Battery control device and battery control method

Abstract

The system includes: a current sensor 14 for detecting battery state; and a battery controller 12 for estimating the battery's state of charge (SOC) based on the detected data and calculating the allowable charging and discharging current. The battery controller calculates the allowable current based on an equivalent circuit model including resistive and capacitive elements, and the battery data table correlates these elements, along with the battery state and SOC. The battery controller uses the estimated SOC as the average SOC, calculates the local SOC based on the average SOC and the charge amount of the capacitive elements, and calculates the allowable current based on the local SOC, the detected data, and the battery data table.

Description

Technical Field

[0001] This invention relates to a battery control device and a battery control method. Background Technology

[0002] In recent years, the use of battery control devices with multiple built-in batteries, such as energy storage devices for mobile devices, energy storage devices for system interconnection stabilization, and emergency energy storage devices, has been expanding. To maximize the performance of these devices, battery control must appropriately calculate the battery's state of charge (SOC), state of decay (SOH), and maximum charge / discharge current (allowable current). SOC indicates the degree to which the battery has been charged or the amount of dischargeable charge remaining. SOH indicates the degree to which the battery has deteriorated from its initial state. The allowable current is the maximum current that the battery can charge / discharge within its upper and lower voltage limits.

[0003] The allowable current of a battery includes the allowable charging current, which represents the allowable current during charging, and the allowable discharging current, which represents the allowable current during discharging. When the State of Charge (SOC) is high, the allowable charging current decreases, and the allowable discharging current increases. Conversely, when the SOC is low, the allowable charging current increases, and the allowable discharging current decreases. The battery control device accurately determines the allowable current to maximize the battery's charging and discharging performance. If the battery control device incorrectly estimates the allowable current, the battery voltage may deviate from its upper and lower limits. Therefore, establishing a highly accurate method for detecting the allowable current is crucial. As prior art related to allowable current detection, for example, a battery state detection device is disclosed in Patent Document 1.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2016-023968 Summary of the Invention The problem the invention aims to solve In the prior art of Patent Document 1, the following is described: The battery state detection device determines the OCV (Open circuit voltage), DC resistance and polarization resistance based on the estimated SOC reference battery data sheet, and predicts the allowable current by dividing the difference between the current OCV and the upper and lower limit voltages by the calculated internal resistance.

[0005] However, even with the permissible current estimated using the prior art as described above, it is desirable to suppress situations where the battery voltage deviates from the upper and lower limits due to high-current charging and discharging. Therefore, the object of the present invention is to provide a battery control device that employs an equivalent circuit, has a low computational load, and can predict sharp rises or falls in battery voltage during high-current charging and discharging, thus enabling high-precision determination of the permissible current.

[0006] means for solving problems To achieve the aforementioned objective, the present invention provides a battery control device that controls the charging and discharging of a battery. The device includes: a detection unit for detecting the battery state; a charging state estimation unit for estimating the charging state of the battery based on detection data from the detection unit; and an allowable current calculation unit for calculating the allowable charging and discharging current of the battery based on an equivalent circuit model of the battery and a data structure. The equivalent circuit model includes resistive and capacitive elements, and the data structure associates the resistive element, the capacitive element, the battery state, and the charging state. The allowable current calculation unit takes the charging state estimated by the charging state estimation unit as a first charging state, calculates a second charging state based on the first charging state and the charge amount of the capacitive element, and calculates the allowable current based on the second charging state and the detection data detected by the detection unit, referring to the data structure.

[0007] The effects of the invention According to the present invention, a battery control device and a battery control method are provided, which employ an equivalent circuit, have a small computational load, and can predict the sharp rise or fall of battery voltage when the battery is charged and discharged with a large current. Therefore, the allowable current can be calculated with high accuracy. Attached Figure Description

[0008] Figure 1 This is a block diagram illustrating the hardware structure of a battery system having an embodiment of the battery control device of the present invention.

[0009] Figure 2 This is a functional block diagram of the battery controller in a battery control device.

[0010] Figure 3 It is a waveform diagram showing the voltage behavior of the battery when a rectangular wave current is applied to the battery.

[0011] Figure 4 This is a block diagram of the equivalent circuit of a battery.

[0012] Figure 5 This is a graph showing the battery parameter table.

[0013] Figure 6AThis is a graph showing the SOC dependence of Ro in the battery parameter table.

