  10   a  of the battery cell  10  or the lower end portion  10   b  of the battery cell  10 , depending on positions of the specific battery cells  10 , and in this case, the terminal holes  112  in the upper and lower holders  110   a  and  110   b  may have a sufficient size (e.g., diameter) to expose the vent portions  13  respectively formed in the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . 
     Referring to  FIG. 7 , exhaust gas emitted through the vent portion  13  of the battery cell  10  may flow through the exhaust path on the cell holder  110  through the terminal hole  112  of the cell holder  110  and may be emitted to the outside of the battery pack through an exhaust hole DH on one side of the cell holder  110 . In an implementation, the exhaust hole DH may be on one side of the cell holder  110 , and the exhaust hole DH may be in fluid connection with the vent portions  13  of the multiple battery cells  10  to collect the exhaust gas emitted from the vent portion  13  and emit the exhaust gas to the outside of the battery pack. In an implementation, the exhaust hole DH may be at a rim (e.g., outer edge or side) of the cell holder  110  and may be at the rim position in a long side direction of the cell holder  110 . 
     Throughout the present specification, the long side direction of the cell holder  110  may correspond to the long side direction Z 1  of the envelope S 1  and S 2  (see  FIG. 4 ) surrounding a group of battery cells  10  forming a battery pack. In an implementation, assuming that a group of battery cells  10  forming a battery pack is surrounded by a rectangular envelope S 1  and S 2  (see  FIG. 4 ) including a pair of long sides S 1  and a pair of short sides S 2  extending to linearly surround an outer periphery of the group of battery cells  10  across an outer circumference of the group of battery cells  10 , the long side direction Z 1  of the envelope S 1  and S 2  may correspond to a long side direction of the cell holder  110 . 
     Referring to  FIG. 7 , in one embodiment, the battery cells  10  may be arranged in a vertically inverted pattern in a height direction of the battery cells  10 . In an implementation, the multiple battery cells  10  may include first and second groups of the battery cells  10  arranged in a pattern that is vertically inverted from each other. In an implementation, the first group of battery cells  10  may include the vent portions  13  at the upper end portions  10   a , and the second group of battery cells  10  may include the vent portions  13  at the lower end portions  10   b.    
     Referring to  FIGS. 7 and 8 , the cell holder  110  may include an upper holder  110   a  to which the upper end portions  10   a  of the first group of battery cells  10  are assembled, and a lower holder  110   b  to which the lower end portions  10   b  of the second group of battery cells  10  are assembled. In an implementation, the upper holder  110   a  and the lower holder  110   b  may accommodate the first and second groups of battery cells therebetween and may be assembled to face each other, and may provide a space for accommodating the first and second groups of battery cells  10 . In this case, an upper exhaust hole DHa for collecting exhaust gas emitted from the upper end portions  10   a  (e.g., the vent portions  13 ) of the first group of battery cells  10  may be in an upper surface of the upper holder  110   a . A lower exhaust hole DHb for collecting exhaust gas emitted from the lower end portions  10   b  (e.g., the vent portions  13 ) of the second group of battery cells  10  may be in a lower surface of the lower holder  110   b . In this case, an exhaust path connecting the upper end portions  10   a  (e.g., the vent portions  13 ) of the first group of battery cells  10  to the upper exhaust hole DHa may be formed. In the lower surface of the lower holder  110   b , and an exhaust path connecting the lower end portions  10   b  (e.g., the vent portions  13 ) of the second group of battery cells  10  to the lower exhaust hole DHb may be in the lower surface of the lower holder  110   b . Referring to  FIG. 1 , an upper separation member  140   a  and a lower separation member  140   b  forming respective exhaust paths may be arranged on the upper surface of the upper holder  110   a  and the lower surface of the lower holder  110   b , and in this case, the exhaust paths may be respectively formed between the upper surface of the upper holder  110   a  and the upper separation member  140   a , and between the lower surface of the lower holder  110   b  and the lower separation member  140   b . In an implementation, the exhaust path may be between the upper surface of the upper holder  110   a  and a block region  144  of the upper separation member  140   a , and between the lower surface of the lower holder  110   b  and a block region  144  of the lower separation member  140   b . More detailed technical description of the upper separation member  140   a , the lower separation member  140   b , and the block regions  144  will be made below. 
     Referring to  FIGS. 7 and 8 , the upper exhaust hole DHa and the lower exhaust hole DHb may be in edges corresponding to each other of the upper holder  110   a  and the lower holder  110   b  and may be formed at, e.g., one rim of the cell holder  110  in a long side direction thereof. In an implementation, an exhaust duct DD (continuously extending in a height direction) may be in edges of the upper holder  110   a  and the lower holder  110   b  in which the upper exhaust hole DHa and the lower exhaust hole DHb are formed respectively. The exhaust duct DD may be continuously formed through the upper holder  110   a  and the lower holder  110   b  in a height direction, and when the upper holder  110   a  and the lower holder  110   b  are assembled together, some of the exhaust duct DD in the upper holder may be connected to the remaining portion of the exhaust duct DD in the lower holder  110   b  to form a complete exhaust duct DD having a single tubular shape. In an implementation, the exhaust duct DD may include a portion in the upper holder  110   a  and the remaining portion in the lower holder  110   b , and the exhaust duct DD may be divided to be formed in the upper holder  110   a  and the lower holder  110   b . For reference, throughout the present specification, the height direction may indicate a height direction of the battery cell  10  and may indicate a lengthwise (e.g., long axis) direction of the battery cell  10  as a largest dimension of the battery cell  10 . 
     The exhaust duct DD may form a space separated from an accommodation space of the battery cells  10  formed by assembling the upper holder  110   a  and the lower holder  110   b , and may be formed in a sealed structure except for a location in which the upper exhaust hole DHa that exhaust gas is introduced is connected to the lower exhaust hole DHb, and a location connected to the exhaust pipe DP from which the exhaust gas is emitted to the outside of the cell holder  110 . 
     The upper exhaust hole DHa and the lower exhaust hole DHb may be connected at both ends of the exhaust duct DD in a height direction. In an implementation, the exhaust pipe DP may be connected to a location or position between both ends of the exhaust duct DD in a height direction. In an implementation, the exhaust duct DD may continuously extend through the upper holder  110   a  and the lower holder  110   b  in a height direction to be connected to the upper exhaust hole DHa and the lower exhaust hole DHb at both ends thereof, and may be connected, at a height or position between both ends, to the exhaust pipe DP, for collecting the entire exhaust gas introduced from the upper exhaust hole DHa and the lower exhaust hole DHb to emit the gas to the outside of the cell holder  110 . In this case, the exhaust pipe DP may be connected to the exhaust duct DD at a height between upper and lower surfaces of the cell holder  110  in a height direction and may protrude from the cell holder  110  toward the outside at a height between the upper and lower surfaces of the cell holder  110 . In an implementation, the exhaust pipe DP may protrude from an outer surface of the cell holder  110  to the outside in a long side direction of the cell holder  110 . In an implementation, the exhaust pipe DP may be at a height between the upper surface of the upper holder  110   a  and the lower surface of the lower holder  110   b  and may be in one of the upper holder  110   a  and the lower holder  110   b  and may be formed between the upper surface of the upper holder ( 110   a ) and the lower surface of the lower holder ( 110   b ) at a height close to either the upper surface of the upper holder  110   a  or the lower surface of the lower holder  110   b . In an implementation, the exhaust pipe DP may protrude outwardly from the upper holder  110   a  and may be at a height or position relatively close to (e.g., proximate to) the upper surface of the upper holder  110   a , at a height between the upper surface of the upper holder  110   a  and the lower surface of the lower holder  110   b . As illustrated in  FIG. 1 , in one embodiment, the circuit board  130  may be on the upper holder  110   a , and the circuit board  130  may be between the upper surface of the upper holder  110   a  formed with the exhaust path and the upper separation member  140   a  to form of flow resistance on the exhaust path, and the exhaust pipe DP may be at a height biased or proximate to the upper surface of the upper holder  110   a  (among the upper surface of the upper holder  110   a  and the lower surface of the lower holder  110   b ) to form a balanced flow resistance between the exhaust path in the upper holder  110   a  and the exhaust path in the lower holder  110   b . As illustrated in  FIG. 1 , with respect to the circuit board  130  on the upper holder  110   a , the upper exhaust hole DHa on the upper surface of the upper holder  110   a  may be at a position out of the circuit board  130  so that a flow of exhaust gas introduced into the upper exhaust hole DHa may not be disturbed by the circuit board  130 . The circuit board  130  may be on the upper holder  110   a  and may be formed locally over a partial area of the upper holder  110   a  without being formed over the entire area of the upper holder  110   a , and thereby, the upper exhaust hole DHa may be prevented from being blocked by the circuit board  130  by forming the upper exhaust hole DHa on the upper holder  110   a  exposed from the circuit board  130 . 
     Referring to  FIG. 8 , the exhaust pipe DP may form an end of the exhaust path through which exhaust gas emitted from the first and second groups of battery cells  10  accommodated in the cell holder  110  is emitted to the outside of the cell holder  110 . In an implementation, the upper exhaust hole DHa, the lower exhaust hole DHb, and the exhaust duct DD may have different configurations, and this is for the sake of easy understanding, and both ends of the exhaust duct DD continuously extending through the upper holder  110   a  and the lower holder  110   b  in a height direction may form the upper exhaust hole DHa and the lower exhaust hole DHb, and the upper exhaust hole DHa, the lower exhaust hole DHb, and the exhaust duct DD may be formed together as one tubular shape continuously extending in the height direction. 
     Referring to  FIG. 7 , the hollow protrusion portion  115  for forming the cooling flow path F may be formed in the cell holder  110 . The hollow protrusion portion  115  may include a central hollow portion forming the cooling flow path F, and a wall body  115   a  surrounding the central hollow portion (e.g., may be a hollow cylinder). In an implementation, the hollow protrusion portion  115  may include a circular wall body  115   a  surrounding the central hollow portion. In an implementation, the circular wall body  115   a  of the hollow protrusion portion  115  may indicate a shape of an outer surface forming an outer circumference of the hollow protrusion portion  115 , and a shape of an inner surface of the hollow protrusion portion  115  may be formed in a shape different from a circular shape. In an implementation, the circular wall body  115   a  of the hollow protrusion portion  115  may have a circular outer surface and a triangular inner surface having rounded corners. In an implementation, the hollow protrusion portions  115  may have the wall body  115   a  of one of various shapes including an oval shape or a polygonal shape, e.g., hexagonal shape, surrounding the central hollow portion and may have the inner shape of one of various shapes such as a circular shape, an elliptical shape, a polygonal shape, and a combination thereof together with the outer surface of an oval shape or one of various polygonal shapes. 
