Rechargeable battery system, abnormality determination method, and program

Abstract

To easily determine presence or absence of abnormality pertaining to measurement of a rechargeable cell.SOLUTION: A rechargeable battery system 1 includes: a voltage sensor 23 for measuring a voltage of a rechargeable battery cell 21; a current sensor 22 for measuring a current flowing to the rechargeable battery cell 21; a monitoring section 4 for monitoring the state of the rechargeable battery cell 21 on the basis of a measurement value of a voltage and a measurement value of a current; and a control section 3 for controlling charge / discharge of the rechargeable battery cell 21 on the basis of the monitoring result of the monitoring section 4 and determining presence or absence of abnormality regarding the measurement of the rechargeable battery cell 21. The control section 3 generates a charge characteristic (discharge characteristic) 53 of the rechargeable cell 21 on the basis of the measurement value of the capacity of the rechargeable battery cell 21 and a measurement value of a voltage, calculates a deviation amount Dv between an actual inflection point voltage Vix and a unique inflection point voltage Vi0 in the charge characteristic (discharge characteristic) 53, and determines the presence or absence of abnormality regarding the measurement of the rechargeable battery cell 21 on the basis of the deviation amount Dv.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery system, an abnormality determination method, and a program.

Background Art

[0002] In recent years, secondary batteries that perform charge and discharge by the movement of alkali ions such as lithium ions and sodium ions have been adopted in a wide range of products such as mobile devices such as smartphones and tablet terminals, electric vehicles, and stationary battery systems.

[0003] In recent years, a battery system including a battery module having a battery string in which a plurality of single battery cells (single cells) are connected in series has been becoming popular. The battery system is installed, for example, on the premises of a consumer who receives power supply from the power grid, charges the battery module by power supply from the power grid or a solar power generation device, etc., and discharges the battery module to supply power to a load or the power grid on the premises of the consumer.

[0004] Generally, a battery system measures the voltage of each battery cell constituting the battery string and the current flowing through the battery string, and controls the charge and discharge of each battery cell based on the measurement results (see, for example, Patent Document 1).

[0005] As a voltage sensor for measuring the voltage of each battery cell in a battery system, there is known one including a multiplexer that alternately selects and outputs the voltages at both ends of each battery cell, and an analog / digital conversion circuit (hereinafter also referred to as "ADC") that converts the voltage output from the multiplexer into a digital value and outputs it.

[0006] However, for example, when a multiplexer or ADC as a voltage sensor fails, or when components such as protection diodes and resistors existing in the path from the battery cell to the multiplexer fail, an event where an offset is superimposed on the measured voltage value (also referred to as "voltage offset"), or an event where the measured voltage value is fixed to a certain value (hereinafter also referred to as "voltage sticking") may occur. When such an event occurs, the battery system controls the charging and discharging of the battery module using the incorrect measured voltage value, thus deviating from the safe operating range of the battery module and causing problems such as promoting overcharging of the battery cell and deterioration of the battery cell.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Conventionally, the determination of the presence or absence of abnormalities such as voltage offset and voltage sticking in a battery system has been performed by an operator regularly visiting the location where the battery system is installed and measuring the voltage of the battery cell using a separately prepared reference power supply device or the like. Therefore, there has been a problem of high labor costs.

[0009] The present invention has been made in view of the above-described problems, and an object thereof is to enable easy determination of the presence or absence of abnormalities related to the measurement of battery cells.

Means for Solving the Problems

[0010] A battery system according to a representative embodiment of the present invention includes a battery string including at least one battery cell, a voltage measurement unit that measures the voltage of the battery cell, a current measurement unit that measures the current flowing through the battery cell, a monitoring unit that monitors the state of the battery cell based on the measured value of the voltage measured by the voltage measurement unit and the measured value of the current measured by the current measurement unit, and a control unit that controls the charge and discharge of the battery string and determines the presence or absence of an abnormality related to the measurement of the battery string based on the monitoring result by the monitoring unit. The control unit includes a charge and discharge control unit that controls the charge and discharge of the battery string based on the monitoring result by the monitoring unit, a storage unit that stores a specific inflection point voltage that is the voltage of a specific inflection point in at least one of the charging characteristics and the discharging characteristics of the battery cell, a measured value acquisition unit that acquires the measured value of the capacity of the battery cell and the measured value of the voltage during charging or discharging of the battery cell based on the monitoring result by the monitoring unit, a charge and discharge characteristic generation unit that generates at least one of the charging characteristics and the discharging characteristics based on the measured value of the capacity and the measured value of the voltage, an inflection point voltage calculation unit that calculates an actual inflection point voltage that is the voltage of an inflection point in at least one of the charging characteristics and the discharging characteristics generated by the charge and discharge characteristic generation unit, a deviation amount calculation unit that calculates the deviation amount between the specific inflection point voltage and the actual inflection point voltage, and a determination unit that determines the presence or absence of an abnormality related to the measurement of the battery cell based on the deviation amount.

Advantages of the Invention

[0011] According to the battery system of the present invention, it is possible to easily determine the presence or absence of an abnormality related to the measurement of the battery cell.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] 1. Outline of the Embodiment First, an overview of typical embodiments of the invention disclosed in the present application will be described. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are described with parentheses.

[0014] 〔1〕A battery system (1) according to a typical embodiment of the present invention includes a battery string (20) including at least one battery cell (21), a voltage sensor (23) for measuring the voltage of the battery cell, a current sensor (22) for measuring the current flowing through the battery cell, a monitoring unit (4) for monitoring the state of the battery cell based on the measured value of the voltage measured by the voltage sensor and the measured value of the current measured by the current sensor, and a control unit (3, 3A to 3D) for controlling the charge and discharge of the battery string and determining the presence or absence of an abnormality related to the measurement of the battery string based on the monitoring result by the monitoring unit. The control unit includes a charge and discharge control unit (31) for controlling the charge and discharge of the battery string based on the monitoring result by the monitoring unit, a storage unit (37, 37A to 37D) for storing a specific inflection point voltage (Vi0) which is the voltage of a specific inflection point in at least one of the charge characteristics and the discharge characteristics of the battery cell, a measured value acquisition unit (32) for acquiring the measured value of the capacity of the battery cell and the measured value of the voltage during charging or discharging of the battery cell based on the monitoring result by the monitoring unit, a charge and discharge characteristic generation unit (33, 33A to 33C) for generating at least one of the charge characteristics and the discharge characteristics (53, 53A, 53B, 53C_1, 53C_2) based on the measured value of the capacity and the measured value of the voltage, an inflection point voltage calculation unit (34, 34A to 34C) for calculating an actual inflection point voltage (Vix) which is the voltage of an inflection point in at least one of the charge characteristics and the discharge characteristics generated by the charge and discharge characteristic generation unit, a deviation amount calculation unit (35, 35A to 35C) for calculating a deviation amount (Dv) between the specific inflection point voltage and the actual inflection point voltage, and a determination unit (36, 36A to 36D) for determining the presence or absence of an abnormality related to the measurement of the battery cell based on the deviation amount.

[0015] 〔2〕In the battery system (1) described in 〔1〕 above, the determination unit (36) may determine that there is an abnormality when the deviation amount is equal to or greater than a predetermined threshold value (Dth).

[0016] 〔3〕In the battery system (1C) described in 〔1〕 above, the determination unit (36C) may determine that there is an abnormality when the polarity of the deviation amount in the charging characteristic matches the polarity of the deviation amount in the discharging characteristic, and the deviation amount in at least one of the charging characteristic and the discharging characteristic is equal to or greater than a predetermined threshold value (Dth).

[0017] 〔4〕In the battery system (1C) described in 〔1〕 above, the determination unit (36C) may determine that there is an abnormality when the actual inflection point voltage is smaller than the inherent inflection point voltage and the deviation amount is greater than a predetermined threshold value.

[0018] 〔5〕In the battery system (1D) described in 〔1〕 above, in the case where the charging characteristic is such that after the voltage of the battery cell reaches a specified voltage value near the charging termination voltage, it decreases to a minimum value and then increases, the determination unit (36D) may determine that there is an abnormality when there is no correlation between the voltage difference (ΔV), which is the difference between the specified voltage value and the minimum value, and the deviation amount, and the deviation amount is greater than a predetermined threshold value (Dth).

[0019] 〔6〕In the battery system (1D) described in 〔5〕 above, the storage unit (37C) stores correspondence relationship information (61) indicating the relationship between the voltage difference and the deviation amount, and the determination unit may determine the presence or absence of correlation between the voltage difference and the deviation amount based on the correspondence relationship information.

[0020] 〔7〕In the battery system (1E) described in 〔1〕 above, the charge-discharge control unit charges the battery cell by a CCCV charging method in which charging by a CV charging method is performed after charging by a CC charging method, the charge-discharge characteristic generation unit generates the charging characteristics when the battery cell is charged by the CCCV charging method, and the determination unit determines that there is an abnormality when there is no correlation between the change amount (ΔQ) of the capacity and the deviation amount (Dv) during the period in which charging by the CV charging method is performed in the charging characteristics, and the deviation amount is equal to or greater than a predetermined threshold value (Dth).

[0021] 〔8〕In the battery system according to 〔7〕 above, the storage unit further stores correspondence relationship information (81) indicating the relationship between the change amount of the capacity and the deviation amount, and the determination unit may determine the presence or absence of correlation between the change amount of the capacity and the deviation amount based on the correspondence relationship information.

[0022] 〔9〕In the battery system described in 〔1〕 above, the charge-discharge control unit charges the battery cell by a CCCV charging method in which charging by a CV charging method is performed after charging by a CC charging method, the charge-discharge characteristic generation unit generates the charging characteristics when the battery cell is charged by the CCCV charging method, and the determination unit determines that there is an abnormality when there is no correlation between the length (ΔT) of the period in which charging by the CV charging method is performed in the charging characteristics and the deviation amount (Dv), and the deviation amount is equal to or greater than a predetermined threshold value (Dth).

[0023] 〔10〕In the battery system according to 〔9〕 above, the storage unit further stores correspondence relationship information (81A) indicating the relationship between the length of the period and the deviation amount, and the determination unit may determine the presence or absence of correlation between the length of the period and the deviation amount based on the correspondence relationship information.

[0024] 〔11〕In the battery system according to any one of the above〔2〕to〔6〕, the charging characteristic may be a characteristic (Q-V characteristic) indicating a change in the voltage with respect to the capacity during charging of the battery cell, and the discharging characteristic may be a characteristic (Q-V characteristic) indicating a change in the voltage with respect to the capacity during discharging of the battery cell.

[0025] 〔12〕In the battery system according to any one of the above〔2〕to〔6〕, the charging characteristic may be a characteristic (SOC-V characteristic) indicating a change in the voltage with respect to the SOC of the battery cell during charging of the battery cell, and the discharging characteristic may be a characteristic (SOC-V characteristic) indicating a change in the voltage with respect to the SOC of the battery cell during discharging of the battery cell.

