Abstract:
A battery device is provided with cooling bodies for contacting the outer surfaces of a plurality of battery cells arranged inside a battery case, and spacers provided adjacent to the cooling bodies. The cooling bodies absorb or are impregnated with a cooling fluid inside the battery case. Cooling medium vapor flow channels in which cooling medium vapor circulates are formed on the surfaces of the spacers facing the cooling bodies, the cooling medium vapor being generated by the evaporation of the cooling fluid of the cooling bodies.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a battery apparatus (battery device) for cooling a plurality of battery cells mutually juxtaposed in a battery case, utilizing the evaporation latent heat of insulating cooling liquid. 
       BACKGROUND ART 
       [0002]    Electric vehicles such as an electric automobile, a hybrid automobile equipped with an internal combustion engine, and a fuel cell automobile equipped with a fuel cell are equipped with a battery apparatus for supplying electrical energy to an electric motor for driving the vehicle. The battery apparatus of this type includes a plurality of battery cells that are connected in series electrically. These battery cells emit heat produced in chemical reactions at the time of charging and discharging of the battery cells. It is important to suppress the increase in the temperature of the battery cells, for maintaining the operation characteristics of the battery apparatus, and avoiding the decrease in the product life of the battery apparatus. 
         [0003]    In such a battery apparatus, for example, according to the technical concept disclosed in the pamphlet of International Publication No. WO2011/105256, a plurality of cooling elements (supports in the form of sponge, etc.) for absorbing insulating cooling liquid stored in a battery case with a predetermined space of the battery case unfilled with the cooling liquid, are brought into contact with each of the battery cells. The evaporation latent heat of the cooling liquid of the cooling element is utilized to cool the battery cells. In the battery apparatus, since the space inside the battery case is not fully filled with the cooling liquid, it is possible to achieve weight reduction of the battery apparatus. In the battery apparatus, the cooling elements are filled between the adjacent battery cells, and between the battery cell and the battery case. 
       SUMMARY OF INVENTION 
       [0004]    In the conventional technique as described in International Publication No. WO2011/105256, since the cooling elements are filled between the adjacent battery cells, and between the battery cells and the battery case, it may not be possible to smoothly guide the gas (coolant steam) produced by evaporation of the cooling liquid of the cooling elements to the outside of the cooling elements. That is, the coolant steam may be retained inside the cooling elements. Under the circumstances, it becomes impossible for the cooling elements to absorb the cooling liquid retained in the battery case efficiently. Since the quantity of the cooling liquid contained in the cooling elements is reduced, the cooling efficiency may be lowered undesirably. 
         [0005]    The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a battery apparatus in which it is possible to achieve weight reduction, and suppress the decrease in the cooling efficiency of a battery cell by the evaporation latent heat of cooling liquid of a cooling element. 
         [0006]    In order to achieve solve the above problems, a battery apparatus according to the present invention cools a plurality of battery cells mutually juxtaposed in a battery case, utilizing evaporation latent heat of insulating cooling liquid, and includes a cooling element provided between the plurality of battery cells, the cooling element being configured to contact an outer surface of the battery cell, and configured to absorb or be impregnated with cooling liquid in the battery case; and a spacer provided adjacent to the cooling element in a direction in which the plurality of battery cells are arranged, wherein a coolant steam flow groove is famed on a surface of the spacer facing the cooling element, as a passage of coolant steam produced by evaporation of the cooling liquid of the cooling element. 
         [0007]    In the structure, since it is possible to guide the cooling liquid in the battery case to outer surfaces of battery cells by the cooling element, even if the space inside the battery case is not filled with the cooling liquid, it is possible to cool the battery cells by the suitable quantity of cooling liquid. Therefore, it is possible to achieve weight reduction of the battery apparatus. Further, since the coolant steam produced by evaporating the cooling liquid of the cooling element is guided from the inside of the cooling element to the coolant steam flow groove of the spacer, it is possible to suppress stagnation of the coolant steam inside the cooling element. In this manner, since the cooling element can absorb or can be impregnated with the cooling liquid stored in the battery case efficiently, it is possible to suppress decrease in the cooling efficiency of the battery cell by the evaporation latent heat of the cooling liquid of the cooling element. 
         [0008]    The battery apparatus may further include a heat exchanger configured to cool the coolant steam. 
         [0009]    Further, in the structure, since it is possible to condense the coolant steam back to the cooling liquid, it is possible to suppress the shortage of the cooling liquid in the battery case. 
