Patent Publication Number: US-2016226034-A1

Title: Energy storage device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2015-0015611, filed on Jan. 30, 2015, in the Korean Intellectual Property Office, and entitled: “Energy Storage Device,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to an energy storage device, and more particularly, to an energy storage device having a secondary battery. 
     2. Description of the Related Art 
     In general, a secondary battery is a battery capable of being charged and discharged so as to be repeatedly used. The secondary battery may be charged using new and renewable energy, e.g., solar energy, as well as an existing electric power system, e.g., a power plant. The secondary battery is used as an energy source in automobiles or large facilities requiring power supply, as well as in electronic devices, e.g., a portable phone, a notebook computer, and a camcorder. An energy storage device is configured by connecting a plurality of secondary batteries in series or parallel for the purpose of high output or high capacity. 
     SUMMARY 
     An energy storage device according to an embodiment includes at least one battery pack including a plurality of unit batteries, a pack frame accommodating the plurality of unit batteries, and a rack housing accommodating the at least one battery pack with the pack frame, the rack housing including at least one support member supporting a side wall of the pack frame, wherein the plurality of unit batteries are arranged in an overlapping manner in a first direction, the at least one support member extending in a second direction perpendicular to the first direction and traversing the side wall of the pack frame. 
     The plurality of unit batteries may be arranged in at least one column extending in the first direction. The at least one support member may include first and second support members coupled to the side walls of the pack frame from both ends of the column in a length direction. 
     The at least one support member may extend along an outer surface of the side wall. 
     The at least one support member may extend along a line corresponding to a height of a half of a height of the unit battery. Also, the at least one support member may extend to pass through the center of the side wall. The height of the side wall of the pack frame may be substantially similar to or the same as the height of the unit battery. 
     The at least one support member may be detachably coupled to the pack frame. Here, the pack frame and the at least one support member may be slidably coupled. 
     The pack frame may include at least one insertion recess provided on the side wall parallel to the second direction and allowing the support member to be inserted therein. 
     The insertion recess may extend in the second direction on an outer surface of the side wall. 
     The insertion recess may extend from one corner of the side wall to a corner of the opposite side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will become apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, in which: 
         FIG. 1  illustrates a perspective view of an energy storage device according to an embodiment; 
         FIG. 2  illustrates a partial, enlarged perspective view of a battery pack frame of  FIG. 1 ; 
         FIG. 3  illustrates a perspective view of a pack frame of  FIG. 2 ; 
         FIG. 4  illustrates a perspective view of a rack housing of  FIG. 1 ; 
         FIG. 5  illustrates a schematic perspective view of an electrode assembly according to an embodiment; 
         FIG. 6  illustrates a view of the battery pack of  FIG. 2  in the rack housing of  FIG. 4 ; 
         FIG. 7  illustrates a schematic top of an expansive force acting on the battery pack of  FIG. 1  in an arrow direction; 
         FIG. 8  illustrates a partial cross-sectional view of a pack frame in a rack housing according to a modified embodiment; 
         FIG. 9  illustrates a perspective view of a battery pack in a rack housing according to a modified embodiment; and 
         FIG. 10  illustrates a perspective view of a rack housing and a battery pack according to another embodiment. 
     
    
    
     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 elements and regions may be exaggerated for clarity of illustration. It will also be understood that when an element is referred to as being “on” another element or substrate, it can be directly on the other element or substrate, or intervening elements may also be present. In addition, it will also be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Further, when it is described that an element is “coupled” to another element, the element may be “directly coupled” to the other element or “electrically coupled” to the other element through a third element. 
     In the accompanying drawings, portions irrelevant to description of the example embodiments may be omitted for clarity. Like reference numerals refer to like elements throughout. 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings such that they can be easily practiced by those skilled in the art. A secondary battery mentioned described hereinafter may be a battery having any configuration that can be charged and discharged. 
       FIG. 1  is a perspective view of an energy storage device according to an embodiment,  FIG. 2  is a perspective view of a battery pack frame of  FIG. 1 ,  FIG. 3  is a perspective view of a pack frame of  FIG. 2 , and  FIG. 4  is a perspective view of a rack housing of  FIG. 1 . The energy storage device according to an embodiment will be described in detail with reference to  FIGS. 1 through 4 . 
