Battery system

Abstract

A battery system capable of suppressing a decrease in availability of a battery pack in a case where equalization processing is performed on a plurality of battery packs connected in series. A battery ECU performs equalization processing in a battery cell group constituted by a plurality of battery cells of a battery pack and a plurality of battery cells of another battery pack, in a case where the battery packs are connected in series, and in a case where a difference in SOH between the battery packs is smaller than a threshold Th1 and a difference in SOC between the battery packs is smaller than a threshold Th2. The equalization processing in the battery cell group is performed in a high SOC range, in a case where the difference in SOH is equal to or larger than the threshold Th1 and the difference in SOC is smaller than a threshold Th3 in the high SOC range.

Description

Technical Field

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

[0002] Japanese Patent Publication No. 2024-507529 (Patent Document 1) discloses a system that performs equalization processing to equalize the state of charge (SOC) of multiple batteries connected in series.

[0003] Patent Document 1: Japanese Patent Publication No. 2024-507529 Summary of the Invention

[0004] In the system described in Patent Document 1 above, equalization processing is performed without considering the differences in the degradation state and the State of Charge (SOC) of each battery (battery pack). In this case, it is considered that the SOC is not properly equalized, resulting in a decrease in battery availability.

[0005] The present invention was made to solve the above-mentioned problems, and its object is to provide a battery system that can suppress the decline in battery pack availability when performing equalization processing on multiple battery packs connected in series.

[0006] One aspect of the present invention relates to a battery system that performs SOC equalization processing, comprising: a first battery pack including a plurality of first battery cells; a second battery pack including a plurality of second battery cells; and a control unit. At least one of the first battery pack and the second battery pack is replaceable. When the first battery pack and the second battery pack are connected in series, and when the magnitude of the SOH difference (the difference between the State of Health (SOH) of the first battery pack and the SOH of the second battery pack) is less than a first threshold, and the magnitude of the SOC difference (the difference between the State of Charge (SOC) of the first battery pack and the SOC of the second battery pack) is less than a second threshold, equalization processing is performed in a battery cell group consisting of a plurality of first battery cells and a plurality of second battery cells; when the magnitude of the SOH difference is greater than or equal to the first threshold, and the SOC difference is less than a third threshold in a high SOC range (i.e., a range higher than a predetermined threshold), equalization processing is performed in a battery cell group within the high SOC range.

[0007] In a battery system according to one aspect of the present invention, as described above, when the first battery pack and the second battery pack are connected in series, and when the SOH difference is less than a first threshold and the SOC difference is less than a second threshold, equalization processing is performed in the battery cell group. Furthermore, when the first battery pack and the second battery pack are connected in series, and when the SOH difference is greater than or equal to the first threshold and the SOC difference is less than a third threshold in the high SOC range, equalization processing is performed in the high SOC range. Therefore, by considering both the SOH difference and the SOC difference when performing equalization processing, the SOC can be appropriately equalized. As a result, the degradation of battery pack availability can be suppressed.

[0008] When the first and second battery packs are connected in series, and the SOH difference is greater than or equal to a first threshold, and the SOC difference is less than a third threshold within the high SOC range, the control unit performs a high SOC range equalization process. This ensures that the SOC of the battery pack with the smaller SOH is only one value higher than the SOC of the battery pack with the larger SOH, based on the SOH difference. This structure enables the equalization of the energy storage capacity of the first and second battery packs.

[0009] When the first and second battery packs are connected in series, and the SOH difference is greater than or equal to a first threshold, and the SOC difference is greater than or equal to a third threshold in the high SOC range, the control unit can individually perform equalization processing for multiple first battery cells and equalization processing for multiple second battery cells. This structure can suppress over-discharge or over-charge of battery cells in each of the first and second battery packs. Furthermore, it can prevent the execution of equalization processing between packs (within battery cell groups) when the SOC difference is large and equalization between packs is difficult.

