JP2012160283A - Battery pack and battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack and a battery module which eliminate nonuniformity of cooling for heat generated from multiple unit cells with a simple structure, and achieve long life.SOLUTION: A battery pack includes multiple unit cells 100 electrically connected with each other, multiple battery modules 800 electrically connected with each other in parallel, and a cooling part 400 cooling each battery module 800. The unit cells 100 have the same internal resistance and the same electric capacitance in the battery modules 800. The battery modules 800 are arranged in a line in the flow direction of a cooling medium. The internal resistance and the electric capacitance of the unit cells 100 forming the battery modules 800 on the upstream side are larger than the internal resistance and the electric capacitance of the unit cells 100 forming the battery modules 800 on the downstream side.

Description

  The present invention relates to a battery pack and a battery module in which nonuniformity of cooling with respect to heat generation of a plurality of unit cells is eliminated.

  A battery module in which a large number of high-performance unit cells such as nickel metal hydride batteries and lithium batteries are equally arranged is used as a power source for moving bodies such as hybrid vehicles.

  If the temperature difference between the unit cells during charging / discharging is large, there is a possibility that a specific unit cell will be rapidly deteriorated and the life of the battery module may be shortened. It is necessary to eliminate the non-uniformity of the temperature difference at.

  Patent Document 1 describes a battery module having a cooling unit for stacking unit cells in a vertical direction in a holder case and forming a cooling air blown from the lower side between the unit cells. In such a case, cooling of the upper unit cell that is leeward becomes a problem, but a louver member having a predetermined shape is provided near the upper unit cell in the holder case in order to collect cooling air to the upper unit cell. Thus, the temperature difference between the upper and lower unit cells is eliminated.

JP 2007-165164 A

  However, the above-mentioned technique is disadvantageous in terms of the number of parts because the louver member having a predetermined shape is provided in the holder case, and a space for providing the louver member needs to be formed, so that the configuration is complicated. Become.

  The present invention has been made in view of such problems, and provides a battery pack and a battery module having a long life by eliminating the non-uniformity of cooling with respect to heat generation of a plurality of unit cells by a simple structure. Objective.

  A battery pack according to a first aspect of the present invention includes a plurality of electrically connected unit cells, a plurality of battery modules electrically connected in parallel, and the plurality of battery modules. A battery pack that cools by flowing a cooling medium, and the unit cells included in each battery module have the same or equivalent internal resistance and electric capacity in each battery module, Are arranged in a line along the direction of the flow of the cooling medium by the cooling unit, and the internal resistance and electric power of the unit cell constituting the battery module arranged upstream of the flow of the cooling medium. A capacity | capacitance is larger than the internal resistance and electric capacity of the unit cell which comprises the battery module arrange | positioned downstream.

  In the case where a plurality of battery modules are arranged in parallel, the inventors of the present invention discharge a unit cell having a large internal resistance and electric capacity than a unit cell having a small internal resistance and electric capacity at the final stage of charging and discharging. I found that the current is large as a new finding. Therefore, according to the above-described configuration, the battery module constituted by the unit cell having a large internal resistance and electric capacity is arranged on the upstream side of the flow of the cooling medium, while the cell module is constituted by the unit cell having a small internal resistance and electric capacity. The battery module is placed downstream of the flow of the cooling medium, so that in the final stage of charging / discharging with a large temperature difference, the cooling effect on the heat generation of multiple unit cells is made uniform, and a specific unit cell is rapidly It is possible to prevent the battery pack from being deteriorated and to extend the life of the battery pack.

Further, a unit cell constituting a battery module arranged on the upstream side of the cooling medium is a unit cell A, and a unit cell constituting a battery module arranged on the downstream side of the cooling medium is a unit cell B, and the frequency is 1 kHz. the internal resistance of the battery a as measured by alternating _{R a,} is _{R a} and _R ratio 1.2 ≦ _R a / _{R B} ≦ 3.0 for _B when the internal resistance was _{R B} of the battery B, battery a the electrical capacitance _{C a,} it is preferred ratio of _{C a} and _{C B} electric capacity of the battery B when the _{C B} is _{1.2 ≦ C a / C B ≦} 2.2.

