Power storage device, information processing method, and computer program

Abstract

To provide a technology of improving the accuracy of detecting variation of the remaining capacitance in power storage cells.SOLUTION: A power storage device includes a power storage unit having a plurality of power storage cells connected in series and a control unit. The control unit acquires the remaining capacitance value of the power storage unit or the power storage cells, and performs full-charging control on the power storage unit when the remaining capacitance value falls within a prescribed range.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a power storage device, an information processing method, and a computer program. [Background technology]

[0002] In an energy storage device that stores a number of storage cells connected in series, the remaining charge may vary over time among the storage cells. To suppress such variation in the remaining charge among the storage cells, a balancer that equalizes the voltage among the storage cells is known.

[0003] Patent Document 1 proposes a capacity adjustment device that equalizes the capacity among a plurality of cells. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-244058 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the technique of Patent Document 1, there are cases where the accuracy of detecting the remaining capacity variation among the power storage cells is not sufficient.

[0006] An object of the present disclosure is to provide a technique capable of improving the accuracy of detecting remaining capacity variations among power storage cells. [Means for solving the problem]

[0007] According to an aspect of the present disclosure, there is provided an energy storage device including an energy storage unit having a plurality of energy storage cells connected in series, and a control unit, the control unit acquiring a remaining capacity value of the energy storage unit or the energy storage cells, and performing full charge control on the energy storage unit when the remaining capacity value is within a predetermined range. The energy storage device may further include a balancer electrically connected to each of the energy storage cells, and the control unit may determine, when the remaining capacity value is within a predetermined range, an amount of imbalance of each of the energy storage cells to be equalized by the balancer based on the voltage of each of the energy storage cells after full charge control. Effect of the Invention

[0008] According to the present disclosure, it is possible to improve the accuracy of detecting the remaining capacity variation among the power storage cells. In particular, the technology of the present disclosure can be suitably applied to a power storage unit having a plateau region in its SOC (State of Charge)-OCV (Open Circuit Voltage) profile. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the relationship between the SOC of an LFP / Gr battery and the OCV of each cell and the voltage difference between the cells. [Diagram 2] 1 is a graph showing voltage and current values ​​during charging when the charge start SOC is 0% and when the charge start SOC is 85%. [Diagram 3] 1 is a graph showing the relationship between the SOC of an LFP / Gr battery and the voltage difference between the cells for each remaining capacity variation. [Figure 4] FIG. 2 is a perspective view illustrating a configuration example of a power storage device. [Diagram 5] FIG. [Figure 6] FIG. 2 is a block diagram showing a configuration example of a power storage device. [Figure 7] 13 is a flowchart illustrating an example of an equalization process procedure. [Figure 8] FIG. 11 is a diagram illustrating an imbalance determination. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (1) An energy storage device according to one aspect of the present disclosure includes an energy storage unit having a plurality of energy storage cells connected in series, and a control unit, the control unit acquiring a remaining capacity value of the energy storage unit or the energy storage cells, and performing full charge control on the energy storage unit when the remaining capacity value is within a predetermined range.

[0011] Here, the remaining capacity may be the SOC or the amount of dischargeable electricity. The SOC may be the ratio of the remaining capacity to the full charge capacity of the power storage unit or power storage cell at that time (so-called RSOC (Relative State Of Charge)), or may be the ratio of the remaining capacity to the full charge capacity according to the specifications (so-called ASOC (Absolute State Of Charge)). The remaining capacity may be a physical quantity expressed in units of Ah (ampere-hours).

[0012] In an energy storage device that stores multiple storage cells connected in series, a balancer is used to equalize the voltage (residual capacity) variations that occur between the storage cells, thereby preventing overcharging or overdischarging of the energy storage device. In the equalization process, the other storage cells are discharged to match the voltage of a specific storage cell, thereby equalizing the voltage between the storage cells. To operate the balancer, it is necessary to accurately detect the voltage difference between the cells and determine the amount of imbalance according to the voltage difference.

[0013] Some storage cells have a plateau region in the SOC-OCV profile. The plateau region is a region where there is almost no change in OCV relative to the change in SOC (almost horizontal). As storage cells having a plateau region, for example, iron-based storage cells in which iron is contained in the positive electrode active material are known, and in particular, LFP / Gr-based lithium-ion secondary batteries are known. In the case of storage cells having a plateau region, it is difficult to detect the voltage difference of the storage cell within the plateau region.