     The hollow protrusion portion  115  may protrude from the plate-shaped body of the cell holder  110  in a height direction opposite to or away from the battery cell  10 . In an implementation, the hollow protrusion portion  115  may extend the cooling flow path F formed between the adjacent battery cells  10  to the outside of the battery cell  10  in a height direction of the battery cell  10 , and may form the cooling flow path F surrounded by the wall body  115   a  (e.g., the hollow protrusion portion  115  may be vertically aligned with spaces between battery cells  10 ). In an implementation, a position at which the hollow protrusion portion  115  is formed along the body of the cell holder  110  may correspond to a position of the cooling flow path F between the battery cells  10 , and the position at which the hollow protrusion portion  115  is formed may correspond to the position of the cooling flow path F described with reference to  FIG. 4 , and the position of the cooling flow path F in  FIG. 4  may indicate the hollow protrusion portion  115 . 
     Referring to  FIG. 1 , the hollow protrusion portion  115  may sequentially penetrate through the circuit board  130  and the separation member  140  on the cell holder  110  in the height direction of the battery cell  10 , and in this case, the hollow protrusion portion  115  may form the cooling flow path F extending across a battery pack so as to penetrate almost the entire battery pack in the height direction of the battery cell  10 . In an implementation, the hollow protrusion portion  115  of the upper holder  110   a  may sequentially penetrate the circuit board  130  and the upper separation member  140   a  on the upper holder  110   a  in the height direction of the battery cell  10 , and the hollow protrusion portion  115  of the lower holder  110   b  may penetrate the lower separation member  140   b  arranged on the lower holder  110   b  in the height direction of the battery cell  10 . Opening regions  135  and  145  (to allow the hollow protrusion portion  115  to be fitted thereto) may be in the circuit board  130  and in the separation member  140 . The opening regions  135  and  145  of the circuit board  130  and the separation member  140  may be formed in a shape in which a position corresponding to the hollow protrusion portion  115  is opened along the circuit board  130  and the separation member  140 . The opening regions  135  and  145  of the circuit board  130  and the separation member  140  will be described below in greater detail. 
     Referring to  FIGS. 1 and 2 , the bus bar  120  may be on the cell holder  110 . In an implementation, the upper bus bar  120   a  and the lower bus bar  120   b  may be respectively arranged on the upper holder  110   a  and the lower holder  110   b , and the bus bars  120  may be alternately arranged at alternate positions on the upper holder  110   a  and the lower holder  110   b  and may connect the adjacent battery cells  10  in an electrical connection direction. As described above, each of the bus bars  120  may electrically connect a pair of the battery cells  10  in the electrical connection direction, and the multiple bus bars  120  may be arranged in the electrical connection direction of the battery cells  10  to electrically connect a group of the battery cells  10 . 
     Referring to  FIG. 9 , the bus bar  120  may include coupling pieces  120   a  at both ends, a central protrusion connection piece  120   c  coupling the coupling pieces  120   a  to each other, and bent portions  120   b  coupling the coupling pieces  120   a  at both ends to the central protrusion connection piece  120   c  in a bent shape. The coupling pieces  120   a  at both ends of the bus bar  120  may be connected to the upper end portion  10   a  of the adjacent battery cell  10  or the lower end portion  10   b  of the adjacent battery cell  10 , and may be connected to the upper end portion  10   a  or the lower end portion  10   b  of the adjacent battery cell  10  exposed through the terminal hole  112  of the cell holder  110  to connect the first and second electrodes  11  and  12  of the adjacent battery cell  10  to each other in series or in parallel. In an implementation, the coupling pieces  120   a  at both ends of the bus bar  120  and the adjacent battery cells  10  may be welded together. 
     The bent portions  120   b  connect the coupling pieces  120   a  at both ends to the central protrusion connection piece  120   c  in a bent shape, and by supporting the protrusion connection piece  120   c  at a level spaced apart from the battery cell  10  from the connection pieces  120   a  at both ends in the height direction of the battery cell  10 , electrical interference between the protrusion connection piece  120   c  and the battery cell  10  may be blocked, and the connection pieces  120   a  at both ends may be pressed toward the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  while being elastically deformed according to the protrusion connection piece  120   c  pressed toward the battery cell  10  by the cell holder  110  (e.g., the hollow protrusion portion  115 ). This will be described below in greater detail. 
     The protrusion connection piece  120   c  may correspond to a flat plate-shaped member spaced farthest from the battery cell  10  among the bus bars  120  in the height direction of the battery cell  10 , and may be arranged on a virtual plane located farthest from the battery cell  10  among the bus bars  120 . As illustrated in  FIG. 10 , the protrusion connection piece  120   c  may be exposed from the circuit board  130  arranged on the cell holder  110 , and the whole of the protrusion connection piece  120   c  may be exposed from the circuit board  130  (a solid portion of the circuit board  130 ) through an escape hole  132   a  of the circuit board  130 . 
     Referring to  FIG. 9 , the bus bar  120  may extend across a space between the hollow protrusion portions  115  of the cell holder  110 . In an implementation, the bus bar  120  may extend across a space between a pair of the hollow protrusion portions  115 , and the protrusion connection piece  120   c  of the bus bar  120  may be placed between the pair of hollow protrusion portions  115 . An extension direction of the bus bar  120  and a direction in which the pair of hollow protrusion portions  115  face each other may cross each other, for example, may cross vertically. 
     In an implementation, the bus bar  120  may electrically connect a pair of adjacent battery cells  10  while extending across the pair of battery cells  10  of which outer circumferences are adjacent, and in this case, the cooling flow path F or the hollow protrusion portion  115  may be between the pair of battery cells  10  connected by the bus bar  120  and the other pair of battery cells  10  facing each other in a direction crossing the bus bar  120 . Accordingly, the bus bar  120  may extend across a pair of the hollow protrusion portions  115  facing each other in a direction crossing the bus bar  120 . 
     A pair of hollow protrusion portions  115  facing each other and having the bus bar  120  therebetween, e.g., a pair of locking protrusions  115   p  for fitting and assembling the bus bar  120  thereto may be in the wall bodies  115   a , which face each other, of the pair of hollow protrusions  115 . In an implementation, the locking protrusion  115   p  may be on the wall body  115   a  of the hollow protrusion portion  115 , and the bus bar  120 , e.g., the protrusion connection piece  120   c  of the bus bar  120  may be fitted and assembled to the locking protrusion  115   p  of a wedge shape. The bus bar  120  fitted and assembled to the locking protrusion  115   p  may be effectively prevented from being separated from the battery cell  10  in a distant direction. A pair of the locking protrusions  115   p  may be on the pair of hollow protrusion portions  115  facing each other with the bus bar  120  therebetween, and the pair of locking protrusions  115   p  may extend from the wall body  115   a  of the hollow protrusion portion  115  onto the protrusion connection piece  120   c  of the bus bar  120  to press the protrusion connection piece  120   c  toward the battery cell  10 , and the coupling pieces  120   a  at both ends of the bus bar  120  may be pressed toward the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  due to elastic deformation of the bent portion  120   b  connected to the protrusion coupling piece  120   c , and thus, the bus bar  120  may be firmly bonded to the battery cells  10 . 
     Referring to  FIG. 9 , a mold hole  110 ′ may be in the cell holder  110  corresponding to the pair of locking protrusions  115   p . In an implementation, the hollow protrusion portion  115  having the locking protrusion  115   p  protrudes from a main body of the cell holder  110  formed in a plate shape, and the mold hole  110 ′ may be formed in the main body of the cell holder  110  corresponding to the locking protrusion  115   p  to penetrate the main body of the cell holder  110 . The mold hole  110 ′ may be formed at a coupling position between an upper mold and a lower mold when the cell holder  110  having the locking protrusion  115   p  is formed, and a portion that is not filled with a molten resin by a coupling hole between the upper mold and the lower mold may remain in the form of the mold hole  110 ′. In an implementation, the cell holder  110  having the locking protrusion  115   p  therein may be easily demolded from a mold through a mold having a shape in which the upper mold is combined with the lower mold, and it is possible to prevent a shape of the locking protrusion  115   p  of the cell holder  110  from being damaged in while being demolded. 
     Referring to  FIG. 9 , a position alignment hole  120   g  for aligning a position of the cell holder  110  may be in the protrusion connection piece  120   c  of the bus bar  120 . A position alignment pin  110   g  for being fitted to the position alignment hole  120   g  of the protrusion connection piece  120   c  may be between a pair of the hollow protrusion portions  115  having the protrusion connection piece  120   c  including the position alignment hole  120   g  therebetween, e.g., on a main body of the cell holder  110  in which the pair of hollow protrusion portions  115  are formed. In this case, while the position alignment hole  120   g  of the protrusion connection piece  120   c  is fitted to the position alignment pin  110   g  of the cell holder  110 , the bus bar  120  may be assembled to a correct position on the cell holder. The position alignment pin  110   g  may include a pair of position alignment pins  110   g  arranged in an extension direction of the bus bar  120 . In this case, the extension direction of the bus bar  120  in which the paired position alignment pins  110   g  are arranged may cross a direction in which the pair of hollow protrusion portions  115  having the bus bar  120  therebetween face each other, e.g., may cross vertically. In an implementation, the position alignment hole  120   g  and the position alignment pin  110   g  may be respectively on the bus bar  120  and the cell holder  110  to which the bus bars  120  are assembled, and in another embodiment, the position alignment hole  120   g  and the position alignment pin  110   g  may also be respectively on the cell holder  110  and the bus bar  120 , and may be selectively on any one side and the other side of the cell holder  110  and the bus bar  120  in a range in which the position alignment hole  120   g  and the position alignment pin  110   g  are formed at corresponding positions. 
     Referring to  FIGS. 10 and 11 , the coupling pieces  120   a  at both ends of the bus bar  120  may be exposed from the circuit board  130  arranged on the bus bar  120 , and more specifically, may be exposed from the circuit board  130  (a solid portion of the circuit board  130 ) through a filling hole FH of the circuit board  130 . In an implementation, the filling hole FH may expose at least some of the coupling piece  120   a  of the bus bar  120 . In addition, as the coupling piece  120   a  of the bus bar  120  connected to the upper end portion  10   a  of the battery cell  10  is exposed through the filling hole FH of the circuit board  130 , a potting resin PR filling the filling hole FH may cover and protect a coupling portion between the upper end portion  10   a  of the battery cell  10  and the coupling piece  120   a  of the bus bar  120 . In an implementation, the potting resin PR may protect the coupling portion between the battery cell  10  and the coupling piece  120   a  of the bus bar  120  from harmful components such as oxygen or moisture and may protect, e.g., a coupling portion between heterogeneous materials formed by welding from galvanic corrosion. In an implementation, the filling hole FH may be at a central position of the upper end portion  10   a  of each of the battery cells  10  to expose the bus bar  120  (e.g., the coupling pieces  120   a  at both ends of the bus bar  120 ) connected to a central position of the upper end portion  10   a  of each battery cell  10 . 