     Referring to  FIG. 1 , an energy storage device according to an embodiment may include a battery pack  100  and a rack housing  200  for accommodating the battery pack  100 .  FIG. 1  illustrates eight (8) battery packs  100  accommodated in the rack housing  200 , but embodiments are not limited thereto, i.e., embodiments may include an energy storage device in which one or more battery packs  100  are accommodated in the rack housing  200 . 
     Referring to  FIG. 2 , the battery pack  100  is an assembly in which a plurality of unit batteries are connected in series or parallel, including a plurality of unit batteries  110 ,  110 A, and  110 B, and a pack frame  120  accommodating the unit batteries. It is noted that while  FIG. 2  illustrates unit batteries that are connected in series, embodiments are not limited thereto, e.g., the unit batteries may be appropriately connected in series and/or in parallel to obtain intended capacity or output. 
     Further, although not shown, the battery pack  100  may further include a spacer between the unit batteries in order to insulate the unit batteries and provide a heat dissipation passage. Also, although not shown, the battery pack  100  may further include a control module for controlling charging and discharging of the unit batteries. 
     The unit battery is a secondary battery which can be charged or discharged. The unit battery is a battery in which an electrode assembly with a separator interposed between first and second electrodes is sealed together with an electrolyte in a case  113 . The electrode assembly may be provided by stacking the first electrode, the separator, and the second electrode (hereinafter, referred to as a “stacked type”) or winding the stacked body (hereinafter, referred to as a “wound type”). The first and second electrodes have different polarities, e.g., the first electrode may be a positive electrode and the second electrode may be a negative electrode. 
     Also, the unit batteries  110 ,  110 A, and  110 B include first electrode terminals  111 ,  111   a , and  111   b , respectively, and second electrode terminals  112 ,  112   a , and  112   b , respectively. The first electrode terminals  111 ,  111   a , and  111   b , and the second electrode terminals  112 ,  112   a , and  112   b  are electrically connected to the first electrode and the second electrode and exposed from the case. 
       FIG. 5  is a perspective view schematically illustrating a wound type electrode assembly as an exemplary electrode assembly  119 . It is noted that  FIG. 5  illustrates the wound type electrode assembly  119  only as an example, and embodiments may also include a stacked type electrode assembly. 
     Referring to  FIG. 5 , the electrode assembly  119  may be provided by sequentially stacking a first electrode plate  116 , a separator  117 , and a second electrode plate  118 , followed by winding the same. The first electrode plate  116  serves as a first electrode, and the second electrode plate  118  serves as a second electrode. Also, the electrode assembly  119  may include an outwardly extending electrode tap  115 , and the electrode tap  115  may include a first electrode tap  115   a  electrically connected to the first electrode plate  116  and a second electrode tap  115   b  electrically connected to the second electrode plate  118 . The first and second electrode taps  115   a  and  115   b  may transmit electrochemical energy generated from the unit batteries to the outside. 
     Referring back to  FIG. 2 , the unit battery  110  may have an angular shape, e.g., a hexagonal shape, in which the case  113  has a predetermined thickness d. Thus, portions corresponding to the thickness of the unit battery  110  may be called edges, e.g., may include four sides, and two additional sides may be called both sides. That is, the both sides of the case  113  of the unit battery  110  may be two wide sidewalls, i.e., two sides of the case  113  that are parallel to a stacked plane in which the first electrode, the separator, and the second electrode of the electrode assembly are sequentially stacked. Further, the edges of the case  113  may be four narrow sidewalls, e.g., including top and bottom sides of the case  113 . As such, the first electrode terminal  111  and the second electrode terminal  112  protrude from an edge of the unit battery  110 , e.g., from a top side of the case  113 . In other words, the first electrode terminal  111  and the second electrode terminal  112  protrude from one edge, i.e., side, among the four edges of the case  113 . 
     For example, when the electrode assembly is a wound type electrode assembly, sides of the case  113  facing flat sides of the electrode assembly  119  are the both sides of the case  113 , and sides facing rounded corners of the electrode assembly  119  may be the edges of the case  113 . Also, when the electrode assembly is a stacked type electrode assembly, sides facing a stacked plane of the electrode assembly are the both sides of the case, and sides facing the sides providing a thickness or height of the stacked plane of the electrode assembly may be the edges of the case  113 . 
