Abstract:
An electricity storage device includes: a plurality of batteries juxtaposed in a first direction, each battery having on a first side a gas discharge valve that discharges a gas produced inside the battery; and a cooling path formed between the plurality of batteries that face each other in the first direction, constructed to convey a coolant that cools the batteries, and an intake opening for taking in the coolant on a second side that is an opposite side to the first side in a second direction orthogonal to the first direction and a discharge opening for discharging the coolant taken in on at least one of sides in a third direction orthogonal to the second direction and to the first direction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an electricity storage device. 
         [0003]    2. Description of Related Art 
         [0004]    There exists an electricity storage device which has: a plurality of electricity storage elements that are juxtaposed in a predetermined direction and that is each equipped with a valve that discharges gas produced inside; a pair of end plates that clamp the electricity storage elements in the predetermined direction; a plurality of connecting members that extend in the predetermined direction and that are fixed to the two end plates; and a case for housing the electricity storage elements, and in which the connecting members are disposed along external surfaces of the electricity storage elements on which the valves are provided, and contact an internal wall surface of the case, and form, together with the case, a space in which gas discharged from the valves moves (see, e.g., Japanese Patent Application Publication No. 2012-109126 (JP-A-2012-109126)). In this electricity storage device, air that cools the electricity storage elements flows in a longitudinal direction, that is, from a side opposite to the side where the valves are provided toward the side where the valves are provided. The air having cooled the electricity storage elements is discharged to an outside through a discharge path that is shared with the gas discharged from the valves. 
       SUMMARY OF THE INVENTION 
       [0005]    However, in the construction described in JP-A-2012-109126, the air that cools the electricity storage elements flows from an intake opening that is provided on the opposite side to the side provided with valves toward a discharge opening that is provided on the valve-provided side, and this flowing direction gives rise to a problem that a cooling path for the battery and a discharge path for gas produced inside the battery (a smoke discharge path) cannot be separated from each other. 
         [0006]    Accordingly, the invention provides an electricity storage device in which a cooling path for a battery and a smoke discharge path can be separated from each other. 
         [0007]    According to an aspect of the invention, an electricity storage device includes: a plurality of batteries juxtaposed in a first direction, each battery having on a first side a gas discharge valve that discharges a gas produced inside the battery; and a cooling path formed between the plurality of batteries that face each other in the first direction, constructed to convey a coolant that cools the batteries, and having an intake opening for taking in the coolant on a second side that is an opposite side to the first side in a second direction orthogonal to the first direction and a discharge opening for discharging the coolant taken in on at least one of sides in a third direction orthogonal to the second direction and to the first direction. 
         [0008]    Furthermore, in the foregoing aspect, the discharge opening may be provided on each of a third side and a fourth side that are two sides in the third direction. 
         [0009]    Furthermore, in the foregoing aspect, a sectional area of the intake opening may be smaller than a sectional area of the discharge opening provided on at least one of the sides in the third direction. Further, the sectional area of the intake opening may be smaller than a sum of a sectional area of the discharge opening on a third side that is a side in the third direction and a sectional area of the discharge opening on a fourth side that is another side in the third direction. 
         [0010]    Furthermore, in the foregoing aspect, the cooling path may have a T shape as a whole in a section orthogonal to the first direction, and may include a path portion that extends from the intake opening toward the first side and then extends toward a third side that is a side in the third direction and a path portion that extends from the intake opening toward the first side and then extends toward a fourth side that is another side in the third direction. 
         [0011]    Furthermore, in the foregoing aspect, the electricity storage device may further include: a partition plate provided between the plurality of batteries in the first direction and having a rib, and the cooling path may be at least partially defined by the rib. 
         [0012]    Furthermore, in the foregoing construction, the rib may extend from the second side to the first side in the second direction and turns into the third direction. 
         [0013]    Furthermore, in the foregoing aspect, the electricity storage device may further include a smoke discharge path formed for the plurality of batteries at the first side in the second direction and constructed to discharge to an outside the gas discharged from the gas discharge valve of each battery, and the cooling path may be formed in such a manner that the cooling path does not communicate with the smoke discharge path. 