     Referring to  FIGS. 10 and 12 , the circuit board  130  may be arranged on the bus bar  120 . The escape hole  132   a  for exposing some of the bus bar  120  may be formed in the circuit board  130 . More specifically, the escape hole  132   a  may expose the entire protrusion connection piece  120   c  at the center of the bus bar  120 . Here, that the escape hole  132   a  exposes the entire protrusion connection piece  120   c  may indicate that all of the protrusion connection piece  120   c  is completely exposed from the circuit board  130  through the escape hole  132   a . In an implementation, the protrusion connection piece  120   c  may not overlap the circuit board  130  (a solid portion of the circuit board  130 ), and even some thereof may not overlap the circuit board  130  (a solid portion of the circuit board  130 ). 
     Referring to  FIG. 12 , the escape hole  132   a  may accommodate the protrusion connection piece  120   c , and the protrusion connection piece  120   c  may be at a height between the lower surface  130   a  and the upper surface  130   b  of the circuit board  130  in a height direction. Here, the lower surface  130   a  and the upper surface  130   b  of the circuit board  130  may indicate respectively a surface facing the battery cell  10  and a surface opposite to the battery cell  10  among both surfaces of the circuit board  130 . In an implementation, the coupling pieces  120   a  at both ends of the bus bar  120  may overlap the lower surface  130   a  of the circuit board  130  (a solid portion of the circuit board  130 ), but the protrusion connection piece  120   c  connected through the bent portion  120   b  from the coupling pieces  120   a  does not overlap the lower surface  130   a  of the circuit board  130  (a solid portion of the circuit board  130 ) and is accommodated in the escape hole  132   a  at a height between the upper surface  130   b  and the upper surface  130   b  of the circuit board  130  in a height direction so as not to for an additional thickness for the thickness of the circuit board  130  in the height direction. 
     The protrusion connection piece  120   c  of the bus bar  120  and the circuit board  130  (a solid portion of the circuit board  130 ) may be arranged so as not to overlap each other through the escape hole  132   a , and thereby, the circuit board  130  may be arranged at a position close to the battery cell  10 , e.g., a low height close to the battery cell  10 , and by reducing an interval q between the circuit board  130  and the battery cell  10  in the height direction, a length of a coupling member  125  forming a voltage measurement line between the circuit board  130  and the battery cell  10  may be reduced, and for example, when coupling one end portion and the other end portion of the coupling member  125  to each of the circuit board  130  and the battery cell  10 , wire bonding or ribbon bonding is performed by using ultrasonic welding for solid bonding, and it is possible to prevent the ultrasonic welding from failing due to relative shaking between the circuit board  130  and the battery cell  10  during the ultrasonic welding. 
     In addition, by arranging the protrusion connection piece  120   c  of the bus bar  120  and the circuit board  130  (a solid portion of the circuit board  130 ) in a height direction through the escape hole  132   a  so as not to overlap each other, the circuit board  130  may be arranged at a low height close to the battery cell  10 , and by reducing a height of the entire battery pack, a battery pack advantageous for slimming may be provided. 
     Referring to  FIG. 10 , the bus bar  120  may extend across a pair of hollow protrusion portions  115 , and the protrusion connection piece  120   c  of the bus bar  120  may be arranged between the pair of hollow protrusion portions  115 . In this case, the escape hole  132   a  may be formed at a position corresponding to the protrusion connection piece  120   c  on the circuit board  130 , that is, a position between the pair of hollow protrusion portions  115 . The escape hole  132   a  may be formed as some of a bus opening region  132   b  that exposes a pair of hollow protrusion portions  115  formed at positions facing each other with the bus bar  120  therebetween or the cooling flow path F together with the protrusion connection piece  120   c  of the bus bar  120 . In an implementation, the circuit board  130  may have the bus opening region  132   b  exposing the hollow protrusion portion  115  together with the protrusion connection piece  120   c  of the bus bar  120  and may be formed in a single hole form by being connected to the escape hole  132   a  for exposing the protrusion connection piece  120   c  of the bus bar  120 . 
     The bus opening region  132   b  may be in a single hole form formed in the circuit board  130  to expose some of the bus bar  120 , e.g., the protrusion connection piece  120   c  of the bus bar  120  together with a pair of hollow protrusion portions  115  (or a pair of cooling flow paths F) facing each other with the bus bar  120  therebetween. In this case, the escape hole  132   a  that entirely exposes the protrusion connection piece  120   c  of the bus bar  120  may indicate a region excluding a region through which the hollow protrusion portion  115  passes in the bus opening region  132   b  formed in a single hole form. 
     If one hole for exposing the protrusion connection piece  120   c  of the bus bar  120  and two holes for exposing respectively the adjacent cooling flow paths F were to be separately formed with a narrow interval therebetween, e.g., if three holes were to be individually formed with narrow intervals therebetween, there is a possibility of damage to the circuit board  130 . In an implementation, the protrusion connection piece  120   c  of the bus bar  120  and a pair of adjacent cooling flow paths F may be exposed together through the bus opening region  132   b  formed in a single hole form, and thereby, a structure of the circuit board  130  may be simplified and a possibility of breakage due to insufficient rigidity of the circuit board  130  may be reduced. 
     The bus opening region  132   b  may expose a pair of cooling flow paths F (or the hollow protrusion portions  115 ) facing each other with the bus bar  120  therebetween. As will be described below, the bus opening region  132   b  may be in a single hole form together with a coupling opening region  132   c  that exposes a pair of cooling flow paths F (or the hollow protrusion portions  115 ) facing each other with the coupling member  125  therebetween, and the bus opening region  132   b  and the coupling opening region  132   c  may form a second opening region  132  formed in a single hole form. In an implementation, the cooling flow paths F exposed through the second opening region  132  (or the hollow protrusion portion  115 ) may include a pair of cooling flow paths F (or first and second hollow protrusion portions  1151  and  1152 ) facing each other with the bus bar  120  therebetween and a pair of cooling flow paths F (or first and third hollow protrusions  1151  and  1153 ) facing each other with the coupling member  125  therebetween, and share the cooling flow paths F (or the first hollow protrusion portion  1151 ) between the bus bar  120  and the coupling member  125 , and include three different cooling flow paths F as a whole. In an implementation, the hollow protrusion portion  115  exposed through the second opening region  132  may include the first hollow protrusion portion  1151  between the bus bar  120  and the coupling member  125 , the second hollow protrusion portion  1152  facing the first hollow protrusion portion  1151  with the bus bar  120  therebetween, and the third hollow protrusion portion  1151  facing the first hollow protrusion with the coupling member  125  therebetween, e.g., may include three hollow protrusion portions  115  as a whole. 
     In an implementation, the escape hole  132   a  exposing the protrusion connection piece  120   c  of the bus bar  120  may be formed as some of the second opening region  132 , and the protrusion connection piece  120   c  of the bus bar  120  may be exposed through the second opening region  132 , and the entire protrusion connection piece  120   c  may be completely exposed from the circuit board  130  (a solid portion of the circuit board  130 ) through the second opening region  132 . 
     Referring to  FIG. 10 , an opening region  135  opened in a hole form may be formed in the circuit board  130  to allow the cooling flow path F (or the hollow protrusion portion  115 ) to pass therethrough. The cooling flow path F may penetrate the opening region  135  of the circuit board  130  and extend across the circuit board  130 , and for example, the cooling flow path F may penetrate the opening region  135  of the circuit board  130  while the hollow protrusion portion  115  of the cell holder  110  is fitted to the opening region  135  of the circuit board  130 . To this end, the opening region  135  of the circuit board  130  may be at a position corresponding to the hollow protrusion portion  115  of the cell holder  110 , and may be formed in a form corresponding to the hollow protrusion portion  115  of the cell holder  110 . In an implementation, the opening region  135  (e.g., the first opening region  131 ) of the circuit board  130  may be formed in a circular shape corresponding to the hollow protrusion portion  115  including the circular wall body  115   a . In an implementation, the opening region  135  (e.g., the first opening region  131 ) of the circuit board  130  may be formed in various shapes corresponding to the hollow protrusion portions  115 , e.g., various shapes including ovals or polygonal shapes, e.g., hexagons. 
     As will be described below, among the opening regions  135 , the first opening region  131  may surround an outer circumference of the hollow protrusion portion  115 , and the second opening region  132  may surround at least some of the outer circumference of the hollow protrusion portion  115 . In an implementation, the second opening region  132  may expose two or more different adjacent hollow protrusion portions  115 , and the second opening region  132  may surround at least some of outer circumferences of the different hollow protrusion portions  115  so that two or more different hollow protrusion portions  115  are surrounded together. 
     The opening region  135  of the circuit board  130  may include first opening regions  131  individually formed for the respective cooling flow paths F (or the hollow protrusion portion  115 ), and second opening regions  132  formed in common for two or more adjacent cooling flow paths F. In an implementation, each of the second opening regions  132  may include a coupling opening region  132   c  and a bus opening region  132   b . The coupling opening region  132   c  may be formed in common for a pair of cooling flow paths F facing each other with the coupling member  125  therebetween. Detailed technical matters relating to the coupling member  125  will be described below. The bus opening region  132   b  may be formed in common for a pair of cooling flow paths F facing each other with the bus bar  120  therebetween. In an implementation, the coupling opening region  132   c  and the bus opening region  132   b  may not be formed in the form of independent holes separated from each other, but may be connected to each other to form the second opening region  132  in the form of a single hole. A pair of cooling flow paths F exposed through the coupling opening region  132   c  and a pair of cooling flow paths F exposed through the bus opening region  132   b  may not include four different cooling flow paths F as a whole and may include three different cooling flow paths F as a whole by sharing one cooling flow path F. In an implementation, the cooling flow path F at a position where the coupling opening region  132   c  and the bus opening region  132   b  meet each other, e.g., the cooling flow path F (or the first hollow protrusion portion  115 ) between the coupling member  125  and the bus bar  120  may be shared in a pair of cooling flow paths F (or the first and second hollow protrusion portions  1151  and  1152 ) exposed through the bus opening region  132   b , and a pair of cooling flow paths F (or the first and third hollow protrusion portions  1151  and  1153 ) exposed through a coupling opening region  132   c . In other words, the cooling flow path F or the hollow protrusion portion  115  exposed through the second opening region  132  may include the first hollow protrusion portion  1151  between the bus bar  120  and the coupling member  125 , the second hollow protrusion portion  1152  facing the first hollow protrusion portion  1151  with the bus bar  120  therebetween, and the third hollow protrusion portion  1153  facing the first hollow protrusion portion  1151  with the coupling member  125  therebetween, e.g., may include three hollow protrusion portions  115  as a whole. 
