Battery pack equalisation device, battery pack equalisation method, and program

Abstract

This battery pack equalisation device (18) for equalising the remaining capacities of a plurality of batteries (b1 to bn) connected in series comprises: an ammeter (16) which measures a discharge current, which is the current supplied from the plurality of batteries (b1 to bn) to a load (4); a transfer circuit which transfers charge between the plurality of batteries (b1 to bn); an equalisation current setting unit (28) which sets the magnitude of an equalisation current, which is the current flowing through the transfer circuit during equalisation, according to the magnitude of the discharge current; and an equalisation processing unit (30) which performs equalisation by controlling the transfer circuit such that the equalisation current of the magnitude set by the equalisation current setting unit (28) flows through the transfer circuit.

Description

Battery pack equalization device, battery pack equalization method, and program

[0001] The present disclosure relates to a battery pack equalization device that equalizes the remaining capacity of each of a plurality of batteries connected in series.

[0002] A technique is known in which charging and discharging between a plurality of batteries (charging and discharging by equalizing current control executed between the plurality of batteries) is used to equalize the SOC (State Of Charge) of a plurality of batteries connected in series.

[0003] For example, Patent Document 1 discloses an adjusting device that sets the accumulated charge in the coil so that the equalization current is minimized in order to suppress power loss due to the equalization current.

[0004] Patent No. 6641665

[0005] However, in the adjusting device described in Patent Document 1, if there is a large variation in the deterioration of the plurality of batteries, the equalizing current to be set becomes large, which may accelerate the deterioration of the plurality of batteries.

[0006] Therefore, an object of the present disclosure is to provide a battery pack equalization device and the like that can suppress further deterioration of a plurality of batteries even when there is a large variation in the deterioration of the plurality of batteries.

[0007] In order to achieve the above goal, an assembled battery equalization device according to one embodiment of the present disclosure is an assembled battery equalization device that performs equalization to make the remaining capacity of each of multiple batteries connected in series the same, and includes an ammeter that measures a discharge current, which is a current supplied from the multiple batteries to a load; a transfer circuit that transfers charge between the multiple batteries; an equalization current setting unit that sets the magnitude of an equalization current, which is a current that flows through the transfer circuit when the equalization is performed, in accordance with the magnitude of the discharge current; and an equalization processing unit that performs the equalization by controlling the transfer circuit so that the equalization current of the magnitude set by the equalization current setting unit flows through the transfer circuit.

[0008] In order to achieve the above object, an assembled battery equalization method according to one embodiment of the present disclosure is a assembled battery equalization method using an assembled battery equalization device that performs equalization to make the remaining capacity of each of a plurality of batteries connected in series the same, the assembled battery equalization device including an ammeter that measures a discharge current that is a current supplied from the plurality of batteries to a load, and a transfer circuit that transfers charge between the plurality of batteries, the assembled battery equalization method including: an equalization current setting step that sets, in accordance with the magnitude of the discharge current, an equalization current that flows through the transfer circuit during the equalization; and an equalization processing step that performs the equalization by controlling the transfer circuit so that the equalization current of the magnitude set in the equalization current setting step flows through the transfer circuit.

[0009] In order to achieve the above object, a program according to one embodiment of the present disclosure is a program for causing a computer to execute the battery pack equalization method.

[0010] The present disclosure provides an assembled battery equalizing device and the like that can suppress further deterioration of a plurality of batteries even when there is a large variation in the deterioration of the plurality of batteries.

[0011] FIG. 1 is a block diagram showing the configuration of a system including a battery pack equalization device. FIG. 2A is a circuit diagram showing a first configuration example of an equalization processing circuit. FIG. 2B is a circuit diagram showing a second configuration example of an equalization processing circuit. FIG. 2C is a circuit diagram showing a third configuration example of an equalization processing circuit. FIG. 3 is a flowchart showing a first operation example performed by the battery pack equalization device shown in FIG. 1. FIG. 4 is a flowchart showing a second operation example performed by the battery pack equalization device shown in FIG. 1. FIG. 5 is a diagram showing the change over time in the voltage of each of a plurality of batteries when the battery pack equalization device performs the operation example shown in FIG. 3 or FIG. 4.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. The numerical values, components, component placement and connection configurations, steps, step order, display examples, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not recited in the independent claims of the present disclosure will be described as optional components. Furthermore, each figure is not necessarily an exact illustration. In each figure, substantially identical components are assigned the same reference numerals, and redundant explanations are omitted or simplified.

[0013] In this specification, the remaining capacity may be the capacity that can be supplied, or the ratio of the capacity that can be supplied to the battery capacity.

[0014] 1 is a block diagram showing the configuration of a system including a battery pack equalization device 18. As shown in FIG. 1, the present disclosure includes a battery pack 2, a load 4, selector switches 6A, 6B, 14A, and 14B, an external power supply 8, an ammeter 16, and the battery pack equalization device 18.

[0015] The battery pack 2 is a battery in which a plurality of batteries b1 to bn (n is an integer of 2 or more) are connected in series. Note that in the battery pack 2, each of the plurality of batteries b1 to bn may be connected in parallel with, for example, a plurality of batteries b11 to b1m (m is an integer of 2 or more). The batteries used for the plurality of batteries b1 to bn are secondary batteries that can be charged and discharged, such as lithium-ion batteries. Note that FIG. 1 shows an example in which the battery pack 2 has four batteries b1 to b4.

[0016] The load 4 is a device that operates using the power supplied by the battery pack 2, and is, for example, an actuator, a motor, or a control device.

[0017] The changeover switches 6A and 6B are switches such as mechanical relays, etc. The changeover switches 6A and 6B are provided on the wiring that electrically connects the battery pack 2 and the load 4.

[0018] The external power supply 8 is a power supply that supplies power to the battery pack 2. The external power supply 8 includes an AC power supply 10 and a converter 12.

[0019] The AC power supply 10 is a power supply that supplies AC power.

[0020] The converter 12 is a charger or the like that includes an AC (Alternating Current) / DC (Direct Current) converter that converts AC power into DC power.

[0021] The changeover switches 14A and 14B are switches such as mechanical relays, etc. The changeover switches 14A and 14B are provided on the wiring that electrically connects the battery pack 2 and the external power supply 8.

[0022] The ammeter 16 measures the current value of the power supplied from the battery pack 2 to the load 4 and the current value of the power supplied from the external power supply 8 to the battery pack 2. In this specification, the current supplied from the battery pack 2 (i.e., the plurality of batteries b1 to bn) to the load 4 is referred to as the discharge current.

