Determination device involving multiple batteries, power storage system, determination method, and nonvolatile storage medium

Abstract

In one embodiment, a determination device for a plurality of batteries connected in series is provided. The determination device includes a processor. The processor is configured to determine degradation variations among the plurality of batteries based on first voltage data representing a maximum voltage among the voltages of the plurality of batteries measured during each of a plurality of charging or discharging periods of the plurality of batteries, and second voltage data representing a minimum voltage among the voltages of the plurality of batteries measured during each of a plurality of charging or discharging periods.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based upon and claims the benefit of priority from Japanese patent application No. 2020-149664, filed on September 7, 2020, and the entire contents are incorporated herein by reference. Technical Field

[0003] Embodiments of the present invention relate to a determination device, a power storage system, a determination method, and a nonvolatile storage medium regarding a plurality of batteries. Background Art

[0004] In recent years, storage batteries have been installed in battery-equipped devices such as large-scale storage batteries used in power systems, smartphones, vehicles, stationary power supplies, robots, and drones, forming power storage systems. These systems consist of multiple cells, such as lithium-ion batteries, that are electrically connected. Furthermore, battery diagnostic technologies have been developed to ensure safe maintenance and improve battery performance.

[0005] A known battery diagnostic technique is one that determines the degree of degradation of multiple batteries connected in series. This diagnostic technique calculates the internal resistance of each battery based on changes in its voltage during charging. Furthermore, the degree of degradation of each battery is determined based on its internal resistance.

[0006] In a configuration where batteries are connected in series as described above, it is necessary to appropriately determine the variation in degradation among the multiple batteries. Furthermore, even in a configuration where multiple batteries are connected in series, it is necessary to determine the variation in degradation among the multiple batteries without complicating the data acquisition structure and processing, for example by reducing the amount of data required for processing.

[0007] Prior art literature

[0008] Patent Literature

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-138750

[0010] [Patent Document 2] International Publication No. 2017 / 154112

[0011] [Patent Document 3] International Publication No. 2013 / 128811

[0012] [Patent Document 4] Japanese Patent Application Laid-Open No. 2018-147827 Summary of the Invention

[0013] An object of the present invention is to provide a determination device, a power storage system, a determination method, and a nonvolatile storage medium that can appropriately determine degradation variations among a plurality of batteries connected in series without complicating the structure and processing for acquiring data.

[0014] In one embodiment, a determination device for a plurality of batteries connected in series is provided. The determination device includes a processor. The processor is configured to determine degradation variations among the plurality of batteries based on first voltage data representing a maximum voltage among the voltages of the plurality of batteries measured during each of a plurality of charging or discharging periods of the plurality of batteries, and second voltage data representing a minimum voltage among the voltages of the plurality of batteries measured during each of a plurality of charging or discharging periods. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram illustrating an example of a power storage system according to one embodiment.

[0016] Figure 2 is a schematic diagram for illustrating a structural example of a battery string according to an embodiment.

[0017] Figure 3 Schematic diagram showing an example of voltage changes of each of a plurality of batteries when charging a battery string according to an embodiment.

[0018] Figure 4A The diagram is different from the diagram showing the change of each battery voltage when charging the battery string according to the embodiment. Figure 3 Schematic diagram of another example.

[0019] Figure 4B It is shown in Figure 4A Schematic diagram of first voltage data and second voltage data generated in an example.

[0020] Figure 5 This is a schematic diagram for explaining internal state parameters such as a first internal state parameter and a second internal state parameter that represent the internal state of a battery cell.

[0021] Figure 6 This is a schematic diagram illustrating an example of reference data serving as a basis for the relationship between degradation variations among a plurality of batteries and one or more determination items.

[0022] Figure 7 1 is a flowchart showing a determination process regarding a certain battery string executed by the determination device according to the embodiment. DETAILED DESCRIPTION

[0023] In one embodiment, a determination device for a plurality of batteries connected in series is provided. The determination device includes a processor. The processor is configured to determine degradation variations among the plurality of batteries based on first voltage data representing a maximum voltage among the voltages of the plurality of batteries measured during each of a plurality of charging or discharging periods of the plurality of batteries, and second voltage data representing a minimum voltage among the voltages of the plurality of batteries measured during each of a plurality of charging or discharging periods.

[0024] Hereinafter, embodiments will be described with reference to the accompanying drawings.

[0025] Figure 1 : is a schematic diagram showing an example of a power storage system according to an embodiment. Figure 1 As shown in FIG, a power storage system 1 includes a battery 2 and a determination device 3. The battery 2 is installed in, for example, a battery-mounted device. Examples of battery-mounted devices include large batteries used in power systems, smartphones, vehicles, stationary power supply equipment, robots, drones, and the like. Examples of vehicles that are battery-mounted devices include railway vehicles, electric buses, electric vehicles, plug-in hybrid vehicles, and electric bicycles.

[0026] Storage battery 2 includes at least one battery string 5. When multiple battery strings 5 ​​are provided in storage battery 2, the battery strings 5 ​​are electrically connected in parallel. Examples of battery strings 5 ​​include battery panels, assembled batteries, and battery packs. Each battery string 5 includes multiple cells 6, which are electrically connected in series within each battery string 5. Each cell 6 is a secondary battery such as a lithium-ion battery. Each cell 6 in each battery string 5 can be charged and discharged. In each battery string 5, each cell 6 is charged by power supplied from a power source. Furthermore, in each battery string 5, the power discharged by each cell 6 is supplied to a load. Typically, in a new power storage system, multiple cells 6 of the same type are used in each battery string 5. Therefore, when storage battery 2 is first used, the cells 6 in each battery string 5 have the same or substantially the same internal state. However, this does not apply to power storage systems that use recycled batteries, for example. The internal state of the cells 6 will be described later.

[0027] Figure 2 : is a schematic diagram for illustrating a structural example of a battery string according to an embodiment. Figure 2In the example of , in the battery string 5, a plurality of battery modules 7 are electrically connected in series. In addition, in each battery module 7, a plurality of batteries 6 are electrically connected in series. Therefore, in the battery string 5, a plurality of batteries 6 are electrically connected in series. Therefore, the battery string 5 is a series connection portion of a plurality of batteries 6. In one example, the number of series-connected batteries 6 in the battery string 5 is about several hundred. In addition, Figure 2 In the example of FIG. 1 , each battery 6 includes a plurality of unit cells 8. In each battery 6, the unit cells 8 are electrically connected in parallel. Specifically, Figure 2 In the example of FIG. 5 , each battery 6 is formed by a battery block in which unit cells 8 are connected in parallel. Figure 2 In one example, a plurality of cell blocks are electrically connected in series in the battery string 5. In another example, each battery 6 may be formed of one cell 8. In another example, a plurality of cells 8 may be connected in series in each battery 6. In another example, a series connection structure in which a plurality of cells 8 are connected in series and a parallel connection structure in which a plurality of cells 8 are connected in parallel may be formed in each battery 6.