         [0014]    Furthermore, in the foregoing aspect, the electricity storage device may further include: a plurality of partition plates provided between the plurality of batteries that face each other in the first direction and, each partition plate having connecting portions that are protruded at the second side in the second direction and that extend in two rows in the first direction; and a cover member disposed for the connecting portions of the plurality of partition plates at the second side in the second direction, and a supply path for supplying the coolant to the cooling path may be at least partially defined by the cover member and the connecting portions of the partition plates. 
         [0015]    Furthermore, in the foregoing aspect, the electricity storage device may further include: a plurality of partition plates provided between the plurality of batteries that face each other in the first direction and, each partition plate having connecting portions that are protruded at the first side in the second direction and that extend in two rows in the first direction; a cover member disposed for the connecting portions of the plurality of partition plates at the first side in the second direction; a pair of end plates disposed on two end sides of the plurality of batteries in the first direction; and an arresting member whose two ends are coupled to the pair of end plates and which extends over the plurality of batteries in the first direction at the first side in the second direction and which gives arresting force in the first direction to the plurality of batteries, and a smoke discharge path constructed to discharge to an outside the gas discharged from the gas discharge valve of each battery may be at least partially defined by the cover member and the connecting portions of the partition plates, and the connecting portions may define, inside the connecting portions, hollow portions that extend in the first direction, and the arresting member may extend in at least one of the hollow portions. 
         [0016]    Furthermore, in the foregoing construction, the cover member may be made of metal. 
         [0017]    According to the foregoing aspect, an electricity storage device that allows a battery cooling path and a smoke discharge path to be separated from each other can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0019]      FIG. 1  is an external view schematically showing a battery pack  100  according to an embodiment of the invention; 
           [0020]      FIG. 2  is a diagram schematically showing a section of the battery pack  100  taken on a Y-Z plane; 
           [0021]      FIG. 3  is a diagram schematically showing an example of a partition member  30  in a view taken in an X direction; 
           [0022]      FIG. 4  is a diagram schematically showing an example of the partition member  30  in a view taken in a Y direction; 
           [0023]      FIG. 5  is a diagram schematically showing a manner in which a coolant (air) and a gas flow in the battery pack  100 ; 
           [0024]      FIG. 6  is a diagram schematically showing the flowing manner of the coolant in the battery pack  100  (in a supply path S 2 ) in a view taken in a Y direction; 
           [0025]      FIG. 7  is a diagram schematically showing the flowing manner of the coolant in the battery pack  100  (in cooling paths S 3 ) in a view taken in an X direction; and 
           [0026]      FIGS. 8A and 8B  are diagrams each schematically showing a cooling method according to a comparative example; and 
           [0027]      FIG. 9  is a diagram schematically showing a partition member  300  according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0028]    Best modes for carrying out the invention will be described hereinafter with reference to the drawings. 
         [0029]      FIG. 1  is an external view schematically showing a battery pack  100  according to an embodiment of the invention. In  FIG. 1 , a pack case  50 , only an upper portion of which is shown, is apart from a battery stack  1  for the sake of convenience in illustration.  FIG. 2  is a diagram schematically showing a sectional view of the battery pack  100  taken on a Y-Z plane. In  FIG. 1  and  FIG. 2 , X directions, Y directions and Z directions are orthogonal to one another. Incidentally, although up-down directions, left-right directions, etc. change according to the mounted state of the electricity storage device or the direction of view, it is assumed in the following description that the Z directions correspond to vertical directions (up-down directions) and an upper side in the drawings is an “upper side” with reference to the illustration in each drawing, for the sake of convenience. Furthermore, the Y directions are assumed to correspond to the left-right directions with reference to the illustrations in the drawings. 
         [0030]    The battery pack  100  can be mounted in a vehicle. Such vehicles include hybrid motor vehicles and electric motor vehicles. A hybrid motor vehicle is a vehicle equipped with an electric motor and an internal combustion engine as motive power sources for moving the vehicle. An electric motor vehicle is a vehicle equipped with only an electric motor as a motive power source of the vehicle. In either type of vehicle, the battery pack  100  may be used as an electric power source of the electric motor. 
         [0031]    The battery pack  100  includes the battery stack  1  and the pack case  50 . 
         [0032]    The battery stack  1  has a plurality of electric cells  10 . The electric cells  10  are juxtaposed (stacked) in the X directions as shown in  FIG. 1 . 
