Battery control device and program

Abstract

A storage battery (20, 21) has, in the battery characteristics thereof, a gentle region as a region in which a change in the terminal voltage with respect to a change in the remaining capacity is relatively small, and a steep region as a region in which a change in the terminal voltage with respect to a change in the remaining capacity is relatively large. A battery control device (30) comprises: an impedance measurement unit for measuring the impedance of the storage battery; an energization history acquisition unit for acquiring, as energization history information, a history of energization of the storage battery from when the impedance is measured until after the measurement; a region determination unit for determining that the terminal voltage of the storage battery has transitioned from the gentle region to the steep region when the storage battery is energized after the measurement of the impedance; and a capacity calculation unit for, if it is determined by the region determination unit that the terminal voltage of the storage battery has shifted to the steep region, calculating the remaining capacity at the time of impedance measurement by the impedance measurement unit on the basis of the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region and the energization history information.

Description

Battery control device and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-099305, filed on June 20, 2024, the contents of which are incorporated herein by reference.

[0002] The disclosure in this specification relates to a battery control device and a program.

[0003] Various techniques for calculating the remaining capacity of a storage battery have been proposed. For example, a technique has been disclosed in which a secondary battery is provided with a temperature sensor for detecting the battery temperature and a sensor for detecting the impedance (internal resistance) of the secondary battery, and the capacity of the secondary battery is estimated based on the battery temperature and impedance (see Patent Document 1). Furthermore, for a storage battery, there is a correlation between the remaining capacity and the terminal voltage, and a technique for calculating the remaining capacity based on the open circuit voltage (OCV), which is the terminal voltage of the storage battery, is known.

[0004] Japanese Patent Application Laid-Open No. 2020-34383

[0005] Regarding the relationship between the remaining capacity and terminal voltage of a storage battery, the change in terminal voltage relative to the change in remaining capacity is small in most of the usage range of the storage battery. Therefore, when calculating the remaining capacity based on the terminal voltage of the storage battery, the calculation accuracy of the remaining capacity may be low. For example, when diagnosing deterioration of a storage battery based on the impedance and remaining capacity of the storage battery, it is necessary to know the remaining capacity at the time of impedance measurement. However, there is a concern that the accuracy of the deterioration diagnosis may be reduced due to the low accuracy of the calculation of the remaining capacity at the time of impedance measurement.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a battery control device and a program that can appropriately calculate the remaining capacity of a storage battery when measuring impedance.

[0007] The present disclosure provides a battery control device applicable to a power supply system having a storage battery, wherein the storage battery has battery characteristics indicating the relationship between remaining capacity and terminal voltage, which have a gradual region where the change in terminal voltage relative to a change in remaining capacity is relatively small, and a steep region where the change in terminal voltage relative to a change in remaining capacity is relatively large; the battery control device includes: an impedance measurement unit that measures the impedance of the storage battery; a current history acquisition unit that acquires a history of current flow through the storage battery from the time of measurement of the impedance to after the measurement as current flow history information; a region determination unit that determines, when current is flowing through the storage battery after measurement of the impedance, that the terminal voltage of the storage battery has transitioned from the gradual region to the steep region; and a capacity calculation unit that, when it is determined by the region determination unit that the terminal voltage of the storage battery has transitioned to the steep region, calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region and the current flow history information.

[0008] When determining the impedance and remaining capacity of a battery, it is conceivable that the impedance of the battery is measured in an arbitrary state and the remaining capacity is calculated based on the terminal voltage of the battery at the time of the impedance measurement. However, if the battery has battery characteristics that include a gradual region in which the change in terminal voltage relative to the change in remaining capacity is relatively small and a steep region in which the change in terminal voltage relative to the change in remaining capacity is relatively large, there is a concern that the accuracy of the remaining capacity calculated in the gradual region may be low.

[0009] In this regard, in the above configuration, the history of current application to the storage battery from the time of impedance measurement to the time after the measurement is acquired as current application history information, and it is determined that the terminal voltage of the storage battery has transitioned from a gradual change region to a steep change region when the storage battery is current applied after the impedance measurement. Then, when it is determined that the terminal voltage of the storage battery has transitioned to the steep change region, the remaining capacity at the time of the impedance measurement is calculated based on the remaining capacity of the storage battery corresponding to the terminal voltage in the steep change region and the current application history information after the impedance measurement. In this case, in the steep change region of the battery characteristics, the accuracy of calculation of the remaining capacity based on the terminal voltage of the storage battery is improved, allowing for highly accurate calculation of the remaining capacity. Furthermore, the current application history information after the impedance measurement allows for the amount of change in the remaining capacity since the impedance measurement to be determined. Therefore, the remaining capacity at the time of impedance measurement can be calculated using the remaining capacity calculated in the steep change region and the current application history information after the impedance measurement. As a result, the remaining capacity of the storage battery at the time of impedance measurement can be accurately calculated.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a diagram showing the configuration of a power supply system, Fig. 2 is a diagram showing a correlation map used in deterioration diagnosis, Fig. 3 is a diagram showing the relationship between remaining capacity and terminal voltage of a cell, Fig. 4 is a diagram showing the relationship between remaining capacity and terminal voltage of a cell, Fig. 5 is a diagram showing the relationship between remaining capacity and impedance, Fig. 6 is a flowchart showing a procedure for diagnosing deterioration of a cell, Fig. 7 is a flowchart showing a procedure for updating the correlation map in a second embodiment, Fig. 8 is a diagram showing the relationship between remaining capacity and terminal voltage of a cell, Fig. 9 is a flowchart showing a procedure for diagnosing deterioration of a cell in a third embodiment, Fig. 10 is a diagram showing the relationship between remaining capacity and terminal voltage of a cell, Fig. 11 is a flowchart showing a procedure for diagnosing deterioration of a cell in a fourth embodiment, Fig. 12 is a diagram showing the relationship between remaining capacity and terminal voltage of a cell, and Fig. 13 is a diagram showing the relationship between remaining capacity and terminal voltage of a cell.

[0011] First Embodiment A first embodiment will now be described with reference to the drawings. In this embodiment, a power supply system 10 mounted on an electrically powered vehicle such as a hybrid vehicle or an electric vehicle will be described. Fig. 1 is a diagram showing the configuration of the power supply system 10.

[0012] In FIG. 1 , the power supply system 10 includes a battery 20 and a battery management unit (BMU) 30, which is a battery monitoring device that monitors the status of the battery 20. The battery 20 is configured as a battery pack in which multiple cells 21 are connected in series. The cells 21 are, for example, rechargeable lithium-ion batteries. More specifically, the cells 21 are LFP batteries (lithium iron phosphate batteries, LiFePO4 batteries) that use, for example, lithium iron phosphate (containing lithium, iron, and phosphorus) as an olivine-based positive electrode material and graphite as a graphite-based negative electrode material. The cells 21 are configured as a single battery cell or multiple battery cells connected in series. Each cell 21 has a similar configuration and the rated capacity of each cell 21 is the same. Either the battery 20 or the cells 21 corresponds to a "storage battery."

[0013] An electric load 41, to which electric power is supplied, is connected to the battery 20. The electric load 41 is, for example, a rotating electric machine that is the main engine of an electric vehicle. The rotating electric machine is capable of power running and regenerative operation, and is driven by power supplied from the battery 20, and also generates regenerative power to charge the battery 20.

