Battery state detection device and program

Abstract

This battery system has a battery module (11) in which a plurality of battery cells (13) are connected in series, and the state of each battery cell is detected by a state detection unit. This battery state detection device (20) comprises: an acquisition unit that acquires a state detection value of each battery cell detected by the state detection unit; a parameter change amount calculation unit that uses, as a state parameter of a battery cell, one of the state detection value acquired by the acquisition unit and a state calculation value that is calculated by the state detection value and indicates the state of the battery cell, and calculates, as a parameter change amount, the amount of change in a predetermined period of the state parameter; and an abnormality detection unit that uses a plurality of battery cells one by one as an object cell to be subjected to abnormality detection, and detects an abnormality in the object cell on the basis of whether or not a predetermined deviation occurs in the parameter change amount with respect to the battery cells other than the object cell in the object cell.

Description

Battery state detection device and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-148760 filed on September 13, 2023 and Japanese Application No. 2024-097399 filed on June 17, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a battery state detection device and a program.

[0003] Various techniques have been proposed in the past for determining whether or not there is an abnormality in a storage battery mounted on a vehicle, etc. For example, in the technique described in Patent Document 1, in an energy storage module in which energy storage devices are connected to each other by bus bars, the instantaneous resistance value immediately after constant current charging begins and the diffused resistance value after a certain time has elapsed since the start of constant current charging are extracted, and the ratio between the instantaneous resistance value and the diffused resistance value is compared with a predetermined threshold value to determine whether or not there is an abnormality in the connection of the bus bars.

[0004] JP 2015-68821 A

[0005] Thermal runaway is an abnormality in storage batteries, and various technologies for detecting thermal runaway have been proposed. For example, the initial stage of thermal runaway is an internal short circuit in a battery cell. Therefore, a technology has been developed that determines whether an internal short circuit has occurred in a battery cell by comparing changes in internal resistance or terminal voltage with a predetermined threshold value.

[0006] However, when an internal short circuit occurs in a battery cell as a precursor to thermal runaway, the diffusion resistance fluctuates slowly over time in the early stages of the internal short circuit. Therefore, there is a concern that an internal short circuit in a battery cell cannot be accurately detected under conditions where voltage fluctuations due to charging and discharging or vehicle noise occur in a vehicle. In particular, there is a concern that abnormality detection using a single cell may result in false detection due to factors such as the temperature environment.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide a battery state detection device and program that can quickly and accurately detect internal short-circuit abnormalities in battery cells, which are a sign of thermal runaway.

[0008] The battery state detection device of the present disclosure is applied to a battery system having a battery module in which a plurality of battery cells are connected in series, and in which the state of each of the battery cells is detected by a state detection unit, and comprises: an acquisition unit that acquires state detection values ​​of each of the battery cells detected by the state detection unit; a parameter change calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; and an abnormality detection unit that sets each of the plurality of battery cells as a target cell to be subject to abnormality detection, and detects an abnormality in the target cell based on whether or not a predetermined deviation occurs in the parameter change amount of the target cell compared to battery cells other than the target cell.

[0009] According to the above configuration, abnormality detection for each battery cell in a battery module is performed not for a single cell but relative to other battery cells. Therefore, even if voltage fluctuations or noise occur in the current path of the battery module, the effects of these fluctuations can be suppressed while detecting abnormalities. Furthermore, false detection due to environmental conditions such as temperature in the battery module is suppressed. Therefore, even if an internal short circuit occurs as an early stage of thermal runaway, even if the diffusion resistance of the battery cell fluctuates slowly over time, differences in parameter changes between normal and abnormal cells can be found early, allowing the abnormal cell to be properly detected. As a result, an internal short circuit abnormality in a battery cell, which is a precursor to thermal runaway, can be detected quickly and accurately.

[0010] The battery state detection device of the present disclosure is applied to a battery system having a battery module in which a plurality of battery cells are connected in series, and in which the state of each battery cell is detected by a state detection unit, and includes: a first abnormality detection unit that performs abnormality detection for each battery cell by calculation processing with a relatively small calculation load based on the state detection value of each battery cell detected by the state detection unit; a second abnormality detection unit that performs abnormality detection for each battery cell by calculation processing with a relatively large calculation load based on the state detection value of each battery cell detected by the state detection unit; and a switching execution unit that switches between detecting abnormalities in each battery cell by the first abnormality detection unit and detecting abnormalities in each battery cell by the second abnormality detection unit based on a predetermined switching condition.

[0011] According to the above configuration, two types of abnormality determination are possible when detecting an abnormality in each battery cell, and the abnormality determination is switched according to a predetermined switching condition. Here, when a battery cell is used over a long period of time, there may be situations where a cell abnormality is easy to detect and situations where it is difficult to detect. In such cases, by switching the abnormality determination process according to the predetermined switching condition, it is possible to achieve appropriate abnormality detection while suppressing excessive computational load.

[0012] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of a battery system, Fig. 2 is a diagram for explaining the cell voltage of each battery cell in a battery module, Fig. 3 is a diagram showing an equivalent circuit of a battery cell, Fig. 4 is a time chart showing changes in the cell voltage of each battery cell, Fig. 5 is a flowchart showing a battery cell abnormality detection process in a first embodiment, Fig. 6 is a flowchart showing the battery cell abnormality detection process in the first embodiment, Fig. 7 is a time chart for specifically explaining the battery cell abnormality detection process, Fig. 8 is a diagram for explaining an overview of cell abnormality detection in a second embodiment, Fig. 9 is a flowchart showing the battery cell abnormality detection process in the second embodiment, Fig. 10 is a flowchart showing the battery cell abnormality detection process in the second embodiment, Fig. 11 is a flowchart showing the battery cell abnormality detection process in a third embodiment, Fig. 12 is a flowchart showing the battery cell abnormality detection process in the third embodiment, and Fig. 13 is a flowchart showing the battery cell abnormality detection process in the third embodiment. 14 is a flowchart showing the battery cell abnormality detection process in the fourth embodiment, FIG. 15 is a flowchart showing the battery cell abnormality detection process in the fourth embodiment, FIG. 16 is a flowchart showing the battery cell abnormality detection process in the fourth embodiment, FIG. 17 is a diagram showing the configuration of a battery system in the fifth embodiment, FIG. 18 is a flowchart showing the battery cell abnormality detection process in the fifth embodiment, FIG. 19 is a time chart showing changes in cell voltage in an assembled battery, FIG. 20 is a flowchart showing the battery cell abnormality detection process in the sixth embodiment, FIG. 21 is a diagram showing the configuration of a battery system in the seventh embodiment, FIG. 22 is a flowchart showing the battery cell abnormality detection process in the seventh embodiment, FIG. 23 is a flowchart showing the battery cell abnormality detection process in the eighth embodiment, FIG. 24 is a flowchart showing the battery cell abnormality detection process in another example, FIG. 25 is a time chart showing changes in cell voltage and cell temperature in an internal short-circuiting step,FIG. 27 is a diagram showing an example of the configuration of a battery system, FIG. 27 is a flowchart showing an abnormality detection process for a battery cell in another example, FIG. 28 is a diagram showing the voltage-capacity characteristics of a battery cell, and FIG. 29 is a flowchart showing an abnormality detection process for a battery cell in another example.

[0013] A battery system according to this embodiment will be described below. In this embodiment, a battery system mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle will be described with reference to the drawings. This battery system has a high-voltage battery with a voltage between both the positive and negative terminals of several hundred volts. This battery system can also be applied to aircraft such as drones, ships, construction machinery, agricultural machinery, and the like, in addition to electric vehicles.

[0014] First Embodiment First, an overview of a battery system in a vehicle will be described using FIG. 1 . In FIG. 1 , the battery system includes a plurality of battery units 10 and a battery ECU 20 that manages each of the battery units 10. Each battery unit 10 includes a battery module 11 and a monitoring device 12 that monitors the battery module 11. The battery module 11 is configured by connecting a plurality of battery cells 13 in series. Each battery cell 13 is configured, for example, by a lithium-ion secondary battery or a nickel-metal hydride secondary battery. Note that a lithium-ion secondary battery is a secondary battery that uses lithium as a charge carrier, and may include not only a typical lithium-ion secondary battery that uses a liquid electrolyte, but also an all-solid-state battery that uses a solid electrolyte.

[0015] The battery modules 11 of each battery unit 10 are connected in series to form a battery pack B. The battery pack B is a high-voltage battery that generates a terminal voltage of several hundred volts. Note that the battery pack B may be one in which the battery modules 11 are connected in parallel, or one in which the battery modules 11 are connected in series and parallel.

[0016] The monitoring devices 12 of each battery unit 10 are slave devices of the battery ECU 20, and the battery ECU 20 and the multiple monitoring devices 12 can communicate with each other via wired or wireless communication. The battery ECU 20 is configured with a microcomputer including a CPU, ROM, RAM, etc. The battery ECU 20 executes various processes related to battery control based on programs stored in the ROM. The battery ECU 20 executes control related to charging or discharging of the battery pack B, for example. The monitoring devices 12 acquire information related to the battery modules 11 in response to commands from the battery ECU 20 and transmit the information to the battery ECU 20. The monitoring devices 12 may acquire information related to the battery modules 11 at a predetermined interval. The monitoring devices 12 are also referred to as satellite monitoring devices. In this embodiment, the battery ECU 20 corresponds to the "battery state detection device."

[0017] The monitoring device 12 is provided with a voltage sensor 31 that detects the terminal voltage of each battery cell 13. More specifically, an electrical path 32 is connected to each end of each battery cell 13 in the battery module 11, and the voltage sensor 31 is connected to the electrical path 32. The voltage sensor 31 corresponds to the "state detection unit," and the terminal voltage (cell voltage) detected by the voltage sensor 31 corresponds to the "detected state value." In addition, a current sensor 33 that detects the current flowing through each battery cell 13 is provided in the cell series path of the battery module 11.

[0018] A rotating electric machine unit is connected to the battery pack B as an electrical load driven by power supplied from the battery pack B. The rotating electric machine unit includes a rotating electric machine 41 and an inverter 42 as a power converter that supplies phase current to the rotating electric machine 41. The rotating electric machine 41 is an on-vehicle main engine capable of transmitting power to drive wheels (not shown). The rotating electric machine 41 is, for example, a three-phase AC motor, and the inverter 42 adjusts the current flowing in each phase winding by turning on and off switches (semiconductor switching elements) on upper and lower arms provided for each phase winding.

[0019] When thermal runaway occurs in the battery module 11, an internal short circuit occurs in a battery cell 13 in the initial stage of the process leading up to thermal runaway, followed by gas generation, cell case deformation, and ignition. In this case, it is desirable to detect an internal short circuit in a battery cell 13 in order to quickly detect the signs of thermal runaway. In this embodiment, an internal short circuit anomaly is detected based on the amount of change in cell voltage of each battery cell 13.

[0020] The change in the cell voltage of the battery cell 13 caused by an internal short circuit will be described below.

[0021] 2 is a diagram illustrating the cell voltage of each battery cell 13 in the battery module 11. In Fig. 2, n battery cells 13 are connected in series in the battery module 11, and the battery cells 13 are designated, in order from the lowest potential side, as the first cell C1, the second cell C2, the third cell C3, ..., and the nth cell Cn. The inter-terminal voltages of the cells C1 to Cn are designated as cell voltages V1 to Vn, respectively, the amount of change in each cell voltage V1 to Vn over a predetermined period is designated as voltage change amounts VA1 to VAn, and the differences between the voltage change amounts VA1 to VAn for every two adjacent battery cells 13 in the series path are designated as voltage difference values ​​ΔV21, ΔV32, ..., ΔVn,n-1.

[0022] The voltage difference values ​​ΔV21, ΔV32, ... ΔVn,n-1 are calculated by subtracting two adjacent battery cells 13 in the series path in ascending or descending order of the cell serial connection, and are calculated here by subtracting the voltage change VA of the lower-potential battery cell 13 from the voltage change VA of the higher-potential battery cell 13. For example, the voltage difference value ΔV21 is the value obtained by subtracting the voltage change VA1 of the first cell C1 from the voltage change VA2 of the second cell C2, and the voltage difference value ΔV32 is the value obtained by subtracting the voltage change VA2 of the second cell C2 from the voltage change VA3 of the third cell C3. The voltage difference value ΔV between battery cells 13 may be any value that indicates the difference in the voltage change amount VA between two of the n battery cells 13. For example, the voltage difference value ΔV31 is the value obtained by subtracting the voltage change amount VA1 of the first cell C1 from the voltage change amount VA3 of the third cell C3, and the voltage difference value ΔV1n is the value obtained by subtracting the voltage change amount VAn of the nth cell Cn from the voltage change amount VA1 of the first cell C1.

[0023] 3 is a diagram showing an equivalent circuit of the battery cell 13. The battery cell 13 is composed of an electromotive force OCV, a solution resistance RΩ, a parallel connection of a charge transfer resistance Rct and an interfacial capacitance Cd, and a diffusion resistance Zw, all connected in series. When an internal short circuit occurs in the battery cell 13, the positive electrode path and the negative electrode path are short-circuited by the internal short-circuit resistance Rint, and a short-circuit current flows inside the cell.

[0024] 4 is a time chart showing changes in the cell voltages of the multiple battery cells 13 in the battery module 11. Here, the voltage changes of the first cell C1 to the third cell C3 out of the n battery cells 13 shown in FIG. 2 are illustrated as an example, and the changes in the cell voltages of the individual battery cells 13 and the changes in the voltage difference between the battery cells 13 are explained assuming that an internal short circuit abnormality has occurred in the second cell C2.

[0025] If an internal short circuit occurs in the second cell C2, a short-circuit current flows within the second cell C2. Therefore, when the cell voltages of the battery cells 13 decrease during discharge of the battery module 11, the rate of voltage drop per unit time (i.e., the slope of the voltage change) of the cell voltage V2 of the second cell C2 becomes greater than the cell voltages V1 and V3 of the first and third cells C1 and C3. If the voltage changes of the cells C1 to C3 from the start of discharge, defined as VA1 to VA3, are taken as the reference (initial value) at the start of discharge, each of the voltage changes VA1 to VA3 gradually increase negatively over time, but the magnitudes of the voltage changes VA1 to VA3 differ between the second cell C2 and the other cells C1 and C3. In terms of absolute values, the relationships between the voltage changes VA1 to VA3 are |VA2|>|VA1| and |VA2|>|VA3|.

[0026] Moreover, the voltage difference value ΔV21, which is the difference between the absolute values ​​of the voltage changes VA1 and VA2 of cells C1 and C2, gradually becomes more positive over time, and the voltage difference value ΔV32, which is the difference between the absolute values ​​of the voltage changes VA2 and VA3 of cells C2 and C3, gradually becomes more negative over time. Note that for cells C1 and C3, the voltage difference value ΔV13 remains approximately constant (approximately zero) over time.

[0027] 4 shows a period in which the power supply to the battery module 11 is stopped after discharging in the battery module 11. During this period, the cell voltages V1 and V3 of the cells C1 and C3 remain constant, whereas the cell voltage V2 of the second cell C2 decreases due to the flow of a short-circuit current. Therefore, even after discharging is completed, the voltage difference value ΔV21 increases to the positive side, and the voltage difference value ΔV32 increases to the negative side.

[0028] This embodiment focuses on the above-described voltage change of each battery cell 13 to detect an internal short circuit abnormality in the battery cell 13. In summary, the voltage change amount VA of each battery cell 13 is calculated, and each of the plurality of battery cells 13 is designated as a target cell for abnormality detection, and an abnormality in the target cell is detected based on whether or not a predetermined deviation occurs in the voltage change amount VA of the target cell compared to the other battery cells 13.

[0029] In this embodiment, the difference in the voltage change amount VA between the target cell and two or more different battery cells 13 is calculated as a voltage difference value ΔV, and based on the voltage difference value ΔV, it is determined whether or not a predetermined deviation occurs in the target cell relative to the battery cells 13 other than the target cell, and an abnormality in the target cell is detected based on the determination result. Note that the cell voltage V as a state detection value corresponds to the "state parameter," the voltage change amount VA corresponds to the "parameter change amount," and the voltage difference value ΔV corresponds to the "change amount difference value." The abnormality detection process in this embodiment will be described in detail below.

[0030] 5 is a flowchart showing the procedure for detecting an abnormality in the battery cells 13, and this process is executed by the battery ECU 20. The battery ECU 20 executes abnormality detection for the battery cells 13 of each battery module 11.

[0031] In step S101, the cell voltage V(tm) of each battery cell 13 at time tm is obtained from the monitoring device 12. Time tm is a time that arrives at a predetermined time period, and the cell voltage V of each battery cell 13 is obtained at the predetermined time period. The interval between times tm is, for example, several tens to several hundreds of milliseconds. However, the interval between times tm may be several seconds, several minutes, or several hours.

[0032] In step S102, a voltage change amount VA(tm) is calculated for each battery cell 13, which is the amount of change in cell voltage V(tm) from an initial value (initial voltage value) (VA(tm) = V(tm) - initial value). In the following step S103, the absolute value of the voltage change amount VA(tm) is calculated. The voltage change amount VA(tm) is the amount of change in cell voltage V(tm) from the initial value during a predetermined period from the initial value to the present time. The initial value may be set for each battery cell 13 at any timing, and once set, it is maintained until the next setting timing arrives. The initial value may be reset periodically (for example, at intervals of several days to several months), according to a predetermined mileage of the vehicle, according to a predetermined number of times the vehicle has been started, or according to the timing of switching between discharging and charging of the battery module 11. Furthermore, when an equalization process is performed to equalize the cell voltages of the battery cells 13 in the battery module 11, the initial value may be reset based on the fact that the equalization process has been performed. Note that step S101 corresponds to the "acquisition unit," and step S102 corresponds to the "parameter change amount calculation unit."

[0033] Then, in step S104, for all battery cells 13, the difference in absolute value of the voltage change amount VA(tm) between two battery cells 13 adjacent to each other in the series path is calculated as a voltage difference value ΔVi+1,i(tm). The voltage difference value ΔVi+1,i(tm) may be calculated using the following equation (1): ΔVi+1,i(tm) = |VAi+1(tm)| - |VAi(tm)| ... (1) Note that the subscripts i+1 and i indicate cell numbers from 1 to n. The voltage difference value ΔVi+1,i(tm) is calculated for all combinations of two adjacent cells in the battery module 11.