When the ratio of R _A and R _B is smaller than 1.2, the battery module is composed of a unit cell B on the downstream side of the cooling medium. The temperature may be higher than that of the battery module configured with the unit cell A on the upstream side of the cooling medium. Also, if the ratio of R _A and R _B is greater than 2.2, the heat generation of the battery module composed of the unit cells A upstream of the cooling medium will be too high, and the upstream of the cooling medium Can be inefficient. Furthermore, the ratio of R _A and R _B is greater than 3.0, the possibility of current difference during charging and discharging of the battery module configured in a battery module and the battery cell B composed of a unit cell A is increased There is.

Further, the ratio of C _A and C _B is less than 1.2, there is a case where substantially the same behavior as if they were arranged cell of the same electric capacity. On the other hand, if the ratio of C _A and C _B is larger than 2.2, the heat generation of the battery module constituted by the unit cell A on the upstream side of the cooling medium may become too high.

  A battery module according to a second aspect of the present invention is a battery module formed by aggregating at least two types of unit cells having different internal resistances that are electrically connected in parallel. The internal resistance and electric capacity of the unit cell arranged on the outer side are larger than the internal resistance and electric capacity of the unit cell arranged on the central side. And

  As described above, when a plurality of unit cells are electrically connected in parallel, at the final stage of charge / discharge, a unit cell having a large internal resistance and a large capacitance is more than a unit cell having a small internal resistance and a specific capacitance. Also has a large discharge current. Therefore, according to the above-described configuration, the unit cell having a large internal resistance and electric capacity is arranged outside the battery module, while the unit cell having a small internal resistance and electric capacity is arranged on the center side of the battery module. In the final stage of charging / discharging with a large temperature difference, the heat of the unit cells arranged on the outside is preferentially dissipated to the outside, and the cooling effect on the heat generation of the plurality of unit cells is made uniform. Long life can be achieved.

Further, the unit cell arranged outside is unit cell O, the unit cell arranged on the center side is unit cell I, and the internal resistance of the battery O measured by alternating current with a frequency of 1 kHz is R _O. When the resistance is R _I , the ratio of R _O and R _I is 1.2 ≦ R _O / R _I ≦ 3.0, the electric capacity of the battery O is C _O , and the electric capacity of the battery I is C _I Sometimes it is preferred that the ratio of C 2 _O to C ₁ is 1.2 ≦ C _O / C _I ≦ 2.2.

  A battery pack according to a third aspect of the present invention includes a plurality of unit cells that are electrically connected in parallel, and a cooling unit that cools the plurality of unit cells by flowing a cooling medium. In the pack, the plurality of unit cells are arranged in a line along the direction of the flow of the cooling medium by the cooling unit, and the internal resistance of the unit cell arranged on the upstream side of the flow of the cooling medium The electric capacity is larger than the internal resistance and electric capacity of the unit cell arranged on the downstream side.

  According to the above-described configuration, when a plurality of unit cells are arranged in parallel, the unit cells having large internal resistance and electric capacity are arranged on the upstream side of the flow of the cooling medium, while the internal resistance and electric capacity are Since the small unit cells are arranged on the downstream side of the flow of the cooling medium, the cooling effect on the heat generation of multiple unit cells is made uniform in the final stage of charging / discharging with a large temperature difference, thereby extending the life of the battery pack. Can be achieved.

