Patent Publication Number: US-2015064521-A1

Title: Battery, assembled battery, and vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a structure of a battery in which a power-generating portion is housed in a case. 
     BACKGROUND ART 
     A battery having a power-generating portion housed in a case is known. Patent Document 1 has disclosed a battery in which a power-generating portion of sheet form is wound around an axis to provide a winding of flat shape and both end portions of the winding are hung in a case. The hanging of the winding in the case locates the winding at a predetermined position in the case. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         [Patent Document 1] Japanese Patent Laid-Open No. 2011-71109 
         [Patent Document 2] Japanese Patent Laid-Open No. 2011-249250 
         [Patent Document 3] Japanese Patent Laid-Open No. 2011-222230 
       
    
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     The configuration described above, however, requires a support member for hanging the winding to result in a large size of the battery. 
     It is thus an object of the present invention to prevent displacement of a power-generating portion in a case while avoiding an increased size of a battery. 
     Means for Solving the Problems 
     To solve the problem described above, the present invention provides (1) a battery including a power-generating portion provided by covering cells with an insulating external material, and a case having a hermetically sealing structure to house the power-generating portion, wherein the case has an internal pressure higher than an external pressure. 
     (2) In the configuration of (1), the power-generating portion is a battery module provided by covering a group of batteries with the external material, the group of batteries including the arranged cells, and the battery module can be housed in the case such that the battery module is folded at an area where a conductive member connecting adjacent ones of the cells is located. According to the configuration of (2), displacement of the cell in the case can be prevented more effectively while avoiding an increased size of the battery. 
     (3) In the configuration of (2), a coolant passage can be provided in which a coolant is passed along a face of the case closest to the conductive member. According to the configuration of (3), cooling of the battery can be performed efficiently by cooling the area close to the position of the battery module where the temperature tends to be higher during charge and discharge. 
     (4) In the configuration of (2) or (3), the case includes first side faces opposite to each other in a first direction, second side faces opposite to each other in a second direction orthogonal to the first direction, a bottom face, and a top face, a pair of extraction electrodes used to extract a power of the battery module to the outside of the case is provided closer to the top face, the number of the cells included in the group of batteries is an even number, and the group of batteries includes a first cell and a second cell, an end portion of the first cell closer to the top face being connected to one of the pair of extraction electrodes through a first connecting member, an end portion of the first cell closer to the bottom face being connected to the conductive member, an end portion of the second cell closer to the top face being connected to the other of the pair of extraction electrodes through a second connecting member, an end portion of the second cell closer to the bottom face being connected to the conductive member. According to the configuration of (4), the connecting members for connecting the group of batteries to the extraction electrodes can be reduced in length. This can reduce the cost. 
     (5) In the configuration of (4), the group of batteries further includes a third cell connected to the first cell through the conductive member and a fourth cell connected to the third cell through the conductive member, the first connecting member is connected to one of a positive electrode and a negative electrode of the first cell, and the conductive member is exposed to the outside of the external material. The battery further includes a first voltage detecting portion connected to the other of the electrodes of the first cell, and a second voltage detecting portion connected to the exposed portion of the conductive member connecting the third cell and the fourth cell. According to the configuration of (5), the voltage of each of the first and third cells can be detected without providing any voltage detecting portion for the connecting member connecting the first cell to the third cell. This can reduce the cost. 
     (6) In the configuration of (5), the first voltage detecting portion can be connected to the end portion of the first cell closer to the top face. 
     (7) An assembled battery including the batteries according to any one of (4) to (6), wherein the pair of extraction electrodes for the cells are arranged along the first direction. 
     (8) The battery according to any one of (1) to (6) can be mounted on a vehicle. In this case, a motor for running the vehicle is driven with a power supplied from the battery. 
     (9) The assembled battery according to (7) can be mounted on a vehicle. In this case, a motor for running the vehicle is driven with a power supplied from the assembled battery. 
     Advantage of the Invention 
     The present invention achieves the object of preventing displacement of the power-generating element in the case while avoiding an increased size of the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A developed view of a battery module. 
         FIG. 2  A section view of the battery module in  FIG. 1  taken along a section X-X′. 
         FIG. 3  A perspective view of a battery in which the battery module is housed. 
         FIG. 4  A section view of the battery in  FIG. 3  taken along a section T-T′. 
         FIG. 5  A diagram for explaining the operation of a processing apparatus for producing cooling fins. 
