JP7111857B2 - battery pack - Google Patents

Description

The present invention relates to battery packs.

In recent years, the demand for in-vehicle secondary batteries has increased against the backdrop of environmental regulations. Among them, lithium-ion secondary batteries are generally regarded as promising because they have a higher discharge potential than lead-acid batteries and nickel-metal hydride batteries, and can be made smaller and have higher energy densities. For full-scale application, lithium-ion secondary batteries are required to have higher energy density, higher power density, longer life, and the like. In order to increase the output of the battery, it is effective not only to increase the potential but also to input/output a large current from the battery. However, when a large current is input/output from the battery, heat is generated inside the battery due to the internal resistance of the battery. If the generated heat cannot be sufficiently removed from the battery, the battery temperature will rise. Battery characteristics such as battery capacity and internal resistance of lithium ion batteries tend to deteriorate depending on the battery temperature. Therefore, it is necessary to develop a technique for improving the heat dissipation performance of the battery.

When a plurality of lithium ion cells (hereinafter referred to as cells) are combined and used as a battery group (for example, when used as a battery module or battery pack), the temperature difference between the cells in the battery group should be reduced. It is desired to This is because when the temperature difference between the cells is large, the difference in deterioration tends to occur between the cells. Since the characteristics of a battery group tend to be rate-determined by the characteristics of the most deteriorated cell among the single cells included in the battery group, it is necessary to design a battery group that avoids a structure in which a specific battery deteriorates.

Therefore, in a battery group formed by combining a plurality of cells, a technique for reducing the temperature difference between the cells has been developed. Specifically, in Patent Document 1, a battery case containing cells is formed in a rectangular parallelepiped shape having a narrow short side surface and a wide long side surface. A storage battery is described in which a plurality of single cells are connected to form an assembled battery with a required power capacity.

On the other hand, when a large current is input/output from the battery, it is necessary to increase the cross-sectional area of the cable connected to the battery. Metals such as copper are used as members for cables, and since metals generally have high thermal conductivity, they have high heat radiation performance.

JP-A-2000-164186

In the technique described in Patent Document 1, a plurality of ribs are formed on the long side surface of the container of each unit cell. The cells are cooled by forcibly circulating air or the like between the ribs. In such a configuration, when the cooling efficiency decreases (for example, when the flow rate of forced air is small, or when the input/output current is large and the amount of heat generated by the cells is large), the battery temperature in the configured battery group A distribution occurs, and the battery temperature of the cells arranged near the center of the long side of the battery group is particularly high, and there is a possibility that the deterioration progresses. An object of the present invention is to provide a battery pack in which the temperature difference between battery groups is small.

The battery pack according to the present invention includes a first battery group in which a plurality of storage batteries having a battery can side surface and a battery can bottom surface connected to the battery can side surface are stacked with the battery can side surfaces facing each other, and the battery can side surface and the battery can. A second battery group in which a plurality of storage batteries having a battery can bottom surface connected to a side surface are stacked with the battery can sides facing each other, and a housing for housing the first battery group and the second battery group The first battery group and the second battery group are characterized in that their facing surfaces are directly or indirectly thermally connected to each other.

ADVANTAGE OF THE INVENTION According to this invention, the battery pack which reduced the temperature difference between battery groups can be provided.

FIG. 2 is a diagram for explaining an example of a specific configuration of a battery group in Example 1; FIG. 5 is a diagram for explaining an example of a specific configuration of a battery group in Example 2; FIG. 11 is a diagram for explaining an example of a specific configuration of a battery group in Example 5; FIG. 11 is a diagram for explaining an example of a specific configuration of a battery group in Example 6; FIG. 11 is a diagram for explaining an example of a specific configuration of a battery group in Example 7; 4 is a diagram for explaining an example of a specific configuration of a battery group in Comparative Example 1; FIG. FIG. 10 is a diagram for explaining an example of a specific configuration of a battery group in Comparative Example 2; FIG. 4 is a temperature rise ratio chart showing the temperature rise from the ambient temperature of each unit cell in the configurations of Examples 1 and 2 and the conventional configuration as a ratio from the lowest temperature in the battery group. FIG. 10 is a temperature rise ratio chart showing the temperature rise from the environmental temperature of each unit cell in the configurations of Examples 3 and 4 and the conventional configuration as a ratio from the lowest temperature in the battery group. FIG. 10 is a temperature rise ratio chart showing the temperature rise from the ambient temperature of each unit cell in the configurations of Examples 5 and 6 and the conventional configuration as a ratio from the lowest temperature in the battery group. FIG. 10 is a temperature rise ratio chart showing the temperature rise from the ambient temperature of each single cell in the structure of Example 7 and the conventional structure as a ratio from the lowest temperature in the battery group. The figure which looked at the battery pack of FIG. 2 from the upper surface. The first modification of FIG. 12 . A second modification of FIG. 12 . 1 is a perspective view of a secondary battery of the present invention; FIG.