[0014] FIG. 1 is a diagram showing the relationship between the SOC of an LFP / Gr battery and the OCV of each cell and the voltage difference between the cells. The horizontal axis of FIG. 1 is SOC (unit: %), the left vertical axis is OCV (unit: volts (V)), and the right vertical axis is the voltage difference between the cells (unit: V). In FIG. 1, a solid line 101 indicates the SOC-OCV profile of the first cell, a solid line 102 indicates the SOC-OCV profile of the second cell, and a dashed line 103 indicates the voltage difference between the cells. FIG. 1 shows an example in which an LFP / Gr battery has remaining capacity variation, and the remaining capacity of the second cell is 2% lower than that of the first cell.

[0015] As shown in Figure 1, when the SOC is in the plateau region, the OCV is almost constant, so even if there is an imbalance between the cells, no voltage variation occurs and it is difficult to detect the voltage difference. When the SOC is not in the plateau region, the OCV changes, so voltage variation occurs due to the imbalance, making it possible to detect the voltage difference.

[0016] It is generally assumed that the charge and discharge of a power storage device is controlled so that the SOC is within a preset usable range. For example, if the power storage device is a low-voltage battery mounted on a vehicle, the charge and discharge are controlled so that the SOC is 50% to 90%. In the case of a power storage cell having a plateau region, full charge control may be performed in order to detect the voltage difference.

[0017] The inventors of the present application have found that the current characteristics differ depending on the SOC at the start of charging. Fig. 2 is a graph of the voltage and current values ​​during charging when the charge start SOC is 0% and when the charge start SOC is 85%. The horizontal axis of Fig. 2A is SOC (%) and the vertical axis is voltage (V). The horizontal axis of Fig. 2B is SOC (%) and the vertical axis is current (A). Fig. 2C is an enlarged view of a part of the graph of Fig. 2B.

[0018] In the example of full charge control shown in Figure 2, constant current charging (CC charging) is performed at a constant current value until the voltage value reaches a predetermined voltage value, and once the voltage value reaches the predetermined voltage value, constant voltage charging (CV charging) is performed at a constant voltage value. When switching to constant voltage charging, the current value of the charging current gradually decreases, and charging ends when the current value drops to a predetermined full charge end threshold. For convenience, in the following explanation, the state when the current value drops to the predetermined full charge end threshold is referred to as full charge, and the timing when the current value drops to the predetermined full charge end threshold is taken as the completion point of full charge control. Full charge does not necessarily mean that the SOC is 100%.

[0019] As shown in FIG. 2, the lower the SOC when charging starts, the lower the SOC when full charge control is completed.

[0020] FIG. 3 is a graph showing the relationship between the SOC of an LFP / Gr battery and the voltage difference between cells for each remaining capacity variation. The horizontal axis of FIG. 3 is SOC (%), and the vertical axis is the voltage difference between cells (V). In FIG. 3, solid line 104 shows the case where the remaining capacity variation between the first cell and the second cell is 0.4%, and solid line 105 shows the case where the remaining capacity variation between the first cell and the second cell is 0.2%. In the range of SOC of about 98.3% or less, the voltage difference is almost not generated regardless of the amount of imbalance. In the range of SOC exceeding about 98.3%, the higher the SOC, the larger the voltage difference becomes. The voltage difference increases as the remaining capacity variation becomes larger.

[0021] As described above, in a storage cell having a plateau region, when the SOC value at which full charge control is completed becomes low, the voltage difference between the cells does not appear even if an imbalance occurs between the cells, making it difficult to detect the amount of imbalance from the voltage difference.

[0022] According to the above-mentioned (1) power storage device, when the remaining capacity value of the power storage unit or the power storage cell is within a predetermined range, full charge control is performed on the power storage unit. The predetermined range may be, for example, a usable range set for the power storage unit or the power storage cell. By starting charging when the remaining capacity value is relatively high, it is possible to suppress a decrease in SOC when full charge is completed, and it is possible to accurately detect voltage variations and improve the detection accuracy of remaining capacity variations.

[0023] (2) In the energy storage device described in (1) above, a balancer may be provided that is electrically connected to each of the energy storage cells, and the control unit may determine the amount of imbalance of each of the energy storage cells to be equalized by the balancer based on the voltage of each of the energy storage cells after full charge control. The voltage after full charge control may be the voltage at the time when full charge control is completed.

[0024] According to the energy storage device of (2) above, by determining the amount of imbalance between the cells based on the voltage of each storage cell after full charge control in which the voltage difference is well expressed, it becomes possible to determine the capacity of the storage cell to within, for example, 0.1% order, and the accuracy of detecting the amount of imbalance can be improved. By limiting the conditions for executing full charge control, the voltage variation and the amount of imbalance can be detected with high accuracy, eliminating the need for complex correction processing, and facilitating the configuration of the energy storage device. It is possible to reduce the possibility that the voltage difference cannot be detected even when an imbalance occurs between the storage cells, and to suppress the occurrence of an overcharged state of the energy storage device at unintended timing.