         FIG. 6  A perspective view of an assembled battery. 
         FIG. 7  A section view of a battery module according to Embodiment 2. 
         FIG. 8  A section view of a battery according to Embodiment 2. 
         FIG. 9  An assembly drawing of an assembled battery of Modification 3. 
         FIG. 10  A schematic diagram showing a modification of a battery case. 
         FIG. 11  A schematic diagram showing another modification of the battery case. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Embodiment 1 
     Referring to the drawings, Embodiment 1 of the present invention will be described.  FIG. 1  is a developed view of a battery module (corresponding to a power-generating portion). An X axis, a Y axis, and a Z axis are three axes orthogonal to each other. The X axis represents a direction orthogonal to a longitudinal direction of the battery module, the Y axis represents the longitudinal direction of the battery module, and the Z axis represents a thickness direction of the battery module.  FIG. 2  is a section view of the battery module taken along a section X-X′ in  FIG. 1 .  FIG. 3  is an external perspective view of a battery in which the battery module is incorporated. A T1 axis, a T2 axis, and a T3 axis are three axes orthogonal to each other.  FIG. 4  is a section view of the battery shown in  FIG. 3  taken along a section T-T′. 
     Referring to  FIG. 1 , a battery module  10  includes a group of batteries  11 , inter-cell connecting tabs (corresponding to a conductive member)  12   a , a positive electrode terminal connecting tab  12   b  (corresponding to a first connecting member), a negative electrode terminal connecting tab  12   c  (corresponding to a second connecting member), and an exterior material  13 . The group of batteries  11  includes a first cell  11   a , a second cell  11   b , a third cell  11   c , and a fourth cell  11   d . The first to fourth cells  11   a  to  11   d  are arranged along the Y direction corresponding to the longitudinal direction of the exterior material  13 . However, the number of the cells  11  may be from one to three, or five or more. The first cell  11   a  is located at one end in the Y axis direction, and the second cell  11   b  is located at the other end in the Y axis direction. 
     The exterior material  13  is formed of film members  13   a  and  13   b . The film members  13   a  and  13   b  hold the first to fourth cells  11   a  to  11   d  between them and are thermally fused to each other at outer edge areas. The thermal fusion of the film members  13   a  and  13   b  hermetically seals in the first to fourth cells  11   a  to  11   d  inside the exterior material  13 . The inter-cell connecting tab  12   a  may be exposed to the outside of the exterior material  13 . 
     The film members  13   a  and  13   b  may be provided by using a flexible sheet having insulation properties. The film members  13   a  and  13   b  may be formed of a laminated film. The exterior material  13  having the insulation properties allows the first to fourth cells  11   a  to  11   d  to be unitized into the single battery module. 
     Referring to  FIG. 2 , the first cell  11   a  includes a positive electrode component  111   a , a negative electrode component  111   b , and a separator  111   c . The positive electrode component  111   a  and the negative electrode component  111   b  are stacked with the separator  111   c  interposed between them. In the following description, the direction in which the positive electrode component  111   a , the negative electrode component  111   b , and the separator  111   c  are stacked may be referred to as a stack direction. Each of the first to fourth cells  11   a  to  11   d  may be a secondary battery such as a nickel metal hydride battery or a lithium-ion battery, or a capacitor. In  FIG. 2 , the positive electrode component  111   a , the negative electrode component  111   b , and the separator  111   c  are partially omitted. 
     The positive electrode component  111   a  includes a collector and a positive electrode layer formed on a surface of the collector. The positive electrode layer includes a positive electrode active material layer, a conductive agent and the like. The positive electrode active material may be a Li—Co composite oxide such as LiCoO 2 , a Li—Ni composite oxide such as LiNiO 2 , a Li—Mn composite oxide such as spinel LiMn 2 O 4 , and a Li—Fe composite oxide such as LiFeO 2 . The positive electrode active material may be a phosphate compound of a transition metal and lithium such as LiFePO 4  or a sulfated compound, a transition metal oxide or sulfide such as V 2 O 5 , MnO 2 , TiS 2 , MoS 2 , and MoO 3 , or PbO 2 , AgO, NiOOH. 
     The negative electrode component  111   b  includes a collector and a negative electrode layer formed on a surface of the collector. The negative electrode layer includes the negative electrode active material layer, a conductive agent and the like. The negative electrode active material may be a metal oxide, a lithium-metal composite oxide, and carbon. 
