Patent Publication Number: US-2023133221-A1

Title: Battery pack

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage Application of International Application No. PCT/JP2021/013235, filed on Mar. 29, 2021, and is based upon and claims benefit of priority from Japanese Patent Application No. 2020-076589, filed on Apr. 23, 2020, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates to a battery pack. 
     Conventionally, a battery pack including a plurality of batteries housed in a case is known. The battery pack needs to dissipate heat generated by each of the plurality of batteries to an outside of the battery pack. For example, Patent Literature  1  discloses a temperature management system which includes thermally conductive members in contact with each of the plurality of batteries aligned in two rows, and dissipates heat of the batteries to an outside by a refrigerant flowing inside the thermally conductive members. Furthermore, Patent Literature 2 discloses a battery module which dissipates heat generated by cylindrical batteries to an outside by using a thermally conductive material filled between the plurality of cylindrical batteries. Furthermore, Non-Patent Literature 1 discloses a heat management system in which both end parts of thermally conductive members in contact with each of a plurality of batteries are connected with a case, and which dissipates heat generated by the batteries to an outside. 
     Patent Literature 
     Patent Literature 1: US 2011/0212356 A1 
     Patent Literature 2: JP 2018-060594 A 
     Non-Patent Literature 
     Non-Patent Literature 1: Suman Basu et al., Applied Energy 181, 1-13 (2016) 
     SUMMARY 
     However, the above prior arts still have a room for improvement to improve cooling efficiency of batteries of a battery pack while reducing manufacturing cost of the battery pack. According to, for example, a technique disclosed in Patent Literature 1, the refrigerant which cools the batteries flows inside the thermally conductive members, and then flows in flow passages formed inside a case. Hence, the thermally conductive members and the case need to be connected so as not to cause leakage of a liquid. Hence, the thermally conductive members need to be precisely manufactured, and manufacturing cost is high. Furthermore, according to a technique disclosed in Patent Literature 2, it is necessary to fill the thermally conductive material between the plurality of cylindrical batteries without gaps. This filling process requires a time. Therefore, manufacturing cost increases. Furthermore, in a case where the thermally conductive material is not sufficiently filled between the plurality of cylindrical batteries, cooling efficiency is concerned to lower. Furthermore, according to a technique disclosed in Non-Patent Literature 1, in a case where the length of the thermally conductive member is shorter than an internal dimension of the case due to a manufacturing error, the both end parts of the thermally conductive member cannot be connected with the case. Therefore, heat of the batteries is hardly dissipated at the end parts which are not connected with the case. Therefore, it is concerned that cooling efficiency varies between the different batteries, and it is not possible to obtain desired cooling efficiency. 
     The present disclosure has been made to handle with at least part of the above-described issue, and an object of the present disclosure is to provide a technique which improves cooling efficiency of batteries of a battery pack while reducing manufacturing cost of the battery pack. 
     The present disclosure has been made to solve at least part of the above-described issue, and can be realized as following aspects. 
     (1) One aspect of the present disclosure provides a battery pack. This battery pack includes: a plurality of batteries; a thermally conductive member which is in contact with the plurality of batteries; and a case which houses the plurality of batteries and the thermally conductive member. The case includes a holding part which is not in contact with an end surface of the thermally conductive member. The holding part regulates displacement of two surfaces of the thermally conductive member in a direction vertical to each of the two surfaces which are connected with the end surface and positioned on opposite sides. The holding part is in contact with at least one of the two surfaces. The holding part thereby holds an end part of the thermally conductive member. 
     According to this aspect, it is possible to transfer, to the case, heat generated by the batteries through the thermally conductive member in contact with the batteries, and the holding part in contact with at least one of the two surfaces of the thermally conductive member. Furthermore, even in a case where a position of the end surface of the thermally conductive member with respect to the holding part is displaced from a designed position due to a manufacturing error of one or both of the thermally conductive member and the case, it is possible to regulate the displacement in the direction vertical to each of the two surfaces of the end part of the thermally conductive member, and transfer to the case the heat generated by the batteries through the holding part in contact with at least one of these two surfaces. 
     (2) The battery pack according to the above aspect can also adopt an aspect where the case includes a pair of side surface parts, the plurality of batteries and the thermally conductive member are arranged between the pair of side surface parts, the holding part is provided to one of the pair of side surface parts, and the case further includes another holding part which is provided to other one of the pair of side surface parts, wherein the another holding part is not in contact with an other end surface of the thermally conductive member, the another holding part regulates the displacement of the two surfaces of the thermally conductive member in the direction vertical to each of the two surfaces which are connected with the other end surface and positioned on the opposite sides, the another holding part is in contact with at least one of the two surfaces, and thereby the another holding part holds an other end part of the thermally conductive member. 
     According to this aspect, it is possible to efficiently transfer the heat of the batteries to the case through the both end parts of the thermally conductive member. Furthermore, even in a case where positions of the end surfaces of the both ends of the thermally conductive member with respect to the holding part are displaced due to a manufacturing error of one or both of the thermally conductive member and the case, or an assembly error of the thermally conductive member and the case, it is possible to transfer the heat generated by the batteries to the case. 
     (3) The battery pack according to the above aspect can also employ an aspect where the thermally conductive member includes a recessed part, and is in contact with one battery of the plurality of batteries in the recessed part. 
     According to this aspect, it is possible to place a larger area of the thermally conductive member in contact with the battery in the recessed part compared to an aspect where the thermally conductive member is in planar contact with a battery. Consequently, the thermally conductive member can efficiently take heat from the battery compared to an aspect where the thermally conductive member is in planar contact with a battery. Furthermore, according to this aspect, it is possible to reduce a dimension of a range occupied by the thermally conductive member and the batteries in a recess direction of the recessed part compared to an aspect where the thermally conductive member does not include the recessed part. Consequently, it is possible to more highly densely arrange the batteries in the case. 
     (4) The battery pack according to the above aspect can also employ an aspect where the thermally conductive member further includes a plurality of other recessed parts on a surface opposite to a surface of the thermally conductive member provided with the recessed part, and is in contact with one battery of the plurality of batteries in each of the plurality of other recessed parts, and the recessed part is provided between two other neighboring recessed parts of the plurality of other recessed parts in a direction in which the plurality of other recessed parts are aligned. 
     According to this aspect, it is possible to reduce a dimension of a range occupied by the thermally conductive member and the batteries in contact with the both sides of the thermally conductive member in the direction vertical to a direction in which the plurality of other recessed parts are aligned while arranging the batteries on the both sides of the thermally conductive member. Consequently, it is possible to more highly densely arrange the batteries in the case. 
     (5) The battery pack according to the above aspect can also employ an aspect where the battery pack further includes: a plurality of other batteries; another thermally conductive member which is in contact with the plurality of other batteries; and a heat shielding member which is made of a material having lower thermal conductivity than thermal conductivity of the thermally conductive member and the other thermally conductive member, and the heat shielding member is arranged between a combination of the thermally conductive member and the plurality of batteries, and a combination of the other thermally conductive member and the plurality of other batteries. 
