Battery control device and battery control method

Abstract

This battery control device comprises: a voltage detecting unit for detecting an open circuit voltage of a secondary battery when the secondary battery is discharged after having been charged; and a control unit for estimating an amount of decrease in the open circuit voltage due to a memory effect, on the basis of a charge / discharge history of the secondary battery.

Description

Battery control device and battery control method

[0001] The present invention relates to an apparatus and method for controlling a secondary battery.

[0002] Nickel-metal hydride batteries and other batteries have been widely used as inexpensive and safe secondary batteries. In recent years, zinc secondary batteries, which offer high energy density and high safety, have been developed as an alternative to conventional lithium-ion batteries. These secondary batteries have a larger memory effect than lithium-ion batteries, and therefore, when they are repeatedly charged and discharged at a depth of discharge greater than 0%, a decrease in battery voltage occurs due to the memory effect.

[0003] Regarding suppression of the memory effect, for example, a technique disclosed in Patent Document 1 is known. ６ Octahedron and PO ４ H, which has a tetrahedral crystal structure ２ NiP ２ O ７ A nickel-metal hydride battery is disclosed in which the occurrence of memory effect is suppressed by using the above as a positive electrode active material.

[0004] Japanese Patent Application Publication No. 2017-41393

[0005] The nickel-metal hydride battery described in Patent Document 1 can suppress the occurrence of the memory effect and suppress the decrease in battery voltage, but it cannot completely prevent the decrease in battery voltage, which makes it difficult to accurately estimate the depth of discharge from the battery voltage, which may lead to a decrease in the control accuracy of the secondary battery.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a technique that can control a secondary battery with high precision even when a memory effect occurs.

[0007] A battery control device according to the present invention includes a voltage detection unit that detects the open circuit voltage of a secondary battery when the secondary battery is discharged after being charged, and a control unit that estimates the amount of decrease in the open circuit voltage due to the memory effect based on the charge / discharge history of the secondary battery. A battery control method according to the present invention stores the charge / discharge history of the secondary battery, detects the open circuit voltage of the secondary battery when the secondary battery is discharged after being charged, estimates the amount of decrease in the open circuit voltage due to the memory effect based on the charge / discharge history of the secondary battery, and controls the secondary battery based on the estimated amount of decrease in the open circuit voltage.

[0008] According to the present invention, it is possible to control a secondary battery with high precision even when a memory effect occurs.

[0009] The present invention relates to a battery control device and a method for calculating an OCV of a battery.

[0010] Fig. 1 is a schematic diagram of a battery control device according to one embodiment of the present invention. The battery control device 1 shown in Fig. 1 is connected to a battery 2 in order to control the battery 2. The battery 2 is a rechargeable secondary battery, and may be, for example, a zinc secondary battery using nickel hydroxide as the positive electrode and zinc as the negative electrode, or a nickel-metal hydride battery. The battery 2 may be a single cell, or a battery module made up of a plurality of single cells.

[0011] In this embodiment, a secondary battery having a memory effect is used as the battery 2. The memory effect is a phenomenon in which, when a secondary battery is repeatedly charged and discharged at an intermediate depth of discharge between its maximum and minimum values, i.e., when a so-called top-up charge is performed, the battery voltage drops sharply during discharge to near the battery voltage at the end of the previous discharge. This memory effect is known to occur significantly in secondary batteries such as zinc secondary batteries and nickel-metal hydride batteries that use nickel in the positive electrode.

[0012] Even if a memory effect occurs in the battery 2, the battery control device 1 of this embodiment estimates the amount of battery voltage drop due to the memory effect using a method described below, and corrects the battery voltage using the estimated result, thereby controlling the battery 2 with high precision. As shown in Figure 1, the battery control device 1 of this embodiment is configured to include a control unit 10, a voltage detection unit 11, a current detection unit 12, a battery temperature detection unit 13, and a memory unit 14.

[0013] The voltage detection unit 11 detects the voltage between the positive and negative electrodes of the battery 2 as the battery voltage and outputs the detection result to the control unit 10. The current detection unit 12 detects the charge / discharge current flowing through the battery 2 and outputs the detection result to the control unit 10. The battery temperature detection unit 13 detects the surface temperature of the battery 2 or the temperature of the members or space near the battery 2 as the battery temperature and outputs the detection result to the control unit 10.

