Patent Publication Number: US-2021167346-A1

Title: Battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2019-0157585, 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; a potting resin on the battery cells at positions corresponding to central portions of upper end portions or lower end portions of the battery cells in a height direction of the battery cells; and an adhesive resin on the battery cells at positions corresponding to edge portions surrounding the central portions of the upper end portions or the lower end portions of the battery cells. 
     The battery pack may further include bus bars that electrically connect two of the battery cells to each other, the bus bars being coupled to the central portions of the upper end portions or the lower end portions of the battery cells. 
     The potting resin may cover coupling structures between the bus bars and the upper end portions or the lower end portions of the battery cells. 
     The battery pack may further include a circuit board on the bus bars, wherein the bus bars each include coupling pieces at both ends thereof that are coupled to the upper end portions of the battery cells, the circuit board includes filling holes that expose the coupling structures at both ends of the bus bars, and the potting resin is filled in the filling holes of the circuit board. 
     The battery pack may further include a cell holder in which the battery cells are accommodated, the cell holder having terminal holes that expose the upper end portions of the battery cells, wherein the terminal holes of the cell holder and the filling holes of the circuit board are aligned with each other in the height direction of the battery cells. 
     Each of the bus bars may further include a protruding connection piece that connects the coupling pieces; and bent portions that connect the coupling pieces with the protruding connection piece at a center of the bus bar in a bent shape and space the protruding connection piece apart from the coupling pieces from the battery cells in the height direction of the battery cells. 
     The circuit board may further include escape holes that each expose the protruding connection piece. 
     The battery pack may further include connection members coupled to the edge portions of the upper end portions of the battery cells. 
     The battery pack may further include a circuit board electrically connected to the battery cells is on the battery cells, wherein the connection members pass through connection holes of the circuit board and electrically connect the battery cells with the circuit board. 
     One end of each connection member may form a junction with an edge portion of the upper end portion of a corresponding battery cell, another end of the connection member may form a junction with the circuit board, and the adhesive resin may cover the junctions of the one end and the other end of each connection member. 
     The adhesive resin may continuously cover the junctions of the one end and the other end of each connection member. 
     The adhesive resin may entirely cover each connection member. 
     The connection members may include conductive wires or conductive ribbons. 
     The connection holes of the circuit board may expose the edge portions of the upper end portions of the battery cells. 
     The adhesive resin may cover the edge portions of the upper end portions of the battery cells exposed by the connection holes. 
     The battery pack may further include a cell holder including hollow protrusions that are connected to cooling flow paths around each battery cell covered by the adhesive resin and that pass through the circuit board. 
     The connection holes may expose the hollow protrusions and the edge portions of the upper end portions of the battery cells. 
     The connection holes may expose the edge portions of the upper end portions of two of the battery cells adjacent to each other, two connection members may be bonded to the edge portions of the upper end portions of the two adjacent battery cells, respectively, and the adhesive resin may cover the junctions formed at one end and the other end of each of the connection members. 
     The adhesive resin may entirely cover the two connection members, and continuously covers the edge portions of the upper end portions of the two adjacent battery cells exposed by the connection hole. 
     The potting resin and the adhesive resin may include different components. 
     The adhesive resin may include a two-component curable resin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will become 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. 
       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  FIG. 11 , a battery pack according to an embodiment may include battery cells  10 , a potting resin PR at positions corresponding to central portions of upper end portions  10   a  or lower end portions  10   b  of the battery cells  10  in a height direction of the battery cells  10 ; and an adhesive resin AR at positions corresponding to edge portions surrounding the central portions of the upper end portions  10   a  or the lower end portions  10   b  of the battery cells  10  in the height direction of the battery cells  10 . 
     Hereinafter, the battery pack according to an embodiment will be described in more detail. 
     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  that extends across a plurality of battery cells  10  may include connection holes CH (see  FIG. 1 ) each for exposing the edge portions of the upper end portions  10   a  of a pair of adjacent battery cells  10 , and the edge portions of the upper end portions  10   a  of the battery cells  10  exposed by the connection hole CH may form the first electrodes  11  having the same polarity. In an implementation, the pair of adjacent battery cells  10  exposed by the same connection hole CH may be arranged in a pattern in which one of the pair of adjacent battery cells  10  is inverted in the height direction of the battery cells  10 , however, the edge portions of the upper end portions  10   a  of the pair of adjacent battery cells  10  may form the first electrodes  11  having the same polarity regardless of the vertical arrangement of the battery cells  10 . As illustrated in  FIG. 3 , the can N forming the first electrode  11  may extend from the edge portion of the upper end portion  10   a  to the entire lower end portion  10   b , thus, regardless of the vertical arrangement of the battery cells  10 , both the edge portions of the upper end portions  10   a  and the edge portions of the lower end portions  10   b  of the adjacent battery cells  10  may form the first electrodes  11  having the same polarity. 
     As described below, using bus bars  120 , the upper end portions  10   a  of the pair of adjacent battery cells  10  may be electrically connected to each other, and the lower end portions  10   b  of the pair of adjacent battery cells  10  may be electrically connected to each other. In this case, the bus bars  120  may connect the central portions of the upper end portions  10   a  of the pair of adjacent battery cells  10  to each other, and may connect the central portions of the lower end portions  10   b  of the pair of adjacent battery cells  10  to each other. As illustrated in  FIG. 3 , the central portion of the upper end portion  10   a  may be formed as the cap assembly E forming the second electrode  12 , 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  according to the vertical arrangement. Through the present specification, in the case where the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  form the first electrode  11  and the second electrode  12  or the second electrode  12  and the first electrode  11 , respectively, the central portion of the upper end portion  10   a  of the battery cell  10  and the central portion of the lower end portion  10   b  of the battery cell  10  may form the first electrode  11  and the second electrode  12  or the second electrode  12  and the first electrode  11 , respectively. In addition, in the case where the bus bars  120  connect the upper end portions  10   a  and the lower end portions  10   b  of the pair of adjacent battery cells  10 , the bus bars  120  may connect the central portions of the upper end portions  10   a  and the lower end portions  10   b  of the pair of adjacent battery cells  10  to each other. 
     Through the present specification, the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  may refer to an end portion at the top and an end portion at the bottom of the battery cell  10  in the height direction, respectively, according to their positions rather than the first electrodes  11  or the second electrodes  12  that they form. That is, the upper end portions  10   a  of the pair of adjacent battery cells  10  may form the first electrodes  11  or the second electrodes  12  such that the upper end portions  10   a  have the same electrodes, or may form the first electrode  11  and the second electrode  12  such that the upper end portions  10   a  have the electrodes different from each other, according to the arrangement of the battery cells  10 . 
     Referring to  FIG. 2 , according to an embodiment, the pair of adjacent battery cells  10  may be arranged in a pattern in which one of the battery cells  10  is inverted in the height direction (e.g., alternating up and down arrangements), thus the upper end portions  10   a  of the pair of adjacent battery cells  10  may form the first and second electrodes  11  and  12 , and the lower end portions  10   b  of the pair of adjacent battery cells  10  may also form the first and second electrodes  11  and  12 . 
     Each of the pair of battery cells  10  adjacent to each other along an electrical connection route, may be electrically connected to each other, and the pair of adjacent battery cells  10  may be arranged in the pattern in which one of the pair of adjacent battery cells  10  is inverted in the height direction of the battery cells  10  such that the first and second electrodes  11  and  12  of the pair of adjacent battery cells  10  may be connected to each other in series. In an implementation, the first and second electrodes  11  and  12  of the pair of adjacent battery cells  10  may be connected to each other in parallel. In an implementation, each of a group of the battery cells  10  that constitutes the battery pack may be connected to the adjacent battery cell  10  in series, and the battery pack according to an embodiment may not include a parallel connection between the pair of adjacent battery cells  10 . In an implementation, the battery pack may include serial connections and/or parallel connections between the adjacent battery cells  10 . 
     In an implementation, the pair of battery cells  10  adjacent to each other along the electrical connection route may be arranged a pattern in which one of the battery cells  10  is vertically inverted, and the first and second electrodes  11  and  12  of the pair of adjacent battery cells  10  may be connected to each other in series, by connecting the upper end portions  10   a  of the pair of adjacent battery cells  10  to each other and the lower end portions  10   b  of the pair of adjacent battery cells  10  to each other. In an implementation, the first and second electrodes  11  and  12  of the pair of adjacent battery cells  10  may be connected to each other in parallel. 
     Through the present specification, the electrical connection route of the battery cells  10  refers to directions in which the adjacent battery cells  10  are electrically connected to each other, rather than a specific single direction, and may include different directions in which the adjacent battery cells  10  are connected to each other by arrangements of the bus bars  120 . 
     In an implementation, the electrical connection route of the battery cells  10  may have a zigzag configuration. As will be described in greater detail below, the battery cells  10  may be circular battery cells  10 , and the battery cells  10  may be alternately arranged such that each of the battery cells  10  is arranged in valley regions of the adjacent battery cells  10  in adjacent columns and thus, may be arranged densely (e.g., in an offset arrangement to be closely packed). As described above, the plurality of battery cells  10  alternately arranged may be electrically connected to each other by the plurality of bus bars  120  arranged in zigzag patterns, and the electrical connection route may be formed in a zigzag configuration along the directions in which the plurality of bus bars  120  are arranged. 
     Referring to  FIG. 2 , each of the group of the battery cells  10  that constitutes the battery pack may be electrically connected to each other along the electrical connection route in which the plurality of bus bars  120  are arranged, and the battery cell  10  at one end and the battery cell  10  at the other end of the electrical connection route may correspond to a low-potential battery cell  10  having the lowest potential and a high-potential battery cell  10  having the highest potential, respectively, in the group of the battery cells  10 . First and second output terminals  121  and  122  may be connected to the low-potential battery cell  10  and the high-potential battery cell  10 , respectively. 
     The first and second output terminals  121  and  122  may provide electrical connection between the group of battery cells  10  electrically connected to each other and an external device, and the group of battery cells  10  may supply discharge power to an external load through the first and second output terminals  121  and  122  or may receive charge 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 that may be between the first and second output terminals  121  and  122  to constitute a charge/discharge path. The fuse box may constitute the charge/discharge path between the first and second output terminals  121  and  122 , and thus, the charge/discharge path of the group of the battery cells  10  may pass through the 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 the charge/discharge path may be blocked in response to the overcurrent. 
     In an implementation, the first and second fuse terminals  123  and  124  may be connected to a pair of battery cells  10 , respectively, that are between the low-potential battery cell  10  at the one end and the high-potential battery cell  10  at the other end of the electrical connection route of the battery cells  10  along which the plurality of bus bars  120  are arranged, and thus, the pair of battery cells  10  may be electrically connected to each other through the 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 correspond to fuse terminals closest to the first and second output terminals  121  and  122 , respectively, along the electrical connection route of the battery cells  10  along which the plurality of 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 of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 . In the case where the vent portion  13  is formed at one end of the battery cell  10 , the vent portion  13  may be formed along an edge portion of the one end of the battery cell  10 . For example, the vent portion  13  may be formed along an edge of the second electrode  12  formed at the central portion of the one end of the battery cell  10 , and may be formed along the edge portion of the one end of the battery cell  10 . 
     In an implementation, a plurality of vent portions  13  spaced apart from each other may be formed along the edge portion of the one end of the battery cell  10 . The vent portion  13  is to relieve an internal pressure of the battery cell  10 , and for example, the vent portion  13  may formed at a portion with a relatively low strength in the one end of the battery cell  10 . If the internal pressure of the battery cell  10  exceeds a predefined critical pressure (corresponding to a rupture pressure of the vent portion  13 ), the vent portion  13  may be ruptured to relieve the internal pressure. 
     Referring to  FIG. 1 , exhaust gas discharged through the vent portion  13  by the internal pressure of the battery cell  10  may be discharged to the outside of the battery pack along the exhaust gas path of which one side is blocked by a blocking region  144  of a separation member  140 . In an implementation, the blocking region  144  corresponding to the vent portions  13  of the battery cells  10  may be formed in the separation member  140 , and the exhaust gas discharged through the vent portions  13  may be discharged to the outside of the battery pack through the exhaust gas path between the blocking region  144  of the separation member  140  and the battery cells  10 . The separation member  140  and the exhaust gas path will be described in more detail later. 
     Hereinafter, the arrangements of the battery cells  10  and positions of the cooling flow paths F between the battery cells  10  according to an embodiment will be described with reference to  FIG. 4 . 
     The cooling flow paths F may be formed between the adjacent battery cells  10 . In an implementation, the battery cells  10  may be circular battery cells  10 , the battery cells  10  may be alternately arranged such that each of the battery cells  10  is arranged in valley regions of the adjacent battery cells  10  in adjacent columns and thus, may be arranged densely by utilizing spaces between the adjacent battery cells  10 , and accordingly dead spaces may be reduced and the battery pack may have a relatively high energy density compared to its area. 
     In an implementation, the battery cells  10  may be arranged along a column direction Z 1  of the battery cells  10 , and may be alternately arranged such that each of the battery cells  10  is arranged in valley regions of the adjacent battery cells in adjacent columns. The column direction Z 1  of the battery cells  10  may refer to a direction in which the battery cells  10  are linearly arranged. The column direction Z 1  of the battery cells  10  may be different from directions in which the plurality of battery cells  10  are electrically connected, e.g., the directions constituting the electrical connection route of the battery cells  10 , and the column direction Z 1  of the battery cells  10  may refer to a direction in which the battery cells  10  are arranged, regardless of electrical connection states of the battery cells  10 . 
     According to an embodiment, the battery cells  10  may be linearly arranged along the column direction Z 1 , and may be arranged in a zigzag configuration along a row direction Z 2  perpendicular to the column direction Z 1 . In an implementation, the battery cells  10  having the circumferences adjacent to each other may be linearly arranged along the column direction Z 1 , and may be arranged in the zigzag configuration along the row direction perpendicular to the column direction Z 1 . In this case, the battery cells  10  having the circumferences adjacent to each other may be arranged such that, e.g., in the group of the battery cells  10  that constitutes the battery pack, distances between the circumstances of the adjacent battery cells  10  are equal to a minimum gap SG. In an implementation, the minimum gap SG may be set to secure electrical insulation between the adjacent battery cells  10  and sufficient heat dissipation, and for example, the minimum gap SG may be about 1 mm. 