         [0033]    The pack case  50  is an example of a cover member, and is an exterior package that houses the entire battery stack  1 . That is, the pack case  50  is provided so as to cover the upper and lower surfaces (end surfaces in the Z directions), two opposite side surfaces (end surfaces in the Y directions) and other two opposite side surfaces (end surfaces in the X directions) of the entire battery stack  1 . The pack case  50  may be formed from a metal (e.g., a platy metal member). The pack case  50  may also be constructed by combining a plurality of members. Ducts, such as an air intake duct  61 , a smoke discharge duct  62 , etc., may be connected to the pack case  50  so as to communicate with the inside of the pack case  50  (see  FIG. 5 ). 
         [0034]    The electric cells  10  may be any secondary cells such as nickel-hydrogen cells or lithium-ion cells. Furthermore, the electric cells  10  may also be electric double layer capacitors (condensers) instead of secondary cells. The number of electric cells  10  may be determined as appropriate on the basis of the demanded output of the battery stack  1  and the like. 
         [0035]    The upper surface of each electric cell  10  is provided with a positive terminal  11  and a negative terminal  12 . The positive terminal  11  and the negative terminal  12  of each electric cell  10  are provided apart from each other by a predetermined distance. The electric cells  10  may be electrically connected in series. Concretely, the positive terminal  11  of one electric cell  10  and the negative terminal  12  of another electric cell  10  may be electrically connected by a bus bar (not shown). That is, the electric cells  10  may be electrically connected in series. 
         [0036]    A valve  13  is provided on the upper surface of each electric cell  10 . The valve  13  is used to discharge gas produced inside the electric cell  10  to the outside of the electric cell  10 . Since the inside of the electric cell  10  is tightly closed, the internal pressure of the electric cell  10  rises as gas is produced inside the electric cell  10  if any is produced. When the internal pressure of the electric cell  10  reaches an actuation pressure of the valve  13 , the valve  13  changes from a closed state to an open state. In this manner, the gas produced inside the electric cell  10  can be discharged to the outside of the electric cell  10 . 
         [0037]    The valve  13  is disposed between the positive terminal  11  and the negative terminal  12  in the Y directions. In the example shown in  FIG. 1 , the valve  13  is disposed at a position that is equidistant from, the positive terminal  11  and the negative terminal  12 . Due to the provision of the valve  13  on the upper surface of the electric cell  10 , the gas produced inside the electric cell  10  can easily be discharged from the valve  13 . Incidentally, the position at which the valve  13  is provided can be set as appropriate. 
         [0038]    Incidentally, the construction of the valve  13  is arbitrary, and may be, for example, a generally termed rupture valve or a generally termed return valve. The rupture valve is a valve that irreversibly changes from the closed state to the open state. For example, a rupture valve can be constructed by forming a marking on a portion of the battery case. The return valve is a valve that reversibly changes between the closed state and the open state. That is, the return valve changes between the closed state and the open state according to the magnitude relation between the pressure inside the electric cell  10  and the pressure outside. The return valve can be constructed, for example, of a lid that closes a gas movement path and a spring that urges the lid in one direction. 
         [0039]    A partition member  30  is disposed between two electric cells  10  adjacent to each other in the X directions. Each partition member  30  functions as a spacer. The partition members  30  may be formed from an insulation material such as resin or the like. Each partition member  30  has a plurality of connecting portions  42  that are protruded upward or downward as shown in  FIG. 2 . Concretely, each partition member  30  has two connecting portions  42  that are protruded from an upper side thereof at the two opposite sides of the valve  13  in the Y directions, and has two similar connecting portions  42  that are protruded from the lower side of the partition member  30 . Incidentally, the heights (lengths in the Z directions) and positions of the connecting portions  42  may be different between the upper side and the lower side. Incidentally, further details of the partition member  30  will be described later. 
         [0040]    A pair of end plates  41  are disposed at two opposite ends of the battery stack  1  in the X directions. Arresting members (flat plate bands)  46  are coupled to the end plates  41 . Two arresting members  46  may be provided at an upper side of the battery stack  1 . The two arresting members  46  are apart from each other in the Y directions, and extend in the X directions, and are each connected at its two opposite ends to the two end plates  41  Incidentally, the method of fixing the arresting members  46  to the end plates  41  is arbitrary; for example, a fixing method that uses bolts, a fixing method that uses rivets, and other fixing methods, such as welding, can be used. Similarly, two arresting members  46  may also be provided at the lower side of the battery stack  1 . The arresting members  46  have a function of giving arresting force to the plurality of electric cells  10 . The arresting force is a force that clamps the electric cells  10  in the X directions. By giving arresting force to the electric cells  10 , the electric cells  10  can be, for example, restrained from expanding. In the construction in which two arresting members  46  are provided on each of the upper and lower sides of the battery stack  1 , concentration of arresting force to a single site is prevented, and substantially equal arresting forces can be given to the electric cells  10 . 