     The first opening region  131  may be formed individually for each cooling flow path F, and may be provided in the form of a hole individually formed for each cooling flow path F to expose each cooling flow path F from the circuit board  130 . Unlike the first opening region  131 , the second opening region  132  may be provided in the form of a single hole formed in common for two or more adjacent cooling flow paths F to expose two or more adjacent cooling flow paths F together, and may expose two or more adjacent cooling flow paths F together from the circuit board  130 . 
     In the second opening region  132 , the coupling opening region  132   c  may expose some of the upper end portion  10   a  of the battery cell  10  together with a pair of adjacent cooling flow paths F (a pair of cooling flow paths F facing each other with the coupling member  125  therebetween), and in this case, the coupling member  125  may be connected to the upper end portion  10   a  of the battery cell  10  exposed through the coupling opening region  132   c . In an implementation, the coupling opening region  132   c  may expose some of the upper end portion  10   a  of the battery cell  10  together with a pair of adjacent cooling flow paths F. As the coupling opening region  132   c  exposes some of the upper end portion  10   a  of the battery cell  10 , one end portion of the coupling member  125  may be connected to the upper end portion  10   a  of the battery cell  10  exposed from the circuit board  130  through the coupling opening region  132   c , and as the other end portion of the coupling member  125  is connected to the circuit board  130 , a voltage measurement line may be formed between the battery cell  10  and the circuit board  130 , and the coupling opening region  132   c  may provide the coupling hole CH for allowing coupling of the coupling member  125  through the circuit board  130 . The technical matters relating to the coupling hole CH will be described below in greater detail. 
     Referring to  FIG. 10 , in one embodiment, the coupling opening region  132   c  exposes some of the upper end portion  10   a  of the battery cell  10  together with a pair of adjacent cooling flow paths F (a pair of cooling flow paths F facing each other with the coupling member  125  interposed therebetween), thereby, functioning as the coupling hole CH, and thus, in one embodiment, the coupling opening region  132   c  and coupling hole CH may indicate substantially the same configuration, e.g., the same hole formed in the circuit board  130 . However, in the present specification, separate reference numerals are assigned to the coupling opening region  132   c  and the coupling hole CH for the sake of easy understanding. 
     Some of the upper end portion  10   a  of the battery cell  10  may be exposed through the coupling hole CH (or the coupling opening region  132   c ), and the coupling member  125  may be coupled to the upper end portion  10   a  of the battery cell  10  exposed from the circuit board  130 . For example, the coupling member  125  may include a conductive wire or a conductive ribbon including one end portion connected to the upper end portion  10   a  of the battery cell  10  and the other end portion connected to the circuit board  130 , and one end portion and the other end portion of the conductive wire may be bonded respectively to the upper end portion  10   a  of the battery cell  10  and the circuit board  130  by wire bonding, or one end portion and the other end portion of the conductive ribbon may be bonded respectively to the upper end portion  10   a  of the battery cell  10  and the circuit board  130  by ribbon bonding. In this case, a conductive wire or a conductive ribbon may be bonded to the upper end portion  10   a  of the battery cell  10  and the circuit board  130  by ultrasonic welding. 
     In an implementation, a conductive wire as the coupling member  125  may include a pair of conductive wires extending in parallel to connect the battery cell  10  to the circuit board  130 , and each of the battery cells  10  and the circuit board  130  may be firmly connected through a pair of conductive wires in a case in which the conductive wire is disconnected due to an insufficient mechanical strength. The conductive ribbon has a higher mechanical strength than the conductive wire, and thus, it is not necessary to provide a pair for disconnection, and the battery cell  10  and the circuit board  130  may electrically connected to each other by a single conductive ribbon. For reference, the coupling member  125  exemplarily illustrated in  FIG. 10  may correspond to a conductive ribbon. 
     The coupling hole CH may be in a region of the circuit board  130  overlapping a pair of adjacent battery cells  10  to expose the upper end portions  10   a  of the pair of adjacent battery cells  10  together. In an implementation, the coupling hole CH may be in a region of the circuit board  130  overlapping some of the pair of adjacent battery cells  10 , e.g., in a region overlapping a rim of the pair of battery cells  10 . In addition, different coupling members  125  may be connected to each of the rims of the adjacent battery cells  10  exposed through the coupling hole CH. 
     The rims of the upper end portions  10   a  of the pair of battery cells  10  exposed through the coupling hole CH may form the first electrodes  11  having the same polarity. In an implementation, the adjacent battery cells  10  exposed through the same coupling hole CH may be arranged in a vertically inverted pattern in the height direction of the battery cells  10 , and rims of the upper end portions  10   a  of the battery cells  10  may form the first electrodes  11  having the same polarity, regardless of a vertical arrangement of the battery cells  10 . As can be seen in  FIG. 3 , the can N forming the first electrode  11  extends from the rim of the upper end portion  10   a  to the entire lower end portion  10   b , and thereby, the rim of the upper end portion  10   a  of the battery cell  10  or the rim of the lower end portion  10   b  of the battery cell  10  may form the first electrode  11  having the same polarity. 
     As such, the coupling member  125  may be connected to the rim of the upper end portion  10   a  of the battery cell  10  exposed through the coupling hole CH and may be connected to the first electrode  11  of the battery cell  10 . Referring to  FIG. 2 , most of the multiple coupling members  125  may be connected to the first electrodes  11  of the battery cells  10  exposed through the coupling holes CH, and some of the coupling members  125  may be connected to the first and second output terminals  121  and  122  or the battery cells  10  connected to the first and second output terminals  121  and  122  and may be connected to the second electrodes  12  of the battery cells  10 . In an implementation, the first and second output terminals  121  and  122  may be connected respectively to the low-potential battery cell  10  having the lowest potential and the high-potential battery cell  10  having the highest potential among a group of battery cells  10  electrically connected to each other. In this case, one coupling member  125   a  may be connected to the first electrode  11  formed on the upper end portion  10   a  of the low-potential battery cell  10 , and the other coupling member  125   b  may be connected to the second electrode  12  formed on the upper end portion  10   a  of the high-potential battery cell  10 . In an implementation, in a group of coupling members  125  forming a battery pack, one coupling member  125   a  may be connected to the first electrode  11  of the low-potential battery cell  10  connected to the first output terminal  121 , and the other coupling member  125   b  may be connected to the second electrode  12  of the high-potential battery cell  10  connected to the second output terminal  122 , and the coupling member  125  may be connected to the first electrode  11  in a rim of the upper end portion  10   a  of the battery cell  10  having an intermediate potential other than the high-potential battery cell  10  and the low-potential battery cell  10 . In an implementation, the coupling member  125  may be connected to the second electrode  12  of only the high-potential battery cell  10  connected to the second output terminal  122 , and may be connected to the first electrode  11  of the other battery cells  10 . 
     Referring to  FIG. 10 , the coupling opening region  132   c  (or the coupling hole CH) may be formed with a sufficient area to expose a pair of the adjacent cooling flow paths F (a pair of the cooling flow paths F facing each other with the coupling member  125  therebetween) together with rims of the pair of adjacent battery cells  10 . In an implementation, a direction in which a pair of battery cells  10  exposed through the coupling opening region  132   c  face each other may cross a direction in which a pair of the cooling flow paths F (a pair of the cooling flow paths F facing each other with the coupling member  125  therebetween) exposed through the coupling opening region  132   c , and for example, may cross vertically. 
     If one coupling hole CH for exposing a rim of a pair of the adjacent battery cells  10  and two opening regions  135  for exposing the adjacent cooling flow paths F were to be formed separately from each other with a narrow gap, e.g., if the three holes were to be individually formed with a narrow gap, there is a possibility of damage to the circuit board  130 . In an implementation, a pair of the cooling flow paths F adjacent to a rim of a pair of the adjacent battery cells  10  through the coupling hole CH formed in a single hole form or the coupling opening region  132   c  are exposed together, and thereby, a structure of the circuit board  130  may be simplified and a possibility of damage due to insufficient rigidity of the circuit board  130  may be reduced. 
     The coupling member  125  for electrically connecting the upper end portion  10   a  of the battery cell  10  to the circuit board  130  may be between the upper end portion  10   a  of the battery cell  10  exposed through the coupling opening region  132   c  or the coupling hole CH and the circuit board  130 , and the coupling member  125  may transmit voltage information of the battery cell  10  to the circuit board  130 . In an implementation, the coupling members  125  may electrically connect the upper end portions  10   a  of the battery cells  10  to connection pads  133  of the circuit board  130 . The connection pads  133  of the circuit board  130  may be formed around the coupling holes CH, and for example, a pair of connection pads  133  electrically connected to a pair of adjacent battery cells may be formed at positions facing each other around the coupling hole CH. 
     In an implementation, the coupling opening region  132   c , a second opening region  132  may be formed together with the bus opening region  132   b  that exposes together a pair of the cooling flow paths F facing each other with the bus bar  120  interposed therebetween. In this case, the second opening region  132  may be formed in a single hole form and may extend in an outer circumferential direction surrounding the filling hole FH. The second opening region  132  may expose three different cooling flow paths F which include one cooling flow path F (or first hollow protrusion portion  1151 ) interposed between the bus bar  120  and the coupling member  125 , another cooling flow path F (or the second hollow protrusion portion  1152 ) with the cooling flow path F (or the first hollow protrusion portion  1151 ) and the bus bar  120  interposed therebetween, and another cooling flow path F (or the third hollow protrusion portion  1153 ) with the cooling flow path F (or the first hollow protrusion portion  1151 ) and the coupling member  125  interposed therebetween, and which are successively arranged in an outer circumferential direction surrounding the filling hole FH as a whole. For example, as illustrated in  FIG. 4 , six cooling flow paths F may be formed in an outer circumferential direction of one battery cell  10 , and among the six cooling flow paths F, three adjacent cooling flow paths F may be exposed together through the second opening region  132 . 
     Referring to  FIG. 10 , the second opening region  132  may expose three different hollow protrusion portions  115  which include the first hollow protrusion portion  1151  interposed between the bus bar  120  and the coupling member  125 , the second hollow protrusion portion  1152  facing the first hollow protrusion portion  1151  with the bus bar  120  interposed therebetween, and the third hollow protrusion portion  1153  facing the first hollow protrusion portion  1151  with the coupling member  125  interposed therebetween, and which are consecutively arranged in an outer circumferential direction surrounding the filling hole FH as a whole. 