     In an implementation, supposing that the group of battery cells  10  that constitutes the battery pack is surrounded by a rectangular envelope S 1  and S 2  consisting of a pair of long side lines S 1  and a pair of short side lines S 2  that extend to linearly surround the circumference of the group of battery cells  10 , the column direction Z 1  in which the battery cells  10  are linearly arranged may correspond to a direction parallel to the long sides S 1  of the envelope S 1  and S 2 , and the row direction in which the battery cells  10  are arranged in the zigzag configuration may correspond to a direction similar to the short sides S 2  of the envelope S 1  and S 2 . 
     Referring to  FIG. 4 , the battery cells  10  of first and second columns R 1  and R 2  may be densely arranged such that the battery cells  10  of the first column R 1  are in valley regions of the battery cells  10  of the second column R 2 , and similarly, the battery cells  10  of the second column R 2  and a third column R 3  may be densely arranged such that the battery cells  10  of the second column R 2  are in valley regions of the battery cells  10  of the third column R 3 . 
     Each of the battery cells  10  may be in the valley regions of the adjacent battery cells  10 , thus the circumferences of three battery cells  10  may be adjacent to each other around the battery cells  10 , and the cooling flow path F may be formed between the three battery cells  10 . The cooling flow path F may be formed in a spare region between the three battery cells  10 , of which circumferences are adjacent to each other, that is not occupied by the battery cells  10 , e.g., a valley region. 
     In an implementation, the cooling flow paths F may be formed between the battery cells  10  of the first column R 1  and the battery cells  10  of the second column R 2  adjacent to each other, and one cooling flow path F may be formed between two battery cells  10  of the first column R 1  and one battery cell  10  of the second column R 2 , and one cooling flow path F may be formed between two battery cells  10  of the second column R 2  and one battery cell  10  of the first column R 1 . Similarly, the cooling flow paths F may be formed between the battery cells  10  of the second column R 2  and the battery cells  10  of the third column R 2  adjacent to each other, and one cooling flow path F may be formed between two battery cells  10  of the second column R 2  and one battery cell  10  of the third column R 3 , and one cooling flow path F may be formed between two battery cells  10  of the third column R 3  and one battery cell  10  of the second column R 2 . 
     Referring to  FIG. 4 , six cooling flow paths F may be formed along the circumferential direction of one battery cell  10  of the second column R 2 . In an implementation, one battery cell  10  of the second column R 2  may form a plurality of valley regions between six battery cells  10  (the battery cells  10  of the first to third columns R 1 , R 2 , and R 3 ) along the circumferential direction, may form a total of six valley regions between every two battery cells  10  sequentially along the circumferential direction, and may form a total of six cooling flow paths F, one for each of the six valley regions. 
     Hereinafter, the arrangements of the plurality of bus bars  120  and the electrical connection of the battery cells  10  in which the plurality of bus bars  120  are arranged will be described with reference to  FIGS. 4 and 5 . For reference, in  FIG. 5 , for convenience of understanding, upper bus bars  120   a  (see  FIG. 1 ) and lower bus bars  120   b  (see  FIG. 1 ) are shown together, and the entire electrical connection by the upper bus bars  120   a  and the lower bus bars  120   b  is shown. 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 being distinguished from each other. In an implementation, the electrical connection shown in  FIG. 5  may be implemented through the upper bus bars  120   a  and the lower bus bars  120   b  alternately arranged on upper and lower portions of a cell holder  110 . Meanwhile, the numbers in the circles shown in  FIG. 5  may indicate an order of the battery cells  10  counted along the electrical connection route. 
     Referring to  FIGS. 4 and 5 , the plurality of bus bars  120  that electrically connect the pair of adjacent battery cells  10  may be arranged in a zigzag configuration. In an implementation, the battery cells  10  may be circular battery cells  10 , and the battery cells  10  may be alternately arranged such that each of the battery cells  10  is arranged in valley regions of the adjacent battery cells  10  in adjacent columns and thus, may be arranged densely. 
     In an implementation, supposing that the group of battery cells  10  that constitutes the battery pack is surrounded by the rectangular envelope S 1  and S 2  consisting of the pair of long side lines S 1  and the pair of short side lines S 2  that extend to linearly surround the circumference of the group of battery cells  10 , the group of battery cells  10  that constitutes the battery pack may be configured in arrangements in the column direction Z 1  that linearly extends in parallel with the direction of the long side line S 1  and arrangements in the row direction that extends in a zigzag shape similar to the direction of the short side line S 2 . In an implementation, the row direction that extends in the zigzag shape may be similar to the direction Z 2  of the short side line S 2 , that is shorter than the long side line S 1 , rather than the direction Z 1  of the long side line S 1  of the group of battery cells  10 . In this case, the plurality of bus bars  120  that electrically connect the adjacent battery cells  10  may be arranged in the zigzag shape while connecting the adjacent battery cells  10  along the arrangements of the battery cells  10  in the row direction that extends in the zigzag shape. 
     In the present disclosure, the arrangements of the plurality of bus bars  120  and the electrical connection route of the battery cells  10  along which the bus bars  120  are arranged may be configured in the row direction similar to the direction Z 2  of the short side line S 2  shorter than the long side line S 1 , rather than in the column direction Z 1  parallel to the direction of the long side line S 1 , thus potential differences (voltages) between the battery cells  10  electrically connected to each other in one arrangement along the row direction and the battery cells  10  electrically connected to each other in the arrangement adjacent to the one arrangement along the row direction may be reduced, and for example, by reducing the potential differences between the battery cells  10  in the adjacent arrangements along the row direction Z 1 , a risk of an electrical short between the adjacent battery cells  10  may be reduced and the safety of the battery pack may be improved. The battery cells  10  in the one arrangement and the adjacent arrangement may be electrically connected to each other through the bus bars  120  in an arrangement in the row direction that extends in the zigzag shape and may be arranged to be adjacent to each other along the column direction Z 1  perpendicular to the row direction. In this case, a maximum potential difference (maximum voltage) between the battery cells  10  adjacent to each other along the column direction Z 1  in the adjacent arrangements, for example, a maximum potential difference (maximum voltage) between the seventh battery cell  10  in the one arrangement and the eighteenth battery cell  10  in the arrangement adjacent to the one arrangement may be calculated by multiplying the number of the bus bars  120  that electrically connect the two battery cells  10 , that is,  11 , by a full charge voltage of each of the battery cells  10 , that is 4.2 V, since a difference equal to the full charge voltage may occur between two adjacent battery cells  10  connected by the bus bar  120 . In an implementation, the maximum potential difference (maximum voltage) between the two adjacent battery cells  10 , the seventh and eighteenth battery cells  10 , may be 46.2 V. As will be described later, the battery pack according to an embodiment may have a 72-cell structure in which 72 battery cells  10  are configured, and may include a high-voltage excursion HVe for compatibility with a 64-cell structure in which 64 battery cells  10  are configured, in which case, a maximum potential difference (maximum voltage) between two adjacent battery cells  10 , the nineteenth and fortieth battery cells  10 , may be 88.2 V. It may be determined that the safety of the battery pack is improved, in that in comparative examples shown in  FIGS. 6A to 6C , maximum potential differences (maximum voltages) between the two adjacent battery cells  10  are greater than 200 V or approaches 200 V. 
     If the arrangements of the plurality of bus bars  120  were configured along the column direction Z 1  rather than the row direction, the number of pairs of adjacent battery cells  10  arranged along the column direction Z 1 , in which each pair of adjacent battery cells  10  are electrically connected to each other through the bus bar  120 , is greater than the number of pairs of adjacent battery cells  10  arranged along the row direction, thus the number of bus bars  120  arranged along the column direction Z 1  is also greater than the number of bus bars  120  arranged along the row direction, and accordingly, the maximum voltage between the adjacent battery cells  10  increases, resulting in an increased risk of an electrical short between the adjacent battery cells  10 . 
     Referring to  FIG. 5 , according to an embodiment, a group of the bus bars  120  that constitutes the battery pack may include the bus bars  120  extending in a zigzag shape along the row direction and the bus bars  120  extending along the column direction Z 1 , however, the arrangements of the bus bars  120  and the electrical connection route of the battery cells  10  along which the bus bars  120  are arranged may be regarded as being along the row direction. In an implementation, whether the group of the bus bars  120  that constitutes the battery pack is arranged along the row direction or the column direction Z 1  may be determined by comparing the number of the bus bars  120  along the row direction and the number of the bus bars  120  along the column direction Z 1 , and according to an embodiment, one bus bar  120  along the column direction Z 1  may be arranged per approximately five bus bars  120  along the row direction, thus the arrangements of the bus bars  120  and the electrical connection route of the battery cells  10  along which the bus bars  120  are arranged may be regarded as being along the row direction rather than the column direction Z 1 . 
     In an implementation, the arrangements of the bus bars  120  and the electrical connection route of the battery cells  10  along which the bus bars  120  are arranged may be configured along the row direction that extends in a zigzag shape, and the arrangement, as one unit, in which the bus bars  120  extend along the row direction may be repeatedly configured along the column direction Z 1 , and in this case, the first and second output terminals  121  and  122  may be arranged along the column direction Z 1 , that is, the direction of the long side lines of the envelope S 1  and S 2 . The first and second output terminals  121  and  122  may be arranged in the direction Z 1  of the long side lines of the envelope S 1  and S 2  that surrounds the group of the battery cells  10 , thus electrical connections may be established along the row direction that is similar to the direction Z 2  of the short side lines of the envelope S 1  and S 2 , and accordingly, the maximum potential differences (maximum voltages) between the adjacent battery cells  10  may be reduced. 
     Like the comparative examples illustrated in  FIGS. 6A to 6C , if the first and second output terminals  121  and  122  were to be arranged along the direction Z 2  of the short side lines of the envelope S 1  and S 2  that surrounds the group of the battery cells  10 , the voltage of the adjacent battery cells  10  may be relatively increased as compared with the embodiment illustrated in  FIG. 5 , and maximum potential differences (maximum voltages) may be generated at portions indicated by the ellipses in  FIGS. 6A to 6C , and the maximum potential differences (maximum voltages) may be greater than 200 V or may approach 200 V. More specifically, in the comparative examples illustrated in  FIGS. 6A to 6C , the maximum potential differences (maximum voltages) are 210 V, 180.6 V, and 273 V, respectively. 
     In the comparative examples illustrated in  FIGS. 6A to 6C , the arrangements of the bus bars  120  or the electrical connection route of the battery cells  10  along which the bus bars  120  are arranged are configured along the column direction Z 1  parallel to the direction of the long side lines of the envelope S 1  and S 2  rather than the row direction similar to the direction Z 2  of the short side lines of the envelope S 1  and S 2 , and thus, the potential differences between the adjacent battery cells  10  and the risk of an electrical short between the adjacent battery cells  10  may increase. For example, in the comparative example illustrated in  FIG. 6C , although the electrical connection route of the battery cells  10  is configured along the row direction similar to the direction Z 2  of the short side lines of the envelope S 1  and S 2 , the arrangement, as one unit, in which the bus bars  120  extend along the row direction is repeatedly configured along the column direction Z 1  parallel to the direction Z 1  of the long side lines of the envelope S 1  and S 2  while reciprocating along the column direction Z 1 , and thus, the maximum potential difference (maximum voltage) between the pair of adjacent battery cells  10  in the portion indicated by the eclipse may increase. According to an embodiment illustrated in  FIG. 5 , the arrangement in which the bus bars  120  extend along the row direction may be repeatedly configured along the column direction Z 1  parallel to the direction Z 1  of the long side lines of the envelope S 1  and S 2 , from one short side line S 2  to the other short side line S 2  of the envelope S 1  and S 2  unidirectionally without reciprocating. 
     Referring to  FIG. 5 , according to an embodiment, the group of bus bars  120  and the group of battery cells  10  that constitute the battery pack may be divided into a low-voltage area LV that encompasses 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 area HV that encompasses 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 correspond to the fuse terminals, which are connected to the fuse box, closest to the first and second output terminals  121  and  122 , respectively, along the electrical connection route of the battery cells  10 , and may be connected to the first and second output terminals  121  and  122  along the electrical connection route without passing through the fuse box (not shown). 
     In an implementation, the boundary between the low-voltage area LV and the high-voltage area HV may be asymmetrical with respect to the line O in  FIG. 5  passing between the first and second fuse terminals  123  and  124 , and parallel to the direction Z 2  of the short side lines of the envelope S 1  and S 2 . In an implementation, the high-voltage area HV may include a high-voltage excursion HVe that crosses the line O to extend toward in the low-voltage area LV along the direction Z 1  of the long side lines of the envelope S 1  and S 2 , and the low-voltage area LV may include a low-voltage excursion LVe aligned toward the opposite side of the high-voltage excursion HVe to be elongated along the direction Z 2  of the short side lines while avoiding the high-voltage excursion HVe. For example, the high-voltage excursion HVe and the low-voltage excursion LVe may be arranged at positions opposite to each other along the direction Z 2  of the short side lines of the envelope S 1  and S 2 , the low-voltage excursion LVe may be arranged at one position relatively close to the first and second fuse terminals  123  and  124  along the direction Z 2  of the short side lines of the envelope S 1  and S 2 , and the high-voltage excursion HVe may be arranged at another position relatively far from the first and second fuse terminals  123  and  124 . In addition, the high-voltage excursion HVe and the low-voltage excursion LVe may extend along the direction Z 1  of the long side lines and the direction Z 2  of the short side lines of the envelope S 1  and S 2 , respectively, to be elongated along the respective directions. That is, the high-voltage excursion HVe may be elongated along the direction Z 1  of the long side lines rather than the direction Z 2  of the short side lines to extend toward the low-voltage area LV, and the low-voltage excursion LVe may be elongated along the direction Z 2  of the short side lines rather than the direction Z 1  of the long side lines while avoiding the high-voltage excursion HVe. 
