Patent Publication Number: US-2021184189-A1

Title: Battery stack and battery module employing battery stack

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2019-224461 filed on Dec. 12, 2019, the disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a battery stack and a battery module employing this battery stack. 
     Related Art 
     The battery module described in Japanese Patent Application Laid-Open (JP-A) No. 2017-201587 is provided with a lower face case that houses battery cells configuring part of a battery stack. The lower face case is capable of housing the battery cells individually, and covers outer faces of the battery cells. Moreover, an exposing portion to expose the battery cells is locally formed in the lower face case. An external cooling device or coolant contacts the battery cells through this exposing portion to enable the battery cells to be cooled. 
     However, in JP-A No. 2017-201587, an external cooling device or coolant is required in order to cool the battery cells, complicating the battery stack. There is accordingly further room for improvement with regard to battery stack heat dissipation measures. 
     SUMMARY 
     In consideration of the above circumstances, an object of the present disclosure is to obtain a battery stack and a battery module employing this battery stack that are capable of improving heat dissipation performance with a simple structure for plural battery cells applied with waterproofing measures. 
     A battery stack according to a first aspect of the present disclosure includes plural battery cells that have been waterproofed, that are arrayed along a horizontal direction, and that each has a length direction running in a direction orthogonal to an array direction of the battery cells; and plural resin frames that are respectively provided between mutually adjacent battery cells, that support both length direction end portions of the battery cells, and that form an opening that exposes lower faces of the battery cells. 
     The battery stack according to the first aspect of the present disclosure is configured including the plural battery cells and the plural resin frames. The battery cells are applied with waterproofing measures, arrayed along the horizontal direction, and have their length direction running in a direction orthogonal to the array direction. 
     The resin frames are respectively provided between mutually adjacent of the battery cells, support both the length direction end portions of the battery cells, and form the opening that exposes the lower faces of the battery cells. 
     Namely, lower walls of the resin frames may for example be configured by a pair of support portions that support both the length direction end portions of the battery cells, and the opening may be formed between the support portions. The lower faces of the battery cells are thus exposed through the opening at regions other than both the length direction end portions of the battery cells. 
     Thus, in the present disclosure, the battery cells applied with waterproofing measures can be cooled from the lower face side of the battery cells through the opening formed in the resin frames. This enables a battery stack to be obtained in which heat dissipation performance is improved with a simple structure applied with waterproofing measures. 
     A battery stack according to a second aspect of the present disclosure is the battery stack according to the first aspect, wherein each of the resin frames includes: a rectangular, plate-shaped body disposed between mutually adjacent battery cells; a pair of sidewalls provided at both length direction ends of the body so as to be capable of abutting both length direction ends of one of the mutually adjacent battery cells; and a pair of support portions that are bent to follow the horizontal direction from lower ends of the sidewalls so as to support, and abut lower faces of both length direction end portions of, the one of the mutually adjacent battery cells. 
     In the battery stack according to the second aspect of the present disclosure, each of the resin frames is configured including the body, the pair of sidewalls, and the pair of support portions. The body has a rectangular plate shape and is disposed between the mutually adjacent battery cells. The pair of sidewalls are provided at both the length direction ends of the body so as to be capable of abutting both the length direction ends of the corresponding battery cell. 
     The pair of support portions are bent to follow the horizontal direction from the lower ends of the sidewalls so as to abut the lower faces of both the length direction end portions of the corresponding battery cell and be capable of supporting the battery cell. Namely, the opening is formed in each of the resin frames between leading ends of the support portions, and the lower face of the corresponding battery cell is exposed through this opening. 
     A battery stack according to a third aspect of the present disclosure is the battery stack according to the second aspect, further including a reference face-opposing face that is provided at one sidewall of the pair of sidewalls and that is formed with a biasing portion to bias the one of the mutually adjacent battery cells toward another sidewall of the pair of sidewalls; and a reference face that is provided at the other sidewall so as to be abutted by one length direction end portion of the one of the mutually adjacent battery cells, wherein of the pair of support portions, a length of one support portion formed on one sidewall side is set so as to be longer than a length of another support portion formed on another sidewall side. 