[0026] 〔13〕In the battery system according to any one of the above〔2〕to〔6〕, the charging characteristic may be a characteristic (dV / dQ-characteristic or dQ / dV-V characteristic) representing the relationship between the differential value, which is the ratio of the change amount of the voltage to the change amount of the capacity, and the voltage during charging of the battery cell, and the discharging characteristic may be a characteristic (dV / dQ-characteristic or dQ / dV-V characteristic) representing the relationship between the differential value, which is the ratio of the change amount of the voltage to the change amount of the capacity, and the voltage during discharging of the battery cell.

[0027] 〔14〕In the battery system according to any one of the above〔1〕to〔13〕, the determination unit may determine that there is the abnormality when the measured value of the voltage is constant with respect to the measured value of the capacity.

[0028] 〔15〕In the battery system according to any one of the above [1] to

[14] , as operation modes, there are a normal operation mode for controlling charge and discharge of the battery string based on the monitoring result and an abnormality determination mode for determining the presence or absence of an abnormality. The control unit further includes an operation mode setting unit (30) for setting the operation mode. When the operation mode is set to the abnormality determination mode by the operation mode setting unit, the charge and discharge control unit executes charging or discharging of the battery cell, the measurement value acquisition unit acquires measurement values of the capacity and the voltage of the battery cell during charging or discharging of the battery cell in the abnormality determination mode, the charge and discharge characteristic generation unit generates at least one of the charging characteristic and the discharging characteristic in the abnormality determination mode, the inflection point voltage calculation unit calculates the actual inflection point voltage in the abnormality determination mode, the determination unit calculates the deviation amount in the abnormality determination mode, and may determine the presence or absence of an abnormality based on the deviation amount.

[0029] 〔16〕An abnormality determination method according to a typical embodiment of the present invention includes a first step (S1) of acquiring measurement values of the capacity of at least one battery cell (21) constituting a battery string (20) and measurement values of the voltage of the battery cell during charging or discharging of the battery cell; a second step (S2) of generating at least one of the charging characteristic and the discharging characteristic of the battery cell based on the measurement values of the capacity and the voltage; a third step (S3) of calculating an actual inflection point voltage that is the voltage of an inflection point in at least one of the charging characteristic and the discharging characteristic generated in the second step; a fourth step (S4) of calculating a deviation amount between a specific inflection point voltage that is the voltage of a specific inflection point in the charging characteristic or the discharging characteristic and the actual inflection point voltage; and a fifth step (S5 to S13) of determining the presence or absence of an abnormality regarding the measurement of the battery cell based on the deviation amount calculated in the fourth step.

[0030] 〔17〕A program according to a typical embodiment of the present invention causes a computer to execute each step (S1 to S13) in the abnormality determination method described in the above

[16] .

[0031] 2. Specific Examples of Embodiments Hereinafter, specific examples of embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are given to the common components in each embodiment, and repeated descriptions are omitted.

[0032] ≪Embodiment 1≫ FIG. 1 is a diagram showing the configuration of a battery system according to Embodiment 1. The battery system 1 shown in FIG. 1 is installed, for example, within the premises of a power consumer such as a general household, a building, or a factory. The battery system 1 supplies power from the power supply unit 9 to the load 8 during normal times, and supplies power from the battery to the load 8 when a power outage occurs.

[0033] The power supply unit 9 supplies power to the battery system 1 and the load 8. The power supply unit 9 is, for example, a commercial power supply (power grid). In addition to the commercial power supply, the power supply unit 9 may include power generation facilities that generate power based on renewable energy such as photovoltaic power generation (PV: Photovoltaics).

[0034] The PCS (Power Conditioning System) 7 is controlled by a control unit 3 described later, and is a power conversion unit that mutually converts power among the power supply unit 9, the battery system 1, and the load 8, and controls the power transfer among the power supply unit 9, the battery system 1, and the load 8.

[0035] For example, the PCS 7 converts the alternating current power (AC) from the power supply unit 9 into direct current power (DC) and supplies it to the battery system 1. Also, the PCS 7 converts the direct current power (DC) supplied from the battery module 2 of the battery system 1 into alternating current power (AC) and supplies it to the load 8. The PCS 7 is configured to include, for example, a DC / DC converter, an AC / DC converter (AC / DC), and a switch circuit.

[0036] The load 8 is a device operable by the supplied power, and is, for example, electrical equipment installed within a customer's premises, an EV (Electric Vehicle), or the like.

[0037] The battery system 1 includes, for example, a battery module 2, a current sensor 22, a control unit 3, a monitoring unit 4, a protection circuit 5, and a DC / DC converter 6.

[0038] The battery module 2 has at least one battery string 20 including battery cells 21 configured to be capable of charging and discharging electric power. Note that the battery module 2 may have a configuration in which a plurality of battery strings 20 are connected in series and / or in parallel. Further, the battery system 1 may have a plurality of battery modules 2 connected in series and / or in parallel.

[0039] The battery string 20 has, for example, a structure in which n (n is an integer of 2 or more) battery cells 21 are connected in series. Examples of the battery cell 21 include a lead-acid battery, a lithium-ion secondary battery, and a sodium-ion secondary battery.

[0040] The current sensor 22 measures the current (charging current and discharging current) flowing through the battery string 20 in which the battery cells 21 are connected in series. The current sensor 22 is connected in series to the battery string 20. The current sensor 22 detects the current flowing through the battery string 20, converts the magnitude of the detected current into a digital value, and provides it to the monitoring unit 4 as a measurement result of the current of the battery cell 21.

[0041] In addition to the battery string 20, the battery module 2 has a voltage sensor 23 that measures the voltage of each battery cell 21.

[0042] The voltage sensor 23 includes, for example, a multiplexer (MUX) 24 that alternately selects and outputs the voltage across each battery cell, and an analog / digital conversion circuit (ADC) 25 that converts the voltage output from the multiplexer 24 into a digital value and outputs it.

[0043] The multiplexer 24 is a circuit that connects both ends of the battery cell specified by the selection signal SEL from the monitoring unit 4 to the two input terminals of the ADC 25 according to the selection signal SEL. The ADC 25 is a circuit that converts the voltage between the two input terminals into a digital value and outputs it. According to the voltage sensor 23, the voltage across both ends of one battery cell 21 specified by the selection signal SEL from the monitoring unit 4 is converted into a digital value and input to the monitoring unit 4 as the measurement result of the voltage of the battery cell 21.

[0044] The monitoring unit 4 is a device that sequentially acquires the physical quantities measured by the current sensor 22 and the voltage sensor 23 in the battery module 2, and monitors the state of the battery string 20 based on the physical quantities. The monitoring unit 4 is, for example, a BMU (Battery Management Unit). The monitoring unit 4 monitors the state of the battery cell 21 based on the current of the battery cell 21 measured by the current sensor 22 and the voltage of the battery cell 21 measured by the voltage sensor 23.

[0045] The monitoring unit 4 is composed of a program processing device such as a microcontroller (MCU) having a processor such as a CPU (Central Processing Unit), a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and peripheral circuits such as an I / F circuit.

[0046] The DC / DC converter 6 is a device that converts the input DC voltage into a DC voltage of a predetermined magnitude and outputs it. The DC / DC converter 6 is, for example, a bidirectional DC / DC converter. Specifically, when the battery string 20 is being charged, the DC / DC converter 6 converts the DC voltage supplied via the PCS 7 into a DC voltage of a predetermined magnitude according to the control signal from the control unit 3 and supplies it to the battery string 20. Also, when the battery string 20 is discharging, the DC / DC converter 6 converts the DC voltage output from the battery string 20 into a DC voltage of a predetermined magnitude according to the control signal from the control unit 3 and supplies it to the PCS 7.

[0047] The protection circuit 5 is connected between the DC / DC converter 6 and the battery module 2, and is a circuit that switches the supply and cut-off of power between the DC / DC converter 6 and the battery module 2. The protection circuit 5 is configured to include, for example, a relay, a power transistor, and the like.

[0048] For example, when the monitoring unit 4 detects an abnormality in the battery string 20, the monitoring unit 4 controls the protection circuit 5 to cut off the current path between the DC / DC converter 6 and the battery module 2. Similarly, when the control unit 3 detects an abnormality in the battery string 20, the control unit 3 controls the protection circuit 5 to cut off the current path between the DC / DC converter 6 and the battery module 2. Thereby, the power supply from the PCS7 to the battery string 20 or the power supply from the battery string 20 to the PCS7 is stopped.

[0049] The control unit 3 is a device that controls the overall operation of each component of the battery system 1. The control unit 3 is, for example, an EMS (Energy Management System). The control unit 3 is configured by a program processing device such as a microcontroller (MCU) having, for example, a processor such as a CPU, a storage device such as a RAM or a ROM, and peripheral circuits such as an I / F circuit.

[0050] The control unit 3 has a function of controlling the charge and discharge of the battery module 2 by controlling the PCS7, the DC / DC converter 6 (DC / DC), and the protection circuit 5, and a function of determining the presence or absence of an abnormality in the battery module 2 based on the measurement results of the voltage and current of the battery cell 21.

[0051] Here, an outline of the method for determining an abnormality in the battery module 2 by the control unit 3 will be described.

[0052] As described above, due to a failure of the voltage sensor 23 (the multiplexer 24 and the ADC 25), a voltage offset or a stuck voltage may occur. When such an event occurs, the battery system 1 may promote overcharging of the battery cell 21 or deterioration of the battery cell 21 by controlling the charge and discharge of the battery module 2 using an incorrect voltage measurement value. Therefore, the battery system 1 according to the first embodiment determines the presence or absence of an abnormality related to the measurement of the battery cell 21 by determining the presence or absence of a voltage offset and a stuck voltage.

[0053] First, an overview of the method for determining the presence or absence of a voltage offset will be described.

[0054] FIG. 2 is a diagram showing an example of the charging characteristics (Q-V) of a battery cell when a voltage offset occurs.

[0055] In FIG. 2, the horizontal axis represents the capacity Q of the battery cell 21, and the vertical axis represents the voltage V of the battery cell 21. Reference numeral 400 is a graph (Q-V characteristic) showing the change in voltage V with respect to the capacity Q, which is the theoretically (intrinsic) charging characteristic of the battery cell 21. Reference numeral 401 is a graph (Q-V characteristic) showing an example of the change in voltage V with respect to the capacity Q, which is the charging characteristic after the start of operation of the battery cell 21.

[0056] Generally, the charging and discharging characteristics of the battery cell 21, particularly the inflection points in the charging or discharging characteristics, are mainly determined by the type of battery, the battery active material, and the internal resistance of the battery, and are unique values with respect to the charging current or discharging current of the battery cell 21. In other words, if the battery module 2 is normal, the voltage at the inflection point in the charging or discharging characteristics will not change significantly even after the operation of the battery cell 21.

[0057] For example, in FIG. 2, the inflection point in the graph 400 of the Q-V characteristics specific to the battery cell 21 is designated as "P0", and the inflection point in the graph 401 of the Q-V characteristics of the battery cell 21 measured after the start of operation is designated as "Px". As described above, if the battery module 2 is normal, the inflection point P0 of the graph 400 and the inflection point Px of the graph 401 will substantially coincide even after the start of operation of the battery cell 21. However, when a voltage offset occurs due to a failure of the multiplexer 24 or the ADC 25 in the voltage sensor 23, as shown in FIG. 2, a deviation occurs between the inflection point P0 of the graph 400 and the inflection point Px of the graph 401.