[0014] The control unit 10 has functional blocks of a charge / discharge amount calculation unit 101, a ΔOCV estimation unit 102, and a battery management unit 103. The control unit 10 is configured using, for example, a microcomputer, and can realize these functional blocks by executing a predetermined program. Note that the control unit 10 may be configured using a logic circuit such as an FPGA (Field Programmable Gate Array) instead of a microcomputer.

[0015] The charge / discharge amount calculation unit 101 calculates the charge / discharge amount of the battery 2 based on the detection result of the charge / discharge current input from the current detection unit 12. The ΔOCV estimation unit 102 estimates a ΔOCV that indicates the amount of decrease in the open circuit voltage (OCV) of the battery 2 due to the memory effect based on the charge / discharge amount calculated by the charge / discharge amount calculation unit 101. The specific contents of these processes will be described later.

[0016] The battery management unit 103 controls and manages the battery 2. For example, it controls the charging and discharging of the battery 2 based on external charging and discharging commands and calculates the state of charge (SOC) of the battery 2. Specifically, the battery management unit 103 corrects the OCV detection result input from the voltage detection unit 11 when the battery 2 is not in a charging or discharging state based on the ΔOCV value estimated by the ΔOCV estimation unit 102, thereby calculating the original OCV value of the battery 2 when no memory effect occurs. Then, based on the corrected OCV value and the detection results of the charging and discharging current and the battery temperature input from the current detection unit 12 and the battery temperature detection unit 13, the battery management unit 103 calculates the SOC, which represents the state of charge of the battery 2 as a value between 0 and 100%, and notifies the external device of the calculation result. Furthermore, at this time, the battery 2 may be controlled for charging and discharging as needed based on the calculated SOC value. For example, when the SOC value approaches 0%, the battery 2 may be forcibly charged regardless of the charging or discharging command. Alternatively, the battery 2 may be controlled and managed in any other manner.

[0017] The storage unit 14 is configured using a storage medium such as a RAM or a flash memory, and stores various information used in the processing of the control unit 10. For example, the charge / discharge amount of the battery 2 calculated by the charge / discharge amount calculation unit 101, the ΔOCV estimated by the ΔOCV estimation unit 102, and the like are stored in the storage unit 14. The control unit 10 can implement the functional blocks of the charge / discharge amount calculation unit 101, the ΔOCV estimation unit 102, and the battery management unit 103 described above by reading and writing this information to the storage unit 14.

[0018] Next, a method for estimating ΔOCV in the battery control device 1 will be described with reference to FIG. 2 . FIG. 2 is a diagram showing an overview of a battery voltage drop due to the memory effect. In FIG. 2 , a graph 21 shown by a solid line shows an example of the relationship between the SOC and discharge voltage of the battery 2 when the memory effect does not occur. Furthermore, a graph 22 shown by a dashed line shows an example of the relationship between the SOC and discharge voltage of the battery 2 when the memory effect occurs. In these graphs 21 and 22, the horizontal axis represents the SOC value [%] of the battery 2, and the vertical axis represents the discharge voltage [V] of the battery 2.

[0019] In Figure 2, the SOC value of battery 2 at the end of the previous discharge is indicated by X. When the SOC value approaches X during discharge of battery 2, a ΔOCV occurs due to the influence of the memory effect, and the discharge voltage in graph 22 gradually decreases compared to graph 21. When the SOC value falls below X, the ΔOCV value becomes a constant value a, and when the discharge progresses further and the SOC value falls below a predetermined value L, the discharge voltage decreases to a discharge end voltage V Ｌ It can be seen that it decreases sharply towards

[0020] Here, if the SOC value at which ΔOCV begins to occur due to the influence of the memory effect is X+α, then graph 22 can be divided into the following four regions according to the value of SOC based on the change in discharge voltage. Region R0 (X+α≦SOC≦100) A region where there is no influence of the memory effect and ΔOCV=0 Region R1 (X≦SOC≦X+α) A region where the value of ΔOCV gradually increases according to the function F(x) due to the influence of the memory effect Region R2 (L≦SOC≦X) A region where the discharge voltage is approximately constant and the value of ΔOCV becomes a constant value a due to the influence of the memory effect Region R3 (0≦SOC≦L) A region where the discharge voltage becomes equal to or exceeds the discharge end voltage V while the value of ΔOCV remains constant at the constant value a. Ｌ The region where the value drops sharply toward