A mode for carrying out the present invention will be described. However, the present embodiment is not limited to the following contents in any way, and can be arbitrarily modified within the scope of the present invention.

This embodiment will be described in detail. Although a lithium ion secondary battery is used as the secondary battery in this embodiment, this configuration can also be applied to other types of storage batteries. Moreover, the effect can be obtained regardless of the constituent members of the lithium ion secondary battery. That is, in the present invention, an electrode made of an Al collector foil and a positive electrode material having a layered structure is used as a positive electrode, and an electrode made of a Cu collector foil and a carbon material is used as a negative electrode, but other configurations are also possible. For example, as described in Examples 3 and 4, heat dissipation can be improved even when Al foil is used for the negative electrode. The cooling environment is an example, and it can be applied even when other refrigerants are used. In addition, although a prismatic battery is used as the shape of the lithium ion battery in this embodiment, the effect can be obtained by using other shapes such as a laminate type, a cylindrical type, and the like.

When the unit cells are used as a battery group, the unit cells are connected in series or in parallel. At this time, in order to ensure safety, a member capable of ensuring insulation between the cells may be introduced around the cells, as shown in Example 7, for example. The shape of the member can be freely selected, and the material can be freely selected. Preferably, the member should include a heat transfer member. When the cells are connected in series or in parallel, the wiring to be used is not particularly limited, but an example is a bus bar. Regardless of the type of series or parallel connection, the battery arrangement and external terminal configuration according to the present invention are effective. For example, the effect of the present invention can be obtained even with a battery group in which two battery groups connected in parallel are connected in series to six battery groups. In addition to electrically connecting the unit cells in series or in parallel, it is preferable to physically restrain the unit cells using a fixing jig. However, the method of restraint is not limited to the present invention. For example, the effect was obtained both when two battery groups were lashed using one set of fixing jigs and when two sets of lashing jigs were used.

In the present invention, a battery pack is constructed based on a first battery group and a second battery group that are connected by the means described above. (Battery Management System; BMS, etc.) and a safety mechanism (for example, a fuse, etc.) may be provided, and the effect of the present invention can be obtained even if these are connected to the wiring in the battery group.

The method of contact between the bottom surface of the housing and the battery group is not particularly limited. Although the shape of the housing is a rectangular parallelepiped in this embodiment, the shape is not particularly limited. Further, the effect of the present invention is not limited to the current application conditions and cooling conditions to the battery pack.

The present invention will be described in further detail below based on examples and comparative examples. FIG. 1 is an exploded perspective view of a battery pack 100 of the present invention. In the following description, when referring to up, down, left, right, front and back, the directions shown at the bottom left of each drawing are used.

The battery pack 100 includes a first battery group 10A, a second battery group 10B, and a housing 5 (5a, 5b) that houses the first battery group 10A and the second battery group 10B. The housing 5 consists of a case 5a and a lid 5b that closes the case opening. In this embodiment, the bottom surface 5b is a separate member, but the case 5a may have a bottom surface and an opening on the top surface, and the lid 5b may be arranged on the top surface side.

FIG. 15 is a diagram showing a storage battery 1 used in the present invention. The storage battery 1 comprises a pair of wide surfaces 1a, a pair of narrow surfaces 1b, a bottom surface 1c, and a lid 1d. A positive electrode external terminal 2a and a negative electrode external terminal 2b are provided on the lid 1d.

Returning to FIG. 1 again, the first battery group 10A and the second battery group 10B will be described. The first battery group 10A is formed by stacking a plurality of storage batteries 1 (six in this embodiment) with their wide surfaces 1a facing each other. As with the first battery group 10A, the second battery group 10B also has a structure in which the storage batteries are stacked with their wide faces facing each other.