     In the battery stack according to the third aspect of the present disclosure, the biasing portion is formed to the one sidewall out of the pair of sidewalls of each of the resin frames, and the corresponding battery cell is biased toward the other sidewall out of the pair of sidewalls by the biasing portion. 
     The reference face that is abutted by the one length direction end portion of the battery cell is provided to the other sidewall, and the one sidewall includes the reference face-opposing face. The length of the one support portion formed on the one sidewall side is set so as to be longer than the length of the other support portion formed on the other sidewall side. 
     As described above, the pair of support portions of the resin frame respectively support both the length direction end portions of the corresponding battery cell. Thus, increasing an overlap amount between the support portions and the battery cell improves the support strength with which the battery cell is supported. On the other hand, increasing the overlap amount between the support portions and the battery cell decreases the area of the opening that exposes the lower face of the battery cell, with the result that cooling performance of the battery cell could suffer. 
     Thus, in the present disclosure, first, the one sidewall of each of the resin frames is provided with the biasing portion that biases the battery cell toward the other sidewall, such that the one length direction end portion of the battery cell abuts the reference face of the other sidewall. Thus, out of the pair of support portions, the overlap amount on the one support portion side (reference face-opposing face side) is smaller than that on the other support portion side (reference face side). 
     In cases in which the overlap amount between a support portion of the resin frame and the battery cell is small, the support strength offered to the battery cell by the support portion might be insufficient, such that the battery cell might slip from the support portion. This would be detrimental to the positional precision of the lower face of the battery cell. 
     Thus, in the present disclosure, the length of the one support portion on the reference face-opposing face side is set so as to be longer than the length of the other support portion on the reference face side. The present disclosure thereby enables the overlap amount with the battery cell to be secured on the one support portion side where the overlap amount would otherwise be smaller. Namely, in the present disclosure, support strength is ensured on the one support portion side where the overlap amount with the battery cell would otherwise be smaller, enabling the positional precision of the lower face of the battery cell to be improved. 
     Only the length of the one support portion is set so as to be longer in order to secure the overlap amount with the battery cell. This suppresses narrowing of a separation distance between the leading ends of the support portions, enabling the opening area in the resin frame to be maintained. Accordingly, in the present disclosure, the overlap amount between the resin frames and the battery cells is secured, while the exposed area of the lower faces of the battery cells is also secured by maintaining the opening area in the resin frames, enabling a drop in the cooling efficiency of the battery cells to be suppressed. 
     A battery module according to a fourth aspect of the present disclosure includes the battery stack of any one of the first to the third aspect; and a housing case in which the battery stack is housed in a waterproofed state, and that is provided with a heatsink to dissipate heat passing through the lower faces of the battery cells, which has been generated by the battery cells. 
     The battery module according to the fourth aspect of the present disclosure includes the battery stack and the housing case, and the battery stack is housed in the housing case in a state applied with waterproofing measures. The housing case is provided with the heatsink to dissipate heat passing through the lower faces of the battery cells that was generated by the battery cells. 
     As described above, the battery stack of the first aspect of the present disclosure exhibits an excellent advantageous effect of enabling heat dissipation performance to be improved with a simple structure for plural battery cells applied with waterproofing measures. 
     The battery stack of the second aspect of the present disclosure exhibits an excellent advantageous effect of enabling the opening to be provided in the resin frames that support the battery stacks, such that heat from the battery cells can be dissipated through the opening. 
     The battery stack of the third aspect of the present disclosure exhibits excellent advantageous effects of enabling the support strength of the battery stack by the resin frames to be secured, and enabling a drop in the cooling efficiency of the battery cells to be suppressed. 