[0021] The values ​​of the above functions F(x) and a quantitatively indicate the change in the crystal structure due to the memory effect. These values ​​change depending on the number of times the battery 2 is repeatedly charged and discharged in the intermediate depth state. In addition, in the region R3, when the discharge voltage reaches the discharge cut-off voltage V Ｌ The difference b between the SOCs of the graphs 21 and 22 when the battery 2 is in the above range is a very small value compared to the range of SOCs that the battery 2 can have, and is therefore ignored in this embodiment.

[0022] The battery control device 1 of this embodiment determines which of the above regions R0 to R3 the current charge / discharge state of the battery 2 belongs to based on the SOC value of the battery 2, and switches the ΔOCV estimation method depending on the determination result. This makes it possible to accurately estimate the ΔOCV value even if the charge / discharge state of the battery 2 changes.

[0023] In the above description, the method for estimating ΔOCV is switched depending on the value of the SOC of the battery 2, but similar processing can be performed using the remaining capacity of the battery 2. In this case, the value of the remaining capacity of the battery 2 at the end of the previous discharge can be used instead of X, and the value of the remaining capacity at which ΔOCV begins to occur due to the influence of the memory effect can be used instead of X+α.

[0024] 3 is a flowchart showing the flow of processing in a battery control device according to one embodiment of the present invention. The battery control device 1 manages the battery 2 by having the control unit 10 execute the processing shown in the flowchart in FIG. 3 at predetermined processing intervals.

[0025] In step S10, the control unit 10 acquires the voltage value and current value of the battery 2 from the voltage detection unit 11 and current detection unit 12, respectively.

[0026] In step S20, the control unit 10 determines whether the battery 2 is being charged or discharged based on the current value acquired in step S10. If the current value is not 0, it determines that the battery 2 is being charged or discharged and proceeds to step S30, but if the current value is 0, it determines that the battery 2 is neither being charged nor discharged and proceeds to step S130.

[0027] In step S30, the control unit 10 calculates an integrated current value for the period from the previous processing to the current processing by the charge / discharge amount calculation unit 101. Here, for example, the integrated current value can be calculated by multiplying the current value acquired in step S10 by a predetermined processing cycle. Alternatively, the integrated current value may be calculated by acquiring a current value multiple times at predetermined sampling cycles during one processing period, multiplying each current value by the sampling cycle, and adding up the current values. Note that in this case, it is preferable to distinguish the integrated current value on the discharge side from the integrated current value on the charge side, for example, by making the sign of the integrated current value negative on the discharge side and positive on the charge side.

[0028] In step S40, the control unit 10 updates the remaining capacity of the battery 2 based on the integrated current value calculated in step S30. Here, the control unit 10 adds or subtracts the integrated current value calculated in step S30 to or from the remaining capacity determined in the previous process. This updates the remaining capacity of the battery 2 to the latest value, reflecting the integrated current value from the previous process to the current process.

[0029] In step S50, the control unit 10 determines whether the charge / discharge state of the battery 2 has been switched from discharge to charge. Here, for example, the control unit 10 compares the sign of the current value acquired in the previous process with the sign of the current value acquired in the current process. If the sign of the previous current value is negative, indicating discharge, and the sign of the current current value is positive, indicating charge, it is determined that the charge / discharge state of the battery 2 has been switched from discharge to charge, and the process proceeds to step S60. Note that the switch from discharge to charge here also includes a switch from discharge to charge via a charge / discharge stop state (a state where the current value is zero). On the other hand, if the sign of the previous current value is not negative or the sign of the current current value is not positive, it is determined that the charge / discharge state of the battery 2 has not been switched from discharge to charge, and the process proceeds to step S90.

[0030] In step S60, the control unit 10 stores the remaining capacity of the battery 2 updated in the immediately preceding step S40 as the remaining capacity at the end of discharge in the memory unit 14. The remaining capacity at the end of discharge stored here is used in the processing of step S110, which will be described later.