         [0010]    In the above battery apparatus, the spacer may be configured to contact the cooling element, and the coolant steam flow groove may be famed by making a recess on at least part of the surface of the spacer which contacts the cooling element. 
         [0011]    In the structure, it is possible to hold the cooling element between the battery cell and the spacer, and form the coolant steam flow grooves easily. 
         [0012]    In the above battery apparatus, a pair of the cooling elements which contact outer surfaces of each of the battery cells may be provided between the adjacent battery cells, the spacer which contacts the pair of cooling elements may be formed between the pair of cooling elements, and the coolant steam flow grooves may be famed on both surfaces of the spacer which contact the cooling elements. 
         [0013]    In the structure, since it is sufficient to provide one spacer between a pair of cooling elements, it is possible to achieve size reduction of the battery apparatus. 
         [0014]    In the above battery apparatus, the cooling liquid may be produced by mixing a plurality of kinds of liquid coolants having different boiling points. 
         [0015]    In the structure, the boiling point can be set to the desired temperature. Therefore, it is possible to regulate the temperature of the battery cells cooled by the evaporation latent heat of the cooling liquid to become closer to the target operating temperature. 
         [0016]    In the above battery apparatus, the spacer may be an open cell foam. 
         [0017]    In the structure, it is possible to obtain the spacer having the coolant steam flow grooves easily. 
         [0018]    The above battery apparatus may further includes a liquid holder member provided in the battery case, and configured to be impregnated with the cooling liquid, and the cooling element may contact the liquid holder member in order to absorb the cooling liquid which has been impregnated into the liquid holder member. 
         [0019]    In the structure, for example, even in the case where the battery apparatus is mounted in an electric vehicle, since the liquid surface position of the cooling liquid in the battery case does not change due to the road surface condition or vibrations, the cooling liquid impregnated into the liquid holder member can be absorbed into the cooling element reliably. 
         [0020]    In the present invention, the cooling liquid stored in the battery case can be guided to the outer surfaces of the battery cell by the cooling element. Therefore, it is possible to achieve weight reduction of the battery apparatus. Further, the coolant steam produced by evaporating the cooling liquid of the cooling element is guided to the coolant steam flow groove of the spacer, it is possible to suppress decrease in the cooling efficiency of the battery cell by the evaporation latent heat of the cooling liquid of the cooling element. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  is a vertical cross sectional view schematically showing a battery apparatus according to a first embodiment of the present invention; 
           [0022]      FIG. 2  is a partial enlarged cross sectional view of a battery body shown in  FIG. 1 ; 
           [0023]      FIG. 3  is a graph showing the change in the temperature of a battery cell; 
           [0024]      FIG. 4  is a vertical cross sectional view schematically showing a battery apparatus according to a second embodiment of the present invention; 
           [0025]      FIG. 5  is a vertical cross sectional view schematically showing a battery apparatus according to a third embodiment of the present invention; 
           [0026]      FIG. 6A  is a partial cross sectional view showing a spacer according to a first modified embodiment; and 
           [0027]      FIG. 6B  is a partial cross sectional view showing a spacer according to a second modified embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    Hereinafter, preferred embodiments of a battery apparatus according to the present invention will be described below with reference to the accompanying drawings. 
       First Embodiment 
       [0029]    A battery apparatus  10 A according to an embodiment of the present invention is mounted in an electric vehicle such as an electric automobile, a hybrid automobile equipped with an internal combustion engine, and a fuel cell automobile equipped with a fuel cell. That is, the battery apparatus  10 A is capable of charging electrical energy supplied from a power feeding apparatus, and capable of supplying electrical energy to an electric motor for driving the vehicle. However, the battery apparatus  10 A is not limited to an example where the battery apparatus  10 A is mounted on such an electric vehicle. The battery apparatus  10 A can be utilized in combination with any apparatuses. 
         [0030]    As shown in  FIG. 1 , the battery apparatus  10 A includes a battery body  12  and a battery heat exchanger  14  provided for the battery body  12 . The battery body  12  includes a battery case  16  having a rectangular parallelepiped shape, and a plurality battery cells  18  provided in parallel within the battery case  16 , insulating cooling liquid  20  stored in the battery case  16 , a plurality of cooling elements (wick)  22  provided for the battery cells  18  to absorb the cooling liquid  20  or to be impregnated with the cooling liquid  20 , and a plurality of spacers  24 ,  26  provided adjacent to the cooling elements  22 . 