[0023] The battery pack equalization device 18 is a device that equalizes the remaining capacity of each of the multiple batteries b1 to bn in the battery pack 2. The battery pack equalization device 18 performs equalization by charging and discharging the multiple batteries b1 to bn so as to eliminate differences in SOC or voltage among the multiple batteries b1 to bn. A detailed description of equalization will be given later.

[0024] The battery pack equalization device 18 includes an equalization processing circuit 20 , a monitoring unit 22 , and a control unit 24 .

[0025] The equalization processing circuit 20 is a circuit for transferring electric charge between the plurality of batteries b1 to bn. The equalization processing circuit 20 has a transfer circuit that transfers electric charge between the plurality of batteries b1 to bn, and a voltage measurement circuit that measures the voltage of each of the plurality of batteries b1 to bn. The detailed configuration of the equalization processing circuit 20 will be described later.

[0026] The monitoring unit 22 acquires and monitors various information including information about the equalization processing circuit 20, such as the current value flowing through the delivery circuit and the voltage value of each of the plurality of batteries b1 to bn measured by the voltage measurement circuit, and information about the plurality of batteries b1 to bn, such as the current value measured by the ammeter 16 and the temperatures of the plurality of batteries b1 to bn. The monitoring unit 22 also outputs the acquired information to the control unit 24.

[0027] The control unit 24 controls the overall operation of the assembled battery equalization device 18 based on the various types of information output by the monitoring unit 22. The control unit 24 also controls the timing at which the monitoring unit 22 acquires the various types of information.

[0028] The control unit 24 includes an estimation unit 26 , an equalization current setting unit 28 , and an equalization processing unit 30 .

[0029] The estimation unit 26 estimates the remaining capacity of each of the plurality of batteries b1 to bn based on various information output by the monitoring unit 22. The remaining capacity may be the supplyable capacity or the ratio of the supplyable capacity to the battery capacity. For example, the estimation unit 26 may estimate the remaining capacity of each of the plurality of batteries b1 to bn by integrating the current value measured by the ammeter 16 with the time over which the ammeter 16 measures the current, or may estimate the remaining capacity of each of the plurality of batteries b1 to bn from the voltage values ​​of each of the plurality of batteries b1 to bn. Instead of estimating the remaining capacity of each of the plurality of batteries b1 to bn, the estimation unit 26 may estimate the total remaining capacity of the plurality of batteries b1 to bn. The total remaining capacity of the plurality of batteries b1 to bn may be the sum of the remaining capacities of each of the plurality of batteries b1 to bn, or may be the ratio of the total remaining capacity of each of the plurality of batteries b1 to bn estimated by the estimation unit 26 to the total capacity of each of the plurality of batteries b1 to bn.

[0030] The equalization current setting unit 28 sets the magnitude of the equalization current, which is the current flowing through the transfer circuit when the equalization processing unit 30 performs equalization, in accordance with the magnitude of the discharge current. The equalization current includes a charge equalization current, which is the current flowing through the transfer circuit when the equalization processing unit 30 performs equalization to charge one of the plurality of batteries b1 to bn that is the target of equalization, and a discharge equalization current, which is the current flowing through the transfer circuit when the equalization processing unit 30 performs equalization to discharge one of the plurality of batteries b1 to bn that is the target of equalization. The equalization current setting unit 28 sets the magnitude of the charge equalization current and the magnitude of the discharge equalization current, respectively, in accordance with the magnitude of the discharge current.

[0031] The equalization current setting unit 28 sets the magnitude of the discharge equalization current so that the total current value of the discharge current and the discharge equalization current is equal to or less than the upper limit value set for the plurality of batteries b1 to bn. The equalization current setting unit 28 also sets the magnitude of the charge equalization current so that the total current value of the discharge current and the charge equalization current does not become negative and approaches zero. In this specification, a positive current value indicates that the battery is discharging externally, and a negative current value indicates that the battery is charging externally. In other words, a negative sum of the discharge current and the charge equalization current means that the absolute value of the negative charge equalization current is greater than the positive discharge current.

[0032] The equalization processing unit 30 performs equalization by controlling the transfer circuit so that an equalization current of a magnitude set by the equalization current setting unit 28 flows through the transfer circuit. The equalization processing unit 30 performs equalization when the remaining capacity estimated by the estimation unit 26 is equal to or less than a predetermined value (e.g., 30%) and when a voltage difference ΔV, which is the difference between the maximum and minimum voltages based on the voltage measured by the voltage measurement circuit, is equal to or greater than an equalization start voltage Vth set at a predetermined voltage value (e.g., 50 mV). The equalization processing unit 30 may determine whether at least one estimated remaining capacity is equal to or less than a predetermined value, or may determine whether all estimated remaining capacities are equal to or less than a predetermined value. Alternatively, the equalization processing unit 30 may calculate an average value of all estimated remaining capacities and determine whether the calculated average value is equal to or less than a predetermined value.

[0033] The equalization processing unit 30 may perform equalization in parallel with the supply of discharge current from the plurality of batteries b1 to bn to the load 4, or may perform equalization when the supply of discharge current from the plurality of batteries b1 to bn to the load 4 has stopped.

[0034] The monitoring unit 22 and the control unit 24 are realized by a microcomputer, a processor, etc. That is, the functions of the monitoring unit 22 and the control unit 24 are realized by the microcomputer, the processor, etc. executing a program stored in a memory.

[0035] The assembled battery equalization device 18 may also have a memory unit that stores various information and programs acquired by the monitoring unit 22. The memory unit may also store a flag value (0 or 1) that is updated by the equalization processing unit 30. When the read flag value is 0, the equalization processing unit 30 charges the battery whose voltage is at the minimum value for a predetermined time, and when the read flag value is 1, the equalization processing unit 30 discharges the battery whose voltage is at the maximum value for a predetermined time. The memory unit may also store flag values ​​with 0 as the initial value.

[0036] The equalization currents described herein may also be referred to as balancing currents.

[0037] 2A to 2C, the detailed configuration of the equalization processing circuit 20 will be described. Note that the configuration of the equalization processing circuit 20 shown in FIG. 2A to 2C is an example, and modifications of the various components are within the scope of the present disclosure as long as the functions of the equalization processing circuit 20 are performed.