[0014] Figure 6B This is a graph showing the SOC dependence of Rp in the battery parameter table.

[0015] Figure 7 This is an example of a flowchart that allows the control actions of the current calculation unit.

[0016] Figure 8 This is a graph showing the shift in battery voltage when using the control of the present invention.

[0017] Figure 9 This is a graph showing the shift in battery voltage when the control of the present invention is not used.

[0018] Figure 10 This is a diagram showing an example of an indicator for a battery control device.

[0019] Figure 11A This is a circuit diagram showing another example of an equivalent circuit.

[0020] Figure 11B This is a circuit diagram showing yet another example of an equivalent circuit. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a block diagram showing the hardware structure of a battery system 100 having an embodiment of the battery control device 1 of the present invention. The battery system 100 includes a battery control device 1, an inverter 2, a load 3 such as a motor, and a host controller 4. Since the output voltage of the battery control device 1 is a DC voltage that varies according to the remaining battery capacity and output current, it is not suitable to directly supply power to the load 3 in some cases. Therefore, the inverter 2 converts the output voltage of the battery control device 1 into three-phase AC and supplies it to the load 3. The battery control device 1 and the inverter 2 are controlled by the host controller 4.

[0022] The same structure is used when supplying DC voltage or other multiphase AC or single-phase AC voltage to load 3. When load 3 outputs power, by setting inverter 2 as a bidirectional inverter, the power output by load 3 can be stored in the battery module within the battery control device 1. By connecting the charging system in parallel with inverter 2, the battery module can also be charged as needed.

[0023] The battery control device 1 sends battery state-related information, such as state of charge (SOC), state of decay (SOH), maximum charge / discharge current (allowable current value), battery temperature, and whether there are any abnormalities in the battery, to the host controller 4. Based on this information, the host controller 4 performs energy management and battery anomaly detection. If the host controller 4 determines that the battery control device 1 should be disconnected from the inverter 2 or the load 3, it sends a disconnection instruction to the battery control device 1.

[0024] The battery control device 1 includes: one or more battery modules 11, each composed of multiple batteries; a battery controller 12, which monitors, estimates, and controls the state of the batteries; a relay 13, which disconnects or connects the output of the battery control device 1; a current sensor 14, which measures the current flowing through the battery module 11; a voltage sensor 15, which measures the voltage of the battery module 11; a leakage current sensor 16, which measures the insulation resistance between the battery control device 1 and ground; a temperature sensor 17, which measures the battery temperature; and a circuit breaker 18, which is controlled according to the output voltage of the battery control device 1. The battery control device 1 has two battery modules 11 connected in series via the circuit breaker 18. The battery controller 12 includes a CPU 121 for performing various calculations and a storage unit 122 storing data tables described later.

[0025] The battery module 11 includes: multiple individual cells; circuitry for measuring the internal temperature of the battery module 11 and the voltage of each individual cell; and circuitry for charging and discharging each individual cell as needed. This enables voltage monitoring and adjustment of each individual cell, and allows for the measurement of temperature information necessary for estimating the battery state, wherein the characteristics of the battery state change according to temperature.

[0026] In the series-connected battery module 11, a current sensor 14 is connected in series with a pair of relays 13. The current sensor 14 measures the current value required to monitor and estimate the state of the battery module 11. By controlling the opening and closing of the pair of relays 13 based on instructions from the host controller 4, the output of the battery control device 1 can be switched on or off. A switch connected in series with the relays 13 can also be added, which is used to manually cut off the power input / output to the battery control device 1 when the voltage of the battery module 11 reaches a high voltage, for example, 100V or higher. By forcibly cutting off the power using a switch, short circuits and other hazards can be prevented during the assembly or disassembly of the battery control device 1, and in response to accidents involving devices equipped with the battery control device 1.

[0027] When multiple battery modules 11 are connected in parallel, relays 13, switches, and current sensors 14 can be installed in each column, or relays 13, switches, and current sensors 14 can be installed only in the output section of the battery control device 1. Alternatively, relays 13, switches, and current sensors 14 can be installed in each column and at both the output section of the battery control device 1.