     According to this aspect, it is possible to prevent heat from being transferred between the plurality of batteries which transfer heat to each other through the thermally conductive member, and the plurality of other batteries which transfer heat to each other through the other thermally conductive member. As a result, when one or more batteries of the plurality of batteries cause abnormal heating, it is possible to reduce a probability that this heat causes a negative influence on the plurality of other batteries. When one or more batteries of the plurality of other batteries cause abnormal heating, it is possible to reduce a probability that this heat causes a negative influence on the plurality of batteries. 
     (6) The battery pack according to the above aspect can also employ an aspect where the holding part includes a slit in which the end part of the thermally conductive member is inserted, wherein the holding part is in contact with at least one of two surfaces of the thermally conductive member positioned on the opposite sides via at least one of two facing surfaces of the holding part, wherein the two facing surfaces define the slit, wherein the holding part is not in contact with the end surface via a surface of the holding part which connects the two facing surfaces which define the slit, and the thermally conductive member and the holding part are configured such that the thermally conductive member is detachable from the holding part by sliding in the slit the thermally conductive member with respect to the holding part. 
     According to this aspect, when the thermally conductive member and the plurality of batteries in contact with the thermally conductive member cause abnormalities, it is possible to easily detach from the case the thermally conductive member and the plurality of batteries in contact with the thermally conductive member to exchange with a new thermally conductive member and a plurality of new batteries in contact with the new thermally conductive member. 
     (7) The battery pack according to the above aspect can also employ an aspect where the battery pack further includes a grease which connects the surface which connects the two facing surfaces which define the slit, and the end surface of the thermally conductive member. 
     According to this aspect, it is possible to transfer heat from the end surface of the thermally conductive member to the surface which connects the two facing surfaces which define the slit through the grease. Consequently, even in a case where the positions of the end surfaces of the both ends of the thermally conductive member with respect to the holding part are displaced due to a manufacturing error of one or both of the thermally conductive member and the case, or an assembly error of the thermally conductive member and the case, it is possible to transfer heat from the end surface of the thermally conductive member to the holding part. 
     (8) One aspect of the present disclosure provides a battery pack. This battery pack includes: a plurality of batteries; a thermally conductive member which is in contact with the plurality of batteries; and a case which houses the plurality of batteries and the thermally conductive member inside, and is provided with a grip part which grips an end part of the thermally conductive member by sandwiching the end part of the thermally conductive member. 
     According to this configuration, the thermally conductive member in contact with the plurality of batteries is gripped by the grip part provided to the case, and heat generated by the batteries transfers to the case through the thermally conductive member, and is thereby dissipated from the case to an outside of the battery pack. The grip part grips the thermally conductive member by sandwiching the end part of the thermally conductive member, and consequently can grip the thermally conductive member even when a sandwiching position of the grip part is displaced due to a variation of the length of the thermally conductive member. Consequently, it is possible to transfer heat generated by the batteries to the case even when a manufacturing tolerance of the length of the thermally conductive member is made great compared to a case where, for example, the manufacturing tolerance of the length needs to be made strict to connect both end parts with the case. Consequently, it is possible to improve cooling efficiency of the batteries while reducing manufacturing cost of the battery pack. 
     (9) In the battery pack according to the above aspect, the case may include a pair of side surface parts, the plurality of batteries and the thermally conductive member may be arranged between the pair of side surface parts, the grip part may be provided to each of the pair of side surface parts, one of the end parts of the thermally conductive member may be gripped by the grip part provided to one of the pair of side surface parts, and other one of the end parts of the thermally conductive member may be gripped by the grip part provided to other one of the pair of side surface parts. According to this configuration, each of the both end parts of the thermally conductive member is gripped by each of the two grip parts provided to the pair of side surface parts. Consequently, it is possible to further make the manufacturing tolerance of the thermally conductive member great compared to a thermally conductive member whose one end part is fixed and whose other end part is gripped by the grip part. Consequently, it is possible to further reduce the manufacturing cost of the battery pack. 
     (10) In the battery pack according to the above aspect, the thermally conductive member may have a plate shape, and have a principal surface on which recessed and protrusion parts are formed, and the battery may be in contact with the recessed part of the recessed and protrusion parts of the thermally conductive member. According to this configuration, the battery is in contact with the recessed part of the recessed and protrusion parts of the thermally conductive member having the plate shape. Consequently, in a case where the batteries have cylindrical shapes, a volume occupied by the thermally conductive member and the batteries is small compared to a volume occupied by the thermally conductive member and the batteries in a case where the batteries are in contact with a principal surface of a thermally conductive member of a flat plate shape. Consequently, it is possible to house more batteries inside the case, so that it is possible to improve a packing density of the batteries while improving the cooling efficiency of the batteries. 
     (11) In the battery pack according to the above aspect, the thermally conductive member may include the recessed part of an other principal surface which is formed at a position at which the protrusion part of one principal surface is formed, and the recessed part may be in contact with the battery on both sides of the one principal surface and the other principal surface. According to this configuration, the thermally conductive member includes the recessed part of the other principal part which is formed at the position at which the protrusion part of the one principal surface is formed. The batteries arranged on the one principal surface side of the thermally conductive member are in contact with the recessed parts of the one principal surface, and the batteries arranged on the other principal surface side of the thermally conductive member are in contact with the recessed parts of the other principal surface on a back side of the protrusion parts of the one principal surface. Consequently, according to the battery pack  1 , in a case where the batteries have the cylindrical shapes, a volume occupied by the thermally conductive member and the batteries is further small compared to a volume occupied by the thermally conductive member and the batteries in a case where the batteries are respectively in contact with two principal surfaces included in a thermally conductive member of a flat plate shape. Consequently, it is possible to house more batteries inside the case, so that it is possible to further improve the packing density of the batteries while improving the cooling efficiency of the batteries. 
     (12) In the battery pack according to the above aspect, one thermally conductive member, and a plurality of batteries in contact with the one thermally conductive member may constitute a battery module, the battery pack may include a plurality of the battery modules, and the battery pack may further include a heat shielding member which is arranged between the neighboring battery modules. According to this configuration, the battery pack includes the plurality of battery modules which are each constituted by the one thermally conductive member and the plurality of batteries in contact with the one thermally conductive member. The heat shielding member is arranged between the neighboring battery modules. Consequently, it is possible to prevent heat exchange between the neighboring battery modules, and prevent an abnormality of one battery module from influencing the neighboring battery modules of the one battery module when a battery included in the one battery module causes the abnormality of an external appearance. Consequently, it is possible to prevent an abnormality of the one battery module from influencing the overall battery pack. 
     (13) In the battery pack according to the above aspect, one thermally conductive member and a plurality of batteries fixed to the one thermally conductive member may constitute a battery module, and the grip part may include a slit in which the end part of the thermally conductive member is inserted, and may be configured to enable attachment and detachment by sliding the battery module with respect to the slit. According to this configuration, the battery pack includes the plurality of battery modules which are each constituted by the one thermally conductive member and the plurality of batteries fixed to the one thermally conductive member. The grip part may include the slit in which the end part of the thermally conductive member included in the battery module can be inserted, and may be configured to enable attachment and detachment by sliding the battery module with respect to the slit. Consequently, when one battery module causes an abnormality, it is possible to return the battery pack to a normal state only by exchanging only the battery module which has caused the abnormality instead of the whole battery pack. Furthermore, it is possible to attach or detach the battery module by sliding the battery module with respect to the slit, so that it is possible to easily exchange the battery module. 