[0010] When the first and second battery packs are connected in series, and the SOH difference is less than a first threshold while the SOC difference is greater than a second threshold, the control unit can individually perform equalization processing for multiple first battery cells and equalization processing for multiple second battery cells. This structure can suppress over-discharge or over-charge of battery cells in each of the first and second battery packs. Furthermore, it can prevent the execution of equalization processing between battery packs (within battery cell groups) when the SOC difference is large and equalization between battery packs is difficult.

[0011] The control unit can perform the following processing: determine whether the first battery pack and the second battery pack are connected in series; and if it is determined that the first battery pack and the second battery pack are not connected in series, perform equalization processing on multiple first battery cells and equalization processing on multiple second battery cells separately. With this structure, for example, when the first battery pack and the second battery pack are connected in parallel, equalization processing on the battery cell group can be prevented.

[0012] Invention Effects

[0013] According to the present invention, when equalization processing is performed on multiple battery packs connected in series, the decrease in battery pack availability can be suppressed. Attached Figure Description

[0014] Figure 1 This is a diagram showing the structure of a vehicle and a power station equipped with a battery system based on this embodiment.

[0015] Figure 2 This is a diagram showing the structure of the battery system based on this embodiment.

[0016] Figure 3 This is a diagram showing the structure of the battery module of each battery pack based on this embodiment.

[0017] Figure 4 This is a flowchart illustrating the control of the battery ECU of the battery system based on this embodiment. Detailed Implementation

[0018] The embodiments of the present invention will be described in detail with reference to the accompanying drawings. Identical or corresponding parts in the drawings are labeled with the same symbols, and their descriptions are not repeated.

[0019] Figure 1 This diagram shows a vehicle 110 equipped with the battery system 100 according to an embodiment of the present invention and a power station 200 for power transfer between the vehicle 110 and the power station. Alternatively, the battery system 100 may also be installed in an electrical device other than a vehicle (e.g., a stationary energy storage device).

[0020] The vehicle 110 includes a body 110a, an ECU 111, a charger 112, and a charging port 113.

[0021] Vehicle 110 is electrically connected to power station 200 via cable 201, enabling it to exchange (charge and discharge) power with power station 200. This exchange of power is performed when the plug 202 located at the end of cable 201 is connected to the charging port 113 of vehicle 110.

[0022] The vehicle 110 may be, for example, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a battery electric vehicle. Alternatively, the battery system 100 may be located in an electrical device outside the vehicle (e.g., a stationary energy storage device).

[0023] In the plugged-in vehicle 110, external charging (i.e., charging the battery system 100 using electricity from outside the vehicle) and external discharging (i.e., discharging the battery system 100 to the outside of the vehicle) are possible. Alternatively, the vehicle 110 may only be able to perform external charging. The charger 112 performs power conversion between the power station 200 and the battery system 100 during external charging and discharging. This power conversion is controlled by the ECU 111.

[0024] Figure 2 This diagram illustrates the structure of a battery system 100 according to an embodiment of the present invention. The battery system 100 includes two battery packs 10. Hereinafter, one of the two battery packs 10 will be referred to as battery pack 10A, and the other as battery pack 10B. Hereinafter, when simply referred to as "battery pack 10," it will be a feature common to both battery pack 10A and battery pack 10B. Furthermore, battery pack 10A and battery pack 10B are examples of the "first battery pack" and "second battery pack" of the present invention, respectively.

[0025] Battery packs 10A and 10B are both replaceable. For example, battery pack 10A in battery packs 10A and 10B, which are connected in series, can be replaced with another battery pack 10A. Battery pack 10B can also be replaced.

[0026] The battery pack 10 includes a battery electronic control unit (ECU) 1, a positive terminal 2, a negative terminal 3, a disconnect circuit 4, a current sensor 5, a disconnect circuit 6, a fuse 7, a battery module 8, and a voltage sensor 9. The battery module 8 includes multiple (in...) Figure 2 There are 7 battery cells 8a in the battery pack 10A. Multiple battery cells 8a are connected in series. Furthermore, the battery ECU1 of battery pack 10A and battery ECU1 of battery pack 10B are examples of the "control unit" of the present invention. Moreover, the multiple battery cells 8a of battery pack 10A are an example of the "first battery cell" of the present invention. The multiple battery cells 8a of battery pack 10B are an example of the "second battery cell" of the present invention.