     In an implementation, the high-voltage area HV and the low-voltage area LV may be asymmetrical with respect to the line O, and thus, compatibility of a battery management system (BMS) with the 64-cell structure in which 64 battery cells  10  are configured and the 72-cell structure in which 72 battery cells  10  are configured may be provided. In an implementation, the battery management system (BMS) has a pin-map corresponding to the positions of the battery cells  10  and the fuse box (not shown), and in the 64-cell structure, the fuse box (not shown) is located between a pin of number  32  (the thirty-second battery cell along the electrical connection route of the battery cells  10 ) and a pin of number  33  (the thirty-third battery cell along the electrical connection route of the battery cells  10 ). In an implementation, in the 64-cell structure, the fuse box may be located a central position, e.g., between the thirty-second battery cell  10  and the thirty-third battery cell  10  along the electrical connection route of the battery cells  10 . 
     In an implementation, like the 64-cell structure, the 72-cell structure shown in  FIG. 5  may be implemented such that the fuse box is located between the pin of number  32  (the thirty-second battery along the electrical connection route of the battery cells  10 ) and pin of number  33  (the thirty-third battery cell along the electrical connection route of the battery cells  10 ), and thus, the battery management system (BMS) may be utilized in common in the 64-cell structure and the 72-cell structure. In an implementation, the battery management system (BMS) having a specific pin-map may be applied in common to the 64-cell structure and the 72-cell structure. 
     In the 72-cell structure designed to have the compatibility of the battery management system (BMS) with the 64-cell structure according to an embodiment, the number of the bus bars  120  in the high-voltage area HV (or the number of the battery cells  10  in the high-voltage area HV) may be greater than the number of the bus bars  120  in the low-voltage area LV (or the number of the battery cells  10  in the low-voltage area LV), based on the fuse box (not shown) as a boundary along the electrical connection route of the battery cells  10 , and the high-voltage area HV including the number of the bus bars  120  greater than that of the low-voltage area LV may include the high-voltage excursion HVe that extends toward the low-voltage area LV, while the low-voltage area LV may include the low-voltage excursion LVe to avoid the high-voltage excursion HVe. 
     Referring to  FIG. 7 , the battery cells  10  may be assembled in the cell holder  110 . In an implementation, the cell holder  110  may have one side in which the battery cells  10  are assembled, and the other side on which hollow protrusions  115  connected to the cooling flow paths F between the battery cells  10  adjacent to each other are formed. As described below, the hollow protrusion  115  may extend to penetrate the circuit board  130  on the other side of the cell holder  110 . Hereinafter, the cell holder  110  will be described in more detail. 
     The cell holder  110  may include an upper holder  110   a  into which the upper end portions  10   a  of the battery cells  10  are inserted and a lower holder  110   b  into which the lower end portions  10   b  of the battery cells  10  are inserted. Except for the upper end portions  10   a  and the lower end portions  10   b  of the battery cells  10  inserted into the upper holder  110   a  and the lower holder  110   b , respectively, central portions of the battery cells  10  in the height direction may be exposed between the upper holder  110   a  and the lower holder  110   b . The cooling flow paths F may be formed between the battery cells  10  adjacent to each other, and the central portions of the battery cells  10  exposed between the upper holder  110   a  and the lower holder  110   b  may be directly exposed to a cooling medium flowing through the cooling flow paths F and thus, may be cooled. In an implementation, the cooling medium may be low temperature air introduced from the outside of the battery pack. In an implementation, the cooling medium may be a cooling medium in a gas state other than air, e.g., a refrigerant gas. 
     Assembly ribs  111  into which the upper end portions  10   a  of the battery cells  10  and the lower end portions  10   b  of the battery cells  10  are inserted may be formed in the upper holder  110   a  and the lower holder  110   b , respectively, and the assembly rib  111  may restrict an assembly position of the battery cell  10  while surrounding the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 . The assembly rib  111  may protrude from a plate-shaped main body of the cell holder  110  toward the battery cell  10  in the height direction of the battery cell  10 , and may support the battery cell  10  while surrounding the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 . 
     Terminal holes  112  that expose the first and second electrodes  11  and  12  of the battery cells  10  may be formed in the cell holder  110 . The first and second electrodes  11  and  12  of the battery cell  10  exposed by or through the terminal hole  112  may be electrically connected to the adjacent battery cells  10  through the bus bars  120 . In an implementation, the terminal hole  112  may be formed in a region surrounded by the assembly rib  111  into which the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  is inserted. 
     As illustrated in  FIG. 3 , according to an embodiment, the vent portion  13  may be formed at 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 portion  13  may be formed along the edge surrounding the second electrode  12  formed at the one end portion of the battery cell  10 . Referring to  FIG. 7 , the terminal hole  112  may have a sufficient size (e.g., diameter) to expose the second electrode  12  of the battery cell  10  and the vent portion  13  along the edge portion of the one end portion of the battery cell  10 . In an implementation, the pair of adjacent battery cells  10  may be arranged in the pattern in which one of the pair of adjacent battery cells  10  is inverted in the height direction. Accordingly, the vent portion  13  of the battery cell  10  may be formed at the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  according to a position of the battery cell  10 , and in this case, the terminal holes  112  formed at the upper and lower holders  110   a  and  110   b  may have a sufficient size (e.g., diameter) to expose the vent portions  13  formed at the upper end portions  10   a  and the lower end portions  10   b  of the battery cells  10 , respectively. 
     Referring to  FIG. 7 , the exhaust gas discharged through the vent portions  13  of the battery cells  10  may flow along the exhaust gas path formed on the cell holder  110  through the terminal holes  112  of the cell holder  110 , and may be discharged to the outside of the battery pack through an exhaust hole DH at one side of the cell holder  110 . In an implementation, the exhaust hole DH may be formed at one side of the cell holder  110 , and the exhaust hole DH may be fluidly connected to the vent portions  13  of the plurality of battery cells  10  to collect the exhaust gas discharged from the vent portions  13  and discharge the collected exhaust gas to the outside of the battery pack. In an implementation, the exhaust hole DH may be formed at an edge of the cell holder  110 , and may be formed at one edge of the cell holder  110  along the direction of long side lines of the cell holder  110 . 
     The direction of the long side lines of the cell holder  110  may correspond to the direction Z 1  of the long side lines of the envelope S 1  and S 2  (refer to  FIG. 4 ) that surrounds the group of the battery cells  10  that constitutes the battery pack. In an implementation, supposing that the group of battery cells  10  that constitutes the battery pack is surrounded by the rectangular envelope S 1  and S 2  (see  FIG. 4 ) consisting of the pair of long side lines S 1  and the pair of short side lines S 2  that extend to linearly surround the circumference of the group of battery cells  10 , the direction Z 1  of the long side lines of the envelope S 1  and S 2  may correspond to the direction of the long side lines of the cell holder  110 . 
     Referring to  FIG. 7 , according to an embodiment, a plurality of battery cells  10  may be arranged in the pattern in which one of the pair of adjacent battery cells  10  is inverted in the height direction of the battery cells  10 . In an implementation, the plurality of battery cells  10  may include a first group and a second group of the battery cells  10 , such that the battery cells  10  of the first group are vertically inverse to the battery cells  10  of the second group. In an implementation, the battery cells  10  of the first group may have the vent portions  13  at the upper end portions  10   a  thereof, and the battery cells  10  of the second group may have the vent portions  13  at the lower end portions  10   b  thereof. 
     Referring to  FIGS. 7 and 8 , the cell holder  110  may include the upper holder  110   a  in which the upper end portions  10   a  of the battery cells  10  of the first group are assembled, and the lower holder  110   b  in which the lower end portions  10   b  of the battery cells  10  of the second group are assembled. In an implementation, the upper holder  110   a  and the lower holder  110   b  may be assembled with each other with the battery cells  10  of the first and second groups therebetween, thereby providing an accommodation space for the battery cells  10  of the first and second groups. In this case, an upper exhaust hole DHa, through which the exhaust gas discharged from the upper end portions  10   a  (e.g., the vent portion  13 ) of the battery cells  10  of the first group  10  is collected, may be formed at an upper side of the upper holder  110   a , and a lower exhaust hole DHb, through which the exhaust gas discharged from the lower end portions  10   b  (e.g., the vent portion  13 ) of the battery cells  10  of the second group  10  is collected, may be formed at a lower side of the lower holder  110   b . In an implementation, the exhaust gas path connecting the upper end portions  10   a  (e.g., the vent portion  13 ) of the battery cells  10  of the first group to the upper exhaust hole DHa may be on the upper side of the upper holder  110   a , and the exhaust gas path connecting the lower end portions  10   b  (e.g., the vent portion  13 ) of the battery cells  10  of the second group to the lower exhaust hole DHb may be formed on the lower side of the lower holder  110   b . Referring to  FIG. 1 , an upper separation member  140   a  and a lower separation member  140   b  that form the respective exhaust gas paths may be arranged on the upper side of the upper holder  110   a  and the lower side of the lower holder  110   b , and the exhaust gas paths may be formed between the upper side of the upper holder  110   a  and the upper separation member  140   a  and between the lower side of the lower holder  110   b  and the lower separation member  140   b , respectively. In an implementation, the exhaust gas paths may be formed between the upper side of the upper holder  110   a  and the blocking region  144  of the upper separation member  140   a  and between the lower side of the lower holder  110   b  and the blocking region  144  of the lower separation member  140   b . The upper separation member  140   a , the lower separation member  140   b , and the blocking region  144  will be described in more detail later. 
     Referring to  FIGS. 7 and 8 , the upper exhaust hole DHa and the lower exhaust hole DHb may be formed at edge positions of the upper holder  110   a  and the lower holder  110   b  that correspond to each other, e.g., at edge positions along the direction of the long side lines the cell holder  110 . In addition, an exhaust duct DD may be formed at the edge positions of the upper holder  110   a  and the lower holder  110   b  at which the upper exhaust hole DHa and the lower exhaust hole DHb are formed, while continuously extending in the height direction. The exhaust duct DD may be continuously formed through the upper holder  110   a  and the lower holder  110   b  in the height direction, more specifically, as the upper holder  110   a  and the lower holder  110   b  are assembled, a portion of the exhaust duct DD formed in the upper holder  110   a  and another portion of the exhaust duct DD formed in the lower holder  110   b  may be connected to each other, and thus, the complete exhaust duct DD may be formed in a tube shape. In an implementation, the exhaust duct DD may include the portion formed in the upper holder  110   a  and another portion formed in the lower holder  110   b  such that the exhaust duct DD is divided into the two portions formed in the upper holder  110   a  and the lower holder  110   b , respectively. For reference, throughout the present specification, the term “height direction” may refer to the height direction of the battery cell  10 , and may refer to a length direction of the battery cell  10 , e.g., the lengthwise direction of the longest dimension (e.g., long axis) of the battery cell  10 . 
     The exhaust duct DD may form a space separated from the accommodation space for the battery cells  10  formed by assembling the upper holder  110   a  and the lower holder  110   b , and may have a sealed structure except for portions connected to the upper exhaust hole DHa and the lower exhaust hole DHb through which the exhaust gas is introduced, and a portion connected to an exhaust pipe DP through which the exhaust gas is discharged to the outside of the cell holder  110 . 
     The upper exhaust hole DHa and a lower exhaust hole DHb may be connected to both ends of the exhaust duct DD in the height direction. In an implementation, the exhaust pipe DP may be connected to a location between both ends of the exhaust duct DD in the 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 the height direction, may be connected to the upper exhaust hole DHa and the lower exhaust hole DHb at both ends, respectively, and may be connected to, at the location between both ends in the height direction, the exhaust pipe DP for collecting the exhaust gas discharged from the upper exhaust hole DHa and the lower exhaust hole DHb and discharging the collected exhaust 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 location between the upper side and the lower side of the cell holder  110  in the height direction, may protrude from the location between the upper side and the lower side of the cell holder  110  toward the outside, and for example, may protrude from an outer surface of the cell holder  110  toward the outside along the direction of the long side line of the cell holder  110 . In an implementation, the exhaust pipe DP may be formed at a location between the upper side of the upper holder  110   a  and the lower side of the lower holder  110   b , and may be formed at a location of the upper holder  110   a , the location being closer to the upper side of the upper holder  110   a  than the lower side, or at a location of the lower holder  110   b , the location being closer to the lower side of the lower holder  110   b  than the upper side. In an implementation, the exhaust pipe DP may protrude from the upper holder  110   a  toward the outside, and may be formed at a location between the upper side of the upper holder  110   a  and the lower side of the lower holder  110   b , the location being closer to the upper side of the upper holder than the lower side of the lower holder  110   b . As illustrated in  FIG. 1 , according to an embodiment, the circuit board  130  may arranged on the upper holder  110   a , the circuit board  130  may be interposed between the upper side of the upper holder  110   a  and the upper separation member  140   a  which form the exhaust gas path therebetween, and may generate a flow resistance on the exhaust gas path, and the exhaust pipe DP may be formed at a location between the upper side of the upper holder  110   a  and the lower side of the lower holder  110   b , the location being closer to the upper side of the upper holder  110   a  than the lower side of the lower holder  110   b , to allow the flow resistance to be balanced between the exhaust gas path of the upper holder  110   a  and the exhaust gas path of the lower holder  110   b . As illustrated in  FIG. 1 , in the case where the circuit board  130  is arranged on the upper holder  110   a  and the upper exhaust hole DHa is formed at the upper side of the upper holder  110   a , the upper exhaust hole DHa may be formed at a location deviated from the circuit board  130 , and accordingly, the flow of the exhaust gas introduced into the upper exhaust hole DHa may not be disturbed by the circuit board  130 . The circuit board  130  may be arranged on the upper holder  110   a  and may overlap a partial area of the upper holder  110   a  rather than the entire area, and thus, the upper exhaust hole DHa may be formed at an area of the upper holder  110   a  that is not covered by the circuit board  130  to prevent the upper exhaust hole DHa from being blocked by the circuit board  130 . 