     (14) The battery pack according to the above aspect may include in the slit a thermally conductive grease which fills a gap between the end part of the thermally conductive member gripped by the grip part, and the grip part. According to this configuration, the gap between the end part of the thermally conductive member gripped by the grip part, and the grip part is filled by the thermally conductive grease. Consequently, in a case where the length of the thermally conductive member is relatively short, even when there is a gap between the end part of the thermally conductive member and the grip part, the thermally conductive grease which fills the gap can transfer heat from the thermally conductive member to the case through the grip part. Consequently, it is possible to further improve the cooling efficiency of the batteries. 
     Note that the present disclosure can be realized as various aspects, and can be realized as forms such as a system including the battery pack, a battery pack manufacturing method, a computer program which causes manufacturing of the battery pack to be executed, a server apparatus which distributes this computer program, and a non-transitory storage medium which stores this computer program. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view illustrating a schematic configuration of a battery pack according to a first embodiment. 
         FIG.  2 A  is a partial enlarged view of the battery pack. 
         FIG.  2 B  is an enlarged view illustrating an enlarged A part in  FIG.  2 A . 
         FIG.  3 A  is a perspective view of battery modules included in the battery pack. 
         FIG.  3 B  is an explanatory view illustrating processing of exchanging a battery module  15  in a battery pack  1 . 
         FIG.  4    is a partial cross-sectional view of a battery pack according to the present embodiment. 
         FIG.  5 A  is a view for explaining an issue of a battery pack according to a comparative example. 
         FIG.  5 B  is a view for explaining the issue of the battery pack according to the comparative example. 
         FIG.  6 A  is a view for explaining an effect of the battery pack according to the present embodiment. 
         FIG.  6 B  is a view for explaining the effect of the battery pack according to the present embodiment. 
         FIG.  7    is a schematic view illustrating a schematic configuration of a battery pack according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A. First Embodiment 
       FIG.  1    is a schematic view illustrating a schematic configuration of a battery pack  1  according to a first embodiment. The battery pack  1  according to the first embodiment is used as, for example, an in-vehicle battery of an electric vehicle for which high output is requested. The battery pack  1  includes a plurality of batteries  10 , a plurality of thermally conductive members  20  and a case  30 . Note that an x axis direction, a y axis direction and a z axis direction are defined as follows for convenience of description. A direction in which the thermally conductive members  20  extend is the x axis direction. The x axis direction is also a direction in which the batteries  10  in contact with one surface of the thermally conductive member  20  are aligned. A direction vertical to an x axis on a horizontal plane which passes all the batteries  10  housed in the case  30  is the y axis direction. Furthermore, the direction vertical to the x axis direction and the y axis direction is the z axis direction. 
     The battery  10  is a lithium ion battery having a cylindrical shape. The battery pack  1  includes the plurality of batteries  10 . According to the present embodiment, respective center axes of the plurality of batteries  10  are arranged in substantially parallel to a z axis. The batteries  10  are electrically connected with an unillustrated input/output unit of the battery pack  1 . The batteries  10  receive and store, for example, electrical energy supplied from an external power supply of an electric vehicle and electrical energy generated by deceleration of the running electrical vehicle via this input/output unit. Furthermore, the batteries  10  output the electrical energy for driving a motor included in the electrical vehicle via the input/output unit. 
     As illustrated in  FIG.  1   , the battery pack  1  includes rows B 1  in which the six batteries  10  are aligned along the x axis direction, and rows B 2  in which the five batteries  10  are aligned along the x axis direction. The rows B 1  of the batteries  10  are referred to as the “battery rows B 1 ” in this description. The rows B 2  of the batteries  10  are referred to as the “battery rows B 2 ” in this description. The battery pack  1  includes the eight battery rows B 1  and the eight battery rows B 2 . The battery rows B 1  and the battery rows B 2  are alternately arranged in the y axis direction (see  FIG.  1   ). 
     The thermally conductive member  20  is a member of a plate shape formed by a material having high thermal conductivity such as metal. Note that a shape whose dimension in a thickness direction is ¼ or less than a smaller dimension of a dimension in a vertical direction and a dimension in a horizontal direction is referred to as a “plate shape” in this description. The plate shape includes a corrugated plate. 
     As illustrated in  FIG.  1   , the battery pack  1  includes the eight thermally conductive members  20 . Two surfaces of the largest plates are referred to as “principal surfaces” in this description. The thermally conductive member  20  includes two principal surfaces  21  and  22  to each of which the plurality of batteries  10  are fixed. A plurality of recessed and protrusion parts are formed on the principal surfaces  21  and  22  of the thermally conductive member  20 . 
       FIG.  2 A  is a partial enlarged view of the battery pack  1 .  FIG.  2 B  is an enlarged view illustrating an enlarged A part in  FIG.  2 A . The thermally conductive member  20  includes recessed parts  21   b,    21   d,    21   f  and  21   h.  The thermally conductive member  20  is in contact with the one battery  10  of the plurality of batteries  10  in each of the recessed parts  21   b,    21   d,    21   f  and  21   h.  The thermally conductive member  20  further includes a plurality of other recessed parts  22   a,    22   c ,  22   e,    22   g  and  22   i  on the surface  22  opposite to the surface  21  provided with the recessed parts  21   b,    21   d,    21   f  and  21   h  of the thermally conductive member  20 . The thermally conductive member  20  is in contact with the one battery  10  of the plurality of batteries  10  in each of the plurality of other recessed parts  22   a,    22   c,    22   e ,  22   g  and  22   i.    
     More specifically, as illustrated in  FIG.  2 A , the five protrusion parts and the four recessed parts are formed along the x axis direction and between one end part  20   a  on a minus x axis side and an other end part  20   b  on a plus x axis side on the principal surface  21  on a minus y axis side of the thermally conductive member  20 . These protrusion parts and recessed parts are aligned and arranged in order of a protrusion part  21   a,  the recessed part  21   b,  a protrusion part  21   c,  the recessed part  21   d,  a protrusion part  21   e,  the recessed part  21   f,  a protrusion part  21   g,  the recessed part  21   h  and a protrusion part  21   i  from the one end part  20   a  side. 
     The batteries  10  of the battery row B 1  are fixed to the principal surface  21 . The four batteries  10  of the six batteries  10  of the battery row B 1  are respectively fixed to the recessed part  21   b,  the recessed part  21   d,  the recessed part  21   f  and the recessed part  21   h.  The principal surface  21  on the minus y axis side of the thermally conductive member  20  is also referred to as “one principal surface”. The curvatures of recessed surfaces of the recessed parts  21   b,    21   d,    21   f  and  21   h  substantially match with curvatures of outer circumferential surfaces of the batteries  10  of the columnar shapes. 
     According to this configuration, it is possible to place a larger area of the thermally conductive member  20  in contact with the batteries in the recessed parts  21   b,    21   d,    21   f  and  21   h  compared to an aspect where the thermally conductive member  20  is in planar contact with the batteries  10 . Consequently, the thermally conductive member  20  can efficiently take heat from the batteries compared to an aspect where the thermally conductive member  20  is in planar contact with the batteries. 