     Also, although not shown, the unit battery  110  may have an exhaust for discharging gas between the first electrode terminal  111  and the second electrode terminal  112 . 
     The unit battery  110  described above may be a battery having any configuration as long as it can react to an electrolyte to generate electrochemical energy. For example, the unit battery  110  may be a lithium polymer battery or a lithium ion battery. Specific components of the unit battery  110  are known, and thus, a detailed description thereof will be omitted. 
     As further illustrated in  FIG. 2 , the battery pack  100  may include a plurality of connection terminals  101  to connect the plurality of unit batteries  110  in series. For example, a first connection terminal  101 A electrically connects the second electrode terminal  112   a  of a first unit battery  110 A and the first electrode terminal  111   b  of a second unit battery  110 B adjacent to the first unit battery  110 A. In this manner, the plurality of unit batteries  110  may be connected in series. However, as described above, the present disclosure is not limited thereto, e.g., the plurality of unit batteries  110  may be connected in parallel or may be connected in series-parallel by the connection terminal  101 . 
     For example, referring to  FIG. 2 , the plurality of unit batteries  110  may be received. e.g., arranged, in three columns in the pack frame  120 . However, the number of columns is merely illustrative, and the unit batteries  110  may be arranged in an overlapping manner, e.g., with wide sides overlapping each other, in a first direction to provide at least one column. That is, the unit batteries  110  may be arranged in at least one column to be adjacent to each other along the first direction, such that the wide sides of the unit batteries  110  overlap each other. Here, the unit batteries  110  are arranged such that both sides thereof overlap each other. As described above, both sides of the unit battery  110  face the stacked plane of the electrode assembly. The first direction is a length direction of the column provided as the plurality of unit batteries  110  are arranged. 
     The pack frame  120  accommodates and protects the unit batteries  110 , and is detachably fixed to the rack housing  200 , such that the battery pack  120  may be received in the rack housing  200 . As illustrated in  FIG. 3 , the pack frame  120  may include a bottom surface  121 , a plurality of side walls  122 ,  123 ,  124 , and  125  extending upwardly from edges of the bottom surface  121  to provide the sides of the pack frame  120 , and a plurality of separation walls  128  and  129  provided between the side walls. 
     The pack frame  120  includes a space surrounded by the bottom surface  121  and the plurality of side walls, and accommodates the plurality of unit batteries  110  in the space. The plurality of side walls includes a first side wall  122 , a second side wall  124 , a third side wall  123 , and a fourth side wall  125 . The first and second side walls  122  and  124  are side walls facing wide sides of the unit battery  100 , i.e., the first and second side walls  122  and  124   a  face the both sides of the case  113 , and the third and fourth side walls  123  and  125  are side walls facing narrow sides of the unit battery  110 , i.e., the edges of the case  113 . 
     Insertion recesses  126  and  127  supported by the rack housing  200  are provided on the first and second side walls  122  and  124 . A first insertion recess  126  provided on the first side wall  122  and a second insertion recess  127  provided on the second side wall  124  have the same shape. Hereinafter, although only the first insertion recess  126  is described, the described features may also be applied to the second insertion recess  127 . 
     As illustrated in  FIG. 3 , the first insertion recess  126  extends across an outer surface of the first side wall  122 . Since the first and second side walls  122  and  124  are parallel to both sides of the unit battery  110 , the first and second insertion recesses  126  and  127  extend in a second direction perpendicular to the first direction, e.g., along the x-axis. In other words, the first and second insertion recesses  126  and  127  extend to be perpendicular to a length direction of the column provided as the unit batteries  110  are arranged. 
     The first and second insertion recesses  126  and  127  extend in a substantially central line of the unit battery cells  110 , e.g., each of the first and second insertion recesses  126  and  127  may be in respective centers of the first and second side walls  122  and  124  along the z-axis. The central line corresponds to a line dividing each of the both sides of the unit batteries into two halves, and the substantially central line is a line passing through a portion to which expansive force concentratedly is applied from both sides of the unit batteries  110 . However, the positions of the first and second insertion recesses  126  and  127  are not limited thereto. e.g., the first and second insertion recesses  126  and  127  may be provided to extend to be parallel to the central line and may be provided above or below the central line. 