[0025] (3) In the energy storage device described in (1) or (2) above, the control unit may perform full charge control on the energy storage unit when the remaining capacity value is within a predetermined range and a specific time has elapsed since the remaining capacity value entered the predetermined range.

[0026] According to the above-mentioned energy storage device (3), by taking into account the time elapsed since the remaining capacity value fell within a predetermined range as an additional condition for determining whether to perform full charge control, the charging start SOC can be further increased, and the accuracy of detecting voltage variations can be improved.

[0027] (4) In the energy storage device described in any one of (1) to (3) above, the control unit may output a full charge request for the energy storage unit when the remaining capacity value is within a predetermined range or when a specific time has elapsed since the remaining capacity value entered the predetermined range.

[0028] According to the power storage device described in (4) above, a full charge request can be output when a predetermined requirement is satisfied. The full charge request may be output to, for example, a vehicle ECU (Electronic Control Unit) that controls the amount of charge or discharge of a vehicle in which the power storage device is mounted. The vehicle ECU is an example of a higher-level device. By having the vehicle ECU fully charge the battery in response to the full charge request, the timing of full charge can be adjusted, and the detection accuracy of voltage variation can be improved.

[0029] (5) In the energy storage device described in any one of (1) to (4) above, the control unit may acquire a voltage of each storage cell after full charge control, and based on the acquired voltage of each storage cell, determine a discharge amount of each storage cell by a balancer electrically connected to each storage cell, based on a voltage between the storage cell having the lowest voltage after full charge control among the storage cells and each of the other storage cells.

[0030] According to the power storage device described in (5) above, by using the voltage of each power storage cell after full charge control in which the voltage difference is well expressed, the discharge amount of each power storage cell can be determined with high accuracy.

[0031] (6) In the energy storage device according to any one of (1) to (5) above, the control unit may correct the SOC value of the energy storage unit estimated by a current integration method that integrates a charging current and / or a discharging current flowing through the energy storage unit, using a voltage of each energy storage cell after full charge control.

[0032] The current integration method is a method of estimating the SOC by measuring the charge / discharge current of the storage cell at a specified time interval using a current sensor and adding / subtracting the measured current value from the initial value. With the current integration method, errors (measurement errors of the current sensor, errors caused by individual differences in the current consumption of the management device that manages the storage cell, errors caused by individual differences in the self-discharge of the storage cell, etc.) accumulate over time.

[0033] According to the energy storage device described in (6) above, it is possible to execute a correction of the SOC value of the energy storage unit estimated by the current integration method based on the voltage of each energy storage cell after full charge control is performed when a predetermined requirement is satisfied, that is, a so-called "full charge reset." Since full charge is performed when a predetermined requirement is satisfied, full charge is completed in a region where the slope of the SOC-OCV profile is steep, and the SOC corresponding to the voltage of the energy storage cell can be accurately estimated.

[0034] (7) In the power storage device according to any one of (1) to (6) above, the power storage cell may contain lithium iron phosphate as a positive electrode active material.

[0035] According to the electricity storage device described in (7) above, since the voltage variation can be detected with high accuracy even in the electricity storage cell having a plateau region, it is particularly useful in the case of an electricity storage cell containing lithium iron phosphate as the positive electrode active material.

[0036] (8) An information processing method according to one aspect of the present disclosure includes a computer executing a process to acquire a remaining capacity value of a storage unit having a plurality of storage cells connected in series or of the storage cells, and, if the remaining capacity value is within a predetermined range, to perform full charge control on the storage unit.

[0037] (9) A computer program according to one embodiment of the present disclosure acquires a remaining capacity value of a storage unit having a plurality of storage cells connected in series or of the storage cells, and, when the remaining capacity value is within a predetermined range, causes a computer to execute a process of performing full charging control on the storage unit.

[0038] The present disclosure will be specifically described with reference to the drawings showing the embodiments thereof.

[0039] (First embodiment) Fig. 4 is a perspective view showing a configuration example of the energy storage device 1, and Fig. 5 is an exploded perspective view of the energy storage device 1. In the following, the configuration example of the energy storage device 1 will be described with reference to the "front-rear," "left-right," and "up-down" directions shown in the drawings.

[0040] The power storage device 1 is a battery that is preferably mounted on vehicles such as engine vehicles, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and other mobile objects. The power storage device 1 may be a 12 volt (V) battery or a 48 V battery.