         [0031]    The battery cell  18  has known structure where a battery cell body and electrolytic solution are placed in a laminator case. The battery cell body is famed by connecting a plurality of unit cells that are stacked together, electrically in series. Each of the unit cells includes a positive electrode, a separator, and a negative electrode. A plurality of the battery cells  18  are connected electrically and directly. In the embodiment, the battery cell  18  has a rectangular shape in a front view. Six battery cells are arranged in a horizontal direction (indicated by an arrow X) in the state where the longitudinal directions of the battery cells  18  are oriented in a vertical direction (indicated by an arrow Z). The number of the battery cells  18  can be determined arbitrarily. 
         [0032]    The cooling elements  22  are provided on the outer surfaces (outer surfaces oriented in the thickness direction of the battery cells  18 ) on both sides of each of the battery cells  18 . Further, the spacer  24  is provided in each space between the adjacent cooling elements  22 , and the spacers  26  are provided outside the cooling elements  22  at the outermost positions. That is, the battery cells  18 , the cooling elements  22 , and the spacers  24 ,  26  are arranged in the horizontal direction. Further, the battery cells  18 , the cooling elements  22 , and the spacers  24 ,  26  are fixed to the battery case  16  in the state where the pair of spacers  26  at the outermost positions are pressed toward each other by a holder mechanism (not shown). 
         [0033]    Stated otherwise, a pair of the cooling elements  22  and one spacer  24  are provided in each space between the adjacent battery cells  18 . The pair of cooling elements  22  contact the outer surfaces of the battery cells  18 , and the spacer  24  is positioned between the pair of cooling elements  22 , and contacts these cooling elements  22 . The battery cells  18  are cooled utilizing the evaporation latent heat of the cooling liquid  20  which was absorbed by, or impregnated into the cooling elements  22 . 
         [0034]    The cooling liquid  20  is stored in the battery case  16  in a manner that the each of the battery cells  18  is impregnated with the cooling liquid  20 . That is, some space which is not filled with the cooling liquid  20  remains present in the battery case  16 . In the structure, it is possible to achieve weight reduction of the battery apparatus  10 A. It should be noted that the quantity of the cooling liquid  20  stored in the battery case  16  can be determined arbitrarily. 
         [0035]    As the cooling liquid  20 , liquid coolant having the boiling point which is substantially equal to the target operating temperature of the battery cells  18  is used. For example, hydrofluoroether such as Novec (registered trademark) 7000 having the boiling point of 34° C. under 1 atm or hydrofluoroketone such as Novec (registered trademark) 649 having the boiling point of 49° C. under 1 atm can be used suitably. 
         [0036]    Further, the cooling liquid  20  may be produced by mixing a plurality of kinds of liquid coolants having different boiling points. In this case, the boiling point of the cooling liquid  20  can be set to the desired temperature. Therefore, it is possible to regulate the temperature of the battery cells  18  cooled by the evaporation latent heat of the cooling liquid  20  to become closer to the target operating temperature. Further, the boiling point of the cooling liquid  20  can be set by changing the molecular weight of the liquid coolant. 
         [0037]    The cooling element  22  has a shape corresponding to the shape of the battery cell  18 . For example, the cooling element  22  has a substantially rectangular shape in a front view. The spacers  24 ,  26  have the same shape. In the state where the cooling elements  22  are partially impregnated with the cooling liquid  20  (lower parts of the cooling elements  22  are partially impregnated with the cooling liquid  20 ), the cooling elements  22  contacts substantially the entire outer surfaces on both sides of the battery cell  18 . In this manner, the cooling elements  22  can absorb or can be impregnated with the cooling liquid  20  stored in the battery case  16 . Consequently, it becomes possible to uniformly impregnate (supply) the cooling liquid  20  into substantially the entire outer surfaces on both sides of each of the cooling elements  22 . 
         [0038]    As the cooling element  22 , for example, microfiber cloth is used. In this case, the cooling liquid  20  can be sucked up efficiently by the capillary pressure. However, the cooling element  22  is not limited to the microfiber cloth. The cooling element  22  may be made of, e.g., porous material. The thickness of the cooling element  22  is determined to have a sufficient size to guide the gas produced when the cooling liquid  20  of the cooling element  22  is evaporated at the time of cooing the battery cell  18  (hereinafter also referred to as the coolant steam), to the surfaces which contact the spacers  24 ,  26 . 