In addition, the unit cell arranged upstream of the cooling medium is a unit cell X, and the unit cell arranged downstream of the cooling medium is a unit cell Y. R _X, the ratio of _{R X} and _{R Y} when the internal resistance of the battery Y was _{R Y} is is _{1.2 ≦ R X / R Y ≦} 3.0, the electric capacity of the battery X _{C X,} the battery Y it is preferred ratio of _{C X} and _{C Y} are _{1.2 ≦ C X / C Y ≦} 2.2 when the electrical volume of _{C Y.}

  According to the present invention, by a simple configuration in which a unit cell having a large internal resistance and electric capacity and a unit cell having a small internal resistance and electric capacity are arranged at predetermined positions, the non-uniformity of cooling with respect to heat generation of a plurality of unit cells is eliminated. Thus, a long-life battery pack and battery module can be obtained.

1 is a schematic diagram of a battery pack according to Embodiment 1. FIG. It is sectional drawing which showed the structure of the unit cell typically. It is sectional drawing of a battery module. It is a figure which shows the relationship of an electric current (A) versus discharge time (s) in case a some unit cell is arranged in parallel. It is a figure which illustrates schematically the battery module which concerns on 2nd Embodiment in which unit cells are arranged in zigzag form. It is a figure which illustrates schematically the battery pack which connected the battery module which concerns on 2nd Embodiment. It is a figure which illustrates schematically the battery module which concerns on 2nd Embodiment by which a unit cell is arranged in the grid | lattice form (array form). It is a figure which illustrates roughly the battery pack which connected the battery module by which the unit cell was arranged in the grid | lattice form. It is a figure which illustrates schematically the battery pack which concerns on 3rd Embodiment.

<< First Embodiment >>
Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. However, the embodiments are for facilitating understanding of the principle of the present invention, and the scope of the present invention is as follows. The present invention is not limited to the embodiments, and other embodiments in which those skilled in the art appropriately replace the configurations of the following embodiments are also included in the scope of the present invention.

  FIG. 1 is a schematic diagram of a battery pack 900 according to the first embodiment. As shown in FIG. 1, the battery pack 900 according to the present embodiment includes a plurality of battery modules 800 that are electrically connected in parallel, a cooling unit 400 that cools the battery modules 800 with a cooling medium, It has.

  The plurality of unit cells 100 included in the battery module 800 have the same internal resistance and electric capacity in each battery module, and are electrically connected in series or in parallel. In the present embodiment, the unit cell 100 uses two types of unit cells 100, which are a unit cell 100a having a large internal resistance and electric capacity and a unit cell 100b having a small internal resistance and electric capacity.

  The cooling unit 400 discharges a cooling medium as cooling air, for example, from a cooling medium discharge port (not shown) as indicated by an arrow. The cooling medium is not particularly limited as long as it can cool the heat generated by charging / discharging of the unit cell 100, and may be a liquid such as cooling water, for example.

  Next, the unit cell 100 constituting the battery module 800 will be described. FIG. 2 is a cross-sectional view schematically showing the configuration of the unit cell 100. The unit cell 100 can employ, for example, a cylindrical lithium ion secondary battery as shown in FIG. This lithium ion secondary battery is provided with a safety valve mechanism that releases gas to the outside of the battery when the pressure in the battery increases due to the occurrence of an abnormality such as an internal short circuit.

  In the unit cell 100, an electrode group 104 in which a positive electrode 101 and a negative electrode 102 are wound through a separator 103 is housed in a battery case 107 together with a non-aqueous electrolyte. Insulating plates 109 and 110 are arranged above and below the electrode group 104, the positive electrode 101 is joined to the filter 112 via the positive electrode lead 105, and the negative electrode 102 is also connected to the negative electrode terminal via the negative electrode lead 106. Is joined to the bottom.

A paste containing a positive electrode active material and a negative electrode active material is applied to the surfaces of the positive electrode and the negative electrode, respectively. As the positive electrode active material, for example LiMn ₂ O _4, LiCoO _2, LiNiO _2, etc., can be used without particular limitation one or more of the positive electrode active material used in lithium ion batteries. As the negative electrode active material, for example, one or more negative electrode active materials used in lithium ion batteries, such as amorphous carbon and graphite carbon, can be used without particular limitation. As the non-aqueous electrolyte, for example, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like can be used.