[0031] In step S70, the control unit 10 determines whether the battery 2 has been discharged to the discharge cut-off voltage. Here, for example, the voltage value acquired in step S10 in the previous process is equal to the discharge cut-off voltage V Ｌ If they match, it is determined that the battery 2 has been discharged to the discharge end voltage, and the process proceeds to step S80. On the other hand, if they do not match, it is determined that the battery 2 has not been discharged to the discharge end voltage, and the process shown in the flowchart in Figure 3 ends.

[0032] In step S80, the control unit 10 resets the number of charge / discharge cycles Nc of the battery 2 to an initial value of 0. The number of charge / discharge cycles Nc of the battery 2 is stored in the memory unit 14, and is counted up by 1 each time the charge / discharge state of the battery 2 is switched from charge to discharge. After resetting the number of charge / discharge cycles Nc of the battery 2 to 0 in step S80, the control unit 10 ends the processing shown in the flowchart of FIG. 3.

[0033] In step S90, the control unit 10 determines whether the charge / discharge state of the battery 2 has switched from charge to discharge. Here, similar to step S50 described above, the control unit 10 compares the sign of the current value acquired in the previous processing with the sign of the current value acquired in the current processing. If the sign of the previous current value is positive, indicating charge, and the sign of the current current value is negative, indicating discharge, it is determined that the charge / discharge state of the battery 2 has switched from charge to discharge, and the process proceeds to step S100. Note that the term "switching from charge to discharge" here also includes switching from charge to discharge via a charge / discharge stop state (a state where the current value is zero). On the other hand, if the sign of the previous current value is not positive or the sign of the current current value is not negative, it is determined that the charge / discharge state of the battery 2 has not switched from charge to discharge, and the process shown in the flowchart of FIG. 3 is terminated. In this case, the battery 2 is continuing to be charged or discharged from the previous processing.

[0034] In step S100, the control unit 10 stores the remaining capacity of the battery 2 updated in the immediately preceding step S40 in the storage unit 14 as the remaining capacity at the end of charging.

[0035] In step S110, the control unit 10 calculates the charge amount c of the battery 2 due to the current charge using the charge / discharge amount calculation unit 101. Here, the control unit 10 calculates the difference between the remaining capacity at the end of the most recent charge stored in the storage unit 14 in step S100 and the remaining capacity at the end of the most recent discharge stored in the storage unit 14 in step S60, and sets this as the charge amount c of the battery 2. The calculated charge amount c is then stored in the storage unit 14.

[0036] In step S120, the control unit 10 counts up by one the number of charge / discharge cycles Nc of the battery 2 stored in the storage unit 14. This counts up by one the number of charge / discharge cycles Nc of the battery 2 each time the charge / discharge state of the battery 2 is switched from charging to discharging. After storing the counted-up number of charge / discharge cycles Nc in the storage unit 14 and updating the number of charge / discharge cycles Nc, the control unit 10 ends the processing shown in the flowchart of FIG. 3.

[0037] In step S130, the control unit 10 performs an OCV calculation process using the charge / discharge amount calculation unit 101, the ΔOCV estimation unit 102, and the battery management unit 103. In this OCV calculation process, the ΔOCV value is estimated using the method described above with reference to FIG. 2, and the voltage value acquired in step S10 when the battery 2 is neither charging nor discharging, i.e., the OCV value of the battery 2, is corrected based on the estimated ΔOCV value. This eliminates the influence of the memory effect from the OCV value, and determines an OCV value corresponding to the remaining capacity of the battery 2. Details of the OCV calculation process performed in step S130 will be described later with reference to the flowchart of FIG. 4.

[0038] In step S140, the control unit 10 calculates the remaining capacity of the battery 2 using the battery management unit 103 based on the corrected OCV calculated by the OCV calculation process in step S130. Here, the remaining capacity corresponding to the corrected OCV can be calculated using, for example, a predetermined relational expression between the OCV and the remaining capacity. Note that the relational expression between the OCV and the remaining capacity generally changes depending on operating conditions such as the temperature of the battery 2 and the magnitude of the current immediately before the OCV is detected. Therefore, it is preferable to use different relational expressions between the OCV and the remaining capacity used in the process of step S140 based on the battery temperature acquired from the battery temperature detection unit 13, the immediately preceding current value acquired from the current detection unit 12, etc. After calculating the remaining capacity based on the corrected OCV in this manner, the control unit 10 ends the process shown in the flowchart of FIG. 3.