         [0039]    For example, the spacer  24  is made of metal, resin, etc. The spacer  24  has the compression strength sufficient to maintain the distance between the adjacent battery cells  18  to have a predetermined value when the pair of the spacers  26  at the outermost positions are pressed toward each other. 
         [0040]    As shown in  FIG. 2 , the spacer  24  has a plurality of coolant steam flow grooves  28  as passages of coolant steam, on its surface which contact the cooling element  22 . In the structure, the coolant steam from the inside of the cooling element  22  is guided (supplied) rapidly (smoothly) into the coolant steam flow grooves  28 . 
         [0041]    In the embodiment of the present invention, each of the coolant steam flow grooves  28  has a substantially V-shape in lateral cross section. The coolant steam flow grooves  28  extend along the spacer  24  in the longitudinal direction (vertical direction indicated by an arrow Z) over the entire length. Therefore, the coolant steam supplied into the coolant steam flow grooves  28  is discharged above the spacer  24 . The coolant steam flow grooves  28  have a sufficient flow cross sectional area for the coolant steam to move smoothly. 
         [0042]    Further, the coolant steam flow grooves  28  are arranged in the spacer  24  in parallel in the width direction of the spacer  24  (lateral direction of the spacer  24  indicated by the arrow Y in  FIG. 2 ) such that the coolant steam flow grooves  28  face substantially the entire surface of the cooling element  22 . That is, peaks  32  of partition walls  30  dividing the coolant steam flow grooves  28  contact the cooling element  22 . In the structure, the cooling element  22  is pressed by the spacer  24  such that the cooling element  22  uniformly contacts the battery cell  18 . The width L at the peaks  32  of the partition walls  30  is set to have a sufficient size not to cause floating of the portion of the cooling element  22  impregnated with the cooling liquid  20  due to the buoyant force. 
         [0043]    As described above, in the embodiment of the present invention, the coolant steam flow grooves  28  are formed by making recesses on at least part of the surface of the spacer  24  which contacts the cooling element  22 . Therefore, the cooling element  22  can be held between the battery cell  18  and the spacer  24 , and it is possible to form the coolant steam flow grooves  28  easily. As shown in  FIG. 1 , the pair of spacers  26  have the same structure as the above described spacer  24  except that a plurality of coolant steam flow grooves  28  are formed only on one surface which contacts the cooling element  22 . Therefore, the detailed description about the spacers  26  is omitted. 
         [0044]    The heat exchanger  14  includes an inlet channel  34  through which the coolant steam in the battery case  16  is guided, a fan  36  provided for the inlet channel  34 , a heat exchanger body  38  for cooling the coolant steam guided from the inlet channel  34 , and an outlet channel  40  for guiding the cooling liquid  20  produced by condensing the coolant steam by the heat exchanger body  38  into the battery case  16 . 
         [0045]    In the embodiment of the present invention, the inlet channel  34  and the outlet channel  40  are connected to the side wall of the battery case  16 , and communicated with the inside of the battery case  16 . In the structure, the cooling liquid  20  guided from the outlet channel  40  flows along the side wall of the battery case  16 , and the cooling liquid  20  can be stored in the battery case  16 . However, positions of connecting the inlet channel  34  and the outlet channel  40  to the battery case  16  can be determined arbitrarily. For example, the inlet channel  34  and the outlet channel  40  may be connected to an upper wall of the battery case  16 . 
         [0046]    The fan  36  forcibly guides the coolant steam in the battery case  16  into the heat exchanger body  38  through the inlet channel  34 , and forcibly guides the cooling liquid  20  produced in the heat exchanger body  38  into the battery case  16  through the outlet channel  40 . The heat exchanger body  38  may have any structure as long as it can cool, and condense the coolant steam. That is, it is a matter of course that a radiator mounted in the electric vehicle may be used as the heat exchanger body  38 . 
         [0047]    The battery apparatus  10 A according to the present invention basically have the above structure. Next, effects and advantages of the battery apparatus  10 A will be described. 
         [0048]    In the battery apparatus  10 A of the embodiment of the present invention, in the initial state, the cooling liquid  20  stored in the battery case  16  is impregnated into each of the cooling elements  22  made of, e.g., microfiber cloth, and absorbed into the entire cooling elements  22  by the capillary pressure. That is, the cooling liquid  20  contacts substantially the entire outer surfaces on both sides of each of the battery cells  18  through the cooling elements  22 . 
