Battery cooling system

Abstract

A battery cooling system capable of reducing deterioration bias of a plurality of batteries is provided. The battery cooling system of the present application includes a cooling circuit through which a cooling fluid for cooling a plurality of batteries arranged in a first direction circulates, wherein a cooler that extends in the first direction and cools the plurality of batteries, a liquid feeding device that feeds the cooling fluid and circulates the cooling flow in the cooling circuit, and a fluid cooling device that cools the cooling fluid are provided in the cooling circuit, and the battery cooling system includes a deterioration estimation unit that estimates a deterioration state of an end portion battery of the plurality of batteries that is arranged at an end portion in the first direction and arranged in the cooling fluid outlet side in the cooler, and a circulation direction changing unit that changes a circulation direction of the cooling fluid flowing in the cooling circuit to switch an inlet side and an outlet side of the cooling fluid in the cooler, according to the deterioration state of the end portion battery estimated by the deterioration estimation unit.

Description

Technical Field

[0001] This invention relates to a battery cooling system. Background Technology

[0002] Patent document 1 discloses a cooling system for a battery pack, which introduces coolant into a sealed space containing the battery pack via a circulation channel.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2003-346924 Summary of the Invention

[0004] However, in the cooling system described in Patent Document 1, there is a temperature difference between the coolant on the cooling outlet side and the cooling inlet side, which causes degradation deviations in multiple battery packs.

[0005] The present invention was made in view of the above-mentioned problems, and its object is to provide a battery cooling system that can reduce the degradation deviation of multiple batteries.

[0006] To address the aforementioned issues and achieve the objectives, the present invention relates to a battery cooling system comprising a cooling circuit for circulating cooling fluid, the cooling fluid being used to cool a plurality of batteries arranged along a first direction. The cooling circuit includes: a cooler extending along the first direction and disposed opposite the plurality of batteries, the cooling fluid flowing internally along the first direction to cool the plurality of batteries; a fluid delivery device for supplying the cooling fluid and circulating it in the cooling circuit; and a fluid cooling device for cooling the cooling fluid circulating in the cooling circuit. The battery cooling system further includes: a degradation estimation unit for estimating the degradation state of an end battery disposed at an end in the first direction and at the outlet side of the cooling fluid in the cooler; and a circulation direction changing unit for changing the circulation direction of the cooling fluid flowing in the cooling circuit based on the degradation state of the end battery estimated by the degradation estimation unit, thereby switching the inlet and outlet sides of the cooling fluid in the cooler.

[0007] Therefore, in the battery cooling system of the present invention, by changing the circulation direction of the cooling fluid flowing in the cooling circuit according to the degradation state of the end battery, the inlet and outlet sides of the cooling fluid in the cooler can be switched, thereby reducing the degradation deviation of multiple batteries.

[0008] Furthermore, the above can also be configured as follows: the outlet of the cooling fluid in the fluid cooling device, i.e., the fluid outlet, is connected to the inlet of the cooling fluid in the liquid delivery device, i.e., the first port, through a first pipe; the first inlet / outlet of the cooling fluid in the liquid delivery device, i.e., the second port, is connected to the first inlet / outlet of the cooling fluid in the cooler, i.e., the first fluid inlet / outlet, is connected to the second inlet / outlet of the cooling fluid in the liquid delivery device, i.e., the third port, through a third pipe; the outlet of the cooling fluid in the liquid delivery device, i.e., the fourth port, is connected to the inlet of the cooling fluid in the fluid cooling device, i.e., the fluid inlet, through a fourth pipe; the flow path of the cooling fluid in the liquid delivery device is configured to selectively switch between a first flow path state connecting the first port and the second port and connecting the third port and the fourth port, and a second flow path state connecting the first port and the third port and connecting the second port and the fourth port; the circulation direction changing unit switches between the first flow path state and the second flow path state according to the deterioration state of the end battery.

[0009] Therefore, the circulation direction of the cooling fluid flowing in the cooling circuit can be changed to switch the inlet and outlet sides of the cooling fluid in the cooler without changing the direction of the cooling fluid flow between the fluid cooling device and the liquid delivery device, thereby preventing the circuit structure of the cooling circuit from becoming complicated.

[0010] Invention Effects

[0011] The battery cooling system of the present invention changes the circulation direction of the cooling fluid flowing in the cooling circuit according to the degradation state of the end battery, thereby switching the inlet and outlet sides of the cooling fluid in the cooler, thereby achieving the effect of reducing the degradation deviation of multiple batteries. Attached Figure Description

[0012] Figure 1 This is a diagram showing the general structure of the battery cooling system involved in the implementation method.