[0014] An external charging device 42 can be connected to the battery 20. The charging device 42 is, for example, a charging stand provided in a parking lot or the like, and allows the battery 20 to be charged via a charging cable while the vehicle is parked. The charging device 42 performs so-called plug-in charging of the battery 20.

[0015] A current sensor 23 is provided on an electrical path 22 connecting each of the unit cells 21 in series. In the battery 20, each unit cell 21 is provided with a voltage sensor 24 that detects the terminal voltage (the voltage between the positive and negative terminals). The voltage sensor 24 monitors the terminal voltage of each of the unit cells 21. In addition, at least one unit cell 21 in the battery 20 is provided with a temperature sensor 25 that detects the battery temperature. The detection results of these sensors 23 to 25 are sequentially input to the BMU 30.

[0016] The BMU 30 is primarily composed of a microcontroller (equivalent to a "computer"). The microcontroller includes a processor and a memory (storage unit). The microcontroller provides various computational functions. The functions provided by the microcontroller can be provided by software recorded in a physical memory device and a computer that executes the software, software alone, hardware alone, or a combination of these. For example, when the microcontroller is provided by a hardware electronic circuit, the functions can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcontroller executes programs stored in a non-transitory tangible storage medium that serves as its own storage unit. The programs include, for example, programs for various processes related to battery monitoring. When the programs are executed, a method corresponding to the programs is performed. The storage unit is, for example, a non-volatile memory. The programs stored in the storage unit can be updated, for example, via a network such as the Internet. The BMU 30 corresponds to a "battery control device."

[0017] The BMU 30 performs a deterioration diagnosis of each cell 21. In this embodiment, the BMU 30 diagnoses the deterioration state of each cell 21 based on the impedance and remaining capacity [Ah] of each cell 21. In a cell 21, changes in impedance occur not only due to the progression of deterioration but also due to changes in the remaining capacity. In this case, the remaining capacity of the cell 21 is calculated when the impedance of the cell 21 is measured, and deterioration diagnosis is performed based on the impedance and remaining capacity. This makes it possible to appropriately perform deterioration diagnosis of the cell 21 while distinguishing whether the cause of the change in impedance is deterioration of the cell 21 or a difference in remaining capacity.

[0018] The BMU 30 performs the deterioration diagnosis using, for example, the correlation map shown in Fig. 2. The correlation map in Fig. 2 is correlation data that defines the relationship between the impedance, remaining capacity, and degree of deterioration of the cells 21, and is stored in advance in the memory of the BMU 30. The BMU 30 then obtains the impedance and remaining capacity for each cell 21, and performs the deterioration diagnosis of the cells 21 based on these impedances and remaining capacities.

[0019] When diagnosing the deterioration of a cell 21, it is necessary to grasp the impedance and remaining capacity of the cell 21 in any state. Here, for each cell 21, the remaining capacity is calculated based on the terminal voltage of the cell 21 when the impedance is measured. More specifically, the remaining capacity is calculated based on a certain open circuit voltage (OCV) of the cell 21. However, considering the battery characteristics of the cell 21 (particularly the battery characteristics of an LFP battery), it is conceivable that the accuracy of calculating the remaining capacity based on the terminal voltage will be low when the terminal voltage is detected in any state of the cell 21. This point will be described in detail.

[0020] FIG. 3 is a diagram showing the relationship between remaining capacity and terminal voltage for a cell 21. As shown in FIG. 3, the cell 21 has battery characteristics including a gradual region R1, in which the change in terminal voltage relative to a change in remaining capacity is relatively small, and a steep region R2, in which the change in terminal voltage relative to a change in remaining capacity is relatively large. The gradual region R1 is a low-change region (amount of voltage change per hour) with a small voltage change rate, also referred to as a plateau region. The battery characteristics shown in FIG. 3 include two gradual regions R1 and two steep regions R2. Specifically, the steep region R2 includes a first steep region R21, which is lower than the full charge capacity of the cell 21, and a second steep region R22, which corresponds to the full charge capacity of the cell 21.

[0021] In the slow region R1, the rate of change in voltage relative to the change in remaining capacity is small, and the accuracy of calculating the remaining capacity is low. In other words, in the battery characteristics shown in Figure 3, most of the usage range of the cell 21 is in the slow region R1, and if the terminal voltage of the cell 21 is detected in this slow region R1, the accuracy of calculating the remaining capacity based on the terminal voltage will be low (for example, X1 in the figure).

[0022] In this embodiment, as shown in FIG. 4 , when the impedance of the cell 21 is measured at X1 in the figure, current history information, which is a history of current conduction through the cell 21 since the impedance measurement, is sequentially acquired. After the terminal voltage of the cell 21 transitions from the gradual change region R1 to the steep change region R2, the remaining capacity of the cell 21 corresponding to the terminal voltage in the steep change region R2 is subtracted from the remaining capacity of the cell 21 corresponding to the current history to calculate the remaining capacity at the time of the impedance measurement (the remaining capacity at X1). In other words, the remaining capacity at the time of the impedance measurement (the remaining capacity at X1) is calculated by back-calculating the remaining capacity of the cell 21 corresponding to the terminal voltage in the steep change region R2 and the remaining capacity corresponding to the current history. In this case, the accuracy of the calculation of the remaining capacity based on the terminal voltage is improved in the steep change region R2, and the remaining capacity is calculated with high accuracy. As a result, even if the accuracy of the calculation of the remaining capacity based on the terminal voltage of the cell 21 at that time is low during the impedance measurement, the remaining capacity can be calculated appropriately.

[0023] On the other hand, when performing a deterioration diagnosis based on the impedance and remaining capacity of the battery cell 21, the relationship between impedance and remaining capacity becomes more complex in the steep region R2 than in the gradual region R1, raising concerns about reduced accuracy in the deterioration diagnosis of the battery cell 21. FIG. 5 shows the relationship between remaining capacity and impedance, and in the steep region R2, the relationship between remaining capacity and impedance becomes nonlinear and distorted. In this case, from the perspective of calculation accuracy when calculating remaining capacity from the terminal voltage of the battery cell 21, it is desirable to calculate remaining capacity in the steep region R2 of the battery characteristics. However, from the perspective of performing a deterioration diagnosis based on impedance and remaining capacity, it is undesirable to calculate impedance and remaining capacity in the steep region R2. In consideration of this, in the present embodiment, the impedance and remaining capacity in the gradual region R1 (i.e., the region where the relationship between remaining capacity and impedance is linear) are actively used to perform a deterioration diagnosis of the battery cell 21.

[0024] 1 shows the calculation functions related to deterioration diagnosis in the BMU 30. The BMU 30 has an impedance measurement unit 31, a current history acquisition unit 32, a region determination unit 33, a capacity calculation unit 34, and a deterioration diagnosis unit 35.

[0025] The impedance measurement unit 31 measures the impedance as the internal resistance for each cell 21. The impedance measurement unit 31 may use any method for measuring the impedance, but may, for example, apply an AC current to the cell 21 and calculate the impedance from the voltage response when the AC current is applied. The impedance may be calculated at multiple frequencies.