     Referring to  FIG. 10 , a thermistor TH for measuring a temperature of the battery cell  10  may be arranged at the upper end portion  10   a  of the battery cell  10 . For example, the thermistor TH may be arranged on a rim of the battery cell  10 . More specifically, the thermistor TH may be arranged in a different place of a rim of the battery cell  10  spaced apart from a location of a rim of the battery cell  10  to which the coupling member  125  is connected, in an outer circumferential direction of the battery cell  10 . That is, the coupling member  125  and the thermistor TH may be arranged at locations spaced apart from each other along the rim of the battery cell  10  to avoid interference with each other. For example, the thermistor TH may be provided as a chip-type thermistor TH that may be directly bonded to the rim of the battery cell  10 . In addition, the thermistor TH may be bonded to the rim of the battery cell  10  by solder mounting. 
     A long hole extending in an outer circumferential direction of the battery cell  10  may be formed in the cell holder  110  to which the battery cell  10  is assembled to expose a rim of the battery cell  10 , and the rim of the battery cell  10  may be exposed long through the long hole formed in the cell holder  110 , and the coupling member  125  and the thermistor TH may be arranged at locations spaced apart from each other. As illustrated in  FIG. 11 , an adhesive resin AR may be formed on the coupling member  125  bonded to the rim of the battery cell  10 , and the adhesive resin AR may not extend to the thermistor TH, and the adhesive resin AR may not be formed on the thermistor TH. 
     Referring to  FIG. 13 , the coupling hole CH may be formed in an alternating pattern in a column direction (for example, L 1  and L 2 ) of the battery cell  10  or the filling hole FH to expose a pair of the adjacent battery cells  10  in the column direction (for example, L 1  and L 2 ) of the battery cell  10  or the filling hole FH. In an implementation, the first and second opening regions  131  and  132  for exposing the cooling flow paths F may be formed in the circuit board  130 , and the coupling opening region  132   c  (or the second opening region  132 ) that functions as the coupling hole CH and the first opening region  131  that does not function as the coupling hole CH may be arranged in an alternating pattern in the column direction (for example, L 1  and L 2 ) of the battery cell  10  (or the filling hole FH). In an implementation, the coupling opening region  132   c  (or the second opening region  132 ) functioning as the coupling hole CH may be formed one by one between the two battery cells  10  (or filling hole FH) forming a pair in the column direction (for example, L 1  and L 2 ) of the battery cell  10  (or the filling hole FH, and the coupling opening region  132   c  (or the second opening region  132 ) functioning as the coupling hole CH may not be formed between the adjacent battery cells  10  (or the filling hole FH) that do not form a pair. In an implementation, the coupling opening region  132   c  (or the second opening region  132 ) may not be formed between the adjacent battery cells  10  in the column direction (for example, L 1  and L 2 ) of the battery cell  10  (or the filling hole FH), and may be formed at alternating positions in the column direction (for example, L 1  and L 2 ) of the battery cells  10  (or the filling holes FH) among the adjacent battery cells  10  (or the filling holes FH). In this case, the first opening region  131  for exposing the cooling flow path F penetrating a space between the adjacent battery cells  10  may be formed at a position P where the coupling opening region  132  (or the second opening region  132 ) is not formed, or at a position adjacent thereto among a space between the adjacent battery cells  10  or a space between the adjacent filling holes FH. 
     As will be described below, the filling hole FH may be formed at a central position of the upper end portion  10   a  of the battery cell  10 , and accordingly, arranging the first and second opening regions  131  and  132  between the adjacent battery cells  10  in an alternating pattern in the column direction Z 1  of the cell  10  may include arranging the first and second opening regions  131  and  132  between the adjacent filling holes FH in an alternating pattern in the column direction (for example, L 1  and L 2 ) of the filling hole FH, and arranging the first and second opening regions  131  and  132  at a position P between the adjacent filling holes FH in an alternating pattern and at a position adjacent to the position P. In an implementation, the first opening region  131  may be formed at a position adjacent to the position P between the adjacent filling holes FH rather than a position between the adjacent filling holes FH in the column direction (for example, L 1  and L 2 ) of the filling hole FH, and in this case, the first opening region  131  may still be arranged between the adjacent battery cells  10 . This is because the filling hole FH is formed at a central position of the adjacent battery cells  10 . 
     As described with reference to  FIG. 4 , six cooling flow paths F may be formed in an outer circumferential direction of or surround one battery cell  10 . In this case, four cooling flow paths F may be formed on both sides of one battery cell  10  in the column direction Z 1  of the battery cell  10 , and among the four cooling flow paths, at least one of the two adjacent cooling flow paths F formed on one side of the battery cell  10  may be exposed by the first opening region  131  individually formed for each of the cooling flow paths F, and the two adjacent cooling flow paths F formed on the other side of the battery cell  10  may be exposed by the coupling opening region  132   c  (or the second opening region  132 ) formed commonly for the two cooling flow paths F. As such, the first opening region  131  may be formed at one position of a certain battery cell, and the coupling opening region  132   c  (or the second opening region  132 ) may be formed at the other position of the battery cell, and the first and second opening regions  131  and  132  may be arranged in an alternating pattern in a column direction (for example, L 1  and L 2 ) of the battery cell  10  (or the filling hole FH). In an implementation, the coupling opening region  132   c  (or the second opening region  132 ) that functions as the coupling hole CH in the column direction (for example, L 1  and L 2 ) of the battery cell  10  (or the filling hole FH), and the first opening region  131  that does not function as the coupling hole CH may be arranged to alternate with each other. 
     Referring to  FIG. 13 , the second opening region  132  extending in the outer circumferential direction of the filling holes FH in adjacent rows (for example, L 1  and L 2 ) may be formed in different shapes, and for example, the second opening region  132  extending in the outer circumferential direction of the filling hole FH in the first row L 1  may extend in a downward direction toward the filling hole FH of the second row L 2  from the coupling member  125  in the outer circumferential direction of the filling hole FH. In contrast to this, the second opening region  132  extending in the outer circumferential direction of the filling hole FH in the second row L 2  may extend in an upward direction toward the filling hole FH of the first row L 1  from the coupling member  125  in the outer circumferential direction of the filling hole FH. As such, the extending directions of the second opening regions  132  extending in the outer circumferential direction of the filling hole FH may be formed differently from each other in the filling holes FH of the first and second rows L 1  and L 2  adjacent to each other, and thus, it is possible to reduce interference with each other and to densely arrange the second opening regions  132  in different extension directions at a narrow space between the filling holes FH in the first and second rows L 1  and L 2 . As such, it is described that the second opening region  132  extends in the outer circumferential direction of the filling hole FH, and in another embodiment, the filling hole FH may be omitted, and in this case, it may be understood that the second opening region  132  extends in an outer circumferential direction of a central position of the upper end portion  10   a  of the battery cell  10 . The filling hole FH may be formed at a central position of the upper end portion  10   a  of each battery cell  10  to expose the bus bar  120  connected to the central position of the upper end portion  10   a  of each battery cell  10 . 
     In an implementation, referring to  FIG. 1 , the circuit board  130  may be arranged on the upper holder  110   a  and may not be arranged on the lower holder  110   b . In an implementation, the circuit board  130  may be selectively arranged on any one of the upper holder  110   a  and the lower holder  110   b , e.g., the circuit board  130  may be arranged on the upper holder  110   a  and may collect voltage information of the multiple battery cells  10  through the upper end portion  10   a  of the battery cell  10 . In an implementation, the circuit board  130  may collect the voltage information of the multiple battery cells  10  through any one of the upper end portion  10   a  and the lower end portion  10   b  of each of the multiple battery cells  10 , e.g., the circuit board  130  may collect voltage information of the multiple battery cells  10  through the upper end portions  10   a  of the multiple battery cells  10 . The battery cell  10  may include different first and second electrodes  11  and  12  formed on the upper end portion  10   a  and the lower end portion  10   b , and according to one embodiment, the voltage information of the multiple battery cells  10  may be acquired through any one of the upper end portion  10  and the lower end portion  10   b  of the battery cell  10 , e.g., the upper end portion  10   a  of the battery cell  10  without connecting the circuit board  130  to both the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  to acquire the voltage information of the battery cells  10 , and the entire voltage information of the battery cells  10  may be collected through the circuit board  130  selectively arranged on the upper end portion  10   a  of the battery cell  10 , and thus, a structure of the entire battery pack may be simplified. In an implementation, an electrical connection of the battery cell  10  may be made through both the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , and a voltage of the battery cell  10  may be measured selectively through the upper end portion  10   a  of the battery cell  10  among the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . 
     If voltages of both sides of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  were to be measured, the circuit board  130  needs to be arranged on both sides of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , and thus, a structure of the entire battery pack may be complicated, and a separate wiring structure for connecting the circuit boards  130  on both sides may be required to collect voltage information measured from the circuit boards  130  on both sides. 
     Referring to  FIGS. 9 and 11 , in one embodiment, the potting resin PR may be formed at a position corresponding to a central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  in a height direction of the battery cell  10 , and the adhesive resin AR may be formed at a location corresponding to a rim surrounding a central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  in a height direction of the battery cell  10 . In this case, the potting resin PR and the adhesive resin AR may contain different components. 
     In an implementation, the bus bar  120  electrically connecting different battery cells  10  to each other may connect central portions of the upper end portions  10   a  of the adjacent battery cells  10  to each other. In this case, the potting resin PR may be formed on a central portion of the upper end portion  10   a  of the battery cell  10  and a coupling portion between the coupling pieces  120   a  at both ends of the bus bar  120 , and in one embodiment, the potting resin PR may be injected onto the coupling pieces  120   a  at both ends of the bus bar  120  through the filling hole FH of the circuit board  130 . 
     The potting resin PR may protect a coupling portion between the battery cell  10  and the coupling piece  120   a  of the bus bar  120  from harmful components such as oxygen and moisture by covering the coupling portion, and may protect heterogeneous materials bonded by welding, e.g., a coupling portion between the heterogeneous materials formed between the upper end portion  10   a  of the battery cell  10  and the coupling piece  120   a  of the bus bar  120  from galvanic corrosion. 