  The filter 112 is connected to the inner cap 113, and the protrusion of the inner cap 113 is joined to the metal valve plate 114. Further, the valve plate 114 is connected to a terminal plate 108 that also serves as a positive electrode terminal. The terminal plate 108, the valve plate 114, the inner cap 113, and the filter 112 are integrated to seal the opening of the battery case 107 via the gasket 111.

  When an abnormality such as an internal short circuit occurs in the unit cell 100 and the pressure in the unit cell 100 increases, the valve body 114 swells toward the terminal plate 108, and the inner cap 113 and the valve body 114 are disconnected. The current path is interrupted. When the pressure in the unit cell 100 further increases, the valve body 114 is broken. As a result, the gas generated in the unit cell 100 is discharged to the outside through the through hole 112a of the filter 112, the through hole 113a of the inner cap 113, the tear of the valve body 114, and the opening 108a of the terminal plate 108. Is done.

  Next, each battery module 800 will be described. FIG. 3 is a cross-sectional view of the battery module 800. As shown in FIG. 3, in the battery module 800, a plurality of unit cells 100, 100,. The case 340 includes a lid 323, a housing 325, and a partition plate 327. The lid body 323 and the housing 325 sandwich the partition plate 327. In such a case 340, the space formed by the housing 325 and the partition plate 327 is the battery chamber 331, and the space formed by the lid 323 and the partition plate 327 discharges the gas to the outside. 333.

  In the battery chamber 331, the plurality of unit cells 100, 100,... Are accommodated in the housing 325 with the open portion 108a facing upward, and are arranged in the longitudinal direction of the case 340. Through holes are formed in the partition plate 327 at intervals in the longitudinal direction, and the open portion 108a of the unit cell 100 is exposed from each of the through holes.

  An exhaust port portion 329 is formed in the exhaust chamber 333. Specifically, a notch is formed in one end surface in the longitudinal direction of the lid 323, whereby a gap exists between the lid 323 and the housing 325 at one longitudinal end of the case 340. This gap is the exhaust port 329.

  Next, returning to FIG. 1, in the present embodiment, the battery modules 800 are arranged in a line along the direction of the flow of the cooling medium indicated by the arrows in FIG. 1. In this embodiment, the battery module 800a configured by the unit cell 100a having a large internal resistance and electric capacity is arranged on the upstream side of the cooling medium, and the battery module configured by the unit cell 100b having a small internal resistance and electric capacity. 800b is arranged downstream of the cooling medium. In this embodiment, the battery modules 800 are arranged in a single row, but the “arrangement in a row” is a concept including not only one row but also an arrangement of two or more rows.

  The internal resistance of the unit cell 100a constituting the battery module 800a arranged on the upstream side is not particularly limited, but may be, for example, 20 mΩ or more and 30 mΩ or less. In addition, the internal resistance of the unit cell 100b constituting the battery module 800b disposed on the downstream side is not particularly limited, but may be, for example, 10 mΩ or more and 18 mΩ or less.

  The electric capacity of the unit cell 100a constituting the battery module 800a arranged on the upstream side is not particularly limited, but can be, for example, 2.5 Ah or more and 3.4 Ah or less. In addition, the electric capacity of the unit cell 100b constituting the battery module 800b disposed on the downstream side is not particularly limited, but may be, for example, 1.6 Ah or more and 2.2 Ah or less.

For the unit cell A constituting the battery module 800a arranged on the upstream side and the unit cell B constituting the battery module 800b arranged on the downstream side, the internal resistance of the battery A measured by alternating current at a frequency of 1 kHz is represented by R _A it is preferred ratio of _{R a} and _{R B} when the internal resistance of the battery B was _{R B} is _{1.2 ≦ R a / R B ≦} 3.0. Also, the electric capacity of the battery A _{C A,} it is preferred ratio of _{C A} and _{C B} electric capacity of the battery B when the _{C B} is _{1.2 ≦ C A / C B ≦} 2.2.