The storage batteries 1 that constitute the first battery group 10A are connected in series with each other via a bus bar 2 . Similarly, in the second battery group 10B, the storage batteries 1 are connected in series with each other via the busbars 2 . The storage battery 1 on the bottom surface 5b side of the first battery group 10A and the storage battery 1 on the bottom surface 5b side of the second battery group 10Bno are connected to each other by a bus bar 2 . Each of the two battery groups 10A and 10B has an external terminal 3 arranged at the center of the upper surface of the battery pack 100 to be connected to other electronic components (such as a junction box) housed in the battery pack 100. there is In the present invention, temperature changes of the battery pack 100 were measured in several ways (FIGS. 1 to 7).

(Example 1)
First, Example 1 will be described. After the first battery group and the second battery group were laid flat as shown in FIG. 1 and directly thermally connected, a copper HV cable with a diameter of 95 mm was connected to the ends of the positive electrode external terminal and the negative electrode external terminal. attached and current was applied. The amount of heat generated from the battery at this time was 3 W on average.

Also, as a cooling condition, air was applied only to the bottom plate through the housing at the bottom of the battery group at a wind speed of 5 m/sec. FIG. 1 shows the upper surface of the housing. FIG. 8 shows the results when a substantially steady state was reached after applying this condition to the battery pack.

(Example 2)
Next, Example 2 will be described. Example 2 differs from Example 1 in that a flat plate-like heat conducting member 4 is interposed after the first battery group and the second battery group are laid flat.

FIG. 2 shows the structure of this embodiment. In this embodiment, as described above, the heat conducting member 4 is arranged between the first battery group 10A and the second battery group 10B. Two thicknesses of the heat conducting member, 3 mm and 15 mm, were prepared, and the temperature rise of the battery pack 100 when using each of them was measured. The results are shown in FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Example 3)
Next, Example 3 will be described. Example 3 differs from Example 1 in that the material of the negative electrode current collector foil is changed from copper foil to aluminum current collector foil.

Since the specific structure of the battery pack 100 has the same positional relationship as in FIG. 1, the description thereof is omitted. The results of the temperature rise of battery pack 100 are shown in FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Example 4)
Next, Example 4 will be described. Example 4 is different from Example 2 in that aluminum current collector foil is used instead of copper foil as the material of the negative electrode current collector foil. Since the specific structure of the battery pack 100 has the same arrangement relationship as in FIG. 2, the description thereof is omitted. In this embodiment, a member having a thickness of 15 mm is used as the heat conducting member 4 . The results of the temperature rise of battery pack 100 are shown in FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Example 5)
Next, Example 5 will be described. In the fifth embodiment, compared with the first embodiment, the first battery group 10A and the second battery group 10B are arranged vertically as shown in FIG. It differs in that it is brought into contact with the bottom surface of the housing 5 . The results of the temperature rise of battery pack 100 are shown in FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Example 6)
Next, Example 6 will be described. In the sixth embodiment, as compared with the second embodiment, the first battery group and the second battery group are arranged vertically as shown in FIG. The difference is that the bottom surface of 5 is brought into contact. In addition, in this embodiment, two thicknesses of the thermally conductive member 4, one having a thickness of 3 mm and the other having a thickness of 15 mm, are prepared in the same manner as in the second embodiment, and the respective measurement results are shown in FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Example 7)
Next, Example 7 will be described. This embodiment differs from Embodiments 1 to 6 in that a first battery group and a second battery group in which six storage batteries 1 are connected in series are connected in series, and the bottom surface of the storage battery 1 is the housing of the battery pack 100. It has a structure provided so as to be in contact with the bottom surface 5b of the. Note that the heat conducting member 4 is arranged between the first battery group 10A and the second battery group 10B in this embodiment as well. An aluminum flat plate having a thickness of 15 mm is used as the heat conducting member 4 . The results of the temperature rise of battery pack 100 are shown in FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Comparative example 1)
Next, Comparative Example 1 will be described. Comparative Example 1 is different from Examples 1 to 7 in that the battery group is not divided into two but is stacked as a single battery group.