     The positive electrode terminal connecting tab  12   b  is connected to one end of the first cell  11   a  in the stack direction. The positive electrode terminal connecting tab  12   b  is connected to a general positive terminal  21  (corresponding to an extraction electrode) of a battery  1 . The connection between the positive electrode terminal connecting tab  12   b  and the general positive terminal  21  may be made through ultrasonic welding or spot welding. 
     The negative electrode terminal connecting tab  12   c  is connected to one end of the second cell  11   b  in the stack direction. The negative electrode terminal connecting tab  12   c  is connected to a general negative terminal  22  (corresponding to an extraction electrode) of the battery  1 . The connection between the negative electrode terminal connecting tab  12   c  and the general negative terminal  22  may be made through ultrasonic welding or spot welding. 
     The separator  111   c  contains an electrolyte. The electrolyte may be a solid electrolyte or an electrolytic solution. The solid electrolyte may be provided by using a polymer solid electrolyte or an inorganic solid electrolyte. Examples of the polymer solid electrolyte may be polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof. The polymer solid electrolyte may contain lithium salt to ensure ion conductivity. Examples of the lithium salt can include LiBF 4 , LiPF 6 , LiN(SO 2 CF 3 ) 2r  LiN(SO 2 C 2 F 5 ) 2 , or a mixture thereof. 
     Referring to  FIG. 3  and  FIG. 4 , the battery module  10  is housed in a battery case  30 . The battery case  30  includes a pair of first case side faces  30   a  opposite to each other in a T3 axis direction (corresponding to a first direction) a pair of second case side faces  30   b  opposite to each other in a T1 axis direction (corresponding to a second direction), a case bottom face  30   c , and a case top face  30   d . In  FIG. 3 , the case top face  30   d  is omitted. 
     A case body consisting of the first case side faces  30   a , the second case side faces  30   b , and the case bottom face  30   c , and the case bottom face  30   d  may be manufactured as separate components. The case body can be manufactured, for example, through press forming. The case top face  30   d  can be fixed through welding to inner faces of the first case side faces  30   a  and the second case faces  30   b . The battery case  30  can be formed by using metal. 
     The battery module  10  is folded at a bend portion  10   a . The bend portion  10   a  is formed at an intermediate portion between the adjacent cells, that is, in an area where the inter-cell connecting tab  12   a  connecting the adjacent cells is located. 
     An end of the first cell  11   a  closer to the case top face  30   d  is connected to the general positive terminal  21  through the positive electrode terminal connecting tab  12   b , and an end of the first cell  11   a  closer to the case bottom face  30   c  is connected to the third cell  11   c  through the inter-cell connecting tab  12   a.    
     An end of the second cell  11   b  closer to the case top face  30   d  is connected to the general negative terminal  22  through the negative electrode terminal connecting tab  12   c , and an end of the second cell  11   b  closer to the case bottom face  30   c  is connected to the fourth cell  11   d  through the inter-cell connecting tab  12   a.    
     The folded battery module  10  is housed in the battery case  30  in this manner to allow effective use of the space inside the battery case  30 . This prevents an increase in size of the battery  1 . 
     The setting of the number of the cells constituting the group of batteries  11  at an even number and the folded battery module  10  housed in the battery case  30  can reduce the distance between the general positive terminal  21  and the portion of the first cell  11   a  connected to the positive electrode terminal connecting portion  12   b . This can reduce the length of the positive electrode terminal connecting portion  12   b . Similarly, the distance between the general negative terminal  22  and the portion of the second cell  11   b  connected to the negative electrode terminal connecting portion  12   c  can be reduced. This can reduce the length of the negative electrode terminal connecting portion  12   c.    
     A cooling duct  31  is provided at the case bottom face  30   c . The cooling duct  31  includes cooling fins  31   a  and a duct wall portion  31   b . The cooling fins  31   a  are in contact with the case bottom face  30   c  and are provided at predetermined intervals in a longitudinal direction (T1 axis direction) of the case bottom face  30   c . The cooling fins  31   a  can be formed by using metal having a high thermal conductivity. The metal may be aluminum. 
       FIG. 5  shows diagrams for explaining the operation of a processing apparatus for producing the cooling fins. The processing proceeds in the order from (a) to (e). An impact molding apparatus can be used as the processing apparatus. The impact processing apparatus includes a punch  81  and a die  82 . The punch  81  moves into and out of a recessed portion of the die  82 . The punch  81  is driven by a motor, not shown. A slag M serving as a base material of the cooling fins is placed in the recessed portion of the die  82 . The slag M may be an ingot of cylindrical form made of aluminum. 