         [0041]    A smoke discharge path S 1  is formed at the upper surface side of the electric cell  10 , as shown in  FIG. 2 . The smoke discharge path S 1  communicates with the inside of each electric cell  10  via the valve  13  of the electric cell  10 . Therefore, the smoke discharge path S 1  serves to discharge the gas produced inside each electric cell  10  to the outside of the battery pack  100 . The smoke, discharge path S 1 , as shown in  FIG. 2 , is defined by the upper-side connecting portions  42  of each partition member  30 , the pack case  50  and the upper surfaces of the electric cells  10 . The smoke discharge path S 1  may extend in the X directions, and may be open at one of the two ends (see  FIG. 5 ) and closed at the other end. Preferably, seal members  70  are provided between the pack case  50  and upper edges of the upper-side connecting portions  42  of each partition member  30 . The seal members  70  may be formed from, for example, sponge or rubber. The seal members  70  extend in the X directions along the connected connecting portions  42  at the upper side of the partition members  30 . The provision of the seal members  70  improves air-tightness, and reduces leakage of gas from the smoke discharge path S 1 . Incidentally, the smoke discharge path S 1  may have a consistent cross-section or may have a cross-section that changes from one side toward the other in the X directions. 
         [0042]    A supply path S 2  is formed at a lower surface side of the electric cells  10 , as shown in  FIG. 2 . The supply path S 2  is supplied with coolant from a coolant supply source (not shown) provided outside. The coolant is typically a gas such as air, but may also be another type of fluid, such as water or the like. Incidentally, the coolant is assumed to be air in the following description. The supply path S 2 , as shown in  FIG. 2 , is defined by the lower-side connecting portions  42  of each partition member  30 , the pack case  50  and the lower surfaces of the electric cells  10 . The supply path S 2  may extend in the X directions, and may be open at one of the two ends (see  FIG. 5 ) and closed at the other end. Seal members  70  may be provided between the pack case  50  and lower edges of the lower-side connecting portions  42  of the partition members  30 . The provision of the seal members  70  improves air-tightness, and reduces leakage of the coolant that passes through the supply path S 2 . Incidentally, the supply path S 2  may have a consistent cross-section, or may also have a cross-section that changes from one side to the other side in the X directions. 
         [0043]      FIG. 3  is a diagram schematically showing an example of a partition member  30  in a view taken in one of the X directions.  FIG. 4  is a diagram showing an example of a partition member  30  in a view taken in one of the Y directions. 
         [0044]    Each partition member  30  has connecting portions  42  on its upper and lower portions. The connecting portions  42  are provided at two locations on the upper portion and at two locations on lower portion. The connecting portions  42  are protruded upward and downward relative to the upper surface and the lower surface of each electric cell  10 , as shown in  FIG. 2 . The connecting portions  42 , as shown in  FIG. 3 , are formed so as to be hollow in a view in the X directions. That is, each of the connecting portions  42  has a hole  44  that extends in the X directions. Besides, the connecting portions  42  extend in the X directions as shown in  FIG. 4 . Each connecting portion  42 , as shown in  FIG. 4 , has a large-diameter portion  42   a  and a small-diameter portion  42   b.  Two partition members  30  adjacent to each other in the X directions are interconnected by fitting the small-diameter portions  42   b  of the connecting portions  42  of one of the two partition members  30  into holes  43  of the large-diameter portions  42   a  of the other partition member  30 . In this connected state, the upper-side connecting portions  42  of the partition members  30  define two side wall portions of the smoke discharge path S 1  (see  FIG. 2 ) that extend in the X directions. Furthermore, in this connected state, the holes  44  in the connecting portions  42  are connected to each other so as to form hollow portions that extend in the X directions. The arresting members  46  (see  FIG. 2 ) made of metal are inserted through the hollow portions. Furthermore, in this connected state, a space between two partition members  30  adjacent to each other in the X directions accommodates placement of a corresponding one of the electric cells  10 . That is, because two partition members  30  are interconnected while being positioned on two opposite sides of an electric cell  10  in the X directions, the electric cell  10  is disposed between the two partition members  30  adjacent to each other in the X directions. 