  Next, the effect of the battery pack 900 having the above-described configuration will be described.

FIG. 4 is a diagram showing a relationship of current (A) versus discharge time (s) when a plurality of unit cells are arranged in parallel. As unit cell A having a high internal resistance and electric capacity, two batteries (battery 1 and battery 2) having an internal resistance R _{A of} 25 mΩ and an electric capacity C _{A of} 2.9 Ah measured with an alternating current of 1 kHz, and the internal resistance and the electric capacity As the unit cell B, a total of four batteries are connected in parallel, including two batteries (batteries 3 and 4) having an internal resistance R _{B of} 13 mΩ and an electric capacity C _{B of} 2.0 Ah measured with an alternating current of 1 kHz. . R _A / R _B is 1.923, and C _A / C _B is 1.45. Then, charging or discharging is performed at 1C, and charging or discharging is stopped after 3600 seconds.

  Charging and discharging are the same graph as shown in FIG. 4 and will be described as discharging here. As shown in FIG. 4, in the initial stage of discharge, the batteries 1 and 2 have a smaller discharge current than the batteries 3 and 4. As the discharge proceeds, the discharge currents of the batteries 1 and 2 and the discharge currents of the batteries 3 and 4 become the same (about 500 s). Further, as the discharge proceeds, the discharge currents of the batteries 1 and 2 are larger than those of the batteries 3 and 4, and at the final stage of the discharge, the difference between the two discharge currents becomes significantly large. Finally, when the discharge is stopped (3600 s), since there is a voltage difference between the batteries 1 and 2 and the batteries 3 and 4, a current of 100 to 300 s flows from the batteries 1 and 2 to the batteries 3 and 4. In the batteries 3 and 4, when the voltage difference disappears, no current flows.

  Therefore, as shown in FIG. 1, a battery module 800a composed of a unit cell 100a having a large internal resistance and electric capacity is arranged on the upstream side of the cooling medium, and is composed of a unit cell 100b having a small internal resistance and electric capacity. By disposing the battery module 800b on the downstream side of the cooling medium, the cooling effect on the heat generation of the plurality of unit cells can be made uniform in the final stage of charge / discharge with a large temperature difference.

<< Second Embodiment >>
In the first embodiment described above, the internal resistance and the electric capacity of the unit cell 100 provided in each battery module 800 have the same value. However, in the present embodiment, the unit cell 100 provided in the battery module 800 has the same value. The internal resistance and capacitance are different values.

  FIG. 5 is a diagram schematically illustrating a battery module 800 according to the second embodiment in which the unit cells 100 are arranged in a staggered manner. In the battery module 800 according to the present embodiment, the unit cells 100 are electrically connected in parallel. As shown in FIG. 5, the unit cell 100 uses two different types of unit cells 100, a unit cell 100 a having a large internal resistance and electric capacity and a unit cell 100 b having a small internal resistance and electric capacity. Yes. The configuration of the unit cell 100 included in the battery module 800 and the arrangement of the unit cell 100 in the battery module 800 are the same as those in the first embodiment.

  The unit cells 100 are arranged in a staggered pattern, for example, five in the upper row, four in the middle row, and five in the lower row. Here, the zigzag pattern refers to a state in which the unit cells 100 are arranged at equal intervals in a plurality of rows, and the positions of the unit cells 100 are shifted from each other by adjacent columns, for example, by a half distance. .

  In the present embodiment, the unit cell 100a having a large internal resistance and electric capacity is arranged on the outside, and the unit cell 100b having a small internal resistance and electric capacity is arranged on the center side. Note that all four unit cells arranged in the center of the figure are unit cells 100b having small internal resistance and electric capacity, and the unit cells at the left and right end portions are not unit cells 100a having large internal resistance and electric capacity. This is because these unit cells have a distance from the case 340, so that the heat generated by the unit cells is difficult to dissipate to the outside.