[0058] Therefore, the battery system 1 according to Embodiment 1 determines the presence or absence of a voltage offset based on the deviation of the measured inflection point (Px) of the voltage V in the charging characteristics or discharging characteristics from the theoretical value (P0).

[0059] Next, an overview of the method for determining the presence or absence of voltage sticking will be described.

[0060] FIG. 3 is a diagram showing an example of the charging characteristics (Q-V) of a battery cell when voltage sticking occurs.

[0061] In FIG. 3, the horizontal axis represents the capacity Q of the battery cell 21, and the vertical axis represents the voltage V of the battery cell 21. The reference numeral 403 is a graph (Q-V characteristic) showing an example of the change in the voltage V with respect to the capacity Q, which is the charging characteristic after the start of operation of the battery cell 21.

[0062] As described above, after the start of operation of the battery cell 21, voltage sticking may occur due to a failure of the multiplexer 24 or the ADC 25 of the voltage sensor 23. When voltage sticking occurs, as shown in the graph 403 in FIG. 3, the voltage V becomes substantially constant regardless of the change in the capacity Q.

[0063] Therefore, the battery system 1 according to Embodiment 1 determines the presence or absence of voltage sticking based on the change in the voltage V in the measured charging characteristics or discharging characteristics.

[0064] Next, the configuration of the control unit 3 will be specifically described.

[0065] The control unit 3 has operation modes corresponding to the above-described two functions. That is, the battery system 1 (control unit 3) has, as operation modes, a normal operation mode and an abnormality determination mode. The normal operation mode is a mode for controlling the charge and discharge of the battery string based on the monitoring results (voltage measurement results and current measurement results) by the monitoring unit 4. The abnormality determination mode is a mode for determining the presence or absence of an abnormality regarding the measurement of the battery cell 21. For example, the battery system 1 operates in the normal operation mode in principle, and operates in the abnormality determination mode periodically or in response to a command from the outside.

[0066] FIG. 4 is a diagram showing the functional block configuration of the control unit 3 according to Embodiment 1.

[0067] As shown in FIG. 4, the control unit 3 includes, as functional blocks for realizing the above two functions (operation modes), an operation mode setting unit 30, a charge / discharge control unit 31, a measurement value acquisition unit 32, a charge / discharge characteristic generation unit 33, an inflection point voltage calculation unit 34, a deviation amount calculation unit 35, a determination unit 36, and a storage unit 37. These functional blocks are realized by the cooperation of the hardware resources constituting the control unit 3 with software. That is, the operation mode setting unit 30, the charge / discharge control unit 31, the measurement value acquisition unit 32, the charge / discharge characteristic generation unit 33, the inflection point voltage calculation unit 34, the determination unit 36, and the storage unit 37 are realized by the processor executing various operations according to a program stored in the storage device and controlling the peripheral circuits in a program processing device. Note that part or all of the operation mode setting unit 30, the charge / discharge control unit 31, the measurement value acquisition unit 32, the charge / discharge characteristic generation unit 33, the inflection point voltage calculation unit 34, the determination unit 36, and the storage unit 37 may be realized by dedicated hardware circuits.

[0068] The operation mode setting unit 30 is a functional unit that sets the operation mode of the battery system 1 described above. The operation mode setting unit 30 sets the normal operation mode or the abnormality determination mode as the operation mode. For example, the operation mode setting unit 30 sets the operation mode to the normal operation mode after the startup of the battery system 1, and sets the operation mode to the abnormality determination mode periodically or in response to an instruction from the outside.

[0069] For example, consider a case where, in a situation where the operation mode is set to the normal operation mode, the control unit 3 is instructed to execute an abnormality determination process from an external server connected via a communication network (not shown). In this case, the operation mode setting unit 30 switches the operation mode from the normal operation mode to the abnormality determination mode, and notifies other functional blocks that the operation mode has been set to the abnormality determination mode. Other functional blocks start operating in the abnormality determination mode. Alternatively, the control unit 3 may have a scheduler inside, and the scheduler may instruct the operation mode setting unit 30 to execute the abnormality determination process at a preset timing, thereby switching the operation mode from the normal operation mode to the abnormality determination mode.

[0070] The charge / discharge control unit 31 is a functional unit that controls the charge and discharge of the battery string 20 based on the monitoring results by the monitoring unit 4. Specifically, the charge / discharge control unit 31 controls the PCS 7, the DC / DC converter 6, and the protection circuit 5 based on the measured value of the voltage of the battery cell 21 and the measured value of the current of the battery cell 21, thereby performing the charge and discharge of the battery string 20 (battery cell 21) according to a predetermined charge method or discharge method. For example, the charge / discharge control unit 31 performs the charge of the battery string 20 based on various charge methods such as the CC charge method, the CV charge method, the CCCV charge method, the step charge method, and the CP method. Here, the step charge method refers to a method in which charging is started with a predetermined charge method (for example, the CC charge method), and the charge current is changed stepwise after the voltage of the battery reaches a specified voltage value.

[0071] The measurement value acquisition unit 32 is a functional unit that acquires measurement values of physical quantities of the battery cell 21 during charging or discharging of the battery cell 21. Based on the monitoring results by the monitoring unit 4, the measurement value acquisition unit 32 acquires measurement values of the voltage V of the battery cell 21 per unit time during charging or discharging. Based on the monitoring results by the monitoring unit 4, the measurement value acquisition unit 32 acquires measurement values of the capacity Q of the battery cell 21 per unit time during charging or discharging. For example, the measurement value acquisition unit 32 calculates the measurement value of the capacity Q of the battery cell 21 per unit time during charging or discharging by a known calculation method based on the measurement values of the voltage of the battery cell 21 and the measurement values of the current of the battery cell 21 per unit time during charging or discharging acquired from the monitoring results by the monitoring unit 4. Note that the monitoring unit 4 may calculate the measurement value of the capacity Q.

[0072] The measurement value acquisition unit 32 stores the acquired measurement value 51 of the voltage V of the battery cell 21 and the measurement value 52 of the capacity Q of the battery cell 21 in the storage unit 37 as the measurement result 50.

[0073] The charge / discharge characteristic generation unit 33 is a functional unit that generates the charge characteristics and discharge characteristics of the battery cell 21 based on the measurement values of the capacity Q and the voltage V of the battery cell 21.

[0074] In Embodiment 1, the charge characteristic of the battery cell 21 is a characteristic representing the relationship between the capacity Q and the voltage V during charging of the battery cell 21. The discharge characteristic of the battery cell 21 is a characteristic representing the relationship between the capacity Q and the voltage V during discharging of the battery cell 21.

[0075] The charge / discharge characteristic generation unit 33 generates at least one of the charge characteristic and the discharge characteristic of the storage battery cell 21 based on the measured value of the capacity Q and the measured value of the voltage V of the storage battery cell 21. For example, the charge / discharge characteristic generation unit 33 generates a plurality of data pairs associating the measured value of the capacity Q and the measured value of the voltage V of the storage battery cell 21 measured every unit time during charging of the storage battery cell 21 for each unit time, and stores them in the storage unit 37 as the charge characteristic 53 of the storage battery cell 21. Also, for example, the charge / discharge characteristic generation unit 33 generates a plurality of data pairs associating the measured value of the capacity Q and the measured value of the voltage V of the storage battery cell 21 measured every unit time during discharging of the storage battery cell 21 for each unit time, and stores them in the storage unit 37 as the discharge characteristic 53 of the storage battery cell 21.

[0076] The inflection point voltage calculation unit 34 is a functional unit that calculates the actual inflection point voltage indicating the magnitude of the inflection point of the voltage in at least one of the charge characteristic 53 and the discharge characteristic 53 generated by the charge / discharge characteristic generation unit 33. Specifically, the inflection point voltage calculation unit 34 refers to the charge characteristic (discharge characteristic) 53 generated by the charge / discharge characteristic generation unit 33 and detects the inflection point of the charge characteristic (discharge characteristic) 53. The inflection point voltage calculation unit 34 stores the voltage V at the detected inflection point in the storage unit 37 as the actual inflection point voltage Vix. For example, when the charge characteristic (discharge characteristic) 53 is represented by the graph 401 of the Q-V characteristic shown in FIG. 2, the inflection point voltage calculation unit 34 stores the voltage Vix at the inflection point Px of the graph 401 in the storage unit 37 as the information 56 of the actual inflection point voltage Vix.

[0077] The deviation amount calculation unit 35 is a functional unit that calculates the deviation amount between the specific inflection point voltage and the actual inflection point voltage Vix.

[0078] Here, the specific inflection point voltage is the voltage of the inflection point in the charge characteristic or the discharge characteristic that is specific to the storage battery cell 21 and is determined according to the type of the storage battery cell 21 and the like. For example, when the charge characteristic specific to the storage battery cell 21 is represented by the graph 400 of the Q-V characteristic shown in FIG. 2, the voltage Vi0 at the inflection point P0 in the graph 400 becomes the specific inflection point voltage Vi0. The information 54 of the specific inflection point voltage Vi0 is stored in the storage unit 37 in advance, for example.

[0079] Note that, as the intrinsic inflection point voltage Vi0, a theoretical value determined according to the type of the storage battery cell 21 may be used, or the charging characteristics or discharging characteristics of the storage battery cell 21 may be measured before the operation of the storage battery module 2 starts, and the voltage at the inflection point in the measured charging characteristics or discharging characteristics may be used.

[0080] The deviation amount calculation unit 35 is a functional unit that calculates the deviation amount Dv between the intrinsic inflection point voltage Vi0 and the actual inflection point voltage Vix calculated by the inflection point voltage calculation unit 34.

[0081] Here, the deviation amount Dv is an index indicating the degree of deviation of the actual inflection point voltage Vix with respect to the intrinsic inflection point voltage Vi0. The deviation amount Dv is, for example, a value based on the difference between the intrinsic inflection point voltage Vi0 and the actual inflection point voltage Vix, or the ratio between the intrinsic inflection point voltage Vi0 and the actual inflection point voltage Vix. In the present embodiment, as an example, it is assumed that the deviation amount Dv is a value obtained by subtracting the intrinsic inflection point voltage Vi0 from the actual inflection point voltage Vix.

[0082] For example, the deviation amount calculation unit 35 sets the value obtained by subtracting the intrinsic inflection point voltage Vi0 from the actual inflection point voltage Vix as the deviation amount Dv, and stores the information 56 of the calculated deviation amount Dv in the storage unit 37.

[0083] The determination unit 36 is a functional unit that determines the presence or absence of an abnormality related to the measurement of the storage battery cell 21. Specifically, the determination unit 36 determines the presence or absence of the occurrence of a voltage offset and the presence or absence of the occurrence of a voltage sticking.