         [0045]    Each partition member  30  has on a surface that faces one of the two adjacent electric cells  10  a plurality of ribs  32  that are protruded in an X direction. In each partition member  30 , a surface opposite to the surface provided with the ribs  32 , that is, a surface that faces the other one of the adjacent electric cells  10 , may be a flat surface that has a surface contact with the electric cell  10  (see  FIG. 4 ). 
         [0046]    The ribs  32  are formed in the shape of T as a whole as shown in  FIG. 3 . That is, the ribs  32  extend in one of the Z directions from the lower side (air intake side), and then turn their direction into the Y directions. Therefore, the ribs  32  define T-shaped cooling paths S 3  that extend in a Z direction from the lower side (air intake side), and then turn their direction into the Y directions, and extend toward the two edge portions of the partition member  30  in the Y directions. That is, there are defined the cooling paths S 3  for causing the coolant to flow in the T-shaped course on the end surface of the electric cell  10  (end surface in the X direction). In an example shown in  FIG. 3 , the ribs  32  are formed symmetrically about a center line along the Z directions that passes through a center of the partition member  30  in the Y directions. Concretely, a central rib  32   a  extends in the Z direction from a center of the lower side of the partition member  30  in the Y directions, and then forks toward the two opposite sides (left and right sides) in the Y directions. Ribs  32   b  and  32   c  on the right side extend in the Z direction from the lower side of the partition member  30 , and then turn their direction to one of the. Y directions (the rightward direction) and extend in that direction. The ribs  32   b  and  32   c  on the left side extend in the Z direction from the lower side, and turn their direction to the other one of the Y directions (the leftward direction) and extend in that direction. Ribs  32   d  extend in the Y directions. 
         [0047]    Incidentally, the number of ribs  32 , and the intervals between two mutually adjacent ribs  32  can be set as appropriate. Furthermore, the heights of the ribs  32  (the heights in the X directions) are arbitrary, and can be set as appropriate. For example, the heights of the ribs  32  may be set so that distal ends of the ribs  32  contact the adjacent electric cell  10 , or may also be set so that the distal ends of the ribs  32  do not contact the electric cell  10 . However, as described below, in order to prevent mixture of streams of the coolant moving though the cooling paths S 3  defined by ribs  32  (in order to cause the coolant to flow through a T-shaped course on the end surface of the electric cell  10  (the end surface thereof in the X direction), the heights of the ribs  32  are preferably set so that the distal ends of the ribs  32  contact the end surface of the electric cell  10  in the X direction. Incidentally, the ribs  32  may be formed on both sides of each partition member  30 . 
         [0048]      FIG. 5  is a diagram schematically showing a manner in which the coolant (air in this example) and a gas flow in the battery pack  100 . 
         [0049]    In the example shown in  FIG. 5 , an air intake duct  61  is connected to the pack case  50  at the lower side of the battery pack  100  in such a manner as to communicate with a supply path S 2  that is formed at the lower side of the battery stack  1 . Incidentally, when the battery pack  100  is mounted in a vehicle, the air intake duct  61  may be disposed so that an air intake opening of the air intake duct  61  faces the inside of a cabin of the vehicle. The air intake duct  61  may be provided with means (e.g., a blower) for adjusting the flow (flow velocity) of air to be supplied. Incidentally, a connecting portion between the air intake duct  61  and the supply path S 2  may be provided with a seal member (not shown). As for the supply path S 2 , as stated above, the other side end, that is, the opposite side end to the side end portion connected to the air intake duct  61 , may be sealed. In the example shown in  FIG. 5 , the supply path S 2  is sealed at the deep side in the X directions in the drawing. 
