Assembled battery equalization device and assembled battery equalization method

Abstract

An assembled battery equalization device (18) comprises: a monitoring unit (22) that acquires deterioration information indicating a degree of deterioration of each of a plurality of batteries (b1 to b4); and a control unit (24) that, on the basis of the deterioration information, determines a deteriorated battery which is a battery having the highest degree of deterioration from among the plurality of batteries (b1 to b4), and performs adjustment processing for adjusting the remaining capacity of the plurality of batteries (b1 to b4). The control unit (24) performs the adjustment processing so that the SOC of the deteriorated battery becomes lower than the SOCs of the other batteries when charging of the plurality of batteries (b1 to b4) is completed, or performs the adjustment processing so that the SOC of the deteriorated battery is higher than the SOCs of the other batteries when discharge of the plurality of batteries (b1 to b4) is completed.

Description

Battery pack equalization device and battery pack equalization method

[0001] The present disclosure relates to a battery pack equalization device and battery pack equalization method that equalize a plurality of batteries connected in series to make the remaining capacities of each battery the same.

[0002] Patent Document 1 discloses a technique for adjusting the capacity of a deteriorated battery in a battery pack having a plurality of batteries with varying capacities so that the SOC (State of Charge) of each of the plurality of batteries is uniform when discharge is completed.

[0003] Patent Document 2 discloses a technique for determining the setting conditions of the SOC of each battery according to at least one of the deterioration state of the battery, the capacity of the battery, and the temperature of the battery.

[0004] Patent No. 5463810 Patent No. 6541310

[0005] Since the deterioration of batteries such as lithium-ion batteries accelerates as the range of SOC used increases, the most deteriorated battery among the multiple batteries constituting the battery pack tends to have the smallest capacity and reach the upper and lower limits of its SOC earlier than the other batteries. For this reason, the techniques disclosed in Patent Documents 1 and 2 have the problem that even if the remaining capacities of the multiple batteries are adjusted so that the SOCs of the multiple batteries are the same at the end of discharging or charging, the most deteriorated battery among the multiple batteries reaches the upper and lower limits of its SOC earlier than the other batteries, accelerating the deterioration of the deteriorated battery.

[0006] Therefore, the present disclosure provides a battery pack equalization device and the like that can suppress the rate of deterioration of deteriorated batteries.

[0007] The battery pack equalization device disclosed herein is 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, and includes an acquisition unit that acquires deterioration information indicating the degree of deterioration of each of the plurality of batteries, a determination unit that determines a deteriorated battery among the plurality of batteries that is the battery with the highest degree of deterioration based on the deterioration information, and an adjustment unit that performs adjustment processing to adjust the remaining capacity of the plurality of batteries, wherein the adjustment unit performs the adjustment processing so that the SOC of the deteriorated battery is lower than the SOC of other batteries among the plurality of batteries when charging of the plurality of batteries is complete, or so that the SOC of the degraded battery is higher than the SOC of the other batteries when discharging of the plurality of batteries is complete.

[0008] The battery pack equalization method according to the present disclosure is a battery pack equalization method executed by a battery pack equalization device that equalizes the remaining capacities of a plurality of batteries connected in series, and includes an acquisition step of acquiring deterioration information indicating the degree of deterioration of each of the plurality of batteries; a determination step of determining, based on the deterioration information, a deteriorated battery that is the battery with the highest degree of deterioration among the plurality of batteries; and an adjustment step of performing an adjustment process to adjust the remaining capacities of the plurality of batteries, wherein the adjustment process is performed so that, when charging of the plurality of batteries is complete, the SOC of the deteriorated battery is lower than the SOC of the other batteries among the plurality of batteries, or so that, when discharging of the plurality of batteries is complete, the SOC of the degraded battery is higher than the SOC of the other batteries.

[0009] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0010] According to the assembled battery equalization device and the like according to one aspect of the present disclosure, the rate of deterioration of deteriorated batteries can be suppressed.