[0034] When each battery cell 13 in the battery module 11 is treated as a target cell for anomaly detection, a voltage difference value ΔV(tm) between the target cell (cell Ci) and a first adjacent cell (cell Ci-1) adjacent to the target cell on the negative side is calculated, and a voltage difference value ΔV(tm) between the target cell (cell Ci) and a second adjacent cell (cell Ci+1) adjacent to the target cell on the positive side is calculated. These voltage difference values ​​ΔV(tm) and ΔV(tm) are obtained by subtracting the absolute value of the voltage change amount VA(tm) of each battery cell 13 in descending order of the cell serial connection. Note that each voltage difference value ΔV(tm) can also be calculated by subtracting in ascending order of the cell serial connection. The voltage difference value ΔVi,i-1(tm) between the target cell and the first adjacent cell on the negative side corresponds to the "first difference value," and the voltage difference value ΔVi+1,i(tm) between the target cell and the second adjacent cell on the positive side corresponds to the "second difference value." Furthermore, the first adjacent cell and the second adjacent cell are battery cells 13 different from the target cell, and also correspond to the "first non-target cell" and the "second non-target cell." Step S104 corresponds to the "difference value calculation unit."

[0035] Then, in step S105, each battery cell 13 (cells C1 to Cn) is treated as a target cell, and the voltage difference values ​​ΔVi,i-1(tm) and ΔVi+1,i(tm) for each target cell are compared with predetermined thresholds. Specifically, it is determined whether the voltage difference value ΔVi,i-1(tm) calculated for the target cell and the first adjacent cell on the negative side is equal to or greater than a predetermined positive threshold value TH11, and it is determined whether the voltage difference value ΔVi+1,i(tm) calculated for the target cell and the second adjacent cell on the positive side is equal to or less than a predetermined negative threshold value TH12.

[0036] The positive threshold TH11 is a threshold defined as a positive value (TH11>0), and the negative threshold TH12 is a threshold defined as a negative value (TH12<0). The thresholds TH11 and TH12 have the same absolute value. However, the absolute values ​​of the thresholds TH11 and TH12 may be different.

[0037] The specific determination method in step S105 may be any method, as long as it determines whether the polarities of the voltage difference values ​​ΔVi,i-1(tm) and ΔVi+1,i(tm) for the target cell, cell Ci, are opposite to each other and whether the absolute values ​​of the voltage difference values ​​ΔVi,i-1(tm) and ΔVi+1,i(tm) are each equal to or greater than a predetermined threshold value.

[0038] If none of the battery cells 13 meets the condition that the voltage difference value ΔVi,i-1(tm) is equal to or greater than the positive threshold value TH11 and the voltage difference value ΔVi+1,i(tm) is equal to or less than the negative threshold value TH12, the process judges NO in step S105, increments m by 1 in step S106, and returns to step S101. If any of the battery cells 13 meets the condition that the voltage difference value ΔVi,i-1(tm) is equal to or greater than the positive threshold value TH11 and the voltage difference value ΔVi+1,i(tm) is equal to or less than the negative threshold value TH12, the process judges YES in step S105 and proceeds to step S107.

[0039] At this time, if an internal short-circuit abnormality has not occurred in the target battery cell 13, the condition of step S105 is not met for that battery cell 13, whereas if an internal short-circuit abnormality has occurred in the target battery cell 13, the condition of step S105 is met for that battery cell 13.

[0040] In step S107, it is determined that an abnormality has occurred in the battery cell 13 for which the condition in step S105 is satisfied. That is, it is determined that a predetermined deviation has occurred in the voltage change amount VA(tm) of one of the plurality of battery cells 13 (target cell) compared to the other battery cells 13. Thereafter, in step S108, the occurrence of an abnormality is notified. At this time, it is preferable to notify the vehicle user of the occurrence of an abnormality by, for example, turning on an abnormality warning light. It is also preferable to store diagnostic information indicating the occurrence of an abnormality in memory.

[0041] In the battery module 11, the first cell C1 with the lowest potential and the nth cell Cn with the highest potential have adjacent cells on only one side of the serial cell path. Therefore, for each of these cells C1 and Cn, the processing in steps S104 and S105 may be modified as follows.

[0042] When the first cell C1 is the target cell, the battery ECU 20 calculates two voltage difference values ​​ΔV(tm) by combining the first cell C1 with each of the two battery cells 13 on its positive side. Specifically, the battery ECU 20 calculates the difference in absolute values ​​of the voltage change amounts VA(tm) between the first cell C1 and the nth cell Cn as the voltage difference value ΔV1n(tm), and calculates the difference in absolute values ​​of the voltage change amounts VA(tm) between the first cell C1 and the second cell C2 as the voltage difference value ΔV21(tm). Then, it determines whether the voltage difference value ΔV1n(tm) is equal to or greater than the positive threshold value TH11, and determines whether the voltage difference value ΔV21(tm) is equal to or less than the negative threshold value TH12. The voltage difference value ΔV1n(tm) is calculated by subtracting the voltage change amount VAn of the nth cell Cn on the high potential side from the voltage change amount VA1 of the first cell C1 on the low potential side in the battery module 11, in the order of subtraction opposite to that of the voltage difference value ΔV21(tm). If the first cell C1 is an abnormal cell, the voltage difference value ΔV1n(tm) is calculated as a positive value. If the voltage difference value ΔV1n(tm) is equal to or greater than the positive threshold value TH11 and the voltage difference value ΔV21(tm) is equal to or less than the negative threshold value TH12, the first cell C1 is determined to be abnormal.

[0043] Here, the second cell C2 and the nth cell Cn correspond to the “first non-target cell” and the “second non-target cell.” In addition to this, it is also possible to calculate the voltage difference value ΔV(tm) using other combinations, such as the second cell C2 and the third cell C3 as the “first non-target cell” and the “second non-target cell.”

[0044] Furthermore, when the nth cell Cn is the target cell, the battery ECU 20 calculates two voltage difference values ​​ΔV(tm) by combining the nth cell Cn with each of the two negative battery cells 13. Specifically, the battery ECU 20 calculates the difference in absolute values ​​of the voltage change amounts VA(tm) between the nth cell Cn and the (n-1)th cell Cn-1 as the voltage difference value ΔVn,n-1(tm), and calculates the difference in absolute values ​​of the voltage change amounts VA(tm) between the first cell C1 and the nth cell Cn as the voltage difference value ΔV1n(tm). Then, it determines whether the voltage difference value ΔVn,n-1(tm) is equal to or greater than the positive threshold value TH11, and whether the voltage difference value ΔV1n(tm) is equal to or less than the negative threshold value TH12. If the voltage difference value ΔVn,n-1(tm) is equal to or greater than the positive threshold value TH11 and the voltage difference value ΔV1n(tm) is equal to or less than the negative threshold value TH12, it is determined that the n-th cell Cn is abnormal.

[0045] Here, the first cell C1 and the n-1th cell Cn-1 correspond to the "first non-target cell" and the "second non-target cell." In addition to this, it is also possible to calculate the voltage difference value ΔV(tm) using other combinations, such as the n-2th cell Cn-2 and the n-1th cell Cn-1 being the "first non-target cell" and the "second non-target cell."

[0046] It is also possible to calculate two voltage difference values ​​ΔV(tm) for each combination of a target cell and two battery cells 13 (non-target cells) on either the positive or negative side of the target cell for all battery cells 13 in the battery module 11, and to detect an abnormality in the target cell based on the two voltage difference values ​​ΔV(tm).In short, it is sufficient that the difference in the absolute value of the voltage change amount VA(tm) between the target cell and two or more different battery cells 13 is calculated as the voltage difference value ΔV(tm), and that the voltage difference value ΔV(tm) is used as a parameter for determining an abnormality.

[0047] The combination of battery cells 13 for calculating the voltage difference value ΔV(tm) may be a combination of an adjacent battery cell 13 and a battery cell 13 other than the adjacent cell with respect to the battery cell 13 that is the target cell, or a combination of two battery cells 13 other than the adjacent cell with respect to the battery cell 13 that is the target cell. For example, the voltage difference value ΔV(tm) may be calculated by combining every other two battery cells 13 with respect to the target cell, or by combining every two battery cells 13 with respect to the target cell. If the target cell is cell C3, the voltage difference value ΔV(tm) may be calculated by combining cells C1 and C3, and the voltage difference value ΔV(tm) may be calculated by combining cells C3 and C5.

[0048] The abnormality detection process of Fig. 5 can be modified as shown in Fig. 6. The process of Fig. 6 is a partial modification of the process of Fig. 5, and steps S201 to S203 are different from those of Fig. 5.

[0049] 6, as explained above, in steps S101 to S103, the cell voltage V(tm) of each battery cell 13 at time tm is acquired, the voltage change VA(tm) from the initial value is calculated, and the absolute value of the voltage change VA(tm) is calculated. In step S104, the difference in the absolute values ​​of the voltage change VA(tm) of two adjacent cells in the series path is calculated as the voltage difference value ΔV(tm).

[0050] Then, in step S201, the absolute value of the voltage difference value ΔVi+1,i(tm) is calculated, and in the following step S202, the absolute values ​​of the voltage difference value ΔVi+1,i(tm) calculated every time tm are integrated to calculate the integrated difference value QAi+1,i(tm). At this time, the absolute values ​​of the voltage difference value ΔVi,i-1(tm) between the target cell and the first adjacent cell (first non-target cell) are integrated at a predetermined period to calculate the integrated difference value QAi,i-1(tm). Also, the absolute values ​​of the voltage difference value ΔVi+1,i(tm) between the target cell and the second adjacent cell (second non-target cell) are integrated at a predetermined period to calculate the integrated difference value QAi+1,i(tm). The difference integrated value QAi,i-1(tm) corresponds to the "first difference integrated value", and the difference integrated value QAi+1,i(tm) corresponds to the "second difference integrated value".

[0051] Then, in step S203, each battery cell 13 (cells C1 to Cn) is designated as a target cell, and the differential integrated values ​​QAi,i-1(tm) and QAi+1,i(tm) are compared with a predetermined threshold for each target cell. Specifically, it is determined whether the differential integrated value QAi,i-1(tm) calculated for the target cell and the first adjacent cell on the negative side is equal to or greater than a predetermined threshold TH2, and it is also determined whether the differential integrated value QAi+1,i(tm) calculated for the target cell and the second adjacent cell on the positive side is equal to or greater than the threshold TH2.

[0052] If the conditions that the differential integrated value QAi,i-1(tm) is equal to or greater than the threshold value TH2 and the differential integrated value QAi+1,i(tm) is equal to or greater than the threshold value TH2 are not met for all the battery cells 13, the result in step S203 is negative, m is incremented by 1 in step S106, and the process returns to step S101. If the conditions that the differential integrated value QAi,i-1(tm) is equal to or greater than the threshold value TH2 and the differential integrated value QAi+1,i(tm) is equal to or greater than the threshold value TH2 are met for any of the battery cells 13, the result in step S203 is positive, and the process proceeds to step S107.

[0053] In step S107, it is determined that an abnormality has occurred in the battery cell 13 for which the condition in step S203 is met. Then, in step S108, a notification is given that an abnormality has occurred.

[0054] FIG. 7 is a time chart specifically illustrating the abnormality detection process for the battery cells 13. FIG. 7 shows the changes over time for each parameter shown in (a) to (e). Here, it is assumed that the battery module 11 repeatedly discharges and charges. Three battery cells 13 (cells C1 to C3) are shown, one of which (here, the second cell C2) is an abnormal cell in which an internal short circuit has occurred. The changes in cell voltage, etc., are shown over time for normal cells (other than the second cell) and the abnormal cell. In FIG. 7, the cell voltage V and voltage change VA of the normal cell are shown by a dashed-dotted line, and the cell voltage V and voltage change VA of the abnormal cell are shown by a solid line.

[0055] 7, the cell voltage V of each battery cell 13 decreases during the discharge period, and increases during the charge period. At this time, the voltage change VA of a normal cell differs from that of an abnormal cell. Therefore, for the abnormal cell (cell C2), the difference in voltage change VA between the negative-side adjacent cell (voltage difference value ΔV21) and the difference in voltage change VA between the positive-side adjacent cell (voltage difference value ΔV32) are opposite in polarity, and these differences are larger than the differences calculated between normal cells that do not include the abnormal cell. Furthermore, as the internal short circuit in the abnormal cell gradually progresses, the voltage difference values ​​ΔV21 and ΔV32 between the normal cell and the abnormal cell gradually increase.

[0056] 7, at timing t1, the voltage difference value ΔV21 is equal to or greater than the positive threshold value TH11, and the voltage difference value ΔV32 is equal to or less than the negative threshold value TH12. As a result, it is determined that a predetermined deviation has occurred in the voltage change amount VA of the second cell C2 compared to the other battery cells 13, and the second cell C2 is determined to be abnormal. In this case, when an internal short circuit has occurred in the battery cell 13, the diffusion resistance fluctuates gradually and the voltage fluctuation in the abnormal cell is small, but by comparing the cells relative to each other, it is possible to quickly determine the difference between the abnormal cell and the normal cell.

[0057] 7 shows a voltage difference value ΔV43 as a comparative example. The voltage difference value ΔV43 is the difference between the voltage changes VA3 and VA4 of cells C3 and C4, both of which are normal cells, and is a value that does not exceed the thresholds TH11 and TH12. Although not shown, the changes in the cell voltage V and voltage change VA of cell C4 are the same as those of cells C1 and C3.

[0058] Furthermore, the voltage difference value ΔVi+1,i is accumulated for each battery cell 13 to calculate the accumulated difference value QAi+1,i. As described with reference to FIG. 6 , when the accumulated difference value QAi+1,i is used as a parameter for abnormality determination, if the accumulated difference values ​​QA21 and QA32 are both equal to or greater than the threshold value TH2 at timing t2, the second cell C2 is determined to be abnormal. The accumulated difference value QAi+1,i is calculated continuously over a period that includes charging and discharging of the battery module 11 and periods when no current is being applied. The accuracy of abnormality detection is improved by performing abnormality detection based on the accumulated difference value QAi+1,i. Even if an equalization process is performed to equalize the cell voltages of each battery cell 13 in the battery module 11, the difference in the voltage change amount VA between the battery cells 13 can be cumulatively determined, allowing for earlier and more accurate detection of signs of an abnormality.

[0059] 7 shows a differential integrated value QA43 as a comparative example. The differential integrated value QA43 is an integrated value obtained by integrating the voltage difference value ΔV43 of cells C3 and C4, both of which are normal cells, and is a value that does not exceed the threshold value TH2.

[0060] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0061] In the battery module 11, abnormality detection for each battery cell 13 is performed not as an individual cell, but as a relative abnormality detection with respect to other battery cells 13. Therefore, even if voltage fluctuations or noise occur in the current path of the battery module 11, the effects of these fluctuations can be suppressed while abnormality detection is performed. Furthermore, erroneous detection due to environmental conditions such as temperature in the battery module 11 is suppressed. Therefore, when an internal short circuit occurs as the initial stage of thermal runaway, even if the diffusion resistance of the battery cell 13 fluctuates slowly over time, a difference in the voltage change amount VA(tm) between normal and abnormal cells can be found early, and the abnormal cell can be properly detected. As a result, an internal short circuit abnormality in a battery cell 13, which is a sign of thermal runaway, can be detected quickly and accurately.

[0062] For a target cell of the battery module 11, the difference in voltage change VA(tm) between the target cell and two or more different battery cells 13 is calculated as a voltage difference value ΔV(tm), and based on the voltage difference value ΔV(tm), it is determined whether a predetermined deviation has occurred in the voltage change VA(tm) of the target cell relative to the battery cells 13 other than the target cell. In this case, if an abnormal cell is included among the battery cells 13 of the battery module 11, a difference will occur between the voltage difference value ΔV(tm) calculated using the voltage change VA(tm) of two normal cells and the voltage difference value ΔV(tm) calculated using the voltage change VA(tm) of two cells including the abnormal cell. Therefore, an abnormality in the target cell can be properly detected.

[0063] For the target cell Ci, abnormality is detected based on the fact that the polarities of the voltage difference values ​​ΔVi,i-1(tm) and ΔVi+1,i(tm) are opposite to each other and the absolute values ​​of the voltage difference values ​​ΔVi,i-1(tm) and ΔVi+1,i(tm) are each equal to or greater than a threshold value. This allows for accurate detection of abnormal cells while taking into account the difference in voltage changes between normal and abnormal cells.

[0064] In an abnormal cell where an internal short circuit has occurred, the voltage change amount VA(tm) is larger than the voltage change amount VA(tm) of a normal cell, and this state continues throughout the charging and discharging of the battery module 11. Therefore, the accuracy of determining an internal short circuit can be improved by continuously monitoring the voltage difference value ΔV(tm) in each battery cell 13. In this regard, the accuracy of abnormality detection can be improved by using the differential integrated value QAi+1,i(tm), which is the integrated value of the voltage difference value ΔV(tm) calculated in each battery cell 13, as a parameter for abnormality determination.

[0065] Hereinafter, other embodiments different from the first embodiment will be described, focusing on the differences from the first embodiment.

[0066] Second Embodiment First, an overview of cell abnormality detection in this embodiment will be described using Fig. 8. Fig. 8 shows five battery cells 13 (cells Ci-2, Ci-1, Ci, Ci+1, and Ci+2) in a battery module 11, and the voltage changes from the initial value during charging and discharging of each of cells Ci-2 to Ci+2 are VAi-2(tm) to VAi+2(tm). Furthermore, the voltage difference value ΔV(tm), which is the difference in the absolute value of the voltage change amount VA(tm), for each two battery cells 13 adjacent to each other in the series path, is, in order from the low potential side, ΔVi-1,i-2(tm), ΔVi,i-1(tm), ΔVi+1,i(tm), and ΔVi+2,i+1(tm), and further, the double difference value ΔΔV(tm), which is the difference between the voltage difference values ​​ΔV(tm), is, in order from the low potential side, ΔΔVi,i-1,i-2(tm), ΔΔVi+1,i,i-1(tm), and ΔΔVi+2,i+1,i(tm). The two-time difference value ΔΔVi+1,i,i-1(tm) is calculated from the voltage change amounts VAi--1(tm), VAi(tm), and VAi+1(tm) of each of the three consecutive battery cells 13 connected in series.