     The battery module of the fourth aspect of the present disclosure exhibits an excellent advantageous effect of enabling heat dissipation performance to be improved with a simple structure for plural battery cells applied with waterproofing measures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a cross-section illustrating a battery stack and a housing case configuring parts of a battery module according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a perspective view illustrating a battery stack configuring part of a battery module according to an exemplary embodiment of the present disclosure, as viewed from an oblique lower side; 
         FIG. 3  is a is a perspective view illustrating a battery stack and a housing case configuring parts of a battery module according to an exemplary embodiment of the present disclosure; 
         FIG. 4  is a perspective view illustrating a state in which a battery stack configuring part of a battery module according to an exemplary embodiment of the present disclosure is housed in a housing case; 
         FIG. 5  is a perspective view illustrating battery cell and a resin frame configuring parts of a battery stack according to an exemplary embodiment of the present disclosure; 
         FIG. 6  is an enlarged cross-section of relevant portions to illustrate a positional relationship in a height direction between battery cells configuring parts of a battery stack according to an exemplary embodiment of the present disclosure and a bottom wall of a housing case; 
         FIG. 7  is a graph comparing distances from a bottom wall face of a bottom wall of a housing case at a reference face-opposing face side and a reference face side of a battery cell configuring part of a battery stack according to an exemplary embodiment of the present disclosure; 
         FIG. 8A  and  FIG. 8B  are comparative examples relating to  FIG. 8C ; and 
         FIG. 8C  is a side view schematically illustrating a resin frame and a battery cell configuring parts of a battery stack according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Explanation follows regarding a battery stack  12  according to an exemplary embodiment of the present disclosure, with reference to the drawings. 
     Note that in the drawings, the arrow UP, the arrow L, and the arrow W respectively indicate an upward direction, a length direction, and a width direction of a battery module  10  according to the present exemplary embodiment, as appropriate. 
     Battery Module Configuration 
     First, explanation follows regarding configuration of the battery module  10  according to the present exemplary embodiment of the present disclosure. 
     As illustrated in  FIG. 3 , in the present exemplary embodiment, the battery module  10  includes the battery stack  12  and a housing case  14 . As illustrated in  FIG. 4 , the battery stack  12  is housed inside the housing case  14 . 
     As illustrated in  FIG. 3  and  FIG. 5 , the battery stack  12  is configured including plural battery cells  16  and plural resin frames  18 . Each of the battery cells  16  has a flattened rectangular block shape, and the plural battery cells  16  are arrayed along a width direction of the battery cells  16 , this being orthogonal to a length direction of the battery cells  16 . The plural battery cells  16  are arranged along a horizontal direction. Note that the battery cells  16  are applied with waterproofing measures. 
     Each of the battery cells  16  is, for example, a rechargeable battery capable of being charged and discharged, and may, for example, be a rechargeable lithium ion battery. The battery cells  16  are angular batteries with a flattened rectangular block shape. Note that there is no limitation to rechargeable lithium ion batteries, and the battery cells  16  may be another type of battery, such as rechargeable nickel-hydrogen batteries. 
     An upper face  16 A of each of the battery cells  16  is provided with a positive terminal  16 B and a negative terminal  16 C, each terminal having a circular column shape. The battery cells  16  are arrayed such that the orientations of the positive terminal  16 B and the negative terminal  16 C are arranged alternately in the length direction of the battery stack  12  (array direction of the battery cells  16 , arrow L direction). The positive terminals  16 B and the negative terminals  16 C of mutually adjacent battery cells  16  in the length direction of the battery stack  12  are connected to each other through a non-illustrated bus bar, this being a conductive member. 
     The resin frames  18  are disposed between the mutually adjacent battery cells  16 . Namely, the battery stack  12  is configured with an alternating array of the battery cells  16  and the resin frames  18 . The resin frames  18  are, for example, formed from a resin such as polypropylene, and are disposed as insulating members between the respective battery cells  16 . 
     In this alternating array of the battery cells  16  and the resin frames  18 , the battery cells  16  and the resin frames  18  are applied with pressure along the array direction of the battery cells  16  by pressure-application bands  19  disposed at both length direction end portions and above and below the respective battery cells  16 . This maintains inter-particle ionic conductivity in the electrolytic material, thereby maintaining battery performance of the battery stack  12 . 