     Also, in the present exemplary embodiment, one first insertion recess  126  and one second insertion recess  127  are provided. However, embodiments are not limited thereto. For example, a pair of first insertion recesses may extend to be parallel to each other and parallel to the central line and may be disposed above and below the central line interposed therebetween. Similarly, the second insertion recess may also be provided as a pair. In this manner, the disposition and number of the insertion recesses may be modified according to the positions in which the support member is coupled to the first and second side walls and the number of the support members in order to suppress swelling of the unit batteries. 
     As illustrated in  FIG. 3 , the first insertion recess  126  may be provided to have a predetermined depth on the outer surface of the first side wall  122 , and is open outwardly from the first side wall. The first insertion recess  126  extends to both corners where the first side  122  wall meets the third and fourth side walls  123  and  125 . Similarly, the second insertion recess  127  extends to both corners where the second side  124  wall meets the third and fourth side walls  123  and  125 . That is, each of the first and second insertion recesses  126  and  127  extends continuously along the entire first and second side wall  122  and  124 , respectively. Thus, both ends of the first and second insertion recesses  126  and  127  provide an opening in the corners of the third and fourth side walls  123  and  125 . 
     Through holes  123   a  and  125   a  are provided in the third and fourth side walls  123  and  125  to cool the unit batteries  110 , respectively. For example, as illustrated in  FIG. 3 , each of the through holes  123   a  and  125   a  extends continuously along the entire third and fourth side wall  123  and  125 , respectively. 
     As further illustrated in  FIG. 3 , the plurality of separation walls  128  and  129  separate the space of the pack frame  120  into a plurality of spaces to allow the unit batteries  110  to be accommodated in each space. Here, the plurality of separation walls  128  and  129  are provided to be spaced apart in a vertical direction such that the spaces communicate with each other, e.g., each one of the plurality of separation walls  128  and  129  includes at least two portions spaced apart from each other along the z-axis. By the plurality of separation walls  128  and  129 , the unit batteries  110  are stably accommodated, a cooling passage is provided, and the spaces of the pack frame  120  are firmly maintained. 
     In detail, the plurality of separation walls  128  and  129  include a plurality of first separation walls  128  extending in the first direction, e.g., along the y-axis, and a plurality of second separation walls  129  extending in the second direction, e.g., along the x-axis. Also, the first separation walls  128  extend from an inner surface of any one side wall among the first and second side walls  122  and  124  facing each other to an inner surface of the other side wall. The second separation walls  129  extend from an inner surface of any one side wall among the third and fourth side walls  123  and  125  facing each other to an inner surface of the other side wall. 
     The plurality of first separation walls  128  are members separating the spaces in the pack frame  120 , such that the plurality of unit batteries  110  are arranged in the first direction. For example, a first pair of first separation walls  128  may be fixed to be spaced apart from one another in a horizontal direction, e.g., along the x-axis, and abut an opening provided in an upper portion of the pack frame  120 , e.g., uppermost surfaces (edges) of the first separation walls  128  may be level with uppermost surfaces (edges) of the first and second side walls  122  and  124 . Similarly, a second pair of the first separation walls  128  may be fixed to be spaced apart from one another in the horizontal direction and abut on a bottom surface of the pack frame  120 , while being spaced apart from the first pair of first separation walls  128  along the z-axis. Here, the horizontal direction refers to a direction parallel to the bottom surface. The first and second pairs of the first separation walls  128  are provided above and below, respectively, separating the spaces of the pack frame  120  into three rows along the y-axis. However, as described above, the plurality of unit batteries  110  may be provided in any suitable number of columns, e.g., a first separation wall  128  is not provided when the plurality of unit batteries  110  is arranged as a single column. 
     The plurality of second separation walls  129  separate the spaces of each column in the pack frame  120  by a number of unit batteries provided in the column. Like the first separation walls  128 , a first plurality of second separation walls  129  may be provided to abut the upper opening of the pack frame  120 , and a second plurality of second separation walls  129  are provided to abut the bottom surface of the pack frame  120 . The second separation walls  129  are spaced apart from one another along the y-axis, such that a space sufficient for one unit battery  100  to be accommodated therein is secured. 
     The shape and disposition of the separation walls  128  and  129  are not limited thereto. Further, if necessary, the separation walls  128  and  129  may be omitted, or the separation walls  128  and  129  may be modified such that a plurality of unit batteries  110  are provided in one space. 