[0028] In the power storage system 1, a measurement circuit 11 and a battery management unit (BMU) 12 are provided for each battery string 5. Therefore, in a battery-mounted device or the like equipped with storage batteries 2, the same number of measurement circuits 11 and battery management units 12 as the number of battery strings 5 ​​are provided. Each measurement circuit 11 detects and measures parameters related to the corresponding battery string 5 during charging or discharging of the corresponding battery string 5. In each measurement circuit 11, parameters are periodically detected and measured at a predetermined timing. Specifically, each measurement circuit 11 measures parameters related to the corresponding battery string 5 during each of a plurality of measurement periods. Therefore, each measurement circuit 11 measures parameters related to the corresponding battery string 5 multiple times during charging or discharging of the corresponding battery string 5. It should be noted that the period during which each measurement circuit 11 performs measurement during charging or discharging of the corresponding battery string 5 is defined as a "measurement period." Parameters related to the battery string 5 include the current flowing through the battery string 5 (i.e., the current flowing through each battery cell 6), the voltage of the entire battery string 5 (the voltage of the entire section of series-connected batteries 6), and the voltage of each battery cell 6 in the battery string 5. Therefore, the measurement circuit 11 includes an ammeter for measuring current and a voltmeter for measuring voltage. Furthermore, the measurement circuit 11 can measure the temperature of the battery string 5 or the temperature of each battery cell 6. In this case, the measurement circuit 11 includes a temperature sensor, etc., for measuring temperature. Each measurement circuit 11 can measure the above parameters related to the corresponding battery string 5 at the same time point in each of multiple measurement periods, or can measure the above parameters related to the corresponding battery string 5 at different time points in the same measurement period.

[0029] Each battery management unit 12 constitutes a processing device (computer) that manages the corresponding battery string 5, and includes a processor and a storage medium (non-temporary storage medium). The processor includes any one of a CPU (central processing unit), a GPU (graphics processing unit), an ASIC (application-specific integrated circuit), a microcomputer, an FPGA (field programmable gate array), and a DSP (digital signal processor), etc. In addition to a main storage device such as a memory, the storage medium may also include an auxiliary storage device. Examples of storage media include magnetic disks, optical disks (e.g., CD-ROM, CD-R, DVD), magneto-optical disks (e.g., MO), and semiconductor memories. In each battery management unit 12, each of the number of processors and the number of storage media can be one or more. In each battery management unit 12, the processor executes programs stored in a storage medium, etc., thereby performing processing. In addition, in each battery management unit 12, the program executed by the processor can be stored in a computer (server) connected via a network (e.g., the Internet), or in a server in a cloud environment, etc. In this case, the processor downloads the program via the network.

[0030] The determination device 3 can be set in the battery-mounted device equipped with the storage battery 2, or it can be set outside the battery-mounted device. The determination device 3 performs a determination process on each of the battery strings 5 ​​and includes a data acquisition unit 13, an internal state estimation unit 15, a determination unit 16, and a data storage unit 16. In one example, the determination device 3 is a server capable of communicating with each battery management unit 12 via a network. In this case, like each battery management unit 12, the determination device 3 includes a processor and a storage medium (non-temporary storage medium). In addition, the data acquisition unit 13, the internal state estimation unit 15, and the determination unit 16 perform a portion of the processing performed by the processor of the determination device 3, etc., and the storage medium of the determination device 3 acts as a data storage unit 17. In another example, the determination device 3 is a cloud server configured in a cloud environment. The infrastructure of the cloud environment is composed of virtual processors such as virtual CPUs and cloud storage. Therefore, when the determination device 3 is a cloud server, the data acquisition unit 13, the internal state estimation unit 15, and the determination unit 16 perform a portion of the processing performed by the virtual processor. In addition, the cloud storage acts as the data storage unit 17.

[0031] It should be noted that the data storage section 17 may be provided in a computer different from the battery management unit 12 and the determination device 3. In this case, the determination device 3 is connected to the computer provided with the data storage section 17 and the like via a network.

[0032] In the determination device 3, the processor performs determinations regarding the degree of degradation of each battery string 5 and the variation in degradation among the multiple batteries 6 in each battery string 5. In the storage battery 2 having the above-described structure, after a certain period of time has passed since the start of use, there is a possibility that the internal conditions of the multiple batteries 6 in each battery string 5 may vary. Variations in the internal conditions of the multiple batteries 6 within each battery string 5 also lead to variations in the degree of degradation among the batteries. By suppressing the variation in degradation among the batteries 6, it is possible to prevent the occurrence of batteries 6 that deteriorate more significantly than other batteries 6 and effectively prevent the occurrence of batteries 6 that are overloaded compared to other batteries 6. Consequently, rapid degradation of the battery string 5 is prevented, and performance degradation of the battery string 5 is prevented. Furthermore, by effectively preventing the occurrence of batteries 6 that are overloaded, accidents are effectively prevented compared to other batteries 6, ensuring safety. Therefore, in each battery string 5, it is important to appropriately determine the variation in degradation among the multiple batteries 6, in addition to the degree of degradation of the battery string 5. Hereinafter, a determination process related to a certain battery string 5, that is, a determination process related to a plurality of batteries 6 connected in series will be described. It should be noted that the determination process described below is similarly performed for the other battery strings 5.

[0033] When a battery string 5 is determined to be in a state of charge or discharge, the corresponding measurement circuit 11 measures the aforementioned parameters related to the battery string 5 (parameters related to the multiple batteries 6 connected in series). Furthermore, the corresponding battery management unit 12 acquires the measured values ​​of the parameters related to the battery string 5 from the measurement circuit 11. Thus, the battery management unit 12 acquires the current flowing in the battery string 5 (i.e., the current flowing in each battery 6), the voltage of the entire battery string 5 (the voltage of the entire section of batteries 6 connected in series), and the voltage of each battery 6 in the battery string 5. The battery management unit 12 periodically acquires the measured values ​​of the parameters related to the battery string 5 at predetermined timings. Specifically, the battery management unit 12 acquires the measured values ​​of the parameters related to the battery string 5 for each of multiple measurement periods. For example, the battery management unit 12 acquires the measured values ​​of the voltage of the battery 6 for each measurement period. Therefore, in addition to the measured values ​​of the parameters related to the battery string 5, the battery management unit 12 also acquires the temporal changes (time history) of the parameters related to the battery string 5 as measurement data. Therefore, the measurement data acquired by the battery management unit 12 includes the temporal variation (time history) of the current flowing through the battery string 5, the temporal variation (time history) of the voltage of the entire battery string 5, and the temporal variation (time history) of the voltage of each battery cell in the battery string 5. Furthermore, the measurement data may include the temporal variation of the temperature of the battery string 5 or the temporal variation of the temperature of each battery cell 6. It should be noted that each measurement circuit 11 may measure the voltages of the multiple batteries 6 in the battery string 5 at the same time point during each of the multiple measurement periods, or may measure the voltages of the multiple batteries 6 in the battery string 5 at different time points within the same measurement period.

[0034] In addition to acquiring the aforementioned measurement data, the battery management unit 12 can also acquire charging conditions or discharging conditions when measuring parameters related to the battery string 5. Charging conditions include the charging current value, the SOC (State of Charge) of the battery string 5 at the start and end of charging, and the temperature range of the battery string 5 during charging. Similarly, discharging conditions include the discharging current value, the SOC of the battery string 5 at the start and end of discharging, and the temperature range of the battery string 5 during discharging.