     As illustrated in  FIG. 5 , each of the resin frames  18  is configured including a body  20 , a pair of sidewalls  22 ,  24 , and a pair of support portions  26 ,  28 . The body  20  is formed in a rectangular plate shape, and is disposed between the mutually adjacent battery cells  16 . The respective sidewalls  22 ,  24  are provided at both length direction ends of the body  20 . The respective sidewalls  22 ,  24  jut out from side ends of the body  20 . 
     Accordingly, in a state in which the body  20  of a given resin frame  18  is adjacent to a corresponding battery cell  16 , a sidewall face  32  provided at one length direction end portion  30  of the battery cell  16  is capable of abutting one the sidewalls of the resin frame  18 , namely the sidewall  22 , while a sidewall face  36  provided at another length direction end portion  34  of the battery cell  16  is capable of abutting the other sidewall of the resin frame  18 , namely the sidewall  24 . 
     The respective support portions  26 ,  28  extend from lower ends of the sidewalls  22 ,  24  of the resin frame  18  so as to be contiguous to the body  20  and bend toward directions approaching each other. The support portions  26 ,  28  are abutted by a lower face  38  of the battery cell  16 , and both the length direction end portions  30 ,  34  of the battery cells  16  are respectively supported by the support portions  26 ,  28 . 
     Namely, in the present exemplary embodiment, an opening  40  is formed between a leading end  26 A of one of the support portions, namely the support portion  26 , and a leading end  28 A of the other of the support portions, namely the support portion  28 . The lower face  38  of the battery cell  16  is capable of being exposed through the opening  40 . 
     As illustrated in  FIG. 2 , the openings  40  are formed so as to be contiguous to one another along the array direction of the battery cells  16 . Accordingly, a lower portion  12 A of the battery stack  12  is formed with a large opening  41  formed by the contiguous openings  40 . 
     Moreover, as illustrated in  FIG. 5 , the sidewall  22  of each of the resin frames  18  is provided with a lip (biasing portion)  42  opposing the sidewall  24 . The lip  42  biases the battery cell  16  toward the sidewall  24  in a state in which the battery cell  16  is being supported by the resin frame  18 . 
     The sidewall face  36  of the battery cell  16  accordingly abuts the sidewall  24  of the resin frame  18 . A face of the sidewall  24  of the resin frame  18  that is abutted by the sidewall face  36  of the battery cell  16  in this manner is referred to as a reference face  44 , and a face on the sidewall  22  side of the resin frame  18  is referred to as a reference face-opposing face  46 . 
       FIG. 3  is a perspective view illustrating the battery stack  12  and the housing case  14  configuring parts of the battery module  10 . As illustrated in  FIG. 3 , the housing case  14  is box shaped, and is open at an upper side. The housing case  14  is formed of die-cast aluminum or the like, and as illustrated in  FIG. 4 , the battery stack  12  is housed inside a housing area  15  of the housing case  14 . 
     In a state in which the battery stack  12  is housed inside the housing case  14  in this manner, a cover  48  is fixed to the housing case  14  as illustrated in  FIG. 1 . Note that  FIG. 1  is a cross-section illustrating the battery module  10 . 
     As illustrated in  FIG. 1 , a non-illustrated sealing member is provided between the cover  48  and the housing case  14 , and the battery stack  12  is housed inside the housing case  14  in a sealed state. Moreover, in the housed state of the battery stack  12  inside the housing case  14 , the battery stack  12  is placed on a bottom wall  14 A of the housing case  14 . 
     Note that  FIG. 7  is a graph illustrating a comparison between distances from a bottom wall face  14 A 1  of the bottom wall  14 A of the housing case  14  on the one length direction end portion  30  side of the battery cells  16  (the reference face-opposing face  46  side) and the other length direction end portion  34  side of the battery cells  16  (the reference face  44  side). 