         [0049]    When the battery apparatus  10 A is operated (discharged or charged), heat is emitted from each of the battery cells  18 . At this time, the cooling liquid  20  of the cooling element  22  absorbs the heat from the battery cells  18 . Therefore, the cooling liquid  20  is evaporated, and the coolant steam is produced. Stated otherwise, the battery cells  18  are cooled by the evaporation latent heat of the cooling liquid  20  of the cooling element  22 . Therefore, the operating temperature of the battery cells  18  is cooled up to a temperature close to the boiling point of the cooling liquid  20 . 
         [0050]    The coolant steam produced in the cooling element  22  is guided smoothly above the spacers  24 ,  26  through the coolant steam flow grooves  28  of the spacers  24 ,  26  adjacent to the cooling elements  22 . That is, stagnation of the coolant steam inside the cooling elements  22  is suppressed. Therefore, since the cooling elements  22  efficiently absorb or are impregnated with the cooling liquid  20  stored in the battery case  16 , predetermined quantity of the cooling liquid  20  is continuously supplied to the entire outer surfaces on both sides of the battery cell  18 . Therefore, the temperature of the battery cells  18  is kept at a substantially constant temperature. 
         [0051]    After the coolant steam is guided to the upper space in the battery case  16  through the coolant steam flow grooves  28  of the spacers  24 ,  26 , the coolant steam is guided to the heat exchanger body  38  through the inlet channel  34  under operation of the fan  36 , and cooled in the heat exchanger body  38 . Further, the cooling liquid  20  produced by condensation of the coolant steam by the heat exchanger body  38  flows through the outlet channel  40 , and flows along the side wall of the battery case  16 . Then, the cooling liquid  20  is stored in the battery case  16 . That is, even during operation of the battery apparatus  10 A, the shortage of the cooling liquid  20  stored in the battery case  16  is suppressed. Accordingly, it is possible to continuously cool the battery cell  18  by the predetermined quantity of cooling liquid  20 . 
         [0052]    In the embodiment of the present invention, the cooling liquid  20  stored in the battery case  16  can be guided to the outer surfaces of the battery cells  18  by the cooling elements  22 . Therefore, even if the space inside the battery case  16  is not fully filled with the cooling liquid  20 , it is possible to cool the battery cells  18  using the suitable quantity of cooling liquid  20 . Therefore, it is possible to achieve weight reduction of the battery apparatus  10 A. 
         [0053]    Further, since the coolant steam (gas) produced by evaporating the cooling liquid  20  of the cooling elements  22  can be guided from the inside of the cooling elements  22  to the coolant steam flow grooves  28  of the spacers  24 ,  26 , it is possible to suppress stagnation of the coolant steam inside the cooling elements  22 . In this manner, since the cooling elements  22  can absorb or can be impregnated with the cooling liquid  20  stored in the battery case  16  efficiently, it is possible to suppress decrease in the cooling efficiency of the battery cells  18  by the evaporation latent heat of the cooling liquid  20  of the cooling elements  22 . 
         [0054]    Further, since it is possible to condense the coolant steam by the heat exchanger  14  back to the cooling liquid  20 , it is possible to suppress the shortage of the cooling liquid  20  in the battery case  16 . 
         [0055]    Further, since the coolant steam flow grooves  28  is formed by making recesses on at least part of the surfaces of the spacers  24 ,  26  which contact the cooling elements  22 , it is possible to hold the cooling elements  22  between the battery cells  18  and the spacers  24 ,  26 , and form the coolant steam flow grooves  28  easily. 
         [0056]    Moreover, the pair of cooling elements  22  are provided between the adjacent battery cells  18  in a manner that the cooling elements  22  contact the outer surfaces of each of the battery cells  18 , and one spacer  24  is provided between the pair of cooling elements  22  in a manner that the spacer  24  contacts the cooling elements  22 , to form the coolant steam flow grooves  28  on both surfaces of the spacer  24  which contacts the cooling elements  22 . Therefore, it is possible to achieve size reduction of the battery apparatus  10 A. 