[0041] The energy storage device 1 includes a plurality of energy storage cells 2, a management device 3, a busbar unit 4, and a circuit board 6. The energy storage cells 2, the management device 3, the busbar unit 4, and the circuit board 6 are housed inside a housing case 10.

[0042] The storage case 10 is made of synthetic resin. The storage case 10 includes a case body 11 with an open top, and a cover 12 that covers the opening of the case body 11. The dimensions of the case body 11 and the cover 12 are designed according to the dimensions and number of the energy storage cells 2 to be stored therein. The case body 11 and the cover 12 are fixed in a liquid-tight manner by means of connectors such as screws, an adhesive, welding, or the like, with the energy storage cells 2, the busbar unit 4, and the circuit board 6 stored therein.

[0043] The storage cell 2 is, for example, a battery cell based on a lithium ion secondary battery. The storage cell 2 is, for example, an LFP battery containing LiFePO4 in the positive electrode active material, and has the plateau region described above.

[0044] The storage cell 2 includes a case 21 having a hollow rectangular parallelepiped shape. A positive terminal 22 and a negative terminal 23 of the storage cell 2 are provided on the upper surface of the case 21. An electrode body, an electrolyte, and the like are accommodated inside the case 21. A single assembled battery 20 is configured by connecting a plurality of storage cells 2. The assembled battery 20 is an example of a power storage unit. FIG. 5 shows the assembled battery 20 having four storage cells 2 connected in series. Some of the storage cells 2 may be connected in parallel.

[0045] Although not shown in detail, the electrode body is constructed by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode with two sheet-shaped separators between them and winding them (vertically or horizontally). The separator is formed of a porous resin film. As the porous resin film, a porous resin film made of a resin such as polyethylene (PE) or polypropylene (PP) can be used.

[0046] The positive electrode is an electrode plate in which a positive electrode active material layer is formed on the surface of a long strip-shaped positive electrode substrate made of, for example, aluminum, an aluminum alloy, or the like. The positive electrode active material layer contains a positive electrode active material. As the positive electrode active material used in the positive electrode active material layer, a material capable of absorbing and releasing lithium ions can be used. The positive electrode active material layer may further contain a conductive assistant, a binder, and the like.

[0047] The negative electrode is an electrode plate in which a negative electrode active material layer is formed on the surface of a long strip-shaped negative electrode substrate made of, for example, copper or a copper alloy. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material can be a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include graphite, hard carbon, and soft carbon. The negative electrode active material layer may further contain a binder, a thickener, and the like.

[0048] The electrolyte may be the same as that used in conventional lithium ion secondary batteries. For example, an electrolyte containing a supporting salt in an organic solvent may be used. For example, aprotic solvents such as carbonates, esters, and ethers are used as the organic solvent. For example, lithium salts such as LiPF6, LiBF4, and LiClO4 are preferably used as the supporting salt. The electrolyte may contain various additives such as a gas generating agent, a film forming agent, a dispersing agent, and a thickening agent.

[0049] 5, the storage cells 2 are housed in the case body 11 such that the orientations of the positive terminals 22 and the negative terminals 23 of adjacent storage cells 2 are opposite. In the following description, the storage cells 2 are also referred to as a first storage cell 2A, a second storage cell 2B, a third storage cell 2C, and a fourth storage cell 2D, in that order from the front side of the case body 11.

[0050] The energy storage device 1 is provided with a charge / discharge path that electrically connects the storage cells 2 housed in the case body 11 to the external terminals 13A and 13B. A part of the charge / discharge path is configured by a bus bar (not shown). For example, the negative terminal 23 of the first storage cell 2A is connected to the external terminal 13A via the bus bar. The positive terminal 22 of the first storage cell 2A and the negative terminal 23 of the second storage cell 2B are connected to each other via the bus bar. The positive terminal 22 of the second storage cell 2B and the negative terminal 23 of the third storage cell 2C are connected to each other via the bus bar. The positive terminal 22 of the third storage cell 2C and the negative terminal 23 of the fourth storage cell 2D are connected to each other via the bus bar. The positive terminal 22 of the fourth storage cell 2D is connected to the external terminal 13B via the bus bar. In this way, the storage cells 2A to 2D are connected in series by the bus bar.

[0051] A busbar unit 4 is disposed on the terminal surface of the energy storage cell 2. The busbar unit 4 includes the above-mentioned busbars and a resin busbar frame 40 that holds the busbars. A circuit board 6 is disposed on the upper surface of the busbar frame 40. The circuit board 6 is fixed to the busbar frame 40 via a spacer 41, for example, in a state spaced apart from the upper surface of the busbar frame 40.