[0067] In this case, if "cell Ci" of the five cells Ci-2 to Ci+2 is determined to be an abnormal cell, the voltage change amount VAi(tm) of cell Ci will be a value that is larger on the negative side than the voltage change amounts VA(tm) of the other cells. Therefore, of the voltage difference values ​​ΔV(tm), which are the difference in absolute values ​​of the voltage change amounts VA(tm) of two cells, the voltage difference value ΔVi,i-1(tm) between the abnormal cell (cell Ci) and its adjacent negative cell will be a positive value, the voltage difference value ΔVi+1,i(tm) between the abnormal cell (cell Ci) and its adjacent positive cell will be a negative value, and the other voltage difference values ​​ΔVi-1,i-2(tm) and ΔVi+2,i+1(tm) will be approximately zero.

[0068] Furthermore, among the two-time difference values ​​ΔΔV(tm), ΔΔV(tm) is calculated by subtracting the positive value ΔV(tm) from the negative value ΔV(tm). Therefore, the two-time difference value ΔΔV(tm) is an extremely large negative value, and the difference from the other two-time difference values ​​ΔΔV(tm) is significant. In other words, the two-time difference value ΔΔV(tm) is an indicator that clearly indicates the deviation of the voltage change amount VA(tm) in the abnormal cell. In this embodiment, the two-time difference value ΔΔV(tm) is used as a parameter for determining abnormality, thereby enabling appropriate detection of abnormal cells.

[0069] FIG. 9 is a flowchart showing the procedure of the abnormality detection process for the battery cell 13 in this embodiment. This process is executed by the battery ECU 20.

[0070] 9, in step S301, the cell voltage V(tm) of each battery cell 13 at time tm is obtained. In step S302, a voltage change VA(tm), which is the amount of change in cell voltage from the initial value, is calculated for each battery cell 13. In the subsequent step S303, the absolute value of the voltage change VA(tm) is calculated. In addition, in step S304, the difference in the absolute values ​​of the voltage change VA(tm) between two adjacent battery cells 13 in a series path is calculated as a voltage difference value ΔV(tm). Note that steps S301 to S304 are the same processes as steps S101 to S104 in FIG. 5.

[0071] Thereafter, in step S305, the difference between two voltage difference values ​​ΔVi+1,i(tm), ΔVi,i-1(tm) that are adjacent in the series arrangement order of the battery cells 13 is calculated as a second difference value ΔΔVi+1,i,i-1(tm). The second difference value ΔΔVi+1,i,i-1(tm) may be calculated using the following equation (2): ΔΔVi+1,i,i-1(tm) = ΔVi+1,i(tm) - ΔVi,i-1(tm) (2) The second difference value ΔΔVi+1,i,i-1(tm) is calculated for all combinations of battery cells 13 that form a series triplet in the battery module 11.

[0072] Thereafter, in step S306, it is determined whether the two-time difference value ΔΔVi+1,i,i-1(tm) is equal to or less than a predetermined negative threshold value TH3. If the two-time difference value ΔΔVi+1,i,i-1(tm) is not equal to or less than the negative threshold value TH3 in all the battery cells 13, the result in step S306 is negative, and after incrementing m by 1 in step S307, the process returns to step S301. If the two-time difference value ΔΔVi+1,i,i-1(tm) is equal to or less than the negative threshold value TH3 in any of the battery cells 13, the result in step S306 is positive, and the process proceeds to step S308.

[0073] In step S308, it is determined that an abnormality has occurred in the battery cell 13 for which the condition in step S306 is satisfied. In other words, it is determined that a predetermined deviation has occurred in the voltage change amount VA(tm) of the target cell compared to the other battery cells 13. Thereafter, in step S309, it is notified that an abnormality has occurred.

[0074] The abnormality detection process of Fig. 9 can be modified as shown in Fig. 10. The process of Fig. 10 is a partial modification of the process of Fig. 9, and steps S401 to S402 are different from those of Fig. 9.

[0075] In FIG. 10, as explained above, in steps S301 to S304, the voltage difference value ΔV i+1,i (tm) is calculated every time tm, and in step S305, the difference value ΔΔV i+1,i,i-1 (tm) is calculated twice.

[0076] Then, in step S401, the two-time difference values ​​ΔΔV(tm) calculated every time tm are integrated to calculate the two-time difference integrated value QBi+1,i,i-1(tm). In addition, in step S402, it is determined whether the two-time difference integrated value QBi+1,i,i-1(tm) is equal to or greater than a predetermined threshold value TH4 for all combinations of three consecutive series-connected battery cells 13 in the battery module 11. The threshold value TH4 is a positive threshold value.

[0077] If the two-time difference value ΔΔV(tm) is not equal to or greater than the threshold value TH4 for any of the battery cells 13, the result in step S402 is negative, m is incremented by 1 in step S307, and the process returns to step S301. If the two-time difference value ΔΔV(tm) is equal to or greater than the threshold value TH4 for any of the battery cells 13, the result in step S402 is positive, and the process proceeds to step S308. In step S308, it is determined that an abnormality has occurred in the battery cell 13, and in step S309, a notification of the occurrence of the abnormality is issued.

[0078] If the central battery cell 13 (cell Ci) of three consecutive battery cells 13 connected in series becomes an abnormal cell due to an internal short circuit, the voltage change amount VAi(tm) of the abnormal cell will be larger than that of the normal cells, and the voltage difference value ΔVi,i-1(tm) calculated between the abnormal cell and its adjacent negative electrode will be opposite in polarity to the voltage difference value ΔVi+1,i(tm) calculated between the abnormal cell and its adjacent positive electrode. Therefore, the double difference value ΔΔVi+1,i,i-1(tm), calculated as the difference between the voltage difference value ΔVi,i-1(tm) and the voltage difference value ΔVi+1,i(tm) for three consecutive battery cells 13 connected in series, clearly indicates the deviation of the voltage change amount VAi(tm) of the abnormal cell. In this regard, by using the two-time difference value ΔΔV i+1,i,i-1 (tm) calculated from the voltage change amount VA(tm) of three consecutive battery cells 13 connected in series as a parameter for abnormality determination, abnormal cells can be properly detected.

[0079] When an internal short circuit occurs in an abnormal cell, the polarity of the voltage difference value ΔV(tm) calculated between the abnormal cell and its negative adjacent cell and the polarity of the voltage difference value ΔV(tm) calculated between the abnormal cell and its positive adjacent cell remain reversed. Therefore, continuously monitoring the two-time difference value ΔΔV(tm), which is the difference between these voltage difference values ​​ΔV(tm) and ΔV(tm), improves the accuracy of internal short circuit detection. In this regard, the accuracy of abnormality detection can be improved by using the two-time difference integrated value QBi(tm), which is the integrated value of the two-time difference value ΔΔV(tm), as a parameter for abnormality detection.

[0080] (Third embodiment) In this embodiment, the degree of deviation of the voltage change amount VA(tm) of a target cell from the average value of the voltage change amount VA(tm) of each battery cell 13 in the battery module 11 is calculated as the deviation degree, and based on the deviation degree, it is determined whether or not a predetermined deviation occurs in the voltage change amount VA(tm) of the target cell relative to battery cells 13 other than the target cell.

[0081] Furthermore, if an internal short circuit occurs in any of the battery cells 13 in the battery module 11, this will affect the average value of the voltage change VA(tm) of each battery cell 13. In this case, there is a concern that the detection accuracy will decrease when detecting an abnormality in a target cell based on the degree of deviation of the voltage change VA(tm) of the target cell from the average value of the voltage change VA(tm) of each battery cell 13. Therefore, in this embodiment, the average value of the voltage change VA(tm) of the remaining battery cells 13 excluding one battery cell 13 (target cell) among the multiple battery cells 13 in the battery module 11 is used as a reference, and the degree of deviation of the voltage change VA(tm) of the target cell is calculated, and abnormality detection is performed based on the degree of deviation.

[0082] FIG. 11 is a flowchart showing the procedure of the abnormality detection process for the battery cell 13 in this embodiment. This process is executed by the battery ECU 20.

[0083] 11, in step S501, the cell voltage V(tm) of each battery cell 13 at time tm is acquired, and in step S502, the voltage change amount VA(tm), which is the amount of change in cell voltage from the initial value, is calculated for each battery cell 13. Note that steps S501 and S502 are the same processes as steps S101 and S102 in FIG.

[0084] Thereafter, in step S503, an average value μ(tm) of the voltage change amount VA(tm) is calculated for each battery cell 13 in the battery module 11. In this embodiment, when each battery cell 13 in the battery module 11 is set as a target cell for abnormality detection, the average value μ(tm) of the voltage change amount VA(tm) is calculated without using the voltage change amount VA(tm) of the target battery cell 13, in other words, the voltage change amount VA(tm) of the target battery cell 13 is excluded. At this time, the average value μ(tm) is calculated using each voltage change amount VA(tm) that is a combination of the number of cells.

[0085] For example, if the target cell is cell C1, the voltage change amount VA1(tm) of cell C1 is excluded and the average value μ1(tm) is calculated using the remaining voltage change amount VA(tm). Also, if the target cell is cell C2, the voltage change amount VA2(tm) of cell C2 is excluded and the average value μ2(tm) is calculated using the remaining voltage change amount VA(tm).

[0086] In step S504, the standard deviation σ(tm) of the voltage change VA(tm) for each battery cell 13 in the battery module 11 is calculated. The standard deviation σ(tm) may be calculated by taking the square root of the variance, which is the root mean square of the difference between the voltage change VA(tm) of each battery cell 13 and the average value μ(tm). In this embodiment, the standard deviation σ(tm) of the voltage change VA(tm) is calculated without using the voltage change VA(tm) of the target battery cell 13, but using the voltage change VA(tm) of each remaining battery cell 13 other than the target cell and the average value μ(tm) calculated excluding the target cell. In this case, the standard deviation σ(tm) is calculated using each voltage change VA(tm) that is a combination of the number of cells.

[0087] For example, if the target cell is cell C1, the standard deviation σ1(tm) is calculated using the voltage change VA(tm) of cells other than cell C1 and the average μ1(tm) calculated excluding the voltage change VA1(tm) of cell C1. Also, if the target cell is cell C2, the standard deviation σ2(tm) is calculated using the voltage change VA(tm) of cells other than cell C2 and the average μ2(tm) calculated excluding the voltage change VA2(tm) of cell C2.

[0088] In step S505, for each battery cell 13 that is the target cell, the ratio of the absolute value of the difference between the voltage change amount VAi(tm) and the average value μi(tm) to the standard deviation σi(tm) is calculated as the deviation degree Ri(tm). The deviation degree Ri(tm) is calculated using the following equation (3): Ri(tm) = |VAi(tm) - μi(tm)| / σi(tm) ... (3) The deviation degree Ri(tm) indicates the degree to which the voltage change amount VA(tm) of the target cell deviates from the average value of the voltage change amounts VA(tm) of each battery cell 13. The deviation degree Ri(tm) also indicates the ratio of the deviation (VAi(tm) - μi(tm)) to the standard deviation σi(tm) for each battery cell 13.

[0089] Then, in step S506, it is determined whether the deviation degree Ri(tm) is equal to or greater than a predetermined threshold value TH5 for all battery cells 13. The threshold value TH5 is a positive threshold value. If the deviation degree Ri(tm) is not equal to or greater than the threshold value TH5 for all battery cells 13, the result in step S506 is negative, and in step S507, m is incremented by 1, and the process returns to step S501. If the deviation degree Ri(tm) is equal to or greater than the threshold value TH5 for any battery cell 13, the result in step S506 is positive, and the process proceeds to step S508. In step S508, it is determined that an abnormality has occurred for the battery cell 13 for which the condition in step S506 is met. Then, in step S509, a notification is issued to the effect that an abnormality has occurred.

[0090] The abnormality detection process of Fig. 11 can also be modified as shown in Fig. 12. The process of Fig. 12 is a partial modification of the process of Fig. 11, and steps S601 to S602 are different from those of Fig. 11.

[0091] 12 , as described above, in steps S501 and S502, the voltage change amount VA(tm) is calculated for each time tm. In step S503, the average value μ(tm) of the voltage change amount VA(tm) is calculated for each battery cell 13 in the battery module 11. In step S504, the standard deviation σ(tm) of the voltage change amount VA(tm) for each battery cell 13 is calculated. In step S505, for each battery cell 13 that is a target cell, the ratio of the absolute value of the difference between the voltage change amount VA(tm) and the average value μ(tm) to the standard deviation σ(tm) is calculated as the deviation degree Ri(tm). In this case, as described above, the average value μ(tm) and the standard deviation σ(tm) are calculated excluding the voltage change amount VA(tm) of the target battery cell 13.

[0092] Then, in step S601, the deviation degree Ri(tm) is integrated to calculate the integrated deviation degree value QCi(tm) for each battery cell 13. In step S602, it is determined whether the integrated deviation degree value QCi(tm) is equal to or greater than a predetermined threshold value TH6. The threshold value TH6 is a positive threshold value.

[0093] If the deviation degree integrated value QCi(tm) is not equal to or greater than the threshold value TH6 in any of the battery cells 13, the result in step S602 is negative, m is incremented by 1 in step S507, and the process returns to step S501. If the deviation degree integrated value QCi(tm) is equal to or greater than the threshold value TH6 in any of the battery cells 13, the result in step S602 is positive, and the process proceeds to step S508. In step S508, it is determined that an abnormality has occurred in the battery cell 13, and in step S509, a notification of the occurrence of the abnormality is issued.

[0094] The average value of the voltage change amount VA(tm) of the remaining battery cells 13 excluding the target cell among the plurality of battery cells 13 in the battery module 11 is used as a reference, and the degree of deviation of the voltage change amount VA(tm) of the target cell is calculated, and the degree of deviation is used as an abnormality determination parameter, thereby improving the accuracy of abnormality detection.

[0095] In an abnormal cell where an internal short circuit has occurred, the deviation of the voltage change amount VA(tm) continues to be relatively large, so the accuracy of abnormality detection can be improved by using the integrated deviation amount QCi(tm), which is the integrated value of the deviation amount Ri(tm), as a parameter for abnormality determination. In addition, the integrated deviation amount QCi(tm) is calculated based on the average value of the voltage change amount VA of the battery cells 13 excluding the target cell, which makes it possible to further improve the accuracy of abnormality detection.

[0096] The abnormality detection process of Fig. 11 can be modified as shown in Fig. 13. The process of Fig. 13 is a partial modification of the process of Fig. 11, and steps S611 to S613 are different from the process of Fig. 11.

[0097] 13, in steps S501 to S504, the same processing as in Fig. 11 is performed to calculate the average value μi(tm) of the voltage change amount VA(tm) and the standard deviation σi(tm) of the voltage change amount VA(tm) for each battery cell 13. In this case, as described above, the average value μi(tm) and the standard deviation σi(tm) are calculated excluding the voltage change amount VA(tm) of the battery cell 13 that is the target cell.

[0098] Thereafter, in step S611, a deviation Di(tm) is calculated, which is the difference between the voltage change amount VA(tm) and the average value μ(tm) for each battery cell 13. At this time, the deviation Di(tm) is calculated for each target battery cell 13 using the average value μ(tm) of the voltage change amount VA(tm) of the battery cells 13 excluding the target cell. Furthermore, in step S612, the absolute values ​​of the deviation Di(tm) are integrated to calculate an integrated deviation value QDi(tm). Note that step S611 corresponds to the "deviation calculation unit," and step S612 corresponds to the "integrated value calculation unit."

[0099] In step S613, it is determined for each battery cell 13 whether the deviation integrated value QDi(tm) is equal to or greater than a threshold value (K×σi(tm)) formed by the product of the standard deviation σi(tm) and a predetermined coefficient K.

[0100] If the deviation integrated value QDi(tm) is not equal to or greater than the threshold value for any of the battery cells 13, the result in step S613 is negative, m is incremented by 1 in step S507, and the process returns to step S501. If the deviation integrated value QDi(tm) is equal to or greater than the threshold value for any of the battery cells 13, the result in step S613 is positive, and the process proceeds to step S508. In step S508, it is determined that an abnormality has occurred in that battery cell 13, and in step S509, a notification of the occurrence of the abnormality is issued.

[0101] If an internal short circuit occurs in any of the battery cells 13 in the battery module 11, this will affect the average value μ(tm) and standard deviation σ(tm) of the voltage change amount VA(tm) of each battery cell 13. In this case, there is a concern that the detection accuracy may be reduced when detecting an abnormality in a target cell by comparing the integrated deviation value QD(tm) of the voltage change amount VA(tm) of each battery cell 13 with a threshold value set based on the standard deviation σ(tm). In this regard, the deviation D(tm) is calculated using the average value μ(tm) of the voltage change amount VA(tm) of the remaining battery cells 13 excluding the target cell, and the standard deviation σ(tm) is calculated using the voltage change amount VA(tm) of the remaining battery cells 13 excluding the target cell. This improves the accuracy of abnormality detection.

[0102] Fourth Embodiment In this embodiment, a difference calculation is performed twice based on the voltage change amounts VAi+1(tm), VAi(tm), and VAi-1(tm) of three consecutive battery cells 13 connected in series among a plurality of battery cells 13 to calculate a two-time difference value ΔΔVi+1,i,i-1(tm), and the degree of deviation of the two-time difference value ΔΔVi+1,i,i-1(tm) from the average value of the two-time difference values ​​ΔΔV(tm) is calculated, and an abnormality in the target cell is detected based on the degree of deviation.

[0103] In such a case, if an internal short circuit occurs in any of the battery cells 13 in the battery module 11, the voltage difference value ΔV(tm) between the combination of battery cells 13, including the abnormal cell, will be different from the voltage difference value ΔV(tm) between the combination of normal cells. This will change the average value of the two-time difference values ​​ΔΔV(tm). In this case, the accuracy of the degree of deviation of the two-time difference value ΔΔV(tm) of the target cell from the average value of the two-time difference values ​​ΔΔV(tm) will decrease, raising concerns about a decrease in the accuracy of anomaly detection based on the degree of deviation.

[0104] Therefore, in this embodiment, when calculating the two-time difference value ΔΔV(tm) by treating each battery cell 13 of the battery module 11 as a designated cell, the two-time difference value ΔΔV(tm) calculated by treating the target cell as a designated cell is set as a specific two-time difference value. Then, of the two-time difference values ​​ΔΔV(tm) calculated by treating each battery cell 13 of the battery module 11 as a designated cell, the degree of deviation of the specific two-time difference value from the average value of the remaining two-time difference values ​​ΔΔV(tm) excluding the specific two-time difference value is calculated as the deviation degree.