     Referring to  FIG. 8 , the exhaust pipe DP may form an end of the exhaust gas path through which the exhaust gas discharged from the battery cells  10  of the first and second groups accommodated in the cell holder  110  is discharged to the outside of the cell holder  110 . Through the present specification, the upper exhaust hole DHa, the lower exhaust hole DHb, and the exhaust duct DD are described as separate components, but this is for convenience of understanding, and both ends of the exhaust duct DD that continuously extends through the upper holder  110   a  and the lower holder  110   b  in the 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 in a single pipe shape that continuously extends in the height direction. 
     Referring to  FIG. 7 , the hollow protrusions  115  that form the cooling flow paths F may be formed at, in, or on the cell holder  110 . The hollow protrusion  115  may include a central hollow portion forming the cooling flow path F and a wall body  115   a  surrounding the central hollow portion. In an implementation, the hollow protrusion  115  may include a circular wall body  115   a  surrounding the central hollow portion. For example, the circular wall body  115   a  of the hollow protrusion  115  may refer to a shape of an outer circumference of the hollow protrusion  115 , and an inner circumference of the hollow protrusion  115  may have a shape other than a circular shape. In an implementation, the circular wall body  115   a  of the hollow protrusion  115  may have the outer circumference in a circular shape and the inner circumference in a shape of a triangle with rounded edges. In an implementation, the hollow protrusion  115  may include the wall body  115   a  that surrounds the central hollow portion and has the outer circumference in any one of various shapes including a polygon, an ellipse, and a hexagon, and the inner circumference in any one of various shapes including a circle, an ellipse, a polygon, and a combination thereof. 
     The hollow protrusion  115  may protrude from the plate-shaped main body of the cell holder  110 , in a direction away from the battery cells  10 . In an implementation, the hollow protrusions  115  may extend the cooling flow paths F formed between the adjacent battery cells  10  to the outside of the battery cells  10  in the height direction of the battery cells  10  and may form the cooling flow paths F each surrounded by the wall body  115   a . In an implementation, positions of the hollow protrusions  115  formed along the plate-shaped main body of the cell holder  110  may correspond to the positions of the cooling flow paths F formed between the battery cells  10 , the positions of the hollow protrusions  115  may correspond to the positions of the cooling flow paths F described with reference to  FIG. 4 , and the positions of the cooling flow paths F in  FIG. 4  may refer to the positions of the hollow protrusions  115 . 
     Referring to  FIG. 1 , the hollow protrusion  115  may pass through the circuit board  130  and the separation member  140  that are arranged on the upper holder  110   a  sequentially in the height direction of the battery cells  10 , which in case, the hollow protrusion  115  may form the cooling flow path F that extends across the battery pack to pass through substantially the entire battery pack in the height direction of the battery cells  10 . More specifically, the hollow protrusion  115  of the upper holder  110   a  may pass through the circuit board  130  and the upper separation member  140   a  that are arranged on the upper holder  110   a  sequentially in the height direction of the battery cells  10 , and the hollow protrusion  115  of the lower holder  110   b  may pass through the lower separation member  140   b  that is arranged under the lower holder  110   b  in the height direction of the battery cells  10 . Open regions  135  and  145  into which the hollow protrusions  115  are inserted may be formed at the circuit board  130  and the separation member  140 . The open regions  135  and  145  of the circuit board  130  and the separation member  140  may be formed such that positions in the circuit board  130  and the separation member  140  corresponding to the hollow protrusions  115  are opened. The open regions  135  and  145  of the circuit board  130  and the separation member  140  will be described in more detail below. 
     Referring to  FIGS. 1 and 2 , the bus bars  120  may be arranged on the cell holder  110 . In an implementation, the upper bus bars  120   a  and the lower bus bars  120   b  may be arranged on the upper holder  110   a  and the lower holder  110   b , respectively, and the bus bars  120  may be alternately arranged on the upper holder  110   a  and the lower holder  110   b  to connect the pair of battery cells  10  adjacent to each other along the electrical connection route. As described above, each of the bus bars  120  may electrically connect the pair of battery cells  10  along the electrical connection route, and the plurality of bus bars  120  may be arranged along the electrical connection route 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 thereof, a central protruding connection piece  120   c  that connects the coupling pieces  120   a  to each other, and bent portions  120   b  that connect the coupling pieces  120   a  to the central protruding connection piece  120   c  in a bent shape. The coupling pieces  120   a  at both ends of the bus bar  120  may be coupled to the upper end portions  10   a  or the lower end portions  10   b  of the pair of adjacent battery cells  10 , and may be coupled to the upper end portions  10   a  or the lower end portions  10   b  of the pair of adjacent battery cells  10  exposed by the terminal holes  112  of the cell holder  110  to connect the first and second electrodes  11  and  12  of the pair of adjacent battery cells  10  in series or in parallel. In an implementation, the coupling pieces  120   a  at both ends of the bus bar  120  may be coupled to the pair of adjacent battery cells  10  by, e.g., welding. 
     The bent portions  120   b  may connect the coupling pieces  120   a  at both ends to the central protruding connection piece  120   c , may have the bent shape, and may support the protruding connection piece  120   c  at a level spaced apart from the battery cells  10  in the height direction of the battery cells  10 , thereby preventing electrical interference between the protruding connection piece  120   c  and the battery cells  10  and pressing the coupling pieces  120   a  at both ends toward the upper end portions  10   a  or the lower end portions  10   b  of the battery cells  10  while being elastically deformed by the protruding connection piece  120   c  pressed toward the battery cells  10  by the cell holder  110  (e.g., the hollow protrusions  115 ). This will be described in more detail below. 
     The protruding connection piece  120   c  may correspond to a flat plate-shaped member that is farthest from or distal to the battery cells  10  in the bus bar  120  in the height direction of the battery cells  10 , and may be arranged on a virtual plane that is farthest from the battery cell  10  in the bus bar  120 . As illustrated in  FIG. 10 , the protruding connection piece  120   c  may be exposed from or on the circuit board  130  arranged on the cell holder  110 . In an implementation, the entire protruding connection piece  120   c  may be exposed from or on the circuit board  130  (e.g., the 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 between the hollow protrusions  115  of the cell holder  110 . In an implementation, the bus bar  120  may extend between a pair of hollow protrusions  115 , e.g., the protruding connection piece  120   c  of the bus bar  120  may be between the pair of hollow protrusions  115 . The (e.g., lengthwise) extending direction of the bus bar  120  and the direction in which the pair of hollow protrusions  115  face each other may cross each other, e.g., may vertically cross each other. 
     In an implementation, the bus bar  120  may extend across or connect a pair of battery cells  10  of which circumferences are adjacent to each other and may electrically connect the pair of adjacent battery cells  10  to each other. In an implementation, the cooling flow paths F and the hollow protrusions  115  may be between the pair of adjacent battery cells  10  connected to each other by the bus bar  120  and another pair of battery cells  10  adjacent to each other in a direction intersecting the bus bar  120 . In an implementation, the bus bar  120  may extend between the pair of hollow protrusions  115  facing each other in the direction intersecting the (e.g., lengthwise direction of the) bus bar  120 . 
     A pair of locking steps  115   p  into which the bus bar  120  is inserted to be assembled may be formed at the pair of hollow protrusions  115  facing each other with the bus bar  120  therebetween, e.g., at the wall bodies  115   a  of the pair of hollow protrusions  115  facing each other. In an implementation, the locking steps  115   p  may be formed on the wall bodies  115   a  of the hollow protrusions  115 , and the bus bar  120 , e.g., the protruding connection piece  120   c  of the bus bar  120 , may be inserted into (e.g., between) the locking steps  115   p  having a wedge shape. The bus bar  120  that is inserted into the locking steps  115   p  and assembled may be effectively prevented from being separated from the battery cell  10 . The pair of locking steps  115   p  may be formed at the pair of hollow protrusions  115  facing each other with the bus bar  120  therebetween, may extend from the wall bodies  115   a  of the hollow protrusions  115  to the protruding connection piece  120   c  of the bus bar  120  to press the protruding 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 portions  10   a  or the lower end portions  10   b  of the battery cells  10  through elastic deformation of the bent portions  120   b  connected to the protruding connection piece  120   c . Accordingly, the bus bar  120  and the battery cells  10  may be firmly coupled to each other. 
     Referring to  FIG. 9 , mold holes  110 ′ may be formed at positions in the cell holder  110  that correspond to the pair of locking steps  115   p . In an implementation, the hollow protrusion  115  having the locking step  115   p  may protrude from the plate-shaped main body of the cell holder  110 , and the mold hole  110 ′ may be formed at a position in the main body of the cell holder  110  that corresponds to the locking step  115   p , to pass through the main body of the cell holder  110 . The mold hole  110 ′ may be formed at a position in which an upper mold and a lower mold are coupled to each other when the cell holder  110  in which the locking steps  115   p  are formed is molded, and a portion in which a molten resin is not filled due to a coupling mechanism between the upper mold and the lower mold may remain as the mold hole  110 ′. In an implementation, the cell holder  110  having the locking steps  115   p  formed therein may be easily separated from a mold in which the upper mold and the lower mold are combined, and figures of the locking steps  115   p  of the cell holder  110  may be prevented from being damaged during the separation. 
     Referring to  FIG. 9 , the protruding connection piece  120   c  of the bus bar  120  may include position alignment holes  120   g  for position alignment with the cell holder  110 . In an implementation, position alignment pins  110   g  to be inserted into the position alignment holes  120   g  of the protruding connection piece  120   c  may be between the pair of hollow protrusions  115  with the protruding connection piece  120   c  having the position alignment holes  120   g  formed therein, therebetween, e.g., on the main body of the cell holder  110  having the pair of hollow protrusions  115 . In this case, the position alignment holes  120   g  of the protruding connection piece  120   c  may be inserted onto the position alignment pins  110   g  of the cell holder  110 , and accordingly, the bus bar  120  may be assembled in a correct position on the cell holder  110 . A pair of position alignment pins  110   g  may be arranged along a direction in which the bus bar  120  extends. In this case, the direction in which the bus bar  120  extends and the pair of position alignment pins  110   g  are arranged, may intersect, e.g., may vertically intersect, a direction in which the pair of hollow protrusions  115  having the bus bar  120  therebetween face each other. In an implementation, the position alignment holes  120   g  and the position alignment pins  110   g  may be formed on the bus bar  120  and the cell holder  110  in which the bus bar  120  is assembled, respectively. In an implementation, the position alignment holes  120   g  and the position alignment pins  110   g  may be formed on the cell holder  110  and the bus bar  120 , respectively, in a manner that the position alignment holes  120   g  and the position alignment pins  110   g  are formed at positions corresponding to each other. 
     Referring to  FIGS. 10 and 11 , the coupling pieces  120   a  at both ends of the bus bar  120  may be exposed from or at the circuit board  130  arranged on the bus bars  120 , e.g., may be exposed from or through the circuit board  130  (the solid portion of the circuit board  130 ) through filling holes FH of the circuit board  130 . In an implementation, the filling hole FH may expose at least a portion of the coupling piece  120   a  of the bus bar  120 . In an implementation, the coupling piece  120   a  of the bus bar  120  coupled to the upper end portion  10   a  of the battery cell  10  may be exposed through the filling hole FH of the circuit board  130 , and the potting resin PR filling the filling hole FH may cover and protect a coupling portion or structure 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 help protect the coupling structure between the battery cells  10  and the coupling piece  120   a  of the bus bars  20  from harmful (e.g., external) elements, e.g., oxygen or moisture, and may help protect the coupling structure (between different heterogeneous materials formed by welding) from galvanic corrosion. In an implementation, the filling hole FH may be at the central portion of the upper end portion  10   a  of each battery cell  10  to expose the bus bar  120  (e.g., the coupling pieces  120   a  at both ends of the bus bar  120 ) coupled to the central portion of the upper end portion  10   a  of the battery cell  10 . 
     Referring to  FIGS. 10 and 12 , the circuit board  130  may be on the bus bars  120 . The escape holes  132   a  for exposing portions of the bus bars  120  may be in the circuit board  130 . In an implementation, the escape hole  132   a  may entirely expose the central protruding connection piece  120   c  of the bus bar  120 . In an implementation, in the case where the escape hole  132   a  entirely exposes the protruding connection pieces  120   c , the entire protruding connection piece  120   c  may be entirely exposed on the circuit board  130  through the escape hole  132   a . In an implementation, the protruding connection piece  120   c  may not overlap the circuit board  130  (the solid portion of the circuit board  130 ), and may not overlap the circuit board  130  (the solid portion of the circuit board  130 ) even at least partially. 
     Referring to  FIG. 12 , the escape hole  132   a  may accommodate the protruding connection piece  120   c , and the protruding connection piece  120   c  may be arranged at a location between a lower side  130   a  and a upper side  130   b  of the circuit board  130  in the height direction. Here, the lower side  130   a  of the circuit board  130  may refer to a surface of the circuit board  130  that faces the battery cell  10  and the upper side  130   b  of the circuit board  130  may refer to a surface opposite to the lower side  130   a . In an implementation, the coupling pieces  120   a  at both ends of the bus bar  120  may overlap the lower side  130   a  of the circuit board  130  (the solid portion of the circuit board  130 ), and the protruding coupling piece  120   c  connected from the coupling pieces  120   a  via the bent portions  120   b  may not overlap the lower side  130   a  of the circuit board  130  (the solid portion of the circuit board  130 ), may be accommodated in the escape hole  132   a  at a location between the lower side  130   a  and the upper side  130   b  of the circuit board  130  in the height direction, and thus may not form an additional thickness with respect to a thickness of the circuit board  130  in the height direction. 
     The protruding connection piece  120   c  of the bus bar  120  and the circuit board  130  (e.g., the solid portion of the circuit board  130 ) may not overlap each other due to the escape holes  132   a . Accordingly, the circuit board  130  may be arranged at a low position close to the battery cell  10 , a spacing distance q between the circuit board  130  and the battery cell  10  in the height direction may be reduced, thus a length of a connection member  125  that forms a voltage measurement line between the circuit board  130  and the battery cell  10  may be reduced, e.g., firm junctions may be formed at the circuit board  130  and the battery cell  10  by wire bonding or ribbon bonding that bonds, by ultrasonic welding, one end portion and the other end portion of the connection member  125  to the circuit board  130  and the battery cell  10 , respectively, and welding defects of the ultrasonic welding due to relative vibrations between the circuit board  130  and the battery cell  10  may be prevented. 