         [0057]    Next, effects and advantages of the battery apparatus  10 A according to the embodiment of the present invention will be descried further in detail with reference to a graph of  FIG. 3 .  FIG. 3  is a graph showing the change in the temperature of the battery cell  18  when the battery apparatus  10 A is operated. In  FIG. 3 , a solid bold line A indicates the change in the temperature of the battery cell  18  of the battery apparatus  10 A according to the embodiment of the present invention, and a solid narrow line B indicates the change in the temperature of a battery cell according to a comparative example. The temperature Tb indicates the boiling point of the cooling liquid  20 . 
         [0058]    In the battery apparatus according to the comparative example, the spacers  24 ,  26  of the above described battery apparatus  10 A are omitted. The cooling element  22  is made of porous material, and all of the battery cells  18  are completely impregnated with the cooling liquid (the space inside the battery case is filled with the cooling liquid). The structure of the battery apparatus according to the comparative example is the same as the structure of the battery apparatus  10 A in other respects. 
         [0059]    As can be understood from  FIG. 3 , the temperature of the battery cell  18  of the battery apparatus  10 A according to the embodiment of the present invention is maintained at a temperature close to the boiling point of the cooling liquid  20  during operation of the battery apparatus  10 A, as in the case of the battery apparatus according to the comparative example. That is, the cooling element  22  is made of microfiber cloth having relatively high capillary pressure, and the spacers  24 ,  26  having the coolant steam flow grooves  28  are provided. It can be seen that, even if the quantity of the cooling liquid  20  is small, it is possible obtain the cooling effects equal to the battery cell of the battery apparatus according to the comparative example. 
         [0060]    In the battery apparatus  10 A, the coolant steam flow groove  28  may extend in the entire width direction of the spacers  24 ,  26  (indicated by the arrow Y), and a plurality of the coolant steam flow grooves  28  may be arranged in the longitudinal direction of the spacers  24 ,  26  (indicated by the arrow z). Also in this case, the above described effects and advantages are obtained in the battery apparatus  10 A. Also in a battery apparatus  10 B according to a second embodiment described later, the same effects and advantages are obtained. 
       Second Embodiment 
       [0061]    Next, the battery apparatus  10 B according to the second embodiment of the present invention will be described with reference to  FIG. 4 . In the battery apparatus  10 B according to the second embodiment, the constituent components having the same or similar functions and advantages as or to that of the battery apparatus  10 A according to the first embodiment are labeled with the same reference numerals, and detailed description is omitted. Also in a battery apparatus  10 C according to a third embodiment, the constituent components having the same or similar functions and advantages as or to that of the battery apparatus  10 A according to the first embodiment are labeled with the same reference numerals, and detailed description is omitted. 
         [0062]    As shown in  FIG. 4 , the battery apparatus  10 B according to the embodiment of the present invention further includes a liquid holder member  42  impregnated with cooling liquid  20 . For example, the liquid holder member  42  may be an open cell foam (continuous foaming body) made of porous material. Each of the cooling elements  22  contacts the liquid holder member  42  at its lower end surface. Therefore, the cooling liquid  20  in the liquid holder member  42  is absorbed into each of the cooling elements  22  by the capillary pressure. 
         [0063]    In the embodiment of the present invention, even if the battery apparatus  10 B is mounted in an electric vehicle, since the liquid surface of the cooling liquid  20  in the battery case  16  does not change due to the road surface condition or vibrations, the cooling liquid  20  impregnated into the liquid holder member  42  can be absorbed into the cooling element  22  reliably. 
       Third Embodiment 
       [0064]    Next, the battery apparatus  10 C according to the third embodiment of the present invention will be described with reference to  FIG. 5 . As shown in  FIG. 5 , the battery apparatus  10 C according to the embodiment of the present invention includes a battery body  44  and a heat exchanger  46 . The battery body  44  includes a rectangular parallelepiped battery case  48 . In the battery case  48 , six battery cells  18  are arranged in a vertical direction indicated by an arrow Z in a state where the longitudinal direction of the battery cells  18  is oriented in a horizontal direction (the direction perpendicular to the paper surface in  FIG. 5 ). The number of the battery cells  18  can be determined arbitrarily. 
         [0065]    Further, the cooling elements  22  are provided on the outer surfaces on both sides of the battery cells  18 . A spacer  24  is provided in each space between the adjacent cooling elements  22 , and spacers  26  are provided outside the cooling elements  22  at the outermost positions. That is, the battery cells  18 , the cooling elements  22 , and the spacers  24 ,  26  are arranged in the vertical direction. 