[0028] Relay 13 can be a single relay device or a combination of a main relay, a precharge relay, and a resistor. In the latter configuration, the precharge relay and the resistor are connected in series, and then they are connected in parallel with the main relay. When connecting relay 13 to the circuit of battery control device 1, the precharge relay is connected first. Since the current flowing through the precharge relay is limited by the series-connected resistor, the inrush current generated by a single relay device can be limited. Furthermore, battery controller 12 connects the main relay after the current flowing through the precharge relay has become sufficiently small. The timing of connecting the main relay can be based on the current flowing through the precharge relay, the voltage applied to the resistor, or the voltage between the terminals of the main relay. It can also be based on the time elapsed after connecting the precharge relay.

[0029] Voltage sensor 15 measures the voltage value required to monitor and estimate the state of battery module 11. Voltage sensor 15 is connected in parallel with one or more battery modules 11. A leakage current sensor 16 is connected to the battery module 11 to detect a state in which leakage may occur before it happens, i.e., to detect a decrease in insulation resistance, thereby preventing accidents from occurring.

[0030] The measured values ​​from battery module 11, current sensor 14, voltage sensor 15, and leakage current sensor 16 are sent to battery controller 12. Based on the received measured values, battery controller 12 monitors, estimates, and controls the battery state of battery module 11. This control includes, for example, charging and discharging each individual cell to equalize the voltage of each cell, power control of each sensor, addressing of each sensor, and control of relay 13 connected to battery controller 12. CPU 121 performs the calculations required for monitoring, estimating, and controlling the battery state.

[0031] The battery control unit 1 may also include a fan for system cooling, which can be controlled by the battery controller 12. By having the battery control unit 1 perform functions including cooling, the battery controller 12 can reduce the amount of communication with the host controller 4.

[0032] exist Figure 1In the example shown, by making the voltage sensor 15 and leakage current sensor 16 separate components from the battery controller 12, greater flexibility in system design is provided. Alternatively, the voltage sensor 15 and leakage current sensor 16 can be integrated into the battery controller 12. This reduces the number of wiring harnesses and the workload of sensor installation. However, since the size of the battery control device 1 that can be handled (maximum output voltage, current, etc.) may be limited due to the built-in sensors, it is preferable to make the sensors separate components in such cases.

[0033] Figure 2 This is a functional block diagram of the battery controller 12. The CPU 121 of the battery controller 12 executes a program to implement a system with multiple functional blocks (deterioration state estimation unit 1201, charging state estimation unit 1202, parameter calculation unit 1203, and allowable current calculation unit 1204). The structure defined by the "units" such as the deterioration state estimation unit 1201 is the function implemented by the program. The term "unit" can be replaced with other terms such as "device," "module," or "unit" in addition to "function." Functional blocks can also be implemented in hardware such as integrated circuits. The battery controller 12 has a storage unit 122. The storage unit 122 stores a battery data table 1205.

[0034] The degradation state estimation unit 1201 and the charging state estimation unit 1202 receive inputs of current I, voltage V, and temperature T from a sensor group 1400 including a current sensor 14, a voltage sensor 15, and a temperature sensor 17. Based on this input information, the degradation state estimation unit 1201 estimates the degradation state of the battery. The object of estimation can be arbitrarily selected as long as it represents an indicator of the battery's degradation state. For example, a reduction in battery capacity could be considered such an indicator. The estimation of a reduction in battery capacity can be performed, for example, by the following method.

[0035] The degradation state estimation unit 1201 accumulates the charge / discharge amounts Q_AB from one time point A to another time point B. Referring to the state of charge estimation unit 1202, the degradation state estimation unit 1201 calculates the OCV_A at time point A and the OCV_B at time point B, and refers to the battery data table 1205 of the initial state to determine the charge / discharge amounts Q_AB corresponding to OCV_A and Q'_AB corresponding to OCV_B. The degradation state estimation unit 1201 uses (Q'_AB) / (Q_AB) as the capacity reduction rate (SOHQ). The degradation state estimation unit 1201 uses the capacity reduction rate, or the capacity reduction rate multiplied by the battery's initial capacity Q_0, as an indicator of the battery's degradation state.

[0036] State of Harm (SOH) can also be calculated using the rate of increase in resistance. For example, the ratio of the battery's initial internal resistance to its current internal resistance can be used as the rate of increase in resistance, and this rate of increase in resistance can be used as the SOH. Alternatively, the SOH of the positive and negative electrodes can be calculated based on their respective capacity reduction rates or resistance increase rates.