     In an implementation, the protruding connection piece  120   c  of the bus bar  120  and the circuit board  130  (e.g., the solid portion of the circuit board  130 ) may not overlap each other in the height direction due to the escape holes  132   a . Accordingly, the circuit board  130  may be arranged at a low position, e.g., close to the battery cell  10 , and the height of the entire battery pack may be reduced, thus a thinner battery pack may be provided. 
     Referring to  FIG. 10 , the bus bar  120  may extend between the pair of hollow protrusions  115 , and the protruding connection piece  120   c  of the bus bar  120  may be arranged between the pair of hollow protrusions  115 . In this case, the escape hole  132   a  may be formed at a position in the circuit board  130  corresponding to the protruding connection piece  120   c , e.g., at a position between the pair of hollow protrusions  115 . The escape hole  132   a  may be a portion of a bus opening region  132   b  that exposes the pair of hollow protrusion portions  115  that face each other with the bus bar  120  therebetween and a pair of cooling flow paths F as well as the protruding connection pieces  120   c  of the bus bar  120 . In an implementation, the circuit board  130  may include the bus opening region  132   b  connected to or continuous with the escape hole  132   a  that exposes the protruding connection piece  120   c  of the bus bar  120  to be formed in a single, continuous hole shape, for exposing the hollow protrusions  115  and the protruding connection piece  120   c  of the bus bar  120  together. 
     The bus opening region  132   b  may have the single hole shape in the circuit board  130  to expose a portion of the bus bar  120 , e.g., the protruding connection piece  120   c  of the bus bar  120 , together with exposing the pair of hollow protrusions  115  (or the 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 protruding connection piece  120   c  of the bus bar  120  may refer to a region or a part of the bus opening region  132   b  having the single hole shape, e.g., excluding a region through which the hollow protrusions  115  pass. 
     If one hole for exposing the protruding connection piece  120   c  of the bus bar  120  and two holes for exposing the cooling flow paths F adjacent to each other were to be separately formed with narrow portions therebetween, e.g., if three holes were separately formed with narrow portions therebetween, the circuit board  130  could be damaged. In an implementation, the protruding connection piece  120   c  of the bus bar  120  and the pair of cooling flow paths F adjacent to each other may be exposed through the bus opening region  132   b  having the single hole shape. Accordingly, a structure of the circuit board  130  may be simplified and a risk of damage due to insufficient rigidity of the circuit board  130  may be reduced. 
     The bus opening region  132   b  may expose the pair of cooling flow paths F (or the hollow protrusions  115 ) facing each other with the bus bar  120  therebetween. As will be described below, the bus opening region  132   b  may have the single hole shape together with a connection opening region  132   c  that exposes a pair of cooling flow paths F (or the hollow protrusions  115 ) facing each other with the connection member  125  therebetween. The bus opening region  132   b  and the connection opening region  132   c  may form a second opening region  132  having a single hole shape. In an implementation, the cooling flow paths F (or the hollow protrusions  115 ) exposed through the second opening region  132  may include the pair of cooling flow paths F (or first and second hollow protrusions  1151  and  1152 ) facing each other with the bus bar  120  therebetween, and the pair of cooling flow paths F (or the first and third hollow protrusions  1151  and  1153 ) facing each other with the connection member  125  therebetween, and may include a total of three cooling flow paths F including the cooling flow path F (or the first hollow protrusion  1151 ) arranged between the bus bar  120  and the connection member  125 . In an implementation, the hollow protrusions  115  exposed through the second opening region  132  may include the three hollow protrusions  115  including the first hollow protrusion  1151  between the bus bar  120  and the connection member  125 , the second hollow protrusion  1152  facing the first hollow protrusion  1151  with the bus bar  120  therebetween, and the third hollow protrusion  1153  facing the first hollow protrusion  1151  with the connection member  125  therebetween. 
     In an implementation, the escape hole  132   a  that exposes the protruding connection piece  120   c  of the bus bar  120  may be a portion of the second opening region  132 , and the protruding connection piece  120   c  of the bus bar  120  may be exposed through the second opening region  132 . In an implementation, the protruding connection pieces  120   c  may be entirely exposed from the circuit board  130  (the solid portion of the circuit board  130 ) through the second opening region  132 . 
     Referring to  FIG. 10 , the circuit board  130  may include the open regions  135  having a hole shape through which the cooling flow paths F (or the hollow protrusion  115 ) pass. The cooling flow path F may pass through the open region  135  of the circuit board  130  and may extend across the circuit board  130 , e.g., the hollow protrusion  115  of the cell holder  110  may be inserted into or through the open region  135  of the circuit board  130  to form the cooling flow path F that passes through the open region  135  of the circuit board  130 . In an implementation, the open regions  135  of the circuit board  130  may be at positions corresponding to the hollow protrusions  115  of the cell holder  110  and may have a shape corresponding to the hollow protrusion  115  of the cell holder  110 . In an implementation, the open region  135  (e.g., a first opening region  131 ) of the circuit board  130  may have a circular shape corresponding to the hollow protrusion  115  including the circular wall body  115   a . In an implementation, the open region  135  (e.g., the first opening region  131 ) of the circuit board  130  may have various shapes corresponding to the hollow protrusion  115 , e.g., in an elliptical shape or a hexagonal shape. 
     As will be described below, the first opening region  131  of the open region  135  may surround the outer circumference of some hollow protrusions  115 , and the second opening region  132  may surround at least a portion of the outer circumference of some other hollow protrusions  115 . In an implementation, the second opening region  132  may expose two or more hollow protrusions  115  adjacent to each other together, and surround at least a portion of the outer circumference of each of the two or more hollow protrusions  115  together. 
     The open region  135  of the circuit board  130  may include the first opening regions  131  accommodating some cooling flow paths F (or the hollow protrusion  115 ) individually and the second opening regions  132  commonly accommodating two or more other cooling flow paths F adjacent to each other. In an implementation, the second opening region  132  may include the connection opening region  132   c  and the bus opening region  132   b . The connection opening region  132   c  may commonly accommodate the pair of cooling flow paths F facing each other with the connection member  125  therebetween. The connection member  125  will be described in more detail below. The bus opening region  132   b  may commonly accommodate the pair of cooling flow paths F facing each other with the bus bar  120  therebetween. In an implementation, the connection opening region  132   c  and the bus opening region  132   b  may not be independent holes separated from each other, and may be continuously connected to each other to form the second opening region  132  in a single hole configuration. The number of cooling flow paths F in the pair of cooling flow paths F exposed through the connection opening region  132   c  and the pair of cooling flow paths F exposed through the bus opening region  132   b  may be 3 rather than 4 as one of the cooling flow paths F is included in both pairs. In an implementation, the cooling flow path F at a position where the connection opening region  132   c  and the bus opening region  132   b  overlap each other, e.g., the cooling flow path F (or the first hollow protrusion  1151 ) interposed between the connection member  125  and the bus bar  120  may be included in both the pair of cooling flow paths F (or the first and second hollow protrusions  1151  and  1152 ) exposed through the bus opening region  132   b  and the pair of cooling flow paths F (or the first and third hollow protrusions  1151  and  1153 ) exposed through the connection opening region  132   c . In an implementation, the hollow protrusions  115  (or the cooling flow paths F) exposed through the second opening region  132  may include a total of three hollow protrusions  115 , which are the first hollow protrusion  1151  between the bus bar  120  and the connection member  125 , the second hollow protrusion  1152  facing the first hollow protrusion  1151  with the bus bar  120  therebetween, and the third hollow protrusion  1153  facing the first hollow protrusion with the connection member  125  therebetween. 
     Each of the first opening regions  131  may be a hole formed for the cooling flow paths F individually, and may expose the cooling flow path F from, at, or through the circuit board  130 . Unlike the first opening region  131 , the second opening region  132  may have a single hole shape commonly accommodating two or more cooling flow paths F adjacent to each other, and may expose the two or more neighboring cooling flow paths F together from, at, or through the circuit board  130 . 
     The connection opening region  132   c  of the second opening region  132  may expose a portion of the upper end portions  10   a  of the battery cells  10  together with the pair of cooling flow paths F adjacent to each other (the pair of cooling flow paths F facing each other with the connection member  125  therebetween). In an implementation, the connection members  125  may be connected to the upper end portions  10   a  of the battery cells  10  exposed through the connection opening region  132   c . In an implementation, the connection opening region  132   c  may expose a portion of the upper end portions  10   a  of the battery cells  10  together with the pair of adjacent cooling flow paths F. In the case where the connection opening region  132   c  exposes the portion of the upper end portions  10   a  of the battery cells  10 , one end of the connection 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 connection opening region  132   c , and the other end of the connection member  125  may be connected to the circuit board  130 , thus the voltage measurement line may be formed between the battery cell  10  and the circuit board  130 , and the connection opening region  132   c  may include a connection hole CH for allowing the connection members  125  to pass through the circuit board  130  and be connected. The connection hole CH will be described in more detail below. 
     Referring to  FIG. 10 , according to an embodiment, the connection opening region  132   c  of the second opening region  132  may expose portions of the upper end portions  10   a  of the battery cells  10  together with the pair of cooling flow paths F adjacent to each other (the pair of cooling flow paths F facing each other with the connection member  125  therebetween), and may function as the connection hole CH. In an implementation, the connection opening region  132   c  and the connection hole CH may have substantially the same configuration, e.g., the same hole in the circuit board  130 . In the present specification, for convenience of understanding, the connection opening region  132   c  and the connection hole CH will be assigned different reference numerals. 
     Portions of the upper end portions  10   a  of the battery cells  10  may be exposed through the connection hole CH (or the connection opening region  132   c ), and the connection member  125  may be connected to the upper end portion  10   a  of the battery cell  10  exposed from the circuit board  130 . In an implementation, the connection member  125  may include a conductive wire or a conductive ribbon having one end connected to the upper end portion  10   a  of the battery cell  10  and the other end connected to the circuit board  130 , and the connection member  125  may be formed by wire bonding that bonds the one end and the other end of the conductive wire to the upper end portion  10   a  of the battery cell  10  and the circuit board  130 , respectively, or ribbon bonding that bonds the one end and the other end of the conductive ribbon to the upper end portion  10   a  of the battery cell  10  and the circuit board  130 , respectively. In this case, in the wire bonding or the ribbon bonding, the conductive wire or the 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, the connection member  125  may be a pair of conductive wires that extend in parallel to connect the battery cell  10  to the circuit board  130 , and may firmly connect the battery cell  10  to the circuit board  130  by preparing for a situation where one of the conductive wires is disconnected due to insufficient mechanical strength. In the case where the connection member  125  is the conductive ribbon that has a mechanical strength greater than that of the conductive wire, the battery cell  10  and the circuit board  130  may be electrically connected to each other through a single conductive ribbon. For reference, the connection member  125  exemplarily illustrated in  FIG. 10  may be the conductive ribbon. 
     The connection hole CH may be in a region of the circuit board  130  that overlaps the pair of battery cells  10  adjacent to each other to expose the upper end portions  10   a  of the pair of adjacent battery cells  10  together. In an implementation, the connection hole CH may be in a region of the circuit board  130  that overlaps a portion of the pair of adjacent battery cells  10 , e.g., may be formed in a region that overlaps edge portions of the pair of battery cells  10 . In an implementation, two connection members  125  may be connected to the edge portions of the pair of battery cells  10  adjacent to each other exposed through the connection hole CH. 
     The edge portions of the upper end portions  10   a  of the pair of battery cells  10  exposed through the connection hole CH may form the first electrodes  11  having the same polarity. In an implementation, the pair of adjacent battery cells  10  exposed by the same connection hole CH may be arranged in a pattern in which one of the pair of adjacent battery cells  10  is inverted in the height direction of the battery cells  10 , however, the edge portions of the upper end portions  10   a  of the pair of adjacent battery cells  10  may form the first electrodes  11  having the same polarity regardless of the vertical arrangement of the battery cells  10 . As illustrated in  FIG. 3 , the can N forming the first electrode  11  may extend from the edge portion of the upper end portion  10   a  to the entire lower end portion  10   b , thus, regardless of the vertical arrangement of the battery cells  10 , both the edge portions of the upper end portions  10   a  and the edge portions of the lower end portions  10   b  of the adjacent battery cells  10  may form the first electrodes  11  having the same polarity. 
     As described above, the connection members  125  may be connected to the edge portions of the upper end portions  10   a  of the battery cells  10  exposed through the connection hole CH and may be connected to the first electrodes  11  of the battery cells  10 . Referring to  FIG. 2 , most of a plurality of connection members  125  may be connected to the first electrodes  11  of the battery cells  10  exposed through the connection holes CH, some of the connection members  125  may be connected to the first and second output terminals  121  and  122  or to the battery cells  10  connected to the first and second output terminals  121  and  122 , and thus 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 to the low-potential battery cell  10  having the lowest potential and the high-potential battery cell  10  having the highest potential, respectively, in a group of the battery cells  10  electrically connected to each other. In this case, one connection member  125   a  may be connected to the first electrode  11  at the upper end portion  10   a  of the low-potential battery cell  10 , while the other connection member  125   b  may be connected to the second electrode  12  formed at the upper end portion  10   a  of the high-potential battery cell  10 . In an implementation, among a group of the connection members  125  that constitutes the battery pack, the one connection member  125   a  may be connected to the first electrode  11  in the low-potential battery cell  10  connected to the first output terminal  121 , while the other connection member  125   b  may be connected to the second electrode  12  in the high-potential battery cell  10  connected to the second output terminal  122 , and the remaining connection members  125  may be connected to the first electrodes  11  at the edge portions of the upper end portions  10   a  of the battery cells  10  having middle potentials other than the low-potential battery cell  10  and the high-potential battery cell  10 . In an implementation, the connection members  125  may be connected to the second electrode  12  only for the high-potential battery cell  10  connected to the second output terminal  122 , and may be connected to the first electrodes  11  for the remaining battery cells  10 . 