[0035] The battery management unit 12 can obtain, as measurement data, data indicating the relationship between the voltage of the battery string 5 and the charge (discharge) amount of the battery string 5 or the SOC of the battery string 5 from the start of charging (discharging). Furthermore, the battery management unit 12 can obtain, as measurement data, data indicating the relationship between the voltage of each battery cell 6 and the charge (discharge) amount of the battery string 5 or the SOC of the battery string 5 from the start of charging (discharging). The charge (discharge) amount of the battery string 5 from the start of charging (discharging) can be calculated by using the elapsed time from the start of charging (discharging) and the temporal change (time history) of the current flowing through the battery string 5 (batteries 6 of the battery string 5). Furthermore, in this embodiment, since the batteries 6 are connected in series within the battery string 5, the charge (discharge) amount of the battery string 5 from the start of charging (discharging) corresponds to the charge (discharge) amount of each battery cell 6 from the start of charging (discharging).

[0036] The SOC of the battery string 5 represents the ratio of the remaining capacity of the battery string 5 to the full charge capacity of the battery string 5 from the SOC reaching 0% to the SOC reaching 100%. The SOC of the battery string 5 can be calculated by using the measurement data described above and the charge / discharge history of the battery string 5, etc. Examples of methods for calculating the SOC of the battery string 5 include a current integration method, a calculation method using the relationship between the terminal voltage of the battery string 5 and the SOC, and an estimation method using a Kalman filter.

[0037] It should be noted that for each battery 6, the ratio of the remaining capacity to the fully charged capacity until the SOC reaches 0% is defined as the SOC. In each battery 6, the state in which the inter-terminal voltage (the voltage between the positive and negative terminals) has a voltage value Vα1 under a set discharge condition is defined as a state in which the SOC is 0%, and the state in which the inter-terminal voltage has a voltage value Vα2 greater than Vα1 under a set charge condition is defined as a state in which the SOC is 100%. Furthermore, if the number of series-connected batteries 6 in the battery string 5 is N, then the state in which the inter-terminal voltage in the battery string 5 is N × Vα1 is defined as a state in which the SOC of the battery string 5 is 0%, while the state in which the inter-terminal voltage is N × Vα2 is defined as a state in which the SOC of the battery string 5 is 100%. However, in the battery string 5, the state in which one of the N batteries 6 reaches Vα1 can be defined as a state in which the SOC is 0%, and the state in which one of the N batteries 6 reaches Vα2 can be defined as a state in which the SOC is 100%.

[0038] Furthermore, in this embodiment, the battery management unit 12 calculates first voltage data representing changes in the maximum voltage Vmax during charging or discharging of the battery string 5 based on the measurement data. This maximum voltage Vmax is the maximum voltage among the voltages of the batteries 6 in the battery string 5. As described above, during charging or discharging of the batteries 6 in the battery string 5, the voltages of the batteries 6 are periodically measured, and the battery management unit 12 obtains the measured voltage values ​​of the batteries 6 during each of a plurality of measurement periods (each measurement within a plurality of periods). A maximum voltage Vmax is defined for each measurement period (each measurement within a period), and the maximum voltage among the voltages of the batteries 6 in each measurement period is defined as the maximum voltage Vmax. Furthermore, data representing the maximum voltage Vmax during two or more measurement periods becomes the first voltage data. Therefore, data representing the maximum voltage Vmax, which is the highest among the voltages of the batteries 6 in each measurement period of charging or discharging of the battery string 5, becomes the first voltage data. Specifically, a set of maximum voltages Vmax during each measurement period constitutes first voltage data, and the first voltage data represents the largest maximum voltage Vmax among the voltages of the battery 6 in each measurement during or during charging of the battery string 5. The first voltage data may be data indicating temporal changes (time history) in the maximum voltage Vmax during charging or discharging, or data indicating the relationship between the maximum voltage Vmax and the charge (discharge) amount of the battery string 5 from the start of charging (discharging) or the SOC of the battery string 5.

[0039] Furthermore, the battery management unit 12 calculates second voltage data representing changes in the minimum voltage Vmin based on the measurement data. This minimum voltage Vmin is the minimum voltage among the voltages of the cells 6 in the battery string 5 during charging or discharging of the cells 6 in the battery string 5. Similar to the maximum voltage Vmax, the minimum voltage Vmin is defined for each measurement period (for each measurement within a period). The minimum voltage among the voltages of the cells 6 in each measurement period is defined as the minimum voltage Vmin. Furthermore, data representing the minimum voltage Vmin in two or more measurement periods constitutes the second voltage data. Therefore, data representing the minimum voltage Vmin among the voltages of the cells 6 in each measurement period of charging or discharging the battery string 5 constitutes the second voltage data. Specifically, a set of minimum voltages Vmin in each measurement period constitutes the second voltage data, and the second voltage data represents the minimum voltage Vmin among the voltages of the cells 6 in each measurement period of charging or discharging the battery string 5. The second voltage data may be data indicating a temporal change (time history) of the minimum voltage Vmin during charging or discharging, or may be data indicating a relationship between the minimum voltage Vmin and the charge amount (discharge amount) of the battery string 5 from the start of charging (start of discharging) or the SOC of the battery string 5.

[0040] Here, the first voltage data and the second voltage data will be described. The first voltage data and the second voltage data are generated based on at least the measurement results of the voltages of the plurality of batteries 6 by the measurement circuit 11. Figure 3 FIG is a schematic diagram showing an example of voltage changes of a plurality of batteries when a battery string is charged according to an embodiment. Figure 3 In the example of , the relationship between the voltage of each of the plurality of batteries 6 and the charge amount of the battery string 5 after the start of charging (the charge amount of the battery cell 6 after the start of charging) is shown. Figure 3 In the example of , the voltage of the battery 6 is measured periodically (multiple times) during the multiple periods from the start of charging (from the state where the charge amount is 0) to the time when the charge amount reaches Qa. Figure 3 The solid line shows the change in voltage Va of one battery 6a and the change in voltage Vb of another battery 6b. The dotted line shows the change in voltage of the batteries 6 other than batteries 6a and 6b.

[0041] exist Figure 3 In the example, in any partial range of 0 to Qa of the charge amount, the voltage Va of the battery 6a is the maximum voltage Vmax, which is the largest among the voltages of the battery 6. Therefore, in any partial range of 0 to Qa of the charge amount, that is, in any partial range of the charge amount in which the voltage of the battery 6 is measured, the data representing the change in the voltage Va of the battery 6a corresponds to the data representing the change in the maximum voltage Vmax. Therefore, the data representing the change in the voltage Va of the battery 6a during charging becomes the first voltage data representing the change in the maximum voltage Vmax during charging. In other words, the data representing the voltage Va of the battery 6a measured each time in multiple periods becomes the first voltage data representing the maximum voltage Vmax measured each time in multiple periods during charging. In addition, in Figure 3 In the example, within any portion of the charge range from 0 to Qa, the voltage Vb of battery 6b is the minimum voltage Vmin, which is the lowest among the voltages of battery 6. Therefore, within any portion of the charge range from 0 to Qa, that is, within any portion of the charge range during which the voltage of battery 6 is measured, the data representing the change in voltage Vb of battery 6b corresponds to the data representing the change in minimum voltage Vmin. Therefore, the data representing the change in voltage Vb of battery 6b during charging becomes the second voltage data representing the change in minimum voltage Vmin during charging. In other words, the data representing voltage Vb of battery 6b measured during each of the multiple periods becomes the second voltage data representing the minimum voltage Vmin measured during each of the multiple periods during charging.