[0105] FIG. 14 is a flowchart showing the procedure of the abnormality detection process for the battery cell 13 in this embodiment. This process is executed by the battery ECU 20.

[0106] 14, in step S701, the cell voltage V(tm) of each battery cell 13 at time tm is obtained. In step S702, a voltage change VA(tm), which is the amount of change in cell voltage from the initial value, is calculated for each battery cell 13. In the subsequent step S703, the absolute value of the voltage change VA(tm) is calculated. In addition, in step S704, a voltage difference value ΔV(tm) is calculated, and in step S705, a double difference value ΔΔV(tm) is calculated. Note that steps S701 to S705 are processes similar to steps S301 to S305 in FIG. 9.

[0107] In this embodiment, in step S704, each battery cell 13 in the battery module 11 is designated as a designated cell, and a voltage difference value ΔV(tm), which is the difference in the voltage change VA(tm) between the designated cell and a first adjacent cell on the negative side, and a voltage difference value ΔV(tm), which is the difference in the voltage change VA(tm) between the designated cell and a second adjacent cell on the positive side, are calculated by subtraction in ascending or descending order of the serial connection of the cells. In addition, in step S705, two difference values ​​ΔΔV(tm) are calculated for all combinations in which the designated cell is the central battery cell 13 in a series of three.

[0108] Thereafter, in step S706, an average value μAi(tm) of the two-time difference values ​​ΔΔV(tm) calculated by treating each battery cell 13 of the battery module 11 as a designated cell is calculated. Specifically, from the two-time difference values ​​ΔΔV(tm) calculated by treating each battery cell 13 as a designated cell, the two-time difference values ​​ΔΔVi+1,i,i-1(tm) calculated by treating the target cell (cell Ci) as the designated cell, i.e., the specific two-time difference values, are excluded to calculate the average value μAi(tm) of the two-time difference values ​​ΔΔV(tm). In step S706, multiple average values ​​μAi(tm) are calculated for all possible combinations of battery modules 11.

[0109] In step S707, the standard deviation σAi(tm) of the two-time difference values ​​ΔΔV(tm) calculated for each battery cell 13 in the battery module 11 is calculated. The standard deviation σAi(tm) may be calculated as the square root of the variance, which is the root mean square of the difference between the two-time difference values ​​ΔΔV(tm) calculated for each battery cell 13 as a designated cell and the average value μAi(tm). Specifically, when the two-time difference value ΔΔVi+1,i,i-1(tm) calculated for the target cell (cell Ci) as a designated cell is set as a specific two-time difference value, the standard deviation σAi(tm) of the two-time difference value ΔΔV(tm) other than the specific two-time difference value is calculated using the two-time difference values ​​ΔΔV(tm) calculated for each battery cell 13 as a designated cell, and the average value μAi(tm) calculated excluding the specific two-time difference value. In step S707, a plurality of standard deviations σAi(tm) are calculated for all combinations of the battery modules 11.

[0110] In step S708, the ratio of the absolute value of the difference between the two-time difference value ΔΔV(tm) and the average value μA(tm) to the standard deviation σA(tm) is calculated as the deviation degree RA(tm) for each battery cell 13. The deviation degree RA(tm) is calculated using the following equation (4). RAi(tm) = |ΔΔVi+1,i,i-1(tm) - μAi(tm)| / σAi(tm) ... (4) In steps S706 to S708, when the two-time difference value ΔΔVi+1,i,i-1(tm) calculated using the target cell (cell Ci) as the designated cell is set as the specific two-time difference value, the degree of deviation RAi(tm) is calculated as the deviation degree RAi(tm) from the average value of the remaining two-time difference values ​​ΔΔV(tm) excluding the specific two-time difference value among the two-time difference values ​​ΔΔV(tm) calculated using each battery cell 13 as the designated cell one by one.

[0111] Thereafter, in step S709, it is determined whether or not the deviation degree RAi(tm) is equal to or greater than a predetermined threshold value TH7 for all the battery cells 13. The threshold value TH7 is a positive threshold value.

[0112] If the deviation RAi(tm) for all battery cells 13 is not equal to or greater than the threshold value TH7, the result in step S709 is negative, m is incremented by 1 in step S710, and the process returns to step S701. If the deviation RAi(tm) for any battery cell 13 is equal to or greater than the threshold value TH7, the result in step S709 is positive, and the process proceeds to step S711. In step S711, it is determined that an abnormality has occurred in the battery cell 13 for which the condition in step S709 is met. Then, in step S712, a notification is issued to the effect that an abnormality has occurred.

[0113] Of the two-time difference values ​​ΔΔV(tm) calculated for each battery cell as a designated cell, the specific two-time difference value (the two-time difference value calculated for the target cell) is excluded from the average of the remaining two-time difference values ​​ΔΔV(tm), and the degree of deviation of the specific two-time difference value is used as the abnormality determination parameter. Here, if the target cell is an abnormal cell, the specific two-time difference value ΔΔV(tm) is the two-time difference value that is affected by fluctuations in the voltage change amount VA(tm) of the abnormal cell, and by excluding this specific two-time difference value from the calculation of the average value μi(tm) and standard deviation σi(tm), the accuracy of abnormality detection can be improved.

[0114] The abnormality detection process of Fig. 14 can also be modified as shown in Fig. 15. The process of Fig. 15 is a partial modification of the process of Fig. 14, in which steps S706 to S707 of Fig. 14 are replaced by steps S706a to S707a.

[0115] In steps S706a to S707a, of the two-time difference values ​​ΔΔV(tm) calculated using each battery cell 13 as a designated cell, the degree of deviation of the specific two-time difference value from the average value of the remaining two-time difference values ​​ΔΔV(tm), excluding the specific two-time difference value and the two-time difference values ​​calculated using the first adjacent cell and the second adjacent cell as designated cells, is calculated as the deviation degree RAi(tm).

[0116] For convenience, the specific two-time difference value (the two-time difference value ΔΔVi+1,i,i-1(tm) calculated using the target cell as the designated cell) and the two-time difference values ​​ΔΔVi,i-1,i-2(tm), ΔΔVi+2,i+1,i(tm) calculated using the first adjacent cell and the second adjacent cell, respectively, are collectively referred to as the "specific two-time difference value group X."

[0117] In step S706a, the specific group of two-time difference values ​​X (ΔΔVi,i-1,i-2(tm), ΔΔVi+1,i,i-1(tm), ΔΔVi+2,i+1,i(tm)) is excluded from the two-time difference values ​​ΔΔV(tm) calculated for each battery cell 13 as a designated cell, and the average value μAi(tm) of the two-time difference values ​​ΔΔV(tm) is calculated.

[0118] In step S707a, the standard deviation σAi(tm) of the two-time difference values ​​ΔΔV(tm) is calculated using the two-time difference values ​​ΔΔV(tm) other than the specific two-time difference value group X (ΔΔVi,i-1,i-2(tm), ΔΔVi+1,i,i-1(tm), ΔΔVi+2,i+1,i(tm)) out of the two-time difference values ​​ΔΔV(tm) calculated for each battery cell 13 as a designated cell, and the average value μAi(tm) calculated excluding the specific two-time difference value group X.

[0119] Thereafter, the deviation RAi(tm) is calculated in the same manner as above, and an abnormality determination is made for each battery cell 13 based on the deviation RAi(tm) (steps S708, S709).

[0120] If the target cell is an abnormal cell, the specific two-time difference value group X (the specific two-time difference value and the two-time difference values ​​calculated using the first adjacent cell and the second adjacent cell as designated cells) is the two-time difference value ΔΔV(tm) that is affected by the fluctuation of the voltage change amount VA(tm) of the abnormal cell, and the accuracy of abnormality detection can be improved by excluding this specific two-time difference value group X from the calculation of the average value μi(tm) and standard deviation σi(tm).

[0121] The abnormality detection process of Fig. 14 can be modified as shown in Fig. 16. The process of Fig. 16 is a partial modification of the process of Fig. 14, and steps S801 to S802 are different from the process of Fig. 14.

[0122] 16, after calculating the deviation degree RAi(tm), in step S801, the deviation degree RAi(tm) calculated for each time tm is integrated to calculate the integrated deviation degree value QEi(tm). In addition, in step S802, it is determined whether the integrated deviation degree value QEi(tm) is equal to or greater than a predetermined threshold value TH8. The threshold value TH8 is a positive threshold value.

[0123] If the deviation degree integrated value QEi(tm) is not equal to or greater than the threshold value TH8 in any of the battery cells 13, the result in step S802 is negative, m is incremented by 1 in step S710, and the process returns to step S701. If the deviation degree integrated value QEi(tm) is equal to or greater than the threshold value TH8 in any of the battery cells 13, the result in step S802 is positive, and the process proceeds to step S711. In step S711, it is determined that an abnormality has occurred in the battery cell 13, and in step S712, a notification of the occurrence of the abnormality is issued.

[0124] Fifth Embodiment In this embodiment, in a configuration in which each battery cell 13 of a battery pack B is divided into a plurality of battery cell groups, a provisional determination of an abnormality is made for all battery cell groups as a first stage of abnormality detection, and a final determination of an abnormality is made for battery cell groups that have been provisionally determined to have an abnormality as a second stage.

[0125] Fig. 17 is a diagram showing the configuration of a battery system according to this embodiment. In a battery unit 10, battery cell groups G1, G2, ... Gn are configured, each consisting of a plurality of battery cells 13 connected in series. Each battery cell group G1 to Gn is made up of three or more battery cells 13 connected in series. For example, each battery module 11 shown in Fig. 1 may be a battery cell group G1 to Gn. In the battery unit 10 shown in Fig. 17, a monitoring device 12 is provided for each battery cell group G1 to Gn. However, a configuration in which one monitoring device 12 is provided for two or more battery cell groups G1 to Gn may also be used.

[0126] In this embodiment, the battery ECU 20 includes an acquisition unit 51, a parameter change amount calculation unit 52, a provisional abnormality determination unit 53, an abnormality detection unit 54, and a voltage adjustment unit 55. The acquisition unit 51 acquires, from each monitoring device 12, the cell voltage V (detected state value) of each battery cell 13 detected by the voltage sensor 31 (state detection unit) in each battery cell group G1 to Gn. The parameter change amount calculation unit 52 calculates, for each battery cell group G1 to Gn, a voltage change amount VA (parameter change amount), which is the amount of change in the cell voltage V acquired by the acquisition unit 51 over a predetermined period. The provisional abnormality determination unit 53 makes a provisional abnormality determination for each battery cell 13 for each battery cell group G1 to Gn based on the voltage change amount VA. The abnormality detection unit 54 performs abnormality detection on each of the battery cells 13 in a battery cell group G1 to Gn that includes a battery cell 13 that has been provisionally determined to be abnormal by the provisional abnormality determination unit 53, by treating each battery cell 13 as a target cell for abnormality detection.

[0127] In this embodiment, the execution condition for abnormality detection is that the terminal voltages of the battery cells 13 in each of the battery cell groups G1 to Gn are adjusted to the same voltage. When this execution condition is met, abnormality detection is performed for each battery cell 13 (target cell). Specifically, the battery ECU 20 has an equalization function that adjusts the terminal voltages of the battery cells 13 to the same voltage. After the equalization process (cell balancing process) for each battery cell 13 is performed, the battery ECU 20 performs abnormality detection using the cell voltages of each battery cell 13. The voltage adjustment unit 55 performs voltage equalization by discharging or charging each battery cell 13. For example, the voltage adjustment unit 55 performs the equalization process when there is a variation in the terminal voltages of the battery cells 13 while the vehicle is stopped (parked). Alternatively, the voltage adjustment unit 55 performs the equalization process periodically, i.e., at a predetermined cycle.

[0128] Fig. 18 is a flowchart showing the procedure for the abnormality detection process for the battery cells 13 in this embodiment, and this process is executed by the battery ECU 20. Fig. 18 is a partial modification of Fig. 5 described above, and the same steps as Fig. 5 are assigned the same step numbers to simplify the explanation. The process in Fig. 18 is executed for each battery cell group. Note that the process in Fig. 18 can be executed while the vehicle power switch is off, assuming that the equalization process is performed while the vehicle is stopped.

[0129] 18, in step S901, it is determined whether or not the equalization process has just been performed on each battery cell 13. For example, if the equalization process was performed while the vehicle was stopped, and the result of step S901 is before the next vehicle startup and before a predetermined time has elapsed since the execution of the equalization process, then the process proceeds to the subsequent step S101 on the condition that the result of step S901 is affirmative.

[0130] In steps S101 and S102, the cell voltage V(tm) of each battery cell 13 is acquired, and the voltage change amount VA(tm), which is the amount of change in the cell voltage V(tm) from the initial value (voltage initial value) for each battery cell 13, is calculated (VA(tm) = V(tm) - initial value).

[0131] Then, in step S902, a provisional determination is made as to whether or not each battery cell 13 has an abnormality based on the voltage change VA(tm) of each battery cell 13. Then, in the following step S903, it is determined whether or not the battery cell group currently being detected includes any battery cells 13 that are provisionally determined to have an abnormality. The processing in step S902 corresponds to the first stage of abnormality detection. At this time, the voltage change VA(tm) of each battery cell 13 in the battery cell group is compared with each other, and if a battery cell 13 with a large deviation is found, it is determined that the battery cell group including that battery cell 13 may have an abnormality. Specifically, the average value of the voltage change VA(tm) of each battery cell 13 in the battery cell group is calculated, and a battery cell 13 whose voltage change VA(tm) deviates from the average by a predetermined amount or more is provisionally determined to be an abnormal battery cell 13 (abnormal cell).

[0132] Then, in steps S103 and S104, the absolute value of the voltage change amount VA(tm) is calculated, and the difference between the absolute values ​​of the voltage change amount VA(tm) between two adjacent battery cells 13 in the series path is calculated as a voltage difference value ΔVi+1,i(tm) for all battery cells 13. In step S105, each battery cell 13 (cells C1 to Cn) is treated as a target cell, and the voltage difference value ΔVi,i-1(tm) and ΔVi+1,i(tm) for each target cell are compared with a predetermined threshold value. If the condition that the voltage difference value ΔVi,i-1(tm) is equal to or greater than the positive threshold value TH11 and the voltage difference value ΔVi+1,i(tm) is equal to or less than the negative threshold value TH12 is met for any battery cell 13 among all battery cells 13, the result in step S105 is affirmative, and the process proceeds to step S107. In step S107, it is determined that an abnormality has occurred in the battery cell 13 for which the condition in step S105 is met. The processing in steps S103 to S107 corresponds to the second stage of abnormality detection.

[0133] In the abnormality detection process of FIG. 18 , the second stage of abnormality detection (main determination) is configured to detect an abnormality in the battery cell 13 based on the voltage difference values ​​ΔV(tm) and ΔV(tm). However, this main determination process may be modified as follows.

[0134] (1) In each battery cell group, the absolute values ​​of the voltage difference values ​​ΔV(tm) calculated at each time tm may be accumulated to calculate the differential integrated values ​​QA(tm) and QA(tm), and abnormality detection (main determination) of the battery cells 13 may be performed based on these differential integrated values ​​QA(tm) and QA(tm) (see steps S202 and S203 in FIG. 6).

[0135] (2) In each battery cell group, the difference in the absolute values ​​of the voltage change amounts VA(tm) between two adjacent battery cells 13 in the series path may be calculated as a voltage difference value ΔVi+1,i(tm), and the difference between two adjacent voltage difference values ​​ΔVi+1,i(tm) and ΔVi,i-1(tm) in the series arrangement of the battery cells 13 may be calculated as a double difference value ΔΔVi+1,i,i-1(tm), and abnormality detection (main determination) of the battery cell 13 may be performed based on the double difference value ΔΔVi+1,i,i-1(tm) (see steps S304 to S306 in FIG. 9).

[0136] (3) In each battery cell group, the two-time difference value ΔΔV(tm) calculated at each time tm may be accumulated to calculate the two-time difference accumulated value QBi+1,i,i-1(tm), and abnormality detection (main determination) of the battery cell 13 may be performed based on the two-time difference accumulated value QBi+1,i,i-1(tm) (see steps S401 and S402 in FIG. 10).

[0137] Fig. 19 is a time chart showing changes in cell voltage in the battery pack B. For ease of explanation, Fig. 19 shows changes in cell voltage of two battery cells 13.

[0138] 19 , timings t1 and t2 are timings at which equalization processing is performed on each battery cell 13, and the cell voltages of each battery cell 13 are equalized after timings t1 and t2. For example, when equalization processing is performed at timing t1, period TA is a period immediately after equalization and before discharge, during which no discharge to the on-board rotating electric machine or the like is performed while the vehicle is running. The abnormality detection processing for the battery cells 13 may be started from period TA.

[0139] In the above embodiment, the voltage adjustment unit 55 is configured to perform voltage equalization processing of each battery cell 13 as the voltage adjustment processing, but this may be modified. For example, the voltage adjustment processing may be configured to cause a charging device to charge the battery pack B (each battery module 11) to a fully charged state. In this case, the battery ECU 20 may perform abnormality detection (main determination) of the target cell before a predetermined time has elapsed after the battery pack B (each battery module 11) has been fully charged. The charging device may be an external charging device provided outside the vehicle.

[0140] The configuration in which the condition for executing abnormality detection is that the terminal voltages of the battery cells 13 are adjusted to the same voltage can also be applied to abnormality detection processes other than those of this embodiment. For example, in the abnormality detection processes of the first to fourth embodiments, the condition for detecting abnormality in each battery cell 13 is that the terminal voltages of the battery cells 13 are adjusted to the same voltage, and the abnormality detection may be performed based on the voltage difference value ΔV, the two-time difference value ΔΔV, or the like.

[0141] In the embodiment described above, when detecting an abnormality in each battery cell 13, by combining provisional judgment and actual judgment as described above, it is possible to achieve proper abnormality detection while suppressing excessive computational load.

[0142] Furthermore, the system is configured to perform abnormality detection for the target cell on the condition that the terminal voltages of the battery cells 13 are adjusted to the same voltage by equalization processing, etc. In this case, false detection of abnormality for each battery cell 13 can be suppressed.

[0143] Sixth Embodiment In this embodiment, a configuration will be described in which abnormality detection is performed in two stages in the abnormality detection process of Fig. 11. Note that in this embodiment, a provisional abnormality determination is performed for each battery cell 13 in the battery pack B, rather than for each battery cell group.