[0026] The current history acquisition unit 32 acquires, as current history information, a history of current flow through the battery 21 from the time when the impedance measurement unit 31 measures the impedance to the time after the measurement. The current history information is, for example, an integrated value of the current flowing through the battery 21, i.e., an integrated current value ΣI. The current history acquisition unit 32 calculates the integrated current value ΣI by integrating the current detected by the current sensor 23 over a predetermined time period (for example, several msec to several hundred msec), and sequentially stores the integrated current value ΣI in memory. Note that the integrated current value ΣI is integrated on the positive side when the battery 20 is being charged, and the integrated current value ΣI is integrated on the negative side when the battery 20 is being discharged.

[0027] The region determination unit 33 determines that the terminal voltage of each cell 21 has transitioned from the gradual region R1 to the steep region R2 when the cell 21 is energized after measuring the impedance. Specifically, the region determination unit 33 determines that the terminal voltage of each cell 21 has transitioned from the gradual region R1 to the steep region R2 when a voltage change rate, which is the amount of change per unit time in the terminal voltage of each cell 21, is greater than a predetermined value. The voltage change rate is the rate of change over time in the closed circuit voltage (CCV) of the cell 21. More specifically, a first voltage threshold A1 and a second voltage threshold A2 greater than the first voltage threshold A1 are predefined as thresholds for the voltage change rate. When the voltage change rate changes from less than A1 to equal to or greater than A2, the region determination unit 33 determines that the terminal voltage of each cell 21 has transitioned from the gradual region R1 to the steep region R2.

[0028] In this embodiment, the region determination unit 33 determines that the battery has transitioned to the second steep region R22 (i.e., the fully charged region) of the first steep region R21 and the second steep region R22 shown in Fig. 3. The first steep region R21 and the second steep region R22 can be identified by the difference in voltage level.

[0029] When the region determination unit 33 determines that the terminal voltage of the battery 21 has transitioned to the steep region R2, the capacity calculation unit 34 calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit 31 based on the remaining capacity of the battery 21 corresponding to the terminal voltage in the steep region R2 and the current accumulation value ΣI (current flow history information) acquired by the current flow history acquisition unit 32.

[0030] 2 , based on the impedance of the battery 21 measured by the impedance measuring unit 31 and the remaining capacity calculated by the capacity calculating unit 34. The deterioration diagnosing unit 35 can also determine whether or not the battery 21 has deteriorated based on the battery temperature detected by the temperature sensor 25 in addition to the impedance and remaining capacity of the battery 21.

[0031] 6 is a flowchart showing the procedure for diagnosing deterioration of the cells 21, and this process is repeatedly executed at a predetermined interval by the BMU 30. This process may be executed for each cell 21 of the battery 20.

[0032] 6 , in step S101, it is determined whether or not a diagnosis execution condition for executing a deterioration diagnosis of the cell 21 is met. In this embodiment, a deterioration diagnosis of the battery 20 is performed while the battery is being charged by the charging device 42, and the diagnosis execution condition preferably includes that the battery is being charged by the charging device 42. The diagnosis execution condition preferably also includes that the terminal voltage of the cell 21 is in the slow region R1 as a prerequisite for impedance measurement. Since the diagnosis execution condition includes that the terminal voltage is in the slow region R1, deterioration diagnosis of the cell 21 is performed on the condition that the impedance is measured in the slow region R1.

[0033] Whether the terminal voltage of the cell 21 is in the slow region R1 may be determined based on whether the voltage change rate, which indicates the amount of change per unit time in the terminal voltage of the cell 21, is smaller than a predetermined value. For example, when current is supplied to the battery 20 by charging or discharging, whether the voltage is in the slow region R1 may be determined based on the voltage change rate at that time. Other conditions for performing the diagnosis may include whether a predetermined time, such as several hours, has elapsed since the last time current was stopped from the battery, i.e., since the last time the vehicle was stopped.

[0034] If the result of step S101 is affirmative, the process proceeds to step S102, where the impedance of the cells 21 is measured. If the battery 20 is externally charged by the charging device 42, the impedance of the cells 21 is measured when charging by the charging device 42 starts (specifically, immediately before or at the start of charging).

[0035] Then, in step S103, the current flowing through the battery 21 is acquired, and in the following step S104, the current integrated current value ΣI is calculated by adding the newly acquired integrated current value ΣI to the previous integrated current value ΣI. When the battery is being charged by the charging device 42, the charging current is integrated at a predetermined time interval.

[0036] Then, in step S105, it is determined whether the terminal voltage of the cell 21 has transitioned from the gradual region R1 to the steep region R2 after the start of current application to the battery 20. At this time, it is preferable to determine that the terminal voltage of the cell 21 has transitioned from the gradual region R1 to the steep region R2 if the voltage change rate of the cell 21 is greater than a predetermined value. If the terminal voltage has not transitioned from the gradual region R1 to the steep region R2, the process returns to step S103. If the terminal voltage has transitioned from the gradual region R1 to the steep region R2, the process proceeds to the subsequent step S106.

[0037] In addition, when the battery 20 is externally charged by the charging device 42, the configuration may be such that when the charging device 42 fully charges the single cell 21, that is, when charging by the charging device 42 is completed, it is determined that the terminal voltage of the single cell 21 has transitioned to the steep region R2.

[0038] In step S106, it is determined whether the current integrated current value ΣI is smaller than a predetermined threshold value Th. If the current integrated current value ΣI is excessively large, there is a concern that an error in the current integrated value ΣI, i.e., an error in the back-calculation of the remaining capacity, may be large. Therefore, if the current integrated value ΣI is less than the threshold value Th, the process proceeds to the subsequent step S107. If the current integrated value ΣI is equal to or greater than the threshold value Th, the process ends.

[0039] In step S106, it may be determined whether the accumulated time over which the current accumulated value ΣI has been accumulated is shorter than a predetermined time. In this case, if the accumulated time is shorter than the predetermined time, the process proceeds to the subsequent step S107. If the accumulated time is equal to or greater than the predetermined time, the process ends. The predetermined time may be, for example, several hours, or approximately 10 to 20 hours.

[0040] In step S107, the remaining capacity of the cell 21 at the current time is calculated based on the terminal voltage of the cell 21 at the current time (i.e., the terminal voltage in the steep region R2). At this time, the remaining capacity is preferably calculated based on the OCV of the cell 21. In the following step S108, the remaining capacity at the time of impedance measurement is back-calculated based on the remaining capacity calculated in step S107 and the current integrated value ΣI calculated in step S104.

[0041] When the battery 20 is externally charged by the charging device 42, the remaining capacity at the time of impedance measurement may be back-calculated based on the full charge capacity of the cells 21 and the current integrated value ΣI up to full charge. The full charge capacity of the cells 21 is the remaining capacity corresponding to the terminal voltage of the cells 21 in a fully charged state, and may be predetermined as a target remaining capacity when charging by the charging device 42.

[0042] In step S109, using the correlation map shown in FIG. 2, for example, it is determined whether or not the battery 21 has deteriorated based on the impedance of the battery 21 measured in step S102 and the remaining capacity calculated in step S108.