[0027] Battery packs 10A and 10B are configured to be connected in series. Specifically, battery packs 10A and 10B are connected in series via an electrical connection between the negative terminal 3 of battery pack 10A and the positive terminal 2 of battery pack 10B. Battery packs 10A and 10B are mounted in vehicle 110 (… Figure 1 In the current state, the positive terminal 2 of battery pack 10A is connected to terminal 114 of vehicle 110, and the negative terminal 3 of battery pack 10B is connected to terminal 115 of vehicle 110. Alternatively, the circuit can be switched to a parallel connection between battery pack 10A and battery pack 10B.

[0028] The battery ECU1 includes a processor 1a, a memory 1b, and a communication unit 1c. The memory 1b is configured to store information. In addition to the program, the memory 1b also stores information used in the program (e.g., maps, formulas, and various parameters). In this embodiment, the processor 1a executes the program stored in the memory 1b to perform various processes based on the battery ECU1 (e.g., SOC equalization processing). However, these processes can be executed solely through hardware (electronic circuitry) without using software.

[0029] The communication unit 1c acquires information from various devices via Controller Area Network (CAN) communication. For example, the communication unit 1c acquires the detection values ​​from voltage sensor 9 and current sensor 5, respectively. Furthermore, the processor 1a sends control signals to cut-off circuits 4 and 6, etc., via the communication unit 1c.

[0030] The communication unit 1c of battery pack 10A and the communication unit 1c of battery pack 10B communicate with each other. As a result, information (e.g., SOC and SOH information) is exchanged between battery pack 10A and battery pack 10B.

[0031] In the battery pack 10, a series circuit 11 is formed in the following order: positive terminal 2, disconnect circuit 4, battery module 8, disconnect circuit 6, fuse 7, and negative terminal 3. A current sensor 5 detects the current flowing between the disconnect circuit 4 and the battery module 8 in the series circuit 11.

[0032] Alternatively, the battery ECU1 can also be powered by a power source (not shown) included in the battery pack 10.

[0033] Voltage sensor 9 detects the voltage values ​​of each of the multiple battery cells 8a.

[0034] The processor 1a acquires information about the voltage of each battery cell 8a detected by the voltage sensor 9 via the communication unit 1c. The processor 1a acquires information about the voltage value of each battery cell 8a on a unit time basis (e.g., 1 minute).

[0035] The processor 1a calculates (estimates) the State of Charge (SOC) of each battery cell 8a based on the acquired voltage values ​​of each battery cell 8a. Then, the processor 1a calculates the average SOC of the acquired battery cells 8a (hereinafter referred to as the average SOC). The processor 1a identifies the calculated average SOC as the SOC of the battery pack 10. Furthermore, the SOC calculation (estimation) method can use known methods.

[0036] Processor 1a estimates the state of harmonics (SOH) of battery module 8. For example, processor 1a can estimate the SOH based on the acquired voltage values ​​of each battery cell 8a. However, the method for estimating SOH is not limited to the example described above.

[0037] Figure 3 The diagram schematically shows multiple battery cells 8a of battery pack 10A and multiple battery cells 8a of battery pack 10B.

[0038] The battery module 8 has multiple switches 8b and multiple resistors 8c. Specifically, a series circuit consisting of one switch 8b and one resistor 8c connected in series is connected in parallel with each battery cell 8a.

[0039] The on / off state of each switch 8b is controlled by processor 1a ( Figure 2 Specifically, the processor 1a of battery pack 10A controls the switch 8b of battery pack 10A. The processor 1a of battery pack 10B controls the switch 8b of battery pack 10B.