[0084] The determination unit 36 compares the deviation amount Dv with a predetermined threshold value Dth in order to determine the occurrence of a voltage offset. The threshold value Dth is, for example, stored in advance in the storage unit 37. The determination unit 36 determines that a voltage offset has occurred when the deviation amount Dv (when the deviation amount Dv is based on the difference between the actual inflection point voltage Vix and the intrinsic inflection point voltage Vi0, the absolute value of the deviation amount Dv) is equal to or greater than the threshold value Dth, and determines that no voltage offset has occurred when the deviation amount Dv is smaller than the threshold value Dth.

[0085] Further, the determination unit 36 determines whether the measured value of the voltage V of the storage battery cell 21 is constant in order to determine the presence or absence of voltage sticking. For example, when the measured value of the voltage V is constant (fixed value) with respect to the change in the measured value of the capacity Q during charging or discharging of the storage battery cell 21, the determination unit 36 determines that voltage sticking has occurred. Alternatively, when the measured value of the voltage V during charging or discharging of the storage battery cell 21 is constant with respect to the change in time, the determination unit 36 determines that voltage sticking has occurred.

[0086] Here, the measured value of the voltage V being constant includes not only the measured value of the voltage V being a fixed value, but also the case where the change rate of the measured value of the voltage V with respect to the change in the capacity Q or time is within ±α%. α may be set in consideration of the error and safety of the system to be applied.

[0087] When the determination unit 36 determines that at least one of voltage offset and voltage sticking has occurred, it determines that there is an abnormality in the measurement of the storage battery cell 21. On the other hand, when the determination unit 36 determines that neither voltage offset nor voltage sticking has occurred, it determines that there is no abnormality in the measurement of the storage battery cell 21. The determination unit 36 stores the abnormality determination result (presence / absence of abnormality) 70 regarding the measurement of the storage battery cell 21 in the storage unit 37.

[0088] Note that when the determination unit 36 determines that there is an abnormality in the measurement of the storage battery cell 21, for example, it may transmit information indicating a warning regarding the storage battery module 2 to an external device such as a server. Alternatively, the determination unit 36 may display a warning regarding the storage battery module 2 on a monitor for information display provided in the storage battery system 1.

[0089] Next, the flow of the abnormality determination process regarding the measurement of the storage battery cell 21 by the storage battery system 1 according to Embodiment 1 will be described.

[0090] FIG. 5 is a flowchart showing an example of the flow of the abnormality determination process regarding the measurement of the storage battery cell 21 by the storage battery system 1 according to Embodiment 1.

[0091] For example, when the operation mode setting unit 30 in the control unit 3 sets the operation mode to the "abnormality determination mode", each functional unit of the control unit 3 starts operating in the "abnormality determination mode".

[0092] Specifically, first, the measurement value acquisition unit 32 acquires the measured values of the voltage V and the capacity Q during charging or discharging of the storage battery cell 21 by the method described above (step S1). For example, when the operation mode is set to the "abnormality determination mode", the charge and discharge control unit 31 executes charging or discharging of the storage battery cell 21, and the measurement value acquisition unit 32 sequentially acquires the measured values of the voltage V and the capacity Q of the selected storage battery cell 21. If the measurement of the charging characteristics or discharging characteristics of the storage battery cell 21 was completed during the immediately preceding normal operation mode and the measurement results at that time are stored in the storage unit 37, the measurement value acquisition unit 32 may read out the measured values of the voltage V and the capacity Q of the selected storage battery cell 21 from the storage unit 37.

[0093] Next, in the control unit 3, the charge and discharge characteristic generation unit 33 generates a Q - V characteristic as a charge characteristic (discharge characteristic) 53 representing the relationship between the capacity Q and the voltage V during charging or discharging of the storage battery cell 21 based on the measured values of the voltage V and the capacity Q acquired in step S1 by the method described above (step S2). Next, in the control unit 3, the inflection point voltage calculation unit 34 calculates the actual inflection point voltage Vix, which is the voltage of the inflection point in the charge characteristic (discharge characteristic) 53 generated in step S2, by the method described above (step S3).

[0094] Next, in the control unit 3, the deviation amount calculation unit 35 calculates the deviation amount Dv between the specific inflection point voltage Vi0 stored in the storage unit 37 and the actual inflection point voltage Vix calculated in step S3 by the method described above (step S4).

[0095] Next, in the control unit 3, the determination unit 36 compares whether or not the deviation amount Dv (absolute value) calculated in step S4 is greater than or equal to the threshold value Dth (step S5). When the deviation amount Dv (absolute value) is greater than or equal to the threshold value Dth (step S5: YES), the determination unit 36 determines that a voltage offset has occurred (step S6). On the other hand, when the deviation amount Dv (absolute value) is less than the threshold value Dth (step S5: NO), the determination unit 36 determines that no voltage offset has occurred (step S7).

[0096] After step S6 or step S7, in the control unit 3, the determination unit 36 determines whether or not the measured value of the voltage V is constant by the method described above (step S8). When the measured value of the voltage V is constant (step S8: YES), the determination unit 36 determines that voltage sticking has occurred (step S9). On the other hand, when the measured value of the voltage V is not constant (step S8: NO), the determination unit 36 determines that no voltage sticking has occurred (step S10).

[0097] After step S9 or step S10, in the control unit 3, the determination unit 36 determines whether or not at least one of the voltage offset and the voltage sticking has occurred (step S11). When at least one of the voltage offset and the voltage sticking has occurred (step S11: YES), the determination unit 36 determines that an abnormality has occurred in the measurement of the battery cell 21, and stores the abnormality determination result (abnormality present) 70 in the storage unit 37 (step S12). On the other hand, when neither the voltage offset nor the voltage sticking has occurred (step S11: NO), the determination unit 36 determines that no abnormality has occurred in the measurement of the battery cell 21, and stores the abnormality determination result (no abnormality) 70 in the storage unit 37 (step S13). The control unit 3 executes the above-described series of processes (steps S1 to S13) for each battery cell 21 constituting the battery string 20.

[0098] As described above, the battery system 1 according to Embodiment 1 generates at least one of charging characteristics and discharging characteristics based on the measured value of the capacity Q and the measured value of the voltage V of the battery cell 21, and calculates the actual inflection point voltage Vix in at least one of the generated charging characteristics and discharging characteristics. Then, as described above, the battery system 1 calculates the deviation amount Dv between the inherent inflection point voltage Vi0 and the actual inflection point voltage Vix, and determines the presence or absence of an abnormality related to the measurement of the battery cell 21 based on the deviation amount Dv. According to this, it is possible to determine the presence or absence of the occurrence of a voltage offset.

[0099] That is, as described above, when a voltage offset occurs, the voltage of the inflection point in the Q-V characteristics of the battery cell after the start of operation deviates from the voltage of the inflection point inherent to the battery cell. Therefore, as described above, when the deviation amount Dv is greater than (or equal to) a predetermined threshold value Dth, the determination unit 36 determines that a voltage offset has occurred, and when the deviation amount Dv is less than the predetermined threshold value Dth, it is determined that no voltage offset has occurred. According to this, it becomes possible to easily determine the presence or absence of the occurrence of a voltage offset due to a failure of the voltage sensor 23.

[0100] Also, in the battery system 1, when the measured value of the voltage V is constant with respect to the measured value of the capacity Q of the battery cell 21, the determination unit 36 determines that there is an abnormality. According to this, it becomes possible to easily determine the presence or absence of voltage sticking due to a failure of the voltage sensor 23 of the battery module 2.

[0101] As described above, according to the battery system 1 according to Embodiment 1, it is possible to easily determine the presence or absence of an abnormality related to the measurement of the battery cell. As a result, it is no longer necessary for an operator to regularly visit the location where the battery system is installed and measure the voltage of the battery cell using a reference power supply device or the like, as in the conventional case. Therefore, it is possible to suppress the working cost related to the abnormality determination regarding the measurement of the battery cell 21.

[0102] ≪Embodiment 2≫ FIG. 6 is a diagram showing the functional block configuration of the control unit 3A according to Embodiment 2.

[0103] The control unit 3A according to Embodiment 2 is different from the control unit 3 according to Embodiment 1 in that, as charging characteristics or discharging characteristics, it uses a characteristic representing the relationship between the differential value, which is the ratio of the change amount of the voltage V of the battery cell to the change amount of the capacity Q, and the voltage V. In other respects, it is the same as the control unit 3 according to Embodiment 1.

[0104] Here, the differential value, which is the ratio of the change amount of the voltage V of the battery cell to the change amount of the capacity Q, is the differential value dQ / dV, which is the ratio of the change amount of the capacity Q to the change amount of the voltage V of the battery cell, or the differential value dV / dQ, which is the ratio of the change amount of the voltage V to the change amount of the capacity Q of the battery cell.

[0105] In the present embodiment, a case where the differential value dV / dQ, which is the ratio of the change amount of the voltage V to the change amount of the capacity Q of the battery cell, is used will be described as an example.

[0106] In Embodiment 2, the charging characteristic is a characteristic representing the relationship between the differential value dV / dQ, which is the ratio of the change amount of the voltage V to the change amount of the capacity Q during charging of the battery cell 21, and the voltage V. The discharging characteristic is a characteristic representing the relationship between the differential value dV / dQ, which is the ratio of the change amount of the voltage V to the change amount of the capacity Q during discharging of the battery cell 21, and the voltage V.

[0107] FIG. 7 is a diagram showing the charging characteristic (dV / dQ-V) of the battery cell when a voltage offset occurs.

[0108] In FIG. 7, the horizontal axis represents the differential value dV / dQ, which is the ratio of the change in voltage V to the change in the capacity Q of the storage battery cell 21, and the vertical axis represents the voltage V of the storage battery cell 21. Reference numeral 500 is a graph (dV / dQ-V characteristic) showing the change in voltage V with respect to the differential value dV / dQ as the theoretical (intrinsic) charging characteristic of the storage battery cell 21. Reference numeral 501 is a graph (dV / dQ-V characteristic) showing an example of the change in voltage V with respect to the differential value dV / dQ as the charging characteristic after the start of operation of the storage battery cell 21.

[0109] As shown in FIG. 7, the dV / dQ-V characteristic representing the relationship between the differential value dV / dQ, which is the ratio of the change in voltage V to the change in the capacity Q of the storage battery cell, and the voltage V has an inflection point in the same manner as the Q-V characteristic representing the relationship between the capacity Q and the voltage V of the storage battery cell shown in FIG. 2, and the voltage of the inflection point is a value specific to the storage battery cell. Also, as shown in FIG. 7, the inflection point of the dV / dQ-V characteristic appears more prominently than the inflection point of the Q-V characteristic. The same can be said for the dQ / dV-V characteristic.

[0110] Therefore, the storage battery system 1A according to Embodiment 2 uses the dV / dQ-V characteristic (or dQ / dV-V characteristic) representing the relationship between the differential value dV / dQ (or dQ / dV), which is the ratio of the change in voltage V to the change in capacity Q of the storage battery cell, and the voltage V as the charging characteristic 53A or the discharging characteristic 53A to determine the presence or absence of a voltage offset.