     The potting resin PR may be filled in the filling holes FH of the circuit board  130  which are arranged on the bus bars  120 , and the filling holes FH of the circuit board  130  may expose the coupling pieces  120   a  at both ends of the bus bars  120  connected to the battery cells  10 . For example, the filling hole FH may be formed for each battery cell  10 , and two bus bar  120 , each connecting two adjacent battery cells  10 , may be formed for each bus bar  120 , that is, one filling hole FH may be formed for each coupling piece  120   a  at both ends of the bus bar  120 , and the potting resin PR may be filled in each filling hole FH, and thereby, the potting resin PR filled in the filling hole FH may cover a coupling portion between the battery cell  10  and the bus bar  120  (each coupling piece  120   a  formed at both ends of the bus bar  120 ). For example, the potting resin PR filled in the filling hole FH of the circuit board  130  may be injected onto the coupling piece  120   a  of the bus bar  120  interposed between the circuit board  130  and the battery cell  10 . 
     In an implementation, the bus bar  120  may include the coupling pieces  120   a  at both ends, the central protrusion connection piece  120   c  connecting the coupling pieces  120   a  at both ends to each other, and the bent portions  120   b  that connect the coupling pieces  120   a  at both ends to the central protrusion connection piece  120   c  in a bent shape and supports the protrusion connection piece  120   c  at a level spaced apart from the battery cell  10  from the coupling pieces  120   a  at both ends in a height direction of the battery cell  10 . In this case, the escape hole  132   a  for completely exposing the entire protrusion connection pieces  120   c  may be formed in the circuit board  130  arranged on the bus bar  120 . As illustrated in  FIG. 12 , the protrusion connection piece  120   c  of the bus bar  120  and the circuit board  130  (a solid portion of the circuit board  130 ) may be arranged so as not to overlap each other in a height direction through the escape hole  132   a  formed in the circuit board  130 , and thereby, the circuit board  130  may be arranged at a position close to the coupling pieces  120   a  of the bus bar  120 , and by reducing the interval q between the circuit board  130  and the coupling pieces  120   a  of the bus bar  120  in a height direction, the amount of potting resin PR injected onto the coupling pieces  120   a  of the bus bar  120  through the filling hole FH of the circuit board  130  may be reduced, and contamination of the surroundings due to a flow of excess potting resin PR or uncontrolled potting resin PR may be prevented. 
     The potting resin PR may be injected onto the coupling pieces  120   a  at both ends of the bus bar  120  through appropriate fluidity in an uncured state and may be injected, e.g., through the filling hole FH of the circuit board  130 , and may protect a coupling portion between the bus bar  120  and the battery cell  10  from external harmful components such as oxygen or moisture by performing irradiation of UV light, heating, or curing according to time after injection. In addition, the potting resin PR may insulate the upper end portion  10   a  of the battery cell  10  exposed through the filling hole FH of the circuit board  130  from the bus bar  120 . In an implementation, the potting resin PR may include a urethane resin such as polyurethane. 
       FIG. 11  illustrates that the potting resin PR may be formed on the coupling portion between the upper end portion  10   a  of the battery cell  10  and the bus bar  120 , and the potting resin PR may also be formed on a coupling portion between the lower end portion  10   b  of the battery cell  10  and the bus bar  120 . In an implementation, the circuit board  130  may be formed selectively only on the upper end portion  10   a  of the battery cell  10  from among the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  (the circuit board  130  may be arranged selectively only on the upper holder  110   a  from among the upper holder  110   a  and the lower holder  110   b ), and in this case, the potting resin PR may be formed on the coupling portion between the lower end portion  10   b  of the battery cell  10  and the bus bar  120  without passing through the filling hole FH of the circuit board  130 . 
     Throughout the present specification, forming the potting resin PR at a position corresponding to a central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  in a height direction of the battery cell  10  may indicate that the potting resin PR is formed on the coupling portion between the battery cell  10  and the bus bar  120  to cover the coupling portion, and may indicate a configuration in which the potting resin PR is filled in the filling hole Fh of the circuit board  130  formed on the bus bar  120 . 
     In an implementation, in relation to the central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  in which the potting resin PR is formed, the potting resin PR may be formed at the central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  to which the coupling pieces  120   a  at both ends of the bus bar  120  are connected. In this case, the central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  indicates a position where the coupling pieces  120   a  at both ends of the bus bar  120  are connected in the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , and the central position of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  is not limited restrictively. In an implementation, in relation to the position where the potting resin PR is formed, the central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  may broadly indicate an inner region excluding the rim of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , that is, an inner region surrounded by the rim, and may be used to distinguish between a position where one of the first and second electrodes  11  and  12  is formed and a position where another electrode is formed, according to the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , and the central portion of the upper end portion  10   a  or the lower end  10   b  of the battery cell  10  may broadly indicate an inner region of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , with respect to a boundary that separates one electrode of the battery cell  10  from the other electrode. As described with reference to  FIG. 3 , the second electrode  12  of the battery cell  10  may be formed at the central portion of the upper end portion  10   a  of the battery cell  10 , and the first electrode  11  may be formed in the rim of the upper end portion  10   a . In this case, the central portion of the upper end portion  10   a  of the battery cell  10  in relation to the position where the coupling pieces  120   a  at both ends of the bus bar  120  are connected may indicate the second electrode  12  formed in the central portion of the upper end portion  10   a  of the battery cell  10 . 
     Referring to  FIGS. 9 and 10 , the upper end portion  10   a  of the battery cell  10  may be exposed through the terminal hole  112  of the upper holder  110   a  to which the battery cell  10  is assembled, and the upper end portion  10   a  of the battery cell  10  exposed through the terminal hole  112  of the upper holder  110   a  may be connected to the bus bar  120  arranged on the upper holder  110   a . In this case, the terminal hole  112  of the upper holder  110   a  and the filling hole FH of the circuit board  130  may be formed at positions corresponding to each other in the height direction of the battery cell  10 . The terminal hole  112  of the upper holder  110   a  is for exposing the upper end portion  10   a  of the battery cell  10 , and the filling hole FH of the circuit board  130  is for exposing the coupling pieces  120   a  of the bus bar  120  connected onto the upper end portion  10   a  of the battery cell  10 , and thus, the terminal hole  112  of the upper holder  110   a  and the filling hole FH of the circuit board  130  may be aligned at positions corresponding to each other in the height direction of the battery cell  10 . In an implementation, when the circuit board  130  is arranged on the lower holder  110   b , the terminal hole  112  of the lower holder  110   b  and the filling hole FH of the circuit board  130  may be aligned at positions corresponding to each other. 
     Referring to  FIGS. 10 and 11 , in one embodiment, the coupling member  125  for forming a voltage measurement line between the battery cell  10  and the circuit board  130  may be connected to the rim of the upper end portion  10   a  of the battery cell  10 . Here, the rim of the upper end portion  10   a  of the battery cell  10  may indicate a portion surrounding the central portion of the upper end portion  10   a . The coupling member  125  may electrically connect the battery cell  10  to the circuit board  130  through the coupling hole CH of the circuit board  130 , and one end portion of the coupling member  125  may form a bonding portion with the rim of the battery cell  10 , and the other end portion of the coupling member  125  may form a bonding portion with the circuit board  130 . In this case, the adhesive resin AR may cover the bonding portions of one end portion and the other end portion of the coupling member  125 , e.g., the adhesive resin AR may continuously cover the bonding portions of the one end portion and the other end portion of the coupling member  125 . In this case, the adhesive resin AR may cover the entire coupling member  125 . As the adhesive resin AR covers the bonding portions of the coupling member  125  formed on the rim of the upper end portion  10   a  of the battery cell  10  and on the circuit board  130 , the bonding portions may be protected from external impact, and as the adhesive resin AR covers the entire coupling member  125 , the coupling member  125  formed of a conductive wire or a conductive ribbon may be prevented from being disconnected due to an insufficient mechanical strength. 
     The adhesive resin AR may cover different coupling members  125  respectively bonded to the rims of the adjacent battery cells  10  exposed through the coupling hole CH. In an implementation, the adhesive resin AR may cover together the bonding portions of one end portion and the other end portion of each of the different coupling members  125  respectively bonded to the different battery cells  10  exposed through the coupling holes CH, and may continuously cover together the bonding portions of one end portion and the other end portion of each of the different coupling members  125 . In this case, the adhesive resin AR may entirely cover the different coupling members  125  respectively bonded to the different battery cells  10  exposed through the coupling holes CH. And, the adhesive resin AR may continuously cover the upper end portions  10   a  of the battery cells  10  exposed through the coupling holes CH while covering all of the different coupling members  125  and may electrically insulate the upper end portions  10   a  of the battery cells  10  exposed through the coupling holes CH. For example, the adhesive resin AR may cover the upper end portion  10   a  of the battery cell  10  exposed through the coupling hole CH together with the coupling member  125 , thereby, electrically insulating the coupling member  125  from the upper end portion  10   a  of the battery cell  10 . 
     The coupling member  125  is supported in a suspended state between one end portion bonded to the rim of the upper end portion  10   a  of the battery cell  10  and the other end portion connected to the circuit board  130 , and the adhesive resin AR is formed continuously to cover the entire coupling member  125  together with the bonding portions formed in one end portion and the other end portion of the coupling member  125 , and thereby, the coupling member  125  may be stably supported, and the coupling member  125  supported in a suspended state according to external impact may be stably supported without fluctuation. 
     The adhesive resin AR may include a two-liquid type curable resin containing components different from each other. In an implementation, the adhesive resin AR may include an epoxy adhesive and may include a two-liquid type curable resin containing epoxy as a main material and amine as a curable agent. For example, the adhesive resin AR may be cured by performing heating or curing according to time after being applied onto the coupling member  125 , and in another embodiment, the adhesive resin AR may be cured by irradiation of UV light. As such, the cured adhesive resin AR may firmly support the entire coupling member  125  including one end portion and the other end portion of the coupling member  125 . The adhesive resin AR may be applied onto the coupling member  125  through appropriate fluidity in an uncured state, and may be injected, for example, through the coupling hole CH, and may firmly support the coupling member  125  by performing irradiation of UV light, heating, or curing according to time after coating. 
     Referring to  FIGS. 10 and 11 , the adhesive resin AR may cover the rims of the upper end portions  10   a  of the adjacent battery cells  10  exposed through the coupling holes CH. In this case, the coupling hole CH may expose the hollow protrusion portion  115  connected to the cooling flow path F formed around the battery cell  10  covered by the adhesive resin AR. For example, the coupling hole CH may expose a pair of the hollow protrusion portions  115  facing each other with the coupling member  125  interposed therebetween, and in this case, the pair of hollow protrusion portions  115  may be formed between a pair of the battery cells  10  exposed through the coupling holes CH. 
     Throughout the present specification, forming the adhesive resin AR at a position corresponding to the rim of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  in the height direction of the battery cell  10  may indicate that the adhesion resin AR covers the bonding portions of the coupling member  125  formed on the rim of the battery cell  10  to, and may indicate a configuration in which the adhesive resin AR is filled in the coupling hole CH of the circuit board formed on an upper portion of the battery cell  10 . 