[0039] FIG. 4 is a flowchart showing the details of the OCV calculation process executed in step S130 of FIG.

[0040] In step S210, the charge / discharge amount calculation unit 101 detects the OCV of the battery 2. Here, the OCV of the battery 2 can be detected from the voltage value acquired from the voltage detection unit 11 in step S10 of FIG.

[0041] In step S220, the charge / discharge amount calculation unit 101 calculates the discharge amount d of the battery 2 due to the current discharge. Here, the difference between the remaining capacity at the end of the most recent charge stored in the storage unit 14 in step S100 of FIG. 3 and the most recent remaining capacity updated in step S40 is calculated, and this is set as the discharge amount d of the battery 2. The calculated discharge amount d is then stored in the storage unit 14.

[0042] In step S230, the ΔOCV estimation unit 102 calculates the difference cd between the immediately preceding charge amount c stored in the storage unit 14 in step S110 of FIG. 3 and the discharge amount d calculated in step S220.

[0043] In step S240, the ΔOCV estimation unit 102 determines whether the difference c - d between the charge amount c and the discharge amount d calculated in step S230 is equal to or less than a predetermined threshold t. If the difference c - d is equal to or less than the threshold t, the process proceeds to step S250. If the difference c - d is greater than the threshold t, the process determines that the current charge / discharge state of the battery 2 belongs to region R0 of regions R0 to R3 described in FIG. 2, and proceeds to step S290. The threshold t used in the determination process in step S240 represents the range of the region where the ΔOCV value begins to gradually increase during discharge due to the influence of the memory effect, based on the remaining capacity of the battery 2 at the end of the previous discharge. This corresponds to the SOC value α that defines the boundary between region R0 and region R1.

[0044] The threshold value t can be set in advance in the battery control device 1 based on actual measurement data and simulation results previously obtained using the battery 2. Specifically, experiments have shown that the threshold value t can be set to a value of, for example, 10 to 20 [Ah], preferably about 15 [Ah].

[0045] In step S250, the ΔOCV estimation unit 102 calculates a reference voltage value a based on the value of the number of charge / discharge cycles Nc stored in the storage unit 14. The reference voltage value a corresponds to a ΔOCV value that is constant in the region R2 shown in FIG. 2. Here, the reference voltage value a is calculated, for example, by the following formula (1): a=p×Nc (1)

[0046] In equation (1), p represents a predetermined coefficient, which corresponds to the ratio of the number of charge / discharge cycles Nc to the reference voltage value a. However, if the number of charge / discharge cycles Nc is equal to or greater than a predetermined reference number Nr (e.g., Nr = 15), Nc = Nr, and the reference voltage value a is constant. The coefficient p can be set in advance according to the characteristics of the battery 2, and is, for example, p = 0.0033.

[0047] In step S260, the ΔOCV estimation unit 102 determines whether the difference c - d between the charge amount c and the discharge amount d calculated in step S230 is equal to or greater than 0. If the difference c - d is equal to or greater than 0, it determines that the current charge / discharge state of the battery 2 belongs to region R1, and proceeds to step S270. On the other hand, if the difference c - d is less than 0, it determines that the current charge / discharge state of the battery 2 belongs to region R2 or R3, and proceeds to step S280.

[0048] In step S270, the ΔOCV estimation unit 102 calculates ΔOCV using the following equation (2) based on the difference cd calculated in step S230, the threshold value t used in the determination process in step S240, and the reference voltage value a calculated in step S250: ΔOCV=a×{1−(cd) / t} (2)

[0049] When the current charge / discharge state of the battery 2 belongs to region R1, the value of ΔOCV due to the influence of the memory effect can be calculated by the above formula (2). Note that formula (2) corresponds to the above-mentioned function F(x).