[0042] Figure 4A The diagram is different from the diagram showing the change of each battery voltage when charging the battery string according to the embodiment. Figure 3Schematic diagram of another example. In Figure 4A In the example, the relationship between the voltage of the battery 6 and the charge amount of the battery string 5 (the charge amount of the battery cell 6 starting from the start of charging) is also shown. In addition, in Figure 4A In the example, from the start of charging (from the state where the charge amount is 0) until the charge amount reaches Qa, the voltage of the battery 6 is measured periodically (multiple times) in a plurality of periods. Figure 4A The changes in the voltage Va of the battery 6a and the voltage Vb of the battery 6b are represented by solid lines, and the change in the voltage Vc of the battery 6c is represented by a dotted line, where the battery 6c is different from the battery 6a and 6b of the battery 6. In addition, the voltage change of the battery 6 other than the battery 6a, 6b, and 6c is represented by a dashed line. In addition, Figure 4B is a schematic diagram for explaining the first voltage data and the second voltage data generated in the example of Figure 4A .

[0043] In Figure 4A In the example, the battery in the battery 6 that takes the maximum voltage Vmax is different at the boundary of the charge amount Qb (0 < Qb < Qa). Specifically, in the range from 0 to less than Qb of the charge amount, the voltage Va of the battery 6a is the maximum voltage Vmax, which is the maximum voltage among the voltages of the battery 6. In addition, in the range from Qb to Qa of the charge amount, the voltage Vc of the battery 6c is the maximum voltage Vmax. Therefore, in the range from 0 to less than Qb of the charge amount, the data representing the change in the voltage Va of the battery 6a corresponds to the data representing the change in the maximum voltage Vmax, and in the range from Qb to Qa of the charge amount, the data representing the change in the voltage Vc of the battery 6c corresponds to the data representing the change in the maximum voltage Vmax. Therefore, using the data representing the changes in the voltages Va and Vc of the batteries 6a and 6c during charging, the first voltage data representing the change in the maximum voltage Vmax during charging is generated, that is, the first voltage data representing the maximum voltage Vmax measured each time during multiple periods during charging. In this case, for example, data representing the relationship between the maximum voltage Vmax and the charge amount starting from the start of charging of the battery string 5 in Figure 4B is generated as the first voltage data.

[0044] In addition, in Figure 4AIn the example, the battery with the minimum voltage Vmin among the batteries 6 is different depending on the charge amount Qc (0 < Qc < Qb < Qa). Specifically, within the range of 0 to less than Qc of the charge amount, the voltage Vc of the battery 6c is the minimum voltage Vmin, which is the minimum among the voltages of the batteries 6. Further, within the range of Qc to Qa of the charge amount, the voltage Vb of the battery 6b is the minimum voltage Vmin. Therefore, within the range of 0 to less than Qc of the charge amount, the data representing the change in the voltage Vc of the battery 6c corresponds to the data representing the change in the minimum voltage Vmin, and within the range of Qc to Qa of the charge amount, the data representing the change in the voltage Vb of the battery 6b corresponds to the data representing the change in the minimum voltage Vmin. Thus, using the data representing the changes in the voltages Vb and Vc of the batteries 6b and 6c during charging, second voltage data representing the change in the minimum voltage Vmin during charging is generated, that is, second voltage data representing the minimum voltage Vmin measured each time during multiple periods during charging. In this case, for example, data representing the relationship between the minimum voltage Vmin and the charge amount starting from the start of charging of the battery string 5 in Figure 4B is generated as the second voltage data.

[0045] Further, when the battery module 7 is connected in series in the battery string 5 as shown in the example of Figure 2 , the management device, which is a slave device of the battery management unit 12, can set the number of module management units (not shown) to be the same as the number of battery modules 7 provided in the battery string 5. In this case, each module management unit constitutes a processing device (computer) for managing the corresponding battery module 7 of the battery string 5 and includes a processor and a storage medium (similar to the battery management unit 12). Further, in one example, the number of measurement circuits ¹¹ can be set to be the same as the number of battery modules 7 provided in the battery string 5. In this case, each measurement circuit 11 detects and measures parameters related to the corresponding battery module 7 during charging or discharging of the corresponding battery module 7.

[0046] Each module management unit may also acquire the measured voltage values ​​of the cells 6 provided in the corresponding battery module 7. In this case, each module management unit calculates provisional maximum voltage data indicating the maximum voltage change among the cells 6 of the corresponding battery module 7 during charging or discharging of the battery string 5 based on the acquired measured values. Furthermore, each module management unit calculates provisional minimum voltage data indicating the minimum voltage change among the cells 6 of the corresponding battery module 7 during charging or discharging of the battery string 5 based on the acquired measured values. Furthermore, each module management unit outputs the provisional maximum voltage data and provisional minimum voltage data to the battery management unit 12. The battery management unit 12 then generates the aforementioned first voltage data based on the provisional maximum voltage data output from each module management unit, and generates the aforementioned second voltage data based on the provisional minimum voltage data output from each module management unit.

[0047] The battery management unit 12 outputs data indicating changes in the current flowing through the battery string 5 during charging or discharging of the battery string 5 to the determination device 3. Furthermore, the battery management unit 12 outputs the aforementioned first and second voltage data to the determination device 3. Furthermore, the battery management unit 12 outputs (transmits) third voltage data indicating changes in the voltage of the entire battery string 5 during charging or discharging of the battery string 5 (the voltage of the entire series-connected portion of the battery cells 6) to the determination device 3. The third voltage data is included in the aforementioned measurement data and indicates the voltage of the entire battery string 5 during each of a plurality of measurement periods during charging or discharging of the battery string 5. Furthermore, the third voltage data may be data indicating changes in the voltage of the battery string 5 over time (a time history) during charging or discharging, or data indicating the relationship between the voltage of the battery string 5 and the amount of charge (discharge) of the battery string 5 from the start of charging (discharging) or the state of charge (SOC) of the battery string 5.

[0048] It should be noted that the battery management unit 12 may also output data other than the third voltage data included in the measured data to the determination device 3. In one example, in addition to the first, second, and third voltage data described above, data indicating the temperature change of the battery string 5 during the charging or discharging process of the battery string 5, or data indicating the temperature change of each battery cell 6 during the charging or discharging process of the battery string 5, may also be output to the determination device 3. Furthermore, the battery management unit 12 may output the charging or discharging conditions when measuring parameters related to the battery string 5 to the determination device 3.

[0049] The data acquisition unit 13 of the determination device 3 receives and acquires data output from the battery management unit 12. Therefore, the data acquisition unit 13 acquires at least first voltage data, second voltage data, and third voltage data. The data acquisition unit 13 also receives information such as charging conditions or discharging conditions when measuring parameters related to the battery string 5. It should be noted that in the embodiment described above, the battery management unit 12, etc., generates the first voltage data and the second voltage data. However, the data acquisition unit 13 of the determination device 3 may also generate the first voltage data and the second voltage data. In this case, the data acquisition unit 13 acquires the measured values ​​of the parameters related to the battery string 5 and the aforementioned measured data from the battery management unit 12, etc. The data acquisition unit 13 then generates the first voltage data and the second voltage data based on the measured values ​​of the parameters related to the battery string 5 and the measured data.