     Referring to  FIG. 10 , the connection opening region  132   c  (or the connection hole CH) may have a sufficient area to expose the pair of cooling flow paths F adjacent to each other (the pair of cooling flow paths F facing each other with the connection member  125  therebetween), together with the edge portions of the pair of battery cells adjacent to each other 10. In an implementation, a direction in which the pair of battery cells  10  exposed through the connection opening region  132   c  face each other and a direction in which the pair of cooling flow paths F (the pair of cooling flow paths F facing each other with the connection member  125  therebetween) exposed through the connection opening region  132   c  may intersect each other, e.g., may vertically intersect each other. 
     If one connection hole CH for exposing the edge portions of the pair of battery cells  10  adjacent to each other and two open regions  135  for exposing the cooling flow paths F adjacent to each other were separately formed with narrow portions therebetween, e.g., if three holes were to be separately formed with narrow portions therebetween, the circuit board  130  could be damaged. In an implementation, the connection hole CH or the connection opening region  132   c  formed in a single hole shape may expose the edge portions of the pair of battery cells  10  adjacent to each other and the pair of cooling flow paths F adjacent to each other, and accordingly, the structure of the circuit board  130  may be simplified and a risk of damage due to insufficient rigidity of the circuit board  130  may be reduced. 
     The connections members  125  may be between the circuit board  130  and the upper end portions  10   a  of the battery cells  10  exposed through the connection opening region  132   c  or the connection hole CH, to electrically connect the circuit board  130  to the upper end portions  10   a  of the battery cells  10 , and the connection member  125  may transmit voltage information of the battery cell  10  to the circuit board  130 . In an implementation, the connection member  125  may electrically connect the upper end portion  10   a  of the battery cell  10  to a connection pad  133  of the circuit board  130 . The connection pads  133  of the circuit board  130  may be formed around the connection hole CH, e.g., a pair of connection pads  133  each electrically connected to each of the pair of adjacent battery cells  10  may be formed at positions facing each other around the connection hole CH. 
     In an implementation, the connection opening region  132   c  may form the second opening region  132  together with the bus opening region  132   b  that exposes the pair of cooling flow paths F facing each other with the bus bar  120  therebetween. In an implementation, the second opening region  132  may have a single hole shape, and may extend along an outer circumferential direction surrounding (e.g., partially surrounding) the filling hole FH. The second opening region  132  may include or accommodate the cooling flow path F (or the first hollow protrusion  1151 ) between the bus bar  120  and the connection member  125 , another cooling flow path F (or the second hollow protrusion  1152 ) arranged with the cooling flow path F (or the first hollow protrusion  1151 ) with the bus bar  120  therebetween, and yet another cooling flow path F (or the third hollow protrusion  1153 ) arranged with the cooling flow path F (or the first hollow protrusion  1151 ) and the connection member  125  therebetween, and may expose together the three different cooling flow paths F continuously arranged along the outer circumferential direction surrounding the filling hole FH. In an implementation, as illustrated in  FIG. 4 , six cooling flow paths F may be formed along the outer circumferential direction of one battery cell  10 , and three adjacent cooling flow paths F among the six cooling flow paths F may be exposed through the second opening region  132 . 
     Referring to  FIG. 10 , the second opening region  132  may accommodate the first hollow protrusion  1151  between the bus bar  120  and the connection member  125 , the second hollow protrusion  1152  facing the first hollow protrusion  1151  with the bus bar  120  therebetween, and the third hollow protrusion  1153  facing the first hollow protrusion  1151  with the connection member  125  therebetween, and overall may expose or accommodate three different hollow protrusions  115  continuously arranged along the outer circumferential direction surrounding the filling hole FH. 
     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 , e.g., the thermistor TH may be arranged at the edge portion of the battery cell  10 . In an implementation, the thermistor TH may be at a portion of the edge portion of the battery cell  10  that is spaced apart from, in the outer circumferential direction of the battery cell  10 , the portion of the edge portion of the battery cell  10  to which the connection member  125  is connected. In an implementation, the connection member  125  and the thermistor TH may be arranged at positions spaced apart from each other along the edge portion of the battery cell  10  to avoid interference with each other. In an implementation, the thermistor TH may be a chip-type thermistor TH that may be directly bonded to the edge portion of the battery cell  10 . In addition, the thermistor TH may be bonded to the edge portion of the battery cell  10  by solder mounting. 
     In the cell holder  110  in which the battery cells  10  are assembled, a long hole may expose the edge portions of the battery cells  10  while extending in the outer circumferential direction of the battery cells  10 , and the connection members  125  and the thermistors TH may be arranged at positions spaced apart from each other in the edge portions of the battery cells  10  while the edge portions of the battery cells  10  is exposed through the long hole formed in the cell holder  110 . As illustrated in  FIG. 11 , the adhesive resin AR may be on the connection member  125  bonded to the edge portion of the battery cell  10 , and the adhesive resin AR may not extend to the position of the thermistor TH and may not be formed on the thermistor TH. 
     Referring to  FIG. 13 , the connection hole CH may be formed in an alternate pattern along the column direction (e.g., L 1  and L 2 ) of the battery cells  10  (or the filling hole FH) to expose the pair of battery cells  10  adjacent to each other along the column direction (for example, L 1  and L 2 ) of the battery cells  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 connection opening region  132   c  (or the second opening region  132 ) that functions as the connection hole CH and the first opening region  131  that does not function as the connection hole CH may be arranged in an alternate pattern along the column direction (e.g., L 1  and L 2 ) of the battery cells  10  (or the filling hole FH). In an implementation, one connection opening region  132   c  (or the second opening region  132 ) that functions as the connection hole CH may be formed between two battery cells  10  (or the filling holes FH) that are paired with each other along the column direction (e.g., L 1  and L 2 ), and the connection opening region  132   c  (or the second opening region  132 ) that functions as the connection hole CH may not be formed between two battery cells  10  (or the filling holes FH) that are not paired with each other. In an implementation, the connection opening region  132   c  (or the second opening regions  132 ) may not be formed between every two battery cells  10  (or the filling holes FH) adjacent to each other along the column direction (e.g., L 1  or L 2 ) of the battery cell  10  or the filling hole FH, and may be formed alternatively between two battery cells  10  (or the filling holes FH) adjacent to each other along the column direction (e.g., L 1  or L 2 ) of the battery cell  10  (or the filling hole FH). In this case, the first opening region  131  for exposing the cooling flow path F passing between the adjacent battery cells  10  may be formed at a position P, between the adjacent battery cells  10  or between the adjacent filling holes FH, where the connection opening region  132  (or the second opening region  132 ) is not formed or a position adjacent thereto. 
     As will be described below, the filling hole FH may be formed at the central position of the upper end portion  10   a  of the battery cell  10 , and in the case where the first and second opening regions  131  and  132  are arranged between the adjacent battery cells  10  in an alternating pattern along the column direction Z 1  of the battery cell  10 , the first and second opening regions  131  and  132  may be arranged between the adjacent filling holes FH in the alternating pattern along the column direction (e.g., L 1  and L 2 ) of the filling holes FH, and may be arranged at positions adjacent to the position P between the adjacent filling holes FH in the alternating pattern. 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 between the adjacent filling holes FH in the column direction (e.g., L 1  and L 2 ) of the filling holes FH, and even in this case, the first open region  131  may still be arranged between the adjacent battery cells  10 . This is because the filling hole FH is formed at the central portion of the adjacent battery cell  10 . 
     As described above with reference to  FIG. 4 , six cooling flow paths F may be formed along the circumferential direction of one battery cell  10 . In this case, four cooling flow paths F may be formed at both sides of one battery cell  10  in the column direction Z 1  of the battery cells  10 , and at least one cooling flow path F of two adjacent cooling flow paths F formed at one side of the battery cell  10  may be exposed by the first opening region  131  formed in each cooling flow path F, and two adjacent cooling flow paths F formed at the other side of the battery cell  10  may be exposed by the connection opening region  132   c  or the second opening region  132  formed in common with respect to the two cooling flow paths F. As described above, with respect to one battery cell  10 , the first opening region  131  may be formed at one side, the connection opening region  132   c  (or the second opening region  132 ) may be formed at the other side, and the first and second opening regions  131  and  132  may be arranged in an alternating pattern along the column directions (for example, L 1  and L 2 ) of the battery cell  10  (or the filling hole FH). In an implementation, the connection opening region  132   c  (or the second opening region  132 ) that functions as the connection hole CH and the first opening region  131  that does not function as the connection hole CH are arranged in an alternate pattern along the column direction (e.g., L 1  and L 2 ) of the battery cells  10  (or the filling hole FH). 
     Referring to  FIG. 13 , the second opening regions  132  that extend along the outer circumferential direction of the filling holes FH of the adjacent rows (e.g., L 1  and L 2 ) may be formed in different shapes, e.g., the second opening region  132  that extends along the outer circumferential direction of the filling hole FH of the first row L 1  may extend along the outer circumferential direction of the filling holes FH in a downward direction from the connection member  125  toward the filling holes FH of the second row L 2 . In an implementation, the second opening region  132  that extends along the outer circumferential direction of the filling hole FH of the second row L 2  may extend from the connection member  125  toward the filling hole FH of the first row L 1  along the outer circumferential direction of the filling hole FH in the upper direction. As described above, the second opening regions  132  that extends along the outer circumferential direction of the filling hole FH in the first and second rows L 1  and L 2  adjacent to each other may be formed to have different extension directions from each other, and thus, the second opening regions  132  having the different extension directions from each other may be densely arranged in a narrow space between the filling holes FH in the first and second rows L 1  and L 2  while avoiding interference between each other. In an implementation, the second opening region  132  may extend along the outer circumferential direction of the filling hole FH, of the filling hole FH may be omitted and in this case, the second opening region  132  may be understood as extending along the outer circumferential direction of the central portion of the upper end portion  10   a  of the battery cell  10 . This is because the filling hole FH may be formed at the central portion of the upper end portion  10   a  of each battery cell  10  to expose the bus bar  120  coupled to the central portion of the upper end portion  10   a  of the battery cell  10 . 
     Referring to  FIG. 1 , the circuit board  130  may be arranged on the upper holder  110   a  and may not be arranged under 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 , and according to an embodiment, the circuit board  130  may be arranged on the upper holder  110   a  and may collect voltage information of the plurality of battery cells  10  through the upper end portions  10   a  of the battery cells  10 . In an implementation, the circuit board  130  may collect the voltage information of the plurality of battery cells  10  through the upper end portions  10   a  or the lower end portions  10   b  of the plurality of battery cells  10 , and for example, the circuit board  130  may collect the voltage information of the plurality of battery cells  10  through the upper end portions  10   a  of the plurality of battery cells  10 . In an implementation, the battery cell  10  may include the first and second electrodes  11  and  12  that are formed at the upper end portion  10   a  and the lower end portion  10   b , or the circuit board  130  may not need to be connected to both of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10  to obtain the voltage information of the battery cell  10 , the voltage information of the plurality of battery cells  10  may be obtained through the upper end portions  10   a  or the lower end portions  10   b  of the battery cells  10 , e.g., the upper end portions  10   a  of the battery cells  10 , and the voltage information of the battery cells  10  may be collected through the circuit board  130  that is selectively arranged on the upper end portions  10   a  of the battery cells  10 , thus the structure of the entire battery pack may be simplified. In an implementation, the electrical connection of the battery cell  10  may be performed through both of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , and the voltage measurement of the battery cell  10  may be performed through any one of the upper end portion  10   a  of the battery cell  10  selectively, for example, through the upper end portion  10   a  of the battery cell  10 . 
     If the voltage measurement were to be performed on both of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , the circuit board  130  may need to be arranged on both of the upper end portion  10   a  and the lower end portion  10   b  of the battery cell  10 , and accordingly, the overall structure of the battery pack may be complicated, and a separate wiring structure for connecting the circuit boards  130  on both sides may be required to collect the voltage information measured from the circuit boards  130  on both sides. 
     Referring to  FIGS. 9 and 11 , according to an embodiment, the potting resin PR may be formed at a position corresponding to the central portion 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 , and the adhesive resin AR may be formed at a position corresponding to the edge portion surrounding the central portion 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 . In this case, the potting resin PR and the adhesive resin AR may include different components (e.g., the potting resin PR may be different from the adhesive resin AR). 
     In an implementation, the bus bar  120  that electrically connects the adjacent battery cells  10  to each other may connect the 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 the coupling structure between the central portions of the upper end portions  10   a  of the battery cells  10  and the coupling pieces  120   a  at both ends of the bus bar  120 . In an implementation, 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 help protect the coupling structure between the battery cells  10  and the coupling pieces  120   a  of the bus bar  120  from harmful (e.g., external) elements, e.g., oxygen or moisture, and may protect the coupling structure between different heterogeneous materials formed by welding, e.g., the heterogeneous materials between the upper end portion  10   a  of the battery cells  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 hole FH of the circuit board  130  on the bus bars  120 . The filling holes FH of the circuit board  130  may expose the coupling pieces  120   a  at both ends of the bus bar  120  connected to the battery cells  10 , respectively. In an implementation, the filling hole FH may be formed for each of the battery cells  10 , two filling holes FH may be formed for each of the bus bars  120  that connects two adjacent battery cells  10  to each other, e.g., one filling hole FH may be formed for each of the coupling pieces  120   a  at both ends of the bus bar  120 , the potting resin PR may be filled in each of the filling holes FH, and thus the potting resin PR filled in the filling holes FH may cover the coupling structure between the battery cells  10  and the coupling pieces  120   a  formed at both ends of the bus bars  120  (e.g., the coupling pieces  120   a  formed at both ends of the bus bar  120 ). In an implementation, the potting resin PR filling the filling holes FH of the circuit board  130  may be injected onto the coupling pieces  120   a  of the bus bars  120  between the circuit board  130  and the battery cells  10 . 