  The internal resistance of the unit cell 100a disposed on the outside is not particularly limited, but can be, for example, 20 mΩ or more and 30 mΩ or less. Further, the internal resistance of the unit cell 100b disposed on the center side is not particularly limited, but can be set to, for example, 10 mΩ or more and 18 mΩ or less.

  The electric capacity of the unit cell 100a disposed on the outside is not particularly limited, but can be, for example, 2.5 Ah or more and 3.4 Ah or less. In addition, the electric capacity of the unit cell 100b disposed on the center side is not particularly limited, but may be, for example, 1.6 Ah or more and 2.2 Ah or less.

R unit cell O are located outside, and, for the unit cell I which is centrally located, the internal resistance of the battery O was measured with an alternating current of a frequency 1 kHz R _O, the internal resistance of the battery I is taken as R _I The ratio of _O and R _I is preferably 1.2 ≦ R _O / R _I ≦ 3.0. Further, the capacitance _{C O} of the battery O, it is preferred ratio of _{C O} and _{C I} when the electric capacity of the battery I was _{C I} is _{1.2 ≦ C O / C I ≦} 2.2.

  Next, the effect of the battery module 800 having the above-described configuration will be described.

  As described above in the first embodiment, when a plurality of unit cells are arranged in parallel, as the charging or discharging proceeds, the unit cell 100a having a large internal resistance and electric capacity has a small internal resistance and electric capacity. The discharge current is larger than that of battery 100b. Therefore, as shown in FIG. 5, the unit cell 100a having a large internal resistance and electric capacity is arranged on the outside, and the unit cell 100b having a small internal resistance and electric capacity is arranged on the center side. In the final stage of discharge, the cooling effect on the heat generation of the plurality of unit cells can be made uniform.

  FIG. 6 is a diagram schematically illustrating a battery pack 900 to which the battery module 800 according to the second embodiment is connected. As shown in FIG. 6, it is possible to form the battery pack 900 by electrically connecting the battery modules 800 described above in series or in parallel. In this battery pack 900, a unit cell 100a having a large internal resistance and electric capacity is arranged on the outside, and a unit cell 100b having a small internal resistance and electric capacity is arranged on the center side.

  Next, as a modification of the battery module 800 described above, the arrangement form of the unit cells 100 can be changed. FIG. 7 is a diagram schematically illustrating a battery module 800 according to the second embodiment in which the unit cells 100 are arranged in a lattice shape (array shape). As shown in FIG. 7, the unit cells 100 can be arranged in a lattice pattern having, for example, five rows and three columns. The battery module 800 is not assumed to be electrically connected to form a battery pack, but is assumed to be used alone. Even in such a case, the unit cell 100a having a large internal resistance and electric capacity is arranged on the outside, and the unit cell 100b having a small internal resistance and electric capacity is arranged on the center side.

  FIG. 8 is a diagram schematically illustrating a battery pack 900 to which a battery module 800 in which the unit cells 100 are arranged in a lattice shape is connected. As shown in FIG. 8, it is also possible to form a battery pack 900 by electrically connecting battery modules 800 in which unit cells 100 are arranged in a lattice shape in parallel. In such a case, unlike the battery module 800 shown in FIG. 7, the cells constituting the upper and lower rows of the figure are unit cells 100a having a large internal resistance and electric capacity, and the unit cells constituting the middle row of the figure are The unit cell 100b has a small internal resistance and electric capacity. In the battery pack 900 configured as described above, the unit cell 100a having a large internal resistance and electric capacity is arranged on the outside, and the unit cell 100b having a small internal resistance and electric capacity is arranged on the center side. In the battery pack 900 shown in FIG. 8, in each battery module 800 located at both ends, the unit cells 100 that are located on the end side that is close to the outside of the unit cells 100 that form the row in the center of the figure. Only the unit cell 100a having a large internal resistance and electric capacity can be used.