[0050] The internal state estimation unit 15 performs processing by using the first voltage data, the second voltage data, and the third voltage data acquired by the data acquisition unit 13. The internal state estimation unit 15 estimates a first internal state parameter based on the first voltage data and the like. The first internal state parameter is a parameter that represents the internal state of the battery cell 6 when the voltage changes as the first voltage data during charging or discharging. Specifically, the first internal state parameter represents the internal state of the battery cell 6 when the voltage in each measurement in a plurality of periods becomes the same as the maximum voltage Vmax of the first voltage data. Therefore, by estimating the first internal state parameter, the internal state of the battery cell 6 when the voltage changes as the maximum voltage Vmax during charging or discharging is estimated. In one example, the internal state estimation unit 15 estimates the first internal state parameter by performing charging curve analysis (discharging curve analysis), for example, by analyzing the first voltage data representing the change in the maximum voltage Vmax during charging (discharging), and data representing the change in the current flowing in the battery string 5 during charging (discharging). It should be noted that in Figure 3 In the example, the internal state of the battery 6a is estimated basically by estimating the first internal state parameter. Figure 4A and Figure 4B In the example of , by estimating the first internal state parameter, a virtual internal state of the battery in which the voltage changes as the maximum voltage Vmax during charging is estimated.

[0051] In addition, the internal state estimation unit 15 estimates a second internal state parameter based on the second voltage data, etc. The second internal state parameter is a parameter that represents the internal state of the battery cell 6 when the voltage changes as the second voltage data during charging or discharging. Specifically, the second internal state parameter represents the internal state of the battery cell 6 when the voltage in each measurement in a plurality of periods becomes the same as the minimum voltage Vmin of the second voltage data. Therefore, by estimating the second internal state parameter, the internal state of the battery cell 6 when the voltage changes as the minimum voltage Vmin during charging or discharging is estimated. In one example, the internal state estimation unit 15 estimates the second internal state parameter by performing charging curve analysis (discharging curve analysis), for example, by analyzing the second voltage data representing the change in the minimum voltage Vmin during charging (discharging), and data representing the change in the current flowing in the battery string 5 during charging (discharging). It should be noted that in Figure 3 In the example, the internal state of the battery 6b is estimated basically by estimating the second internal state parameter. Figure 4A and Figure 4B In the example of , by estimating the second internal state parameter, a virtual internal state of the battery in which the voltage changes as the minimum voltage Vmin during charging is estimated.

[0052] Furthermore, the internal state estimator 15 estimates a third internal state parameter based on the third voltage data and the like. The third internal state parameter is a parameter representing the internal state of the battery string 5, that is, a parameter representing the internal state of the entire series-connected battery cell 6. Therefore, by estimating the third internal state parameter, the internal state of the battery string 5 is estimated. In one example, the internal state estimator 15 estimates the third internal state parameter by performing charge curve analysis (discharge curve analysis), for example, by analyzing the third voltage data representing changes in the voltage of the entire battery string 5 (the voltage of the entire series-connected battery cell 6) during charge (discharge), and data representing changes in the current flowing in the battery string 5 during charge (discharge).

[0053] Here, each of the first to third internal state parameters described above includes, for example, any one of the positive electrode capacity (or positive electrode mass), the negative electrode capacity (or positive electrode mass), the initial charge capacity of the positive electrode, the initial charge capacity of the negative electrode, and the internal resistance. Furthermore, each of the first to third internal state parameters may include an offset between the initial charge capacity of the positive electrode and the initial charge capacity of the negative electrode, i.e., a shift of the operation window (SOW). However, it should be noted that the first and second internal state parameters are internal state parameters associated with the battery cell 6, while the third internal state parameter is an internal state parameter associated with the entire battery string 5 (the entirety of the series-connected portion).

[0054] Figure 5 Schematic diagram for explaining the first internal state parameter and the second internal state parameter, etc., which represent the internal state of the battery cell. Figure 5 As shown in , in battery 6 and the like, the amount of charge until the positive electrode reaches the upper limit charge amount from the initial charge amount is the positive electrode capacity. Furthermore, the amount of charge at the positive electrode when the positive electrode potential (the potential of the positive terminal) reaches Vβ1 is defined as the initial charge amount, and the amount of charge at the positive electrode when the positive electrode potential reaches Vβ2, which is higher than Vβ1, is defined as the upper limit charge amount. Furthermore, in battery 6 and the like, the amount of charge until the negative electrode reaches the upper limit charge amount from the initial charge amount is the negative electrode capacity. Furthermore, the amount of charge at the negative electrode when the negative electrode potential (the potential of the negative terminal) reaches Vγ1 is defined as the initial charge amount, and the amount of charge at the negative electrode when the negative electrode potential reaches Vγ2, which is lower than Vγ1, is defined as the upper limit charge amount.

[0055] Furthermore, when the battery string 5 is considered a single battery, similarly to the battery cells 6, the positive electrode capacity is defined as the charge capacity until the positive electrode reaches the upper limit charge capacity from the initial charge capacity, and the negative electrode capacity is defined as the charge capacity until the negative electrode reaches the upper limit charge capacity from the initial charge capacity. However, it should be noted that, if the number of series-connected batteries 6 in the battery string 5 is N, the positive electrode charge capacity when the positive electrode potential (the potential of the positive electrode terminal) reaches N × Vβ1 is defined as the initial charge capacity, and the positive electrode charge capacity when the positive electrode potential reaches N × Vβ2 is defined as the upper limit charge capacity. Furthermore, the negative electrode charge capacity when the negative electrode potential (the potential of the negative electrode terminal) reaches N × Vγ1 is defined as the initial charge capacity, and the negative electrode charge capacity when the negative electrode potential reaches N × Vγ2 is defined as the upper limit charge capacity. Furthermore, the positive electrode mass can be estimated based on the estimated positive electrode capacity and the type of material constituting the positive electrode. Similarly, the negative electrode mass can be estimated based on the estimated negative electrode capacity and the type of material forming the negative electrode.

[0056] If the battery string 5 and each of the multiple batteries 6 degrade due to repeated charge and discharge, the positive electrode capacity and negative electrode capacity described above will decrease compared to the initial use. Furthermore, if degradation occurs in the battery string 5 (the series connection) and each of the multiple batteries 6, the SOW described above will change compared to the initial use. Furthermore, if the degradation variation among the multiple batteries 6 in the battery string 5 increases, the variation in internal state parameters such as the positive electrode capacity, negative electrode capacity, and SOW among the multiple batteries 6 will also increase.

[0057] It should be noted that in each of the battery string 5 and the battery cell 6, the battery capacity is defined as a battery characteristic parameter indicating the battery characteristics. The battery capacity is equivalent to the charge amount required for the difference between the positive electrode potential and the negative electrode potential to reach Vα2 from Vα1 (refer to Figure 5 ). In each of the battery string 5 and the battery cell 6, in addition to the battery capacity, the open circuit voltage (OCV) and the OCV curve are also battery characteristic parameters. The OCV curve is a function that shows the relationship between OCV and parameters other than OCV. For example, the OCV curve is a function that shows the relationship between OCV and SOC or the amount of charge. In addition, in each of the battery string 5 and the battery cell 6, the internal resistance, which is one of the internal state parameters, is also a battery characteristic parameter that shows the battery characteristics. In one example, the internal state estimation unit 15 can estimate the above-mentioned battery characteristic parameters based on the estimated internal state parameters.