[0013] Figure 2 This is a diagram showing the battery cooling system when the liquid delivery device is in the second flow path state.

[0014] Figure 3 This is a graph illustrating an example of the relationship between the number of years of use and the capacity retention rate of battery packs 20a and 20h, which are end batteries in a battery pack. Detailed Implementation

[0015] The following describes embodiments of the battery cooling system according to the present invention. However, the present invention is not limited to these embodiments. The battery cooling system described in these embodiments is, for example, installed in a vehicle, and cools the secondary battery mounted in the vehicle by circulating coolant.

[0016] Figure 1 This is a diagram showing the schematic structure of the battery cooling system 1 according to the embodiment.

[0017] like Figure 1 As shown, the battery cooling system 1 according to the embodiment includes a cooling circuit 100 for circulating cooling fluid, which is cooling water, used to cool multiple battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h that are housed in a battery casing (not shown) of the battery pack 2 and stacked (arranged) along a stacking direction designated as a first direction. In this embodiment, without specifically distinguishing between the multiple battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h, they are also simply referred to as battery pack 20. Battery pack 20 is, for example, a rechargeable secondary battery such as a lithium-ion battery, and typically has a cuboid shape. Furthermore, the cooling fluid circulating in the cooling circuit 100 is not limited to a liquid such as cooling water; for example, it can be a gas such as a refrigerant gas.

[0018] Cooler 3, refrigerator 4, and liquid delivery device 6 are arranged in cooling circuit 100. Cooler 3 extends along the stacking direction of battery packs 20 and is arranged opposite to multiple battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h. Cooling water flows inside along the stacking direction of battery packs 20 to cool the multiple battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h. Refrigerator 4 is also connected to a refrigeration circulation loop (not shown) and is a fluid cooling device that cools the cooling water by exchanging heat between the refrigerant circulating in the refrigeration circulation loop and the cooling water circulating in the battery cooling system 1, causing the cooling water to release heat to the refrigerant. Liquid delivery device 6 delivers cooling water to circulate within cooling circuit 100.

[0019] In the cooling circuit 100, the cooler 3, the refrigerator 4, and the liquid delivery device 6 are connected via a first pipe 51, a second pipe 52, a third pipe 53, and a fourth pipe 54, respectively. Specifically, the outlet of the cooling water in the refrigerator 4, i.e., the fluid outlet 41, is connected to the inlet of the cooling water in the liquid delivery device 6, i.e., the first port 61, via the first pipe 51. Furthermore, the first inlet / outlet of the cooling water in the liquid delivery device 6, i.e., the second port 62, is connected to the first inlet / outlet of the cooling water in the cooler 3, i.e., the first fluid inlet / outlet 31, via the second pipe 52. Furthermore, the second inlet / outlet of the cooling water in the cooler 3, i.e., the second fluid inlet / outlet 32, is connected to the second inlet / outlet of the cooling water in the liquid delivery device 6, i.e., the third port 63, via the third pipe 53. Finally, the outlet of the cooling water in the liquid delivery device 6, i.e., the fourth port 64, is connected to the inlet of the cooling water in the refrigerator 4, i.e., the fluid inlet 42, via the fourth pipe 54. In the cooling circuit 100, cooling water circulates within the cooling circuit 100 by operating the liquid delivery device 6.

[0020] Furthermore, the flow path of the cooling water within the liquid delivery device 6 is configured to selectively switch between a first flow path state connecting the first port 61 and the second port 62, and connecting the third port 63 and the fourth port 64, and a second flow path state connecting the first port 61 and the third port 63, and connecting the second port 62 and the fourth port 64. The switching between the first and second flow path states in the liquid delivery device 6 is performed, for example, by operating a switching valve or similar device provided in the liquid delivery device 6, switching the flow paths within the liquid delivery device 6 that connect the first port 61, the second port 62, the third port 63, and the fourth port 64 respectively. The switching operation of the switching valve is performed, for example, using a drive device such as an actuator controlled by the control device 200.

[0021] Furthermore, the control device 200, for example, is an Electronic Control Unit (ECU) installed in a vehicle equipped with a battery cooling system 1, which acquires the charging capacity of each of the battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h at specified times using various sensors. Moreover, the control device 200 can, for example, calculate the capacity retention rate by dividing the charging capacity of each of the battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h after a period of use by the initial charging capacity. The capacity retention rate calculated by the control device 200 can be used to estimate the degradation state of each of the battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h. Thus, in the battery cooling system 1 according to the embodiment, the control device 200 also functions as a degradation state estimation unit for estimating the degradation state of the battery pack 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h. Furthermore, the control device 200, for example, as described later, in... Figure 1 In this case, it is sufficient to at least estimate the deterioration state of the end battery, i.e., the battery pack 20h, which is disposed at the end in the stacking direction of the battery pack 20 when the liquid delivery device 6 is in the first flow path state and the cooling water OUT side of the cooler 3 is in the first flow path state.