[0040] When switch 8b is in the closed state, battery cell 8a connected in parallel with the closed switch 8b is discharged. As a result, the State of Charge (SOC) of battery cell 8a decreases. Processor 1a performs a leveling process (equalization process) to equalize the SOC of multiple battery cells 8a by switching the discharged battery cells 8a according to their respective SOCs. Furthermore, the method of leveling process is not limited to the example described above.

[0041] In this case, the equalization process was performed without considering the differences in State of Health (SOH) and State of Charge (SOC) of each battery pack. In this situation, the SOC was considered not properly equalized, leading to a decrease in battery availability.

[0042] Therefore, in this embodiment, a leveling process is performed that takes into account the difference in state of decay (SOH) and state of charge (SOC) of each battery pack 10. For details, please refer to [link / reference]. Figure 4 The flowchart is used for illustration.

[0043] (Control process)

[0044] Figure 4This is a flowchart illustrating the processing in the battery system 100 according to this embodiment. This control process is executed by the battery ECU1 (processor 1a) while the battery system 100 is mounted on the vehicle 110. Figure 4 The control flow shown can be executed at predetermined intervals (e.g., 10 minutes). Furthermore, the decision-making processes in steps S1 to S3 and S5 described later can also be performed by the battery ECU1 of at least one of battery packs 10A and 10B. In this embodiment, as an example, an example of the decision-making processes being performed by the battery ECU1 of battery pack 10A is described.

[0045] In step S1, the battery ECU1 determines whether battery pack 10A and battery pack 10B are connected in series. If it is determined that battery pack 10A and battery pack 10B are connected in series ("Yes" in S1), the process proceeds to step S2. If it is determined that battery pack 10A and battery pack 10B are not connected in series ("No" in S1), the process proceeds to step S7.

[0046] For example, the battery ECU1 can make the above determination based on the change in the detected value of a voltage sensor (not shown). The placement of the voltage sensor is not limited. For example, the voltage sensor can detect the voltage of the series circuit 11 of battery pack 10A or battery pack 10B. Furthermore, the battery ECU1 can make the above determination based on the detected value of the current sensor 5 of battery pack 10A or battery pack 10B. Alternatively, the determination process in step S1 can be omitted.

[0047] In step S2, the battery ECU1 determines whether the absolute value of the difference between the State of Health (SOH) of battery pack 10A and the State of Health (SOH) of battery pack 10B (hereinafter referred to as the SOH difference) is less than a threshold Th1 (e.g., 10%). Specifically, the battery ECU1 of battery pack 10A makes the above determination based on the SOH information of battery module 8 of battery pack 10A and the SOH information of battery module 8 of battery pack 10B obtained from battery pack 10B. If the SOH difference is less than the threshold Th1 ("Yes" in S2), the process proceeds to step S3. If the SOH difference is greater than or equal to the threshold Th1 ("No" in S2), the process proceeds to step S5. Furthermore, the threshold Th1 is an example of the "first threshold" of the present invention.

[0048] In step S3, the battery ECU1 determines whether the absolute value of the difference between the SOC of battery pack 10A and the SOC of battery pack 10B (hereinafter referred to as the SOC difference) is less than a threshold Th2 (e.g., 10%). Specifically, the battery ECU1 of battery pack 10A makes this determination based on the SOC (the aforementioned average SOC) information of battery module 8 of battery pack 10A and the SOC (the aforementioned average SOC) information of battery module 8 of battery pack 10B obtained from battery pack 10B. If the SOC difference is less than the threshold Th2 ("Yes" in S3), the process proceeds to step S4. If the SOC difference is greater than or equal to the threshold Th2 ("No" in S3), the process proceeds to step S7. Furthermore, the threshold Th2 is an example of the "second threshold" of the present invention.

[0049] In step S4, the battery ECU1 of battery pack 10A and the battery ECU1 of battery pack 10B cooperate to perform equalization processing in a plurality of battery cells 8a (hereinafter referred to as a battery cell group), which consists of a plurality of battery cells 8a of battery pack 10A and a plurality of battery cells 8a of battery pack 10B. Specifically, each battery ECU1 controls the on / off state of each switch 8b so that the SOC of all battery cells 8a in the battery cell group becomes the SOC of the battery cell 8a with the lowest SOC in the battery cell group. In addition, the equalization processing in step S4 is performed independently of the SOC of battery pack 10 (i.e., across the entire SOC range). Then, the processing ends.