     In an implementation, in relation to the rim of the upper end portion  10   a  of the battery cell  10  in which the adhesive resin AR is formed, the adhesive resin AR may be formed on the rim of the upper end portion  10   a  of the battery cell  10  to which the coupling member  125  is connected. In this case, the rim of the upper end portion  10   a  of the battery cell  10  may indicate a position where the coupling member  125  is connected among the upper end portion  10   a  of the battery cell  10 , and a position of the rim of the upper end portion  10   a  of the battery cell  10  is not limited restrictively. In an implementation, in relation to the position where the adhesive resin AR is formed, the rim of the upper end portion  10   a  of the battery cell  10  may broadly indicate an outer region other than the central portion in the upper end portion  10   a  of the battery cell  10 , that is, an outer region surrounding the central portion, and is for distinguishing between a position where one electrode of the first and second electrodes  11  and  12  of the battery cell  10  is formed and a position where the other electrode is formed, along the upper end portion  10   a  of the battery cell  10 , and in relation to a position where the adhesive resin AR is formed, the rim of the upper end portion  10   a  of the battery cell  10  may broadly indicate the outer region of the upper end portion  10   a  of the battery cell  10  with respect to a boundary that separates one electrode of the battery cell  10  from the other electrode. 
     As described with reference to  FIG. 3 , the second electrode  12  of the first and second electrodes  11  and  12  of the battery cell  10  may be formed in a central portion of the upper end portion  10   a  of the battery cell  10 , and the first electrode  11  may be formed at a rim in the upper end portion  10   a  and the lower end portion  10   b . In this case, in relation to a position where the coupling member  125  is connected, the rim of the upper end portion  10   a  of the battery cell  10  may indicate the first electrode  11  formed at the rim of the upper end portion  10   a  of the battery cell  10 . 
       FIG. 11  illustrates the adhesive resin AR formed on the coupling member  125  coupling the upper end portion  10   a  of the battery cell  10  to the circuit board  130 . In an implementation, the circuit board  130  may be formed selectively on the upper end portion  10   a  of the battery cell  10  among the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  ((the circuit board  130  is arranged selectively only on the upper holder  110   a  among the upper holder  110   a  and the lower holder  110   b ), and in another embodiment, the circuit board  130  may also be formed on the lower end portion  10   b  of the battery cell  10 , and in this case, the adhesive resin AR may be formed on the coupling member  125  coupling the lower end portion  10   b  of the battery cell  10  to the circuit board  130 . 
     The potting resin PR and the adhesive resin AR may contribute to other purposes, and thus, different components having different material properties may be contained therein. For example, the potting resin PR has a function of protecting a coupling portion of the bus bar  120  from harmful components such as oxygen or moisture, and accordingly, the potting resin PR may have airtightness to block penetration of the harmful components. On the other hand, the adhesive resin AR may have adhesiveness for firm attachment of the coupling member  125  to protect the coupling member  125  such as a conductive wire or a conductive ribbon from external impact. 
     Referring to  FIGS. 14 to 16 , a separation member  140  may be arranged on the cell holder  110 . The separation member  140  may spatially separate the cooling flow path F of a cooling medium CM for cooling the battery cell  10  from an exhaust path of exhaust gas DG emitted from the vent portion  13  of the battery cell  10 . In an implementation, the separation member  140  may spatially separate the cooling flow path F and the exhaust path from each other, and thus, it is possible to reduce a risk of explosion or ignition caused by mixing of a cooling medium CM (such as air) flowing through the cooling path F with the exhaust gas DG of a high temperature and a high pressure flowing through the exhaust path. In an implementation, in a battery pack mounted on an electric vehicle, exhaust gas DG may be blocked from flowing into the inside of a vehicle along an uncontrolled path. 
     Referring to  FIG. 1 , the separation member  140  may include the upper separation member  140   a  on the upper holder  110   a  and the lower separation member  140   b  on the lower holder  110   b . In an implementation, the upper separation member  140   a  may be on the circuit board  130  on the upper holder  110   a . In an implementation, the circuit board  130  may not be on the lower holder  110   b , and thus, the lower separation member  140   b  may be directly on the lower holder  110   b . In an implementation, the lower separation member  140   b  may be on the lower bus bar  120   b  on the lower holder  110   b.    
     Referring to  FIG. 14 , an opening region  145  may be formed in the separation member  140  such that the cooling flow path F may penetrate therethrough. The cooling flow path F may be formed across the separation member  140  by penetrating the opening region  145  of the separation member  140  and, e.g., the cooling flow path F may penetrate the opening region  145  of the separation member  140 , e.g., the hollow protrusion portion  115  of the cell holder  110  may be fitted to the opening region  145  of the separation member  140 . To this end, the opening region  145  of the separation member  140  may be formed at a position corresponding to (e.g., overlying or vertically aligned with) the hollow protrusion portion  115  and may be formed in a shape corresponding to the arrangement of the hollow protrusion portion  115 . In an implementation, the opening region  145  may have a circular shape corresponding to the hollow protrusion portion  115  including the circular wall body  115   a  surrounding a central hollow portion. In an implementation, the opening region  145  may have various shapes corresponding to the hollow protrusion portion  115  and may be formed in various shapes including, e.g., ovals or hexagons. 
     Referring to  FIG. 15 , in one embodiment, the opening region  145  may include a wall body  145   a  extending toward or in parallel with the hollow protrusion portion  115 , e.g., the wall body  115   a  of the hollow protrusion portion  115  may be fitted to the wall body  145   a  of the opening region  145 . In this case, the wall body  145   a  of the opening region  145  and the wall body  115   a  of the hollow protrusion portion  115  may have a circular shape corresponding to each other, may be at positions corresponding to each other, and may extend toward or alongside each other and assembled by force fitting. In an implementation, an outer circumference of the wall body  115   a  of the hollow protrusion portion  115  may be fitted to an inner circumference of the wall body  145   a  of the opening region  145 , and the wall body  115   a  of the hollow protrusion portion  115  may be fitted to the wall body  145   a  of the opening region  145  by force fitting. In an implementation, the wall body  145   a  of the opening region  145  may have an inner circumference of a size that gradually decreases toward the hollow protrusion portion  115 , or the wall body  115   a  of the hollow protrusion portion  115  may have an outer circumference of a size that gradually expands toward the opening region  145 , and as the wall body  145   a  of the opening region  145  and the wall body  115   a  of the hollow protrusion portion  115  may have gradients to protrude toward each other, the wall body  145   a  of the opening region  145  and the wall body  115   a  of the hollow protrusion portion  115  may be forcibly assembled be fitted to each other. 
     A spacer  141  may be formed in the separation member  140  (e.g., on a bottom side of the separation member  140 ) to protrude toward the cell holder  110  and maintain an appropriate interval between the separation member  140  and the cell holder  110 . In an implementation, an interval, which is maintained by the spacer  141 , between the separation member  140  and the cell holder  110  may provide an exhaust path for exhaust gas emitted from the battery cell  10 . As will be described below, a space between the block region  144  of the separation member  140  and the cell holder  110  may form an exhaust path for emitting exhaust gas emitted from the upper end portion  10   a  of the battery cell  10  or the lower end portion  10   b  of the battery cell  10  (e.g., the vent portion  13  in the upper end portion  10   a  of the battery cell  10  or the lower end portion  10   b  of the battery cell  10 ), and in this case, the spacer  141  of the separation member  140  may help maintain an appropriate interval between the separation member  140  and the cell holder  110 . In an implementation, the spacer  141  on the upper separation member  140   a  may provide an exhaust path for exhaust gas emitted from the upper end portion  10   a  of the battery cell  10  while maintaining an interval between an upper surface of the upper holder  110   a  and the block region  144  of the upper separation member  140   a , and the spacer  141  formed on the lower separation member  140   b  may provide an exhaust path for exhaust gas emitted from the lower end portion  10   b  of the battery cell  10  while maintaining an interval between a lower surface of the lower holder  110   b  and the block region  144  of the lower separation member  140   b.    
     Referring to  FIGS. 14 and 15 , the opening regions  145  of the upper and lower separation members  140   a  and  140   b  may be formed at positions corresponding to each other to form the cooling flow paths F that penetrate at least some of the battery pack. The opening regions  145  of the upper and lower separation members  140   a  and  140   b  may form the cooling flow paths F that penetrate almost the entire configuration of a battery pack together with the hollow protrusion portion  115  of the cell holder  110  between the upper and lower separation members  140   a  and  140   b , and the opening region  135  of the circuit board  130  between the upper and lower separation members  140   a  and  140   b  in addition to the cell holder  110 . In an implementation, the cooling flow path F may penetrate the circuit board  130 , the upper and lower holders  110   a  and  110   b , and battery cell  10  fitted to the upper and lower holders  110   a  and  110   b  from the upper separation member  140   a  to be connected to the lower separation member  140   b  and may penetrate almost the entire configuration of the battery pack in the height direction. In an implementation, the opening regions  145  of the upper and lower separation members  140   a  and  140   b  and the opening regions  135  of the circuit board  130  may be formed at positions corresponding to or aligned with each other and may be formed at position corresponding to the hollow protrusion portions  115  to be fitted to the hollow protrusion portion  115  of the cell holder  110 . 
     The separation member  140  may include the block region  144  formed at a position corresponding to the vent portion  13  of the battery cell  10 . Hereinafter, the block region  144  of the upper separation member  140   a  will be mainly described. However, the technical matters relating to the upper separation member  140   a  which will described below may be applied to the lower separation member  140   b  in substantially the same manner. 
     Referring to  FIG. 16 , the block region  144  may be formed in the form of closing an upper portion of the vent portion  13  so that exhaust gas DG emitted from the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) of the battery cell  10  does not passes through the separation member  140 . In an implementation, the block region  144  may have a closed shape, and some of the separation member  140  may be opened like the opening region  145  so that upper and lower portions of the separation member  140  are in fluid communication with each other, and the upper and lower portions of the separation member  140  are separated from each other without being in fluid communication with each other through the block region  144 , and as the block region  144  is formed in a closed form, the lower portion of the block region  144  in which the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) is arranged is not in fluid communication with the upper portion of the block region  144  with respect to the block region  144 . 
     In an implementation, the lower portion of the block region  144  in which the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) and the upper portion of the block region  144  are separated from each other without being in fluid communication with each other with respect to the block region  144 , and thus, exhaust gas DG emitted from the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) may not flow out to the upper portion of the block region  144  through the block region  144 . In an implementation, the exhaust gas DG emitted from the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) may be blocked by the block region  144 , thereby, flowing along the exhaust path between the block region  144  and the battery cell  10 ) and may be emitted to the outside of the battery pack along the exhaust path. 