[0022] exist Figure 1 In the battery cooling system 1 shown, the liquid delivery device 6 is in the first flow path state. Figure 1 Arrow A1 in the diagram indicates the flow of cooling water from the fluid outlet 41 of the chiller 4, through the first piping 51, and via the first port 61 and second port 62 of the liquid delivery device 6, through the second piping 52, into the first fluid inlet / outlet 31 of the cooler 3. Furthermore, Figure 1 Arrow B1 indicates the flow of cooling water from the first fluid inlet / outlet 31 side to the second fluid inlet / outlet 32 ​​side within the cooler 3, in the stacking direction of the battery pack 20. Furthermore, Figure 1 Arrow C1 in the diagram indicates the flow of cooling water from the second fluid inlet / outlet 32 ​​of the cooler 3 through the third pipe 53 and through the third port 63 and the fourth port 64 of the liquid delivery device 6, and then through the fourth pipe 54 into the fluid inlet 42 of the refrigerator 4.

[0023] Thus, in Figure 1In the battery cooling system 1 with the liquid delivery device 6 in the first flow path state, in the stacking direction of the battery pack 20, the first fluid inlet / outlet 31 side of the cooler 3 becomes the cooling water IN side (cooling water inlet side) in the cooler 3, and the second fluid inlet / outlet 32 ​​side of the cooler 3 becomes the cooling water OUT side (cooling water outlet side) in the cooler 3. Moreover, in the battery cooling system 1 with the liquid delivery device 6 in the first flow path state, the cooling water cooled by the refrigerator 4 circulates in the cooling circuit 100, so as to flow in the cooler 3 from the battery pack 20a side to the battery pack 20h side in the stacking direction of the battery pack 20.

[0024] Here, as Figure 1 As shown, in the battery cooling system 1 supplied by the liquid delivery device 6 in the first flow path state, the end cells of the multiple battery groups 20 in the battery pack 2 constituting the cooling water OUT side of the cooler 3, namely the battery group 20h, are cooled by the cooling water heated by the cooling water that is cooled by the other battery groups 20a, 20b, 20c, 20d, 20e, 20f, and 20g. Therefore, the cooling effect of the battery group 20h based on the cooling water is lower than that of the other battery groups 20a, 20b, 20c, 20d, 20e, 20f, and 20g, and it always has the highest temperature among all battery groups 20, and is the most degraded among all battery groups 20, thereby limiting the performance of the battery pack 2.

[0025] Figure 2 This is a diagram showing the battery cooling system 1 when the liquid delivery device 6 is in the second flow path state.

[0026] In the battery cooling system 1 described in the embodiment, when the control device 200 estimates (determines) that the battery pack has deteriorated to a preset deterioration state after 20 hours, the control device 200 controls the actuator or other drive device to operate the switching valve in the liquid delivery device 6, such as... Figure 2 As shown, the liquid delivery device 6 is switched to the second flow path state. Therefore, in the battery cooling system 1 according to the embodiment, the circulation direction of the cooling water flowing in the cooling circuit 100 is changed so that the first fluid inlet / outlet 31 of the cooler 3 becomes the cooling water OUT side and the second fluid inlet / outlet 32 ​​becomes the cooling water IN side. Furthermore, at this time, the circulation direction of the cooling water flowing in the cooling circuit 100 can be changed to switch the cooling water IN side and the cooling water OUT side in the cooler 3 without changing the direction of the cooling water flow between the refrigerator 4 and the liquid delivery device 6, thus preventing the circuit structure of the cooling circuit 100 from becoming complex.

[0027] Furthermore, in the battery cooling system 1 according to the embodiment, the circulation direction of the cooling water flowing in the cooling circuit 100 is changed according to the deterioration state of the end battery (e.g., battery pack 20h) estimated by the control device 200. The unit for changing the circulation direction of the cooling water IN side and the cooling water OUT side in the cooler 3 is composed of, for example, the control device 200, the drive device and the switching valve.