[0038] First, a description will be given of the equalization processing circuit 20 shown in Fig. 2A. Fig. 2A is a circuit diagram showing a first configuration example of the equalization processing circuit 20. The configuration of the equalization processing circuit 20 shown in Fig. 2A is referred to as an intermediate storage system.

[0039] The equalization processing circuit 20 includes a plurality of voltmeters V1 to Vn, a plurality of changeover switches SWa to SWz, a capacitor 32, and a non-insulated DC / DC converter .

[0040] The multiple voltmeters V1 to Vn measure the voltages of the multiple batteries b1 to bn connected in series. The voltmeters V1 to Vn are connected to the positive and negative electrodes of the multiple batteries b1 to bn, respectively, and measure the voltages between the electrodes of each of the multiple batteries b1 to bn. In this specification, the voltmeters V1 to Vn and the wiring connected to the positive and negative electrodes of the multiple batteries b1 to bn are referred to as a voltage measurement circuit. The number of voltmeters included in the equalization processing circuit 20 varies depending on the number of connected batteries. FIG. 2A shows an example in which the equalization processing circuit 20 includes four voltmeters V1 to V4, corresponding to the number of batteries included in the battery pack 2 (i.e., four batteries b1 to b4). Alternatively, a single voltmeter may be used to measure the voltages of the multiple batteries b1 to bn by switching between them.

[0041] The multiple changeover switches SWa to SWz are, for example, switching elements such as semiconductor relays. The number of changeover switches included in the equalization processing circuit 20 increases or decreases depending on the number of batteries connected. Note that Fig. 2A shows an example in which the equalization processing circuit 20 includes nine changeover switches SWa to SWi.

[0042] The multiple changeover switches SWa to SWz are provided on wiring that electrically connects the non-insulated DC / DC converter 34 and the multiple batteries b1 to bn. In this specification, the wiring including the multiple changeover switches SWa to SWz is referred to as a transfer circuit. The transfer circuit is a circuit for transferring charge between the multiple batteries b1 to bn.

[0043] The capacitor 32 stores the electric charge discharged from each of the plurality of batteries b1 to bn via the non-insulated DC / DC converter 34. The capacitor 32 also releases the stored electric charge to each of the plurality of batteries b1 to bn via the non-insulated DC / DC converter 34.

[0044] The non-insulated DC / DC converter 34 is configured using, for example, a chopper circuit, etc. The non-insulated DC / DC converter 34 is a circuit that converts the DC power input from each of the multiple batteries b1 to bn into DC power suitable for charging the capacitor 32 and outputs it to the capacitor 32. The non-insulated DC / DC converter 34 is also a circuit that converts the DC power input from the capacitor 32 into DC power suitable for charging each of the multiple batteries b1 to bn and outputs it to each of the multiple batteries b1 to bn.

[0045] The ammeter that measures the equalizing current flowing through the transfer circuit may be included in the non-insulated DC / DC converter 34 or may be included in the transfer circuit. Also, the voltmeter that measures the capacitor voltage VC that indicates the voltage of the capacitor 32 may be included in the non-insulated DC / DC converter 34 or may be connected in parallel with the capacitor 32.

[0046] As explained above, the equalization processing circuit 20 transfers charge from a battery with a high voltage (or a large remaining capacity) to the capacitor 32, and transfers charge from the capacitor 32 to a battery with a low voltage (or a small remaining capacity), thereby achieving charge transfer (equalization). Specifically, the equalization processing unit 30 controls the on / off of the multiple switches SWa to SWz (i.e., controls the transfer circuit) to switch the electrical connection between the capacitor 32 and each of the multiple batteries b1 to bn, thereby performing equalization.

[0047] Next, a description will be given of the equalization processing circuit 20 shown in Fig. 2B. Fig. 2B is a circuit diagram showing a second configuration example of the equalization processing circuit 20. The configuration of the equalization processing circuit 20 shown in Fig. 2B is called an isolation transformer system.

[0048] The equalization processing circuit 20 includes a plurality of voltmeters V1 to Vn, a plurality of changeover switches SWa to SWz, and an isolated DC / DC converter 36. Note that the plurality of voltmeters V1 to Vn and the voltage measurement circuit are the same as the plurality of voltmeters V1 to Vn and the voltage measurement circuit shown in FIG. 2A, and therefore a description thereof will be omitted.

[0049] The multiple changeover switches SWa to SWz are, for example, switching elements such as semiconductor relays. The number of changeover switches included in the equalization processing circuit 20 increases or decreases depending on the number of batteries connected. Figure 2B shows an example in which the equalization processing circuit 20 includes nine changeover switches SWa to SWi.

[0050] The multiple changeover switches SWa to SWz are provided on wiring that electrically connects the isolated DC / DC converter 36 to each of the multiple batteries b1 to bn. In this specification, the wiring including the multiple changeover switches SWa to SWz and the wiring that electrically connects the isolated DC / DC converter 36 to the battery pack 2 are referred to as a transfer circuit.

[0051] The isolated DC / DC converter 36 is configured using, for example, a flyback circuit. The primary circuit of the isolated DC / DC converter 36 is connected to one of the wirings of the transfer circuit, and the secondary circuit of the isolated DC / DC converter 36 is connected to the other wiring of the transfer circuit.

[0052] As described above, the equalization processing circuit 20 can transfer charge from a battery with a high voltage (or a large remaining capacity) to the battery pack 2, thereby discharging the high-voltage battery. Specifically, the equalization processing circuit 30 controls the on / off of the multiple switches SWa-SWz (i.e., controls the transfer circuit) to switch the electrical connection between the isolated DC / DC converter 36 and each of the multiple batteries b1-bn, thereby discharging the high-voltage battery. The equalization processing circuit 20 also transfers charge from the battery pack 2 to a battery with a low voltage (or a small remaining capacity), thereby charging the low-voltage battery. Specifically, the equalization processing circuit 30 controls the on / off of the multiple switches SWa-SWz (i.e., controls the transfer circuit) to switch the electrical connection between the isolated DC / DC converter 36 and each of the multiple batteries b1-bn, thereby charging the low-voltage battery. The equalization processing circuit 30 achieves equalization by repeatedly discharging the high-voltage battery and charging the low-voltage battery.

[0053] Next, the equalization processing circuit 20 shown in FIG. 2C will be described. FIG. 2C is a circuit diagram showing a third configuration example of the equalization processing circuit 20. Note that, like the equalization processing circuit 20 shown in FIG. 2B, the configuration of the equalization processing circuit 20 shown in FIG. 2C is referred to as an isolated transformer system. The equalization processing circuit 20 shown in FIG. 2C differs from the equalization processing circuit 20 shown in FIG. 2B in that it includes n isolated DC / DC converters 36 (the same number as the number of batteries b1 to bn) and does not include multiple change-over switches SWa to SWz.