[0050] In step S280, the ΔOCV estimation unit 102 calculates the ΔOCV using the following equation (3) based on the reference voltage value a calculated in step S250. ΔOCV=a (3)

[0051] When the current charge / discharge state of the battery 2 belongs to region R2 or R3, the value of ΔOCV due to the influence of the memory effect can be calculated using the above formula (3). That is, in these regions, the value of ΔOCV can be calculated as a constant value a according to the number of charge / discharge cycles Nc.

[0052] In step S290, the ΔOCV estimation unit 102 calculates the ΔOCV by the following equation (4): ΔOCV=0 (4)

[0053] When the current charge / discharge state of the battery 2 belongs to region R0, the influence of the memory effect does not occur, and therefore the value of ΔOCV can be calculated as 0 using the above formula (4).

[0054] If the ΔOCV value can be calculated in step S270, S280, or S290, the process proceeds to step S300. In step S300, the battery management unit 103 calculates OCV*, which represents the corrected OCV value, by correcting the OCV value detected in step S210 according to the following equation (5) based on the calculated ΔOCV value: OCV*=OCV+ΔOCV (5)

[0055] If the OCV* can be calculated as the corrected OCV in step S300, the control unit 10 ends the OCV calculation process shown in the flowchart of FIG. 4, and proceeds to step S140 in FIG.

[0056] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0057] (1) The battery control device 1 includes a voltage detection unit 11 that detects the open circuit voltage (OCV) of the battery 2, which is a secondary battery, when the battery 2 is discharged after being charged, and a control unit 10 that estimates the amount of OCV decrease ΔOCV due to the memory effect based on the charge / discharge history of the battery 2. This configuration allows the battery 2 to be controlled with high precision even when the memory effect occurs.

[0058] (2) The control unit 10 estimates the ΔOCV based on the charge amount c of the battery 2 due to charging and the discharge amount d of the battery 2 due to discharging. Specifically, the control unit 10 calculates the difference c - d between the charge amount c and the discharge amount d (step S230), and estimates the ΔOCV based on this difference c - d (steps S240 to S290). This allows the ΔOCV to be accurately estimated according to the current charge / discharge state of the battery 2.

[0059] (3) If the difference c - d between the charge amount c and the discharge amount d is equal to or less than a predetermined threshold t (step S240: YES), the control unit 10 estimates the ΔOCV based on the number of charge / discharge cycles Nc of the battery 2. Specifically, if the difference c - d is equal to or greater than 0 and equal to or less than the threshold t (step S260: YES), the control unit 10 estimates the ΔOCV using equation (2) based on the reference voltage value a based on the number of charge / discharge cycles Nc and the ratio of the difference c - d to the threshold t (step S270). If the difference c - d is less than 0 (step S260: NO), the control unit 10 estimates that the ΔOCV is equal to the reference voltage value a using equation (3) (step S280). This allows for accurate estimation of the value of the ΔOCV caused by the memory effect.

[0060] (4) When the number of charge / discharge cycles Nc is equal to or smaller than a predetermined reference number Nr, the control unit 10 sets the reference voltage value a to a value obtained by multiplying the number of charge / discharge cycles Nc by a predetermined coefficient p according to formula (1), and when the number of charge / discharge cycles Nc is greater than the reference number Nr, sets the reference voltage value a to a constant value (step S250). This makes it possible to accurately determine the reference voltage value a required for estimating the ΔOCV, taking into account the degree of influence of the memory effect, which varies depending on the number of charge / discharge cycles Nc.

[0061] (5) If the difference c - d between the charge amount c and the discharge amount d is greater than the threshold value t (step S240: NO), the control unit 10 estimates that the ΔOCV is 0 using equation (4) (step S290). As a result, if there is no influence of the memory effect, the value of ΔOCV can be correctly estimated to be 0.

[0062] (6) The threshold value t is, for example, 10 to 20 [Ah]. In this way, it is possible to accurately represent the range in which the ΔOCV value gradually increases due to the influence of the memory effect.