     When the punch  81  is lowered toward the recessed portion of the die  82 , the slag M is crushed, and part of the crushed slag M is squeezed out of a gap between the punch  81  and the die  82  to form the cooling fin  31   a . According to the method, the cooling fins  31   a  can be manufactured simply by lowering the punch  81  toward the die  82 . In addition, the cost of a mold can be reduced to prevent an increase in manufacture cost of the battery  1 . 
     The space surrounded by the case bottom face  30   c , the cooling fins  31   a , and the duct wall portion  31   b  provides a coolant path for passing a coolant. The coolant passed in the coolant path can cool the case bottom face  30   c  and the battery module  10 . This avoids deterioration of the first to fourth cells  11   a  to  11   d . The coolant may be air or a heat exchange medium in liquid form. 
     The bend portion  10   a  may have a temperature higher than that of the remaining portion when the battery module  10  is charged and discharged. Since the inter-cell connecting tab  12   a  is located at the bend portion  10   a , the temperature of generated heat during charge and discharge of the battery module  10  is relatively high. Since the bend portion  10   a  is in contact with the case bottom face  30   c , and the cooling fins  31   a  are in contact with the case bottom face  30   c , the coolant flowing in the cooling duct  31  can efficiently cool the first to fourth cells  11   a  to  11   d.    
     The internal pressure of the battery case  30  is set to be higher than the external pressure. The higher internal pressure of the battery case  30  may be achieved by supplying an inert gas (for example, nitrogen gas) or air into the battery case  30 . The inert gas or the like fed into the battery case  30  provides a pressurized atmosphere in the battery case  30  to press the battery module  10  against the inner face of the battery case  30 . 
     The pressing of the battery module  10  can avoid displacement of the battery module  10 . The avoidance of displacement of the battery module  10  can prevent the exterior material  13  of the battery module  10  from rubbing against the inner wall of the battery case  30  and being worn. In addition, the pressing of the battery module  10  can bring the positive electrode component  111   a , the negative electrode component  111   b , and the separator  111   c  constituting the power-generating element of the cell into closer contact with each other to prevent deterioration of input/output characteristics of the battery module  10 . 
     A known method of restraining the battery module  10  in the battery case  30  is to attach a restraint member externally to the battery case  30  such that the restraint member presses the battery case. The method, however, requires the attachment of the restraint member to the battery case  30 , so that the assembly process is complicated and the cost is increased. According to the battery  1  of the present embodiment, the battery module  10  can be restrained without using the restraint member. As a result, the increase in cost can be prevented while the complication of the assembly process is avoided. 
     The restraint of the battery module  10  with the internal pressure of the battery case  30  can eliminate the need of a support member for hanging the battery module  10  in the battery case  30 . This increases the space in the battery case  30  for placing the battery module  10 , so that the battery module  10  can be increased in size while an increased size of the battery  1  is prevented. 
     When the battery is in an abnormal condition such as overcharge and overdischarge, the first to fourth cells  11   a  to  11   d  may discharge gas to increase the internal pressure of the gas exterior material  13 . Since the gas exterior material  13  is pressurized from outside by the pressure inside the battery case  30  in the present embodiment, any outflow of the gas from the exterior material  13  can be prevented. 
     Since the exterior material  13  of the battery module  10  has the insulation properties and the battery case  30  does not have any electric potential, no insulating treatment is required on the inner face of the battery case  30 . This can reduce the cost. 
     A laminated film containing aluminum is widely known as a material for use in hermetically sealing in the cell. The laminated film containing aluminum has water cut-off performance and can prevent entry of moisture into the cell. In the present embodiment, the battery case  30  is made of metal which can prevent entry of moisture into the cell from the outside. Thus, the exterior material  13  in the present embodiment may be provided by using a laminated film which does not contain aluminum. This can enhance the flexibility in selecting the material. 
     The battery  1  described above can be mounted on a vehicle. The battery  1  supplies power to a motor for running the vehicle. The motor is operated to rotate with the power supplied by the battery  1  to run the vehicle. The vehicle may be an electric car having only the battery  1  as the power source for running the vehicle, or a hybrid car having the battery  1  and another element (for example, an internal-combustion engine or a fuel cell) used in combination as the power source. The hybrid car includes a plug-in hybrid car in which the battery  1  can be charged with a power source provided externally to the vehicle. As shown in  FIG. 6 , an assembled battery A including a plurality of such batteries  1  connected to each other may be mounted on the vehicle. The assembled battery A supplies power to the motor for running the vehicle to run the vehicle. 