[0043] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0044] The current integration value ΣI is acquired as current conduction history information of the cell 21 from the time of impedance measurement to the time after the measurement. During current conduction of the cell 21 after the impedance measurement, it is determined that the terminal voltage of the cell 21 has transitioned from the gradual region R1 to the steep region R2. If it is determined that the terminal voltage of the cell 21 has transitioned to the steep region R2, the remaining capacity at the time of the impedance measurement is calculated based on the remaining capacity of the cell 21 corresponding to the terminal voltage in the steep region R2 and the current integration value ΣI (current conduction history information) after the impedance measurement. In this case, the accuracy of calculating the remaining capacity based on the terminal voltage of the cell 21 is improved in the steep region R2 of the battery characteristics, allowing for highly accurate calculation of the remaining capacity. Furthermore, the current integration value ΣI (current conduction history information) after the impedance measurement allows for the change in the remaining capacity since the impedance measurement to be determined. Therefore, the remaining capacity at the time of the impedance measurement can be calculated based on the remaining capacity calculated in the steep region R2 and the current integration value ΣI after the impedance measurement. As a result, the remaining capacity of the cell 21 at the time of impedance measurement can be calculated appropriately.

[0045] Furthermore, by being able to properly calculate the remaining capacity of the cell 21 when the impedance is measured, it is possible to improve the quality of the deterioration diagnosis of the cell 21 that is performed based on the impedance and the remaining capacity.

[0046] If, after measuring the impedance, it is determined that the terminal voltage of the battery 21 has transitioned to the steep region R2, the remaining capacity at the time of impedance measurement is calculated based on the remaining capacity of the battery 21 corresponding to the terminal voltage in the steep region R2 and the accumulated current value ΣI (current-flow history information), provided that the accumulated current value ΣI is smaller than a predetermined value or the integration time for integrating the accumulated current value ΣI is shorter than a predetermined time. In this case, if the accumulated current value ΣI is larger than the predetermined value or the integration time for the accumulated current value ΣI is longer than the predetermined time, there is a concern that the error in the accumulated current value ΣI as the current-flow history information, i.e., the error in the back-calculation of the remaining capacity, may be large. In this regard, since the back-calculation of the remaining capacity is performed based on the accumulated current value ΣI or the integration time, erroneous calculation of the remaining capacity is suppressed.

[0047] When each cell 21 is charged to a fully charged state by the charging device 42, the impedance of each cell 21 is measured at the start of charging, and the remaining capacity at the time of impedance measurement is calculated based on the full charge capacity of the cell 21 when the cell 21 is fully charged and the integrated current value ΣI up to full charge. In this case, when the cell 21 is charged by the charging device 42 (during plug-in charging), the impedance and remaining capacity of the cell 21 can be properly determined, and thus deterioration of the cell 21 can be properly diagnosed.

[0048] In the steep region R2 of the cell 21, the relationship between impedance and remaining capacity is more complex than in the gradual region R1, which may reduce the accuracy of the deterioration diagnosis of the cell 21. In view of this, the deterioration diagnosis of the cell 21 is performed on the condition that the impedance is measured in the gradual region R1 of the cell 21. In this case, the accuracy of the deterioration diagnosis can be improved by acquiring the impedance and remaining capacity in the gradual region R1.

[0049] The following describes another embodiment, focusing on the differences from the first embodiment.

[0050] Second Embodiment In this embodiment, a process of updating the correlation map used for diagnosing deterioration of the cell 21 will be described. In this embodiment, the correlation map for diagnosing deterioration is updated based on the impedance and remaining capacity on the condition that the impedance of the cell 21 is measured in the slow region R1. In this embodiment, the BMU 30 constitutes the correlation data update unit.

[0051] FIG. 7 is a flowchart showing the procedure for updating the correlation map.

[0052] 7 , in step S201, it is determined whether an update condition for executing the update of the correlation map is satisfied. The update condition includes the terminal voltage of the cell 21 being in the slow region R1. Whether the terminal voltage of the cell 21 is in the slow region R1 may be determined based on whether the voltage change rate, which indicates the amount of change per unit time in the terminal voltage of the cell 21, is smaller than a predetermined value. For example, it may be determined whether the battery 20 is in the slow region R1 based on the voltage change rate at that time when the battery 20 is energized by charging or discharging.

[0053] If step S201 is positive, in steps S202 to S208, the impedance of the battery cell 21 is measured, and the remaining capacity at the time of the impedance measurement is calculated based on the current history (integrated current value ΣI) of the battery cell 21 after the impedance measurement. The processing of steps S202 to S208 is similar to the processing of steps S102 to S108 in Fig. 6, and this processing will be briefly described here.

[0054] In step S202, the impedance of the battery cell 21 is measured. Then, in step S203, the current flowing through the battery cell 21 is acquired. In step S204, the current current is calculated by adding the acquired current to the previous current cumulative value ΣI. Then, in step S205, it is determined whether the terminal voltage of the battery cell 21 has transitioned from the gradual region R1 to the steep region R2 after the start of current conduction in the battery 20. If step S205 is affirmative, the process proceeds to step S206, where it is determined whether the current current cumulative value ΣI is smaller than a predetermined threshold value Th. In step S206, it may also be determined whether the cumulative time over which the current cumulative value ΣI has been accumulated is shorter than a predetermined time.

[0055] If the result of step S206 is affirmative, the process proceeds to step S207, where the remaining capacity of the battery 21 at the current time is calculated based on the terminal voltage of the battery 21 at the current time (i.e., the terminal voltage in the steep region R2). In the following step S208, the remaining capacity at the time of impedance measurement is back-calculated based on the remaining capacity calculated in step S207 and the current integrated value ΣI calculated in step S204.

[0056] In step S209, the degree of deterioration of the battery 21 is calculated. The degree of deterioration of the battery 21 is calculated based on the remaining capacity (full charge capacity) calculated when the battery 21 is fully charged in step S207 and a predetermined reference full charge capacity of the battery 21. In this embodiment, the state of health (SOH) is calculated as the degree of deterioration of the battery 21. Specifically, assuming that the full charge capacity calculated in the fully charged state in step S207 is Cf [Ah] and the reference full charge capacity is Cf0 [Ah], the SOH [%] is calculated using the following formula 1: SOH = Cf / Cf0 (Formula 1) Then, in step S210, correlation data is updated (corresponding to a correlation data update unit) in the correlation map shown in FIG. 2, for example, based on the impedance of the battery 21 measured in step S202, the remaining capacity calculated in step S208, and the degree of deterioration calculated in step S209. At this time, data is written to an empty area or existing data is rewritten in the correlation map. In the correlation map, only the minimum necessary data is prepared at the system manufacturing stage, and data is written into free areas under actual vehicle usage conditions.

[0057] In the present embodiment, provided that the impedance of the battery cell 21 is measured in the gradual change region R1, the degradation diagnosis map (correlation data) is updated based on the impedance and the remaining capacity calculated by back-calculation at the time of the impedance measurement. In this case, the impedance and remaining capacity of the battery cell 21 in the gradual change region R1 are used to update the correlation data between the impedance and the remaining capacity, rather than the impedance and remaining capacity in the steep change region R2. In the gradual change region R1, the relationship between the impedance and the remaining capacity varies less than in the steep change region R2, so the correlation data is updated appropriately. This improves the accuracy of the degradation diagnosis.

[0058] The above configuration acquires actual measurement data of impedance and remaining capacity after the vehicle has started to be used (i.e., after the power supply system 10 has started to be used), and updates the map data (correlation data) of impedance and remaining capacity using the actual measurement data, thereby simplifying the map creation process during manufacturing.