[0111] Specifically, the storage battery system 1A according to Embodiment 2 has a control unit 3A instead of the control unit 3. In the control unit 3A, when the operation mode setting unit 30 sets the operation mode to the "abnormality determination mode", the charge / discharge characteristic generation unit 33A calculates the differential value dV / dQ, which is the ratio of the change in voltage V to the change in capacity Q, based on the measured value of voltage V and the measured value of capacity Q per unit time during charging or discharging of the storage battery cell 21.

[0112] Next, the charge / discharge characteristic generation unit 33A calculates at least one of the charge characteristics and discharge characteristics representing the relationship between the differential value dV / dQ and the voltage V based on the measured value of the voltage V measured every unit time during charging and discharging of the storage battery cell 21 and the differential value dV / dQ per unit time calculated by the above-described method.

[0113] For example, the charge / discharge characteristic generation unit 33A generates a plurality of data pairs associating the measured value of the voltage V measured every unit time during charging of the storage battery cell 21 with the differential value dV / dQ per unit time calculated by the above-described method for each unit time, and stores them in the storage unit 37 as the charge characteristic 53A of the storage battery cell 21.

[0114] Also, for example, the charge / discharge characteristic generation unit 33A generates a plurality of data pairs associating the measured value of the voltage V measured every unit time during discharging of the storage battery cell 21 with the differential value dV / dQ per unit time calculated by the above-described method for each unit time, and stores them in the storage unit 37 as the discharge characteristic 53A of the storage battery cell 21.

[0115] The inflection point voltage calculation unit 34A refers to the charge characteristic (discharge characteristic) 53A and detects the inflection point Px of the charge characteristic (discharge characteristic) 53A. As shown in FIG. 7, the inflection point voltage calculation unit 34A calculates the voltage of the detected inflection point Px of the graph 501 as the actual inflection point voltage Vix.

[0116] As shown in FIG. 7, the deviation amount calculation unit 35A calculates the deviation amount Dv between the intrinsic inflection point voltage Vi0 at the intrinsic inflection point of the dV / dQ-V characteristic representing the relationship between the differential value dV / dQ and the voltage V as the charge characteristic (discharge characteristic) 53A and the actual inflection point voltage Vix calculated by the inflection point voltage calculation unit 34A.

[0117] Here, information 54A on the inflection point voltage Vi0 at the specific inflection point Px of the charging characteristic (discharging characteristic) 53A representing the relationship between the differential value dV / dQ and the voltage V is stored in the storage unit 37A in advance, similar to the information 54 on the specific inflection point Vi0 according to Embodiment 1. Also, the method for calculating the deviation amount Dv by the deviation amount calculation unit 35A is the same as the calculation method by the deviation amount calculation unit 35 according to Embodiment 1.

[0118] The determination unit 36A determines whether a voltage offset has occurred based on the comparison result between the deviation amount Dv calculated by the deviation amount calculation unit 35A and the threshold value Dth. Here, the determination method by the determination unit 36A is the same as the determination method by the determination unit 36 according to Embodiment 1. Note that the determination unit 36A determines the presence or absence of voltage sticking by the same method as the determination unit 36 according to Embodiment 1.

[0119] As described above, the battery system 1A according to Embodiment 2 generates at least one of the charging characteristic 53A and the discharging characteristic 53A representing the relationship (dV / dQ-V or dQ / dV-V) between the differential value, which is the ratio of the change amount of the voltage V of the battery cell to the change amount of the capacity Q, and the voltage V, based on the measured value of the capacity Q and the measured value of the voltage V of the battery cell 21, and calculates the actual inflection point voltage Vix in the charging characteristic (discharging characteristic) 53A. Then, the battery system 1A calculates the deviation amount Dv between the specific inflection point voltage Vi0 and the actual inflection point voltage Vix regarding the dV / dQ-V characteristic or the dQ / dV-V characteristic as the charging characteristic (discharging characteristic) 53A, and determines the presence or absence of an abnormality in the measurement of the battery cell 21 based on the deviation amount Dv. According to this, similar to the battery system 1 according to Embodiment 1, it is possible to determine the presence or absence of the occurrence of a voltage offset.

[0120] In addition, since the battery system 1A according to the second embodiment uses the charge characteristic (discharge characteristic) 53A that represents the relationship between the differential value (dV / dQ or dQ / dV), which is the ratio of the change amount of the voltage V of the battery cell to the change amount of the capacity Q, and the voltage V, the voltage at the inflection point can be calculated more accurately. That is, as shown in FIG. 7, the inflection point in the dV / dQ-V characteristic appears more prominently than the inflection point in the Q-V characteristic, so it is easy to detect the inflection point. As a result, the voltage at the inflection point can be calculated more accurately, so that a more accurate abnormality determination can be realized.

[0121] <<Embodiment 3>> FIG. 8 is a diagram showing the functional block configuration of the control unit 3B according to the third embodiment.

[0122] The control unit 3B according to the third embodiment is different from the control unit 3 according to the first embodiment in that it uses, as the charge characteristic or discharge characteristic, a characteristic representing the relationship between the SOC (State Of Charge) of the battery cell and the voltage V, and is the same as the control unit 3 according to the first embodiment in other respects.

[0123] In the third embodiment, the charge characteristic is the SOC-V characteristic representing the relationship between the SOC and the voltage V during charging of the battery cell 21. The discharge characteristic is the SOC-V characteristic representing the relationship between the SOC and the voltage V during discharging of the battery cell 21.

[0124] FIG. 9 is a diagram showing the charge characteristic (SOC-V characteristic) of the battery cell when a voltage offset occurs.

[0125] In FIG. 9, the horizontal axis represents the SOC of the battery cell 21, and the vertical axis represents the voltage V of the battery cell 21. Reference numeral 600 is a graph (SOC-V characteristic) showing the change in the voltage V with respect to the SOC as the theoretically (intrinsic) charge characteristic of the battery cell 21. Reference numeral 601 is a graph (SOC-V characteristic) showing an example of the change in the voltage V with respect to the SOC as the charge characteristic after the start of operation of the battery cell 21.

[0126] As shown in FIG. 9, the charging characteristics (discharging characteristics) representing the relationship between the SOC of the battery cell and the voltage V have an inflection point in the same manner as the charging characteristics (discharging characteristics) representing the relationship between the capacity Q shown in FIG. 2 and the voltage V of the battery cell, and the voltage at the inflection point is a value specific to the battery cell.

[0127] Therefore, the battery system 1B according to Embodiment 3 determines the presence or absence of a voltage offset using the SOC-V characteristics representing the relationship between the SOC of the battery cell and the voltage V as the charging characteristics 53B or discharging characteristics 53B.

[0128] The battery system 1B according to Embodiment 3 has a control unit 3B instead of the control unit 3. In the control unit 3B, when the operation mode setting unit 30 sets the operation mode to the "abnormal determination mode", the charge / discharge characteristics generation unit 33B calculates the SOC of the battery cell 21 by a known calculation method based on the measured value of the capacity Q per unit time during charging or discharging of the battery cell 21.

[0129] Next, the charge / discharge characteristics generation unit 33B calculates at least one of the charging characteristics and discharging characteristics representing the relationship between the SOC and the voltage V based on the measured value of the voltage V measured per unit time during charging and discharging of the battery cell 21 and the SOC per unit time calculated by the above-described method.

[0130] For example, the charge / discharge characteristics generation unit 33B generates a plurality of data pairs associating the measured value of the voltage V measured per unit time during charging of the battery cell 21 with the SOC per unit time calculated by the above-described method for each unit time, and stores them in the storage unit 37 as the charging characteristics 53B of the battery cell 21.

[0131] Also, for example, the charge / discharge characteristics generation unit 33B generates a plurality of data pairs associating the measured value of the voltage V measured per unit time during discharging of the battery cell 21 with the SOC per unit time calculated by the above-described method for each unit time, and stores them in the storage unit 37 as the discharging characteristics 53A of the battery cell 21.

[0132] The inflection point voltage calculation unit 34B refers to the charging characteristic (discharging characteristic) 53B and detects the inflection point Px of the charging characteristic (discharging characteristic) 53B. For example, as shown in FIG. 9, the inflection point voltage calculation unit 34B calculates the voltage of the detected inflection point Px of the graph 601 as the actual inflection point voltage Vix.

[0133] As shown in FIG. 9, the deviation amount calculation unit 35B calculates a deviation amount Dv between the intrinsic inflection point voltage Vi0 at the intrinsic inflection point of the SOC-V characteristic as the charging characteristic (discharging characteristic) 53B and the actual inflection point voltage Vix calculated by the inflection point voltage calculation unit 34A.

[0134] Here, information 54B on the intrinsic inflection point voltage Vi0 at the intrinsic inflection point Px of the SOC-V characteristic of the storage battery cell 21 is stored in advance in the storage unit 37B in the same manner as the information 54 on the intrinsic inflection point Vi0 according to the first embodiment. Also, the method for calculating the deviation amount Dv by the deviation amount calculation unit 35B is the same as the calculation method by the deviation amount calculation unit 35 according to the first embodiment.

[0135] The determination unit 36B determines whether a voltage offset has occurred based on the comparison result between the deviation amount Dv calculated by the deviation amount calculation unit 35B and the threshold value Dth. Here, the determination method by the determination unit 36B is the same as the determination method by the determination unit 36 according to the first embodiment. Note that the determination unit 36B determines the presence or absence of voltage sticking by the same method as the determination unit 36 according to the first embodiment.

[0136] As described above, the storage battery system 1B according to the third embodiment calculates the SOC-V characteristic as the charging characteristic 53B or the discharging characteristic 53B based on the measured value of the capacity Q and the measured value of the voltage V of the storage battery cell 21, and calculates the actual inflection point voltage Vix in the charging characteristic (discharging characteristic) 53B. Then, the storage battery system 1B calculates a deviation amount Dv between the intrinsic inflection point voltage Vi0 and the actual inflection point voltage Vix regarding the SOC-V characteristic, and determines the presence or absence of an abnormality in the measurement of the storage battery cell 21 based on the deviation amount Dv. According to this, similar to the storage battery system 1 according to the first embodiment, it is possible to determine the presence or absence of the occurrence of a voltage offset.

[0137] <<Embodiment 4>> FIG. 10 is a diagram showing a functional block configuration of the control unit 3C according to Embodiment 4.

[0138] The control unit 3C according to Embodiment 4 is different from the control unit 3 according to Embodiment 1 in that it determines the presence or absence of a voltage offset based on the difference between the polarity of the deviation amount of the inflection point in the charging characteristic and the polarity of the deviation amount of the inflection point in the discharging characteristic, and is the same as the control unit 3 according to Embodiment 1 in other respects.

[0139] Generally, it is known that the internal resistance of a storage battery cell increases due to aging deterioration. When the internal resistance increases, the voltage of the inflection point in the charging characteristic and the discharging characteristic increases. That is, the inflection point (voltage) of the charging characteristic or discharging characteristic of the storage battery cell after the start of operation is shifted with respect to the inflection point (voltage) of the charging characteristic or discharging characteristic inherent to the storage battery cell. Therefore, in the case of the storage battery module 2 that has been in long-term operation, it is difficult to distinguish between the voltage offset caused by the failure of the voltage sensor 23 described above and the increase in the internal resistance.