<< Third Embodiment >>
In the first embodiment described above, the battery module 800 including the plurality of unit cells 100 is the battery pack 900 arranged in the flow direction of the cooling medium. However, in the present embodiment, in the flow direction of the cooling medium. A battery pack 900 including the unit cells 100 arranged will be described.

  FIG. 9 is a diagram schematically illustrating the battery pack 900 according to the third embodiment. As shown in FIG. 9, the battery pack 900 according to the present embodiment includes a plurality of unit cells 100 electrically connected in parallel, and a cooling unit 400 that cools each unit cell 100 with a cooling medium. It is equipped with.

  In the present embodiment, the unit cell 100 uses two types of unit cells 100, which are a unit cell 100a having a large internal resistance and electric capacity and a unit cell 100b having a small internal resistance and electric capacity.

  As in the first embodiment, the cooling unit 400 discharges, for example, a cooling medium as cooling air from a cooling medium discharge port (not shown) as indicated by an arrow.

  Each unit cell 100 is arranged in a line along the flow direction of the cooling medium indicated by an arrow in FIG. The unit cell 100a having a large internal resistance and electric capacity is arranged on the upstream side of the flow of the cooling medium, and the unit cell 100b having a small internal resistance and electric capacity is arranged on the downstream side of the flow of the cooling medium.

  The internal resistance of the unit cell 100a arranged on the upstream side is not particularly limited, but can be, for example, 1.4 mΩ or more and 2.2 mΩ or less. In addition, the internal resistance of the unit cell 100b disposed on the downstream side is not particularly limited, but may be, for example, 0.8 mΩ or more and 1.2 mΩ or less.

  The electric capacity of the unit cell 100a disposed on the upstream side is not particularly limited, but may be, for example, 25 Ah or more and 30 Ah or less. In addition, the electric capacity of the unit cell 100b disposed on the downstream side is not particularly limited, but may be, for example, 15 Ah or more and 20 Ah or less.

For the unit cell X arranged on the upstream side and the unit cell arranged on the downstream side for the unit cell Y, the internal resistance of the battery X measured by alternating current with a frequency of 1 kHz is R _X , and the internal resistance of the battery Y is R _Y It is preferable that the ratio of R _X and R _Y is 1.2 ≦ R _X / R _Y ≦ 3.0. The electric capacity of the battery X _{C X,} it is preferred ratio of _{C X} and _{C Y} when the electric capacity of the battery Y was _{C Y} is _{1.2 ≦ C X / C Y ≦} 2.2.

  As described above in the first embodiment, when a plurality of unit cells are arranged in parallel, as the charging or discharging proceeds, the unit cell 100a having a large internal resistance and electric capacity has a small internal resistance and electric capacity. The discharge current is larger than that of battery 100b. Therefore, as shown in FIG. 9, the unit cell 100a having a large internal resistance and electric capacity is arranged on the upstream side of the flow of the cooling medium, and the unit cell 100b having a small internal resistance and electric capacity is arranged on the downstream side of the flow of the cooling medium. By arranging in the above, the cooling effect on the heat generation of the plurality of unit cells can be made uniform in the final stage of charge / discharge with a large temperature difference.

<< Other Embodiments >>
In Embodiments 1 to 3 described above, two types of batteries having different internal resistances are used. However, the scope of the present invention is not limited to such embodiments, and three or more types of batteries having different internal resistances are used. Can be used.

  Further, in the above-described embodiment, the unit cell 100 is provided with a safety valve mechanism that releases gas to the outside of the battery when the pressure in the battery rises due to the occurrence of an abnormality, but the scope of the present invention is as described above. However, the present invention is not limited to such an embodiment. The unit cell 100 may not be provided with a safety valve mechanism for releasing gas to the outside of the battery, and may be provided with no exhaust chamber 333 when arranged in a housing.

  Since the battery module and the battery pack according to the present invention have a long life, they are useful for portable electronic devices, mobile communication devices, power sources for vehicles, and the like.