[0059] Third Embodiment In this embodiment, a process will be described for when charging is terminated before full charge when charging a battery using a charging device 42. Here, it is assumed that a cell 21 is charged from X11 to X12 in Fig. 8, and the remaining capacity at X1 is calculated backward from the estimated remaining capacity in the first steep region R21.

[0060] 9 is a flowchart showing the procedure for diagnosing deterioration of the cells 21, and this process is repeatedly executed at a predetermined interval by the BMU 30. This process may be executed for each cell 21 of the battery 20.

[0061] 9 , in step S301, it is determined whether or not a diagnosis execution condition is met for executing a deterioration diagnosis of the battery cells 21. In this embodiment, the deterioration diagnosis of the battery 20 is performed when the charging device 42 starts charging the battery, and the diagnosis execution condition may include the start of charging the battery by the charging device 42. Other diagnosis execution conditions may include the terminal voltage of the battery 21 being in the slow region R1, or a predetermined time, such as several hours, having passed since the last time power was stopped from the battery, i.e., since the last time the vehicle was stopped.

[0062] If step S301 is positive, the process proceeds to step S302, where the impedance of the battery cell 21 is measured. In step S303, the current flowing through the battery cell 21 is acquired, and in the subsequent step S304, the current value of the current integrated value ΣI is calculated by adding the current integrated value ΣI acquired this time to the current integrated value ΣI up to the previous time. Note that the processes of steps S302 to S304 are similar to the processes of steps S102 to S104 in FIG. 6.

[0063] Then, in step S305, after the start of energization of the battery 20, it is determined whether the terminal voltage of the cell 21 has transitioned from the gradual region R1 to the steep region R2. At this time, it is determined that the terminal voltage has transitioned to the first steep region R21 or the second steep region R22 based on whether the voltage change rate of the cell 21 is greater than a predetermined value. If the terminal voltage of the cell 21 has transitioned to either the first steep region R21 or the second steep region R22, a positive result is obtained in step S305, and the process proceeds to step S306. In step S306, the current remaining capacity of the cell 21 is estimated based on the current terminal voltage of the cell 21 (i.e., the terminal voltage in either the steep region R21 or R22). This remaining capacity is remaining capacity estimation data and is stored in memory. Here, the remaining capacity may be estimated based on the CCV of the cell 21.

[0064] Then, in step S307, it is determined whether the cell 21 is fully charged, i.e., whether the cell has transitioned to the second steep region R22. The distinction between the first steep region R21 and the second steep region R22 may be made, for example, based on the terminal voltage of the cell 21. That is, the terminal voltage of the cell 21 differs between the first steep region R21 and the second steep region R22. In this case, if the terminal voltage of the cell 21 is less than a predetermined value, the cell is in the first steep region R21; if the terminal voltage of the cell 21 is equal to or greater than the predetermined value, the cell is in the second steep region R22. If the cell 21 is not fully charged, the process returns to step S303; if the cell is fully charged, the process proceeds to the subsequent step S308.

[0065] In step S308, the remaining capacity at the time of impedance measurement is back-calculated based on the remaining capacity corresponding to the terminal voltage of the cell 21 at the current time (i.e., the terminal voltage in a fully charged state) and the current integrated value ΣI calculated in step S304. Note that in step S308, similar to steps S106 to S108 in Fig. 6, the remaining capacity at the time of impedance measurement may be back-calculated using the current integrated value ΣI on the condition that the current integrated value ΣI is smaller than the threshold value Th or on the condition that the integration time for integrating the current integrated value ΣI is shorter than a predetermined time.

[0066] In step S309, using the correlation map shown in FIG. 2, for example, it is determined whether or not the battery 21 has deteriorated based on the impedance of the battery 21 measured in step S302 and the remaining capacity calculated in step S308.

[0067] If it is determined in step S305 that the battery is still in the gradual region R1 and has not yet transitioned to the steep region R2, the process proceeds to step S310. In step S310, it is determined whether battery charging has been completed. That is, it is determined whether battery charging was completed before the cells 21 (battery 20) were fully charged, i.e., whether charging of the cells 21 was completed at a capacity lower than the full charge capacity. If battery charging is continuing, the process returns to step S303; if battery charging has been completed, the process proceeds to step S311.

[0068] In step S311, it is determined whether the remaining capacity estimation data calculated in step S306 is stored in memory. If the remaining capacity estimation data is stored, the process proceeds to step S312, where the remaining capacity estimation data stored in memory is read. If the remaining capacity estimation data is not stored, the process ends.

[0069] Thereafter, in step S308, the remaining capacity at the time of impedance measurement is calculated backward based on the remaining capacity estimation data read out in step S312 and the current integrated value ΣI calculated in step S304. In step S309, whether or not the single battery 21 has deteriorated is determined based on the impedance of the single battery 21 measured in step S302 and the remaining capacity calculated in step S308.

[0070] In step S308 of FIG. 9, it is preferable that the remaining capacity be back-calculated under the condition that the current integrated value ΣI used for back-calculating the remaining capacity during impedance measurement is less than a predetermined threshold value, or that the integration time for integrating the current integrated value ΣI is shorter than a predetermined time (similar to steps S106 to S108 of FIG. 6).

[0071] During charging of the battery 21, it is possible that the battery 21 may not be fully charged. In this case, the terminal voltage of the battery 21 may reach the first steep region R21, which indicates a capacity lower than the full charge capacity, but may not reach the second steep region R22, which indicates the full charge state. In consideration of this, if the voltage change rate of the battery 21 becomes greater than a predetermined value after the charging device 42 starts charging, remaining capacity estimation data based on the current integrated value ΣI (current application history information) and terminal voltage at that time is acquired. Then, if the charging of the battery 21 is terminated at a capacity lower than the full charge capacity, and remaining capacity estimation data has been acquired before, the remaining capacity at the time of impedance measurement is calculated based on the remaining capacity estimation data. This allows the impedance and remaining capacity of the battery 21 to be properly determined as a set even when the charging device 42 does not fully charge the battery 21, thereby enabling proper deterioration diagnosis of the battery 21.

[0072] Fourth Embodiment In this embodiment, when the battery is charged by the charging device 42, a first charge is performed in which the cells 21 are charged to a predetermined designated voltage (charging voltage Vc) that is lower than the terminal voltage corresponding to the steep region R2 of the cells 21, and a second charge is performed in which the cells 21 are charged to the steep region R2 following the first charge. In the second charge after the first charge is completed, the impedance of the cells 21 is measured and the remaining capacity after completion of charging is calculated based on the remaining capacity and current history. The first charge and the second charge may be performed consecutively without a temporary stop between them, or may be performed consecutively with a temporary stop between them.

[0073] An overview of the processing in this embodiment will be described with reference to FIG. 10 . In FIG. 10 , the first charging step involves charging the cell 21 from X21 to X22, and the second charging step involves charging the cell 21 from X22 to X23. In the first charging step, charging is performed until the terminal voltage of the cell 21 reaches the charging voltage Vc. In the second charging step, charging is performed until the cell 21 is fully charged. In this case, in the second charging step, the impedance of the cell 21 at X22 is measured at the start of charging, and an integrated current value ΣI is calculated as current history information after the start of charging. Then, when charging up to X23 (full charge) is completed and it is determined that the terminal voltage of the cell 21 has transitioned to the steep region R2, the remaining capacity at the time of impedance measurement (i.e., the remaining capacity at X22) is back-calculated based on the remaining capacity corresponding to the terminal voltage of the cell 21 and the integrated current value ΣI.