[0037] The state-of-charge estimation unit 1202 estimates the battery's state of charge based on the current I, voltage V, and temperature T output from the sensor group 1400 (14, 15, 17) and a model of the battery's equivalent circuit. The battery controller 12 utilizes an equivalent circuit model of a lithium-ion battery in evaluating battery performance during the state-of-charge assessment. (Refer to...) Figure 3 , 4 The equivalent circuit model is explained.

[0038] Figure 3 This is a graph illustrating an example of the voltage behavior of a battery when a rectangular wave current is applied to it. Figure 3 In diagram (A), a rectangular wave current I is applied to the battery, and in diagram (B), the battery voltage V is shown. The horizontal axis of both diagrams represents the elapsed time. When the rectangular wave current I in diagram (A) is applied to the battery, the battery voltage V, i.e., the battery's CCV (closed-circuit voltage), changes as shown by waveform 32 in diagram (B). This voltage V waveform 32 can be roughly divided into three components: the DC voltage component I×Ro (DC resistance component), the polarization voltage component Vp, and the OCV variation component ΔOCV.

[0039] The first component, the DC voltage component I×Ro, responds instantaneously to changes in current I. That is, it rises rapidly with the rising edge of current I, shifts at a certain level, and then disappears with the falling edge of current I. The second component, the polarization voltage component Vp, responds to changes in current I with a delayed change. That is, it rises gradually after the rising edge of current I and gradually decreases after the falling edge of current I. The third component, the OCV variation component ΔOCV, represents the change in the battery's OCV, equivalent to the difference between the OCV value before charging begins (OCV1) and the OCV value after charging begins (OCV2). This OCV variation component ΔOCV corresponds to the change in the battery's state of charge based on the amount of charge / discharge.

[0040] Figure 4 This is a diagram illustrating an example of the equivalent circuit model of battery (cell) 10. Figure 4In this context, Ro represents the DC resistance component of the resistive element. The state-of-charge estimation unit 1202 multiplies the DC resistance component Ro by the current I to calculate the DC voltage component I×Ro. Rp represents the polarization resistance component of the resistive element, and Cp represents the polarization capacity component of the capacitor element connected in parallel with the resistive element. RpCp is connected in series with Ro. The battery voltage (CCV) is obtained by adding the polarization voltage component Vp, the DC resistance component Ro, and the open-circuit voltage OCV. The state-of-charge estimation unit 1202 calculates the polarization voltage component Vp based on the current I and the charging / discharging time t.

[0041] Vp=I×Rp×(1-exp[-t / RpCp]) from Figure 4 As shown in the equivalent circuit, the polarization voltage component Vp varies exponentially with respect to the time constant RpCp. The primary cause of polarization, which generates internal resistance in the battery, is the distribution of lithium concentration within and on the surface of the electrode active material particles. Specifically, the state of polarization occurring and charge accumulating in Cp in the equivalent circuit corresponds to the state during charging where lithium accumulates on the surface of the negative electrode active material particles, creating a lithium concentration difference between the surface and interior. The amount of charge accumulated in Cp corresponds to the difference between the average SOC (first state of charge) and the local SOC (second state of charge) on the surface of the electrode active material particles. The average SOC compensates for variations in SOC at different locations or localities within the battery, representing its average state of charge. When all parts of the battery are uniformly charged or discharged, the average SOC and the local SOC are the same value. When the state of charge differs at different locations or localities within the battery, the average SOC shows a value different from the average value of the local SOC.

[0042] The permissible current calculated using the prior art in Patent Document 1 may result in the battery voltage deviating from the upper and lower limits. This is because lithium ion concentration distribution occurs inside the electrodes during charging and discharging, leading to inconsistent State of Charge (SOC). However, existing SOC estimation methods based on current accumulation capacity cannot reflect this SOC distribution.

[0043] To calculate the maximum current while keeping the battery voltage within its upper or lower limits, the battery control device utilizes multiple parameters related to the battery's internal state, such as the open-circuit voltage (OCV) and internal resistance. In energy storage devices, especially those designed for moving bodies that always carry irregular currents and for stabilizing interconnected systems, in addition to considering the effect of internal resistance (DC resistance) that causes voltage changes when current flows through the battery momentarily, it is also necessary to consider the effect of internal resistance (polarization resistance) that causes voltage changes when current continues to flow.