         [0050]    Furthermore, a smoke discharge duct  62  is connected to the pack case  50  at the upper side of the battery pack  100  in such a manner as to communicate with the smoke discharge path S 1  that is formed at the upper side of the battery stack  1 . The smoke discharge duct  62  may be provided with means (e.g., a blower) for adjusting the flow (flow velocity) of gas to be discharged. Incidentally, a connecting portion between the smoke discharge duct  62  and the smoke discharge path S 1  may be provided with a seal member (not shown). As for the smoke discharge path S 1 , as mentioned above, the other side end, that is, the opposite side end to the side end portion connected to the smoke discharge duct  62 , may be sealed. In the example shown in  FIG. 5 , the smoke discharge path S 1  is sealed at the deep side in the X directions in the drawing. However, the smoke discharge duct  62  may be connected to the deep side end portion of the smoke discharge path S 1  in the drawing, and the near-side end portion of the smoke discharge path S 1  in the drawing may be sealed. Furthermore, the smoke discharge path S 1  may also be connected at its both ends to the smoke discharge duct  62 . 
         [0051]    Incidentally, as shown in  FIG. 5 , the gas introduced into the smoke discharge path S 1  from the inside of each electric cell  10  via its valve  13  moves in an X direction (moves toward the near side in  FIG. 5 ), and is discharged from the smoke discharge duct  62  to the outside of the battery pack  100 . 
         [0052]      FIG. 6  is a diagram schematically showing the flowing manner of the coolant in the battery pack  100  (in the supply paths S 2 ) in a view taken in a Y direction. 
         [0053]    As shown in  FIG. 6 , the air introduced into the supply path S 2  via the air intake duct  61  moves in an X direction (moves toward the right side in  FIG. 6 ), and rises in the Z directions and is introduced into cooling paths S 3  (streams in the cooling paths S 3  will later be described with reference to  FIG. 7 ). The cooling paths S 3  are formed between each partition member  30  and an adjacent electric cell  10  as mentioned above. Incidentally, although  FIG. 6  illustrates as an example a virtual construction that has only four cooling paths S 3  for the sake of simple illustration, the cooling paths S 3  are formed between each partition member  30  and its adjacent electric cell  10 . 
         [0054]      FIG. 7  is a diagram schematically showing the flowing manner of the coolant in the battery pack  100  (in the cooling paths S 3 ) in a view taken in an X direction. 
         [0055]    As schematically shown by arrows P 1  and P 2  in  FIG. 7 , the air introduced through an intake opening  90  into the cooling path S 3  from the supply path S 2  is restricted in flowing direction by the ribs  32  so that the air flows in the T-shaped course as a whole, and is discharged from discharge openings  92  provided on both sides of the battery stack  1  in the Y directions. Concretely, part of the air introduced into the cooling path S 3  via the supply path S 2 , as schematically shown by the arrows P 1 , moves in a Z direction from the intake openings  90  (inlet openings) open to the supply path S 2  and then turns its direction to the Y direction (to the right side in  FIG. 7 ) and moves sideway (to the right side of the battery stack  1 ), and then is discharged out of the battery stack  1  through discharge openings  92  formed on the right side of the battery stack  1 . Furthermore, other part of the air introduced into the cooling path S 3  via the supply path S 2 , as schematically shown by arrows. P 2 , moves in the Z direction from the intake openings  90  open to the supply path S 2 , and then turns its direction to the Y direction (to the left side in  FIG. 7 ) and moves sideway (to the left side of the battery stack  1 ), and then is discharged out of the battery stack  1  through discharge openings  92  formed on the left side of the battery stack  1 . 
         [0056]    Incidentally, the air discharged out of the battery stack  1  may be discharged to the outside of the battery pack  100  through gaps or the like formed in the pack case  50 , or may also be discharged to the outside of the battery pack  100  through the use of an air discharge duct (not shown). In the former case, the air discharge duct can be discarded. 
         [0057]    Thus, according to the example shown in  FIG. 7 , since the cooling-purpose air can be caused to flow in the T-shaped course over the cooling areas of each electric cell  10  (the end surfaces thereof in the X directions), the cooling-purpose air can be discharged out of the battery stack  1  by using the discharge openings  92  formed on the side surface sides of the battery stack  1 , without using the smoke discharge path S 1  on the upper surface side of the battery stack  1 . 
         [0058]    Furthermore, since the cooling-purposed air can be caused to flow in the T-shaped courses over the cooling surfaces of each electric cell  10  (the end surfaces thereof in the X directions), the cooling efficiency for the electric cells  10  can be enhanced (which will later be described in detail with reference to  FIGS. 8A and 8B ). Incidentally, in order to enhance the cooling efficiency, a region R (a dotted region) where air flows is preferably set so as to cover the entire region of each of the end surfaces of each electric cell  10  in the X directions so that the cooling area is maximized. That is, it is desirable that the region R covers the existence region of each electric cell  10 . 