     In an implementation, the bus bar  120  may include the central protruding connection piece  120   c  that connects 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 protruding connection piece  120   c  in a bent shape and support the protruding connection piece  120   c  at a level spaced apart from the battery cells  10  from the coupling pieces  120   a  at both ends in the height direction of the battery cells  10 . In this case, the circuit board  130  arranged on the bus bar  120  may have the escape hole  132   a  for completely exposing the entire protruding connection piece  120   c . As illustrated in  FIG. 12 , the protruding connection piece  120   c  of the bus bar  120  and the circuit board  130  (e.g., the solid portion of the circuit board  130 ) may be arranged so as not to overlap each other in the height direction through the escape hole  132   a  formed in the circuit board  130 , thus the circuit board  130  may be arranged at a position close to the coupling pieces  120   a  of the bus bar  120 , and the gap q between the circuit board  130  and the coupling piece  120   a  of the bus bar  120  in the height direction may be reduced, such that the amount of the potting resin PR injected onto the coupling pieces  120   a  of the bus bars  120  through the filling holes FH of the circuit board  130  may be reduced, and the contamination of the surroundings due to the movement of the surplus or uncontrollable 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  based on proper fluidity when uncured, e.g., may be injected through the filling hole FH of the circuit board  130 , may be cured by, after injection, irradiating UV light, heating, or curing in a timely manner, and then may protect the coupling structure between the bus bars  120  and the battery cells  10  from harmful (e.g., external) elements, e.g., oxygen or moisture. In an implementation, the potting resin PR may help 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 PR may include a urethane resin such as polyurethane. 
     In an implementation, as illustrated in  FIG. 11 , the potting resin PR may be on the coupling structure between the upper end portions  10   a  of the battery cells  10  and the bus bars  120 . In an implementation, the potting resin PR may be on the coupling structure between the lower end portions  10   b  of the battery cells  10  and the bus bars  120 . In an implementation, the circuit board  130  may be selectively formed only on the upper end portion  10   a  of the battery cell  10  (i.e., the circuit board  130  is selectively arranged only on the upper holder  110   a ), and in this case, the coupling structure between the lower end portion  10   b  of the battery cell  10  and the bus bar  120  may be directly on the coupling structure between the lower end portion  10   b  of the battery cell  10  and the bus bar  120  without the filling hole FH of the circuit board  130 . 
     Throughout the present specification, in the case where the potting resin PR is formed at a position corresponding to the central portion 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 , the potting resin PR may be formed on the coupling structure between the battery cell  10  and the bus bar  120  to cover the coupling portion, and the potting resin PR may be filled in the filling hole FH of the circuit board  130  on the bus bar  120 . 
     In the case where the potting resin PR is formed on the central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , 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 coupled. In an implementation, the central portion of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10  refers to a position to which the coupling pieces  120   a  at both ends of the bus bar  120  are coupled, e.g., 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 thereto. 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 refer to an inner area of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , other than the edge portion, e.g., an inner area surrounded by the edge portion, to distinguish a position where any one of the first and second electrodes  11  and  12  of the battery cell  10  is formed from a position where another electrode is formed, along the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , and 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 refer to an inner area of the upper end portion  10   a  or the lower end portion  10   b  of the battery cell  10 , based on the boundary between the one electrode and another of the battery cell  10 . As described above 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 at the edge portion of the upper end portion  10   a . In this case, in relation to the positions to which the coupling pieces  120   a  at both ends of the bus bar  120  are coupled, the central portion of the upper end portion  10   a  of the battery cell  10  may refer to the second electrode  12  formed at 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  in which the battery cells  10  are 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 coupled 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 cells  10 . The terminal hole  112  of the upper holder  110   a  is to expose the upper end portion  10   a  of the battery cell  10 , the filling hole FH of the circuit board  130  is to expose the coupling piece  120   a  of the bus bar  120  coupled to 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, in the case where the circuit board  130  is arranged under 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 , according to an embodiment, the connection member  125  forming the voltage measurement line between the battery cell  10  and the circuit board  130  may be coupled to the edge portion of the upper end portion  10   a  of the battery cell  10 . Here, the edge portion of the upper end portion  10   a  of the battery cell  10  may refer to the portion surrounding the central portion of the upper end portion  10   a . The connection member  125  may pass through the connection hole CH of the circuit board  130  to electrically connect the battery cell  10  to the circuit board  130 , and one end of the connection member  125  may form a junction with the edge portion of the battery cell  10  and the other end of the connection member  125  may form a junction with the circuit board  130 . In this case, the adhesive resin AR may cover the junctions of one end and the other end of the connection member  125 , e.g., the adhesive resin AR may continuously cover the junctions of one end and the other end of the connection member  125  together. In an implementation, the adhesive resin AR may entirely cover the connection member  125 . The adhesive resin AR may cover the edge portion of the upper end portion  10   a  of the battery cell  10  and the junctions of the connection member  125  formed on the circuit board  130  to help protect the junctions from an external impact, and the adhesive resin AR may entirely cover the connection member  125  to help prevent the connection member  125  formed of the conductive wire or the conductive ribbon from being disconnected due to an insufficient mechanical strength. 
     The adhesive resin AR may cover two connection members  125  bonded to the edge portions of two adjacent battery cells  10  exposed through the connection hole CH. In an implementation, the adhesive resin AR may cover one end and another end of the two connection members  125  respectively bonded to the two battery cells  10  exposed through the connection hole CH, and may continuously cover the one end and the other ends of the two connection members  125 . In this case, the adhesive resin AR may entirely cover the two connection members  125  bonded to the two battery cells  10  exposed through the connection hole CH. The adhesive resin AR may continuously cover the upper end portions  10   a  of the two battery cells  10  exposed through the connection hole CH while entirely covering the two connection members  125 , and may electrically insulate the upper end portions  10   a  of the two battery cells  10  exposed through the connection hole CH. In an implementation, the adhesive resin AR may cover the upper end portions  10   a  of the two battery cells  10  exposed through the connection hole CH together with the connection members  125 , thereby electrically insulating the two connection members  125  and the upper end portions  10   a  of the two battery cells  10 . 
     The connection member  125  may be supported while being suspended between the one end bonded to the edge portion of the upper end portion  10   a  of the battery cell  10  and the other end bonded to the circuit board  130 , the adhesive resin AR may be continuously formed to entirely cover the connection member  125  together with the bonding portions formed at the one end and the other end of the connection member  125 , and accordingly, the connection member  125  may be stably supported without moving by an external impact. 
     In an implementation, the adhesive resin AR may include a two-component curable resin including two different components. In an implementation, the adhesive resin AR may include an epoxy adhesive, and may include a two-component curable resin including epoxy as a main material and amine as a curing agent. In an implementation, the adhesive resin AR may be applied on the connection member  125  and then cured by heating or curing in a timely manner. In an implementation, the adhesive resin AR may be cured by irradiating UV light. The cured adhesive resin AR may firmly support the entire connection member  125 , including the one end and the other end thereof. The adhesive resin AR may be applied on the connection member  125  based on proper fluidity when uncured, e.g., may be injected through the connection hole CH, may be cured by, after injection, irradiating UV light, heating, or curing in a timely manner, and then may firmly support the connection member  125 . 
     Referring to  FIGS. 10 and 11 , the adhesive resin AR may cover the edge portions of the upper end portions  10   a  of the adjacent battery cells  10  exposed through the connection hole CH. In this case, the connection hole CH may expose the hollow protrusions  115  connected to the cooling flow paths F formed around the battery cell  10  covered with the adhesive resin AR. In an implementation, the connection hole CH may expose a pair of hollow protrusions  115  facing each other with the connection members  125  therebetween, and in this case, the pair of hollow protrusions  115  may be between the pair of battery cells  10  exposed through the connection hole CH. 
     Throughout the present specification, in the case where the adhesive resin AR is formed at a position corresponding to the edge portion 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 , the adhesive resin AR may be formed on the edge portion of the battery cell  10  to cover the junctions of the connection members  125 , and the adhesive resin AR may be filled in the connection holes CH of the circuit board  130  formed on the upper portion of the battery cells  10 . 
     In the present disclosure, in relation to the edge portion of the upper end portion  10   a  of the battery cell  10  at which the adhesive resin AR is formed, the adhesive resin AR may be formed at the edge portion of the upper end portion  10   a  of the battery cell  10  to which the connection member  125  is coupled. In this case, the edge portion of the upper end portion  10   a  of the battery cell  10  refers to a position of the upper end portion  10   a  of the battery cell  10  to which the connection member  125  is coupled, and the edge position of the upper end portion  10   a  of the battery cell  10  is not limited. In an implementation, in relation to the position where the adhesive resin AR is formed, the edge portion of the upper end portion  10   a  of the battery cell  10  may refer to an outer area of the upper end portion  10   a  of the battery cell  10 , other than the central portion, that is, an outer area surrounding the central portion, to distinguish a position where any one of the first and second electrodes  11  and  12  of the battery cell  10  is formed from a position where another electrode is formed, along the upper end portion  10   a  of the battery cell  10 , and in relation to the position where the adhesive resin AR is formed, the edge portion of the upper end portion  10   a  of the battery cell  10  may refer to an outer area of the upper end portion  10   a  of the battery cell  10 , based on the boundary between the one electrode and another of the battery cell  10 . 
     As described above 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 at the edge portion of the upper end portion  10   a  and the lower end portion  10   b . In this case, in relation to the position to which the connection member  125  is coupled, the edge portion of the upper end portion  10   a  of the battery cell  10  may refer to the first electrode  11  formed at the edge portion of the upper end portion  10   a  of the battery cell  10 . 
       FIG. 11  illustrates the adhesive resin AR formed on the connection members  125  that connect the upper end portions  10   a  of the battery cells  10  to the circuit board  130 . In an implementation, the circuit board  130  may be selectively formed on the upper end portion  10   a  of the battery cell  10  (i.e., the circuit board  130  is selectively arranged only on the upper holder  110   a ), or the circuit board  130  may be formed under the lower end portions  10   b  of the battery cells  10 , and in this case, the adhesive resin AR may be formed on the connection members  125  that connect the lower end portions  10   b  of the battery cells  10  to the circuit board  130 . 
     The potting resin PR and the adhesive resin AR are provided to perform different functions, and they may include different components having different material characteristics. In an implementation, the potting resin PR may perform a function of protecting the coupling portions of the bus bars  120  from harmful elements such as oxygen or moisture, and thus, may have airtightness to help prevent penetration of the harmful elements. On the other hand, the adhesive resin AR may have adhesion to be firmly attached to the connection members  125  thereby protecting the connection member  125  such as a conductive wire or a conductive ribbon from an external impact. 
     Referring to  FIGS. 14 to 16 , the separation member  140  may be arranged on the cell holder  110 . The separation member  140  may spatially separate the cooling flow paths F for the cooling medium CM for cooling the battery cells  10 , from the exhaust gas path for the exhaust gas DG discharged from the vent portions  13  of the battery cells  10 . In an implementation, the separation member  140  spatially separates the cooling flow paths F from the exhaust gas path, thereby removing a risk of explosion or fire due to mixing of the high-temperature and high-pressure exhaust gas DG flowing through the exhaust gas path and the cooling medium CM such as air flowing through the cooling flow paths F. In addition, in the battery pack mounted on an electric vehicle, the exhaust gas (DG) may be prevented from flowing into the interior of the vehicle along an uncontrolled path. 
     Referring to  FIG. 1 , the separation member  140  may include an upper separation member  140   a  arranged on the upper holder  110   a  and a lower separation member  140   b  arranged under the lower holder  110   b . For example, the upper separation member  140   a  may be arranged on the circuit board  130  arranged on the upper holder  110   a . In an implementation, the circuit board  130  may not be arranged under the lower holder  110   b , and thus the lower separation member  140   b  may be arranged directly under the lower holder  110   b . In an implementation, the lower separation member  140   b  may be arranged under the lower bus bars  120   b  arranged under the lower holder  110   b.    
     Referring to  FIG. 14 , open regions  145  through which the cooling flow paths F passes may be formed in the separation member  140 . The cooling flow path F may be formed across the separation member  140  while passing through the open region  145  of the separation member  140 , e.g., the hollow protrusion  115  of the cell holder  110  may be inserted into the open region  145  of the separation member  140 , and thus the cooling flow path F that passes through the open region  145  of the separation member  140  may be formed. In an implementation, the open regions  145  of the separation member  140  may be formed at positions corresponding to the hollow protrusions  115  and may be formed in a shape corresponding to the hollow protrusions  115 . In an implementation, the open region  145  may be formed in a circular shape corresponding to the hollow protrusion  115  including the circular wall body  115   a  that surrounds the central hollow portion. In an implementation =, the open region  145  may be formed in various shapes corresponding to the hollow protrusion  115 , e.g., an elliptical shape or various polygonal shapes including a hexagon. 
     Referring to  FIG. 15 , according to an embodiment, the open region  145  may include a wall body  145   a  that extends toward the hollow protrusion  115 , and the wall body  115   a  of the hollow protrusion  115  may be inserted into the wall body  145   a  of the open region  145 . In an implementation, the wall body  145   a  of the open region  145  and the wall body  115   a  of the hollow protrusion  115  may be formed in circular shapes corresponding to each other at positions corresponding to each other, and may be assembled by being press-fit toward each other. In an implementation, the outer circumference of the wall body  115   a  of the hollow protrusion  115  may be inserted into the inner circumference of the wall body  145   a  in the open region  145 , and the wall body  115   a  of the hollow protrusion  115  and the wall body  145   a  in the open region  145  may be assembled by being press-fit toward each other. In an implementation, the wall body  145   a  of the open region  145  may have an inner circumference having a size that decreases gradually toward the hollow protrusion  115 , or the wall body  115   a  of the hollow protrusion  115  may have an outer circumference having a size that increases gradually toward the open region  145 , and the wall body  145   a  of the open region  145  or the wall body  115   a  of the hollow protrusion  115  may have a gradient along the direction of protruding toward each other such that the wall body  145   a  of the open region  145  and the wall body  115   a  of the hollow protrusion  115  may be press-fit toward each other. 