[0044] In calculating the allowable current of the lithium-ion battery, the allowable current calculation unit 1204 does not utilize the average SOC, but rather a local SOC that incorporates the influence of lithium-ion distribution. Lithium accumulation affects the charge amount of the capacitor elements. Therefore, the allowable current calculation unit 1204 can calculate the local SOC affected by lithium-ion distribution based on the average SOC and the charge amount of the capacitor elements. The charge accumulated in Cp corresponds to the difference between the average SOC and the local SOC. The allowable current calculation unit 1204 can calculate this difference based on the charge amount of the capacitor elements, and then subtract this difference from the average SOC or add the difference to the average SOC to calculate the local SOC. To transform the charge amount of the capacitor elements into this difference, for example, the charge amount can be multiplied by a specific transformation coefficient obtained through experiments or computer simulations.

[0045] The state of charge estimation unit 1202 calculates the average state of charge (SOC) of the battery, for example, based on the charge / discharge capacity ΔQ obtained by integrating the current I, according to the relationship between the charge / discharge capacity and SOC. Alternatively, the state of charge estimation unit 1202 can also calculate the average SOC of the battery based on the battery's open-circuit volume (OCV) obtained by analyzing the battery's open-circuit volume (CCV) using an equivalent circuit model. Specifically, the state of charge estimation unit 1202 estimates the battery's state of charge using the battery's temperature, current, voltage detected by the sensor group 1400, and the battery's data table 1205. Alternatively, the state of charge estimation unit 1202 can also calculate the average SOC of the battery by combining the average SOC obtained from integrating the current I with the average SOC obtained from analyzing the battery's CCV using a weighted average method.

[0046] Parameters such as DC resistance and polarization resistance vary depending on the battery's state of charge (SOC) and temperature. Therefore, the battery controller 12 provides a data table 1205 or a function that maps SOC and temperature to the values ​​of parameters such as DC resistance and polarization resistance. Furthermore, the battery controller 12 estimates the SOC based on measured current, voltage, and temperature information, and determines the parameter values ​​based on the SOC using the data table 1205 or the function.

[0047] like Figure 5 As shown, battery datasheet 1205 stores the relationships between the DC resistance component Ro (Ω), polarization resistance Rp (Ω), and polarization capacity Cp (F) and temperature T (°C), SOC (%), and OCV (V). Battery datasheet 1205 records data at SOCs of SOC1 to SOC2. MAt temperatures T (degrees Celsius) ranging from T_1 to T_L, the OCV components V_1,1 to V_M,L, DC resistance components Ro_1,1 to Ro_M,L, polarization resistance Rp_1,1 to Rp_M,L, and polarization capacity Cp_1,1 to Cp_M,L are given. Battery datasheet 1205 is one of the data structures containing battery performance parameters. The DC resistance component Ro (Ω), polarization resistance Rp (Ω), and polarization capacity Cp (F) of the equivalent circuit model are examples of battery performance parameters.

[0048] The relationships between OCV, DC resistance, polarization resistance, polarization capacitance, and temperature and SOC can also be defined as functions (graphs) of a data structure. For example, Figure 6A It is a graph of SOC versus DC resistance component Ro at 25 degrees Celsius. Figure 6B This is a graph of SOC versus polarization resistance Rp at 25 degrees Celsius. A similar graph can be plotted for OCV and polarization capacitance Cp. Temperatures outside 25 degrees Celsius are defined in the same way.

[0049] The parameter calculation unit 1203 calculates the current parameter values ​​of the DC resistance component Ro (Ω), polarization resistance Rp (Ω), and polarization capacity Cp (F) based on the battery degradation state estimated by the degradation state estimation unit 1201. The parameter calculation unit 1203 updates the parameter values ​​from the battery's initial state to the calculated parameter values ​​and records them in the battery data table 1205. For details regarding the parameter calculation, this application references Japanese Patent Application Publication No. 2020-134279.

[0050] The allowable current calculation unit 1204 calculates the battery's internal resistance and allowable current based on the current battery SOC and temperature, and refers to the battery's DC resistance, polarization resistance, and polarization capacity stored in the battery data sheet 1205. The allowable current calculation is part of a safety function to prevent battery overvoltage; by limiting the current to a reference value, it maintains the safety of the battery control device 1.