         [0059]    Furthermore, according to the example shown in  FIG. 7 , since the gas to be discharged forks into two streams (see the left and right discharge openings  92 ) as described above, the sectional area S 0  of the intake openings  90  is significantly smaller than the sectional area (the sum of S 11  and S 12 ) of the discharge openings  92 . For example, the sectional area S 0  of the intake openings  90  may be within the range of 1/3 to 2/3 of the sectional area of the discharge openings  92 . Therefore, the pressure of the cooling-purposed air can be adjusted (or the flow velocity thereof can be adjusted) at the intake openings  90 , which is relatively small in sectional area. 
         [0060]      FIG. 8A  and  FIG. 8B  schematically show cooling methods according to comparative examples, and, similar to  FIG. 7 , schematically show the flowing manners of the coolant on a partition plate.  FIG. 8A  shows a first comparative example in which the ribs extend in up-down directions so as to cause air to flow in a Z direction.  FIG. 8B  shows a second comparative example in which the ribs extend in the left-right directions so as to cause air to flow in the Y direction. 
         [0061]    In the first comparative example, as schematically shown by arrows P 3  in  FIG. 8A , the air introduced via an intake opening provided on a lower side of a battery stack flows in the Z direction, and is discharged out of the battery stack through a discharge opening provided on an upper side of the battery stack. Incidentally, in this example, the discharge openings communicate with a smoke discharge path. That is, the smoke discharge path also serves as an air discharge path. In this cooling method, there is a drawback that the cooling area is relatively small due to the limited sectional area of the intake opening (and the limited sectional area of the discharge opening). That is, the sectional area of the discharge opening on the upper surface side of the electric cell  10 , in particular, the lateral width of the discharge opening in the Y directions, is restricted because the discharge opening needs to be provided between the positive terminal.  11  and the negative terminal  12  of each electric cell  10 , and the sectional area of the intake opening is accordingly restricted as well. This results in a drawback that an effective cooling region R 1  is small in the Y directions as indicated by dotting in  FIG. 8A . 
         [0062]    It is to be noted herein that a thermal conductance Q usable as an index that represents the cooling efficiency of each electric cell  10  can be generally expressed as follows. 
         [0000]        Q=K·S ·√( V/L )
 
         [0000]    where K is a coefficient, S is a cooling area, V is the flow velocity of air, and L is a flow path length. Therefore, in the first comparative example, the cooling area S is smaller than in the example shown in  FIG. 7 , and therefore, the cooling efficiency is lower than in the foregoing example. 
         [0063]    In the second comparative example, as schematically shown by arrows P 4  in  FIG. 8B , the air introduced via intake openings provided on a left side of the battery stack flows in one of the Y directions, and is discharged out of the battery stack through discharge openings provided on a right side of the battery stack. In such a cooling method, a maximum cooling area R 2  substantially the same as in the example shown in  FIG. 7  can be secured, but the flow path length is longer and the cooling efficiency is lower than in the example shown in  FIG. 7  (see the foregoing mathematical expression). Concretely, in the second comparative example, the flow path length L1 corresponds to a width of the electric cell  10  in the Y directions whereas in the example shown in  FIG. 7  the flow path length L corresponds approximately to the sum of the length of the partition member  30  (or the electric cell  10 ) in the Z directions and ½ of the width of the partition member  30  in the Y directions) (see  FIG. 7 ). Therefore, since the sectional shape of the partition member  30  (or the electric cell  10 ) in a view taken in an X direction is a laterally long rectangle, the flow path length L1 in the second comparative example is longer than the flow path length L in the example shown in  FIG. 7 . 
         [0064]    The foregoing embodiments achieve, particularly, excellent effects as stated below. 
         [0065]    According to the embodiments, the lower side of the battery stack  1  is provided with the cooling-purposed air intake openings  90 , and the left and right sides of the battery stack  1  are provided with the discharge openings  92 , as described above. Therefore, the smoke discharge path S 1  can be formed isolatedly from the supply path S 2  and the cooling path S 3 . That is, the gas produced inside the electric cell  10  alone can be independently discharged to the outside of the pack case  50 . 