[0140] On the other hand, the direction of the shift of the inflection point due to the increase in the internal resistance is different between the charging characteristic and the discharging characteristic. That is, in the case of the charging characteristic, the inflection point after the start of operation shifts in the increasing direction (positive side) with respect to the inherent inflection point, and in the case of the discharging characteristic, the inflection point after the start of operation shifts in the decreasing direction (negative side) with respect to the inherent inflection point. In contrast, the direction of the shift of the inflection point due to the voltage offset caused by the failure of the voltage sensor 23 is the same between the charging characteristic and the discharging characteristic.

[0141] Therefore, the storage battery system 1C according to Embodiment 4 determines the presence or absence of a voltage offset based on the difference between the polarity of the deviation amount of the inflection point in the charging characteristic and the polarity of the deviation amount of the inflection point in the discharging characteristic.

[0142] Specifically, the storage battery system 1C according to Embodiment 4 has a control unit 3C instead of the control unit 3.

[0143] In the control unit 3C, when the operation mode setting unit 30 sets the operation mode to the "abnormality determination mode", the charge / discharge characteristic generation unit 33C calculates the charge characteristics 53C_1 and the discharge characteristics 53C_1 representing the relationship between the capacity Q and the voltage V based on the measured value of the voltage V measured every unit time during charging and discharging of the storage battery cell 21 and the measured value of the capacity Q per unit time calculated by the same method as in the first embodiment.

[0144] For example, the charge / discharge characteristic generation unit 33C generates a plurality of data pairs associating the measured value of the voltage V measured every unit time during charging of the storage battery cell 21 with the measured value of the capacity Q for each unit time, and stores them in the storage unit 37C as the charge characteristics 53C_1 of the storage battery cell 21.

[0145] Also, for example, the charge / discharge characteristic generation unit 33C generates a plurality of data pairs associating the measured value of the voltage V measured every unit time during discharging of the storage battery cell 21 with the measured value of the capacity Q for each unit time, and stores them in the storage unit 37C as the discharge characteristics 53C_1 of the storage battery cell 21.

[0146] Note that the charge characteristics 53C_1 and the discharge characteristics 53C_2 are not limited to the Q-V characteristics, and may be the dV / dQ-V characteristics, dQ / dV-V characteristics, or SOC-V characteristics shown in the second and third embodiments.

[0147] The inflection point voltage calculation unit 34C refers to the charge characteristics 53C_1 and the discharge characteristics 53C_2 respectively, and detects the inflection point Px_1 of the charge characteristics 53C_1 and the inflection point Px_2 of the discharge characteristics 53C_2. The inflection point voltage calculation unit 34C calculates the voltage of the detected inflection point Px_1 of the charge characteristics 53C_1 as the actual inflection point voltage Vix_1, calculates the voltage of the detected inflection point Px_2 of the discharge characteristics 53C_1 as the actual inflection point voltage Vix_2, and stores them in the storage unit 37C respectively.

[0148] The deviation amount calculation unit 35C calculates a deviation amount Dv_1 between a specific inflection point voltage Vi0_1 at a specific inflection point of the charging characteristic (Q-V characteristic) of the battery cell 21 and an actual inflection point voltage Vix_1 of the charging characteristic 53C_1 (Q-V characteristic) calculated by the inflection point voltage calculation unit 34C. Further, the deviation amount calculation unit 35C calculates a deviation amount Dv_2 between a specific inflection point voltage Vi0_2 at a specific inflection point of the discharging characteristic (Q-V characteristic) of the battery cell 21 and an actual inflection point voltage Vix_2 of the discharging characteristic 53C_2 (Q-V characteristic) calculated by the inflection point voltage calculation unit 34C.

[0149] Here, information 54C on the specific inflection point voltages Vi0_1 and Vi0_2 is stored in advance in the storage unit 37C in the same manner as the information 54 on the specific inflection point Vi0 according to the first embodiment. Also, the method for calculating the deviation amounts Dv_1 and Dv_2 by the deviation amount calculation unit 35C is the same as the calculation method by the deviation amount calculation unit 35 according to the first embodiment.

[0150] The determination unit 36C determines that a voltage offset has occurred when the polarities (positive / negative) of the deviation amount Dv_1 in the charging characteristic and the deviation amount Dv_2 in the discharging characteristic match, and at least one of the deviation amounts Dv_1 and Dv_2 in the charging characteristic and the discharging characteristic is equal to or greater than predetermined thresholds Dth_1 and Dth_2. In other cases, the determination unit 36C determines that no voltage offset has occurred. The determination unit 36C determines the presence or absence of voltage sticking by the same method as the determination unit 36 according to the first embodiment.

[0151] Note that the determination unit 36C may determine that the internal resistance of the battery cell 21 has increased when the polarities (positive / negative) of the deviation amount Dv_1 in the charging characteristic and the deviation amount Dv_2 in the discharging characteristic are different, and at least one of the deviation amounts Dv_1 and Dv_2 in the charging characteristic and the discharging characteristic is equal to or greater than predetermined thresholds Dth_1 and Dth_2.

[0152] As described above, the battery system 1C according to Embodiment 4 determines the presence or absence of a voltage offset based on the difference between the polarity of the deviation amount of the inflection point in the charging characteristics of the battery cell 21 and the polarity of the deviation amount of the inflection point in the discharging characteristics. Therefore, even when the internal resistance increases due to the aging deterioration of the battery cell, it is possible to detect the occurrence of a voltage offset caused by the failure of the voltage sensor 23 with higher accuracy.

[0153] Among the voltage offsets caused by the failure of the voltage sensor 23, when a voltage offset occurs in which the inflection point after the start of operation shifts in the direction (negative side) in which the voltage decreases with respect to the unique inflection point, there is a risk that the battery cell 21 may be overcharged when the control unit 3 charges the battery cell 21.

[0154] Therefore, when detecting an abnormality of the voltage offset that may lead to overcharging, it is only necessary to determine the polarity of the deviation amount Dv. For example, the determination unit 36C may determine that a voltage offset (a voltage offset that may lead to overcharging) has occurred when the actual inflection point voltage Vix_1 (Vix_2) is smaller than the unique inflection point voltage Vi0_1 (Vi0_2) and the deviation amount Dv_1 (Dv_2) is equal to or greater than a predetermined threshold value Dth_1 (Dth_2).

[0155] ≪Embodiment 5≫ FIG. 11 is a diagram showing the functional block configuration of the control unit 3D according to Embodiment 5.

[0156] The control unit 3D according to Embodiment 5 is different from the control unit 3 according to Embodiment 1 in that it determines the presence or absence of a voltage offset by using the degree of voltage drop near the charge termination voltage in the charging characteristics, and is the same as the control unit 3 according to Embodiment 1 in other respects.

[0157] FIG. 12 is an enlarged view of a partial range of the charging characteristics (Q-V characteristics) shown in FIG. 2.

[0158] In FIG. 12, the horizontal axis represents the capacity Q of the storage battery cell, the left vertical axis in the drawing represents the voltage V of the storage battery cell, and the right vertical axis in the drawing represents the current I of the storage battery cell. Reference numeral 402 is a graph showing the change in current (charging current) I with respect to the capacity Q during charging of the storage battery cell. Reference numeral 401 is a graph showing an example of the change in voltage V with respect to the capacity Q after the start of operation of the storage battery cell. In FIG. 12, the range indicated by reference numeral 410 in FIG. 2 in the graph 401 is shown enlarged.

[0159] For example, when the storage battery cell is first charged by the CC charging method and then charged by the step charging method in which the charging voltage is gradually decreased after the voltage of the storage battery cell reaches the specified voltage value, the voltage V and current I of the storage battery cell change as shown in FIG. 12. That is, first, the storage battery cell is charged by the CC charging method so that the current I becomes substantially constant at the first value I1, and after the voltage V of the storage battery cell reaches the specified voltage value (for example, the maximum value Vmax), the storage battery cell is charged so that the current I becomes the second value I2 smaller than the first value I1. As a result, the charging characteristic (Q-V characteristic) of the storage battery cell decreases to the minimum value Vlm after the voltage V of the storage battery cell reaches the specified voltage value Vmax near the charging termination voltage, and then increases.

[0160] Here, it is considered that the voltage difference ΔV, which is the difference between the specified voltage value Vmax and the minimum value Vlm in the charging characteristic (Q-V characteristic), can be expressed as ΔV≒R×(I1-I2) when the internal resistance of the storage battery cell 21 is R. Therefore, it is considered that the voltage difference ΔV increases as the internal resistance of the storage battery cell 21 increases. Also, it is considered that the offset (deviation amount Dv) of the voltage at the inflection point increases as the internal resistance of the storage battery cell 21 increases. That is, when an offset (deviation amount Dv) of the voltage at the inflection point occurs due to an increase in the internal resistance of the storage battery cell, it is considered that there is a correlation between the voltage difference ΔV and the deviation amount Dv.

[0161] FIG. 13 is a diagram for explaining the correlation between the voltage difference ΔV and the deviation amount Dv.

[0162] In FIG. 13, the horizontal axis represents the voltage difference ΔV, and the vertical axis represents the amount of voltage deviation Dv at the inflection point in the charging characteristics and the discharging characteristics.

[0163] As described above, when the internal resistance of the storage battery cell increases from the initial stage of operation, the voltage difference ΔV and the deviation amount Dv both tend to increase (positive correlation). On the other hand, when a voltage offset occurs due to a failure of the voltage sensor 23, there is no correlation between the voltage difference ΔV and the deviation amount Dv. For example, even though the voltage difference ΔV is small, the deviation amount Dv may be large. Therefore, the storage battery system 1 according to Embodiment 5 determines the presence or absence of the occurrence of the voltage offset based on the presence or absence of the correlation between the voltage difference ΔV and the deviation amount Dv.

[0164] Specifically, the storage battery system 1D according to Embodiment 5 has a control unit 3D instead of the control unit 3. The control unit 3D further has a voltage difference calculation unit 38 in addition to the components of the control unit 3.

[0165] In the control unit 3D, when the operation mode setting unit 30 sets the operation mode to the "abnormal determination mode", similar to the control unit 3 according to Embodiment 1, the amount of voltage deviation Dv at the inflection point in the charging characteristics is calculated by the charge and discharge characteristic generation unit 33, the inflection point voltage calculation unit 34, and the deviation amount calculation unit 35.

[0166] Based on the charging characteristic (discharging characteristic) 53 generated by the charge and discharge characteristic generation unit 33, the voltage difference calculation unit 38 detects the specified voltage value Vmax and the minimum value Vlm of the voltage near the charge termination voltage, calculates the voltage difference ΔV (=Vmax - Vlm), and stores it in the storage unit 37D.

[0167] The determination unit 36D determines the presence or absence of a correlation between the voltage difference ΔV and the deviation amount Dv. For example, correspondence relation information 61 indicating the relationship between the voltage difference ΔV and the deviation amount Dv is stored in advance in the storage unit 37D. As shown in FIG. 13, the correspondence relation information 61 is information indicating the correlation between the voltage difference ΔV and the deviation amount Dv. The correspondence relation information 61 may be any information that can determine the presence or absence of a correlation between the voltage difference ΔV and the deviation amount Dv. For example, it may be a table shown in FIG. 13, or it may be a function indicating the relationship between the voltage difference ΔV and the deviation amount Dv.