FIG. 6 is a diagram of a battery pack 100 of Comparative Example 1. FIG. A single battery group is formed by connecting 12 batteries 1 in series, and is arranged so that the wide surface 1 a of the single battery 1 is in contact with the bottom surface 5 b of the housing 5 . The results of the temperature rise of the battery pack 100 are shown in FIGS. 8 and 9. FIG. The cooling conditions and current application conditions are the same as in the first embodiment.

(Comparative example 2)
Next, Comparative Example 2 will be described. Comparative Example 2 differs from Examples 1 to 7 in that the battery group is not divided into two but is stacked as a single battery group, and the narrow surface 1b of the unit cell 1 and the bottom surface 5b of the housing 5 are stacked. The difference is the point of contact.

FIG. 7 is a diagram of a battery pack 100 of Comparative Example 2. FIG. A single battery group is formed by connecting 12 batteries in series, and is arranged so that the narrow surface 1b of the unit cell 1 is in contact with the bottom surface 5b of the housing 5. As shown in FIG. The results of the temperature rise of the battery pack 100 are shown in FIGS. 10 and 11. FIG. The cooling conditions and current application conditions are the same as in the first embodiment. The effects of this patent will be described below based on the results of Examples and Comparative Examples.

As a result of applying the conditions shown in this example and comparative example to the battery group, when the temperature of the battery group reached a steady state, the battery temperature increased compared to the environmental temperature. 8 to 11 are diagrams showing, for each cell in the battery group, the ratio of the temperature rise with respect to the environmental temperature to the temperature rise of the cell with the smallest temperature rise. The cell numbers in the figure correspond to the cell numbers described in the figures corresponding to the respective examples and comparative examples. At this time, for the two battery groups in the example, since the temperature of the unit cells present in the locations facing each other in the battery groups was substantially the same, the description is omitted for the sake of simplicity. The results of each figure will be explained in detail below.

FIG. 8 shows the temperature rise ratios of the configurations of Examples 1 and 2, which are examples in which the present invention is applied to the batteries laid flat as in Comparative Example 1. FIG. As can be seen from the figure, in the comparative example, which has a conventional configuration, cell No. 1, which is the central portion of the stacked batteries, is shown. It can be seen that the temperature of 7 is the maximum. This is cell no. In batteries near 7, the heat generated by the surrounding batteries is not radiated, so not only the temperature of the battery itself, but also the temperature of the surrounding batteries is high, and there is no temperature difference, so heat does not flow easily. This is because the battery temperature is high. On the other hand, the temperature rise of the cell No. 1, which is in contact with the bottom surface of the housing, and the battery of cell No. 12, which has an external terminal, are suppressed because of the existence of the heat radiation path. From the above results, a difference in temperature rise between cell No. 1 or cell No. 12 and cell No. 7 was observed. Therefore, it can be seen that in Comparative Example 1, temperature differences between the cells tend to appear.

On the one hand, FIG. 8 at the same time shows an embodiment of the invention. In the present invention, since the rate of temperature rise between batteries is compared in all cells existing in the same arrangement, it can be seen that the rate of temperature rise in all cells can be reduced compared to the comparative example. Further, it can be seen that disposing the heat transfer member between the battery groups as shown in Example 2 further enhances the effect and alleviates the temperature difference between the batteries. This means that the heat dissipation path can be effectively secured by arranging the external terminal in cell No. 6 where the temperature is the highest. In addition, in Example 2, the introduction of the Al plate also ensured a heat radiation path, so it can be seen that the temperature rise difference between the batteries could be effectively reduced.

FIG. 9 shows the temperature rise rates of the configurations of Examples 3 and 4, which are examples in which the present invention is applied to the battery configuration in which the battery is laid flat as in Comparative Example 1. In FIG. It can be seen from the figure that even when the negative electrode current collector foil is made of Al, the temperature difference between the batteries tends to be alleviated in the same manner as shown in FIG. The thermal behavior that occurs in FIG. 9 is due to the same phenomenon that occurred in FIG.

FIG. 10 shows the configurations of Examples 5 and 6, which are examples in which the present invention is applied to the vertically arranged battery configuration as in Comparative Example 2. FIG. From the figure, it can be seen that in the comparative example, which has a conventional configuration, the cell No. 1, which is the central portion where the batteries are stacked, is located. It can be seen that the temperature of 6 is the maximum. The temperature rise that occurs here is caused by the same phenomenon as the behavior that appeared in Comparative Example 1 shown in FIG.