[0051] Figure 7 This is an example of a flowchart illustrating the control operation of the allowable current calculation unit 1204 during discharge. The allowable current calculation unit 1204 obtains the OCV, DC resistance, polarization resistance, and polarization capacity based on the average SOC from the state of charge estimation unit 1202 and the temperature T from the sensor group 1400, referring to the battery data sheet 1205. The allowable current calculation unit 1204 can calculate the allowable current by dividing the absolute value of the difference between OCV and the limiting voltage (lower limit voltage or upper limit voltage) by the internal resistance. The allowable current calculation unit 1204 calculates candidates for the discharge allowable current (candidate allowable current Imax_m) (S700).

[0052] Candidates for the allowable discharge current can be calculated, for example, using the following formula.

[0053] Imax_1 = (|OCV - Vmin|) / R Vmin is the lower limit voltage, and R is the internal resistance of the battery.

[0054] The internal resistance R of a battery can be calculated, for example, using the following formula.

[0055] R = Ro + Rp (1-e -t / RpCp ) t is time (seconds).

[0056] Next, the allowable current calculation unit 1204 calculates the average SOC after n seconds based on the discharge charge ΔQ obtained by integrating the allowable current (Imax_m) over the discharge time (n seconds) and the SOC at the start of discharge (S701). Next, the allowable current calculation unit 1204 calculates the charge of the capacitor element. The allowable current calculation unit 1204 multiplies the charge Q of the capacitor element by the specific transformation coefficient described above, and calculates the difference SOC (ΔSOC), which is the difference between the average SOC and the local SOC (S702). The allowable current calculation unit 1204 calculates the local SOC (effective SOC) by subtracting the difference SOC from the average SOC.

[0057] The current calculation unit 1204 extracts Ro, Rp, and Cp based on the local SOC and temperature, referring to the battery data sheet 1205. Then, the current calculation unit 1204 substitutes the extracted values ​​into the formula for the internal resistance R to calculate the battery's internal resistance R after n seconds (S703). Next, the current calculation unit 1204 calculates (Imax_1) × R to predict the battery voltage after n seconds (S704).

[0058] Next, the allowable current calculation unit 1204 compares the battery voltage after n seconds (S704) with the lower limit voltage to determine whether the battery voltage has deviated from the lower limit voltage (S705). If the allowable current calculation unit 1204 rejects the determination, that is, determines that the battery voltage falls within the lower limit voltage range, it sends the candidate allowable current (S700) as the determined allowable current to the battery controller 12 for charge / discharge execution function (S707), and ends the flowchart. On the other hand, if the allowable current calculation unit 1204 affirms the determination, that is, determines that the battery voltage has deviated from the lower limit voltage, it multiplies the candidate allowable current by a pre-defined correction factor to slightly increase it, updates the candidate allowable current (k) (S706), returns to step S701, calculates the battery voltage based on the updated candidate allowable current (k), and repeatedly determines whether it has deviated from the upper or lower limit voltage. By repeatedly executing such a control flow, the allowable current calculation unit 1204 can detect an allowable current that takes into account the Li concentration distribution on the surface and inside of the electrode active material particles and avoids deviating from the limiting voltage (upper limit voltage or lower limit voltage) of the battery voltage. Furthermore, Figure 7 Although an example flowchart of the control operation of the allowable current calculation unit 1204 during discharge has been described, it can be applied to the control operation during charging. In this case, the upper limit voltage is used instead of the lower limit voltage, and the correction factor is changed to a factor that can slightly reduce the candidate allowable current.

[0059] Here, use Figure 8 , 9 right Figure 7 The control actions will be further explained. Figure 8 It is based on the average SOC operational internal resistance and does not perform based on Figure 7 An example of optimized allowable current. Figure 8 The relationship between SOC (average SOC, local SOC) and battery voltage relative to the discharge current is shown. By utilizing these characteristics, the current calculation unit 1204 can predict the shifts in SOC and voltage. Figure 8 In the diagram, T1 represents the current time point and shows the changes in SOC and battery voltage up to n seconds later. (A) shows the aforementioned Imax_1 (allowed discharge current) input to the battery for n seconds starting from T1. (B) shows the situation during this period where lithium accumulates on the surface of the electrode active material particles, causing the local SOC to deviate from the average SOC (ΔL1). When the local SOC enters a region of high resistance due to the continuous accumulation of lithium, the voltage drop difference ΔV increases, and the battery voltage exceeds the lower limit voltage (V). Limit ).