     Furthermore, according to this configuration, it is possible to reduce a dimension of a range W 1  occupied by the thermally conductive member  20  and the batteries  10  in a recess direction of the recessed parts  21   b,    21   d,    21   f  and  21   h,  i.e., in the y axis direction compared to an aspect where the thermally conductive member  20  does not include the recessed parts  21   b,    21   d,    21   f  and  21   h  (see a lower stage in  FIG.  2 A ). Consequently, it is possible to more densely arrange the batteries  10  in the case  30 . 
     As illustrated in  FIG.  2 A , the five recessed parts and the four protrusion parts are formed along the x axis direction and between the one end part  20   a  on the minus x axis side and the other end part  20   b  on the plus x axis side on the principal surface  22  on a plus y axis side of the thermally conductive member  20 . These recessed parts and protrusion parts are aligned and arranged in order of the recessed part  22   a,  a protrusion part  22   b,  the recessed part  22   c,  a protrusion part  22   d , the recessed part  22   e,  a protrusion part  22   f,  the recessed part  22   g,  a protrusion part  22   h  and the recessed part  22   i  from the one end part  20   a  side. Each of the recessed part  22   a,  the recessed part  22   c,  the recessed part  22   e,  the recessed part  22   g  and the recessed part  22   i  of the principal surface  22  is formed at a position at which each of the protrusion part  21   a,  the protrusion part  21   c,  the protrusion part  21   e,  the protrusion part  21   g  and the protrusion part  21   i  of the principal surface  21  is formed. Each of the protrusion part  22   b,  the protrusion part  22   d,  the protrusion part  22   f  and the protrusion part  22   h  of the principal surface  22  is formed at a position at which each of the recessed part  21   b,  the recessed part  21   d,  the recessed part  21   f  and the recessed part  21   h  of the principal surface  21  is formed. As a result, the recessed parts  21   b,    21   d,    21   f  and  21   h  are positioned between the two neighboring recessed parts of the other recessed parts  22   a,    22   c,    22   e,    22   g  and  22   i  in the x axis direction in which the other recessed parts  22   a,    22   c,    22   e,    22   g  and  22   i  are aligned. 
     The batteries  10  of the battery row B 2  are fixed to the principal surface  22 . The five batteries  10  of the battery row B 2  are respectively fixed to the recessed part  22   a,  the recessed part  22   c,  the recessed part  22   e,  the recessed part  22   g  and the recessed part  22   i.  The principal surface  22  on the plus y axis side of the thermally conductive member  20  is also referred to as an “other principal surface”. The curvatures of recessed surfaces of the recessed parts  22   a,    22   c,    22   e,    22   g  and  22   i  substantially match with curvatures of outer circumferential surfaces of the batteries  10  of the columnar shapes. 
     According to this aspect, it is possible to reduce a dimension of a range W 2  occupied by the thermally conductive member  20  and the batteries  10  in contact with the both sides of the thermally conductive member  20  in the y axis direction vertical to the x axis direction in which the plurality of recessed parts  22   a,    22   c,    22   e ,  22   g  and  22   i  are aligned while arranging the batteries  10  on the both sides of the thermally conductive member  20  (see the lower stage in  FIG.  2 A ). Consequently, it is possible to more densely arrange the batteries  10  in the case  30 . 
       FIG.  3 A  is a perspective view of a battery module  15  included in the battery pack  1 .  FIG.  3 B  is an explanatory view illustrating processing of exchanging the battery modules  15  in the battery pack  1 . According to the present embodiment, the one thermally conductive member  20  and the  11  batteries  10  fixed to this one thermally conductive member  20 , i.e., the one battery row B 1  and the one battery row B 2  constitute the one battery module  15  illustrated in  FIG.  3 A . As illustrated in  FIG.  3 B , the battery pack  1  includes the eight battery modules  15 . 
     According to the present embodiment, as illustrated in  FIG.  3 B , when a failure occurs in one battery  10   d,  a battery module  15   o  including the battery  10   d  which has caused this failure is detached (an outlined arrow T 1  in  FIG.  3 B ). Subsequently, a new battery module  15   n  is attached to a place at which the battery module  15   o  has been detached (an outlined arrow T 2  in  FIG.  3 B ). 
     The case  30  houses the plurality of batteries  10  and the plurality of thermally conductive members  20  inside (see  FIG.  1   ). The case  30  is formed by, for example, metal having high thermal conductivity. The case  30  includes a plurality of wall parts  31 ,  32 ,  33  and  34  which form a housing space  30   a  for housing the plurality of batteries  10  and the plurality of thermally conductive members  20 , a plurality of grip parts  36 , and a plurality of grip parts  37 . Note that  FIG.  1    illustrates the battery pack  1  in a state where the wall part  34  has been detached from the case  30  for ease of understanding of the technique. The case  30  is connected with an unillustrated external heat dissipation device. The case  30  transfers heat generated by the batteries  10  to this heat dissipation device. 
     As illustrated in  FIG.  1   , the wall part  31  and the wall part  32  are arranged at positions facing each other (see an upper stage center part and a lower stage center part in  FIG.  1   ). The wall part  31  and the wall part  32  form the housing space  30   a  in which the plurality of batteries  10  and the plurality of thermally conductive members  20  are arranged. A surface on the housing space  30   a  side of the wall part  31  is provided with the plurality of grip parts  36  (see an upper stage in  FIG.  1    and an upper stage in  FIG.  2   ). A surface on the housing space  30   a  side of the wall part  32  is provided with the plurality of grip parts  37  (see a lower stage in  FIG.  1    and a lower stage in  FIG.  2   ). Details of configurations of the grip parts  36  and  37  will be described later. The wall part  31  and the wall part  32  are also referred to as “a pair of side surface parts”. 
       FIG.  4    is a perspective view of the battery pack  1  according to the present embodiment from which part of the components of the battery pack  1  have been removed. The wall part  33  is connected with an end part on a minus z axis direction side of the wall part  31 , and an end part on the minus z axis direction side of the wall part  32  (see a lower stage center part in  FIG.  4   ). The wall part  33  corresponds to a bottom part of the case  30 . As illustrated in  FIG.  4   , the plurality of batteries  10  housed in the housing space  30   a  is placed on the wall part  33 . The wall part  34  is connected with an end part on a plus z axis direction side of the wall part  31 , and an end part on the plus z axis direction side of the wall part  32 . The wall part  34  is arranged at a position which faces the wall part  33 . As illustrated in  FIG.  4   , a plurality of fins  34   a  are formed in an outer wall surface of the wall part  34 . Consequently, the case  30  can dissipate heat to the above-described heat dissipation device and, in addition, efficiently dissipate heat generated by the batteries  10  to an outside by using the fins  34   a.    
     As illustrated in the upper stage in  FIG.  2 A , the grip part  36  is arranged on a surface on the housing space  30   a  side of the wall part  31 . The grip part  36  includes two slit formation parts  36   a  and  36   b.  The two slit formation parts  36   a  and  36   b  each protrude from the surface on the housing space  30   a  side of the wall part  31  to a plus x axis direction. As illustrated in  FIG.  2 B , the two slit formation parts  36   a  and  36   b  are arranged so as to form a gap of a certain interval. On each of the two slit formation parts  36   a  and  36   b,  inner wall surfaces  36   c  and  36   d  of planar shapes which face each other in the y axis direction are formed. A space between the inner wall surface  36   c  and the inner wall surface  36   d  is a slit S which penetrates the grip part  36  in the z axis direction. 