DESCRIPTION OF SYMBOLS 100: Unit cell 101: Positive electrode 102: Negative electrode 103: Separator 104: Electrode group 105: Positive electrode lead 106: Negative electrode lead 107: Battery case 108: Terminal board 109,110: Insulation board 111: Gasket 112: Filter 113: Inner cap 114 : Valve body 200: Battery storage unit 300: Battery holder 323: Cover body 325: Housing 327: Partition plate 333: Exhaust chamber 340: Case 800: Battery module 900: Battery pack

Claims (6)

A plurality of battery modules including a plurality of electrically connected unit cells and electrically connected in parallel; and a cooling unit that cools the plurality of battery modules by flowing a cooling medium. A battery pack,
The unit cells included in each battery module have the same or equivalent internal resistance and electric capacity in each battery module,
The plurality of battery modules are arranged in a line along the direction of the flow of the cooling medium by the cooling unit,
The internal resistance and electric capacity of the unit cell constituting the battery module arranged on the upstream side of the flow of the cooling medium are larger than the internal resistance and electric capacity of the unit cell constituting the battery module arranged on the downstream side. A battery pack characterized by A unit cell constituting a battery module arranged on the upstream side of the cooling medium is a unit cell A, and a unit cell constituting a battery module arranged on the downstream side of the cooling medium is a unit cell B.
The internal resistance of the battery A was measured with an alternating current of a frequency 1 kHz _{R A,} the ratio of _{R A} and _{R B} when the internal resistance of the battery B was _{R B} be 1.2 ≦ _R A / _{R B} ≦ 3.0 ,
Claims, characterized in that the ratio of _{C A} and _{C B} is 1.2 ≦ _C A / _{C B} ≦ 2.2 when the electrical capacity of the battery A was _{C A,} the electric capacity of the battery B and _{C B} The battery pack according to 1. A battery module formed by assembling at least two types of unit cells having different internal resistances electrically connected in parallel,
The unit cell is divided into a central side and an outer side, and
The battery module characterized in that the internal resistance and electric capacity of the unit cell arranged on the outside are larger than the internal resistance and electric capacity of the unit cell arranged on the center side. The unit cell arranged outside is called unit cell O, the unit cell arranged on the center side is called unit cell I,
The internal resistance of the battery O was measured with an alternating current of a frequency 1 kHz _{R O,} the ratio of _{R O} and _{R I} when the internal resistance of the battery I was _{R I} be _{1.2 ≦ R O / R I ≦} 3.0 ,
Claims the electric capacity of the battery O _{C O,} the ratio of _{C O} and _{C I} when the electric capacity of the battery I was _{C I} characterized in that it is a _{1.2 ≦ C O / C I ≦} 2.2 4. The battery module according to 3. A battery pack comprising: a plurality of unit cells electrically connected in parallel; and a cooling unit that cools the plurality of unit cells by flowing a cooling medium,
The plurality of unit cells are arranged in a line along the flow direction of the cooling medium by the cooling unit,
A battery pack, wherein an internal resistance and an electric capacity of a unit cell arranged on the upstream side of the flow of the cooling medium are larger than an internal resistance and an electric capacity of a unit cell arranged on the downstream side. A unit cell arranged upstream of the cooling medium is a unit cell X, a unit cell arranged downstream of the cooling medium is a unit cell Y,
There the internal resistance of the battery X were measured with an alternating current of a frequency 1kHz in _{R X,} the ratio of _{R X} and _{R Y} when the internal resistance of the battery Y was _{R Y} is _{1.2 ≦ R X / R Y ≦} 3.0 ,
Claims an electric capacity of the battery X _{C X,} the ratio of _{C X} and _{C Y} when the electric capacity of the battery Y was _{C Y} characterized in that it is a _{1.2 ≦ C X / C Y ≦} 2.2 5. The battery pack according to 5.

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