     As illustrated in  FIG. 7 , the distance from the bottom wall face  14 A 1  of the bottom wall  14 A of the housing case  14  is shorter on the reference face-opposing face  46  side of the battery cells  16  illustrated in  FIG. 1  than on the reference face  44  side of the battery cells  16 . Namely, the reference face-opposing face  46  side of the battery cells  16  hangs further toward a lower side than the reference face  44  side of the battery cells  16 . 
     Accordingly, in the present exemplary embodiment, as illustrated in  FIG. 5 , a length L 1  of the support portions  26  is set so as to be longer than a length L 2 (&lt;L 1 ) of the support portions  28 , such that the one length direction end portions  30  of the battery cells  16  are reliably supported by the support portions  26 . 
     In the present exemplary embodiment, as illustrated in  FIG. 1 , the bottom wall  14 A of the housing case  14  is coated with heat dissipation grease  50 . The heat dissipation grease  50  is thus interposed between the battery stack  12  and the housing case  14  when the battery stack  12  is placed on the bottom wall  14 A of the housing case  14 . 
     As described above, the battery cells  16  are supported by the support portions  26 ,  28  of the respective resin frames  18 , and the lower faces  38  of the battery cells  16  are in a state contacting upper faces  26 B of the respective support portions  26  and upper faces  28 B of the respective support portions  28 . 
     Strictly speaking, height differences thereby emerge between the lower faces  38  of the battery cells  16  and lower faces  26 C of the support portions  26 , and also between the lower faces  38  of the battery cells  16  and lower faces  28 C of the support portions  28 . Accordingly, in the present exemplary embodiment, the heat dissipation grease  50  is coated at a thickness that is set in advance so as to absorb these height differences. 
       FIG. 6  is an enlarged cross-section illustrating relevant portions in order to illustrate a positional relationship between the battery cells  16  and the bottom wall  14 A of the housing case  14  in the height direction. As illustrated in  FIG. 6 , in an arrayed state of the plural battery cells  16 , when the battery cells  16  are viewed from the one length direction ends of the battery cells  16 , variation in the region of several μm to around a dozen μm arises between the height direction positions of the lower faces  38  of the battery cells  16 . The heat dissipation grease  50  is thereby set with a coating thickness that takes this variation into consideration. The lower faces  38  of the battery cells  16  accordingly contact the heat dissipation grease  50  reliably. 
     Moreover, as illustrated in  FIG. 1 , in the present exemplary embodiment, a heatsink  52  is attached to the bottom wall  14 A of the housing case  14  on the outer side of the housing case  14 . The heatsink  52  is formed from a metal with good thermal conductivity, such as aluminum or ferrous metal. 
     The heatsink  52  is configured including a plate shaped base  52 A that makes face-to-face contact with the bottom wall  14 A of the housing case  14 , fixing portions  52 B that are fixed to the housing case  14 , and a fin section  52 C that hangs downward from the base  52 A. 
     The fin section  52 C is formed by plural elongated plate shaped fins  52 C 1  that extend along the array direction of the battery cells  16 . The fins  52 C 1  are arranged at a predetermined pitch along the length direction of the resin frames  18  of the battery cells  16 . Note that the pitch of the fins  52 C 1  is set as small as possible in order to increase the surface area of the heatsink  52 . 
     Operation and Advantageous Effects of Battery Module 
     Explanation follows regarding operation and advantageous effects of the battery module  10  according to an exemplary embodiment of the present disclosure. 
     As illustrated in  FIG. 2  and  FIG. 5 , in the present exemplary embodiment, the opening  40  is formed in each of the resin frames  18  provided between mutually adjacent battery cells  16  in the battery stack  12 . The opening  40  is formed between the leading end  26 A of the support portion  26  and the leading end  28 A of the support portion  28  that are bent toward mutually approaching directions from the lower ends of the sidewalls  22 ,  24  of the resin frame  18 . 