[0054] The equalization processing circuit 20 includes a plurality of voltmeters V1 to Vn and n isolated DC / DC converters 36. The plurality of voltmeters V1 to Vn and the voltage measurement circuit are the same as the plurality of voltmeters V1 to Vn and the voltage measurement circuit shown in FIG. 2A, and therefore a description thereof will be omitted.

[0055] In FIG. 2C, the wiring electrically connecting the n isolated DC / DC converters 36 to each of the plurality of batteries b1 to bn, and the wiring electrically connecting the n isolated DC / DC converters 36 to the battery pack 2 are called transfer circuits.

[0056] The primary side circuit of each of the n isolated DC / DC converters 36 is connected to one of the wirings of the transfer circuits, and the secondary side circuit of each of the n isolated DC / DC converters 36 is connected to the other of the wirings of the transfer circuits. The number of isolated DC / DC converters 36 in the equalization processing circuit 20 increases or decreases depending on the number of connected batteries. Figure 2C shows an example in which the equalization processing circuit 20 includes four isolated DC / DC converters 36.

[0057] As described above, the equalization processing circuit 20 can transfer charge from a battery with a higher voltage (or a higher remaining capacity) to the battery pack 2, thereby discharging the higher voltage battery. Specifically, the equalization processing circuit 30 controls the n isolated DC / DC converters 36 to discharge the higher voltage battery. The equalization processing circuit 20 can also transfer charge from the battery pack 2 to a battery with a lower voltage (or a lower remaining capacity), thereby charging the lower voltage battery. Specifically, the equalization processing circuit 30 controls the n isolated DC / DC converters 36 to charge the lower voltage battery. The equalization processing circuit 30 achieves equalization by repeatedly discharging the higher voltage battery and charging the lower voltage battery. Alternatively, the equalization processing circuit 30 can achieve equalization by using any isolated DC / DC converter to transfer charge from the higher voltage battery to the lower voltage battery.

[0058] [First Operation Example] Fig. 3 is a flowchart showing a first operation example performed by the assembled battery equalization device 18 shown in Fig. 1. The assembled battery equalization device 18 can execute the first operation example shown in Fig. 3 regardless of whether it has any of the equalization processing circuits 20 shown in Figs. 2A to 2C.

[0059] First, the estimation unit 26 estimates the remaining capacity of each of the plurality of batteries b1 to bn (step S101) based on various information output by the monitoring unit 22. Note that in step S101, the estimation unit 26 may estimate the remaining capacity of the entire plurality of batteries b1 to bn instead of estimating the remaining capacity of each of the plurality of batteries b1 to bn.

[0060] The equalization processing unit 30 determines whether the remaining capacity estimated by the estimation unit 26 in step S101 is equal to or less than a predetermined value (step S102). Note that in step S102, the equalization processing unit 30 may determine whether at least one estimated remaining capacity is equal to or less than a predetermined value, or may determine whether all estimated remaining capacities are equal to or less than a predetermined value. Alternatively, the equalization processing unit 30 may calculate an average value from the estimated remaining capacities and determine whether the calculated average value is equal to or less than a predetermined value.

[0061] If it is determined that the remaining capacity is greater than the predetermined value (No in step S102), the equalization processing unit 30 ends the operation. Note that the control unit 24 may start the operation again from step S101 after a certain time has elapsed since the end of the operation.

[0062] If it is determined that the remaining capacity is equal to or less than the predetermined value (Yes in step S102), the voltage measurement circuit measures the voltage of each of the plurality of batteries b1 to bn (step S103).

[0063] The equalization processing unit 30 calculates the voltage difference ΔV between the battery with the highest voltage and the battery with the lowest voltage based on the voltages of each of the multiple batteries b1 to bn measured by the voltage measurement circuit in step S103, and determines whether the voltage difference ΔV is equal to or greater than the equalization start voltage Vth (step S104).

[0064] If it is determined that the voltage difference ΔV is smaller than the equalization start voltage Vth (No in step S104), the equalization processing unit 30 ends the operation. Note that the control unit 24 may resume the operation from step S101 after a certain time has elapsed since the end of the operation.

[0065] When it is determined that the voltage difference ΔV is equal to or greater than the equalization start voltage Vth (Yes in step S104), the ammeter 16 measures the discharge current (step S105).

[0066] The equalization current setting unit 28 sets the equalization current in accordance with the discharge current measured by the ammeter 16 in step S105 (step S106).

[0067] The equalization processing unit 30 determines whether the Flag stored in the storage unit is 0 (step S107).

[0068] If it is determined that the flag is 0 (Yes in step S107), the equalization processing unit 30 charges the battery whose voltage shows the minimum value for a predetermined time (step S108). At this time, the equalization processing unit 30 charges the battery based on the equalization current set by the equalization current setting unit 28 in step S106.

[0069] After a predetermined time has elapsed since the start of charging in step S108, the equalization processing unit 30 stops charging, updates the flag to 1, and stores the flag in the storage unit (step S109). Specifically, when the equalization processing circuit 20 has the configuration shown in FIG. 2A or 2B, the equalization processing unit 30 controls the multiple changeover switches SWa to SWz so that all of the multiple changeover switches SWa to SWz are turned off, thereby stopping charging. When the equalization processing circuit 20 has the configuration shown in FIG. 2C, the equalization processing unit 30 controls the isolated DC / DC converter 36 to stop charging.

[0070] If it is determined that the flag is not 0 (i.e., the flag is 1) (No in step S107), the equalization processing unit 30 discharges the battery whose voltage shows the maximum value for a predetermined time (step S110). At this time, the equalization processing unit 30 discharges the battery based on the equalization current set by the equalization current setting unit 28 in step S106.

[0071] After a predetermined time has elapsed since the start of discharge in step S110, the equalization processing unit 30 stops the discharge, updates the flag to 0, and stores the flag in the storage unit (step S111). Specifically, when the equalization processing circuit 20 has the configuration shown in FIG. 2A, the equalization processing unit 30 stops the non-insulated DC / DC converter 34 and controls the multiple switches SWa to SWz so that all of the switches SWa to SWz are turned off, thereby stopping the discharge. When the equalization processing circuit 20 has the configuration shown in FIG. 2B, the equalization processing unit 30 stops the isolated DC / DC converter 36 and controls the multiple switches SWa to SWz so that all of the switches SWa to SWz are turned off, thereby stopping the discharge. When the equalization processing circuit 20 has the configuration shown in FIG. 2C, the equalization processing unit 30 controls the isolated DC / DC converter 36 to stop the discharge.