[0052] In the embodiment, the storage cell 2 is a battery cell based on an LFP-based lithium ion secondary battery having a plateau region. Alternatively, the storage cell 2 may be another type of secondary battery having a plateau region. The storage cell 2 is not limited to one having a plateau region. The storage cell 2 may be an all-solid-state battery or a capacitor.

[0053] In the embodiment, the power storage cell 2 is a rectangular battery cell equipped with a wound electrode assembly. Alternatively, the power storage cell 2 may be a cylindrical battery cell or a laminated (pouch) battery cell, or may be a battery cell equipped with a laminated electrode assembly.

[0054] In the embodiment, the number of storage cells 2 housed in the case body 11 is four. Alternatively, the number of storage cells 2 housed in the case body 11 may be equal to or greater than one and less than four, or may be more than four. The battery pack 20 may include, for example, twelve storage cells 2 connected in three parallel and four series.

[0055] 6 is a block diagram showing a configuration example of the power storage device 1. The power storage device 1 includes a battery pack 20, a management device 3, a balancer 61, a cutoff circuit 62, a temperature sensor 63, a current sensor 64, and a voltage sensor 65. The management device 3, the balancer 61, the cutoff circuit 62, the temperature sensor 63, the current sensor 64, and the voltage sensor 65 may be mounted on a circuit board 6 and configured as a circuit board unit.

[0056] The power storage device 1 is connected to a vehicle ECU 71, an electric load 72 such as an electric component, and an alternator (not shown) via external terminals 13A and 13B. The vehicle ECU 71 is a vehicle control unit that controls the vehicle. The vehicle ECU 71 controls the amount of charge or discharge of the power storage device 1 by controlling the electric load 72.

[0057] If the vehicle is an engine vehicle, while the engine is running, if the amount of power generated by the alternator is greater than the amount of power consumed by the electrical load 72, the electrical storage device 1 is charged by the alternator. If the amount of power generated by the alternator is less than the amount of power consumed by the electrical load 72, the electrical storage device 1 discharges to make up for the shortfall. While the vehicle is parked, the alternator stops generating power, so the electrical storage device 1 is not charged and only discharges to the vehicle ECU 71 and the electrical load 72.

[0058] When the vehicle can start traveling using a high-voltage system (driving power storage device) instead of an internal combustion engine, the power storage device 1 supplies power to enable the high-voltage system to start. While the vehicle is parked, the power storage device 1 discharges to the vehicle ECU 71 and the electric load 72, and can also be charged by the high-voltage system.

[0059] The management device 3 is, for example, a Battery Management Unit (BMU) that manages the state of the storage cells 2. When the SOC of the storage cells 2 satisfies a predetermined condition, the management device 3 executes control for performing an equalization process for equalizing the voltages (capacities) between the storage cells 2. In one example, the management device 3 is mounted on a circuit board 6. Alternatively, the management device 3 may be mounted on a board different from the circuit board 6, or may be a computer such as a terminal device or a server device connected to the outside of the storage device 1.

[0060] The balancer 61 is an equalization circuit for equalizing the voltages of the storage cells 2. A plurality of balancers 61 are provided according to the number of the storage cells 2, and each is connected in parallel to a different storage cell 2. The balancer 61 includes, for example, a discharge load and a switch such as a FET (Field Effect Transistor) or a relay, and consumes the amount of electricity of the storage cells 2 by passing a current through the discharge load. When the balancer 61 is activated and the switch is turned on, the storage cells 2 are discharged via the discharge load. By discharging the storage cell 2 with a large capacity, the voltages (residual capacity) of the storage cells 2A to 2D can be equalized.

[0061] The interruption circuit 62 is a circuit for connecting or interrupting a charge / discharge path (current path) between the positive terminal 22 of the fourth storage cell 2D and the external terminal 13B. The interruption circuit 62 is formed of a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET). By switching the interruption circuit 62 from an on state to an off state, it is possible to interrupt the outflow of current from the storage cell 2 to the outside and the inflow of current from the outside to the storage cell 2. Alternatively, the interruption circuit 62 may be formed of a relay switch.

[0062] The temperature sensor 63 is, for example, a thermistor, a thermocouple, etc. The temperature sensor 63 measures the temperature of the power storage cell 2 or the power storage device 1 in a time series manner. The temperature sensor 63 may be disposed at a position sufficiently separated from an electrically-applied heat-generating body on the circuit board 6 (for example, the interrupter circuit 62, a bus bar, a fastener, etc.).