[0050] In step S5, the battery ECU1 determines whether the magnitude of the SOC difference within the high SOC range (i.e., the range higher than a predetermined threshold (e.g., 80%)) is less than the threshold Th3 (e.g., 10%). In other words, the battery ECU1 determines whether the SOC of each battery pack 10 is within the high SOC range and whether the magnitude of the SOC difference is less than the threshold Th3. If the magnitude of the SOC difference within the high SOC range is less than the threshold Th3 ("Yes" in S5), the process proceeds to step S6. If the magnitude of the SOC difference within the high SOC range is greater than or equal to the threshold Th3 ("No" in S5), the process proceeds to step S7. Furthermore, the threshold Th3 is an example of the "third threshold" of the present invention.

[0051] Additionally, thresholds Th2 and Th3 can be set to values ​​based on the electrical force that can be discharged through equalization processing (setting switch 8b to the closed state). For example, thresholds Th2 and Th3 can be equal to the values ​​converted from the electrical force that can be discharged through equalization processing to the state of charge (SOC).

[0052] In step S6, within the high SOC range, the battery ECU1 of battery pack 10A and the battery ECU1 of battery pack 10B cooperate to perform equalization processing in the battery cell group. Furthermore, unlike the case where equalization processing is performed by discharging from battery cell 8a as in this embodiment, in the case where equalization processing is performed by charging battery cell 8a, the equalization processing in step S6 can be performed after the SOC of each battery pack 10 has reached a near-full charge (e.g., a range where the SOC is 95% or higher) within the high SOC range.

[0053] Here, in the equalization process of step S6, the battery ECU1 makes the SOC (hereinafter referred to as the first SOC) of the battery pack 10A and the battery pack 10B with the smaller SOH greater than the SOC (hereinafter referred to as the second SOC) of the battery pack 10A and the battery pack 10B with the larger SOH.

[0054] Specifically, the battery ECU1 sets the difference between the first SOC and the second SOC as a value based on the SOH difference. More specifically, the battery ECU1 adjusts the SOC of each battery pack 10 so that the product of the SOH of the battery pack 10A and battery pack 10B with the first SOC is equal to the product of the SOH of the battery pack 10A and battery pack 10B with the second SOC. Alternatively, the first SOC can be made equal to the second SOC.

[0055] In step S7, the battery ECU1 of battery pack 10A performs equalization processing on each battery cell 8a of battery pack 10A, and the battery ECU1 of battery pack 10B performs equalization processing on each battery cell 8a of battery pack 10B. Furthermore, the equalization processing in step S7 is performed independently of the state of charge (SOC) of battery pack 10 (i.e., across the entire SOC range). Then, the processing ends.

[0056] As described above, in this embodiment, when battery pack 10A and battery pack 10B are connected in series, and the SOH difference is less than threshold Th1 and the SOC difference is less than threshold Th2, equalization processing is performed in the battery cell group. Thus, by performing equalization processing considering both the SOH and SOC differences, the SOC can be appropriately equalized. As a result, the decrease in the availability of battery pack 10 can be suppressed. Furthermore, by performing equalization processing under the condition that the SOH and SOC differences are relatively small, differences in charge storage capacity between battery packs 10 are suppressed. Therefore, the performance of each battery pack 10 can be fully utilized.

[0057] Furthermore, when battery packs 10A and 10B are connected in series, and when the SOH difference is greater than or equal to threshold Th1, and the SOC difference is less than threshold Th3 within the high SOC range, equalization processing is performed within the battery cell group within the high SOC range. Therefore, by performing equalization processing considering both the SOH and SOC differences, the SOC can be appropriately equalized. As a result, the performance of the battery pack 10 with at least a smaller SOH can be fully utilized. Moreover, by performing equalization within the high SOC range, the occurrence of over-discharge can be detected more reliably.