     Referring to  FIG. 4 , the rack housing  200  may be a cabinet accommodating a plurality of battery packs  100 , e.g., eight battery packs  100 , within a plurality of corresponding pack frames  120 . Further, the rack housing  200  may include a plurality of rack frame members and a plurality of support members  250  fixed to the rack frame members to support side walls of the pack frames  120 . 
     In detail, as illustrated in  FIG. 4 , the plurality of rack frame members may include a first frame  210  providing a bottom frame of the rack housing  200 , a second frame  220  extending in a vertical direction, e.g., along the z-axis, to provide a side frame of the rack housing  200 , and a third frame  230  providing an upper frame of the rack housing  200 . Also, the plurality of rack frame members may further include a fourth frame  240  fixed to the second frame  220  between the first frame  210  and the third frame  230  to firmly support a middle portion of the rack housing  200 . Here, the fourth frame  240  may have the same shape as that of the first and third frames  210  and  230 . 
     As illustrated in  FIG. 4 , the first frame  210  and the third frame  230  have the same shape and are provided on upper and lower portions of the rack housing  200 , respectively. The first and third frames  210  and  230  are frames having, e.g., rectangular, edges and middle portions thereof are open. However, the present disclosure is not limited thereto, e.g., the first and third frames  210  and  230  may have any configuration as long as it has functions of the upper frame and the lower surface of the rack housing  200 . 
     The second frame  220  may include a plurality of pillar members extending from the first frame  210  to the third frame  230 . The plurality of pillar members may include four corner pillars  221  extending to corresponding corners of the third frame  230  from the corners of the first frame  210 , and a pair of intermediate pillars  223  extending from the first frame  210  to the third frame  230 , and disposed between two corner pillars  221 . The pair of intermediate pillars  223  are provided on a side where the first and second side walls  122  and  124  of the battery pack are disposed. 
     The plurality of support members  250  are on the frame members of the rack housing  200 , e.g., the plurality of support members  250  may be on inner surfaces of the frame members, to support side walls of the battery packs  100 . That is, the battery packs  100  are fixed to the rack housing  200  via the support members  250 , e.g., fixed to the second frame  220  of the rack housing  200  via the support members  250 . A first side of the support member  250  facing the battery pack  100  is coupled to the side wall of the battery pack  100 , and a second (opposite) side of the support member  250  is fixed to the second frame. 
     The support member  250  is a planar member extending in the second direction, e.g., along the x-axis, and edges thereof in a width direction are bent in the first direction. However, the shape of the support member is not limited thereto, e.g., the support member may have any shape extending in the second direction. 
     The support member  250  includes a first support member  252  supporting the first side wall  122  of the battery pack  100  and a second support member  254  supporting the second side wall  124  of the battery pack  100 . The first and second support members  252  and  254  support across the outer surfaces of the first and second side walls  122  and  124  in the second direction, and are disposed in portions corresponding to central lines of both sides of the unit battery  110 . In detail, the first support member  252  is inserted from an outer surface of the first side wall  122  to the first insertion recess  126  to support the first side wall  122 . Similarly, the second support member  254  is inserted from an outer surface of the second side wall  124  to the second insertion recess  127  to support the second side wall  124 . 
     The position in which the support member  250  is inserted into a side wall of the battery pack  100  is not limited thereto and may be modified as described above in relation to the insertion recess. For example, the first and second support members  252  and  254  may support across the first and second side walls  122  and  124  in the second direction, respectively, and may be disposed to slightly deviate from the central lines of both sides of the unit battery  110 . Also, in the present embodiment, one first support member  250  is coupled to the first side wall  122  and one second support member  254  is coupled to the second side wall  124 . However, embodiments are not limited thereto, e.g., a pair of first support members  252  may be disposed on the first side wall  122  and slightly spaced apart from a central line in opposite directions, and a pair of second support members  254  may be disposed on the second side wall  124  and slightly spaced apart from a central line in opposite directions. 
       FIG. 6  is a view illustrating a state in which the battery pack  100  is installed in the rack housing  200 . A specific configuration of the support member  250  and a structure in which the battery pack  100  is installed in the rack housing  200  will be described in detail with reference to  FIG. 6 . 