[0072] After performing step S109 or step S111, the battery pack equalization device 18 returns to step S103 and performs the above-described operation again.

[0073] 3, step S106 corresponds to the equalization current setting step, and steps S108 and S110 correspond to the equalization processing steps.

[0074] Furthermore, after performing step S109 or step S111, if a predetermined condition is satisfied, the assembled battery equalization device 18 may return to step S103 and perform the above-described operation again, and if the predetermined condition is not satisfied, the assembled battery equalization device 18 may return to step S107 and perform the above-described operation again. The predetermined condition may be, for example, whether the number of times step S107 has been performed exceeds a certain number of times, or whether the time required for steps S108 and S110 has exceeded a certain time.

[0075] Alternatively, the equalization processing unit 30 may calculate the voltage difference ΔV calculated in step S104 using the following method. The voltage measurement circuit measures the voltage of each of the plurality of batteries b1 to bn in the equalization processing step (step S108 or step S110). The equalization processing unit 30 calculates the internal resistance of each of the plurality of batteries b1 to bn based on the measured voltage and the current measured by the ammeter 16 in the equalization processing step. The equalization processing unit 30 then corrects the voltage of each of the plurality of batteries b1 to bn measured by the voltage measurement circuit in step S103 by the voltage drop due to the respective internal resistances to calculate the voltage difference ΔV.

[0076] As explained above, the battery pack equalization device 18 can repeatedly charge and discharge batteries as needed, thereby making it possible to equalize the remaining capacity of each of the multiple batteries b1 to bn connected in series.

[0077] Furthermore, the battery pack equalization device 18 performs equalization so that an equalization current of a magnitude set according to the magnitude of the discharge current flows through the transfer circuit, so that the amount of current discharged from the batteries b1 to bn can be kept within the range of the rated current set for the batteries b1 to bn. As a result, the battery pack equalization device 18 can suppress further deterioration of the batteries b1 to bn even when there is a large variation in deterioration among the batteries.

[0078] Furthermore, the battery pack equalization device 18 uses the voltages corrected by the equalization processing unit 30, and therefore can calculate the voltage difference ΔV using more accurate voltages of each of the plurality of batteries b1 to bn.

[0079] [Second Operation Example] Fig. 4 is a flowchart showing a second operation example performed by the assembled battery equalization device 18 shown in Fig. 1. Note that the assembled battery equalization device 18 can execute the second operation example shown in Fig. 4 when it has the equalization processing circuit 20 shown in Fig. 2A. Furthermore, steps S201 to S206 shown in Fig. 4 are the same as steps S101 to S106 shown in Fig. 3, respectively, and therefore description thereof will be omitted.

[0080] The voltmeter included in the equalization processing circuit 20 measures the capacitor voltage VC (step S207).

[0081] The equalization processing unit 30 determines whether the capacitor voltage VC measured in step S207 is smaller than a capacitor charging determination voltage VCth (step S208). The capacitor charging determination voltage VCth is the median between a preset upper limit voltage (e.g., 10 V) and a preset lower limit voltage (e.g., 5 V).

[0082] If the capacitor voltage VC is smaller than the capacitor charging determination voltage VCth (Yes in step S208), the equalization processing unit 30 controls the multiple changeover switches SWa to SWz so that the circuit discharges charge from the battery whose voltage shows the maximum value to the capacitor 32 (step S209).

[0083] The equalization processing unit 30 discharges the battery whose voltage is at the maximum value to the capacitor 32 (step S210).

[0084] The equalization processing unit 30 determines whether the capacitor voltage VC is equal to or greater than a preset upper limit voltage (step S211). For example, the equalization processing unit 30 makes the determination in step S211 using the capacitor voltage VC measured by a voltmeter included in the equalization processing circuit 20 after step S210.

[0085] If the capacitor voltage VC is lower than the preset upper limit voltage (No in step S211), the equalization processing unit 30 returns to step S210 and continues discharging.

[0086] If the capacitor voltage VC is equal to or higher than a preset upper limit voltage (Yes in step S211), the equalization processing unit 30 controls the multiple changeover switches SWa to SWz so that all of the multiple changeover switches SWa to SWz are turned off (step S212).

[0087] If the capacitor voltage VC is greater than the capacitor charging determination voltage VCth (No in step S208), the equalization processing unit 30 controls the multiple changeover switches SWa to SWz so that the circuit charges the battery whose voltage shows the minimum value from the capacitor 32 (step S213).

[0088] The equalization processing unit 30 charges the battery whose voltage shows the minimum value from the capacitor 32 (step S214).

[0089] The equalization processing unit 30 determines whether the capacitor voltage VC is equal to or lower than a preset lower limit voltage (step S215). For example, the equalization processing unit 30 makes the determination in step S215 using the capacitor voltage VC measured by the voltmeter included in the equalization processing circuit 20 after step S214.

[0090] If the capacitor voltage VC is higher than the preset lower limit voltage (No in step S215), the equalization processing unit 30 returns to step S214 and continues charging.

[0091] If the capacitor voltage VC is equal to or lower than a preset lower limit voltage (Yes in step S215), the equalization processing unit 30 controls the multiple changeover switches SWa to SWz so that all of the multiple changeover switches SWa to SWz are turned off (step S212).

[0092] After performing step S212, the battery pack equalization device 18 returns to step S203 and performs the above-described operation again.

[0093] 4, step S206 corresponds to the equalization current setting step, and steps S209 to S210 and steps S213 to S214 correspond to the equalization processing steps.

[0094] Furthermore, after performing step S211 or step S215, if a predetermined condition is satisfied, the battery pack equalization device 18 may return to step S203 and perform the above-described operation again, and if the predetermined condition is not satisfied, the battery pack equalization device 18 may return to step S208 and perform the above-described operation again. The predetermined condition may be, for example, whether the number of times step S208 has been performed exceeds a certain number of times, or whether the time required for steps S210 and S214 has exceeded a certain time.