         [0066]    Further, the battery body  44  includes a supply part  50  for supplying the cooling liquid  20  stored in the battery case  48  to each of the cooling elements  22 . In the state where the supply part  50  contacts each of the cooling elements  22 , the supply part  50  is partially impregnated with the cooling liquid  20  stored in the battery case  48 . The supply part  50  is made of microfiber cloth or porous material, and can absorb the cooling liquid  20 , or can be impregnated with the cooling liquid  20 . The supply part  50  is formed integrally with each of the cooling elements  22 . Alternatively, the supply part  50  may be provided separately from each of the cooling elements  22 . 
         [0067]    In the embodiment of the present invention, the supply part  50  is provided at each of both ends of the cooling elements  22  in the width direction (indicated by an arrow X) over the entire length of the cooling elements  22 . In the structure, it is possible to supply the cooling liquid  20  stored in the battery case  48  to each of the cooling elements  22  efficiently. 
         [0068]    Coolant steam flow grooves  28  formed in the spacers  24 ,  26  extend in the longitudinal direction of the spacers  24 , over the entire length of the spacers  24 . Therefore, the coolant steam supplied into the coolant steam flow grooves  28  does not interfere with the supply part  50 , and the coolant steam is discharged to the outside of the spacers  24 ,  26 . Further, the coolant steam flow grooves  28  are arranged in parallel in the width direction of the spacers  24 ,  26  in the direction indicated by an arrow X such that the coolant steam flow grooves  28  face at least substantially the entire surfaces of the cooling elements  22 . 
         [0069]    The heat exchanger  46  includes a support part  52 , a plurality of cooling fins  54 , and a plurality of heat radiation fins  56 . The support part  52  closes an upper opening of the battery case  48 . The cooling fins  54  extend from the support part  52  downward inside the battery case  48 . The radiation fins  56  extend from the support part  52  upward outside the battery case  48 . For example, the heat exchanger  46  is made of metal material, etc. 
         [0070]    The radiation fins  56  may be cooled forcibly by the wind generated by a fan, etc. (not shown). In this case, it is possible to efficiently release the heat transmitted to the cooling fins  54  by heat exchange with the coolant steam to the outside through the support part  52  and the heat radiation fins  56 . 
         [0071]    In the battery apparatus  10 C according to the embodiment of the present invention, in the initial state, the cooling liquid  20  stored in the battery case  48  is absorbed into each of the cooling elements  22  through the supply part  50 , and impregnated into the entire cooling elements  22 . That is, the cooling liquid  20  contacts substantially the entire outer surfaces on both sides of each of the battery cells  18  through the cooling elements  22 . 
         [0072]    Further, when heat is emitted from each of the battery cells  18 , the battery cells  18  are cooled by the evaporation latent heat of the cooling liquid  20  in the cooling elements  22 . The cooling steam produced at this time is discharged to the outside of the spacer  24  through the coolant steam flow grooves  28 , and contacts the cooling fins  54  of the heat exchanger  46 , and the coolant steam is cooled by the cooling fins  54 . Further, the cooling liquid  20  produced by condensation of the coolant steam at the cooling fins  54  is dropped downward, and eventually, stored in the battery case  48 . In the battery apparatus  10 C according to the embodiment of the present invention, the same effects and advantages as in the case of the battery apparatus  10 A according to the above described first embodiment are obtained. 
         [0073]    The battery apparatus  10 C may include the above described liquid holder member  42  shown in  FIG. 4 . In this case, the battery apparatus  10 C has the same effects and advantages as in the case of the battery apparatus  10 B according to the second embodiment. 
         [0074]    The battery apparatuses  10 A to  10 C are not limited to the above described structure. The battery apparatuses  10 A to  10 C may include a spacer  60  according to a first modified embodiment shown in  FIG. 6A  instead of the spacer  24 . This spacer  60  is formed by corrugating a thin resin plate. In the structure, it is possible to form the coolant steam flow grooves  62  on both surfaces of the spacer  60  easily. 
         [0075]    Further, the battery apparatuses  10 A to  10 C may have a spacer  64  according to a second modified embodiment shown in 
         [0076]      FIG. 6B  instead of the spacers  24 ,  26 . For example, the spacer  64  is an open cell foam made of metal such as aluminum. In the structure, it is possible to increase the rigidity of the spacer  64  easily, and form the coolant steam flow grooves  66  in the spacer  64 .