[0063] (7) The control unit 10 determines whether the voltage of the battery 2 reaches a predetermined discharge end voltage V Ｌ When the battery 2 is discharged until the SOC reaches 0% (step S70: YES), the number of charge / discharge cycles Nc is reset to 0 (step S80). In this way, when a refresh discharge is performed in which the battery 2 is discharged until the SOC reaches 0%, and the decrease in OCV due to the memory effect is thereby eliminated, this can be correctly reflected in the calculation of the reference voltage value a in the subsequent processing, and an accurate estimation result of ΔOCV can be obtained.

[0064] (8) The battery 2 is a zinc secondary battery that uses, for example, nickel hydroxide for the positive electrode and zinc for the negative electrode. This improves the usability of the zinc secondary battery, which has high energy density and high safety.

[0065] The present invention is not limited to the above-described embodiment, and can be implemented using any components without departing from the spirit of the present invention.

[0066] The above-described embodiments and modifications are merely examples, and the present invention is not limited to these details as long as the features of the invention are not impaired. Furthermore, although various embodiments and modifications have been described above, the present invention is not limited to these details. Other aspects that can be considered within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0067] 1: Battery control device 2: Battery 10: Control unit 11: Voltage detection unit 12: Current detection unit 13: Battery temperature detection unit 14: Memory unit 101: Charge / discharge amount calculation unit 102: ΔOCV estimation unit 103: Battery management unit

Claims

1. A battery control device comprising: a voltage detection unit that detects the open circuit voltage of a secondary battery when the secondary battery is discharged after being charged; and a control unit that estimates the amount of decrease in the open circuit voltage due to the memory effect based on the charge / discharge history of the secondary battery.

2. A battery control device according to claim 1, wherein the control unit estimates the amount of decrease in the open circuit voltage based on the amount of charge of the secondary battery due to the charging and the amount of discharge of the secondary battery due to the discharging.

3. A battery control device according to claim 2, wherein the control unit calculates the difference between the charge amount and the discharge amount, and estimates the amount of decrease in the open circuit voltage based on the difference.

4. A battery control device according to claim 3, wherein the control unit estimates the amount of decrease in the open circuit voltage based on the number of times the secondary battery is charged and discharged when the difference is equal to or less than a predetermined threshold value.

5. A battery control device according to claim 4, wherein the control unit, when the difference is equal to or greater than 0 and equal to or less than the threshold value, estimates the amount of decrease in the open circuit voltage based on a reference voltage value based on the number of charge / discharge cycles and the ratio of the difference to the threshold value, and when the difference is less than 0, estimates that the amount of decrease in the open circuit voltage is the reference voltage value.

6. A battery control device according to claim 5, wherein when the difference is equal to or greater than 0 and equal to or less than the threshold value, the control unit estimates the amount of decrease in the open circuit voltage based on the following formula: ΔOCV=a×{1-(c-d) / t} where ΔOCV represents the amount of decrease in the open circuit voltage, a represents the reference voltage value, c represents the amount of charge, d represents the amount of discharge, and t represents the threshold value.

7. A battery control device according to claim 5 or 6, wherein the control unit sets the reference voltage value to a value obtained by multiplying the number of charge / discharge cycles by a predetermined coefficient when the number of charge / discharge cycles is equal to or less than a predetermined reference number, and sets the reference voltage value to a constant value when the number of charge / discharge cycles is greater than the reference number.

8. A battery control device according to any one of claims 4 to 7, wherein the control unit estimates that the amount of decrease in the open circuit voltage is zero when the difference is greater than the threshold value.

9. A battery control device according to any one of claims 4 to 8, wherein the threshold value is 10 to 20 [Ah].

10. A battery control device according to any one of claims 4 to 9, wherein the control unit resets the number of charge / discharge cycles to 0 when the secondary battery is discharged until its voltage reaches a predetermined discharge end voltage.

11. A battery control device according to any one of claims 1 to 10, wherein the secondary battery is a zinc secondary battery using nickel hydroxide as the positive electrode and zinc as the negative electrode.

12. A battery control method comprising: storing a charge / discharge history of a secondary battery; detecting an open circuit voltage of the secondary battery when the secondary battery is discharged after being charged; estimating an amount of decrease in the open circuit voltage due to a memory effect based on the charge / discharge history of the secondary battery; and controlling the secondary battery based on the estimated amount of decrease in the open circuit voltage.

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