[0060] Figure 9 The following scenario illustrates that the current calculation unit 1204 is allowed to perform optimization processing on the allowed current value. Figure 7 By determining the allowable current Imax, which is ultimately determined as the allowable current, as shown in (B), the SOC distribution (ΔL2 < ΔL1) is suppressed, thereby enabling the battery voltage to be suppressed to a state where the voltage does not have an inflection point. As a result, it is possible to prevent the battery voltage from deviating from the lower limit voltage (V). Limit ).

[0061] Figure 10 An example display of the indicator 900 of the battery control device 1 is shown. It can be displayed on a mobile terminal device's screen or transmitted to a host system. In addition to general values ​​such as voltage, temperature, current, SOC, SOHR, and SOHQ, the battery control device 1 also outputs the local SOC and allowable current values ​​specific to this invention. Therefore, the user of the battery control device 1 can obtain the allowable current, which has been predicted with high accuracy.

[0062] Alternatively, equivalent circuits other than those shown in this embodiment can be used. For example, circuits such as... Figure 11A The equivalent circuit shown has RC parallel sections representing the positive and negative terminals, respectively. In this case, instead of battery datasheet 1205, a positive terminal datasheet and a negative terminal datasheet with the same structure are provided. Alternatively, for example, a... Figure 11B The equivalent circuit shown can simulate the current distribution 1500 and the SOC distribution 1502 along the electrode depth direction. In this case, the present invention can be applied by setting the average SOC and local SOC for each RC parallel circuit along the depth direction.

[0063] According to the embodiments described above, the first disclosure relates to a battery control device 1 that controls the charging and discharging of a single battery cell 10. The device is characterized by comprising: a detection unit (sensor group) 1400 for detecting the battery state; a state of charge estimation unit 1202 for estimating the battery's state of charge (SOC) based on detection data from the detection unit; and an allowable current calculation unit 1204 for calculating the allowable current for charging and discharging the battery based on an equivalent circuit model of the battery and a battery data sheet 1205, wherein the equivalent circuit model (… Figure 4The battery datasheet 1205 associates the resistance and capacitance elements, battery state, and charging state. The allowable current calculation unit 1204 uses the SOC estimated by the charging state estimation unit 1202 as the first SOC (average SOC), calculates the second SOC (local SOC) based on the average SOC and the charge amount of the capacitance elements, and calculates the allowable current based on the local SOC and detection data with reference to the battery datasheet. According to the first disclosure, a battery control device is provided that uses an equivalent circuit, has a low computational load, and can predict the sharp rise or fall of battery voltage when the battery is charged and discharged with a large current, thus enabling the calculation of the allowable current with high accuracy.

[0064] Furthermore, the second disclosure is characterized in that, based on the first disclosure, the charge quantity of the capacitor element includes the influence of lithium accumulated on the surface of the electrode active material particles. According to the second disclosure, the influence caused by lithium accumulation can be eliminated, and the allowable current can be determined with high accuracy.

[0065] Furthermore, the third disclosure is characterized in that, based on the first or second disclosure, the current calculation unit 1204 is allowed to multiply the charge of the capacitor element by a predetermined coefficient, and then subtract the calculation result of multiplying the charge of the capacitor element by the predetermined coefficient from the average SOC to obtain the local SOC. According to the third disclosure, the local SOC can be easily obtained.

[0066] Furthermore, the fourth disclosure is characterized in that, based on any one of the first to third disclosures, the allowable current calculation unit 1204 calculates the internal resistance of the battery cell 10 with reference to the battery data sheet, and calculates the allowable current based on the difference between the battery's open-circuit voltage and the limiting voltage (upper limit voltage or lower limit voltage) and the internal resistance.

[0067] Furthermore, the fifth disclosure is characterized in that, based on any one of the first to fourth disclosures, the allowable current calculation unit 1204, when determining the allowable current, sets a candidate allowable current as a candidate for determining the allowable current, calculates the battery voltage based on the candidate allowable current, compares the battery voltage with the limiting voltage, and when the battery voltage deviates from the range of the limiting voltage, corrects the candidate allowable current; when the battery voltage based on the corrected candidate allowable current falls within the range of the limiting voltage, the corrected candidate allowable current is used as the determined allowable current. Thus, it is possible to predict the allowable current with high accuracy and to reliably prevent the battery voltage from deviating from the range of the limiting voltage.