Further, from the figure, it can be seen that the temperature difference between the batteries is alleviated even when the batteries are placed vertically, as in FIGS. The temperature near the center of the long side surface also tends to be high when it is placed vertically instead of horizontally. It can be seen that by arranging the external terminal and the external terminal in that portion, the same effect as in FIGS. 8 and 9 can be obtained, and the temperature rise difference can be reduced.

FIG. 11 compares the temperature difference in the case where the present invention is applied in the configuration shown in Example 7 with respect to the battery configuration in which the batteries are placed vertically as in Comparative Example 2. In FIG. From the figure, it can be seen that the temperature difference tends to be moderated in the present invention as well. It can be seen that in Example 7 as well, heat was effectively dissipated to the outside of the battery group by installing an external terminal in cell No. 6, which has the highest battery temperature.

The battery pack according to the present invention comprises a plurality of storage batteries (1) each having a battery can side surface (1a, 1b) and a battery can bottom surface (1c) connected to the battery can side surface (1a, 1b). 1b) facing each other and stacked, and a storage battery (1) having a battery can side surface (1a, 1b) and a battery can bottom surface (1c) connected to the battery can side surface (1a, 1b). A second battery group (10B) in which a plurality of the battery can sides (1a, 1b) are opposed to each other, and a housing for housing the first battery group (10A) and the second battery group (10B) A body (5) is provided, and the first battery group (10A) and the second battery group (10B) are characterized in that the facing surfaces are directly or indirectly thermally connected to each other. By adopting such a structure, it is possible to provide a battery pack in which the temperature difference between battery groups is reduced.

Further, in the present invention, the structure is such that the wide surfaces (1a) of the two battery groups face the bottom surface of the housing (5). With such a structure, the cooling area is increased, and the cooling performance is improved as compared with the case where the narrow surface 1b is brought into contact with the housing 5. FIG.

In addition, in the battery pack according to the present invention, when the wide surface 1a of the battery 1 is placed downward, the external terminals 3 are located at the center of the battery pack, thereby cooling the center of the battery pack from which heat is less likely to escape. , can be done via an external terminal. Therefore, it is possible to provide a battery pack with improved heat dissipation and reduced temperature difference between battery groups.

Further, as shown in FIG. 12, in the battery pack according to the present invention, the first heat transfer member (6) is provided between the first battery group (10A) and the second battery group (10B). The heat transfer member (6) is placed in close contact with the first battery group (10A) and the second battery group (10B). With such a structure, it is possible to provide a battery pack in which the heat transfer member facilitates heat diffusion and reduces the temperature difference between the battery groups. 12 is a top view of FIG. 2. FIG.

Further, in the battery pack according to the present invention, as shown in FIG. 13, the second heat transfer member 61 and the third heat transfer member 62 are provided on both sides of the first battery group 10A and the second battery group 10B. may be placed. In this case, the first battery group 10A is sandwiched between the heat transfer member 6 and the second heat transfer member 61, and the second battery group 10B is sandwiched between the heat transfer member 6 and the third heat transfer member 10B. , the heat dissipation is improved on both sides of the battery groups 10A and 10B, and it is possible to provide a battery pack in which the temperature difference between the battery groups is further reduced.

Moreover, the battery pack according to the present invention has a structure in which both the second heat transfer member 61 and the third heat transfer member 62 are wider than the first heat transfer member 6 . With such a structure, the housing 5 and the heat transfer members 61 and 62 can be fixed to each other with screws or the like. Therefore, the heat generated by the battery 1 can be more easily transferred to the housing 5, making it possible to provide a battery pack with improved cooling performance.