[0144] Figure 20 is a flowchart showing the procedure for the process of detecting an abnormality in the battery cell 13 in this embodiment, and this process is executed by the battery ECU 20. Figure 20 is a partial modification of the above-mentioned Figure 11, and the same steps as in Figure 11 are assigned the same step numbers to simplify the explanation.

[0145] 20, in steps S501 and S502, the cell voltage V(tm) of each battery cell 13 is acquired, and the voltage change amount VA(tm), which is the amount of change in cell voltage from the initial value, is calculated for each battery cell 13.

[0146] Then, in step S1001, a provisional determination is made as to whether or not each battery cell 13 has an abnormality based on the voltage change VA(tm) of each battery cell 13. At this time, if there is any battery cell 13 for which the difference of the voltage change VA(tm) from the average value of the voltage change VA(tm) of each battery cell 13 is equal to or greater than a predetermined value, that battery cell 13 is provisionally determined to be an abnormal cell. In this embodiment, step S1001 corresponds to the "provisional abnormality determination unit."

[0147] Thereafter, in steps S503 to S506, the battery cells 13 provisionally determined to be abnormal in step S1001 are each treated as a target cell for abnormality detection, and it is determined whether a predetermined deviation has occurred in the target cell. In this case, in steps S503 to S506, not all battery cells 13 in the battery module 11 are treated as target cells for abnormality detection, but only the battery cells 13 provisionally determined to be abnormal are treated as target cells for abnormality detection.

[0148] Specifically, in step S503, the average value μ(tm) of the voltage change amount VA(tm) is calculated for all battery cells 13 in the battery module 11. At this time, when each battery cell 13 provisionally determined to be an abnormal cell in step S1001 is set as a target cell, the average value μ(tm) of the voltage change amount VA(tm) is calculated without using the voltage change amount VA(tm) of the target battery cell 13, in other words, excluding the voltage change amount VA(tm) of the target battery cell 13. In step S504, the standard deviation σ(tm) of the voltage change amount VA(tm) is calculated without using the voltage change amount VA(tm) of the target battery cell 13, but using the voltage change amount VA(tm) of each remaining battery cell 13 other than the target cell and the average value μ(tm) calculated excluding the target cell.

[0149] In step S505, the ratio of the absolute value of the difference between the voltage change amount VA(tm) and the average value μ(tm) to the standard deviation σ(tm) is calculated as the deviation degree Ri(tm) for each target battery cell 13. Then, in step S506, anomaly detection is performed for each target battery cell 13 based on the deviation degree Ri(tm).

[0150] 12 and 13, it is preferable to provisionally determine whether or not an abnormality exists in each battery cell 13 based on the voltage change amount VA(tm) of each battery cell 13, as in Fig. 20 (similar to step S1001). That is, in the abnormality detection processes of Fig. 12 and 13, it is preferable to execute the process of step S1001 between step S502 and step S503.

[0151] In the embodiment described above, a provisional abnormality determination is made for a plurality of battery cells 13 based on the difference between the average value of the voltage change amount VA (parameter change amount), and each provisionally determined abnormal cell is set as a target cell, and a final abnormality determination is made for the target cell. This makes it possible to achieve proper abnormality detection while suppressing excessive computational load.

[0152] Seventh Embodiment In this embodiment, in a configuration in which each battery cell 13 of a battery pack B is divided into a plurality of battery cell groups, a provisional determination of an abnormality is made for all battery cell groups as a first stage of abnormality detection, and a final determination of an abnormality is made for battery cell groups that have been provisionally determined to have an abnormality as a second stage.

[0153] Fig. 21 is a diagram showing the configuration of a battery system in this embodiment. In a battery unit 10, battery cell groups G1, G2, ... Gn are configured, each consisting of a plurality of battery cells 13 connected in series. Each battery cell group G1 to Gn is made up of three or more battery cells 13 connected in series to one another. For example, each battery module 11 shown in Fig. 1 may be a battery cell group G1 to Gn. In the battery unit 10 shown in Fig. 21, a monitoring device 12 is provided for each battery cell group G1 to Gn. However, a configuration in which one monitoring device 12 is provided for two or more battery cell groups G1 to Gn may also be used.

[0154] In this embodiment, the battery ECU 20 includes an acquisition unit 61 , a parameter change amount calculation unit 62 , a one-time difference value calculation unit 63 , a tentative abnormality determination unit 64 , a two-time difference value calculation unit 65 , and an abnormality detection unit 66 .

[0155] The acquisition unit 61 acquires the cell voltage V (detected state value) of each battery cell 13 detected by the voltage sensor 31 (state detection unit). The parameter change amount calculation unit 62 calculates a voltage change amount VA (parameter change amount), which is the amount of change in the cell voltage V acquired by the acquisition unit 51 over a predetermined period of time.

[0156] The one-time difference value calculation unit 63 calculates, as a one-time difference value, a voltage difference value ΔV which is the difference between the voltage change amount VA (parameter change amount) of a target cell that is the target of abnormality detection for each of the battery cell groups G1 to Gn and two or more different battery cells 13. The tentative abnormality determination unit 64 tentatively determines the presence or absence of an abnormality in each of the battery cells 13 for each of the battery cell groups G1 to Gn, based on the voltage difference value ΔV calculated by the one-time difference value calculation unit 63.

[0157] In a battery cell group among the multiple battery cell groups G1 to Gn that has been provisionally determined to have an abnormality by the abnormality provisional determination unit 64, the two-time difference value calculation unit 65 determines the battery cell 13 adjacent to the negative electrode side of the target cell as a first adjacent cell and the battery cell 13 adjacent to the positive electrode side of the target cell as a second adjacent cell, and calculates the change amount difference values ​​between each of these adjacent cells and the target cell by subtraction in ascending or descending order of the cell serial order to obtain first and second difference values, and also calculates the difference between the first and second difference values ​​as a two-time difference value ΔΔV. The procedure for calculating the voltage difference value ΔV and the two-time difference value ΔΔV is as described in FIG. 8 . The abnormality detection unit 66 determines that a predetermined deviation indicating a cell abnormality has occurred in the target cell when the two-time difference value ΔΔV is greater than a predetermined threshold.

[0158] Fig. 22 is a flowchart showing the procedure of the abnormality detection process for the battery cells 13 in this embodiment, and this process is executed by the battery ECU 20. In the abnormality detection process in Fig. 22, the process for provisional abnormality determination is the process shown in Fig. 5 described above, i.e., the process for provisionally determining whether or not an abnormality exists in each battery cell 13 based on the voltage difference value ΔV of the battery cell 13, and the process for final abnormality determination is the process shown in Fig. 9 described above, i.e., the process for final abnormality determination is the process shown in Fig. 9 based on the double difference value ΔΔV of the battery cell 13. The process in Fig. 22 will be described below while showing the correspondence between the abnormality detection process in Fig. 5 and the abnormality detection process in Fig. 9.

[0159] 22 , in steps S1101 and S1102, the cell voltage V(tm) of each battery cell 13 is acquired, and a voltage change VA(tm), which is the amount of change in the cell voltage V(tm) from an initial value (initial voltage value) for each battery cell 13, is calculated (VA(tm) = V(tm) - initial value). In steps S1103 and S1104, the absolute value of the voltage change VA(tm) is calculated, and the difference in the absolute values ​​of the voltage change VA(tm) between two adjacent battery cells 13 in the series path is calculated as a voltage difference value ΔVi+1,i(tm). Then, in step S1105, each battery cell 13 (cells C1 to Cn) is designated as a target cell, and the voltage difference values ​​ΔVi,i-1(tm) and ΔVi+1,i(tm) for each target cell are compared with a predetermined threshold value. The above steps S1101 to S1105 are the same processes as steps S101 to S105 in FIG.

[0160] If the result of step S1105 is negative for all battery cells 13 in the battery cell group currently being detected, the abnormality detection process is terminated to stop processing for the current battery cell group. If the result of step S1105 is positive for any battery cell 13 in the battery cell group currently being detected, the process proceeds to step S1106. In step S1106, it is provisionally determined that an abnormality has occurred in the battery cell 13 for which the condition of step S1105 is met.

[0161] Then, in step S1107, the difference between two voltage difference values ​​ΔV(tm) and ΔV(tm) that are adjacent in the series arrangement of the battery cells 13 is calculated as a double difference value ΔΔV(tm). In step S1108, it is determined whether the double difference value ΔΔV(tm) is equal to or less than a predetermined negative threshold value TH3. If a positive judgment is made in step S1108, the process proceeds to step S1109.

[0162] In step S1109, it is determined that an abnormality has occurred in the battery cell 13 for which the condition in step S1108 is satisfied. In other words, it is determined that a predetermined deviation has occurred in the voltage change amount VA(tm) of the target cell compared to the other battery cells 13. The determination result in step S1109 corresponds to the result of this determination. Thereafter, in step S1110, it is notified that an abnormality has occurred. The above steps S1107 to S1110 are the same processes as steps S305, S306, S308, and S309 in FIG. 9.

[0163] In the embodiment described above, a two-stage abnormality determination is performed when detecting an abnormality in each battery cell 13. For each battery cell group, a provisional determination of a cell abnormality is performed based on the voltage difference value ΔV (single difference value). Furthermore, for a battery cell group provisionally determined to have an abnormality among the multiple battery cell groups, a final determination is performed that a predetermined deviation has occurred in the battery cell 13 based on the second difference value ΔΔV. Comparing the abnormality determination (provisional determination) based on the voltage difference value ΔV and the abnormality determination (final determination) based on the second difference value ΔΔV, the calculation load and detection accuracy required for abnormality detection differ. As already described with reference to FIG. 8 , the abnormality determination based on the second difference value ΔΔV increases the calculation load, but allows for clear identification of abnormal cells, enabling highly accurate detection of cell abnormalities.

[0164] In this embodiment, in the first stage (provisional determination), a low-load abnormality determination is performed in consideration of the large number of battery cell groups that are subject to abnormality determination, and the accuracy of the abnormality determination can be improved in the second stage (main determination). In this case, abnormalities do not necessarily occur simultaneously in all battery cell groups (battery modules 11) in the battery pack B, and proper abnormality detection can be performed in order, starting with the battery cell group that includes the battery cell 13 in which an abnormality has occurred.

[0165] In this embodiment, the process for provisional abnormality determination and the process for final abnormality determination are a combination of processes that require different processing loads for parameter calculations, etc., and the former process may be a relatively low-load process, while the latter process may be a relatively high-load process. Specifically, when the process for provisional abnormality determination is the process shown in Fig. 5 described above, i.e., the process for provisionally determining whether or not an abnormality exists in each battery cell 13 based on the voltage difference value ΔV of the battery cell 13, the process for final abnormality determination may be any of the following: - the process shown in Fig. 6, i.e., the process for detecting an abnormality in each battery cell 13 based on an integrated difference value QA obtained by integrating the voltage difference value ΔV of the battery cell 13; - the process shown in Fig. 9, i.e., the process for detecting an abnormality in each battery cell 13 based on a double-time difference value ΔΔV of the battery cell 13; or - the process shown in Fig. 10, i.e., the process for detecting an abnormality in each battery cell 13 based on a double-time difference value QB obtained by integrating the double-time difference value ΔΔV of the battery cell 13.

[0166] Alternatively, when the process of provisional abnormality determination is the process of FIG. 5 described above, i.e., the process of provisionally determining whether each battery cell 13 has an abnormality based on the voltage difference value ΔV of the battery cell 13, the process of final abnormality determination may be: - the process of FIG. 11, i.e., the process of calculating the deviation degree Ri of the voltage change amount VA of the target cell based on the average value of the voltage change amount VA of the remaining battery cells 13 excluding one battery cell 13 (target cell) among the battery cells 13, and detecting an abnormality in the battery cell 13 based on the deviation degree Ri; - the process of FIG. 12, i.e., the process of calculating an integrated deviation value QCi by accumulating the deviation degree of the voltage change amount VA of the target cell each time the deviation degree is calculated, and detecting an abnormality in the battery cell 13 based on the integrated deviation degree value QCi; 13 , i.e., a process of integrating the deviation Di of the voltage change amount VA of each battery cell 13 to calculate an integrated deviation value QDi, and detecting an abnormality in the battery cell 13 based on the integrated deviation value QDi; 14 and 15 , i.e., a process of calculating the standard deviation σAi of the two-time difference value ΔΔV of each battery cell 13, calculating a deviation degree RAi from the standard deviation σAi, and detecting an abnormality in the battery cell 13 based on the deviation degree RAi; 16 , i.e., a process of integrating the deviation degree RAi to calculate an integrated deviation degree value QEi, and detecting an abnormality in the battery cell 13 based on the integrated deviation degree value QEi.

[0167] Eighth Embodiment In this embodiment, the abnormality detection unit for detecting an abnormality in each battery cell 13 includes a first determination unit that determines whether a predetermined deviation has occurred in the target cell based on a voltage difference value ΔV, which is a one-time difference value of the voltage change amount VA, and a second determination unit that determines whether a predetermined deviation has occurred in the target cell based on a two-time difference value ΔΔV, which is the difference between the voltage difference values ​​ΔΔV of two cells. The first determination unit and the second determination unit are selectively used based on a predetermined switching condition. In this embodiment, the abnormality determination of each battery cell 13 based on the voltage difference value ΔV of the battery cell 13 is referred to as a first determination process, and the abnormality determination of each battery cell 13 based on the two-time difference value ΔΔV of the battery cell 13 is referred to as a second determination process.

[0168] The abnormality determination of each battery cell 13 based on the voltage difference value ΔV of the battery cell 13 corresponds to a process of detecting an abnormality of each battery cell 13 by low-load calculation processing with a relatively small calculation load (first abnormality detection unit). The abnormality determination of each battery cell 13 based on the double difference value ΔΔV of the battery cell 13 corresponds to a process of detecting an abnormality of each battery cell 13 by high-load calculation processing with a relatively large calculation load (second abnormality detection unit). These abnormality detection processes are switched based on predetermined switching conditions (switching execution unit).

[0169] FIG. 23 is a flowchart showing the procedure for the abnormality detection process for the battery cell 13 in this embodiment. This process is executed by the battery ECU 20.

[0170] 23, in step S1200, it is determined whether to execute the first determination process or the second determination process based on a predetermined switching condition. The determination in step S1200 is preferably performed as follows.

[0171] The battery ECU 20 determines whether an abnormality determination has already been performed on each battery cell 13 in the battery module 11 currently being detected based on the voltage difference value ΔV, and whether that abnormality determination has determined that an abnormality exists. If an abnormality has not been determined based on the voltage difference value ΔV, the battery ECU 20 makes an affirmative decision in step S1200 and proceeds to step S1201. If an abnormality has been determined based on the voltage difference value ΔV, the battery ECU 20 makes a negative decision in step S1200 and proceeds to step S1202. In this case, the determination that an abnormality exists based on the voltage difference value ΔV corresponds to the switching condition for switching from the first determination process to the second determination process.

[0172] Alternatively, the battery ECU 20 may determine whether each battery cell 13 in the battery module 11 is degraded or is likely to degrade (degradation determination unit), and use the determination result as the switching condition. In this case, the determination that each battery cell 13 is degraded or is likely to degrade corresponds to the switching condition for switching from the first determination process to the second determination process.

[0173] Whether each battery cell 13 is degraded or highly likely to degrade may be determined based on, for example, the SOH (State of Health) of the battery cell 13. The SOH [%] of the battery cell 13 may be calculated as the ratio between the actual full charge capacity Cf [Ah] of the battery cell 13 and the reference full charge capacity Cf0 [Ah] of the battery cell 13 (SOH = Cf / Cf0). In this case, if the SOH is smaller than a predetermined value, an abnormality determination may be performed by a first determination process, and if the SOH is greater than the predetermined value, an abnormality determination may be performed by a second determination process.

[0174] It may be possible to determine whether or not each battery cell 13 is degraded or is highly likely to degrade based on the number of years since the vehicle was manufactured or the mileage of the vehicle. For example, if the vehicle has been in use for more than five years or the mileage exceeds 100,000 km, it is determined that each battery cell 13 is degraded or is highly likely to degrade.

[0175] Furthermore, when the battery cells 13 are in a predetermined low temperature state (for example, below 10°C), lithium precipitates on the electrodes, which accelerates the deterioration of the battery cells 13. Therefore, whether the battery cells 13 are in a low temperature state may be used to determine whether the battery cells 13 are in a state where deterioration is occurring or where there is a high possibility of deterioration occurring.

[0176] In step S1201, an abnormality determination is made for each battery cell 13 based on the voltage difference value ΔV of the battery cell 13. Note that the process of step S1201 is the same as steps S101 to S105 and S107 in Fig. 5, and therefore a description thereof will be omitted here.

[0177] In step S1202, an abnormality determination is performed for each battery cell 13 based on the two-time difference value ΔΔV of the battery cell 13. Note that the process in step S1202 is the same as steps S301 to S306 and S308 in Fig. 9, and therefore a description thereof will be omitted here.

[0178] In the embodiment described above, two types of abnormality determination are possible when detecting an abnormality in each battery cell 13, and the abnormality determination is switched depending on a predetermined switching condition. Here, when the battery cell 13 is used over a long period of time, there may be situations during that period when a cell abnormality is easy to detect and situations when it is difficult to detect. In such cases, by switching the abnormality determination process depending on the predetermined switching condition, it is possible to achieve appropriate abnormality detection while suppressing excessive computational load.

[0179] In addition, in this embodiment, switching is performed between a first determination process that determines whether a cell has an abnormality based on the voltage difference value ΔV (one-time difference value) and a second determination process that determines whether a cell has an abnormality based on the two-time difference value ΔΔV, based on the degree of deterioration of each battery cell 13. In this case, by performing abnormality detection according to the degree of deterioration of each battery cell 13, it is possible to achieve appropriate abnormality detection while suppressing excessive computational load.

[0180] In Fig. 23, the combination of the low-load calculation processing executed in step S1201 and the high-load calculation processing executed in step S1202 may be a combination other than the combination of the processing in Fig. 5 and the processing in Fig. 9. For example, a configuration may be adopted in which the low-load calculation processing is performed by any one of the processing in Fig. 5, Fig. 6, Fig. 9, or Fig. 10, and the high-load calculation processing is performed by any one of the processing in Fig. 11 to Fig. 16.