     The grip part  36  is not in contact with an end surface  23  of the thermally conductive member  20  in a minus x axis direction. The wall part  31  which supports the grip part  36  is not in contact with the end surface  23  of the thermally conductive member  20 , either. The grip part  36  regulates displacement of each of the surfaces  21  and  22  of the thermally conductive member  20  in the y axis direction vertical to each of the surfaces  21  and  22  which are connected with the end surface  23  and positioned on sides opposite to each other. That is, the surfaces  21  and  22  of the thermally conductive member  20  are positioned within a range defined by the grip part  36  in the y axis direction. The grip part  36  is in contact with at least one of the two surfaces  21  and  22 , and thereby holds the end part  20   a  of the thermally conductive member  20 . According to the present embodiment, the grip part  36  is substantially in contact with the two surfaces  21  and  22 , and thereby determines the position of the end part  20   a  of the thermally conductive member  20 . 
     According to this configuration, it is possible to transfer heat generated by the batteries  10  to the case  30  through the thermally conductive member  20  which is in contact with the batteries  10 , and the grip part  36  which is in contact with at least one of the two surfaces  21  and  22  of the thermally conductive member  20 . Furthermore, even in a case where the position of the end surface  23  of the thermally conductive member  20  with respect to the grip part  36  is displaced from a designed position due to a manufacturing error of one or both of the thermally conductive member  20  and the case  30 , it is possible to transfer the heat generated by the batteries to the case  30 . 
     More specifically, as illustrated in  FIG.  2 B , the inner wall surface  36   c  and the inner wall surface  36   d  of the grip part  36  sandwich the one end part  20   a  of the thermally conductive member  20 , and thereby grip the one end part  20   a  of the thermally conductive member  20 . According to the present embodiment, as illustrated in  FIG.  2 B , the one end part  20   a  of the thermally conductive member  20  is gripped by the grip part  36  in the slit S. 
     In this state, at least one of the two facing surfaces  36   c  and  36   d  of the grip part  36  which define the slit S is in contact with at least one of the two surfaces  21  and  22  of the thermally conductive member  20  positioned on the sides opposite to each other. The wall part  31  is not in contact with the end surface  23  of the thermally conductive member  20  via a surface  36   e  which connects the two facing surfaces  36   c  and  36   d  in the slit S. 
     A gap between the one end part  20   a  of the thermally conductive member  20  and the grip part  36  is filled by a thermally conductive grease  38 . As a result, the surface  36   e  which connects the two facing surfaces  36   c  and  36   d  in the slit S and the end surface  23  of the thermally conductive member  20  are connected by the thermally conductive grease  38  (see an upper stage center part in  FIG.  2 B ). 
     According to this configuration, it is possible to transfer heat from the end surface  23  of the thermally conductive member  20  to the surface  36   e  which connects the two facing surfaces  36   c  and  36   d  in the slit S through the thermally conductive grease  38 . Consequently, even in a case where the position of the end surface  23  of the thermally conductive member  20  with respect to the grip part  36  is displaced due to a manufacturing error of one or both of the thermally conductive member  20  and the case  30  or an assembly error of the thermally conductive member  20  and the case  30 , it is possible to transfer heat from the end surface  23  of the thermally conductive member  20  to the grip part  36 . 
     According to the present embodiment, sizes of the two slit formation parts  36   a  and  36   b  in the x axis direction are different to prevent an interference with the batteries  10  fixed to the thermally conductive member  20 . More specifically, the dimension of the slit formation part  36   b  in the x axis direction is smaller than the dimension of the slit formation part  36   a  in the x axis direction. As a result, an interference between the battery  10  at an end of the battery row B 1  and the slit formation part  36   b  is prevented. 
     Note that  FIG.  2 B  illustrates the enlarged width of the slit S compared to the width of the one end part  20   a  of the thermally conductive member  20  to clarify a positional relationship between the principal surface  21  of the thermally conductive member  20 , the inner wall surface  36   d  of the slit formation part  36   b  and the thermally conductive grease  38  in the slit S. However, the inner wall surfaces  36   c  and  36   d  are actually substantially in contact with the principal surfaces  21  and  22  of the thermally conductive member  20 , respectively. The thermally conductive grease  38  fills minute gaps of various portions between the inner wall surface  36   d  and the principal surface  21 . As a result, the thermally conductive grease  38  functions to increase an area of a part at which heat is transferred between the inner wall surface  36   d  and the principal surface  21 . 
     The thermally conductive member  20  and the grip part  36  are configured such that the thermally conductive member  20  can be detached from the grip part  36  by sliding in the slit S the thermally conductive member  20  with respect to the grip part  36 . 
     According to this configuration, when the thermally conductive member  20  and the plurality of batteries  10  in contact with the thermally conductive member  20  cause abnormalities, the abnormalities can be dealt with as follows. That is, it is possible to easily detach the thermally conductive member  20  and the plurality of batteries  10  in contact with the thermally conductive member  20  from the case  30  to exchange with the new thermally conductive member  20  and the plurality of new batteries  10  in contact with the new thermally conductive member  20  (see  FIG.  3 B ). 
     The grip part  37  is arranged on a surface on the housing space  30   a  side of the wall part  32  (see a lower stage in  FIG.  2 A ). The grip part  37  is provided in a shape symmetrical to that of the grip part  36  around an axis parallel to the y axis direction. As a result, the grip part  37  exhibits the same function as that of the grip part  36 . 
     According to this configuration, it is possible to efficiently transfer heat of the batteries  10  to the case  30  through the both end parts  20   a  and  20   b  of the thermally conductive member  20 . Furthermore, even in a case where the positions of the end surfaces  23  and  24  at the both ends of the thermally conductive member  20  in the x axis direction with respect to the grip part  36  are displaced due to a manufacturing error of one or both of the thermally conductive member  20  and the case  30  or an assembly error of the thermally conductive member  20  and the case  30 , it is possible to transfer heat generated by the batteries  10  to the case  30 . 
     More specifically, the grip part  37  includes two slit formation parts  37   a  and  37   b.  The two slit formation parts  37   a  and  37   b  each protrude from the surface on the housing space  30   a  side of the wall part  32  to the minus x axis direction. The two slit formation parts  37   a  and  37   b  are arranged so as to form a gap of a certain interval substantially equal to the gap of the grip part  36 . On each of the two slit formation parts  37   a  and  37   b,  inner wall surfaces of planar shapes which face each other in the y axis direction are formed. A space between these inner wall surfaces is a slit which penetrates the grip part  36  in the z axis direction. 
     The grip part  37  is not in contact with the end surface  24  of the thermally conductive member  20  in the plus x axis direction. The wall part  32  which supports the grip part  37  is not in contact with the end surface  24  of the thermally conductive member  20 , either. The grip part  37  regulates displacement of each of the surfaces  21  and  22  of the thermally conductive member  20  in the y axis direction vertical to each of the surfaces  21  and  22  which are connected with the end surface  24  and positioned on the sides opposite to each other, is in contact with at least one of the two surfaces, and thereby holds the end part  20   b  of the thermally conductive member  20 . 