[0063] The current sensor 64 is, for example, a shunt resistor, and is connected in series to the storage cell 2. The current sensor 64 measures the current flowing through the storage cell 2 in a time series manner based on the voltage across the storage cell 2. Discharging and charging can be determined from the polarity (positive / negative) of the voltage across the cells. Alternatively, the current sensor 64 may be a magnetic sensor.

[0064] The voltage sensor 65 is connected in parallel to each storage cell 2. The voltage sensor 65 is connected to both ends of each storage cell 2, and measures the terminal voltage of each storage cell 2 and the total voltage of the battery pack 20 in time series.

[0065] The management device 3 is a computer, and includes a control unit 31, a storage unit 32, and a communication unit 33. The management device 3 may be configured to perform distributed processing using multiple computers, may be realized by multiple virtual machines provided in one server, or may be realized by using a cloud server.

[0066] The control unit 31 is an arithmetic circuit including a central processing unit (CPU), a graphics processing unit (GPU), a read only memory (ROM), a random access memory (RAM), etc. The CPU or GPU included in the control unit 31 executes various computer programs stored in the ROM or the storage unit 32, and controls the operation of each of the above-mentioned hardware components. The control unit 31 may include functions such as a timer that measures the elapsed time from when an instruction to start measurement is given to when an instruction to end measurement is given, a counter that counts numbers, and a clock that outputs date and time information.

[0067] The storage unit 32 includes a non-volatile storage device such as a flash memory or a hard disk drive. The storage unit 32 stores various computer programs, data, and the like referenced by the control unit 31. The storage unit 32 may be an external storage device connected to the management device 3. The storage unit 32 of this embodiment stores a program 321 for causing a computer to execute a process related to equalization, and a characteristic table 322. The characteristic table 322 is data indicating, in a table format, a relative relationship between the closed circuit voltage (CCV) of the storage cell 2 and the remaining capacity (CCV-remaining capacity characteristic). The CCV-remaining capacity characteristic may be stored as a graph, a formula, or the like.

[0068] A computer program (computer program product) including the program 321 may be provided by a non-transitory recording medium 3A on which the computer program is readably recorded. The recording medium 3A is, for example, a portable memory such as a magnetic disk, an optical disk, or a semiconductor memory. The control unit 31 reads a desired computer program from the recording medium 3A using a reading device (not shown) and stores the read computer program in the storage unit 32. Alternatively, the computer program may be provided by communication. The program 321 may be a single computer program or may be composed of multiple computer programs, and may be executed on a single computer or multiple computers interconnected by a communication network.

[0069] The communication unit 33 includes a communication interface for transmitting and receiving various signals and data. In response to an instruction from the control unit 31, the communication unit 33 transmits to the circuit board 6 a control signal for opening and closing the balancer 61 switch and a control signal for opening and closing the switch of the interrupter circuit 62. The communication unit 33 receives temperature data output from the temperature sensor 63, current data output from the current sensor 64, and voltage data output from the voltage sensor 65. The communication unit 33 transmits and receives various data including a full charge request to and from the vehicle ECU 71 or other external devices.

[0070] 7 is a flowchart showing an example of an equalization process procedure. The control unit 31 of the management device 3 executes the following process according to the program 321. The control unit 31 repeatedly executes the following process, for example, at predetermined time intervals (for example, every six months, every three months, etc.). The control unit 31 may start the following process when a predetermined requirement is satisfied (for example, when a predetermined period has passed since the previous SOC reset).

[0071] The control unit 31 of the management device 3 acquires the current SOC value of the battery pack 20 (step S11). The SOC of the battery pack 20 may be calculated by a current integration method. The current integration method is a method in which the amount of power flowing in and out of the battery storage device 1 is measured by measuring the charge / discharge current of the battery storage device 1 at a predetermined time interval using the current sensor 64, and the SOC is estimated by adding or subtracting this from the initial capacity. The control unit 31 executes an SOC estimation process using the current integration method at a predetermined interval, for example, and stores the obtained SOC in the storage unit 32 in association with the estimated date and time.

[0072] The control unit 31 determines whether the acquired current SOC value of the battery pack 20 is within a preset control range (step S12). The control range may be, for example, a usable range (e.g., SOC 50% to 90%) set for the battery pack 20, or may be an SOC range set for this determination process. Alternatively, the control unit 31 may acquire the current SOC value of one or more storage cells 2, and determine whether the current SOC value of one or more storage cells 2 is within a preset control range.

[0073] When it is determined that the current SOC value of the battery pack 20 is not within the preset control range (S12: NO), the control unit 31 ends the process. The control unit 31 may return the process to step S11 and wait until the SOC value falls within the preset control range.