     Embodiment 2 
     A battery according to Embodiment 2 will hereinafter be described in detail with reference to drawings.  FIG. 6  is a developed view of a battery module (corresponding to power-generating portion)  100 .  FIG. 7  is a section view of the battery and corresponds to  FIG. 4 . The battery module  100  includes a first cell  51 , a second cell  52 , a third cell  53 , and a fourth cell  54 . The first cell  51  is located at one end of the battery module  100 , and the second cell  51  is located at the other end of the battery module  100 . 
     The first cell  51  is formed by stacking a positive electrode component  51   a  and a negative electrode component  51   b  with a separator interposed between them. Since the positive electrode component  51   a  and the negative electrode component  51   b  have the same configurations as those of the positive electrode component  111   a  and the negative electrode component  111   b  in Embodiment 1, respectively, detailed description thereof is omitted. Since the second to fourth cells  52  to  54  have the same configuration as that of the first cell  51 , detailed description thereof is omitted. 
     The positive electrode component  51   a  of the first cell  51  is connected to a positive electrode terminal  57  (corresponding to an extraction electrode) of the battery through a positive electrode terminal connecting tab  43  (corresponding to a first connecting member). The negative electrode component  51   b  of the first cell  51  is connected to a voltage detecting tab  41   a  (corresponding to a first voltage detecting portion). The negative electrode component  51   b  of the first cell  51  and a positive electrode component  53   a  of the third cell  53  are electrically and mechanically connected to each other through an inter-cell connecting tab  42   a  (corresponding to a conductive member). A negative electrode component  53   b  of the third cell  53  and a positive electrode component  54   a  of the fourth cell  54  are electrically and mechanically connected to each other through an inter-cell connecting tab  42   b  (corresponding to a conductive member). A negative electrode component  54   b  of the fourth cell  54  and a positive electrode component  52   a  of the second cell  52  are electrically and mechanically connected to each other through an inter-cell connecting tab  42   c  (corresponding to a conductive member). A negative electrode component  52   b  of the second cell  52  is connected to a negative electrode terminal  58  (extraction electrode) of the battery through a negative electrode terminal connecting tab  44  (corresponding to a second connecting member). 
     As shown in  FIG. 7 , the battery module  100  is folded at a boundary portion between adjacent cells and is housed in a battery case  59 , similarly to the battery module  10  in Embodiment 1. The inter-cell connecting tab  42   b  connecting the third cell  53  and the fourth cell  54  is exposed to the outside of an exterior material  13 , and a voltage detecting terminal  56  (corresponding to a second voltage detecting portion) is in contact with the exposed portion. The inter-cell connecting tab  42   b  has elasticity. The inter-cell connecting tab  42   b  is pressed against the voltage detecting terminal  56  through the elasticity. Alternatively, the inter-cell connecting tab  42   b  and the voltage detecting terminal  56  may be bonded to each other by welding. 
     The positive electrode terminal connecting tab  43 , the voltage detecting tab  41   a , the voltage detecting terminal  56 , the negative electrode terminal connecting tab  44 , and the voltage detecting tab  41   b  are electrically connected to a monitor unit, not shown. The monitor unit transmits voltage information acquired from the positive electrode terminal connecting tab  43 , the voltage detecting tab  41   a , the voltage detecting terminal  56 , the negative electrode terminal connecting tab  44 , and the voltage detecting tab  41   b  to an ECU (Electric Control Unit), not shown. The ECU calculates the voltage of the first cell  51  based on the voltage information acquired through the positive electrode terminal connecting tab  43  and the voltage detecting tab  41   a . The ECU calculates the voltage of the third cell  53  based on the voltage information acquired through the voltage detecting tab  41   a  and the voltage detecting terminal  56 . The ECU calculates the voltage of the fourth cell  54  based on the voltage information acquired through the voltage detecting terminal  56  and the voltage detecting tab  41   b . The ECU calculates the voltage of the second cell  52  based on the voltage information acquired through the negative electrode terminal connecting tab  44  and the voltage detecting tab  41   b.    
     According to the configuration described above, the voltages of the cells  51  to  54  can be detected without providing the voltage detecting tab for the respective adjacent cells. This can reduce the cost of the battery. 