     More specifically, as illustrated in  FIG.  2 A , the two inner wall surfaces respectively formed on the two slit formation parts  37   a  and  37   b  of the grip part  37  sandwich the other end part  20   b  of the thermally conductive member  20 , and thereby grip the other end part  20   b  of the thermally conductive member  20 . According to the present embodiment, a gap between the other end part  20   b  of the thermally conductive member  20  gripped by the grip part  37 , and the grip part  37  in the slit formed in the grip part  37  is filled by the same thermally conductive grease as that of the grip part  36  (see  FIG.  2 B ). Similar to the grip part  36 , sizes of the two slit formation parts  37   a  and  37   b  in the x axis direction are different to prevent an interference with the batteries  10  fixed to thermally conductive member  20 . More specifically, the dimension of the slit formation part  37   b  in the x axis direction is smaller than the dimension of the slit formation part  37   a  in the x axis direction. As a result, an interference between the battery  10  at an end of the battery row B 1  and the slit formation part  37   b  is prevented. 
     The both end parts  20   a  and  20   b  are inserted in the respective slits of the two grip parts  36  and  37  such that each of the eight battery modules  15  included in the battery pack  1  is gripped by the grip parts  36  and  37  (see  FIG.  3 B ). By detaching the wall part  34  from the case  30  and then sliding the arbitrary battery module  15  in the plus z axis direction with respect to the grip parts  36  and  37 , the arbitrary battery module  15  can be detached from the case  30  (see the arrow T 1  in  FIG.  3 B ). Then, by sliding the new battery module  15  in the minus z axis direction with respect to the grip part  36  and  37 , this new battery module  15  is attached to the case  30  (see the arrow T 2  in  FIG.  3 B ). Consequently, it is possible to easily exchange the battery module  15  as described above. 
     Next, an effect of the battery pack  1  according to the present embodiment will be described. First, an issue of a battery pack  90  according to a comparative example will be described with reference to  FIGS.  5 A and  5 B . 
       FIGS.  5 A and  5 B  are explanatory views for explaining the issue of the battery pack  90  according to the comparative example. In the battery pack  90  according to the comparative example illustrated in  FIG.  5 A , the plurality of batteries  10  are aligned in a row and arranged between a pair of wall parts  92  and  93  of a case of the battery pack  90 . Thermally conductive members  91  in contact with the plurality of these batteries  10  are arranged on both sides of the plurality of batteries  10 , and are formed to surround the batteries  10 . The thermally conductive member  91  is arranged between the pair of wall parts  92  and  93 . In the battery pack  90  according to the comparative example, both end parts of the thermally conductive member  91  are respectively fixed by, for example, welding to the wall parts  92  and  93 . 
     An actual size of the thermally conductive member  91  is determined at a manufacturing stage. The length of the thermally conductive member  91  in a direction in which the plurality of batteries  10  are aligned may differ per individual thermally conductive member  91  due to a manufacturing error in some cases. Hence, the plurality of thermally conductive members  91  include the relatively short thermally conductive members  91  illustrated in  FIG.  5 A , and the relatively long thermally conductive members  91  illustrated in  FIG.  5 B . In a case where, for example, a length L 01  of the thermally conductive member  91  in a direction in which the batteries  10  in contact with the thermally conductive member  91  are aligned is shorter than a distance L 0  between the pair of wall parts  92  and  93  as illustrated in  FIG.  5 A , while one end part  94  of the thermally conductive member  91  can be connected with the wall part  92 , an other end part  95  cannot be connected with the wall part  93 . Consequently, heat of the batteries  10  on the end part  95  side of the thermally conductive member  91  is hardly dissipated to an outside through the case in the manufactured battery pack  90 . 
     Furthermore, in a case where a length L 02  of the thermally conductive member  91  in the direction in which the batteries  10  in contact with the thermally conductive member  91  are aligned is longer than the distance L 0  between the pair of wall parts  92  and  93  as illustrated in  FIG.  5 B , the thermally conductive member  91  to which the batteries  10  are fixed cannot be arrange between the pair of wall parts  92  and  93  (see the thermally conductive member  91  indicated by a broken line in  FIG.  5 B ). Consequently, it is necessary to manufacture the thermally conductive member  91  such that the length of the thermally conductive member  91  in the direction in which the batteries  10  are aligned is not longer than the distance L 0  between the pair of wall parts  92  and  93 . On the other hand, as described with reference to  FIG.  5 A , in the case where the length of the thermally conductive member  91  is shorter than the distance L 0  between the pair of wall parts  92  and  93 , one of the two end parts  94  and  95  cannot be connected with the wall parts  92  and  93 . 
     Therefore, cooling efficiency differs between the plurality of thermally conductive members  91  depending on the lengths of the thermally conductive members  91 . As a result, the cooling efficiency varies per thermally conductive member  91 , and the cooling efficiency of the overall battery pack  90  lowers. To prevent the variation of the cooling efficiency, the lengths of the thermally conductive members  91  need to be accurately managed to match with or become slightly shorter than the distance L 0  between the pair of wall parts  92  and  93  which is an upper limit. That is, it is necessary to set a small manufacturing tolerance for the thermally conductive members  91 . Therefore, manufacturing cost of the battery pack  90  increases. 
       FIGS.  6 A and  6 B  are explanatory views for explaining the effect of the battery pack  1  according to the present embodiment. As described above, according to the battery pack  1  according to the present embodiment, the pair of wall parts  31  and  32  are provided with the grip parts  36  and  37 , respectively, which grip the two end parts  20   a  and  20   b  of the thermally conductive member  20 , respectively (see  FIGS.  1  and  2 A ). In, for example, a manufacturing process of the thermally conductive member  20 , a reference dimension of the length of the thermally conductive member  20  can be set to the distance L 1  between a center line C 36  of the grip part  36  and a center line C 37  of the grip part  37  (see an upper stage in  FIG.  6 A ). Note that the center line C 36  is a line which indicates a center position of the slit S of the grip part  36  in the x axis direction. The center line C 37  is a line which indicates a center position of the slit of the grip part  37  in the x axis direction. According to this aspect, even in a case where a length L 11  of the thermally conductive member  20  in a direction in which the batteries  10  in contact with the thermally conductive member  20  are aligned is shorter than the length L 1  as illustrated in  FIG.  6 A , the thermally conductive member  20  can be held by the grip parts  36  and  37 . Furthermore, even in a case where a length L 12  of the thermally conductive member  20  in the direction in which the batteries  10  in contact with the thermally conductive member  20  are aligned is longer than the length L 1  as illustrated in  FIG.  6 B , the thermally conductive member  20  can be arranged in the case  30 . Consequently, the manufacturing tolerance of the thermally conductive member  20  can be made greater than the manufacturing tolerance of the thermally conductive member  91  according to the comparative example. Consequently, the manufacturing cost of the battery pack  1  is reduced. Furthermore, in the both cases, the two end parts  20   a  and  20   b  of the thermally conductive member  20  are gripped by the two grip parts  36  and  37 , respectively, so that heat generated by the batteries  10  transfers to the case  30  through the thermally conductive member  20  (see  FIGS.  5 A and  6 A ). Consequently, the cooling efficiency varies becomes less between the plurality of thermally conductive members  20 , so that it is possible to improve the cooling efficiency. 