[0095] Alternatively, the equalization processing unit 30 may calculate the voltage difference ΔV calculated in step S104 using the following method. The voltage measurement circuit measures the voltage of each of the plurality of batteries b1 to bn in the equalization processing step (steps S209 to S210 or steps S213 to S214). The equalization processing unit 30 calculates the internal resistance of each of the plurality of batteries b1 to bn based on the measured voltage and the current measured by the ammeter 16 in the equalization processing step. The equalization processing unit 30 then corrects the voltage of each of the plurality of batteries b1 to bn measured by the voltage measurement circuit in step S203 by the voltage drop due to the respective internal resistances to calculate the voltage difference ΔV.

[0096] As explained above, the battery pack equalization device 18 transfers charge from the battery with the maximum voltage to the battery with the minimum voltage, thereby equalizing the remaining capacities of the batteries. By repeating this operation, the battery pack equalization device 18 can equalize the remaining capacities of the multiple batteries b1 to bn.

[0097] Furthermore, the battery pack equalization device 18 sets the magnitude of the charge equalization current and the magnitude of the discharge equalization current separately, so that the equalization current can be set in accordance with more detailed conditions.

[0098] Furthermore, the battery pack equalization device 18 sets the magnitude of the discharge equalization current so that the total current value of the discharge current and the discharge equalization current is equal to or less than the upper limit, thereby making it possible to suppress over-discharge.

[0099] Furthermore, the battery pack equalizer 18 sets the magnitude of the charge equalization current so that the sum of the discharge current and the charge equalization current does not become a negative value, thereby making it possible to equalize the number of charge / discharge cycles of the batteries b1 to bn. This allows the battery pack equalizer 18 to suppress cycle deterioration of the batteries b1 to bn.

[0100] Furthermore, the battery pack equalization device 18 sets the magnitude of the charge equalization current so that the total current value of the discharge current and the charge equalization current approaches zero, thereby suppressing further deterioration of the batteries being charged.

[0101] [Specific Example] The operation of the battery pack equalization device 18 described in FIGS. 3 and 4 will be described with reference to FIG. 5. FIG. 5 is a diagram showing the change over time in the voltage of each of the plurality of batteries b1 to bn. In the graph shown in FIG. 5, the vertical axis represents voltage (mV) and the horizontal axis represents the battery discharge capacity (mAh). The explanation of FIG. 5 also describes a case where the battery pack 2 has four batteries. FIG. 5 is a diagram showing the change over time from when the control unit 24 starts supplying current from the four batteries b1 to b4 to the load 4 until the current supply is stopped.

[0102] In the graph shown in Figure 5, the dashed line at 4200 mV indicates the battery voltage when fully charged, and the dashed line at 2500 mV indicates the discharge cut-off voltage. Full charge refers to a state of charge in which the remaining capacity of the battery is 100%. The discharge cut-off voltage refers to the voltage at which the discharge of at least one of the multiple batteries b1 to bn is stopped, that is, the voltage when the remaining capacity of at least one battery is 0%.

[0103] As shown in FIG. 5, as time passes after the control unit 24 starts supplying discharge current from the four batteries b1 to b4 to the load 4, the voltage of each of the four batteries b1 to b4 decreases.

[0104] The equalization processing unit 30 performs equalization within the area indicated by the dashed lines in Fig. 5, and equalizes the remaining capacities of the four batteries b1 to b4 until the voltage of any one of the four batteries b1 to b4 reaches 2500 mV. The equalization processing unit 30 charges and discharges at a cycle of 100 Hz.

[0105] As described above, the battery pack equalization device 18 can perform equalization even when a plurality of batteries b1 to bn are supplying discharge current to the load 4.

[0106] [Effects] As described above, the battery pack equalization device 18 according to this embodiment is an assembled battery equalization device 18 that performs equalization to make the remaining capacity of each of a plurality of series-connected batteries b1 to bn the same, and includes an ammeter 16 that measures a discharge current, which is a current supplied from the plurality of batteries b1 to bn to the load 4, a transfer circuit that transfers charge between the plurality of batteries b1 to bn, an equalization current setting unit 28 that sets the magnitude of the equalization current, which is a current that flows through the transfer circuit when equalization is performed, in accordance with the magnitude of the discharge current, and an equalization processing unit 30 that performs equalization by controlling the transfer circuit so that an equalization current of the magnitude set by the equalization current setting unit 28 flows through the transfer circuit.

[0107] The battery pack equalizer 18 performs equalization so that an equalization current of a magnitude set according to the magnitude of the discharge current flows through the transfer circuit, thereby keeping the amount of current discharged from the batteries b1 to bn within the range of the rated current set for the batteries b1 to bn. This allows the battery pack equalizer 18 to suppress further deterioration of the batteries b1 to bn even when there is a large variation in deterioration among the batteries.

[0108] Furthermore, the battery pack equalization device 18 according to this embodiment includes an estimation unit 26 that estimates the remaining capacity of each of the plurality of batteries b1 to bn or the remaining capacity of the entire plurality of batteries b1 to bn, and a voltage measurement circuit that measures the voltage of each of the plurality of batteries b1 to bn. The equalization processing unit 30 executes equalization when (1) the remaining capacity estimated by the estimation unit 26 is equal to or less than a predetermined value, and (2) the voltage difference ΔV, which is the difference between the maximum and minimum voltages based on the voltages measured by the voltage measurement circuit, is equal to or greater than a predetermined equalization start voltage Vth.

[0109] The battery pack equalizer 18 can determine the state of the batteries that require equalization, and can start equalization at the appropriate timing. This allows the battery pack equalizer 18 to simultaneously use up each of the multiple batteries b1 to bn, thereby improving the effective capacity of the battery pack 2.

[0110] Furthermore, in the assembled battery equalization device 18 according to this embodiment, the equalization processing unit 30 executes equalization in parallel with the supply of discharge current from the plurality of batteries b1 to bn to the load 4.

[0111] Such a battery pack equalizer 18 can perform equalization even when a plurality of batteries b1 to bn are supplying discharge current to the load 4.

[0112] Furthermore, in the assembled battery equalization device 18 according to this embodiment, the equalization processing unit 30 performs equalization by controlling the transfer of charge from the battery whose voltage based on the voltage measured by the voltage measurement circuit is at the maximum value to the battery whose voltage based on the voltage is at the minimum value.

[0113] This type of battery pack equalization device 18 transfers charge from the battery whose voltage measured by the voltage measurement circuit indicates the maximum value to the battery whose voltage measured by the voltage measurement circuit indicates the minimum value, thereby making it possible to equalize the remaining capacities of the batteries. By repeating this operation, the battery pack equalization device 18 can make the remaining capacities of the multiple batteries b1 to bn equal.