[0168] The determination unit 36D determines the presence or absence of a correlation between the voltage difference ΔV and the deviation amount Dv based on the correspondence relation information 61. For example, as shown in FIG. 13, if a point determined by the voltage difference ΔV and the deviation amount Dv exists within the range indicated by reference numeral 502 among the ranges defined by the correspondence relation information 61, it is determined that there is no correlation between the voltage difference ΔV and the deviation amount Dv. If a point determined by the voltage difference ΔV and the deviation amount Dv exists in a range other than the range indicated by reference numeral 502, it is determined that there is a correlation between the voltage difference ΔV and the deviation amount Dv.

[0169] The determination unit 36D determines that a voltage offset has occurred when the voltage difference ΔV and the deviation amount Dv have no correlation with each other and the deviation amount Dv is equal to or greater than a predetermined threshold value Dth. Otherwise, it is determined that no voltage offset has occurred.

[0170] Note that the determination unit 36D may determine that the internal resistance of the storage battery cell 21 has increased when the voltage difference ΔV and the deviation amount Dv are correlated with each other and the deviation amounts Dv_1 and Dv_2 in at least one of the charging characteristics and the discharging characteristics are equal to or greater than predetermined threshold values Dth_1 and Dth_2.

[0171] As described above, the storage battery system 1D according to Embodiment 5 determines the presence or absence of the occurrence of a voltage offset based on the presence or absence of a correlation between the voltage difference ΔV and the deviation amount Dv in the charging characteristics of the storage battery cell. Therefore, even when the internal resistance increases due to the aging deterioration of the storage battery cell, it is possible to more accurately determine the occurrence of a voltage offset caused by a failure of the voltage sensor 23.

[0172] <<Embodiment 6>> FIG. 14 is a diagram showing a functional block configuration of the control unit 3E according to Embodiment 6.

[0173] The control unit 3E according to Embodiment 6 is different from the control unit 3D according to Embodiment 5 in that it determines the presence or absence of a voltage offset by using the amount of change in capacitance or the length of the period during which charging is performed in the CV charging method when the battery cell is charged by the CCCV charging method. In other respects, it is the same as the control unit 3D according to Embodiment 5.

[0174] FIG. 15 is a diagram showing an example of charging characteristics when a battery is charged by the CCCV charging method.

[0175] In FIG. 15, the horizontal axis represents the capacitance Q of the battery cell, the left vertical axis of the drawing represents the current I of the battery cell, and the right vertical axis of the drawing represents the voltage V of the battery cell. Reference numeral 601 is a graph showing the change in voltage V with respect to capacitance Q when a battery cell with an increasing internal resistance is charged by the CCCV charging method. Reference numeral 701 is a graph showing the change in current (charging current) I with respect to capacitance Q when a battery cell with an increasing internal resistance is charged by the CCCV charging method. Reference numeral 602 is a graph showing the change in voltage V with respect to capacitance Q when a battery cell with an increasing internal resistance is charged by the CCCV charging method. Reference numeral 702 is a graph showing the change in current (charging current) I with respect to capacitance Q when a battery cell with an increasing internal resistance is charged by the CCCV charging method.

[0176] For example, when a battery cell is charged by a CCCV charging method in which charging by a CV charging method is performed after charging by a CC charging method, the voltage V and current I of the battery cell change as shown in FIG. 15. That is, first, the current I is controlled to be substantially constant at a predetermined value (21 mA) by charging the battery cell by the CC charging method, so that the voltage V of the battery cell increases. Then, when the voltage V of the battery cell reaches a specified voltage value (3.65 V), the charging method switches from the CC charging method to the CV charging method. By controlling the voltage V to be constant by the CV charging method, the current I decreases. And when the current I decreases to a predetermined value (2.5 mA), the charging of the battery cell stops.

[0177] Here, in the charging characteristics (Q-V characteristics, Q-I characteristics) in the CCCV charging method, the change amount ΔQ of the capacity during the charging period by the CV charging method is considered to be correlated with the internal resistance of the battery cell. For example, as shown in FIG. 15, when comparing the change amount ΔQ1 of the capacity during the charging period by the CV charging method of a battery cell whose internal resistance has not increased and the change amount ΔQ2 of the capacity during the charging period by the CV charging method of a battery cell whose internal resistance has increased, it is understood that the change amount ΔQ2 of the capacity of the battery cell whose internal resistance has increased is larger than the change amount ΔQ1 of the capacity of the battery cell whose internal resistance has not increased (ΔQ2>ΔQ1). That is, as the internal resistance of the battery cell increases due to aging deterioration, the change amount ΔQ of the capacity during the charging period by the CV charging method tends to increase.

[0178] On the other hand, as described above, the larger the internal resistance of the battery cell, the larger the voltage offset (deviation amount Dv) at the inflection point of the charging characteristics. Therefore, when a voltage offset (deviation amount Dv) occurs at the inflection point due to an increase in the internal resistance of the battery cell, it is considered that there is a correlation between the change amount ΔQ of the capacity during the charging period by the CV charging method and the deviation amount Dv.

[0179] FIG. 16 is a diagram for explaining the correlation between the change amount ΔQ of the capacity and the deviation amount Dv during the charging period by the CV charging method in the CCCV charging method.

[0180] In FIG. 16, the horizontal axis represents the change amount ΔQ of the capacity, and the vertical axis represents the deviation amount Dv of the voltage at the inflection point in the charging characteristics and the discharging characteristics.

[0181] As described above, when the internal resistance of the storage battery cell increases from the beginning of operation, both the change amount ΔQ of the capacity and the deviation amount Dv during the charging period by the CV charging method in the CCCV charging method tend to increase (positive correlation). On the other hand, when a voltage offset occurs due to a failure of the voltage sensor 23, there is no correlation between the change amount ΔQ of the capacity and the deviation amount Dv. For example, the deviation amount Dv may become large even though the change amount ΔQ of the capacity is small. Therefore, the storage battery system 1 according to Embodiment 5 determines the presence or absence of the occurrence of the voltage offset based on the presence or absence of the correlation between the change amount ΔQ of the capacity and the deviation amount Dv.

[0182] Specifically, the storage battery system 1E according to Embodiment 6 has a control unit 3E instead of the control unit 3. The control unit 3E further has a difference calculation unit 39 in addition to the components of the control unit 3.

[0183] In the control unit 3E, when the operation mode setting unit 30 sets the operation mode to the "abnormal determination mode", the charge and discharge control unit 31 charges the storage battery cell 21 by the CCCV charging method. Then, similar to the control unit 3 according to Embodiment 1, the deviation amount Dv of the voltage at the inflection point in the charging characteristics (discharging characteristics) 53 when the storage battery cell 21 is charged by the CCCV charging method is calculated by the charge and discharge characteristic generation unit 33, the inflection point voltage calculation unit 34, and the deviation amount calculation unit 35.

[0184] The difference calculation unit 39 calculates the change amount ΔQ of the capacitance during the charging period in the CV charging method in the charging characteristics 53 generated by the charge and discharge characteristics generation unit 33. For example, the difference calculation unit 39 calculates the difference between the measured value of the capacitance at the time when switching from the CC charging method to CV charging and the measured value of the capacitance at the time when the CV charging ends in the charging characteristics (discharge characteristics) 53. The difference calculation unit 39 stores the calculated difference in the storage unit 37E as the information 80 on the change amount ΔQ of the capacitance.

[0185] The determination unit 36D determines the presence or absence of a correlation between the change amount ΔQ of the capacitance and the deviation amount Dv. For example, the correspondence relationship information 81 indicating the relationship between the change amount ΔQ of the capacitance and the deviation amount Dv is stored in advance in the storage unit 37E. As shown in FIG. 16, the correspondence relationship information 81 is information indicating the correlation between the change amount ΔQ of the capacitance and the deviation amount Dv. The correspondence relationship information 81 may be information capable of determining the presence or absence of a correlation between the change amount ΔQ of the capacitance and the deviation amount Dv. For example, it may be a table shown in FIG. 16, or may be a function indicating the relationship between the change amount ΔQ of the capacitance and the deviation amount Dv.

[0186] The determination unit 36E determines the presence or absence of a correlation between the change amount ΔQ of the capacitance and the deviation amount Dv based on the correspondence relationship information 81. For example, as shown in FIG. 16, when a point determined by the change amount ΔQ of the capacitance and the deviation amount Dv exists in the range indicated by the reference numeral 802 among the ranges defined by the correspondence relationship information 81, it is determined that there is no correlation between the change amount ΔQ of the capacitance and the deviation amount Dv. When a point determined by the change amount ΔQ of the capacitance and the deviation amount Dv exists in a range other than the range indicated by the reference numeral 802, it is determined that there is a correlation between the change amount ΔQ of the capacitance and the deviation amount Dv.

[0187] The determination unit 36E determines that a voltage offset has occurred when the change amount ΔQ of the capacitance and the deviation amount Dv have no correlation with each other and the deviation amount Dv is equal to or greater than a predetermined threshold value Dth, and determines that no voltage offset has occurred in other cases.

[0188] Note that the determination unit 36E may determine that the internal resistance of the storage battery cell 21 has increased when the change amount ΔQ of the capacity and the deviation amount Dv are correlated with each other, and the deviation amounts Dv_1 and Dv_2 in at least one of the charging characteristics and the discharging characteristics are equal to or greater than the predetermined threshold values Dth_1 and Dth_2.

[0189] As described above, the storage battery system 1E according to the sixth embodiment determines the presence or absence of the occurrence of the voltage offset based on the presence or absence of the correlation between the change amount ΔQ of the capacity and the deviation amount Dv during the charging period by the CV charging method within the CCCV charging method. Therefore, even when the internal resistance increases due to the secular deterioration of the storage battery cell, it is possible to more accurately determine the occurrence of the voltage offset caused by the failure of the voltage sensor 23.

[0190] In the above embodiment, the case where the presence or absence of the occurrence of the voltage offset is determined based on the presence or absence of the correlation between the change amount ΔQ of the capacity and the deviation amount Dv during the charging period by the CV charging method within the CCCV charging method has been described. However, the presence or absence of the occurrence of the voltage offset may be determined based on the presence or absence of the correlation between the length ΔT of the charging period by the CV charging method within the CCCV charging method and the deviation amount Dv.

[0191] As described above, there is a positive correlation between the internal resistance of the storage battery cell and the change amount ΔQ of the capacity during the charging period by the CV charging method within the CCCV charging method. On the other hand, the length ΔT of the charging period by the CV charging method within the CCCV charging method tends to be longer as the change amount ΔQ of the capacity becomes larger. Therefore, there is also a positive correlation between the internal resistance of the storage battery cell and the length ΔT of the charging period by the CV charging method within the CCCV charging method.