     According to the above-described battery pack  1  according to the present embodiment, the thermally conductive members  20  to which the plurality of batteries  10  are fixed are gripped by the grip parts  36  and  37  provided to the case  30 . Consequently, the heat generated by the batteries  10  transfers to the case  30  through the thermally conductive members  20 , and thereby is dissipated from the case  30  to the outside of the battery pack  1 . The grip parts  36  and  37  grip the thermally conductive members  20  by sandwiching the two end parts  20   a  and  20   b  of the thermally conductive members  20 . Consequently, even in a case where the positions of the two end parts  20   a  and  20   b  of the thermally conductive members  20  with respect to the grip parts  36  and  37  are displaced due to variations of the lengths of the thermally conductive member  20 , the grip parts  36  and  37  can grip the thermally conductive members  20 . Consequently, even in a case where the manufacturing tolerance of the length is made great compared to the comparative example where the manufacturing tolerance of the length of the thermally conductive members needs to be strictly managed to connect the both end parts with the case, it is possible to transfer the heat generated by the batteries  10  to the case  30 . Consequently, it is possible to improve the cooling efficiency of the batteries  10  while reducing the manufacturing cost of the battery pack  1 . 
     Furthermore, according to the battery pack  1  according to the present embodiment, the two end parts  20   a  and  20   b  of the thermally conductive member  20  are gripped by the grip parts  36  and  37 , respectively, which are provided to the pair of wall parts  31  and  32 . Consequently, compared to the thermally conductive member whose one end part is fixed and whose other end part is fixed to the case, it is possible to make the manufacturing tolerance of the thermally conductive member  20  greater. Consequently, it is possible to further reduce the manufacturing cost of the battery pack  1 . 
     Furthermore, in the battery pack  1  according to the present embodiment, the batteries  10  have the columnar shapes. The nine batteries  10  are in contact with the recessed parts  21   b,    21   d,    21   f,    21   h,    22   a,    22   c,    22   e,    22   g  and  22   i  of the thermally conductive member  20  having the plate shape. More specifically, part of each of the nine batteries  10  is positioned in the recessed parts  21   b,    21   d,    21   f,    21   h,    22   a,    22   c,    22   e ,  22   g  and  22   i  of the thermally conductive member  20 . Consequently, a volume of a minimum cuboid surrounding a space occupied by the one thermally conductive member  20  and the plurality of batteries  10  in contact with this thermally conductive member  20  is smaller than a volume of a minimum cuboid surrounding a space occupied by one thermally conductive member and a plurality of batteries in contact with this one thermally conductive member in a case where the batteries of cylindrical shapes are in contact with principal surfaces of the thermally conductive member of flat plate shapes. Consequently, it is possible to house the more batteries  10  inside the case  30 . Consequently, it is possible to improve a packing density of the batteries  10  while improving the cooling efficiency of the batteries  10 . 
     Furthermore, according to the battery pack  1  according to the present embodiment, each of the recessed part  22   a,  the recessed part  22   c,  the recessed part  22   e,  the recessed part  22   g  and the recessed part  22   i  of the principal surface  22  of the thermally conductive member  20  is formed at a position at which each of the protrusion part  21   a,  the protrusion part  21   c,  the protrusion part  21   e,  the protrusion part  21   g  and the protrusion part  21   i  of the principal surface  21  is formed. The batteries  10  arranged on the principal surface  21  side of the thermally conductive member  20  are fixed to the recessed parts  21   b,    21   d,    21   f  and  21   h  of the principal surface  21 . Furthermore, the batteries  10  arranged on the principal surface  22  side of the thermally conductive member  20  are fixed to the recessed parts  22   a,    22   c,    22   e ,  22   g  and  22   i  of the principal surface  22 . More specifically, the nine batteries  10  are arranged in a zig-zag pattern along a longitudinal direction of the thermally conductive member  20  while being in contact with the recessed parts  21   b,    21   d,    21   f ,  21   h,    22   a,    22   c,    22   e,    22   g  and  22   i  of the thermally conductive member  20 . Consequently, according to the battery pack  1 , the volume of the minimum cuboid surrounding the space occupied by the one thermally conductive member and the plurality of batteries in contact with this one thermally conductive member is much smaller than the volume of the minimum cuboid surrounding the space occupied by the one thermally conductive member and the plurality of batteries in contact with this one thermally conductive member in a case where the batteries are in contact with each of the two principal surfaces included in the thermally conductive member of the flat plate shape. Consequently, it is possible to house the much more batteries  10  inside the case  30 . Consequently, it is possible to improve the packing density of the batteries  10  while improving the cooling efficiency of the batteries  10 . 
     Furthermore, according to the battery pack  1  according to the present embodiment, the battery pack  1  includes the plurality of battery modules  15 . The one battery module  15  is constituted by the one thermally conductive member  20 , and the plurality of batteries  10  fixed to the one thermally conductive member  20 . The grip parts  36  and  37  include the slits in which one of the two end parts  20   a  and  20   b  of the thermally conductive member  20  included in the battery module  15  can be inserted, and are configured to enable attachment and detachment of the battery module  15  by sliding the battery module  15  with respect to the slit. Consequently, it is possible to return the battery pack  1  to a normal state by exchanging only the battery module  15  which has caused an abnormality instead of the whole battery pack  1  when the one battery module  15  causes the abnormality. Furthermore, by sliding the battery module  15  with respect to the slit, the battery module  15  can be attached and detached, so that it is possible to easily exchange the battery module  15 . 
     Furthermore, according to the battery pack  1  according to the present embodiment, the gaps between the two end parts  20   a  and  20   b  of the thermally conductive member  20  gripped by the grip parts  36  and  37 , and the grip parts  36  and  37  are filled by the thermally conductive grease  38 . Consequently, even when relatively short length of the thermally conductive member  20  creates the gaps between the end parts  20   a  and  20   b  of the thermally conductive member  20  and the grip parts  36  and  37 , the thermally conductive grease  38  which fills the gaps can transfer heat from the thermally conductive member  20  to the case  30  through the grip parts  36  and  37 . Consequently, it is possible to further improve the cooling efficiency of the batteries  10 . 
     The grip part  36  , the part of the wall part  31  which supports the grip part  36 , and the part of the wall part  31  which forms the inner wall surface  36   e  of the slit S in the present embodiment are also referred to as a “holding part”. The grip part  37 , the part of the wall part  32  which supports the grip part  37 , and the part of the wall part  32  which forms the inner wall surface of the slit of the grip part  37  are also referred to as an “other holding part”. The thermally conductive grease  38  is also referred to as a “grease”. 
     B. Second Embodiment 
       FIG.  7    is a schematic view illustrating a schematic configuration of a battery pack  2  according to a second embodiment. The battery pack  2  according to the second embodiment differs from the battery pack  1  according to the first embodiment illustrated in  FIG.  1    in including heat shielding members. Other points of the battery pack  2  according to the second embodiment are the same as those of the battery pack  1  according to the first embodiment. 
     The battery pack  2  according to the present embodiment includes the plurality of batteries  10 , the thermally conductive members  20 , heat shielding members  25  and a case  40 . 
     The heat shielding member  25  is a member of a plate shape arranged between the neighboring battery modules  15  among the plurality of battery modules  15  arranged in the case  40 . The heat shielding member  25  has low thermal conductivity, and is formed by a material having fire retardancy. More specifically, the heat shielding member  25  is made of a material having lower thermal conductivity than that of the material of the thermally conductive member  20 . The thermal conductivity of the material of the heat shielding member  25  is lower than thermal conductivity of the material of the case  30  and thermal conductivity of the thermally conductive grease  38 . According to the present embodiment, the battery pack  2  includes the six heat shielding members  25 . 