     The lower faces  38  of the battery cells  16  are thus exposed through the openings  40  at regions other than both the length direction end portions  30 ,  34  of the battery cells  16 . In the present exemplary embodiment, the plural battery cells  16  are arrayed along the length direction of the battery stack  12 . Accordingly, the lower portion  12 A of the battery stack  12  is formed with the large opening  41  formed by the contiguous openings  40 . The battery cells  16  can accordingly be cooled from the lower face  38  side of the battery cells  16  through the large opening  41 . 
     Namely, in the present exemplary embodiment, the battery cells  16  applied with waterproofing measures can be cooled through the large opening  41  formed by the contiguous openings  40  that expose regions at the lower faces  38  of the battery cells  16  other than both the length direction end portions  30 ,  34  of the battery cells  16 . This thereby enables the heat dissipation performance of the battery cells  16  to be improved by a simple structure. 
     Note that as illustrated in  FIG. 1 , in the present exemplary embodiment, the bottom wall  14 A of the housing case  14  is coated with the heat dissipation grease  50 , and the battery stack  12  is placed on the bottom wall  14 A of the housing case  14  such that the heat dissipation grease  50  is interposed between the battery stack  12  and the bottom wall I  4 A. The heatsink  52  is provided to the bottom wall  14 A of the housing case  14  on the outside of the housing case  14 . 
     More specifically, in the present exemplary embodiment, the lower faces  38  of the battery cells  16  contact the heat dissipation grease  50  coated on the bottom wall  14 A of the housing case  14 , and the base  52 A of the heatsink  52  is in face-to-face contact with the bottom wall  14 A of the housing case  14 . 
     Accordingly, in the present exemplary embodiment, heat from the battery cells  16  is transmitted in sequence through the lower faces  38  of the battery cells  16 , the heat dissipation grease  50 , the bottom wall  14 A of the housing case  14 , and the base  52 A of the heatsink  52 . Namely, in the present exemplary embodiment, a thermal conductance path is secured between the battery cells  16 , the heat dissipation grease  50 , the housing case  14 , and the heatsink  52 , enabling heat emitted from the battery cells  16  to be dissipated via the fin section  52 C of the heatsink  52 . 
     As described above, in the present exemplary embodiment, the heat dissipation grease  50  is provided between the lower faces  38  of the battery cells  16  and the bottom wall  14 A of the housing case  14  so as to achieve a setting in which the heat from the battery cells  16  is transmitted to the bottom wall  14 A side of the housing case  14  through the heat dissipation grease  50 . 
     Note that as illustrated in  FIG. 6 , since in the present exemplary embodiment variation in the region of from several μm to around a dozen μm emerges in the height direction positions of the lower faces  38  of the battery cells  16  in a state in which plural of the battery cells  16  are arrayed, the coating thickness of the heat dissipation grease  50  is set in advance in consideration of this variation. The present exemplary embodiment is thus set such that the lower faces  38  of the battery cells  16  reliably contact the heat dissipation grease  50 . 
     Moreover, as illustrated in  FIG. 1 , the base  52 A of the heatsink  52  makes face-to-face contact with the outside of the bottom wall  14 A of the housing case  14 . Namely, in the present exemplary embodiment, no gaps are formed between the battery cells  16 , the heat dissipation grease  50 , and the heatsink  52 . The present exemplary embodiment thus enables the battery cells  16  to be effectively cooled while suppressing cooling loss. 
     As illustrated in  FIG. 5 , in the present exemplary embodiment, the support portions  26 ,  28  of the resin frames  18  support both the length direction end portions  30 ,  34  of the respective battery cells  16 . As a general rule, increasing the overlap amount between the support portions  26 ,  28  and the battery cells  16  improves the support strength with which the battery cells  16  are supported. 
     On the other hand, increasing the overlap amount between the support portions  26 ,  28  and the battery cells  16  decreases the area of the openings  40  that expose the lower faces  38  of the battery cells  16 , with the result that cooling performance of the battery cells  16  could suffer. 