[0114] Furthermore, in the assembled battery equalization device 18 according to this embodiment, the voltage based on the voltage measured by the voltage measurement circuit is a voltage corrected by the equalization processing unit 30 .

[0115] Such a battery pack equalizer 18 uses the voltages corrected by the equalization processing unit 30, and therefore can calculate the voltage difference ΔV using more accurate voltages of each of the plurality of batteries b1 to bn.

[0116] Furthermore, in the battery pack equalization device 18 according to this embodiment, the equalization current includes a charge equalization current, which is a current that flows through the transfer circuit when the battery is being charged, and a discharge equalization current, which is a current that flows through the transfer circuit when the battery is being discharged, and the equalization current setting unit 28 sets the magnitude of the charge equalization current and the magnitude of the discharge equalization current, respectively.

[0117] The battery pack equalizer 18 sets the magnitude of the charge equalization current and the magnitude of the discharge equalization current separately, so that the equalization current can be set to suit more specific situations. As a result, the battery pack equalizer 18 can suppress further deterioration of the batteries b1 to bn even when there is a large variation in deterioration among the batteries.

[0118] Furthermore, in the battery pack equalization device 18 according to this embodiment, the equalization current setting unit 28 sets the magnitude of the discharge equalization current so that the total current value of the discharge current and the discharge equalization current is equal to or less than the upper limit value set for the plurality of batteries b1 to bn.

[0119] The battery pack equalizer 18 sets the magnitude of the discharge equalization current so that the total current value of the discharge current and the discharge equalization current is equal to or less than the upper limit, thereby preventing overdischarge. This allows the battery pack equalizer 18 to prevent further deterioration of the batteries b1 to bn even when there is a large variation in deterioration among the batteries.

[0120] In addition, in the assembled battery equalization device 18 according to this embodiment, the equalization current setting unit 28 sets the magnitude of the charge equalization current so that the total current value of the discharge current and the charge equalization current does not become a negative value.

[0121] The battery pack equalizer 18 sets the magnitude of the charge equalization current so that the sum of the discharge current and the charge equalization current does not become a negative value, thereby making it possible to equalize the number of charge / discharge cycles of the batteries b1 to bn. This allows the battery pack equalizer 18 to suppress cycle deterioration of the batteries b1 to bn, and even when there is a large variation in deterioration among the batteries, it is possible to suppress further deterioration of the batteries b1 to bn.

[0122] Furthermore, in the assembled battery equalization device 18 according to this embodiment, the equalization current setting unit 28 sets the magnitude of the charge equalization current so that the total current value of the discharge current and the charge equalization current approaches zero.

[0123] The battery pack equalizer 18 sets the magnitude of the charge equalization current so that the sum of the discharge current and the charge equalization current approaches zero, thereby further suppressing deterioration of the batteries being charged. This allows the battery pack equalizer 18 to suppress further deterioration of the batteries b1 to bn even when there is a large variation in the deterioration of the batteries.

[0124] Furthermore, the battery pack equalization method according to this embodiment is a battery pack equalization method using a battery pack equalization device 18 that performs equalization to make the remaining capacity of each of a plurality of series-connected batteries b1 to bn the same. The battery pack equalization device 18 includes an ammeter 16 that measures a discharge current, which is a current supplied from the plurality of batteries b1 to bn to a load 4, and a transfer circuit that transfers charge between the plurality of batteries b1 to bn. The battery pack equalization method includes an equalization current setting step that sets the magnitude of the equalization current, which is a current that flows through the transfer circuit during equalization, in accordance with the magnitude of the discharge current, and an equalization processing step that performs equalization by controlling the transfer circuit so that an equalization current of the magnitude set in the equalization current setting step flows through the transfer circuit.

[0125] According to this battery pack equalization method, equalization is performed so that an equalization current of a magnitude set according to the magnitude of the discharge current flows through the transfer circuit, and the amount of current discharged from the batteries b1 to bn can be kept within the range of the rated current set for the batteries b1 to bn. As a result, the battery pack equalization method can suppress further deterioration of the batteries even when there is a large variation in deterioration among the batteries.

[0126] The program according to the present embodiment causes a computer to execute the assembled battery equalization method according to the present embodiment.

[0127] Such a program provides the same effects as the battery pack equalization method according to the present embodiment.

[0128] [Modifications] While the battery pack equalization device and the like according to the present disclosure have been described above based on the above-described embodiment, the present disclosure is not limited to the above-described embodiment. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the above-described embodiment and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects.

[0129] In the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0130] In the above-described embodiments, some or all of the functions of the components may be realized by a processor such as a CPU executing a program.

[0131] Some or all of the components constituting each of the above devices may be configured as an IC card or a standalone module that can be attached to or detached from each device. The IC card or module is a computer system composed of a microprocessor, ROM, RAM, etc. The IC card or module may include a super multi-function LSI. The IC card or module achieves its functions when the microprocessor operates in accordance with a computer program. The IC card or module may be tamper-resistant.

[0132] [Additional Notes] The above description of the embodiments discloses the following techniques.

[0133] (Technology 1) An assembled battery equalization device that performs equalization to make the remaining capacity of each of a plurality of batteries connected in series the same, the assembled battery equalization device comprising: an ammeter that measures a discharge current, which is a current supplied from the plurality of batteries to a load; a transfer circuit that transfers charge between the plurality of batteries; an equalization current setting unit that sets the magnitude of an equalization current, which is a current that flows through the transfer circuit when the equalization is performed, in accordance with the magnitude of the discharge current; and an equalization processing unit that performs the equalization by controlling the transfer circuit so that the equalization current of the magnitude set by the equalization current setting unit flows through the transfer circuit.

[0134] (Technology 2) The battery pack equalization device according to Technology 1 includes an estimation unit that estimates the remaining capacity of each of the plurality of batteries or the remaining capacity of all of the plurality of batteries, and a voltage measurement circuit that measures the voltage of each of the plurality of batteries, and the equalization processing unit performs the equalization when (1) the remaining capacity estimated by the estimation unit is equal to or less than a predetermined value, and (2) a voltage difference that is the difference between a maximum value and a minimum value of voltage based on the voltage measured by the voltage measurement circuit is equal to or greater than a predetermined equalization start voltage.

[0135] (Technology 3) The assembled battery equalizing device according to Technology 2, wherein the equalization processing unit performs the equalization in parallel with the plurality of batteries supplying the discharge current to the load.