[0028] Figure 2 Arrow A2 indicates the flow of cooling water from the fluid outlet 41 of the refrigerator 4 through the first port 61 and the third port 63 of the liquid delivery device 6 into the second fluid inlet 32 ​​of the cooler 3 when the liquid delivery device 6 is in the second flow path state. Furthermore, Figure 2 Arrow B2 indicates the flow of cooling water from the second fluid inlet / outlet 32 ​​side of the cooler 3 towards the first fluid inlet / outlet 31 side in the stacking direction of the battery pack 20 when the liquid delivery device 6 is in the second flow path state. Furthermore, Figure 2 Arrow C2 indicates that when the liquid delivery device 6 is in the second flow path state, the cooling water flowing out from the first fluid inlet 31 of the cooler 3 flows through the second port 62 and the fourth port 64 of the liquid delivery device 6 and flows into the fluid inlet 42 of the refrigerator 4.

[0029] Thus, in Figure 2 In the battery cooling system 1 with the liquid delivery device 6 in the second flow path state, in the stacking direction of the battery pack 20, the second fluid inlet / outlet 32 ​​side of the cooler 3 becomes the cooling water IN side of the cooler 3, and the first fluid inlet / outlet 31 side of the cooler 3 becomes the cooling water OUT side of the cooler 3. Moreover, in the battery cooling system 1 with the liquid delivery device 6 in the second flow path state, the cooling water cooled by the refrigerator 4 circulates in the cooling circuit 100, so as to flow in the cooler 3 from the battery pack 20h side to the battery pack 20a side in the stacking direction of the battery pack 20.

[0030] Therefore, battery pack 20h is cooled to its coldest state by cooling water cooled by the refrigeration unit 4, while battery pack 20a is cooled to its hottest state by cooling water heated by the refrigeration unit 4. Thus, compared to the case where the circulation direction of the cooling water flowing within the cooler 3 is not switched, battery pack 20a deteriorates faster over time, while battery pack 20h deteriorates slower, reducing the deterioration deviation among the multiple battery packs 20a, 20b, 20c, 20d, 20e, 20f, 20g, and 20h, thereby improving the lifespan of battery pack 2.

[0031] Figure 3 This is a graph showing an example of the relationship between the number of years of use and the capacity retention rate of the end cells of the battery packs 20a and 20h, which are the end cells of the multiple battery packs 20 constituting the battery pack 2.

[0032] The capacity retention rate of battery packs 20a and 20h is obtained by the control device 200 at a specified time by acquiring the charging capacity of battery packs 20a and 20h. The control device 200 calculates this by dividing the charging capacity of each battery pack 20a and 20h for each number of years of use by the initial charging capacity.

[0033] in addition, Figure 3 The solid line L1 in the graph represents the change in the capacity retention rate of the battery pack 20a over time when the circulation direction of the cooling water flowing in the cooler 3 is switched. Figure 3 The dashed line L2 in the graph represents the change in the capacity retention rate of the battery pack over 20 hours when the circulation direction of the cooling water flowing in the cooler 3 is switched. Figure 3 The single-dotted line L3 in the graph represents the change in the capacity retention rate of the battery pack 20a over time without changing the circulation direction of the cooling water flowing in the cooler 3. Figure 3 The double-dotted line L4 in the graph represents the change in the capacity retention rate of the battery pack over 20 hours without changing the circulation direction of the cooling water flowing in the cooler 3.

[0034] First, in the battery cooling system 1 according to the embodiment, the liquid delivery device 6 delivers liquid in a first flow path state, and the first fluid inlet / outlet 31 of the cooler 3 becomes the cooling water IN side and the second fluid inlet / outlet 32 ​​becomes the cooling water OUT side, so that the cooling water circulates in the cooling circuit 100 (cooler 3). Then, in the battery cooling system 1 according to the embodiment, as... Figure 3 As shown, after a period of use, if the capacity retention rate of the battery pack reaches the set value X1 after 20 hours, the liquid delivery device 6 is switched to the second flow path state, changing the circulation direction of the cooling water flowing in the cooling circuit 100, thereby switching the cooling water IN side and cooling water OUT side in the cooler 3. Thus, after a period of use following the change in circulation direction, if... Figure 3 As shown, the decrease in capacity retention is less when the temperature of the battery pack decreases after 20 hours, while the decrease in capacity retention is more significant when the temperature of the battery pack increases after 20 years. Furthermore, as... Figure 3 As shown, if the capacity retention rate of battery pack 20a reaches the set value X2 (< set value X1), the liquid delivery device 6 is switched to the first flow path state, changing the circulation direction of the cooling water flowing in the cooling circuit 100, thereby switching the cooling water IN side and cooling water OUT side in the cooler 3. Thus, after the circulation direction is changed again, during subsequent use, such as... Figure 3 As shown, when the temperature of battery pack 20a decreases, the decrease in capacity retention rate decreases; when the temperature of battery pack 20h increases, the decrease in capacity retention rate increases.