[0058] The data storage unit 17 stores the operation data used in the operation of estimating the above-mentioned internal state parameters. The internal state estimation unit 15 reads the operation data required for the estimation of the internal state parameters, etc. from the data storage unit 17. The operation data includes, for example, a function representing the OCP (open circuit potential) of the positive electrode in each of the battery cells 6 and the battery string 5 relative to the SOC of the positive electrode, and a function representing the OCP of the negative electrode in each of the battery cells 6 and the battery string 5 relative to the SOC of the negative electrode. In addition, in the estimation of the above-mentioned internal state parameters, intermediate estimation values ​​are calculated in the process of obtaining the final estimation result, etc. The above-mentioned operation data may include the intermediate estimation value of each internal state parameter. In addition, the internal state estimation unit 15 can store the respective intermediate estimation values ​​and final estimation values ​​of the internal state parameters in the data storage unit 17, which estimation values ​​are required in the subsequent estimation process.

[0059] It should be noted that, for example, Patent Document 4 (Japanese Patent Application Laid-Open No. 2018-147827) mentioned above discloses estimating the internal state parameters of a battery cell through charge curve analysis. In this embodiment, for example, the internal state parameters described above are estimated in the same manner as the charge curve analysis of Patent Document 4. Alternatively, battery characteristic parameters can be estimated based on the internal state parameters in the same manner as described in Patent Document 4. For example, the upper and lower limit voltages applied to the OCV in each of the battery cell 6 and the battery string 5 are stored as calculation data in the data storage unit 17.

[0060] Determination unit 16 performs processing using the first, second, and third internal state parameters estimated by internal state estimation unit 15. Determination unit 16 determines the degradation variation among the plurality of batteries 6 in battery string 5 based on at least the first and second internal state parameters. Determination unit 16 compares the first and second internal state parameters when determining the degradation variation among the plurality of batteries 6. In one example, determination unit 16 calculates the difference between the first and second internal state parameters. Furthermore, the greater the difference between the first and second internal state parameters, the greater the determination unit 16 determines that the degradation variation among the plurality of batteries 6 is.

[0061] Here, the determination unit 16 determines the degradation deviation between the batteries 6 based on one or more determination items. The data storage unit 17 stores reference data, which serves as a reference for the relationship between the degradation deviation and one or more determination items. The determination unit 16 reads the reference data from the data storage unit 17 and determines the degradation deviation based on the first internal state parameter, the second internal state parameter, and the reference data described above. An example of a determination item in the determination of the degradation deviation is the difference between the first internal state parameter and the second internal state parameter. Specifically, the difference between the first internal state parameter and the second internal state parameter for any one of the positive electrode capacity, the negative electrode capacity, the SOW, and the internal resistance is used as the determination item.

[0062] In addition, by estimating the first internal state parameter as described above, a first associated parameter related to the first internal state parameter can be estimated. Examples of the first associated parameter include: the battery capacity, battery capacity maintenance rate, positive electrode capacity maintenance rate, and negative electrode capacity maintenance rate of the battery cell 6 when the voltage changes in the same way as the first voltage data during charging or discharging. In addition, by estimating the second internal state parameter as described above, a second associated parameter related to the second internal state parameter can be estimated. Examples of the second associated parameter include: the battery capacity, battery capacity maintenance rate, positive electrode capacity maintenance rate, and negative electrode capacity maintenance rate of the battery cell 6 when the voltage changes in the same way as the second voltage data during charging or discharging. Here, the positive electrode capacity maintenance rate is the ratio of the estimated positive electrode capacity to the positive electrode capacity at the beginning of use, and the negative electrode capacity maintenance rate is the ratio of the estimated negative electrode capacity to the negative electrode capacity at the beginning of use.

[0063] When determining degradation variations among the plurality of batteries 6, the determination unit 16 may compare the first and second correlated parameters, instead of or in addition to comparing the first and second internal state parameters. In one example, the greater the difference between the first and second correlated parameters, the greater the degradation variations among the plurality of batteries 6. In this case, the criteria for determining degradation variations include, for example, the difference between the first and second correlated parameters. Specifically, the difference between the first and second correlated parameters for any one of the battery capacity, battery capacity retention rate, positive electrode capacity retention rate, and negative electrode capacity retention rate is used as the determination criteria.

[0064] Figure 6 : is a schematic diagram illustrating an example of reference data used as a reference for the relationship between degradation variations among a plurality of batteries and one or more determination items. Figure 6 In the example, determination is made based on two determination items, namely, the difference ΔX in the positive electrode capacity between the first internal state parameter and the second internal state parameter, and the difference ΔY in the negative electrode capacity between the first internal state parameter and the second internal state parameter. Figure 6 In the reference data, two threshold values ​​ΔXth1 and ΔXth2 (ΔXth1 < ΔXth2) are set for the difference ΔX in the positive electrode capacity, and two threshold values ​​ΔYth1 and ΔYth2 (ΔYth1 < ΔYth2) are set for the difference ΔY in the negative electrode capacity.

[0065] Based on Figure 6 In determining the reference data, when the positive electrode capacity difference ΔX is less than the threshold ΔXth1 and the negative electrode capacity difference ΔY is less than the threshold ΔYth1, the determination unit 16 sets the degradation variation among the plurality of batteries 6 to "Level 1" and determines that the degradation variation is relatively small. Furthermore, in each of the following two cases, the determination unit 16 sets the degradation variation among the plurality of batteries 6 to "Level 2" and determines that the degradation variation is moderate: when the positive electrode capacity difference ΔX is less than the threshold ΔXth2 and the negative electrode capacity difference ΔY is greater than or equal to the threshold ΔYth1 and less than ΔYth2; and when the positive electrode capacity difference ΔX is greater than or equal to the threshold ΔXth1 and less than ΔXth2, and the negative electrode capacity difference ΔY is less than the threshold ΔYth2. Furthermore, in each of the following two cases, the determination unit 16 sets the degradation variation among the plurality of batteries 6 to "Level 3" and determines that the degradation variation is relatively large: when the positive electrode capacity difference ΔX is greater than or equal to the threshold ΔXth2; and when the negative electrode capacity difference ΔY is greater than or equal to the threshold ΔYth2.

[0066] It should be noted that in Figure 6In the example, the degradation variation among the plurality of batteries 6 is classified into three levels. However, the degradation variation among the batteries 6 may be classified into five levels, for example. Furthermore, the degradation variation among the batteries 6 may be represented by a variation index or the like. In this case, for example, a larger variation index indicates a larger degradation variation among the plurality of batteries 6.

[0067] In addition, the determination unit 16 determines the degree of degradation of the battery string 5 as a whole, that is, the degree of degradation of the series-connected portion of the plurality of batteries 6 as a whole, based on at least the third internal state parameter. Here, the determination unit 16 determines the degree of degradation of the battery string 5 based on one or more determination items. The data storage unit 17 stores reference data, which serves as a reference for the relationship between the degree of degradation of the battery string 5 and one or more determination items. The determination unit 16 reads the reference data from the data storage unit 17 and determines the degree of degradation based on the third internal state parameter and the reference data described above. The determination items when determining the degree of degradation of the battery string 5 include: the positive electrode capacity, the negative electrode capacity, the SOW, and the internal resistance of the battery string 5 estimated as the third internal state parameter.

[0068] Furthermore, by estimating the third internal state parameter as described above, a third associated parameter related to the third internal state parameter can be estimated. Examples of the third associated parameter include the battery capacity, battery capacity retention rate, positive electrode capacity retention rate, and negative electrode capacity retention rate of the battery string 5. When determining the degree of degradation of the battery string 5, the determination unit 16 can use any of the third associated parameters as a determination item instead of, or in addition to, the third internal state parameter.