     When the number of the cells is an even number as shown in  FIG. 7 , the positive electrode terminal connecting tab  43 , the voltage detecting tab  41   a , the voltage detecting terminal  56 , the negative electrode terminal connecting tab  44 , and the voltage detecting tab  41   b  can be collectively provided at one end side of the battery case  59 . The arrangement can integrate the voltage detection paths into a bus bar module. The bus bar module refers to a unit of a plurality of bus bars used in an assembled battery including a plurality of batteries in which each of the bus bars connects the adjacent batteries. The bus bar module is used to facilitate the installation of the bus bars. 
     Modification 1 
     Although the positive electrode component  111   a , the negative electrode component  111   b , and the separator  111   c  are stacked in the predetermined direction to constitute the cell in the embodiments described above, the present invention is not limited thereto. For example, the positive electrode component  111   a  and the negative electrode component  111   b  may be stacked with the separator  111   c  interposed between them to provide a stack sheet, and the stack sheet may be wound around a predetermined axis to form a winding which constitutes the cell. 
     Modification 2 
     Although the cooling duct  31  is disposed along the case bottom face  30   c  of the battery case  30  in the embodiments described above, the present invention is not limited thereto, and the cooling duct  31  may be provided at a different position. The different position may be at the case side face  30   b  of the battery case  30 . In another modification, the cooling duct  31  may be omitted. 
     Modification 3 
     Although the number of the cells included in the battery is an even number in the embodiments described above, the present invention is not limited thereto, and the number may be an odd number.  FIG. 9  is an assembly drawing of an assembled battery including batteries connected in serial in which each of the batteries includes an odd number (for example, five) of cells. An assembled battery  80  includes a first battery  81 , a second battery  82 , and a third battery  83 . The first battery  81  includes first to fifth cells  81   a  to  81   e . Since the second to third batteries  82  to  83  have the same configuration as that of the first battery  81 , detailed description thereof is omitted. 
     A positive electrode terminal  86   a  and a negative electrode terminal  86   b  of the first battery  81  are formed on different faces. In this case, as shown, the negative electrode terminal  86   b  of the first battery  81  and a positive electrode terminal  86   c  of the second battery  82  can be extended along outer faces of the first and second batteries  81  and  82  to electrically connect the first battery  81  to the second battery  82 . Similarly, a negative electrode terminal  86   d  of the second battery  82  and a positive electrode terminal  86   e  of the third battery  83  can be extended along outer faces of the second and third batteries  82  and  83  to electrically connect the second battery  82  to the third battery  83 . The number of the batteries included in the assembled battery can be set as appropriate in view of the yields of materials, processing equipment, mount space and the like. 
     Modification 4 
     Although the battery case  30  is formed of the case body consisting of the first case side faces  30   a , the second case side faces  30   b , and the case bottom face  30   c , and the case top face  30   d  in the embodiments described above, the present invention is not limited thereto. As shown in  FIG. 10 , the battery case  30  may be provided by bonding a case a and a case b of bottomed tubular form at their end portions. In this case, the battery module  10  ( 100 ) housed in the battery case  30  is pressed by the inner faces of the cases. The case a and the case b having the common shape can reduce the cost of the battery. In addition, as shown in  FIG. 11 , the battery case  30  may be provided by bonding a side wall c of flat plate shape and a case d of bottomed tubular shape at their end portions. In this case, the battery module  10  ( 100 ) housed in the battery case  30  is pressed by the inner faces of the cases. The parts such as the positive electrode terminal can be collectively placed at an upper wall portion dl of the case d. 
     Modification 5 
     The positive electrode terminal connecting tab  12   b  (negative electrode terminal connecting tab  12   c ) connected to the general positive terminal  21  (general negative terminal  22 ) may sag. This provides so-called play in the positive electrode terminal connecting tab  12   b  (negative electrode terminal connecting tab  12   c ) to reduce a load on the positive electrode terminal connecting tab  12   b  (negative electrode terminal connecting tab  12   c ) during vibration of the battery. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
           1  BATTERY  10  BATTERY MODULE  11  GROUP OF BATTERIES 
           11 A TO  11 D FIRST TO FOURTH CELLS  12 A INTER-CELL CONNECTING TAB 
           12 B POSITIVE ELECTRODE TERMINAL CONNECTING TAB  12 C NEGATIVE ELECTRODE TERMINAL CONNECTING TAB 
           30  BATTERY CASE  31  COOLING DUCT