     Referring to  FIG. 6 , the first support member  252  includes a planar body  256  inserted into the first insertion recess  126  and a pair of ribs  255   a  and  255   b  bent from respective edges of the body  256  outwardly and extending in the first direction. The second support member  254  has the same shape as that of the first support member  252 , and is inserted into the second insertion recess  127 . Hereinafter, the first support member  252  will be described in detail and this may also be applied in the same manner to the second support member  254 . 
     The body  256  is a planar member extending in the second direction, and has the same width as that of the first insertion recess  126  along the z-axis. The pair of ribs  255   a  and  255   b  are bent in the first direction, e.g., along the y-axis, from both edges of the body  256  in the width direction. The pair of ribs  255   a  and  255   b  extend outwardly, e.g., along the y-axis, and have the same thickness as that of the body. The pair of ribs  255   a  and  255   b  are fixed to the inner side of the second frame  220 , such that a portion of each of the ribs  255   a  and  255   b  has a width along the y-axis that equals at least the depth of the first insertion recess  126  and protrudes from the second frame  220 . In other words, as illustrated in  FIG. 6 , each of the ribs  255   a  and  255   b  extends from the inner side of the second frame  220  toward the interior of the rack housing  200  along the y-axis, such that both the ribs  255   a  and  255   b  may be inserted into a same first insertion recess  126  of the battery pack  100 . The ribs  255   a  and  255   b  are connected by the body  256  along the z-axis, such that the body  256  is inserted into the same first insertion recess  126  with the ribs  255   a  and  255   b . The pair of ribs  255   a  and  255   b  may be fixed to the second frame  220  by a fastening member, e.g., a bolt, or may be fixed to the second frame  220 , e.g., by welding, but the present disclosure is not limited thereto. 
     The first insertion recess  126  is a concave recess including three sides and having a predetermined depth, and a vertical cross-section thereof has a C shape (see portion A in  FIG. 6 ). The vertical cross-section refers to a cross-section perpendicular to the extending direction of the first insertion recess  126 . The shape of the vertical cross-section is provided such that the body  256  of the first support member  252  and a portion of the rib extending from the body  256  fit to the first insertion recess  126 . However, the shape of the vertical cross-section of the first insertion recess  126  is not limited thereto, and may have any shape in which the first support member  252  is slidably inserted therein. Similarly, the second insertion recess  127  may also have any shape in which the second support member  254  is slidably inserted therein. 
     As illustrated in  FIG. 6 , the first and second support members  252  and  254  are slidably inserted into the first and second insertion recesses  126  and  127 , respectively, through the opening provided in the corner of the fourth side wall  125 . In detail, for example, in case of the first support member  252 , the body  256  is in contact with a bottom surface of the insertion recess  126 , and the pair of ribs  255   a  and  255   b  are in contact with the other remaining two sides of the insertion recess  126 . The first and second support members  252  and  254  are inserted, e.g., pushed, until end portions thereof pass through, e.g., align with, the opening provided in the corner of the third side wall  123 . 
     Thus, when the battery pack  100  is completely received in the rack housing  200 , the first support member  252  extends from one corner of the first side wall  122  to the opposite corner thereof along the central line of the unit battery  110  across the outer surface of the first side wall  122 . Similarly, the second support member  254  extends from one corner of the second side wall  124  to the opposite corner thereof along the central line of the unit battery  110  across the outer surface of the second side wall  124 . In this manner, the first and second support members  252  and  254  are coupled to the side walls of the battery pack  110  to support the side walls. Since the plurality of support members  250  are slidably coupled to the first and second insertion recesses  126  and  127 , the battery pack  100  may be separated from the plurality of support members  250  in a sliding manner. 
       FIG. 7  is a top view illustrating a shape in which expansive force acts on the battery pack  100  in the arrow direction. A configuration for preventing swelling of the battery pack  100  installed in the rack housing  200  will be described in detail. 
     Referring to  FIG. 7 , when the unit battery  110  swells, expansive force acts on the outer side of the unit battery  100  in a direction (F) perpendicular, e.g., normal, to both sides of the unit battery  110 . Here, the direction perpendicular to both sides of the unit battery  110  is the same as the first direction, e.g., y-axis in  FIG. 2 . Thus, it may be considered that the expansive force F acts in parallel to the first direction and perpendicularly to the second direction. However, as the first and second support members  252  and  254  extend in the second direction, i.e., along the central line of the unit battery  110  to traverse the first side wall and the second side wall  122  and  124 , the unit battery  110  is restrained from expanding in the arrow direction (F) despite the expansive force. 