[0069] In one example, the degree of degradation of the battery string 5 is determined based on two determination items, namely, the positive electrode capacity retention rate and the negative electrode capacity retention rate of the battery string 5, which serve as third correlation parameters. In this case, the greater the positive electrode capacity retention rate, that is, the closer the positive electrode capacity retention rate is to 100%, the less deterioration the battery string 5 is determined to be. Furthermore, the greater the negative electrode capacity retention rate, that is, the closer the negative electrode capacity retention rate is to 100%, the less deterioration the battery string 5 is determined to be.

[0070] Furthermore, in addition to the first and second internal state parameters, the determination unit 16 may also determine the degradation variation among the plurality of batteries 6 in the battery string 5 based on the third internal state parameter. In this case, the determination unit 16 determines the degradation variation among the plurality of batteries 6 by comparing the third internal state parameter with the first and second internal state parameters. In one example, the determination unit 16 calculates the difference between the first and third internal state parameters, and the difference between the second and third internal state parameters. The determination unit 16 then determines the degradation variation among the plurality of batteries 6 based on the difference between the first and third internal state parameters, and the difference between the second and third internal state parameters.

[0071] In one example, the absolute value ε1 of the difference in negative electrode capacity between the first internal state parameter and the third internal state parameter, and the absolute value ε2 of the difference in negative electrode capacity between the second internal state parameter and the third internal state parameter are calculated. Then, based on the absolute values ​​ε1 and ε2 of these differences, the determination unit 16 determines the degradation variation among the plurality of batteries 6. In this case, the determination unit 16 determines, for example, whether either the absolute value ε1 of the difference or the absolute value ε2 of the difference is greater than a threshold value εth. If each of the absolute value ε1 of the difference and the absolute value ε2 of the difference is less than the threshold value εth, the determination unit 16 determines that the degradation variation among the plurality of batteries 6 is small. On the other hand, if either the absolute value ε1 of the difference or the absolute value ε2 of the difference is greater than the threshold value εth, the determination unit 16 determines that the degradation variation among the plurality of batteries 6 is large.

[0072] Furthermore, when the absolute value of the difference ε1 or the absolute value of the difference ε2 is greater than or equal to the threshold value εth, that is, when it is determined that the degradation variation among the multiple batteries 6 is large, the determination unit 16 determines whether the absolute values ​​ε1 and ε2 differ greatly from each other. Then, if the absolute values ​​ε1 and ε2 differ greatly from each other, the determination unit 16 determines which of the absolute values ​​ε1 and ε2 is larger. Then, if the absolute values ​​ε1 and ε2 differ greatly from each other, and the absolute value ε2 is greater than the absolute value ε1, the determination unit 16 determines that the degradation variation among the multiple batteries 6 is large, and determines that the safety and performance of the battery string 5 are significantly reduced. Therefore, when the absolute values ​​ε1 and ε2 are used for determination, in addition to the degradation variation among the multiple batteries 6, the safety of the battery string 5 and the like are also determined.

[0073] As described above, in this embodiment, the determination device 3 determines the degradation variation among the plurality of batteries 6 in the battery string 5 based on at least the first and second voltage data. Furthermore, the determination device 3 determines the degree of degradation of the entire battery string 5 (the entire series-connected portion) based on the third voltage data. Furthermore, the determination device 3 may also notify the user of the battery-mounted device equipped with the storage battery 2 of the results of the above determinations via a user interface or the like. In this case, the notification of the results of the determinations may be by voice or by a screen display or the like.

[0074] Figure 7 The flowchart shows the determination process of a battery string executed by the determination device according to the embodiment. The determination process is performed regularly at a predetermined time based on any one of the battery's operating time, operating power, other indicators, specific events, etc. Figure 7 In one example, the determination process is repeatedly performed at predetermined intervals. Figure 7 In another example, the user of the battery-mounted device equipped with the battery 2 enters an operation instruction through the user interface to execute Figure 7 processing.

[0075] If you start Figure 7 , the data acquisition unit 13 of the determination device 3 acquires the above-mentioned first voltage data and second voltage data (S101). At this time, the data acquisition unit 13 can receive the first voltage data and second voltage data generated by the battery management unit 12, etc., or the data acquisition unit 13 can generate the first voltage data and second voltage data. Then, the data acquisition unit 13 acquires the above-mentioned third voltage data (S102). Subsequently, the internal state estimation unit 15 estimates the first internal state parameter based on the first voltage data as described above, and estimates the second internal state parameter based on the second voltage data as described above (S103). In addition, the internal state estimation unit 15 estimates the third internal state parameter based on the third voltage data as described above (S104).

[0076] Furthermore, the determination unit 16 compares the first internal state parameter and the second internal state parameter (S105). In this case, instead of comparing the first and second internal state parameters, or in addition to comparing the first and second internal state parameters, the determination unit 16 may also compare the first and second associated parameters described above. Furthermore, as described above, the determination unit 16 may compare the third internal state parameter with the first and second internal state parameters (S106). Then, based on the comparison results between the first and second internal state parameters, etc., the determination unit 16 determines the degradation variation between the plurality of cells 6 in the battery string 5 (S107). In this case, in addition to the comparison results between the first and second internal state parameters, the determination unit 16 may also determine the degradation variation between the cells 6 in the battery string 5 based on the comparison results between the third internal state parameter and the first and second internal state parameters. Furthermore, based at least on the third internal state parameter, the determination unit 16 determines the degree of degradation of the battery string 5 (the degree of degradation of the entire series connection of the plurality of cells 6) (S108).

[0077] In this embodiment, degradation variations among the multiple cells 6 of the battery string 5 are determined based on first voltage data and second voltage data. The first voltage data represents the maximum voltage Vmax, which is the highest among the voltages of the multiple cells 6, during each of multiple measurement periods during charging or discharging of the battery string 5, and the second voltage data represents the minimum voltage Vmin, which is the lowest among the voltages of the multiple cells 6, during each of multiple measurement periods during charging or discharging of the battery string 5. Therefore, the degradation variation determination process does not require internal state estimation or other processing for all cells 6. Consequently, degradation variations among the multiple cells 6 are determined without complicating the data acquisition structure and process. Furthermore, in this embodiment, the determination is made based on the first voltage data representing changes in the maximum voltage Vmax of the battery string 5 during charging or discharging, and the second voltage data representing changes in the minimum voltage Vmin of the battery string 5 during charging or discharging. This allows for more appropriate determination of degradation variations among the multiple cells 6.

[0078] Furthermore, in this embodiment, when the voltage measured during each of the multiple periods equals the maximum voltage Vmax of the first voltage data, the first internal state parameter is estimated as the internal state of the battery cell 6. And when the voltage measured during each of the multiple periods equals the minimum voltage Vmin of the second voltage data, the second internal state parameter is estimated as the internal state of the battery cell 6. Furthermore, for example, by comparing the first and second internal state parameters, degradation variations among the multiple batteries 6 are determined. By performing the determination based on the first and second internal state parameters, degradation variations among the multiple batteries 6 can be more appropriately determined.

[0079] It should be noted that, in addition to the degree of degradation, factors such as temperature and arrangement within the battery string 5 also affect the voltage of each of the plurality of batteries 6 in the battery string 5. Therefore, by making a determination based on, for example, a comparison between the first internal state parameter and the second internal state parameter, the accuracy of determining degradation variations among the plurality of batteries 6 is improved compared to, for example, a case where a determination is made based solely on a comparison between the first voltage data and the second voltage data.