[0058] (Modified example)

[0059] In the above embodiment, an example is shown where equalization processing is performed individually for each battery pack 10 in step S7, but the present invention is not limited thereto. Equalization processing may also be omitted in step S7.

[0060] In the above embodiment, an example of having two battery packs 10 in the battery system 100 is shown, but the present invention is not limited thereto. The battery system may also have three or more battery packs 10. In this case, the SOH difference can be the difference between the maximum and minimum SOH values ​​of each of the multiple battery packs 10. Furthermore, the SOC difference can be the difference between the maximum and minimum SOC values ​​of each of the multiple battery packs 10.

[0061] In the above embodiments, an example of performing equalization processing on a per-cell basis is shown when the battery packs 10 are not connected in series with each other, but the present invention is not limited thereto. When the battery packs 10 are not connected in series with each other, equalization processing may not be performed.

[0062] In the above embodiments, it is shown that Figure 4 The control flow shown is an example executed while the battery system 100 is mounted on the vehicle 110, but the invention is not limited thereto. The control flow described above can also be executed while the battery system 100 is removed from the vehicle 110 (during separate placement).

[0063] The structures of the above-described embodiments and variations can be combined with each other.

[0064] Furthermore, the embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The scope of this invention is defined not by the description of the above embodiments but by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

[0065] Symbol Explanation

[0066] 1-Battery ECU (Control Unit), 8a-Battery Unit (First Battery Unit) (Second Battery Unit), 10A-Battery Pack (First Battery Pack), 10B-Battery Pack (Second Battery Pack), 100-Battery System.

Claims

1. A battery system that performs SOC equalization processing, the battery system being characterized by comprising: The first battery pack includes multiple first battery cells; A second battery pack, comprising a plurality of second battery cells; and Control Department At least one of the first battery pack and the second battery pack is configured to be replaceable. The control unit is configured such that the first battery pack and the second battery pack are connected in series, and, When the SOH difference (the difference between the SOH of the first battery pack and the SOH of the second battery pack) is less than a first threshold, and the SOC difference (the difference between the SOC of the first battery pack and the SOC of the second battery pack) is less than a second threshold, the equalization process is performed in the battery cell group consisting of the plurality of first battery cells and the plurality of second battery cells. When the SOH difference is greater than or equal to the first threshold, and the SOC difference is less than the third threshold in the high SOC range (i.e., within the range of SOC higher than a predetermined threshold), the equalization process in the battery cell group is performed in the high SOC range.

2. The battery system according to claim 1, characterized in that, When the first battery pack and the second battery pack are connected in series, and when the SOH difference is greater than or equal to the first threshold and the SOC difference is less than the third threshold in the high SOC range, the control unit performs the equalization process in the high SOC range so that the SOC of the battery pack with the smaller SOH is increased only by the value based on the SOH difference compared to the SOC of the battery pack with the larger SOH.

3. The battery system according to claim 1 or 2, characterized in that, When the first battery pack and the second battery pack are connected in series, and when the SOH difference is greater than or equal to the first threshold, and the SOC difference is greater than or equal to the third threshold in the high SOC range, the control unit performs the equalization processing of the plurality of first battery cells and the equalization processing of the plurality of second battery cells separately.

4. The battery system according to claim 1 or 2, characterized in that, When the first battery pack and the second battery pack are connected in series, and when the magnitude of the SOH difference is less than the first threshold and the magnitude of the SOC difference is greater than the second threshold, the control unit performs the equalization processing of the plurality of first battery cells and the equalization processing of the plurality of second battery cells separately.

5. The battery system according to claim 1 or 2, characterized in that, The control unit performs the following processing: Determine whether the first battery pack and the second battery pack are connected in series; and If it is determined that the first battery pack and the second battery pack are not connected in series, the equalization process of the plurality of first battery cells and the equalization process of the plurality of second battery cells are performed separately.

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