In the battery pack according to the present invention, as shown in FIG. 14, the first heat transfer member 6 is thicker than the second heat transfer member 61 and the third heat transfer member 62. It's becoming By adopting such a structure, it is possible to provide a battery pack with improved cooling performance by further promoting heat diffusion between the two battery groups with the worst heat dissipation. In the present invention, the battery pack of the type in which the wide surface 1a of the battery 1 is in contact with the bottom surface of the housing 5 is used for natural cooling such that cooling air does not flow between the battery groups or between the cells. Very effective in case. Therefore, the present invention is very suitable for a structure in which the battery 1 is laid horizontally. Further, the present invention relates to a battery group in which a plurality of storage batteries each formed in a rectangular parallelepiped having a wide surface and a narrow surface are stacked with the wide surfaces facing each other, the first battery comprising: A battery pack comprising a battery group and a second battery group, wherein the first battery group and the second battery group are arranged side by side and housed in a housing such that the narrow sides of the storage batteries face each other. A first heat transfer member is disposed between the first battery group and the second battery group, and the first heat transfer member is disposed between the first battery group and the second battery group. The first battery group and the second battery group are placed on the center side of the battery pack in the storage batteries on the upper surfaces of the first battery group and the second battery group, respectively. is provided with an external terminal for connecting to an electronic circuit in the housing, and heat is dissipated through the external terminal. and a third heat transfer member, the first battery group is sandwiched between the first heat transfer member and the second heat transfer member, and the second battery group is connected to the first heat transfer member It is sandwiched between a heat transfer member and the third heat transfer member, and the second heat transfer member and the third heat transfer member are thicker than the first heat transfer member. The battery pack according to the present invention is further characterized in that the first battery group is sandwiched between the first heat transfer member and the second heat transfer member, and the second battery group is sandwiched between the heat transfer member and the third heat transfer member, and the first heat transfer member is thinner than the second heat transfer member and the third heat transfer member It is a battery pack that

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the invention described in the claims. Changes can be made. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration.

REFERENCE SIGNS LIST 1 cell 2 wiring 3 external terminal 4 bottom surface of housing 5 top surface of housing 6, 61, 62 heat transfer member

Claims (6)

A first battery group in which a plurality of storage batteries each formed as a rectangular parallelepiped having a pair of wide surfaces and other narrow surfaces are stacked on a housing such that the wide surfaces face each other. and a second battery group,
a metal heat transfer member;
Narrow surfaces other than the pair of wide surfaces,
a first narrow surface having external terminals;
a second narrow surface facing the first narrow surface;
Consisting of a third narrow surface as a side surface other than the first narrow surface and the second narrow surface,
The first battery group and the second battery group are connected to the third narrow surface of the first battery group and the second battery group through the heat transfer member. housed in the housing so as to face the third narrow surface in
A battery pack characterized by: A first battery group in which a plurality of storage batteries each formed as a rectangular parallelepiped having a pair of wide surfaces and other narrow surfaces are stacked on a housing such that the wide surfaces face each other. and a second battery group,
A battery pack comprising a heat transfer member,
Narrow surfaces other than the pair of wide surfaces,
a first narrow surface having external terminals;
a second narrow surface facing the first narrow surface;
Consisting of a third narrow surface as a side surface other than the first narrow surface and the second narrow surface,
The first battery group and the second battery group are connected to the third narrow surface of the first battery group and the second battery group through the heat transfer member. Housed in the housing so as to face the third narrow surface in
Terminals for connecting the first battery group and the second battery group to a device outside the battery are provided on the storage battery separately from the external terminal on the central side of the battery pack,
A battery pack characterized by: The battery pack according to claim 1 or 2,
A battery pack, wherein the storage batteries of the battery group are connected to adjacent storage batteries by connecting members. The battery pack according to any one of claims 1 to 3,
A battery pack, wherein the first narrow faces of the batteries of the first battery group and the first narrow faces of the batteries of the second battery group face the same side. The battery pack according to any one of claims 1 to 4,
A battery pack, comprising: the storage battery arranged so that the wide surface faces the housing. A first battery group in which a plurality of storage batteries each formed as a rectangular parallelepiped having a pair of wide surfaces and other narrow surfaces are stacked on a housing such that the wide surfaces face each other. and a second battery group,
A battery pack comprising a heat transfer member,
Narrow surfaces other than the pair of wide surfaces,
a first narrow surface having external terminals;
a second narrow surface facing the first narrow surface;
Consisting of a third narrow surface as a side surface other than the first narrow surface and the second narrow surface,
The first battery group and the second battery group are connected to the third narrow surface of the first battery group and the second battery group through the heat transfer member. Housed in the housing so as to face the third narrow surface in
Connected to the external terminals of the storage battery located on the end faces of the first battery group and the second battery group respectively on the central side of the battery pack, the first battery group and the second battery group Provided with a terminal to connect each and the device outside the battery,
A battery pack characterized by:

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