[0080] Furthermore, in this embodiment, the degree of degradation of the battery string 5 is determined based on third voltage data representing the voltage of the battery string 5 (the voltage of the entire series-connected portion of the plurality of batteries 6) measured during each of multiple periods of charging or discharging the battery string 5. Therefore, in this embodiment, while maintaining the small amount of data required for processing, that is, without complicating the data structure and processing for acquiring the data, the degree of degradation of the battery string 5 is determined, in addition to the degradation variations among the plurality of batteries 6. Furthermore, in this embodiment, a third internal state parameter representing the internal state of the battery string 5 is estimated based on the third voltage data, and the degree of degradation of the battery string 5 is estimated based on the third internal state parameter. Therefore, the degree of degradation of the battery string 5 can also be appropriately determined.

[0081] It should be noted that in the embodiments described above, the determination device 3 is a computer (server) or a server in a cloud environment that is separate from the battery management unit 12, but the determination device 3 is not limited to this. In one embodiment, each battery management unit 12 can perform a determination for a corresponding battery string 5. In this case, each battery management unit 12 performs the same processing as the determination device 3 in the above-described embodiment, thereby determining the degradation deviation between the multiple batteries 6 in the corresponding battery string 5 and the degree of degradation of the corresponding battery string 5.

[0082] In at least one of the above-described embodiments or examples, degradation variations among a plurality of batteries connected in series are determined based on first voltage data representing the maximum voltage among the battery voltages measured during each of multiple battery charge or discharge periods, and second voltage data representing the minimum voltage among the battery voltages measured during each of these periods. This provides a determination device, a power storage system, a determination method, and a determination program that can appropriately determine degradation variations among a plurality of batteries connected in series without complicating the structure and processing for acquiring data.

[0083] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in form may be made to the embodiments described herein without departing from the spirit of the present invention. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the present invention.

[0084] Reference numerals

[0085] 1…power storage system; 2…battery; 3…determination device; 5…battery string; 6…battery; 8…cell; 11…measuring circuit; 12…battery management unit (BMU); 13…data acquisition unit; 15…internal state estimation unit; 16…determination unit; 17…data storage unit.

Claims

1. A determination device related to a plurality of batteries connected in series, comprising: a processor configured to determine a degradation deviation among the plurality of batteries based on first voltage data and second voltage data, wherein the first voltage data indicates a maximum voltage among the voltages of the plurality of batteries measured in each of a plurality of periods during which the plurality of batteries are charged or discharged, and the second voltage data indicates a minimum voltage among the voltages of the plurality of batteries measured in each of the plurality of periods. The processor is configured to: estimating a first internal state parameter as an internal state of the battery cell, the first internal state parameter being based on a change in the maximum voltage of the first voltage data; estimating a second internal state parameter as an internal state of the battery of the battery cell, the second internal state parameter being based on a change in the minimum voltage of the second voltage data; determining the degradation deviation among the plurality of batteries based on at least the first internal state parameter and the second internal state parameter; estimating a third internal state parameter representing an overall internal state of the series-connected portion of the plurality of batteries based on at least third voltage data representing a voltage of the series-connected portion of the plurality of batteries during each of the plurality of periods of charge or discharge of the plurality of batteries; as well as The degradation deviation among the plurality of batteries is determined by comparing the third internal state parameter with the first internal state parameter and the second internal state parameter.

2. The determination device according to claim 1, wherein: The processor is configured to: The degradation deviation among the plurality of batteries is determined by comparing the first internal state parameter and the second internal state parameter.

3. The determination device according to claim 2, wherein: The processor is configured to: The larger the difference between the first internal state parameter and the second internal state parameter, the larger the deviation in degradation among the plurality of batteries is determined to be.

4. The determination device according to claim 1, wherein: The processor is configured to: The degree of degradation of the entire series connection of the plurality of batteries is determined based on third voltage data indicating the voltage of the series connection of the plurality of batteries measured in each of the plurality of periods in which the plurality of batteries are charged or discharged.

5. The determination device according to claim 4, wherein: The processor is configured to: The degree of degradation of the entire series-connected portion of the plurality of batteries is determined based on at least the third internal state parameter.

6. A power storage system comprising: The determination device according to any one of claims 1 to 5; as well as the plurality of batteries connected in series, The processor of the determination device is configured to determine the degradation deviation among the plurality of batteries.

7. The power storage system according to claim 6, wherein: The system further includes a measuring circuit that periodically measures the voltage of each of the plurality of batteries during each of the plurality of periods during which the plurality of batteries are charged or discharged. The first voltage data and the second voltage data are generated based on at least a measurement result of the voltage of each of the plurality of batteries by the measurement circuit.

8. The power storage system according to claim 6, wherein: Each of the plurality of batteries includes a plurality of unit cells, and The unit cells are connected in parallel in each of the plurality of batteries.

9. A method for determining a plurality of batteries connected in series, comprising the following steps: determining a degradation variation among the plurality of batteries based on first voltage data and second voltage data, wherein the first voltage data indicates a maximum voltage among the voltages of the plurality of batteries measured in each of a plurality of periods during which the plurality of batteries are charged or discharged, and the second voltage data indicates a minimum voltage among the voltages of the plurality of batteries measured in each of the plurality of periods; in Determining the degradation deviation includes: estimating a first internal state parameter as an internal state of the battery cell, the first internal state parameter being based on a change in the maximum voltage of the first voltage data; estimating a second internal state parameter as an internal state of the battery of the battery cell, the second internal state parameter being based on a change in the minimum voltage of the second voltage data; determining the degradation deviation among the plurality of batteries based on at least the first internal state parameter and the second internal state parameter; estimating a third internal state parameter representing the entire internal state of the series-connected portion of the plurality of batteries based on at least third voltage data representing the voltage of the series-connected portion of the plurality of batteries during each of the plurality of periods of charge or discharge of the plurality of batteries; and The degradation deviation among the plurality of batteries is determined by comparing the third internal state parameter with the first internal state parameter and the second internal state parameter.

10. A nonvolatile storage medium storing a determination program related to a plurality of batteries connected in series, the determination program causing a computer to perform the following operations: determining a degradation variation among the plurality of batteries based on first voltage data and second voltage data, wherein the first voltage data indicates a maximum voltage among the voltages of the plurality of batteries measured in each of a plurality of periods during which the plurality of batteries are charged or discharged, and the second voltage data indicates a minimum voltage among the voltages of the plurality of batteries measured in each of the plurality of periods; in Determining the degradation deviation includes: estimating a first internal state parameter as an internal state of the battery cell, the first internal state parameter being based on a change in the maximum voltage of the first voltage data; estimating a second internal state parameter as an internal state of the battery of the battery cell, the second internal state parameter being based on a change in the minimum voltage of the second voltage data; determining the degradation deviation among the plurality of batteries based on at least the first internal state parameter and the second internal state parameter; estimating a third internal state parameter representing the entire internal state of the series-connected portion of the plurality of batteries based on at least third voltage data representing the voltage of the series-connected portion of the plurality of batteries during each of the plurality of periods of charge or discharge of the plurality of batteries; and The degradation deviation among the plurality of batteries is determined by comparing the third internal state parameter with the first internal state parameter and the second internal state parameter.

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