[0074] When it is determined that the current SOC value is within the preset control range (S12: YES), the control unit 31 determines whether a preset specific time has elapsed since the SOC value of the battery pack 20 entered the preset control range (step S13). The elapsed time since the SOC value entered the control range can be calculated based on the SOC time-series data stored in the memory unit 32. The control unit 31 may skip the determination of whether the specific time has elapsed and proceed to step S14.

[0075] When it is determined that the specific time has not elapsed since the SOC value of the battery pack 20 entered the control range (S13: NO), the control unit 31 returns the process to step S13 and waits until the specific time has elapsed.

[0076] When it is determined that a specific time has elapsed since the SOC value of the battery pack 20 entered the control range (S13: YES), the control unit 31 executes full charge control on the battery pack 20 (step S14). In step S14, the control unit 31 may output a full charge request to a higher-level device such as the vehicle ECU 71. In response to the full charge request received from the management device 3, the vehicle ECU 71 starts charging the battery pack 20.

[0077] After the full charge control is completed, the control unit 31 acquires the voltage of each storage cell 2 after the full charge control (step S15), and calculates the remaining capacity of each storage cell 2 based on the acquired voltage of each storage cell 2 (step S16). The control unit 31 determines the discharge amount of each storage cell 2 by the balancer 61 based on the calculated remaining capacity of each storage cell 2 (step S17). The processing of steps S15 to S17 corresponds to the imbalance determination.

[0078] 8 is a diagram for explaining the imbalance determination. The processes in steps S15 to S17 will be described in detail with reference to FIG.

[0079] The graph on the left side of FIG. 8 shows the change over time in the charging voltage (cell voltage) and charging current of each storage cell 2 during full charge control. During full charge control of the battery pack 20, charging is controlled so that the highest cell voltage does not exceed a preset maximum charging voltage. For example, consider an assembled battery 20 in which four storage cells 2A-2D, each with a maximum cell charging voltage of 3.5V, are connected in series. When charging is performed at the maximum charging voltage of the assembled battery 20, if there is no variation in the remaining capacity of each storage cell 2A-2D, the cell voltages of the storage cells 2A-2D at the completion of full charge control will all be 3.5V. In reality, since there is variation in the remaining capacity of each storage cell 2A-2D, the cell voltages of the storage cells 2A-2D at the completion of full charge control are not uniform, as shown in FIG. 8. The storage cells 2 that are charged with the maximum cell charging voltage are fully charged, but the storage cells 2 whose charging voltage has dropped are insufficiently charged according to the amount of voltage variation and are not fully charged.

[0080] In step S15, the control unit 31 acquires the voltage of each of the storage cells 2A-2D at the time when the full charge control is completed, i.e., at the time when the current value of the CV charging reaches a predetermined full charge end threshold, based on the current data and voltage data of the storage cells 2A-2D. The voltages of the storage cells 2A-2D may be CCV detected by the voltage sensor 65. The control unit 31 identifies the storage cell 2 with the smallest voltage after the full charge control as the minimum cell.

[0081] In step S16, the control unit 31 refers to the characteristics table 322 of the CCV-residual capacity characteristics stored in the storage unit 32, and obtains the residual capacity corresponding to the CCV of each of the storage cells 2A to 2D after the full charge control.

[0082] The CCV-remaining capacity characteristic may be generated by obtaining a correlation between the CCV and remaining capacity of the storage cell 2 at a predetermined full charge end threshold value by an experiment or the like in advance. When the OCV of the storage cell 2 can be detected, the SOC and remaining capacity can be calculated from the detected OCV of the storage cell 2 by using the SOC-OCV profile. In the case of a vehicle-mounted storage cell 2, various electric loads are connected to the storage cell 2, and there is almost no timing when the amount of current flowing through the storage cell 2 becomes zero or approximately zero. Therefore, the remaining capacity is obtained by using the CCV instead of the OCV of the storage cell 2. By setting the full charge end threshold value to a sufficiently small value, the influence of the internal resistance of the storage cell 2 can be reduced, and the detection accuracy of the remaining capacity can be improved. In order to take into account the influence of the actual capacity variation due to the deterioration of the storage cell 2, the depth of discharge may be used instead of the remaining capacity.

[0083] In step S17, the control unit 31 uses the remaining capacity of the identified minimum cell as a reference and calculates the difference between the remaining capacity of the minimum cell and the remaining capacities of the other storage cells 2 for each storage cell 2. The obtained remaining capacity difference is set as the discharge amount of the balancer 61.

[0084] Returning to Fig. 7, the description will continue. The control unit 31 operates the balancer 61 of the storage cells 2 to be equalized in accordance with the determined discharge amount (step S18). The balancer 61 discharges the storage cells 2 other than the minimum cell, and the voltages (residual capacities) of the storage cells 2A to 2D are equalized.