[0035] Thus, in the battery cooling system 1 according to the embodiment, by repeatedly switching the cooling water IN side and the cooling water OUT side in the cooler 3, the capacity retention rate of the battery packs 20a and 20h, which are end batteries, and each battery pack 20 constituting the battery pack 2 is reduced approximately uniformly (charging capacity deterioration), thereby extending the life of the battery pack 2.

[0036] Furthermore, in the battery cooling system 1 according to the embodiment, the circulation direction of the cooling water flowing in the cooling circuit 100 is changed at least once during the long-term use of the battery pack 2 (cell 20) to switch between the cooling water IN side and the cooling water OUT side in the cooler 3. In the battery cooling system 1 according to the embodiment, the circulation direction can also be changed based on the number of years of use of the battery pack 2 (cell 20) (e.g., every year). In the battery cooling system 1 according to the embodiment, the circulation direction can also be changed when the temperature of the end battery (e.g., cell 20h) on the cooling water OUT side is measured at least by a temperature sensor or the like, the temperature and time are recorded, and a preset threshold (e.g., 2400 hours for 25°C or higher) is reached. Furthermore, in the battery cooling system 1 according to the embodiment, if it is not possible to measure the temperature of each cell 20 by a temperature sensor or the like, the circulation direction can be changed based on a temperature sensor that measures the internal temperature of the battery pack 2, so as to cool the side of the battery pack 2 with the highest temperature.

[0037] Furthermore, the battery cooling system 1 described in this embodiment is not limited to battery packs 2 with multiple battery cells 20 stacked together; for example, it can also be applied to battery packs with multiple battery cells stacked in a predetermined stacking direction. That is, the cooling water in the cooler is switched between the cooling water in the IN side and the cooling water in the OUT side of the cooler, based on the deterioration state of the end battery cell disposed at the end in the stacking direction and disposed in the cooler extending along the stacking direction. This reduces the deterioration deviation of the multiple battery cells and improves the lifespan of the battery pack.

[0038] Symbol Explanation

[0039] 1-Battery cooling system, 2-Battery pack, 3-Cooler, 4-Refrigeration unit, 6-Liquid delivery device, 20, 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h-Battery groups, 31-First fluid inlet / outlet, 32-Second fluid inlet / outlet, 41-Fluid outlet, 42-Fluid inlet, 51-First piping, 52-Second piping, 53-Third piping, 54-Fourth piping, 61-First port, 62-Second port, 63-Third port, 64-Fourth port, 100-Cooling circuit.

Claims

1. A battery cooling system comprising a cooling circuit for circulating cooling fluid, the cooling fluid being used to cool a plurality of batteries arranged along a first direction, characterized in that, The cooling circuit is equipped with: A cooler that extends along the first direction and is configured to be opposite the plurality of batteries, wherein cooling fluid flows inside along the first direction to cool the plurality of batteries; A liquid delivery device that delivers the cooling fluid and circulates the cooling fluid in the cooling circuit; and A fluid cooling device that cools the cooling fluid circulating in the cooling circuit. The battery cooling system includes: A degradation estimation unit estimates the degradation state of an end cell among the plurality of cells that is disposed at an end in the first direction and at the outlet side of the cooling fluid in the cooler; and The circulation direction changing unit changes the circulation direction of the cooling fluid flowing in the cooling circuit according to the degradation state of the end battery estimated by the degradation estimation unit, so as to switch the inlet side and outlet side of the cooling fluid in the cooler.

2. The battery cooling system according to claim 1, characterized in that, The outlet of the cooling fluid in the fluid cooling device, i.e., the fluid outlet, is connected to the inlet of the cooling fluid in the liquid delivery device, i.e., the first port, through a first pipe. The first inlet / outlet, i.e., the second port, of the cooling fluid in the liquid delivery device is connected to the first inlet / outlet, i.e., the first fluid inlet / outlet, of the cooling fluid in the cooler via a second pipe. The second inlet / outlet of the cooling fluid in the cooler, i.e., the second fluid inlet / outlet, is connected to the second inlet / outlet of the cooling fluid in the liquid delivery device, i.e., the third port, via a third pipe. The outlet of the cooling fluid in the liquid delivery device, i.e., the fourth port, is connected to the inlet of the cooling fluid in the fluid cooling device, i.e., the fluid inlet, through a fourth pipe. The flow path of the cooling fluid within the liquid delivery device is configured to selectively switch between a first flow path state connecting the first port and the second port, and connecting the third port and the fourth port, and a second flow path state connecting the first port and the third port, and connecting the second port and the fourth port. The circulation direction change unit switches between the first flow path state and the second flow path state according to the degradation state of the end battery.

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