[0074] 10, X22 is preferably set on the full charge side of the median of the remaining capacity in the high-capacity slow region R1 of the two-stage slow region R1. This shortens the integration period of the current flow, i.e., the time over which errors in the current sensor 23 accumulate, during the second charge, thereby reducing the error in the integrated current value ΣI.

[0075] 11 is a flowchart showing the procedure for diagnosing deterioration of the cells 21, and this process is repeatedly executed at a predetermined interval by the BMU 30. This process may be executed for each cell 21 of the battery 20.

[0076] 11 , in step S401, it is determined whether or not a diagnosis execution condition is met for executing a deterioration diagnosis of the cell 21. In this embodiment, the deterioration diagnosis of the battery 20 is performed while the battery is being charged by the charging device 42, and the diagnosis execution condition preferably includes the fact that the battery is being charged by the charging device 42. In addition, the diagnosis execution condition preferably includes the fact that the terminal voltage of the cell 21 is in the slow region R1 as a prerequisite for impedance measurement.

[0077] If step S401 is positive, the process proceeds to step S402, where the charging device 42 performs a first charge. In the first charge, charging is performed until the terminal voltage of the cell 21 reaches the charging voltage Vc. In step S403, it is determined whether the first charge has been completed. At this time, if the terminal voltage of the cell 21 has reached the charging voltage Vc, it is determined that the first charge has been completed. If the first charge has not been completed, the process returns to step S402, and if the first charge has been completed, the process proceeds to step S404. Note that the first charge may be a constant voltage charge at the charging voltage Vc, and the condition for completing the first charge may be when the charging current falls below a predetermined value.

[0078] In step S404, the impedance of the cell 21 is measured. In step S405, the charging device 42 is caused to perform a second charge. In the second charge, charging is performed until the cell 21 is fully charged, that is, until the terminal voltage of the cell 21 reaches a voltage corresponding to full charge. In step S406, the current flowing through the cell 21 is obtained, and in the subsequent step S407, the integrated current value ΣI in the second charge is calculated. At this time, in step S404, the impedance of the cell 21 at the start of the second charge is measured, and in step S407, the integrated current value ΣI is calculated as current flow history information from the start of the second charge.

[0079] Thereafter, in step S408, it is determined whether the second charging has been completed. At this time, if the cells 21 are fully charged, it is determined that the second charging has been completed. If the second charging has not been completed, the process returns to step S405, and if the second charging has been completed, the process proceeds to step S409.

[0080] In step S409, the remaining capacity of the cell 21 at the current time is calculated based on the terminal voltage of the cell 21 at the current time (i.e., the terminal voltage in the steep region R2). At this time, the remaining capacity may be calculated based on the OCV of the cell 21. In the following step S410, the remaining capacity at the start of the second charge, i.e., at the time of impedance measurement, is calculated back based on the remaining capacity calculated in step S409 and the current integrated value ΣI calculated in step S407.

[0081] Then, in step S411, a capacity difference ΔQ is calculated, which is the difference between the remaining capacity calculated in step S410, i.e., the actual remaining capacity at the start of the second charging (the end of the first charging), and a specified capacity that is predetermined as the remaining capacity at the end of the first charging, and it is determined whether the absolute value of the capacity difference ΔQ is smaller than a predetermined threshold value Th2 (corresponding to the capacity determination unit). If |ΔQ|<Th2, the process proceeds to step S412, and if |ΔQ|≧Th2, the process proceeds to step S413.

[0082] In step S412, for example, the correlation map shown in FIG. 2 is used to determine whether the cells 21 have deteriorated based on the impedance of the cells 21 measured in step S404 and the remaining capacity calculated in step S410.

[0083] In step S413, the charging voltage Vc of the first charge is increased or decreased (corresponding to a voltage adjusting unit). At this time, if |ΔQ| ≧ Th2 and the actual capacity is smaller than the designated capacity, the charging voltage Vc should be increased. Also, if |ΔQ| ≧ Th2 and the actual capacity is larger than the designated capacity, the charging voltage Vc should be decreased.

[0084] In the present embodiment, the battery is charged by the charging device 42 in two stages: a first charge, which charges the battery to a charging voltage Vc (specified voltage) lower than the full charge region (voltage steepness region), and a second charge, which follows the first charge and charges the battery to the full charge capacity. During the second charge, the impedance of the cells 21 is measured, and the remaining capacity at the time of the impedance measurement is calculated based on the current history information during the second charge and the remaining capacity corresponding to the terminal voltage at full charge. In this case, the second charge, which follows the first charge, has a relatively short charging period, which reduces the accumulation of errors in the current integration value ΣI, which is the current history information. This improves the accuracy of the remaining capacity calculated by back-calculating the current integration value.

[0085] The charging device 42 determines whether the capacity difference ΔQ between the actual remaining capacity (actual capacity) of the cell 21 at the end of the first charge (the first charge) and the specified capacity is smaller than a predetermined value. If it is determined that the capacity difference ΔQ is smaller than the predetermined value, the charging device 42 measures the impedance of the cell 21 in the subsequent second charge, and calculates the remaining capacity at the time of impedance measurement based on the current history information in the second charge and the remaining capacity corresponding to the terminal voltage at full charge. In this case, it is possible to accurately grasp the capacity change of the cell 21 during the second charge, and therefore to accurately calculate the remaining capacity at the time of impedance measurement.

[0086] If it is determined that the capacity difference ΔQ between the actual remaining capacity estimated at the end of the first charge and the specified capacity is greater than a predetermined value, the charging voltage Vc in the first charge is adjusted up or down, thereby enabling the first charge to be performed appropriately the next time the cells 21 are charged.

[0087] (Other Embodiments) The above embodiment may be modified as follows, for example.

[0088] The relationship between impedance and remaining capacity of the battery 21 varies depending on the battery temperature. Specifically, as shown in Fig. 12, when comparing room temperature (25°C) with low temperature (e.g., 0°C), the slope of the change in impedance with respect to remaining capacity is greater at low temperature. Therefore, when diagnosing deterioration of the battery 21 based on the impedance and remaining capacity, it is thought that the diagnosis accuracy will be higher at low temperatures.

[0089] Therefore, when diagnosing deterioration of the cells 21, the diagnosis execution conditions may include the battery temperature being in a predetermined low temperature state. Specifically, a predetermined temperature Tp (e.g., 10°C) that is lower than room temperature may be set, and the diagnosis conditions may include the battery temperature being lower than the predetermined temperature Tp. For example, in step S101 of Fig. 6, if the battery temperature is lower than the predetermined temperature Tp, it may be determined that the diagnosis conditions are met.

[0090] In the above embodiment, after the impedance is measured, the BMU 30 acquires the current integrated value ΣI of the battery 21 as the current supply history information. However, this configuration may be changed. For example, after the impedance is measured, the BMU 30 acquires the power integrated value of the battery 21 as the current supply history information.