[0085] The control unit 31 executes SOC reset based on the voltages of the storage cells 2A to 2D after the full charge control, thereby correcting the SOC estimated by the current integration method (step S19). The control unit 31 calculates the SOC values ​​of the storage cells 2A to 2D based on the remaining capacities corresponding to the voltages of the storage cells 2A to 2D after the full charge control obtained by the unbalance determination, and the known actual capacities of the storage cells 2A to 2D. The control unit 31 corrects the SOC of the storage cells 2A to 2D by the current integration method with the calculated SOC of the storage cells 2A to 2D. Alternatively, the control unit 31 may regard the voltages of the storage cells 2A to 2D after the full charge control as the OCV, estimate the SOC from the voltages of the storage cells 2A to 2D after the full charge control using the SOC-OCV profile, and correct the SOC by the current integration method with the estimated SOC. The process of step S19 may be omitted. The control unit 31 ends the series of processes.

[0086] In the above-described process, the control unit 31 may execute the process from step S15 onwards even when full charge control is performed on the battery pack 20 independently of the full charge control in step S14. In this case, it is preferable that the control unit 31 executes steps S11 to S13 in parallel, and when it is determined that the predetermined condition is satisfied, executes the process from step S14 onwards again.

[0087] According to this embodiment, by controlling the timing of full charging for the equalization process in accordance with the SOC of the battery pack 20, it is possible to suppress a decrease in SOC after full charging control and improve the detection accuracy of the voltage difference and the amount of imbalance.

[0088] The power storage device may be a high-voltage battery (a battery for driving a moving object) mounted on a vehicle or other moving object.

[0089] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims. The sequences shown in each embodiment are not limited, and the order of each process may be changed and multiple processes may be executed in parallel, as long as there is no contradiction. The subject of each process is not limited, and the process of each device may be executed by another device, as long as there is no contradiction.

[0090] The matters described in each embodiment can be combined with each other. In addition, the independent claims and dependent claims described in the claims can be combined with each other in any and all combinations regardless of the citation format. Furthermore, the claims use a format in which a claim cites two or more other claims (multiple claim format), but this is not limited to this. A multiple claim (multi-multi claim) that cites at least one multiple claim may also be used. [Explanation of symbols]

[0091] 1. Energy storage device 2. Energy storage cell 20 Battery pack 61 Balancer 3 Management device 31 Control Unit 32 Storage section 33 Communications Department 321 Program 322 Characteristics Table 3A Recording Media

Claims

1. The power storage device includes a power storage unit having a plurality of power storage cells connected in series, and a control unit. The control unit is Acquire a remaining capacity value of the power storage unit or the power storage cell; When the remaining capacity value is within a predetermined range, full charge control is performed on the power storage unit. Energy storage device.

2. A balancer is provided which is electrically connected to each of the storage cells; The control unit determines an amount of imbalance of each of the power storage cells to be equalized by the balancer based on a voltage of each of the power storage cells after full charge control. The power storage device according to claim 1 .

3. When the remaining capacity value is within a predetermined range and a specific time has elapsed since the remaining capacity value entered the predetermined range, the control unit performs full charge control on the power storage unit. The power storage device according to claim 1 .

4. When the remaining capacity value is within a predetermined range or when a specific time has elapsed since the remaining capacity value entered the predetermined range, the control unit outputs a full charge request for the power storage unit. The power storage device according to claim 1 or 2.

5. Obtain the voltage of each storage cell after full charge control. Based on the acquired voltage of each storage cell, a discharge amount of each storage cell is determined by a balancer electrically connected to each storage cell, based on the voltage of the storage cell having the lowest voltage after full charge control among the storage cells and the voltage of each of the other storage cells. The power storage device according to claim 1 or 2.

6. The voltage of each power storage cell after full charge control is used to correct the SOC value of the power storage unit estimated by a current integration method that integrates a charging current and / or a discharging current flowing through the power storage unit. The power storage device according to claim 1 or 2.

7. The storage cell contains lithium iron phosphate as a positive electrode active material. The power storage device according to claim 1 or 2.

8. Acquire a remaining capacity value of a storage unit having a plurality of storage cells connected in series or the storage cells; When the remaining capacity value is within a predetermined range, full charge control is performed on the power storage unit. An information processing method in which processing is performed by a computer.

9. Acquire a remaining capacity value of a storage unit having a plurality of storage cells connected in series or the storage cells; When the remaining capacity value is within a predetermined range, full charge control is performed on the power storage unit. A computer program that causes a computer to carry out processing.

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