         [0066]    Furthermore, as described above, the lower side of the battery stack  1  is provided with the cooling-purposed air intake openings  90 , and the left and right sides of the battery stack  1  are provided with the discharge openings  92 . Therefore, the cooling-purposed air can be caused to flow in the T-shaped courses over the cooling areas (the end surfaces in the X directions) of each electric cell  10 , so that the cooling efficiency for the electric cells  10  can be enhanced. 
         [0067]    Furthermore, as described above, the pressure of the cooling-purposed air at the intake opening  90  side can be adjusted by making the sectional area SO of the intake openings  90  smaller than the sectional area (the sum of S 11  and S 12 ) of the discharge openings  92 . Furthermore, the air discharged from the discharge openings  92  provided on the two opposite sides of the battery stack  1  can be discharged to the outside of the pack case  50  without using any special air discharge duct, so that such air discharge ducts can be discarded. 
         [0068]    As described above, since the supply path S 2  is defined by the connecting portions  42  of the partition members  30  as described above, the number of component parts can be reduced in comparison with a construction in which the supply path S 2  is defined by members other than the partition members  30 . However, the connecting portions  42  of the partition members  30  may be discarded, and the supply path S 2  may be constructed by using members other than the partition members  30 . Furthermore, since the lower-side arresting members  46  are passed through the hollow portions that are formed when the connecting portions  42  of the partition members  30  made of resin are interconnected, it is no longer necessary to separately perform the insulation of the arresting members  46  made of metal. 
         [0069]    Furthermore, since the smoke discharge path Si is substantially defined by the connecting portions  42  of the partition members  30  as described above, the number of component parts can be reduced in comparison with a construction in which the smoke discharge path S 1  is substantially defined by members other than the partition members  30 . However, the connecting portions  42  of the partition members  30  may be discarded, and the smoke discharge path S 1  may be constructed by using members other than the partition members  30 . Furthermore, since the upper-side arresting members  46  are passed through the hollow portions that are formed when the connecting portions  42  of the partition members  30  made of resin are interconnected, it is no longer necessary to separately perform the insulation of the arresting members  46  made of metal. 
         [0070]    While the preferred embodiments of the invention have been described, the invention is not restricted by the foregoing embodiments, but various changes and replacements can be carried out on the foregoing embodiments without departing from the scope of the invention. 
         [0071]    For example, although in the foregoing embodiments, the cooling-purposed air discharge openings  92  are provided on both sides of the battery stack  1  in the Y directions, the cooling-purposed air discharge opening  92  may be provided only on one of the sides of the battery stack  1  in the Y directions as in a partition member  300  according to another embodiment shown in  FIG. 9  (on the right side in the example shown in  FIG. 9 ). In this construction, as schematically shown by arrows P 5  in  FIG. 9 , the air introduced via an intake opening  90  provided on the lower side of the battery stack flows in one of the Z directions, and then turns its direction to one of the Y directions, and is discharged out of the battery stack through a discharge opening  92  provided on the right side of the battery stack. This construction also makes it possible to form a smoke discharge path isolatedly from the supply path and the cooling path S 3  although the flow path length is long. 
         [0072]    Furthermore, although in the foregoing embodiment, a plurality of electric cells  10 , each being one battery unit, are partitioned from each other by the partition members  30 , it is also permissible to provide a plurality of electric cells  10  as a module, and to partition a plurality of modules from each other, each being one battery unit, by partition members  30 . 
         [0073]    Furthermore, although in the foregoing embodiments, the plurality of electric cells  10  are partitioned from each other by partition members  30 , the partition members  30  may be omitted. In this case, the electric cells  10  may be individually insulated (e.g., the end surfaces of each electric cell in the X directions are each provided with an insulation layer). Furthermore, in the case where the partition members  30  are omitted, the construction that corresponds to the ribs  32  of each partition member  30  may be formed on an end surface of each electric cell  10  in the X directions. 
         [0074]    Furthermore, although in the foregoing embodiments, the ribs  32  are provided on each partition member  30 , it is also permissible to, instead of or in addition to the ribs  32 , provide similar ribs on an end surface of each electric cell  10  in the X directions. 
         [0075]    Furthermore, although in the foregoing embodiments, the coolant is used to cool the electric cells  10 , the coolant may also be used to warm up the electric cells  10  according to need.