     The separation member  140  may include spacers  141  that protrude toward the cell holder  110  to maintain a predefined gap between the separation member  140  and the cell holder  110 . The gap between the separation member  140  and the cell holder  110 , which is maintained by the spacers  141 , may provide the exhaust gas path for the exhaust gas discharged from the battery cells  10 . As will be described below, a space between the blocking region  144  of the separation member  140  and the cell holder  110  may form the exhaust gas path through which the exhaust gas discharged from the upper end portions  10   a  of the battery cells  10  or the lower end portions  10   b  of the battery cells  10  (e.g., the vent portions  13  formed at the upper end portions  10   a  or the lower end portion  10   b  of the battery cells  10 ) is discharged, and in this case, the spacers  141  of the separation member  140  may maintain an appropriate gap between the separation member  140  and the cell holder  110 . In an implementation, the spacers  141  formed at the upper separation member  140   a  may provide the exhaust gas path for the exhaust gas discharged from the upper end portions  10   a  of the battery cells  10  while maintaining the gap between the upper side of the upper holder  110   a  and the blocking region  144  of the upper separation member  140   a , and the spacers  141  formed at the lower separation member  140   b  may provide the exhaust gas path for the exhaust gas discharged from the lower end portions  10   b  of the battery cells  10  while maintaining the gap between the lower side of the lower holder  110   b  and the blocking region  144  of the lower separation member  140   b.    
     Referring to  FIGS. 14 and 15 , the open 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 pass through at least a portion of the battery pack. The open regions  145  of the upper and lower separation members  140   a  and  140   b  may form the cooling flow paths F that pass through substantially the entire structure of the battery pack, together with the hollow protrusions  115  of the cell holder  110  interposed between the upper and lower separation members  140   a  and  140   b , and the open regions  135  of the circuit board  130  interposed between the upper and lower separation members  140   a  and  140   b . In an implementation, the cooling flow path F may connected from the upper separation member  140   a , through the circuit board  130 , the upper and lower holders  110   a  and  110   b , between the battery cells  10  inserted into the upper and lower holders  110   a  and  110   b , and to the lower separation member  140   b , to pass through substantially the entire structure of the battery pack in the height direction. To this end, the open regions  145  of the upper and lower separation members  140   a  and  140   b  and the open regions  135  of the circuit board  130  may be formed at positions corresponding to each other, and may be formed at positions corresponding to the hollow protrusions  115  such that the hollow protrusions  115  of the cell holder  110  may be inserted into the open regions  145  and the open regions  135 . 
     The separation member  140  may include the blocking region  144  formed at a position corresponding to the vent portions  13  of the battery cell  10 . Hereinafter, the blocking region  144  formed at the upper separation member  140   a  will be mainly described. In an implementation, the technical aspects of the upper separation member  140   a  described below may be substantially equally applied to the lower separation member  140   b.    
     Referring to  FIG. 16 , the blocking region  144  may be formed to block areas above the vent portions  13  such that the exhaust gas DG discharged from the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) of the battery cells  10  may not pass through the separation member  140 . For example, the blocking region  144  may be formed in a closed shape, and unlike the open regions  145 , the separation member  140  may not have an opened portion such that the upper and lower sides of the separating member  140  are not fluidly connected to each other, and the upper and lower sides of the separation member  140  are separated from each other, and thus the lower side of the blocking region  144  in which the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) are arranged and the upper side of the blocking area  144  may not be fluidly connected to each other. 
     As described above, the lower side of the blocking region  144  in which the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) are arranged and the upper side of the blocking area  144  may not be fluidly connected to each other and may be separated from each other, thus the exhaust gas DG discharged from the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) may not pass through the blocking region  144  and may not be discharged to an upper portion of the blocking region  144 , and the exhaust gas DG discharged from the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) may be blocked by the blocking region  144  to flow along the exhaust gas path between the blocking region  144  and the battery cells  10 , and may be discharged to the outside of the battery pack along the exhaust gas path. 
     Referring to  FIG. 7 , according to an embodiment, the group of the battery cells  10  that constitutes the battery pack may be arranged in which one of the pair of adjacent battery cells  10  is inverted in the height direction, and may include the first group of the battery cells  10  in which the vent portions  13  are formed at the upper end portions  10   a  and the second group of battery cells  10  in which the vent portions  13  are formed in the lower end portions  10   b . In this case, as illustrated in  FIG. 16 , the blocking region  144  of the upper separation member  140   a  arranged on the upper side of the upper holder  110   a  may be formed in a closed shape such 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 the battery cells  10  are arranged, and the other side of the upper separation member  140   a , which is opposite to the upper end portions  10   a  (or the vent portions  13 ) of the first group of the battery cells  10 , are not fluidly connected to each other. In an implementation, the blocking region  144  of the lower separation member  140   b  arranged under the lower side of the lower holder  110   b  may be formed in a closed shape such that one side of the lower separation member  140   b , in which the bottom portions  10   b  (or the vent portions  13 ) of the second group of the battery cells  10  are arranged, and the other side of the lower separation member  140   b , which is opposite to the bottom portions  10   b  (or the vent portions  13 ) of the second group of the battery cells  10 , are not fluidly connected to each other. 
     Referring to  FIG. 16 , the blocking region  144  is not limited to positions corresponding to the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) of the battery cells  10 , and may be formed over the entire area of the separation member  140  other than the open regions  145 . For example, the blocking region  144  may extend to the entire area of the separation member  140 , other than the open regions  145  for penetration of the cooling flow paths F, between the open regions  145 , and may form the exhaust gas path continuously connected from positions corresponding to the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) to the exhaust hole DH. For example, the exhaust gas DG discharged from the vent portions  13  (or the terminal holes  112  exposing the vent portions  13 ) at different positions may be collected into the exhaust hole DH along the exhaust gas path continuously formed between the blocking region  144  of the separation member  140  and the battery cells  10 . In an implementation, the exhaust gas path may be formed between the blocking region  144  of the separation member  140  and the battery cells  10  or between the blocking region  144  of the separation member  140  and the cell holder  110  (or the circuit board  130 ), and may be continuously formed from the vent portion  13  (or the terminal hole  112  exposing the vent portion  13 ) of each battery cell  10  to the exhaust hole DH formed at one side of the cell holder  110 . For example, the exhaust gas path may be formed in a manner in which spaces between the hollow protrusions  115  inserted into the open regions  145  of the separation member  140  are continuously connected to each other, and the exhaust gas DG collected into the exhaust hole DH through the exhaust gas path may be discharged to the outside of the battery pack. According to an embodiment, the exhaust gas path for the exhaust gas discharged from the upper end portions  10   a  or the lower end portions  10   b  (or the vent portions  13  formed at the upper end portions  10   a  or the lower end portions  10   b ) of the battery cells  10  may be formed between the upper side of the upper holder  110   a  and the upper separation member  140   a  and between the lower side of the lower holder  110   b  and the lower separation member  140   b , and may be formed in a manner in which spaces between the hollow protrusions  115  inserted into the open regions  145  of the upper separation member  140   a  and the lower separation member  140   b  are continuously connected to each other. 
     The exhaust gas path, one side of which is closed by the blocking region  144  formed in a closed shape such that the upper and lower sides of the separation member  140  are not connected to each other, may be spatially separated from the cooling flow paths F passing through the upper and lower sides of the separation member  140  through the open regions  145  of the separation member  140 . In an implementation, the separation member  140  may be formed generally in a plate shape having a closed shape, except for the open regions  145  into which the hollow protrusions  115  are inserted. In this case, the cooling flow paths F may pass through the separation member  140  through the open regions  145  while being surrounded by the hollow protrusions  115 , and may be spatially separated from the exhaust gas path formed between the separation member  140  (the blocking region  144 ) and the battery cells  10 , and by the structure in which the cooling flow paths F and the exhaust gas path are spatially separated from each other, a risk of a safety accident that may cause explosion or ignition due to mixing of the cooling medium CM flowing along the cooling flow path F and the high-temperature and high-pressure exhaust gas DG flowing along the exhaust gas path, may be reduced, and in the case of the battery pack mounted on an electric vehicle, the exhaust gas DG may be prevented from being introduced into the interior of the vehicle through the separation member  140 , and thus the safety of passengers from toxic gas may be secured. 
     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 under the lower separation member  140   b , respectively. An opening OP through which the cooling medium is introduced, may be formed at the upper duct  150   a , and the cooling medium introduced into the battery pack through the opening OP may cool the battery cells  10  while passing through the cooling flow paths F formed from the upper separation member  140   a  to the lower separation member  140   b . The cooling flow paths F may be formed between the adjacent battery cells  10 , and the battery cells  10  may be cooled by the cooling medium vertically flowing in the height direction of the battery cells  10 . 
     The lower duct  150   b  may be connected to a fluid device for generating a pressure difference between the inside and the outside of the battery pack, to force a flow of the cooling medium passing through the battery pack. In an implementation, a connection portion M for the fluid device may be formed at one side of the lower duct  150   b . According to an embodiment, the fluid device may be a suction type pump for maintaining an internal pressure of the battery pack to be a negative pressure with respect to the external atmosphere of the battery pack. The fluid device (or the connection portion M for 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 the inlet of the cooling medium, and the fluid device (or the connection portion M for the fluid device) connected to the lower duct  150   b  may form the outlet of the cooling medium. In an implementation, the fluid device may be a blower type pump, and in this case, the fluid device (or the connection portion M for the fluid device) connected to the lower duct  150   b  may form the inlet of the cooling medium, and the opening OP of the upper duct  150   a  may form the outlet of the cooling medium. 
     A negative pressure may be generated in the battery pack by operation of the fluid device, the cooling medium may be introduced into the battery pack through the opening OP of the upper duct  150   a  by a pressure difference between the inside and the outside of the battery pack, and the cooling medium introduced into the battery pack may cool the battery cells  10  while passing through the cooling flow paths F and may be discharged to the outside of the battery pack through the fluid device connected to the connection portion M of the lower duct  150   b.    
     In an implementation, the opening OP formed in the upper duct  150   a  and the fluid device (or the connection portion M for the fluid device formed in the lower duct  150   b ) connected to the lower duct  150   b  may form the inlet and the outlet of the cooling medium, respectively, and thus, the position of the opening OP formed in the upper duct  150   a  and the position (or the position of the connection portion M formed in the lower duct  150   b ) of the fluid device connected to the lower duct  150   b  may be indicated on both ends of a diagonal line crossing the battery pack in an diagonal direction. 
     In relation to the positions of the inlet and the outlet of the cooling medium, the diagonal direction of the battery pack may refer to a direction that simultaneously follows the height direction of the battery cell  10  and the direction Z 1  of the long side lines of the envelope S 1  and S 2  (see  FIG. 4 ) surrounding the battery cells  10 . That is, supposing that the group of battery cells  10  that constitutes the battery pack is surrounded by the rectangular envelope S 1  and S 2  (see  FIG. 4 ) consisting of the pair of long side lines S 1  and the pair of short side lines S 2  that extend to linearly surround the circumference of the group of battery cells  10 , the diagonal direction of the battery pack may refer to the direction that simultaneously follows the height direction of the battery cell  10  and the direction Z 1  of the long side lines of the envelope S 1  and S 2 . For reference, the direction Z 1  of the long side lines and the direction Z 2  of the short side lines of the envelope S 1  and S 2  may correspond to the direction of long side lines and the direction of the short side lines of the cell holder  110 , respectively, and may correspond to the direction of long side lines and the direction of the short side lines of the battery pack, respectively. 
     In an implementation, the flow of the cooling medium passing through the inside of the battery pack may be induced by using the opening OP of the upper duct  150   a  and the fluid device of the lower duct  150   b  (or the connection portion M formed in the lower duct  150   b ) formed at both ends of the diagonal line crossing the battery pack in the diagonal direction. In an implementation, the position of the opening OP formed in the upper duct  150   a  and the position of the fluid device (or the connection portion M formed in the lower duct  150   b ) connected to the lower duct  150   b  may be formed at positions spaced apart from each other along the direction Z 1  of the long side lines of the envelope S 1  and S 2  or the direction Z 1  of the long side lines of the battery pack, and for example, in the case where the position of the opening OP formed in the upper duct  150   a , for example, the position of at least a portion of the opening OP formed in the upper duct  150   a  is formed at one edge position along the direction of the long side lines of the battery pack, the position of the fluid device connected to the lower duct  150   b  (or the position of the connection portion M formed in the lower duct  150   b ) may be formed at the other edge position along the direction of the long side lines of the battery pack. As described above, the opening OP formed in the upper duct  150   a  and the fluid device (or the connection portion M formed in the lower duct  150   b ) connected to the lower duct  150   b  may be formed at the one edge position and the other edge position along the direction of the long side lines of the battery pack, and accordingly, the flow of the cooling medium that connects the opening OP of the upper duct  150   a  to the fluid device (or the connection portion M formed in the lower duct  150   b ) of the lower duct  150   b  may be formed to cross the inside of the entire battery pack. 
     As described above, the connection portion M for the fluid device may be formed at the one edge portion of the battery pack in the direction of the long side lines of the battery pack, and a fixing portion FX for the fluid device may be formed together with the connection portion M for the fluid device at the one edge portion of the battery pack in which the connection portion M for the fluid device is formed. That is, an inlet or an air blowing hole of the fluid device, according to a type of the fluid device, may be connected to the connection portion M for the fluid device, and the position of the fluid device may be fixed by the fixing portion FX for the fluid device. The exhaust pipe DP may be formed at the one edge portion of the battery pack in which the connection portion M for the fluid device is formed. The exhaust pipe DP may require an installation space to protrude toward the outside of the battery pack, the exhaust pipe DP may be formed at one edge portion of the battery pack to which the fluid device is connected, and the connection portion M for the fluid device, the fixing portion FX for the fluid device, and the exhaust pipe DP may be formed at one edge portion of the battery pack, and accordingly, the other edge portion of the battery pack may provide a position alignment surface of the battery pack, for example, a reference surface for position alignment with an electric vehicle on which the battery pack is mounted. 
     One or more embodiments may provide a battery pack that includes potting resin and adhesive resin for protecting electrical connections of a high-current charge/discharge path and a low-current voltage measurement line, thereby preventing a short circuit from occurring at the charge/discharge path and the voltage measurement line, and improving electrical durability. 
     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.