     The effect of the foregoing aspect will be described by using deformation as an example. For example, deformation, e.g., a degree of deformation due to the expansive force in the direction F, of a pack frame before being installed in the rack housing  200  ranged from about 0.8 mm to 1.2 mm. After installation of the pack frame in the rack housing  200 , followed by application of a same expansive force in the direction F on the pack frame, deformation was measured in a range from about 0.2 mm to 0.8 mm. Also, in a state in which the pack frame is installed, a degree of deformation of the vicinity of the support members and around the support members of the rack housing due to the expansive force F was measured to range from about 0.2 mm to 0.8 mm. 
       FIG. 8  is a partial cross-sectional view illustrating a state in which a modified embodiment of a pack frame is installed in the rack housing  200 . The portion illustrated in  FIG. 8  is a cross-sectional view of corresponding to the portion A of  FIG. 6 . 
     Referring to  FIG. 8 , the insertion recess  126  provided on a first side wall  122 ′ of a pack frame according to the modified embodiment is provided through pressing. Thus, while the shape of the insertion recess  126  is the same as that described previously with reference to  FIG. 3 , but the shape of the cross-section of the first side wall  122 ′ is different from the first side wall  122  in  FIG. 3 . That is, in the case of the embodiment of  FIG. 6 , a thickness of a portion of the first side wall  122  where the first insertion recess  126  is provided is smaller than the thickness of the other remaining portion. However, in the embodiment of  FIG. 8 , a portion of the first side wall  122 ′ where the first insertion recess  126  is provided has the same thickness as that of the other remaining portion. Other portions are the same as those of the embodiment described above. Similarly, the second insertion recess of the second side wall may also be provided through pressing. 
       FIG. 9  is a perspective view illustrating a shape in which the battery pack  100  is installed in a rack housing according to another embodiment. In the embodiment of  FIG. 9 , a shape of a cross-section of a plurality of support members is different, as compared to components described above with reference to  FIGS. 1 through 8 . 
     Referring to  FIG. 9 , a plurality of support members  252 ′ and  254 ′ are provided as members having a body with a quadrangular bar shape extending in the second direction. That is, a vertical cross-section of the plurality of support members  252 ′ and  254 ′ has a rectangular shape. A shape of the plane where the support members  252 ′ and  254 ′ are in contact with the insertion recess is the same as that of the embodiment described above. The plurality of support members are slidably inserted into the insertion recesses  126  and  127 , respectively, as described above. The other portions are the same as those described above, and thus, a detailed description thereof will be omitted. 
       FIG. 10  is a view illustrating a modified embodiment in which a shape of an insertion recess and a shape of a plurality of support members  252 ″ and  254 ″ is modified. Referring to  FIG. 10 , an insertion recess  126 ′ provided on the first side wall  122  is provided as a single concave curved surface. The insertion recess  126 ′ extends from one corner of the first side wall  122  to the corner of the other side in the second direction and the curved surface faces the first support member  252 ″. The insertion recess  126 ′ extends along a central line of the side of the unit battery  110 . An insertion recess  127 ′ is provided on the second side wall  125  and has the same shape. The insertion recesses  126 ′ and  127 ′ according to the modified embodiment have the same function and effect as those of the embodiment described above, except that they are provided as curved surfaces, and a further detailed description thereof will be omitted. 
     The first support member  252 ″ is provided as a body having a curved surface provided to be convex with the same curvature as that of the curved surface of the insertion recess  126 ′. In  FIG. 10 , the first support member is illustrated as a member having a plate shape, but the embodiments are not limited thereto and the first support member may have a shape of a pipe or a circular bar shape having an outer diameter with the same curvature as that of the curved surface of the insertion recess. The second support member  254 ″ may be provided in the same manner as that of the first support member and inserted into the insertion recess  127 ′. The other components are the same as those of the embodiment described above, and thus, a detailed description thereof will be omitted. 
     By way of summation and review, according to embodiments, an energy storage device includes a rack housing capable of firmly supporting a battery pack. That is, since the support member supports the side wall of the battery pack in the second direction across the side wall, expansive force acting on the battery pack in the first direction may be restrained. 
     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.