[0091] The BMU 30 may calculate the SOC (State Of Charge) as the remaining capacity of the battery cell 21. The SOC [%] may be calculated from the remaining capacity Cr [Ah] of the battery cell 21 and the fully charged capacity Cf [Ah] of the battery cell 21 using the following formula 2: SOC=Cr / Cf (Formula 2) The BMU 30 may also calculate the remaining energy as the remaining capacity of the battery cell 21.

[0092] During discharge from the battery 20 to the electrical load 41, the impedance of the cell 21 may be measured and the remaining capacity of the cell 21 at the time of impedance measurement may be calculated. As shown in FIG. 13 , for example, when the impedance of the cell 21 is measured at X31 in the figure, current history information of the cell 21 (integrated current value ΣI of the discharge current) may be sequentially acquired during battery discharge from the time of the impedance measurement. After the terminal voltage of the cell 21 transitions from the gentle region R1 to the first steep region R21, the remaining capacity of the cell 21 at the time of impedance measurement (the remaining capacity at X31) may be calculated by subtracting the remaining capacity corresponding to the current history from the remaining capacity of the cell 21 corresponding to the terminal voltage in the first steep region R21. Note that the impedance measurement and the calculation (reverse calculation) of the remaining capacity may be performed at any timing during battery discharge.

[0093] In the above embodiment, the remaining capacity of each cell 21 in the battery 20 is calculated, and degradation diagnosis is performed for each cell 21 based on the impedance and remaining capacity. However, this configuration may be changed. For example, the remaining capacity may be calculated and degradation diagnosis may be performed for each battery group including a plurality of cells 21. Alternatively, the remaining capacity may be calculated and degradation diagnosis may be performed for the battery 20.

[0094] In the above embodiment, the impedance measurement unit 31 is provided as one of the functions of the BMU 30. However, this may be modified so that the impedance measurement unit 31 is provided as a measurement device separate from the BMU 30. In this case, the BMU 30 and the impedance measurement device constitute a battery control device.

[0095] The power supply system 10 is not limited to being mounted on a vehicle, but may be mounted on other moving objects such as aircraft, ships, etc. Furthermore, the power supply system 10 is not limited to being mounted on a moving object, but may be a stationary system.

[0096] The control device and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control device and method described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the control device and method described herein may be implemented by one or more special-purpose computers configured with a combination of a processor and memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

[0097] The technical ideas extracted from the above-described embodiments will be described below. [Configuration 1] A battery control device (30) applied to a power supply system (10) having a storage battery (20, 21), wherein the storage battery has, in battery characteristics indicating the relationship between remaining capacity and terminal voltage, a gradual region where the change in terminal voltage relative to a change in remaining capacity is relatively small, and a steep region where the change in terminal voltage relative to a change in remaining capacity is relatively large, the battery control device comprising: an impedance measurement unit that measures the impedance of the storage battery; a current history acquisition unit that acquires a history of current flow through the storage battery from the time of measurement of the impedance to after the measurement as current flow history information; a region determination unit that determines, when current is flowing through the storage battery after the impedance measurement, that the terminal voltage of the storage battery has transitioned from the gradual region to the steep region; and a capacity calculation unit that, when it is determined by the region determination unit that the terminal voltage of the storage battery has transitioned to the steep region, calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region and the current flow history information. [Configuration 2] The battery control device according to Configuration 1, wherein the current history acquisition unit acquires, as the current history information, an integrated current value which is an integrated value of the current flowing through the storage battery after the impedance is measured, and when the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region, the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the current history information and the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region, on the condition that the integrated current value is smaller than a predetermined value or the integration time for which the integrated current value is integrated is shorter than a predetermined time.[Configuration 3] The battery control device according to Configuration 1 or 2, wherein the storage battery can be charged by a charging device (42), the impedance measurement unit measures the impedance of the storage battery when the charging device starts charging the storage battery, the current history acquisition unit acquires the current history information after the charging device starts charging, the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region when the storage battery is fully charged by the charging device, and the capacity calculation unit calculates the remaining capacity at the time of the impedance measurement based on the full charge capacity of the storage battery when the storage battery is fully charged and the current history information up to the full charge. [Configuration 4] The battery control device according to any of Configurations 1 to 3, further comprising a degradation diagnosis unit that performs degradation diagnosis of the storage battery based on the impedance measured by the impedance measurement unit and the remaining capacity calculated by the capacity calculation unit. [Configuration 5] The battery control device according to Configuration 4, wherein the degradation diagnosis unit performs degradation diagnosis of the storage battery on condition that the impedance has been measured by the impedance measurement unit in the slow region of the storage battery. [Configuration 6] The battery control device according to Configuration 5, wherein the degradation diagnosis unit performs degradation diagnosis of the storage battery based on correlation data that defines a correlation between the impedance and remaining capacity of the storage battery, and includes a correlation data update unit that updates the correlation data based on the impedance measured by the impedance measurement unit and the remaining capacity calculated by the capacity calculation unit at the time of impedance measurement on condition that the impedance has been measured by the impedance measurement unit in the slow region of the storage battery.[Configuration 7] The storage battery can be charged by a charging device (42), and the impedance measurement unit measures the impedance of the storage battery when charging of the storage battery by the charging device starts, and the battery characteristics of the storage battery have, as the steep slope region, a first steep slope region that is lower than the full charge capacity of the storage battery and a second steep slope region that corresponds to the full charge capacity of the storage battery, and the region determination unit determines that the terminal voltage has transitioned to the first steep slope region or the second steep slope region based on a voltage change rate that indicates a change in terminal voltage per unit time of the storage battery becoming larger than a predetermined value after charging by the charging device starts, and the current flow history acquisition unit, when the voltage change rate becomes larger than the predetermined value, acquires the current flow history information at that time and remaining capacity estimation data based on the terminal voltage, The battery control device according to any one of configurations 1 to 6, wherein, when charging of the storage battery is terminated at a capacity lower than a full charge capacity, if the remaining capacity estimation data has been acquired by the current history acquisition unit before the present time, the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity estimation data. [Configuration 8] A battery control device according to any one of Configurations 1 to 7, wherein the storage battery can be charged by a charging device (42), and when the storage battery is charged by the charging device, a first charge is performed in which the storage battery is charged to a predetermined designated voltage that is lower than the terminal voltage corresponding to the steep region, and a second charge is performed in which the storage battery is charged to the steep region following the first charge, and the impedance measurement unit measures the impedance of the storage battery at the start of the second charge, the current flow history acquisition unit acquires the current flow history information from the start of the second charge, the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region after the start of the second charge, and the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the current flow history information and the remaining capacity of the storage battery corresponding to the terminal voltage at the transition to the steep region after the start of the second charge.[Configuration 9] The storage battery can be charged by a charging device (42), and when the storage battery is charged by the charging device, a first charge is performed to charge the storage battery to a predetermined designated voltage that is lower than the terminal voltage corresponding to the steep region, and a second charge is performed to charge the storage battery to the steep region following the first charge; the storage battery includes: an actual capacity estimation unit that estimates an actual capacity that is an actual remaining capacity of the storage battery at the end of the first charge; and a capacity determination unit that determines whether a capacity difference between the actual capacity estimated by the actual capacity estimation unit and a designated capacity that is predetermined as the remaining capacity at the end of the first charge is smaller than a predetermined value; the impedance measurement unit measures the impedance of the storage battery at the start of the second charge; the current flow history acquisition unit acquires the current flow history information from the start of the second charge; and the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region after the start of the second charge. The battery control device according to any one of configurations 1 to 8, wherein the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity of the storage battery corresponding to the terminal voltage at the time of transition to the steep region after the start of the second charging and the current flow history information, on condition that the capacity determination unit determines that the capacity difference is smaller than a predetermined value. [Configuration 10] The battery control device according to configuration 9, further comprising a voltage adjustment unit that adjusts the designated voltage when the capacity determination unit determines that the capacity difference is larger than a predetermined value.