     That is, the heat shielding member  25  is arranged between a combination of the thermally conductive member  20  and the plurality of batteries  10  which constitute the certain battery module  15 , and a combination of the another thermally conductive member  20  and the plurality of other batteries  10  which constitute the another battery module  15 . 
     According to this configuration, it is possible to prevent heat from being transferred between the plurality of batteries  10  which transfer heat to each other through the thermally conductive member  20 , and the plurality of other batteries  10  which transfer heat to each other through the another thermally conductive member  20 . As a result, when the one or more batteries of the plurality of batteries  10  cause abnormal heating, it is possible to reduce a probability that this heat causes a negative influence on the plurality of other batteries  10 . Furthermore, when the one or more batteries of the plurality of other batteries  10  cause abnormal heating, it is possible to reduce a probability that this heat causes a negative influence on the plurality of batteries  10 . 
     The case  40  includes the plurality of wall parts  31 ,  32 ,  33  and  34  which form a housing space  40   a  which houses the plurality of batteries  10 , the plurality of thermally conductive members  20  and the plurality of heat shielding members  25 , the plurality of grip parts  36  and the plurality of grip parts  37  which respectively grip the thermally conductive members  20 , and the plurality of grip parts  48  and the plurality of grip parts  49  which respectively grip the heat shielding members  25 . 
     The grip part  48  is arranged between the neighboring grip parts  36  on the surface on the housing space  40   a  side of the wall part  31  (see an upper stage in  FIG.  7   ). The grip part  48  protrudes from the surface on the housing space  30   a  of the wall part  31  side to the plus x axis direction. The grip part  48  includes a slit in which an end part of the heat shielding member  25  can be inserted. The grip part  48  grips the end part of the heat shielding member  25  when the end part of the heat shielding member  25  is inserted therein. 
     The grip part  49  is arranged between the neighboring grip parts  37  on the surface on the housing space  40   a  side of the wall part  32  (see a lower stage in  FIG.  7   ). The grip part  49  protrudes from the surface on the housing space  30   a  side of the wall part  32  to the minus x axis direction. The grip part  49  includes a slit in which an end part of the heat shielding member  25  can be inserted. The grip part  49  grips the end part of the heat shielding member  25  when the end part of the heat shielding member  25  is inserted therein. 
     The two end parts of the heat shielding member  25  are respectively held in the slits included in the two grip parts  48  and  49 , and thereby supported. As a result, the heat shielding member  25  shields between the neighboring battery module  15  and battery module  15 . The heat shielding member  25  is configured to be exchangeable by being slid with respect to the grip parts  48  and  49 . 
     According to the above-described battery pack  2  according to the present embodiment, the battery pack  2  includes the plurality of battery modules  15  which are each constituted by the one thermally conductive member  20  and the plurality of batteries  10  in contact with the one thermally conductive member  20 , and the heat shielding members  25  are arranged between the neighboring battery modules  15 . Consequently, it is possible to prevent heat exchange between the neighboring battery modules  15 , and prevent an abnormality of the one battery module  15  from influencing the neighboring battery module  15  of the one battery module  15  when the abnormality occurs in an external appearance of the battery  10  included in the one battery module  15 . Consequently, it is possible to prevent the abnormality of the one battery module  15  from influencing the overall battery pack  2 . 
     C. Modified Example of Present Embodiment 
     The present disclosure is not limited to the above embodiments, can be carried out as various aspects without departing from the spirit of the present disclosure, and can be also modified as follows, for example. 
     MODIFIED EXAMPLE 1 
     According to the above-described embodiments, the batteries  10  are fixed to the thermally conductive members  20 . However, the batteries do not necessarily need to be fixed to the thermally conductive members, and only need to be in contact with the thermally conductive members. The batteries and the thermally conductive members are in contact, so that it is possible to transfer heat generated by the batteries to the case through the thermally conductive members. Consequently, it is possible to improve the cooling efficiency. 
     MODIFIED EXAMPLE 2 
     According to the above-described embodiments, the grip parts  36  and  37  are provided to the pairs of the wall parts  31  and  32  of the case  30 , respectively. However, the grip parts may be provided to one of the wall parts. In a case where the one grip part can grip one end part of the thermally conductive member, it is possible to transfer heat of the batteries to the case while making the manufacturing tolerance of the thermally conductive member greater. 
     MODIFIED EXAMPLE 3 
     According to the above-described embodiments, the plurality of recessed and protrusion parts are formed on the principal surfaces  21  and  22  of the thermally conductive members  20 , and the batteries  10  are fixed to the recessed parts. However, the shape of the thermally conductive member  20  is not limited to this. The thermally conductive member  20  may have a flat plate shape. Furthermore, part of the batteries  10  of the plurality of batteries  10  may be in contact with and fixed to the recessed parts of the thermally conductive member, and part of the other batteries  10  may be in contact with and fixed to flat plate parts of the thermally conductive member. 
     MODIFIED EXAMPLE 4 
     According to the above-described embodiments, each of the recessed part  22   a , the recessed part  22   c,  the recessed part  22   e,  the recessed part  22   g  and the recessed part  22   i  of the principal surface  22  is formed at a position at which each of the protrusion part  21   a,  the protrusion part  21   c,  the protrusion part  21   e,  the protrusion part  21   g  and the protrusion part  21   i  of the principal surface  21  is formed. In other words, the thermally conductive member  20  is a member of a plate shape whose thickness is substantially uniform, and is corrugated in the y axis direction. However, the shape of the thermally conductive member  20  is not limited to this. Furthermore, the batteries  10  are arranged on the both sides of the thermally conductive member  20 , yet may be arranged on one side. 
     MODIFIED EXAMPLE 5 
     According to the above-described embodiments, the battery pack  1  includes the plurality of battery modules  15 . By sliding the individual battery module  15  in the z axis direction with respect to the grip parts  36  and  37 , it is possible to attach and detach the battery module  15  to and from the case  30 . However, the battery modules  15  may be housed in the case in a mode that the battery modules  15  are fixed to the case by bolts or nuts, that is, the battery modules  15  cannot be detached from the case only by sliding the battery modules  15 . 
     MODIFIED EXAMPLE 6 
     According to the above-described embodiments, the gap between the one end part  20   a  of the thermally conductive member  20  gripped by the grip part  36 , and the grip part  36  is filled by the thermally conductive grease  38 . However, a material which fills the gap between the end part of the thermally conductive member  20  and the grip part is not limited to this. A gap between an external surface of the end part of the thermally conductive member and the grip part may be filled by an adhesive material, and the end part of the thermally conductive member and the grip part may be fixed. Furthermore, there may not be a material which fills the gap. 
     Although the present embodiment has been described above based on the embodiments and the modified examples, the above-described embodiments of the present embodiment help to easily understand the present embodiment, and do not limit the present embodiment. The present embodiment can be changed and improved without departing from the spirit of the present embodiment and the claims, and the present embodiment includes equivalents of the changed and improved embodiments. Furthermore, unless technical features of the present embodiment are described as indispensable in this description, the technical features can be deleted as appropriate.