[0181] (Other Embodiments) The above embodiment may be modified as follows, for example.

[0182] As the abnormality detection process for the battery cell 13, the battery ECU 20 may execute the process shown in FIG.

[0183] 24, in step S1301, the cell voltage V(tm) of each battery cell 13 at time tm is acquired, and in step S1302, the voltage change amount VA(tm), which is the amount of change in cell voltage from the initial value, is calculated for each battery cell 13. Note that steps S1301 and S1302 are the same processes as steps S101 and S102 in FIG.

[0184] Then, in step S1303, the correlation coefficient CR(tm) between adjacent battery cells 13 in the series path is calculated. The correlation coefficient CR(tm) is an index that indicates the strength of the correlation (association) between two pieces of data, and specifically, it is preferable to calculate it using the following equation (5).

[0185] In equation (5), for two sets of data (x1, x2, ..., xN), (y1, y2, ..., yN), the sample covariance is sxy and the sample standard deviations are sx and sy, respectively, and the ratio of the sample covariance sxy to the product of the sample standard deviations sx and sy is the correlation coefficient CR.

[0186] In step S1303, the voltage change VA for the target cell (cell Ci) over the past N counts from the current time point is defined as data x1, x2, ..., xN, and the voltage change VA for the first adjacent cell (cell Ci-1) adjacent to the target cell on the negative side is defined as data y1, y2, ..., yN, to calculate the correlation coefficient CRi,i-1(tm). The voltage change VA for the target cell (cell Ci) over the past N counts from the current time point is defined as data x1, x2, ..., xN, and the voltage change VA for the second adjacent cell (cell Ci+1) adjacent to the target cell on the positive side is defined as data y1, y2, ..., yN, to calculate the correlation coefficient CRi+1,i(tm). If the target cell is an abnormal cell in the combination of the target cell and the adjacent cell, the correlation between these two cells will be weak, i.e., the correlation coefficient CR(tm) will be small. This makes it possible to determine whether the cell is abnormal.

[0187] Then, in step S1304, it is determined whether the correlation coefficients CR(tm) and CR(tm) are equal to or smaller than a predetermined threshold TH9. The threshold TH9 is a value greater than 0 and less than 1.

[0188] If none of the battery cells 13 meets the condition that both of the correlation coefficients CR(tm) and CR(tm) are equal to or less than the threshold value TH9, the result of step S1304 is negative, m is incremented by 1 in step S1305, and the process returns to step S1301. If any of the battery cells 13 meets the condition that both of the correlation coefficients CR(tm) and CR(tm) are equal to or less than the threshold value TH9, the result of step S1304 is positive, and the process proceeds to step S1306. In step S1306, it is determined that an abnormality has occurred in the battery cell 13 for which the condition of step S1304 is met. Then, in step S1307, a notification is issued that an abnormality has occurred.

[0189] If the battery cells 13 in the battery module 11 include an abnormal cell, a difference will occur between the correlation coefficient CR(tm) calculated using the voltage change amounts VA(tm) of two normal cells and the correlation coefficient CR(tm) calculated using the voltage change amounts VA(tm) of two cells including the abnormal cell. Therefore, an abnormality in the target cell can be properly detected.

[0190] In the above embodiment, the amount of change in cell voltage V(tm) from an initial value is calculated as the amount of voltage change VA(tm) of each battery cell 13. However, this may be modified. For example, the amount of change in cell voltage V(tm) over a predetermined time period, i.e., the time rate of change in voltage change VA(tm), may be calculated as the amount of voltage change VA(tm). In this case, the amount of change in cell voltage V(tm) per unit time, i.e., the slope of cell voltage V(tm) on the time axis, may be calculated as the amount of voltage change VA(tm).

[0191] In the above embodiment, the cell voltage V(tm) detected by the voltage sensor 31 is used as the state parameter of the battery cell 13. However, this may be changed. For example, a temperature sensor may be provided in each battery cell 13 of the battery module 11, and the cell temperature detected by each temperature sensor may be used as the state parameter. In this case, the amount of change in the cell temperature of each battery cell 13 over a predetermined period may be calculated as the temperature change amount (parameter change amount), and an abnormality in the target cell may be detected based on whether or not a predetermined deviation occurs in the temperature change amount of the target cell compared to the other battery cells 13. The specific abnormality detection method may be the same as the method in each of the above embodiments. It is also possible to provide each battery cell 13 of the battery module 11 with a strain sensor that detects strain occurring in the battery cell 13 or a pressure sensor that detects the internal pressure of the battery cell 13, and use the detection values ​​(state detection values) of these sensors as state parameters.

[0192] Furthermore, it is also possible to use, as the state parameters, state calculation values ​​that are calculated from state detection values ​​such as cell voltage and cell temperature and that indicate the state of the battery cell 13. Specifically, the impedance of each battery cell 13 is calculated based on the cell voltage and current flowing through each battery cell 13. Then, the amount of change in the impedance of each battery cell 13 over a predetermined period is calculated as the impedance change amount (parameter change amount), and an abnormality in the target cell is detected based on whether or not a predetermined deviation occurs in the impedance change amount of the target cell compared to the battery cells 13 other than the target cell. The specific abnormality detection method may be the same as the method in each of the above embodiments.

[0193] The configuration may also be such that the SOC (State of Charge) is calculated as a state parameter based on the cell voltage and current flowing through each battery cell 13, and an abnormality in the battery cell 13 is detected based on the amount of change in the SOC over a predetermined period. Alternatively, the impedance may be calculated based on the temperature detection value of a temperature sensor in each battery cell 13, and the impedance may be used as a state parameter. In the battery module 11, a current sensor that detects the current flowing through each battery cell 13 may be provided for each cell, and the cell temperature as a state parameter may be calculated based on the amount of current flowing through each battery cell 13.

[0194] In the third embodiment, the degree of deviation Ri(tm) of the voltage change VA(tm) in each battery cell 13 is calculated from the ratio of the absolute value of the difference between the voltage change VA(tm) and the average value μ(tm) to the standard deviation σ(tm). However, this may be changed. For example, the degree of deviation Ri(tm) may be the difference between the voltage change VA(tm) of the target cell and the average value μ(tm) of the voltage change VA(tm) in each battery cell 13, i.e., the deviation of the voltage change VA(tm).

[0195] In this case, the battery ECU 20 calculates the average value μ(tm) of the voltage change amounts VA(tm) of the remaining battery cells 13 excluding the target cell among the plurality of battery cells 13, and calculates the deviation between the average value μ(tm) and the voltage change amount VA(tm) of the target cell as the degree of deviation Ri(tm).

[0196] In the internal short-circuit process, which is the initial stage in the process of generating thermal runaway in the battery cell 13, the cell voltage gradually changes in the initial period of the internal short-circuit process as the internal short-circuit resistance of the battery cell 13 changes, and the cell temperature (internal temperature) gradually rises in the period following the initial period. Figure 25 shows changes in cell voltage and cell temperature in the initial period T1 and the subsequent period T2 in the internal short-circuit process. In consideration of these changes in cell voltage and cell temperature, an abnormality in the battery cell 13 may be detected based on the amount of change in cell voltage in the initial period T1, and may be detected based on the amount of change in cell temperature in the subsequent period T2.

[0197] 26 shows an example of the configuration of a battery system. A voltage sensor 31 is connected to each battery cell 13 of a battery module 11. A temperature sensor 34 is also provided in each battery cell 13, and the detection signal of each temperature sensor 34 is input to the monitoring device 12. The voltage sensor 31 corresponds to the "first sensor," and the temperature sensor 34 corresponds to the "second sensor."

[0198] The battery ECU 20 calculates a voltage change amount VA (first parameter change amount) which is the amount of change in cell voltage detected by the voltage sensor 31 over a predetermined period of time, and also calculates a temperature change amount TA (second parameter change amount) which is the amount of change in cell temperature detected by the temperature sensor 34 over a predetermined period of time. The battery ECU 20 is also capable of executing a first abnormality detection process that detects an abnormality in a target cell based on the voltage change amount VA of each battery cell 13, and a second abnormality detection process that detects an abnormality in a target cell based on the temperature change amount TA of each battery cell 13, and executes the second abnormality detection process on the condition that an abnormality in the target cell is detected by the first abnormality detection process.

[0199] FIG. 27 is a flowchart showing the procedure for the abnormality detection process for the battery cell 13 , and this process is executed by the battery ECU 20 .

[0200] 27 , in step S1401, the cell voltage of each battery cell 13 detected by the voltage sensor 31 and the cell temperature of each battery cell 13 detected by the temperature sensor 34 are acquired as detected state values. The cell voltage and cell temperature are acquired at a predetermined cycle. In step S1402, the amount of change in the cell voltage from the initial value of each battery cell 13 is calculated as a voltage change amount VA(tm), and the amount of change in the cell temperature from the initial value of each battery cell 13 is calculated as a temperature change amount TA(tm). The initial values ​​may be calculated at any predetermined timing.

[0201] In step S1403, it is determined whether the abnormality flag F is 0. The abnormality flag F is a flag that indicates whether any of the battery cells 13 has been determined to have an abnormality in the first abnormality detection process, and is set to F=0 if no abnormality is present, and F=1 if an abnormality is present.

[0202] If step S1403 is determined to be positive, the process proceeds to step S1404. In step S1404, a first abnormality detection process is executed. In the first abnormality detection process, abnormality detection of the target cell is performed based on the voltage change amount VA(tm) of each battery cell 13. The first abnormality detection process may be performed in accordance with any of the abnormality detection processes described in the above embodiments. For example, when using the method described in FIG. 5 , for all battery cells 13, the difference in absolute values ​​of the voltage change amounts VA(tm) between two adjacent battery cells 13 in a series path is calculated as a voltage difference value ΔVi+1,i(tm), and it is determined whether any battery cell 13 includes an abnormal cell based on the voltage difference value ΔVi+1,i(tm). If it is determined that any battery cell 13 includes an abnormal cell, a notification of the occurrence of an abnormality is issued.

[0203] In step S1405, it is determined whether or not an abnormal cell has been detected by the first abnormality detection process. If no abnormal cell has been detected, the process ends. In this case, the first abnormality detection process is repeatedly executed at a predetermined interval. If an abnormal cell has been detected, the process proceeds to step S1406, where the abnormality flag F is set to 1.

[0204] After the abnormality flag F is set to 1, step S1403 is negative, and the process proceeds to step S1407. In step S1407, a second abnormality detection process is executed. In the second abnormality detection process, abnormality detection of the target cell is performed based on the temperature change amount TA(tm) of each battery cell 13. The second abnormality detection process may be performed in accordance with any of the abnormality detection processes described in the above embodiments. For example, when using the method described in FIG. 5 , the voltage change amount VA(tm) may be replaced with the temperature change amount TA(tm). In this case, for all battery cells 13, the difference in absolute values ​​of the temperature change amounts TA(tm) between two adjacent battery cells 13 in the series path is calculated as a temperature difference value ΔTi+1,i(tm), and it is determined whether any battery cell 13 includes an abnormal cell based on the temperature difference value ΔTi+1,i(tm). If it is determined that any battery cell 13 includes an abnormal cell, a notification of the occurrence of an abnormality is issued.

[0205] With the above configuration, signs of thermal runaway in the battery cells 13 can be detected in a stepwise and appropriate manner while taking into account changes in the state of the battery cells 13. A strain sensor or a pressure sensor can be used instead of the temperature sensor 34. The strain sensor is provided in each battery cell 13 and detects, for example, the strain of the battery cell 13 case. In this case, the strain detection value detected by the strain sensor is used as the state detection value, and an abnormality in each battery cell 13 is detected based on the amount of change in the detected strain value. Alternatively, a pressure sensor is provided in each battery cell 13 and detects, for example, the pressure inside the battery cell 13 case. In this case, the pressure detection value detected by the pressure sensor is used as the state detection value, and an abnormality in each battery cell 13 is detected based on the amount of change in the detected pressure value.

[0206] 28 is a diagram showing the voltage-capacity characteristics, which are the relationship between the voltage (OCV) and the capacitance (SOC) of the battery cell 13. This voltage-capacity characteristic has a flat plateau region A1 and a steep region A2 where the change in voltage relative to the capacitance is steeper than in the plateau region A1. The steep region A2 is on the lower SOC side and higher SOC side than the plateau region A1, and for example, when the battery cell 13 is fully charged, the SOC of the battery cell 13 falls within the steep region A2 on the higher SOC side.

[0207] Comparing the case where the SOC is in the plateau region A1 with the case where the SOC is in the steep region A2, the amount of voltage change relative to the SOC change is larger in the steep region A2 than in the plateau region A1. Therefore, when an abnormal cell is included in the battery module 11, the difference in the voltage change amount VA between normal cells and abnormal cells is considered to be even larger when the SOC is in the steep region A2. For example, when each battery cell 13 of the battery module 11 (battery pack B) is fully charged, if the battery module 11 includes an abnormal cell, the difference in the voltage change amount VA between the abnormal cell and normal cells becomes significant, thereby improving the accuracy of abnormality detection. In light of this, it is recommended to perform abnormality detection based on the voltage change amount VA (parameter change amount) on the condition that the SOC of each battery cell 13 is in the steep region.

[0208] 29 is a flowchart showing the procedure for detecting an abnormality in the battery cells 13, and this process is executed by the battery ECU 20. In FIG. 29, in step S1501, it is determined whether the SOC of the battery cells 13 is in the steep region A2. At this time, if the SOC of all the battery cells 13 in the battery module 11 is in the steep region A2, for example, the result of step S1501 is YES.

[0209] If step S1501 is affirmative, the process proceeds to step S1502, where abnormality detection is performed on each battery cell 13. This abnormality detection may be performed using a process similar to any of the abnormality detection processes in the above-described embodiments. For example, when using the method described in FIG. 5 , the difference in absolute value of the voltage change amount VA(tm) between two adjacent battery cells 13 in a series path is calculated as a voltage difference value ΔVi+1,i(tm) for all battery cells 13, and whether or not any battery cell 13 includes an abnormal cell is determined based on the voltage difference value ΔVi+1,i(tm). If it is determined that any battery cell 13 includes an abnormal cell, a notification of the occurrence of an abnormality is issued.

[0210] Note that abnormality detection for each battery cell 13 may be performed when the SOC of the battery cell 13 is in the plateau region A1 and when the SOC of the battery cell 13 is in the steep region A2. In this case, taking into consideration that the amount of voltage change with respect to SOC change differs for each battery cell 13 depending on whether the SOC is in the plateau region A1 or the steep region A2, the thresholds (TH11, TH12, etc.) for detecting an abnormality in the voltage difference value ΔV may be changed depending on whether the SOC is in the plateau region A1 or the steep region A2. For example, when the SOC is in the steep region A2, the positive-side threshold TH11 may be made larger on the positive side and the negative-side threshold TH12 may be made larger on the negative side compared to when the SOC is in the plateau region A1.

[0211] In the above embodiments, the difference between the voltage change amount VA(tm) of the target cell and two different battery cells 13 is calculated as the voltage difference value ΔV(tm). However, this may be changed so that the difference between the voltage change amount VA(tm) of the target cell and three or four different battery cells 13 is calculated as the voltage difference value ΔV(tm). In this case, it is preferable to determine whether a predetermined deviation has occurred in the target cell based on the voltage difference values ​​ΔV(tm) of the target cell and other cells calculated using three or four combinations. In this case, increasing the number of combinations for calculating the voltage difference value ΔV(tm) can improve the reliability of abnormality detection.

[0212] In the above embodiment, the battery ECU 20 is used as the battery state detection device, but this configuration may be changed. For example, the monitoring device 12 of each battery unit 10 may be used as the battery state detection device, or a device external to the vehicle may be used as the battery state detection device.

[0213] The battery unit 10 in each of the above embodiments can be applied to stationary battery systems in addition to mobile bodies such as vehicles and aircraft.