[0192] Therefore, instead of the change amount ΔQ of the capacity during the charging period by the CV charging method within the CCCV charging method, the length ΔT of the charging period by the CV charging method within the CCCV charging method may be used to determine the presence or absence of the occurrence of the voltage offset.

[0193] For example, the difference calculation unit 39 calculates the change amount ΔQ of the capacitance during the charging period in the charging characteristic 53 generated by the charge and discharge characteristic generation unit 33 using the CV charging method. For example, the difference calculation unit 39 calculates the time difference between the time point when the charging method is switched from the CC charging method to the CV charging and the time point when the CV charging ends in the charging characteristic 53. The difference calculation unit 39 stores the time difference in the storage unit 37E as the information 80A on the length ΔT of the charging period in the CV charging method.

[0194] The determination unit 36E determines the presence or absence of a correlation between the length ΔT of the charging period and the deviation amount Dv. For example, the correspondence relationship information 81A indicating the relationship between the length ΔT of the charging period and the deviation amount Dv is stored in advance in the storage unit 37E. The correspondence relationship information 81 is information indicating the correlation between the length ΔT of the charging period and the deviation amount Dv, similar to the correspondence relationship information 81 shown in FIG. 16. The correspondence relationship information 81A may be information capable of determining the presence or absence of a correlation between the length ΔT of the charging period and the deviation amount Dv. For example, it may be a table similar to FIG. 16, or it may be a function indicating the relationship between the length ΔT of the charging period and the deviation amount Dv.

[0195] The determination unit 36E determines the presence or absence of a correlation between the length ΔT of the charging period and the deviation amount Dv based on the correspondence relationship information 81A by the same method as the determination unit 36. The determination unit 36E determines that a voltage offset has occurred when the length ΔT of the charging period and the deviation amount Dv have no correlation with each other and the deviation amount Dv is equal to or greater than a predetermined threshold value Dth, and determines that no voltage offset has occurred in other cases.

[0196] According to this, even when the internal resistance increases due to the aging deterioration of the storage battery cell, it is possible to more accurately determine the occurrence of a voltage offset caused by the failure of the voltage sensor 23.

[0197] ≪Expansion of the Embodiment≫ As described above, the invention made by the present inventor has been specifically described based on the embodiments. However, it goes without saying that the present invention is not limited thereto and can be variously modified without departing from the gist thereof.

[0198] For example, the above flowchart shows an example for explaining the operation and is not limited thereto. That is, the steps shown in each figure of the flowchart are specific examples and are not limited to this flow. For example, the order of some processes may be changed, other processes may be inserted between each process, or some processes may be performed in parallel.

Description of Reference Numerals

[0199] 1, 1A to 1D... battery system, 2... battery module, 3, 3A to 3D... control unit, 4... monitoring unit, 5... protection circuit, 6... DC / DC converter, 8... load, 9... power supply unit, 20... battery string, 21... battery cell, 22... current sensor, 23... voltage sensor, 24... multiplexer (MUX), 25... analog / digital conversion circuit (ADC), 30... operation mode setting unit, 31... charge / discharge control unit, 32... measurement value acquisition unit, 33, 33A to 33C... charge / discharge characteristic generation unit, 34, 34A to 34C... inflection point voltage calculation unit, 35, 35A to 35C... deviation amount calculation unit, 36, 36A to 36D... determination unit, 37, 37A to 37D... storage unit, 38... voltage difference calculation unit, 39... difference calculation unit, 50... measurement result, 51... measured value of voltage, 52... measured value of capacity, 53, 53C_1, 53C_2... charge characteristic (discharge characteristic), 53A... charge characteristic (discharge characteristic), 53B... charge characteristic (discharge characteristic), 54, 54A to 54C... inherent inflection point voltage (Vi0), 56... deviation amount Dv, 57... threshold value Dth, 61... correspondence relationship information, 70... abnormality determination result, Vlm... minimum value, Vmax... specified voltage value, ΔV... voltage difference.

Claims

1. A battery string including at least one battery cell, a voltage sensor for measuring the voltage of the battery cell, a current sensor for measuring the current flowing through the battery cell, a monitoring unit for monitoring the state of the battery cell based on the measured value of the voltage measured by the voltage sensor and the measured value of the current measured by the current sensor, a control unit for controlling the charge and discharge of the battery string and determining the presence or absence of an abnormality related to the measurement of the battery string based on the monitoring result by the monitoring unit, wherein the control unit is a charge and discharge control unit for controlling the charge and discharge of the battery string based on the monitoring result by the monitoring unit, is a storage unit for storing a specific inflection point voltage which is the voltage of a specific inflection point in at least one of the charging characteristics and the discharging characteristics of the battery cell, is a measured value acquisition unit for acquiring the measured value of the capacity of the battery cell and the measured value of the voltage during charging or discharging of the battery cell based on the monitoring result by the monitoring unit, is a charge and discharge characteristic generation unit for generating at least one of the charging characteristics and the discharging characteristics based on the measured value of the capacity and the measured value of the voltage, is an inflection point voltage calculation unit for calculating an actual inflection point voltage which is the voltage of an inflection point in at least one of the charging characteristics and the discharging characteristics generated by the charge and discharge characteristic generation unit, is a deviation amount calculation unit for calculating the deviation amount between the specific inflection point voltage and the actual inflection point voltage, and has a determination unit for determining the presence or absence of an abnormality related to the measurement of the battery cell based on the deviation amount. A battery system.

2. The battery system according to Claim 1, wherein the determination unit determines that the abnormality exists when the deviation amount is equal to or greater than a predetermined threshold value. A battery system.

3. The battery system according to Claim 1, wherein the determination unit determines that the abnormality exists when the polarity of the deviation amount in the charging characteristics and the polarity of the deviation amount in the discharging characteristics are the same, and the deviation amount in at least one of the charging characteristics and the discharging characteristics is equal to or greater than a predetermined threshold value. A battery system.

4. The battery system according to Claim 1, wherein the determination unit determines that the abnormality exists when the actual inflection point voltage is smaller than the specific inflection point voltage and the deviation amount is equal to or greater than a predetermined threshold value. A battery system.

5. The battery system according to Claim 1, When the charging characteristic is such that after the voltage of the storage battery cell reaches a specified voltage value near the charging termination voltage, it drops to a minimum value and then rises, the determination unit determines that there is an abnormality when there is no correlation between the voltage difference, which is the difference between the specified voltage value and the minimum value, and the deviation amount, and the deviation amount is equal to or greater than a predetermined threshold value Storage battery system.

6. In the storage battery system according to claim 5, the storage unit further stores correspondence relationship information indicating the relationship between the voltage difference and the deviation amount, the determination unit determines the presence or absence of correlation between the voltage difference and the deviation amount based on the correspondence relationship information Storage battery system.

7. In the storage battery system according to claim 1, the charge and discharge control unit charges the storage battery cell by a CCCV charging method in which charging by a CV charging method is performed after charging by a CC charging method, the charge and discharge characteristic generation unit generates the charging characteristic when the storage battery cell is charged by the CCCV charging method, the determination unit determines that there is an abnormality when there is no correlation between the change amount of the capacity and the deviation amount during the period in which charging by the CV charging method is performed in the charging characteristic, and the deviation amount is equal to or greater than a predetermined threshold value Storage battery system.

8. In the storage battery system according to claim 7, the storage unit further stores correspondence relationship information indicating the relationship between the change amount of the capacity and the deviation amount, the determination unit determines the presence or absence of correlation between the change amount of the capacity and the deviation amount based on the correspondence relationship information Storage battery system.

9. In the storage battery system according to claim 1, the charge and discharge control unit charges the storage battery cell by a CCCV charging method in which charging by a CV charging method is performed after charging by a CC charging method, the charge and discharge characteristic generation unit generates the charging characteristic when the storage battery cell is charged by the CCCV charging method, the determination unit determines that there is an abnormality when there is no correlation between the length of the period in which charging by the CV charging method is performed in the charging characteristic and the deviation amount, and the deviation amount is equal to or greater than a predetermined threshold value Storage battery system.

10. In the storage battery system according to claim 9, the storage unit further stores correspondence relationship information indicating the relationship between the length of the period and the deviation amount, the determination unit determines the presence or absence of correlation between the length of the period and the deviation amount based on the correspondence relationship information Storage battery system.

11. In the battery system according to any one of Claims 2 to 10, the charging characteristic is a characteristic indicating a change in the voltage with respect to the capacity during charging of the battery cell, and the discharging characteristic is a characteristic indicating a change in the voltage with respect to the capacity during discharging of the battery cell Battery system.

12. In the battery system according to any one of Claims 2 to 6, the charging characteristic is a characteristic indicating a change in the voltage with respect to the state of charge (SOC) of the battery cell during charging of the battery cell, and the discharging characteristic is a characteristic indicating a change in the voltage with respect to the state of charge (SOC) of the battery cell during discharging of the battery cell Battery system.

13. In the battery system according to any one of Claims 2 to 6, the charging characteristic is a characteristic representing the relationship between the differential value, which is the ratio of the change amount of the voltage to the change amount of the capacity during charging of the battery cell, and the voltage, and the discharging characteristic is a characteristic representing the relationship between the differential value, which is the ratio of the change amount of the voltage to the change amount of the capacity during discharging of the battery cell, and the voltage Battery system.

14. In the battery system according to Claim 1, the determination unit determines that there is the abnormality when the measured value of the voltage is constant with respect to the measured value of the capacity Battery system.

15. In the battery system according to Claim 1, as operation modes, there are a normal operation mode for controlling charging and discharging of the battery string based on the monitoring result and an abnormality determination mode for determining the presence or absence of an abnormality, the control unit further includes an operation mode setting unit for setting the operation mode, when the operation mode is set to the abnormality determination mode by the operation mode setting unit, the charge / discharge control unit executes charging or discharging of the battery cell, the measurement value acquisition unit acquires the measured value of the capacity and the measured value of the voltage during charging or discharging of the battery cell in the abnormality determination mode, the charge / discharge characteristic generation unit generates at least one of the charging characteristic and the discharging characteristic in the abnormality determination mode, the inflection point voltage calculation unit calculates the actual inflection point voltage in the abnormality determination mode, the determination unit calculates the deviation amount in the abnormality determination mode, and determines the presence or absence of the abnormality based on the deviation amount Battery system.

16. A first step of obtaining a measured value of the capacity of the at least one battery cell constituting the battery string and a measured value of the voltage of the battery cell during charging or discharging of the battery cell; A second step of generating at least one of the charging characteristics and the discharging characteristics of the battery cell based on the measured value of the capacity and the measured value of the voltage; A third step of calculating an actual inflection point voltage which is the voltage of the inflection point in at least one of the charging characteristics and the discharging characteristics generated in the second step; A fourth step of calculating a deviation amount between the actual inflection point voltage and an inherent inflection point voltage which is the voltage of the inherent inflection point in at least one of the charging characteristics and the discharging characteristics; A fifth step of determining the presence or absence of an abnormality regarding the measurement of the battery cell based on the deviation amount calculated in the fourth step, and including An abnormality determination method.

17. A program for causing a computer to execute each step in the abnormality determination method according to Claim 16 Program.

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