[0098] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A battery control device (30) applied to a power supply system (10) having a storage battery (20, 21), wherein the storage battery has, in battery characteristics indicating the relationship between remaining capacity and terminal voltage, a gradual region where the change in terminal voltage relative to a change in remaining capacity is relatively small, and a steep region where the change in terminal voltage relative to a change in remaining capacity is relatively large, the battery control device comprising: an impedance measurement unit that measures the impedance of the storage battery; a current history acquisition unit that acquires a history of current flow through the storage battery from the time of measurement of the impedance to after the measurement as current flow history information; a region determination unit that determines, when current is flowing through the storage battery after measuring the impedance, that the terminal voltage of the storage battery has transitioned from the gradual region to the steep region; and a capacity calculation unit that, when it is determined by the region determination unit that the terminal voltage of the storage battery has transitioned to the steep region, calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region and the current flow history information.

2. The battery control device of claim 1, wherein the current history acquisition unit acquires, as the current history information, an accumulated current value, which is an accumulated value of the current flowing through the storage battery after the impedance is measured; and when the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region, the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region and the current history information, provided that the accumulated current value is smaller than a predetermined value or the accumulated time during which the accumulated current value is accumulated is shorter than a predetermined time.

3. A battery control device as described in claim 1 or 2, wherein the storage battery can be charged by a charging device (42), the impedance measurement unit measures the impedance of the storage battery when the charging device starts charging the storage battery, the current history acquisition unit acquires the current history information after the charging device starts charging, the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region when the storage battery is fully charged by the charging device, and the capacity calculation unit calculates the remaining capacity at the time of measuring the impedance based on the full charge capacity of the storage battery when the storage battery is fully charged and the current history information up to the full charge.

4. A battery control device according to claim 1 or 2, further comprising a degradation diagnosis unit that performs degradation diagnosis of the storage battery based on the impedance measured by the impedance measurement unit and the remaining capacity calculated by the capacity calculation unit.

5. A battery control device according to claim 4, wherein the deterioration diagnosis unit executes deterioration diagnosis of the storage battery on the condition that the impedance measurement unit measures impedance in the slow region of the storage battery.

6. A battery control device as described in claim 5, wherein the deterioration diagnosis unit performs deterioration diagnosis of the storage battery based on correlation data that defines the correlation between the impedance and remaining capacity of the storage battery, and further comprises a correlation data update unit that updates the correlation data based on the impedance measured by the impedance measurement unit and the remaining capacity calculated by the capacity calculation unit at the time of impedance measurement, on the condition that the impedance is measured by the impedance measurement unit in the slow region of the storage battery.

7. The storage battery can be charged by a charging device (42), and the impedance measurement unit measures the impedance of the storage battery when the charging device starts charging the storage battery, and the battery characteristics of the storage battery have, as the steep slope region, a first steep slope region that is lower than the full charge capacity of the storage battery and a second steep slope region that corresponds to the full charge capacity of the storage battery, and the region determination unit determines that the terminal voltage has transitioned to the first steep slope region or the second steep slope region based on a voltage change rate that indicates the amount of change per unit time in the terminal voltage of the storage battery becoming larger than a predetermined value after the charging device starts charging, and the current history acquisition unit acquires the current history information at that time and remaining capacity estimation data based on the terminal voltage when the voltage change rate becomes larger than the predetermined value, 3. The battery control device according to claim 1, wherein, when charging of the storage battery is terminated at a capacity lower than a full charge capacity, if the remaining capacity estimation data has been acquired by the current history acquisition unit before the present time, the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity estimation data.

8. A battery control device according to claim 1 or 2, wherein the storage battery can be charged by a charging device (42), and when the storage battery is charged by the charging device, a first charge is performed in which the storage battery is charged to a predetermined designated voltage that is lower than the terminal voltage corresponding to the steep region, and a second charge is performed in which the storage battery is charged to the steep region following the first charge, and the impedance measurement unit measures the impedance of the storage battery at the start of the second charge, the current flow history acquisition unit acquires the current flow history information from the start of the second charge, the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region after the start of the second charge, and the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the current flow history information and the remaining capacity of the storage battery corresponding to the terminal voltage at the transition to the steep region after the start of the second charge.

9. The storage battery can be charged by a charging device (42), and when the storage battery is charged by the charging device, a first charge is performed to charge the storage battery to a predetermined designated voltage that is lower than the terminal voltage corresponding to the steep region, and a second charge is performed to charge the storage battery to the steep region following the first charge; the storage battery comprises: an actual capacity estimation unit that estimates an actual capacity that is the actual remaining capacity of the storage battery at the end of the first charge; and a capacity determination unit that determines whether a capacity difference between the actual capacity estimated by the actual capacity estimation unit and a designated capacity that is predetermined as the remaining capacity at the end of the first charge is smaller than a predetermined value; the impedance measurement unit measures the impedance of the storage battery at the start of the second charge; the current flow history acquisition unit acquires the current flow history information from the start of the second charge; and the region determination unit determines that the terminal voltage of the storage battery has transitioned to the steep region after the start of the second charge.

3. The battery control device according to claim 1, wherein the capacity calculation unit calculates the remaining capacity at the time of impedance measurement by the impedance measurement unit based on the remaining capacity of the storage battery corresponding to the terminal voltage at the time of transition to the steep region after the start of the second charging and the current flow history information, on the condition that the capacity determination unit determines that the capacity difference is smaller than a predetermined value.

10. The battery control device according to claim 9, further comprising a voltage adjusting section that adjusts the designated voltage when the capacity determining section determines that the capacity difference is greater than a predetermined value.

11. A program applied to a power supply system (10) having a storage battery (20, 21) and executed by a computer, wherein the storage battery has, in battery characteristics indicating the relationship between remaining capacity and terminal voltage, a gradual region where the change in terminal voltage relative to a change in remaining capacity is relatively small, and a steep region where the change in terminal voltage relative to a change in remaining capacity is relatively large, the program comprising: an impedance measurement process for measuring the impedance of the storage battery; a current history acquisition process for acquiring a history of current flow through the storage battery from the time of measurement of the impedance to after the measurement as current flow history information; a region determination process for determining that the terminal voltage of the storage battery has transitioned from the gradual region to the steep region when current is flowing through the storage battery after measurement of the impedance; and a capacity calculation process for calculating the remaining capacity at the time of impedance measurement by the impedance measurement process based on the remaining capacity of the storage battery corresponding to the terminal voltage in the steep region and the current flow history information, when it is determined by the region determination process that the terminal voltage of the storage battery has transitioned to the steep region.

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