[0214] The control device and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control device and method described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the control device and method described herein may be implemented by one or more special-purpose computers configured with a combination of a processor and memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

[0215] The technical concepts extracted from the above-described embodiments are described below. [Configuration 1] A battery state detection device (20) is applied to a battery system having a battery module (11) formed by connecting a plurality of battery cells (13) in series, the state of each battery cell being detected by a state detection unit, the battery state detection device (20) comprising: an acquisition unit that acquires state detection values ​​of each battery cell detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; and an abnormality detection unit that sets each of the plurality of battery cells as a target cell to be subjected to abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of parameter change of the target cell compared to battery cells other than the target cell. [Configuration 2] The battery state detection device according to Configuration 1, further comprising: a difference value calculation unit that calculates, for the target cell, differences in the parameter change amounts from two or more different battery cells as change amount difference values, and the abnormality detection unit determines whether the predetermined deviation has occurred in the target cell based on the change amount difference values ​​calculated by the difference value calculation unit, and detects an abnormality in the target cell based on the determination result. [Configuration 3] The battery state detection device according to Configuration 2, further comprising: a difference value calculation unit that calculates, as a first difference value, the change amount difference value between the target cell and a first non-target cell that is a battery cell different from the target cell in the battery module, and calculates, as a second difference value, the change amount difference value between the target cell and a second non-target cell that is a battery cell different from the target cell, and the abnormality detection unit determines that the predetermined deviation has occurred in the target cell when the absolute value of the first difference value and the absolute value of the second difference value are both greater than predetermined thresholds.[Configuration 4] The battery state detection device according to Configuration 2, wherein the difference value calculation unit calculates, at a predetermined period, the change amount difference value between the target cell and a first non-target cell that is the battery cell different from the target cell in the battery module as a first difference value, and calculates the change amount difference value between the target cell and a second non-target cell that is the battery cell different from the target cell as a second difference value, and calculates a first difference accumulated value and a second difference accumulated value by accumulating the absolute value of the first difference value and the absolute value of the second difference value each time each difference value is calculated, and the abnormality detection unit determines that the predetermined deviation has occurred in the target cell when both the first difference accumulated value and the second difference accumulated value are greater than predetermined thresholds. [Configuration 5] The battery state detection device according to Configuration 2, wherein the difference value calculation unit defines the battery cell adjacent to the negative electrode side of the target cell as a first adjacent cell and the battery cell adjacent to the positive electrode side of the target cell as a second adjacent cell, calculates the change amount difference values ​​between each of these adjacent cells and the target cell by subtraction in ascending or descending order of the cell serial connection, respectively, to obtain a first difference value and a second difference value, and calculates the difference between the first difference value and the second difference value as a second difference value, and the abnormality detection unit determines that the specified deviation has occurred in the target cell when the second difference value is greater than a predetermined threshold value. [Configuration 6] The battery state detection device according to Configuration 2, wherein the difference value calculation unit: defines the battery cell adjacent to the negative electrode side of the target cell as a first adjacent cell, and defines the battery cell adjacent to the positive electrode side of the target cell as a second adjacent cell; calculates the change amount difference values ​​between each of these adjacent cells and the target cell by subtraction in ascending or descending order of the cell serial order, respectively, to obtain a first difference value and a second difference value; calculates the difference between the first difference value and the second difference value as a double difference value; and further calculates a double difference integrated value by accumulating the double difference value each time the double difference value is calculated; and the abnormality detection unit determines that the predetermined deviation has occurred in the target cell when the double difference integrated value is greater than a predetermined threshold value.[Configuration 7] The battery system includes a plurality of battery cell groups each made up of three or more of the battery cells connected in series with each other, and the battery system includes a one-time difference value calculation unit that calculates, for each of the battery cell groups, differences in the parameter change amounts between the target cell and two or more different battery cells as one-time difference values; an abnormality provisional determination unit that, for each of the battery cell groups, makes a provisional determination of the presence or absence of an abnormality in the plurality of battery cells based on the one-time difference value calculated by the one-time difference value calculation unit; and a two-time difference value calculation unit that, in a battery cell group among the plurality of battery cell groups that has been provisionally determined to have an abnormality by the abnormality provisional determination unit, defines the battery cell adjacent to the negative electrode side of the target cell as a first adjacent cell and the battery cell adjacent to the positive electrode side of the target cell as a second adjacent cell, calculates the change amount difference values ​​between each of these adjacent cells and the target cell by subtraction in ascending or descending order of the cell serial order, respectively, to obtain first difference values ​​and second difference values, and calculates the difference between the first difference value and the second difference value as a two-time difference value. 3. The battery state detection device according to configuration 2, wherein the abnormality detection unit determines whether the predetermined deviation occurs in the target cell based on the two-time difference value calculated by the two-time difference value calculation unit.[Configuration 8] The device comprises: a one-time difference value calculation unit that calculates, for the target cell, differences in the parameter change amounts between the target cell and two or more different battery cells as one-time difference values; a two-time difference value calculation unit that calculates, by subtracting the battery cell adjacent to the negative electrode side of the target cell as a first adjacent cell and the battery cell adjacent to the positive electrode side of the target cell as a second adjacent cell, the change amount difference values ​​between each of these adjacent cells and the target cell in ascending or descending order of the cell serial order to obtain first and second difference values, and calculates the difference between the first and second difference values ​​as a two-time difference value; and the abnormality detection unit comprises: a first determination unit that determines whether or not the predetermined deviation has occurred in the target cell based on the one-time difference value calculated by the one-time difference value calculation unit; and a second determination unit that determines whether or not the predetermined deviation has occurred in the target cell based on the two-time difference value calculated by the two-time difference value calculation unit. and a switching execution unit that switches, based on a predetermined switching condition, whether to detect an abnormality in the target cell based on the determination result of the first determination unit or the determination result of the second determination unit. [Configuration 9] The battery state detection device according to Configuration 8, further comprising: a degradation determination unit that determines whether each battery cell in the battery module is degraded or is likely to degrade, and the switching execution unit uses the determination result of the degradation determination unit as the switching condition, and when it is determined that each battery cell is degraded or is likely to degrade, detects an abnormality in the target cell based on the determination result of the second determination unit.[Configuration 10] The battery state detection device according to Configuration 1, further comprising: a deviation degree calculation unit that calculates, as a deviation degree, a degree by which the parameter change amount of the target cell deviates from an average value of the parameter change amounts of each of the battery cells in the battery module; wherein the abnormality detection unit determines whether the specified deviation has occurred in the target cell based on the deviation degree calculated by the deviation degree calculation unit, and detects an abnormality in the target cell based on the determination result; and the deviation degree calculation unit calculates, as the deviation degree, a degree by which the parameter change amount of the target cell deviates from an average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells. [Configuration 11] The battery state detection device according to Configuration 1, further comprising a deviation calculation unit that calculates, at a predetermined cycle, a degree of deviation of the parameter change amount of the target cell from an average value of the parameter change amounts of each of the battery cells in the battery module, and calculates an integrated deviation value by accumulating the deviation degree each time the deviation degree is calculated, wherein the abnormality detection unit determines whether the predetermined deviation has occurred in the target cell based on the integrated deviation degree calculated by the deviation degree calculation unit, and detects an abnormality in the target cell based on the determination result, and the deviation degree calculation unit calculates, as the degree of deviation, a degree by which the parameter change amount of the target cell deviates from an average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells.[Configuration 12] The battery state detection device according to Configuration 1, comprising: a deviation calculation unit that calculates a deviation that is a difference between the parameter change amount of the target cell and an average value of the parameter change amounts of each of the battery cells; a standard deviation calculation unit that calculates a standard deviation by taking the root mean square of the difference between the parameter change amount of each of the battery cells and the average value thereof; and an integrated value calculation unit that calculates an integrated deviation value by integrating the absolute values ​​of the deviation calculated by the deviation calculation unit each time the deviation is calculated; wherein the abnormality detection unit determines whether the predetermined deviation has occurred in the target cell by comparing the integrated value of the deviation calculated by the integrated value calculation unit with a threshold value that is set based on the standard deviation calculated by the standard deviation calculation unit; the deviation calculation unit calculates the deviation using an average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells; and the standard deviation calculation unit calculates the standard deviation using the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells.[Configuration 13] When one designated cell is defined among the plurality of battery cells, and the battery cell adjacent to the designated cell on the negative electrode side is defined as a first adjacent cell, and the battery cell adjacent to the designated cell on the positive electrode side is defined as a second adjacent cell, the battery module includes a difference value calculation unit that calculates a change amount difference value that is a difference in the parameter change amount between the designated cell and the first adjacent cell and a change amount difference value that is a difference in the parameter change amount between the designated cell and the second adjacent cell by subtraction in ascending or descending order of the cell serial connection order, to obtain a first difference value and a second difference value, and calculates the difference between the first difference value and the second difference value as a double difference value; and a deviation degree calculation unit that sets the double difference value calculated using the target cell as the designated cell as a specific double difference value, and calculates a degree of deviation by which the specific double difference value deviates from an average value of the double difference values ​​calculated using each of the battery cells in the battery module one by one as the designated cell, The battery state detection device described in configuration 1, wherein the abnormality detection unit determines whether the specified deviation has occurred in the target cell based on the degree of deviation calculated by the deviation degree calculation unit, and detects an abnormality in the target cell based on the determination result, and the deviation degree calculation unit calculates, as the degree of deviation, the degree by which the specific two-time difference value deviates from an average value of the remaining two-time difference values, excluding the specific two-time difference value, among the two-time difference values ​​calculated for each of the battery cells one by one as the designated cell.[Configuration 14] When one designated cell is defined among the plurality of battery cells, and the battery cell adjacent to the negative electrode side of the designated cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the designated cell is defined as a second adjacent cell, the battery module includes a difference value calculation unit that calculates a change amount difference value that is a difference in the parameter change amount between the designated cell and the first adjacent cell and a change amount difference value that is a difference in the parameter change amount between the designated cell and the second adjacent cell by subtraction in ascending or descending order of the cell serial connection order, to obtain a first difference value and a second difference value, and calculates the difference between the first difference value and the second difference value as a double difference value; and a deviation degree calculation unit that sets the double difference value calculated using the target cell as the designated cell as a specific double difference value, and calculates a degree of deviation by which the specific double difference value deviates from an average value of the double difference values ​​calculated using each of the battery cells in the battery module as the designated cell, The battery state detection device described in configuration 1, wherein the abnormality detection unit determines whether the specified deviation has occurred in the target cell based on the degree of deviation calculated by the deviation degree calculation unit, and detects an abnormality in the target cell based on the determination result, and the deviation degree calculation unit calculates, as the degree of deviation, the degree by which the specific two-time difference value deviates from an average value of the remaining two-time difference values, excluding the specific two-time difference value and the two-time difference values ​​calculated using the first adjacent cell and the second adjacent cell as the designated cells, among the two-time difference values ​​calculated using each of the battery cells as the designated cell. [Configuration 15] The battery state detection device according to any one of configurations 1 to 14, further comprising an abnormality provisional determination unit that provisionally determines, as an abnormal cell, a battery cell in which a difference from an average value of the amount of parameter change is a predetermined value or more among the plurality of battery cells, and the abnormality detection unit determines, one by one, the abnormal cells provisionally determined by the abnormality provisional determination unit as target cells, and determines whether the predetermined deviation has occurred in the target cells.[Configuration 16] The battery state detection device according to Configuration 1, further comprising: a correlation coefficient calculation unit that calculates, for the target cell, a correlation coefficient that indicates the strength of the correlation between the parameter change amount and two or more different battery cells; and the abnormality detection unit determines whether the predetermined deviation has occurred in the target cell based on the correlation coefficient calculated by the correlation coefficient calculation unit, and detects an abnormality in the target cell based on the determination result. [Configuration 17] The battery state detection device according to Configuration 1, wherein the state detection unit includes a first sensor (31) that detects a cell voltage, which is a voltage between terminals of each of the battery cells, and a second sensor (34) that detects a temperature, a strain, or an internal pressure of each of the battery cells; the acquisition unit acquires, as the state detection values, the cell voltage of each of the battery cells detected by the first sensor and the temperature, the strain, or the internal pressure of each of the battery cells detected by the second sensor; the parameter change amount calculation unit calculates, as the parameter change amounts, a first parameter change amount based on the cell voltage of each of the battery cells detected by the first sensor, and a second parameter change amount based on the temperature or the strain of each of the battery cells detected by the second sensor; and the abnormality detection unit is capable of executing a first abnormality detection process that detects an abnormality in the target cell based on the first parameter change amount and a second abnormality detection process that detects an abnormality in the target cell based on the second parameter change amount, and executes the second abnormality detection process on the condition that an abnormality in the target cell is detected by the first abnormality detection process.[Configuration 18] A battery state detection device applied to a battery system having a battery module (11) formed by connecting a plurality of battery cells (13) in series, the state of each battery cell being detected by a state detection unit, the battery state detection device comprising: a first abnormality detection unit that performs abnormality detection for each battery cell by calculation processing with a relatively small calculation load based on the state detection value of each battery cell detected by the state detection unit; a second abnormality detection unit that performs abnormality detection for each battery cell by calculation processing with a relatively large calculation load based on the state detection value of each battery cell detected by the state detection unit; and a switching execution unit that switches between detecting abnormalities in each battery cell by the first abnormality detection unit and detecting abnormalities in each battery cell by the second abnormality detection unit based on a predetermined switching condition. [Configuration 19] The battery state detection device according to Configuration 18, wherein the switching condition is that the first abnormality detection unit has detected an abnormality in any of the battery cells in the battery module, and causes the second abnormality detection unit to detect an abnormality when the switching condition is met. [Configuration 20] The battery state detection device of Configuration 18, further comprising: a deterioration determination unit that determines whether each battery cell in the battery module is degraded or is likely to degrade, and the switching execution unit uses a determination result by the deterioration determination unit as the switching condition, and causes the second abnormality detection unit to detect an abnormality when it is determined that each battery cell is degraded or is likely to degrade. [Configuration 21] The battery state detection device of any of Configurations 1 to 20, further comprising: a voltage-capacity characteristic that indicates the relationship between voltage and capacitance of each battery cell, which has a plateau region and a steep region where the voltage change with respect to capacitance is steeper than in the plateau region, and the abnormality detection unit determines whether the predetermined deviation has occurred based on the amount of change in the parameter, on the condition that the capacitance of each battery cell is in the steep region.[Configuration 22] The battery state detection device according to any one of configurations 1 to 21, which is applied to a battery system including a voltage adjustment unit that adjusts the terminal voltages of the battery cells in the battery module to the same voltage, wherein the acquisition unit acquires the terminal voltages of the battery cells as the state detection values, and the abnormality detection unit determines whether the predetermined deviation has occurred based on the amount of change in the parameter, on condition that the voltage adjustment by the voltage adjustment unit has been performed.

[0216] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a difference value calculation unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and calculates, for each target cell, differences in the parameter change amounts between the target cell and two or more different battery cells as change amount difference values; an abnormality detection unit that determines whether a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the change amount difference value calculated by the difference value calculation unit, and detects an abnormality in the target cell based on the determination result; Equipped with The difference value calculation unit At a predetermined cycle, the change amount difference value between the target cell and a first non-target cell, which is a battery cell different from the target cell in the battery module, is calculated as a first difference value, and the change amount difference value between the target cell and a second non-target cell, which is a battery cell different from the target cell, is calculated as a second difference value; accumulating the absolute value of the first difference value and the absolute value of the second difference value each time each difference value is calculated to calculate a first difference accumulated value and a second difference accumulated value; The battery state detection device (20) is configured such that, when the first difference integrated value and the second difference integrated value are both greater than predetermined thresholds, the abnormality detection unit determines that the predetermined deviation has occurred in the target cell.

2. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a difference value calculation unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and calculates, for each target cell, differences in the parameter change amounts between the target cell and two or more different battery cells as change amount difference values; an abnormality detection unit that determines whether a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the change amount difference value calculated by the difference value calculation unit, and detects an abnormality in the target cell based on the determination result; Equipped with The difference value calculation unit The battery cell adjacent to the negative electrode side of the target cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the target cell is defined as a second adjacent cell, and the change amount difference values ​​between each of these adjacent cells and the target cell are calculated by subtraction in ascending order or descending order of the cell serial order, to obtain a first difference value and a second difference value, respectively; calculating a difference between the first difference value and the second difference value as a double difference value; The battery state detection device (20) is configured such that, when the two-time difference value is greater than a predetermined threshold, the abnormality detection unit determines that the predetermined deviation has occurred in the target cell.

3. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a difference value calculation unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and calculates, for each target cell, differences in the parameter change amounts between the target cell and two or more different battery cells as change amount difference values; an abnormality detection unit that determines whether a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the change amount difference value calculated by the difference value calculation unit, and detects an abnormality in the target cell based on the determination result; Equipped with The difference value calculation unit The battery cell adjacent to the negative electrode side of the target cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the target cell is defined as a second adjacent cell, and the change amount difference values ​​between each of these adjacent cells and the target cell are calculated by subtraction in ascending order or descending order of the cell serial order, to obtain a first difference value and a second difference value, respectively; calculating a difference between the first difference value and the second difference value as a double difference value; Furthermore, the two-time difference value is accumulated each time the two-time difference value is calculated to calculate a two-time difference accumulated value; The battery state detection device (20) is configured such that, when the two-times differential integrated value is greater than a predetermined threshold, the abnormality detection unit determines that the predetermined deviation has occurred in the target cell.

4. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, In the battery system, a plurality of battery cell groups are configured by three or more of the battery cells connected in series with each other, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a single-time difference value calculation unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and calculates, for each of the battery cell groups, differences in the parameter change amounts of the target cell and two or more different battery cells as single-time difference values; a temporary abnormality determination unit that temporarily determines whether or not an abnormality exists in the plurality of battery cells for each battery cell group based on the one-time difference value calculated by the one-time difference value calculation unit; a two-time difference value calculation unit that calculates, in a battery cell group that has been provisionally determined to have an abnormality by the provisional abnormality determination unit, a first adjacent cell as the battery cell adjacent on the negative electrode side of the target cell and a second adjacent cell as the battery cell adjacent on the positive electrode side of the target cell, calculates a first difference value and a second difference value by subtracting the first adjacent cell from the second adjacent cell in ascending or descending order of the cell serial order, the first difference value and the second difference value being the difference in the parameter change between each of the first adjacent cell and the target cell, and calculates a two-time difference value as the difference between the first difference value and the second difference value; an abnormality detection unit that determines whether a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the two-time difference value calculated by the two-time difference value calculation unit, and detects an abnormality of the target cell based on the determination result; A battery state detection device (20) comprising:

5. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a single-time difference value calculation unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and calculates, for each target cell, differences in the parameter change amounts between the target cell and two or more different battery cells as single-time difference values; a double difference value calculation unit that calculates a first difference value and a second difference value by subtracting the battery cell adjacent to the target cell on the negative electrode side as a first adjacent cell and the battery cell adjacent to the target cell on the positive electrode side in ascending or descending order of the cell serial order, the first difference value and the second difference value being the difference in the parameter change amount between each of the adjacent cells and the target cell, and calculating a double difference value between the first difference value and the second difference value; an anomaly detection unit that determines whether a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the calculation results of the one-time difference value calculation unit and the two-time difference value calculation unit, and detects an anomaly of the target cell based on the determination result; Equipped with The abnormality detection unit a first determination unit that determines whether or not the predetermined deviation occurs in the target cell based on the one-time difference value calculated by the one-time difference value calculation unit; a second determination unit that determines whether or not the predetermined deviation occurs in the target cell based on the second difference value calculated by the second difference value calculation unit; a switching execution unit that switches between detecting an abnormality in the target cell based on the judgment result of the first judgment unit and detecting an abnormality in the target cell based on the judgment result of the second judgment unit based on a predetermined switching condition; A battery state detection device (20) having:

6. a deterioration determination unit that determines whether deterioration of each battery cell in the battery module is occurring or whether there is a high possibility that deterioration will occur; 6. The battery state detection device according to claim 5, wherein the switching execution unit uses the determination result by the deterioration determination unit as the switching condition, and when it is determined that deterioration is occurring in each of the battery cells or that deterioration is likely to occur, detects an abnormality in the target cell based on the determination result of the second determination unit.

7. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a deviation degree calculation unit that calculates, at a predetermined cycle, a deviation degree of the parameter change amount of the target cell from an average value of the parameter change amounts of the respective battery cells in the battery module, and that calculates an integrated deviation degree value by accumulating the deviation degree each time the deviation degree is calculated; Equipped with the anomaly detection unit determines whether or not the predetermined deviation occurs in the target cell based on the deviation degree integrated value calculated by the deviation degree calculation unit, and detects an anomaly in the target cell based on the determination result; The deviation degree calculation unit calculates, as the deviation degree, the degree to which the parameter change amount of the target cell deviates from the average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells.

8. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a deviation calculation unit that calculates a deviation that is a difference between the parameter change amount of the target cell and an average value of the parameter change amounts of the respective battery cells; a standard deviation calculation unit that calculates a standard deviation by the root mean square of the difference between the parameter change amount of each battery cell and its average value; an integrated value calculation unit that calculates an integrated deviation value by integrating the absolute values ​​of the deviations calculated by the deviation calculation unit each time the deviations are calculated; Equipped with the anomaly detection unit determines whether or not the predetermined deviation occurs in the target cell by comparing the deviation integrated value calculated by the integrated value calculation unit with a threshold value set based on the standard deviation calculated by the standard deviation calculation unit; the deviation calculation unit calculates the deviation using an average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells; The battery state detection device (20) is configured such that the standard deviation calculation unit calculates the standard deviation using the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells.

9. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a difference value calculation unit that calculates a first difference value and a second difference value by subtracting a change amount difference value that is a difference in the parameter change amount between the designated cell and the first adjacent cell and a change amount difference value that is a difference in the parameter change amount between the designated cell and the second adjacent cell, respectively, in ascending or descending order of the cell serial connection order, and calculates the difference between the first difference value and the second difference value twice as a difference value; a deviation degree calculation unit that sets the two-time difference value calculated using the target cell as the designated cell as a specific two-time difference value, and calculates a deviation degree by calculating a degree by which the specific two-time difference value deviates from an average value of the two-time difference values ​​calculated using each of the battery cells in the battery module as the designated cell; Equipped with the anomaly detection unit determines whether or not the predetermined deviation occurs in the target cell based on the deviation degree calculated by the deviation degree calculation unit, and detects an anomaly in the target cell based on the determination result; The deviation degree calculation unit calculates, as the deviation degree, the degree by which the specific two-time difference value deviates from the average value of the remaining two-time difference values, excluding the specific two-time difference value, among the two-time difference values ​​calculated for each of the battery cells one by one as the designated cell.

10. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a difference value calculation unit that calculates a first difference value and a second difference value by subtracting a change amount difference value that is a difference in the parameter change amount between the designated cell and the first adjacent cell and a change amount difference value that is a difference in the parameter change amount between the designated cell and the second adjacent cell, respectively, in ascending or descending order of the cell serial connection order, and calculates the difference between the first difference value and the second difference value twice as a difference value; a deviation degree calculation unit that sets the two-time difference value calculated using the target cell as the designated cell as a specific two-time difference value, and calculates a deviation degree by calculating a degree by which the specific two-time difference value deviates from an average value of the two-time difference values ​​calculated using each of the battery cells in the battery module as the designated cell; Equipped with the anomaly detection unit determines whether or not the predetermined deviation occurs in the target cell based on the deviation degree calculated by the deviation degree calculation unit, and detects an anomaly in the target cell based on the determination result; The deviation degree calculation unit calculates, as the deviation degree, the degree by which the specific two-time difference value deviates from the average value of the remaining two-time difference values, excluding the specific two-time difference value and the two-time difference values ​​calculated using the first adjacent cell and the second adjacent cell as the designated cells, out of the two-time difference values ​​calculated using each of the battery cells as the designated cell.

11. a temporary abnormality determination unit that temporarily determines, as an abnormal cell, a battery cell in which a difference between the parameter change amount and an average value of the battery cells is equal to or greater than a predetermined value; The battery state detection device according to any one of claims 1 to 10, wherein the abnormality detection unit determines whether the predetermined deviation occurs in each of the target cells, one by one, for each of the abnormal cells provisionally determined by the abnormality provisional determination unit.

12. Each of the battery cells has a voltage-capacity characteristic that indicates the relationship between voltage and capacitance, which has a plateau region and a steep region where the change in voltage relative to capacitance is steeper than that in the plateau region; The battery state detection device according to any one of claims 1 to 10, wherein the abnormality detection unit determines whether the predetermined deviation occurs based on the amount of change in the parameter, on the condition that the electrical capacitance of each of the battery cells is in the steep region.

13. The present invention is applied to a battery system including a voltage adjusting unit that adjusts the terminal voltages of the battery cells in the battery module to the same voltage, the acquisition unit acquires a terminal voltage of each of the battery cells as the state detection value; The battery state detection device according to any one of claims 1 to 10, wherein the abnormality detection unit determines whether the specified deviation occurs based on the parameter change amount, provided that voltage adjustment is being performed by the voltage adjustment unit.

14. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a provisional abnormality determination unit that provisionally determines, as an abnormal cell, a battery cell in which a difference between the parameter change amount and an average value of the battery cells is equal to or greater than a predetermined value; Equipped with The abnormality detection unit determines whether the predetermined deviation occurs in each of the target cells, one by one, of the abnormal cells provisionally determined by the abnormality provisional determination unit.

15. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; Equipped with the state detection unit includes a first sensor (31) that detects a cell voltage, which is a voltage between the terminals of each battery cell, and a second sensor (34) that detects a temperature, a strain, or an internal pressure of each battery cell; the acquisition unit acquires, as the state detection value, a cell voltage of each of the battery cells detected by the first sensor and a temperature, a strain, or an internal pressure of each of the battery cells detected by the second sensor; the parameter change amount calculation unit calculates, as the parameter change amount, a first parameter change amount based on a cell voltage of each of the battery cells detected by the first sensor, and calculates a second parameter change amount based on a temperature or a strain of each of the battery cells detected by the second sensor; The abnormality detection unit is capable of executing a first abnormality detection process that detects an abnormality in the target cell based on the first parameter change amount, and a second abnormality detection process that detects an abnormality in the target cell based on the second parameter change amount, and executes the second abnormality detection process on the condition that an abnormality in the target cell is detected by the first abnormality detection process.

16. The present invention is applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, and in which the state of each battery cell is detected by a state detection unit, an acquisition unit that acquires the state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation unit that sets either the state detection value acquired by the acquisition unit or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection unit that sets each of the plurality of battery cells as a target cell that is a target for abnormality detection, and detects an abnormality in the target cell based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; Equipped with the battery system includes a voltage adjusting unit that adjusts the terminal voltages of the battery cells in the battery module to the same voltage; the acquisition unit acquires a terminal voltage of each of the battery cells as the state detection value; The battery state detection device, wherein the abnormality detection unit determines whether the predetermined deviation has occurred based on the amount of change in the parameter, on condition that voltage adjustment is being performed by the voltage adjustment unit.

17. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a difference value calculation process in which each of the plurality of battery cells is designated as a target cell to be subjected to abnormality detection, and a difference in the parameter change amount between the target cell and two or more different battery cells is calculated as a change amount difference value; an abnormality detection process that determines whether or not a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the change amount difference value calculated by the difference value calculation process, and detects an abnormality in the target cell based on the determination result; Execute In the difference value calculation process, At a predetermined cycle, the change amount difference value between the target cell and a first non-target cell, which is a battery cell different from the target cell in the battery module, is calculated as a first difference value, and the change amount difference value between the target cell and a second non-target cell, which is a battery cell different from the target cell, is calculated as a second difference value; accumulating the absolute value of the first difference value and the absolute value of the second difference value each time each difference value is calculated to calculate a first difference accumulated value and a second difference accumulated value; a program that determines, in the abnormality detection process, that the predetermined deviation occurs in the target cell when the first difference integrated value and the second difference integrated value are both greater than predetermined thresholds.

18. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a difference value calculation process in which each of the plurality of battery cells is designated as a target cell to be subjected to abnormality detection, and a difference in the parameter change amount between the target cell and two or more different battery cells is calculated as a change amount difference value; an abnormality detection process that determines whether or not a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the change amount difference value calculated by the difference value calculation process, and detects an abnormality in the target cell based on the determination result; Execute In the difference value calculation process, The battery cell adjacent to the negative electrode side of the target cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the target cell is defined as a second adjacent cell, and the change amount difference values ​​between each of these adjacent cells and the target cell are calculated by subtraction in ascending order or descending order of the cell serial order, to obtain a first difference value and a second difference value, respectively; calculating a difference between the first difference value and the second difference value as a double difference value; a program that determines that the predetermined deviation has occurred in the target cell when the two-time difference value is greater than a predetermined threshold value in the abnormality detection process.

19. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a difference value calculation process in which each of the plurality of battery cells is designated as a target cell to be subjected to abnormality detection, and a difference in the parameter change amount between the target cell and two or more different battery cells is calculated as a change amount difference value; an abnormality detection process that determines whether or not a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the change amount difference value calculated by the difference value calculation process, and detects an abnormality in the target cell based on the determination result; Execute In the difference value calculation process, The battery cell adjacent to the negative electrode side of the target cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the target cell is defined as a second adjacent cell, and the change amount difference values ​​between each of these adjacent cells and the target cell are calculated by subtraction in ascending order or descending order of the cell serial order, to obtain a first difference value and a second difference value, respectively; calculating a difference between the first difference value and the second difference value as a double difference value; Furthermore, the two-time difference value is accumulated each time the two-time difference value is calculated to calculate a two-time difference accumulated value; a program that determines that the predetermined deviation has occurred in the target cell when the two-times difference integrated value is greater than a predetermined threshold value in the abnormality detection process.

20. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), In the battery system, a plurality of battery cell groups are configured by three or more of the battery cells connected in series with each other, an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a single-time difference value calculation process for determining each of the plurality of battery cells as a target cell that is a target cell for anomaly detection, and calculating, for each of the battery cell groups, differences in the parameter change amounts of the target cell and two or more different battery cells as single-time difference values; a temporary abnormality determination process for performing a temporary determination of the presence or absence of an abnormality in the plurality of battery cells based on the one-time difference value calculated by the one-time difference value calculation process for each of the battery cell groups; a double difference value calculation process in which, in a battery cell group among the plurality of battery cell groups that has been provisionally determined to have an abnormality by the abnormality provisional determination process, the battery cell adjacent to the negative electrode side of the target cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the target cell is defined as a second adjacent cell, and a change amount difference value, which is a difference in the parameter change amount between each of these adjacent cells and the target cell, is calculated by subtraction in ascending order or descending order of the cell serial order, to obtain a first difference value and a second difference value, and the difference between the first difference value and the second difference value is calculated as a double difference value; an abnormality detection process that determines whether a predetermined deviation occurs in the parameter change amount of the target cell with respect to battery cells other than the target cell based on the second difference value calculated by the second difference value calculation process, and detects an abnormality in the target cell based on the determination result; A program that executes.

21. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; a single-time difference value calculation process for determining each of the plurality of battery cells as a target cell that is a target cell for abnormality detection, and calculating, for each target cell, differences in the parameter change amounts between the target cell and two or more different battery cells as single-time difference values; a double difference value calculation process in which the battery cell adjacent to the negative electrode side of the target cell is defined as a first adjacent cell, and the battery cell adjacent to the positive electrode side of the target cell is defined as a second adjacent cell, and a change amount difference value, which is a difference in the parameter change amount between each of these adjacent cells and the target cell, is calculated by subtraction in ascending or descending order of the cell serial order to obtain a first difference value and a second difference value, and the difference between the first difference value and the second difference value is calculated as a double difference value; an abnormality detection process that determines whether a predetermined deviation occurs in the parameter change amount of the target cell relative to battery cells other than the target cell based on the calculation results of the one-time difference value calculation process and the two-time difference value calculation process, and detects an abnormality in the target cell based on the determination result; Execute The abnormality detection process includes: a first determination process for determining whether or not the predetermined deviation occurs in the target cell based on the one-time difference value calculated by the one-time difference value calculation process; a second determination process for determining whether or not the predetermined deviation occurs in the target cell based on the second difference value calculated by the second difference value calculation process; A switching execution process that switches between detecting an abnormality in the target cell based on the judgment result of the first judgment process and detecting an abnormality in the target cell based on the judgment result of the second judgment process based on a predetermined switching condition; Including, the program.

22. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a deviation degree calculation process that calculates, at a predetermined cycle, a deviation degree of the parameter change amount of the target cell from an average value of the parameter change amounts of the respective battery cells in the battery module, and calculates an integrated deviation degree value by accumulating the deviation degree each time the deviation degree is calculated; Execute the abnormality detection process determines whether or not the predetermined deviation occurs in the target cell based on the deviation degree integrated value calculated by the deviation degree calculation process, and detects an abnormality in the target cell based on the determination result; a program for calculating, in the deviation degree calculation process, a degree of deviation of the parameter change amount of the target cell from an average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells, as the deviation degree.

23. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a deviation calculation process for calculating a deviation that is a difference between the parameter change amount of the target cell and an average value of the parameter change amounts of the respective battery cells; a standard deviation calculation process for calculating a standard deviation by the root mean square of the difference between the parameter change amount of each battery cell and its average value; an integrated value calculation process for calculating an integrated deviation value by integrating the absolute values ​​of the deviations calculated by the deviation calculation process each time the deviations are calculated; Execute the abnormality detection process determines whether or not the predetermined deviation occurs in the target cell by comparing the deviation integrated value calculated by the integrated value calculation process with a threshold value set based on the standard deviation calculated by the standard deviation calculation process; In the deviation calculation process, the deviation is calculated using an average value of the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells; a program for calculating the standard deviation using the parameter change amounts of the remaining battery cells excluding the target cell among the plurality of battery cells in the standard deviation calculation process.

24. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a difference value calculation process in which, when one designated cell is determined from the plurality of battery cells, the battery cell adjacent to the designated cell on the negative electrode side is designated as a first adjacent cell, and the battery cell adjacent to the designated cell on the positive electrode side is designated as a second adjacent cell, a change amount difference value that is a difference in the parameter change amount between the designated cell and the first adjacent cell and a change amount difference value that is a difference in the parameter change amount between the designated cell and the second adjacent cell are calculated by subtraction in ascending or descending order of the cell serial connection order, to obtain a first difference value and a second difference value, and the difference between the first difference value and the second difference value is calculated twice as a difference value; a deviation degree calculation process for setting the two-time difference value calculated using the target cell as the designated cell as a specific two-time difference value, and calculating a deviation degree by which the specific two-time difference value deviates from an average value of the two-time difference values ​​calculated using each of the battery cells in the battery module as the designated cell; Execute the abnormality detection process determines whether or not the predetermined deviation occurs in the target cell based on the deviation degree calculated by the deviation degree calculation process, and detects an abnormality in the target cell based on the determination result; In the deviation degree calculation process, the program calculates, as the deviation degree, the degree by which the specific two-time difference value deviates from the average value of the remaining two-time difference values, excluding the specific two-time difference value, among the two-time difference values ​​calculated for each of the battery cells one by one as the designated cell.

25. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a difference value calculation process in which, when one designated cell is determined from the plurality of battery cells, the battery cell adjacent to the designated cell on the negative electrode side is designated as a first adjacent cell, and the battery cell adjacent to the designated cell on the positive electrode side is designated as a second adjacent cell, a change amount difference value that is a difference in the parameter change amount between the designated cell and the first adjacent cell and a change amount difference value that is a difference in the parameter change amount between the designated cell and the second adjacent cell are calculated by subtraction in ascending or descending order of the cell serial connection order, to obtain a first difference value and a second difference value, and the difference between the first difference value and the second difference value is calculated twice as a difference value; a deviation degree calculation process for setting the two-time difference value calculated using the target cell as the designated cell as a specific two-time difference value, and calculating a deviation degree by which the specific two-time difference value deviates from an average value of the two-time difference values ​​calculated using each of the battery cells in the battery module as the designated cell; Execute the abnormality detection process determines whether or not the predetermined deviation occurs in the target cell based on the deviation degree calculated by the deviation degree calculation process, and detects an abnormality in the target cell based on the determination result; a program for calculating, in the deviation degree calculation process, a degree by which the specific two-time difference value deviates from an average value of the remaining two-time difference values, excluding the specific two-time difference value and the two-time difference values ​​calculated using the first adjacent cell and the second adjacent cell as the designated cells, among the two-time difference values ​​calculated using each of the battery cells as the designated cell, as the deviation degree.

26. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; a provisional abnormality determination process for provisionally determining, as an abnormal cell, a battery cell in which a difference between the parameter change amount and an average value of the battery cells is equal to or greater than a predetermined value; Execute a program for determining whether the predetermined deviation occurs in each of the target cells, the target cells being each provisionally determined to be abnormal by the provisional abnormality determination process, in the abnormality detection process;

27. ​​A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; Execute the state detection unit includes a first sensor (31) that detects a cell voltage, which is a voltage between the terminals of each battery cell, and a second sensor (34) that detects a temperature, a strain, or an internal pressure of each battery cell; In the acquisition process, the cell voltage of each of the battery cells detected by the first sensor and the temperature, strain, or internal pressure of each of the battery cells detected by the second sensor are acquired as the state detection values; In the parameter change amount calculation process, a first parameter change amount is calculated based on a cell voltage of each of the battery cells detected by the first sensor, and a second parameter change amount is calculated based on a temperature or a strain of each of the battery cells detected by the second sensor, as the parameter change amount; A program capable of executing, in the abnormality detection processing, a first abnormality detection processing that detects an abnormality in the target cell based on the first parameter change amount, and a second abnormality detection processing that detects an abnormality in the target cell based on the second parameter change amount, and which executes the second abnormality detection processing on the condition that an abnormality in the target cell is detected by the first abnormality detection processing.

28. A program applied to a battery system having a battery module (11) in which a plurality of battery cells (13) are connected in series, in which the state of each battery cell is detected by a state detection unit, and executed by a computer (20), an acquisition process of acquiring a state detection value of each of the battery cells detected by the state detection unit; a parameter change amount calculation process that sets either the state detection value acquired by the acquisition process or a state calculation value calculated from the state detection value and indicating the state of the battery cell as a state parameter of the battery cell, and calculates an amount of change in the state parameter over a predetermined period as a parameter change amount; an abnormality detection process in which each of the plurality of battery cells is designated as a target cell that is a target for abnormality detection, and an abnormality in the target cell is detected based on whether a predetermined deviation occurs in the amount of change in the parameter of the target cell compared to battery cells other than the target cell; Execute the battery system includes a voltage adjusting unit that adjusts the terminal voltages of the battery cells in the battery module to the same voltage; In the acquisition process, a terminal voltage of each battery cell is acquired as the state detection value; a program for determining whether the predetermined deviation has occurred based on the amount of change in the parameter, on condition that the voltage adjustment is being performed by the voltage adjustment unit, in the abnormality detection process;