     Accordingly, in the present exemplary embodiment, the sidewall  22  of each of the resin frames  18  is provided with the lip  42  that biases the corresponding battery cell  16  toward the sidewall  24 , such that the other length direction end portion  34  of the battery cell  16  abuts the reference face  44  of the sidewall  24 . A gap  54  (see  FIG. 8C ) is thus formed between the reference face-opposing face  46  provided to the sidewall  22  of the resin frame  18  and the one length direction end portion  30  of the battery cell  16 . 
       FIG. 8A  illustrates a comparative example in which the overlap amounts between the pair of support portions  26 ,  28  and the battery cell  16  are set such that the overlap amount with the battery cell  16  on the support portion  26  side (reference face-opposing face  46  side) is smaller than that on the support portion  28  side (reference face  44  side). 
     In such cases in which the overlap amount between the support portion  26  of the resin frame  18  and the battery cell  16  is small, the support strength offered to the battery cell  16  by the support portion  26  might be insufficient, such that the battery cell  16  might slip from the support portion  26 . This would be detrimental to the positional precision of the lower face  38  of the battery cell  16 . 
       FIG. 8B  illustrates a comparative example for the purpose of examining a case in which the overlap amounts between the support portions  26 ,  28  and the battery cell  16  are increased. In this case, although the support strength with which the battery cell  16  is supported is improved, there is a commensurate decrease in the area of the opening  40  that exposes the lower face  38  of the battery cell  16 . This might result in a drop in the cooling performance of the battery cell  16 . 
     Accordingly, in the present exemplary embodiment, out of the pair of support portions  26 ,  28 , the length L 1  of the support portion  26  formed on the sidewall  22  side is set so as to be longer than the length L 2 (&lt;L 1 ) of the support portion  28  formed on the sidewall  24  side. 
     As illustrated in  FIG. 8C , the present exemplary embodiment thereby enables the overlap amount with the battery cell  16  to be secured on the support portion  26  side where the overlap amount would otherwise be smaller. As a result, support strength is ensured on the support portion  26  side where the overlap amount with the battery cell  16  would otherwise be smaller, enabling the positional precision of the lower face  38  of the battery cell  16  to be improved. 
     In the present exemplary embodiment, only the length L 1  of the support portion  26  is set so as to be longer in order to secure the overlap amount with the battery cell  16  at the support portion  26  (on the reference face-opposing face  46  side). This suppresses narrowing of a separation distance L 3  between the leading end  26 A of the support portion  26  and the leading end  28 A of the support portion  28 , enabling the opening area to be maintained. 
     Accordingly, in the present exemplary embodiment, the overlap amount between the resin frames  18  and the battery cells  16  is secured, while the exposed area of the lower faces  38  of the battery cells  16  is also maintained, enabling a drop in the cooling efficiency of the battery cells  16  to be suppressed. 
     Note that in the present exemplary embodiment, setting the length L 1  of the support portion  26  longer than the length L 2  of the support portion  28  secures the overlap amount with the battery cell  16  on the support portion  26  side. However, there is no limitation thereto as long as the battery cell  16  can be prevented from slipping from the support portion  26 . 
     For example, the surface frictional coefficient on the support portion  26  side may be increased, for example by applying surface roughening, to discourage the battery cell  16  from slipping from the support portion  26 . 
     In the present exemplary embodiment, the support portions  26 ,  28  extend from the respective lower ends of the sidewalls  22 ,  24  so as to be contiguous to the body  20  of the resin frame  18 . However, it is sufficient that both the length direction end portions  30 ,  34  of the battery cells  16  be supported by the support portions  26 ,  28 . Accordingly, as long as the support portions  26 ,  28  are capable of ensuring the required rigidity, the support portions  26 ,  28  do not necessarily need to be contiguous to the body  20 . Namely, there is no need for width dimensions of the support portions  26 ,  28  to be substantially the same as a width direction dimension of the battery cell  16 . 
     Although explanation has been given regarding one example of an exemplary embodiment of the present disclosure, various modifications may be implemented within a range not departing from the spirit of the present disclosure. Obviously, the scope of rights encompassed by the present disclosure is not limited to the exemplary embodiment described above.