     Referring to  FIG. 7 , in one embodiment, a group of the battery cells  10  forming a battery pack may be arranged in a vertically inverted pattern in a height direction, and may include a first group of the battery cells  10  in which the vent portion  13  is formed in the upper end portion  10   a , and a second group of the battery cells  10  in which the vent portion  13  is formed in the lower end portion  10   b . In this case, as illustrated in  FIG. 16 , the block region  144  of the upper separation member  140   a  arranged on an upper surface of the upper holder  110   a  may be formed in a closed shape so that one side of the upper separation member  140   a  in which the upper end portions  10   a  (or the vent portions  13 ) of the first group of battery cells  10  are arranged, and the other side of the upper separation member  140   a  opposite to the upper end portions  10   a  (or the vent portions  13 ) of the first group of battery cells  10  may not be fluidly connected to each other. Similarly, the block region  144  of the lower separation member  140   b  arranged on a lower surface of the lower holder  110   b  may be formed in a closed shape so that one side of the lower separation member  140   b  in which the lower end portions  10   b  (or the vent portions  13 ) of the second group of battery cells  10  are arranged, and the other side of the lower separation member  140   b  opposite to the lower end portions  10   b  (or the vent portions  13 ) of the second group of battery cells  10  may not be fluidly connected to (e.g., may not be in fluid communication with) each other. 
     Referring to  FIG. 16 , the block region  144  may be formed over the entire region of the separation member  140  excluding the opening region  145  without being limited to a position corresponding to the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) of the battery cell  10 . In an implementation, the block region  144  may extend to cover the entire region of the separation member  140  across a space between the opening regions  145  except for the opening region  145  for penetrating the cooling flow path F, and may form an exhaust path continuously connected to the exhaust hole DH from a position corresponding to the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ). In an implementation, the exhaust gas DG emitted from the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) at different positions may be collected or directed into the exhaust hole DH along an exhaust path continuously formed or open between the block region  144  of the separation member  140  and the battery cell  10 . In an implementation, the exhaust path may be formed between the block region  144  of the separation member  140  and the battery cell  10  or between the block region  144  of the separation member  140  and the cell holder  110  (or the circuit board  130 ), and may be continuously formed or open from the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) of the each battery cell  10  to the exhaust hole DH on one side of the cell holder  110 . In an implementation, the exhaust path may be formed in a form in which spaces between the hollow protrusion portions  115  fitted to the opening regions  145  of the separation member  140  are continuously connected (e.g., in fluid communication), and the exhaust gas DG collected into the exhaust hole DH through the exhaust path may be emitted to the outside of the battery pack. In an implementation, an exhaust path for exhaust gas emitted from the upper end portion  10   a  or the lower end portion  10   b  (or the vent portions  13  formed in the upper end portion  10   a  and the lower end portion  10   b ) of the battery cell  10  may be formed between an upper surface of the upper holder  110   a  and the separation member  140   a  and between a lower surface of the lower holder  110   b  and the lower separation member  140   b , and may be formed in a form in which spaces between the hollow protrusion portions  115  fitted to the opening regions  145  of the upper separation member  140   a  and the lower separation member  140   b  are continuously connected. 
     The exhaust path of which one side is closed by the block region  144  formed in a closed form so that upper and lower portions of the separation member  140  are not connected to each other may be spatially separated from the cooling flow paths F penetrating upper and lower portions of the separation member  140  through the opening region  145  of the separation member  140 . In an implementation, the separation member  140  may be formed generally in a plate shape, e.g., may have a closed plate shape except for the opening region  145  opened so that the hollow protrusion portion  115  is fitted. In this case, the cooling flow path F may be spatially separated from an exhaust path formed between the separation member  140  (the block region  144 ) and the battery cell  10  while penetrating the separation member  140  through the opening region  145  in a state of being surrounded by the hollow protrusion portion  115 . A risk of accidents causing explosion or fire when the cooling medium CM flowing along the cooling flow path F and the exhaust gas DG of a high temperature and a high pressure flowing along the exhaust path are mixed with each other, may be reduced by the structure in which the cooling flow path F and the exhaust path are spatially separated from each other, and the battery pack mounted on an electric vehicle may block the exhaust gas DG that penetrates the separation member  140  to enter the inside of the vehicle, and thus, an occupant may be safely protected from toxic gas. 
     Referring to  FIGS. 1 and 17 , an upper duct  150   a  and a lower duct  150   b  may be arranged on the upper separation member  140   a  and the lower separation member  140   b . An opening OP for introducing a cooling medium may be in the upper duct  150   a , and the cooling medium introduced into a battery pack through the opening OP may cool the battery cell  10  while passing through the cooling flow path F formed from the upper separation member  140   a  up to the lower separation member. The cooling flow path F may be between the adjacent battery cells  10  to cool the battery cells  10  while flowing up and down in a height direction of the battery cells  10 . 
     A fluid device for generating a pressure difference between the inside and outside of a battery pack may be connected to the lower duct  150   b  to force a flow of a cooling medium passing through the battery pack. In an implementation, a coupling portion M of a fluid device may be on one side of the lower duct  150   b . In an implementation, the fluid device may be a suction type pump for forming a negative pressure inside a battery pack with respect to an external atmosphere of the battery pack. The fluid device (or the coupling portion M of the fluid device) connected to the lower duct  150   b  may form an outlet of the cooling medium introduced through the opening OP of the upper duct  150   a . In an implementation, the opening OP of the upper duct  150   a  may form an inlet of the cooling medium, and the fluid device (or the coupling portion M of the fluid device) connected to the lower duct  150   b  may form an outlet of the cooling medium. In an implementation, the fluid device may be provided as a blower type pump, and in this case, the fluid device (or the coupling portion M of the fluid device) connected to the lower duct  150   b  may form an inlet of a cooling medium, and the opening OP of the upper duct  150   a  may form an outlet of the cooling medium. 
     A cooling medium may flow into the inside of a battery pack through the opening OP of the upper duct  150   a  according to a pressure difference between the inside and outside of the battery pack while a negative pressure is formed inside the battery pack according to an operation of a fluid device, and the cooling medium introduced into the battery pack may cool the battery cell  10  while passing through the cooling flow path F and may be emitted to the outside of the battery pack through a fluid device connected to the coupling portion M of the lower duct  150   b.    
     In an implementation, the opening OP in the upper duct  150   a  and a fluid device (or the coupling portion M of a fluid device formed in the lower duct  150   b ) connected to the lower duct  150   b  may each form an inlet and an outlet of a cooling medium, and accordingly, a position of the opening OP formed in the upper duct  150   a  and a position (or a position of the coupling portion M formed in the lower duct  150   b ) of the fluid device connected to the lower duct  150   b  may be formed at a diagonal position diagonally crossing a battery pack. 
     Throughout the present specification, in relation to an inlet position and an outlet position of a cooling medium, a diagonal direction of a battery pack may indicate a direction that simultaneously follows a height direction of the battery cell  10  and the long side direction Z 1  of the envelope S 1  and S 2  (see  FIG. 4 ) surrounding the battery cells  10 . In an implementation, when a group of the battery cells  10  forming a battery pack is surrounded by a rectangular envelope S 1  and S 2  (see  FIG. 4 ) including a pair of short side S 2  and a pair of long side S 1  extending to linearly surround an outer periphery of a group of the battery cells  10  across an outer circumference of a group of the battery cells  10 , the diagonal direction of the battery pack may indicate a direction that simultaneously follows a height direction of the battery cell  10  and the long side direction Z 1  of the envelope S 1  and S 2 . For reference, the long side direction Z 1  and the short side direction Z 2  of the envelope S 1  and S 2  may correspond to a long side direction and a short side direction of the cell holder  110 , and may correspond to a long side direction and a short side direction of a battery pack. 
     In an implementation, it is possible to induce a flow of a cooling medium passing through the entire inside of a battery pack through the opening OP of the upper duct  150   a  formed at a diagonal position crossing the battery pack in a diagonal direction and a fluid device (or the coupling portion M formed in the lower duct  150   b ) of the lower duct  150   b . In an implementation, a position of the opening OP in the upper duct  150   a  and a position of a fluid device (or the coupling portion M formed in the lower duct  150   b ) connected to the lower duct  150   b  may be formed at positions spaced apart (e.g., laterally) from each other in the long side direction Z 1  of the envelope S 1  and S 2  or the long side direction Z 1  of a battery pack. In an implementation, when the position of the opening OP formed in the upper duct  150   a , e.g., a position of at least some of the openings OP formed in the upper duct  150   a  is formed at one edge in the long side direction of the battery pack, a position (or a position of the coupling portion M formed in the lower duct  150   b ) of a fluid device connected to the lower duct  150   b  may be formed at the other edge in the long side direction of the battery pack. As such, the opening OP in the upper duct  150   a  and a fluid device (or the coupling portion M formed in the lower duct  150   b ) connected to the lower duct  150   b  may be formed at one edge and the other edge of the battery pack in the long side direction, and thereby, a cooling medium coupling the opening OP of the upper duct  150   a  to a fluid device (or the coupling portion M formed in the lower duct  150   b ) of the lower duct  150   b  may be formed to flow across the entire inside of a battery pack (e.g., to be exposed to each battery cell). 
     As described above, the coupling portion M of the fluid device may be at one edge in the long side direction of the battery pack, and a fixed portion FX of the fluid device may be at the one edge of the battery pack in which the coupling portion M of the fluid device is formed, together with the coupling portion M of the fluid device. In an implementation, in the fluid device, a position of the fluid device may be fixed through the fixed portion FX of the fluid device while a suction hole or an air outlet of the fluid device is connected to the coupling portion M of the fluid device depending on types of the fluid device. In an implementation, the exhaust pipe DP may be at the one edge or side of the battery pack in which the coupling portion M of the fluid device is formed. The exhaust pipe DP may protrude in an installation space toward the outside of the battery pack, and the exhaust pipe DP may be at one edge of the battery pack to which the fluid device is connected, and by intensively forming the coupling portion M of the fluid device described above, the fixed portion FX of the fluid device, and the exhaust pipe DP, the other edge of the battery pack may provide a (e.g., relatively flatter) position alignment surface of the battery pack, e.g., a reference surface may be provided for position alignment with an electric vehicle in which the battery pack is mounted. 
     According to an embodiment, in a battery pack including electrical connections of multiple battery cells, a greatest potential difference (highest voltage) between adjacent battery cells may be reduced, and thus, the battery pack may reduce a risk of an electrical short-circuit between the adjacent battery cells and may help improve safety. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.