[0068] The sixth disclosure relates to a battery control method for controlling the charging and discharging of a battery. The method is characterized by detecting the battery state; estimating the charging state of the battery based on the detection data; and calculating an allowable current for charging and discharging the battery based on an equivalent circuit model and a data structure. The equivalent circuit model includes resistive and capacitive elements, and the data structure associates the resistive elements, capacitive elements, battery state, and charging state. The calculation of the allowable current involves taking the estimated charging state as a first charging state, calculating a second charging state based on the first charging state and the charge quantity of the capacitive elements, and calculating the allowable current based on the second charging state and the detection data detected by the detection unit, referring to the data structure.

[0069] This invention is not limited to the configuration described in the embodiments, and can be appropriately configured based on the content described in the claims. The above-described embodiments are examples for implementing this invention. When implementing this invention, only a portion of the configuration of the embodiments may be implemented. When implementing this invention, configurations not described in the embodiments may also be added and implemented. When implementing this invention, a portion of the configuration of the embodiments may be replaced with a configuration not described in the embodiments. Modules, devices, and units may also be configured as combined electronic circuits.

[0070] Explanation of reference numerals in the attached figures 1: Battery control device 2: Inverter 3: Load, 4: Host controller 10: Battery cells, 11: Battery module 12: Battery controller 13: Relay, 14: Current sensor 15: Voltage sensor 16: Leakage current sensor 17: Temperature sensor 18: Circuit breaker 100: Battery system 121: CPU 122: Storage Department 1201: Deterioration State Prediction Section 1202: Charging State Estimation Unit 1203: Parameter Calculation Department 1204: Permissible current calculation unit, 1205: Battery Data Sheet.

Claims

1. A battery control device for controlling the charging and discharging of a battery, wherein, have: The testing department checks the battery status. The charging state estimation unit estimates the charging state of the battery based on the detection data from the detection unit. as well as The allowable current calculation unit calculates the allowable current for charging and discharging the battery based on the equivalent circuit model and data structure of the battery. The equivalent circuit model includes resistive elements and capacitive elements, and the data structure associates the resistive elements, the capacitive elements, the battery state, and the charging state. The allowable current calculation unit takes the charging state estimated by the charging state estimation unit as the first charging state, calculates the second charging state based on the first charging state and the charge of the capacitor element, and calculates the allowable current based on the second charging state and the detection data with reference to the data structure.

2. The battery control device according to claim 1, wherein, The charge of the capacitor element includes the effect of lithium accumulated on the surface of the electrode active material particles.

3. The battery control device according to claim 1, wherein, The permissible current calculation unit multiplies the charge of the capacitor element by a predetermined coefficient, and then subtracts the calculation result of the charge of the capacitor element multiplied by the predetermined coefficient from the first charging state to obtain the second charging state.

4. The battery control device according to claim 1, wherein, The allowable current calculation unit calculates the internal resistance of the battery by referring to the data structure. The allowable current is determined based on the difference between the open-circuit voltage and the limiting voltage of the battery, as well as the internal resistance.

5. The battery control device according to claim 4, wherein, When determining the allowable current, the allowable current calculation unit sets a candidate allowable current as a candidate for determining the allowable current. The battery voltage is calculated based on the candidate allowable current, and then compared with the limiting voltage. When the battery voltage deviates from the range of the limit voltage, the candidate allowable current is adjusted. When the battery voltage based on the modified candidate allowable current falls within the range of the limiting voltage, the modified candidate allowable current is used as the determined allowable current.

6. A battery control method for controlling the charging and discharging of a battery, wherein, Check battery status; The charging state of the battery is estimated based on the detection data; as well as Based on the equivalent circuit model and data structure of the battery, the allowable current for charging and discharging the battery is calculated. The equivalent circuit model includes resistive and capacitive elements, and the data structure associates the resistive element, the capacitive element, the battery state, and the charging state. The calculation of the allowable current is as follows: The estimated charging state is taken as the first charging state, and the second charging state is determined based on the first charging state and the charge quantity of the capacitor element. Based on the second charging state and the detection data, the allowable current is calculated using the data structure.

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