[0136] (Technology 4) The battery pack equalization device according to Technology 2 or 3, wherein the equalization processing unit performs the equalization by controlling the transfer of charge from the battery whose voltage based on the voltage measured by the voltage measurement circuit is at a maximum value to the battery whose voltage based on the voltage is at a minimum value.

[0137] (Technology 5) The battery pack equalization device according to any one of Technologies 2 to 4, wherein the voltage based on the voltage measured by the voltage measurement circuit is a voltage corrected by the equalization processing unit.

[0138] (Technology 6) The battery pack equalization device according to any one of Technologies 1 to 5, wherein the equalization current includes a charge equalization current that is a current that flows through the delivery circuit when the battery is being charged, and a discharge equalization current that is a current that flows through the delivery circuit when the battery is being discharged, and the equalization current setting unit sets the magnitude of the charge equalization current and the magnitude of the discharge equalization current, respectively.

[0139] (Technology 7) The battery pack equalization device described in Technology 6, wherein the equalization current setting unit sets the magnitude of the discharge equalization current so that the total current value of the discharge current and the discharge equalization current is equal to or less than an upper limit value set for the plurality of batteries.

[0140] (Technology 8) The battery pack equalization device according to Technology 6 or 7, wherein the equalization current setting unit sets the magnitude of the charge equalization current so that a total current value of the discharge current and the charge equalization current does not become a negative value.

[0141] (Technology 9) The battery pack equalization device according to Technology 8, wherein the equalization current setting unit sets the magnitude of the charge equalization current so that a total current value of the discharge current and the charge equalization current approaches zero.

[0142] (Technology 10) A battery pack equalization method using a battery pack equalization device that performs equalization to make the remaining capacity of each of a plurality of batteries connected in series the same, the battery pack equalization device including an ammeter that measures a discharge current that is a current supplied from the plurality of batteries to a load, and a transfer circuit that transfers charge between the plurality of batteries, the battery pack equalization method including an equalization current setting step that sets a magnitude of an equalization current that is a current that flows through the transfer circuit during the equalization in accordance with the magnitude of the discharge current, and an equalization processing step that performs the equalization by controlling the transfer circuit so that the equalization current of the magnitude set in the equalization current setting step flows through the transfer circuit.

[0143] (Technology 11) A program for causing a computer to execute the battery pack equalization method according to Technology 10.

[0144] The assembled battery equalizing device and the like according to the present disclosure are useful, for example, as a device for equalizing the remaining capacity of each of a plurality of batteries connected in series.

[0145] 2 assembled battery 4 load 6A, 6B, 14A, 14B changeover switch 8 external power supply 10 AC power supply 12 converter 16 ammeter 18 assembled battery equalizer 20 equalization processing circuit 22 monitoring unit 24 control unit 26 estimation unit 28 equalization current setting unit 30 equalization processing unit 32 capacitor 34 non-insulated DC / DC converter 36 insulated DC / DC converter b1 to bn, b11 to b1m multiple batteries V1 to Vn multiple voltmeters SWa to SWz multiple changeover switches

Claims

1. A battery pack equalization device that performs equalization to make the remaining capacity of each of a plurality of batteries connected in series the same, comprising: an ammeter that measures a discharge current, which is a current supplied from the plurality of batteries to a load; a transfer circuit that transfers charge between the plurality of batteries; an equalization current setting unit that sets the magnitude of an equalization current, which is a current that flows through the transfer circuit when the equalization is performed, in accordance with the magnitude of the discharge current; and an equalization processing unit that performs the equalization by controlling the transfer circuit so that the equalization current of the magnitude set by the equalization current setting unit flows through the transfer circuit.

2. The battery pack equalization device according to claim 1, comprising an estimation unit that estimates the remaining capacity of each of the plurality of batteries or the remaining capacity of all of the plurality of batteries, and a voltage measurement circuit that measures the voltage of each of the plurality of batteries, wherein the equalization processing unit performs the equalization when: (1) the remaining capacity estimated by the estimation unit is equal to or less than a predetermined value, and (2) a voltage difference, which is the difference between the maximum and minimum values ​​of voltage based on the voltage measured by the voltage measurement circuit, is equal to or greater than a predetermined equalization start voltage.

3. The battery pack equalization device according to claim 2, wherein the equalization processing unit performs the equalization in parallel with the supply of the discharge current from the plurality of batteries to the load.

4. The battery pack equalization device according to claim 2 or 3, wherein the equalization processing unit performs the equalization by controlling the transfer of charge from the battery whose voltage based on the voltage measured by the voltage measurement circuit is at a maximum value to the battery whose voltage based on the voltage is at a minimum value.

5. The battery pack equalization device according to claim 2 or 3, wherein the voltage based on the voltage measured by the voltage measurement circuit is a voltage corrected by the equalization processing unit.

6. The battery pack equalization device according to claim 1, wherein the equalization current includes a charge equalization current that flows through the delivery circuit when the battery is being charged and a discharge equalization current that flows through the delivery circuit when the battery is being discharged, and the equalization current setting unit sets the magnitude of the charge equalization current and the magnitude of the discharge equalization current, respectively.

7. The battery pack equalization device according to claim 6, wherein the equalization current setting unit sets the magnitude of the discharge equalization current so that the total current value of the discharge current and the discharge equalization current is equal to or less than an upper limit value set for the plurality of batteries.

8. The battery pack equalization device according to claim 6 or 7, wherein the equalization current setting unit sets the magnitude of the charge equalization current so that the total current value of the discharge current and the charge equalization current does not become a negative value.

9. The battery pack equalization device according to claim 8, wherein the equalization current setting unit sets the magnitude of the charge equalization current so that the total current value of the discharge current and the charge equalization current approaches zero.

10. A battery pack equalization method using a battery pack equalization device that performs equalization to make the remaining capacity of each of a plurality of batteries connected in series the same, wherein the battery pack equalization device includes an ammeter that measures a discharge current that is a current supplied from the plurality of batteries to a load, and a transfer circuit that transfers charge between the plurality of batteries, and the battery pack equalization method includes an equalization current setting step that sets the magnitude of an equalization current that flows through the transfer circuit during the equalization in accordance with the magnitude of the discharge current, and an equalization processing step that performs the equalization by controlling the transfer circuit so that the equalization current of the magnitude set in the equalization current setting step flows through the transfer circuit.

11. A program for causing a computer to execute the battery pack equalization method according to claim 10.

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