[0011] 1 is a configuration diagram showing an example of an assembled battery equalization device according to an embodiment. FIG. 2 is a circuit diagram showing a first example of an equalization processing circuit according to an embodiment. FIG. 3 is a circuit diagram showing a second example of an equalization processing circuit according to an embodiment. FIG. 4 is a circuit diagram showing a third example of an equalization processing circuit according to an embodiment. FIG. 5 is a circuit diagram showing a fourth example of an equalization processing circuit according to an embodiment. FIG. 6 is a flowchart showing an example of operation of an assembled battery equalization device according to an embodiment. FIG. 7 is a diagram for explaining adjustment processing of an assembled battery equalization device according to an embodiment. FIG. 8 is a diagram showing an example of adjustment processing during charging of an assembled battery equalization device according to an embodiment. FIG. 9 is a diagram showing an example of adjustment processing during discharging of an assembled battery equalization device according to an embodiment. FIG. 10 is a diagram showing another example of adjustment processing during charging of an assembled battery equalization device according to an embodiment. FIG. 11 is a diagram showing another example of adjustment processing during discharging of an assembled battery equalization device according to an embodiment. FIG. 12 is a flowchart showing an example of an assembled battery equalization method according to another embodiment.

[0012] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0013] The embodiments described below are all comprehensive or specific examples, and the numerical values, shapes, materials, components, arrangement and connection of the components, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0014] (Embodiment) Hereinafter, a battery pack equalization device according to an embodiment will be described.

[0015] 1 is a configuration diagram showing an example of a battery pack equalization device 18 according to an embodiment. In addition to the battery pack equalization device 18, Fig. 1 also shows a battery pack 2, a load 4, an external power supply 8, relays 6A, 6B, 14A, and 14B, and an ammeter 16.

[0016] The battery pack 2 has multiple batteries connected in series. Here, batteries b1 to b4 are shown as the multiple batteries that make up the battery pack 2. Below, the multiple batteries will be referred to as batteries b1 to b4, and an example will be described in which the number of multiple batteries is four, but the number of multiple batteries is not limited to four and may be two, three, five or more. Each of the batteries b1 to b4 is a secondary battery that can be charged and discharged, such as a lithium-ion battery.

[0017] 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.

[0018] The external power supply 8 is a power supply that supplies power to the battery pack 2. The external power supply 8 includes a conversion unit 12 that converts AC power from an AC power supply 10 into DC power. The conversion unit 12 is, for example, an alternating current (AC) / direct current (DC) converter.

[0019] The relays 14A and 14B are controlled to the ON state when power is supplied from the external power source 8 to the battery pack 2, that is, when the battery pack 2 is being charged. The relays 6A and 6B are controlled to the ON state when power is supplied from the battery pack 2 to the load 4, that is, when the battery pack 2 is being discharged.

[0020] The battery pack equalization device 18 is a device that equalizes the remaining capacities of the series-connected batteries b1 to b4 that make up the battery pack 2. Hereinafter, equalizing the remaining capacities of the batteries b1 to b4 will be simply referred to as equalization. The battery pack equalization device 18 performs equalization by charging and discharging the batteries b1 to b4 so as to eliminate differences in SOC or voltage among the batteries b1 to b4.

[0021] The assembled battery equalization device 18 includes an equalization processing circuit 20, a monitoring unit 22, and a control unit 24. The assembled battery equalization device 18 performs equalization using the equalization processing circuit 20, but also has a function of adjusting the remaining capacities of the batteries b1 to b4 when performing equalization. Specifically, the assembled battery equalization device 18 also has a function of increasing the remaining capacities of some of the batteries b1 to b4 compared to the other batteries when discharging is complete, and decreasing the remaining capacities of some of the batteries b1 to b4 compared to the other batteries when charging is complete. The assembled battery equalization device 18 achieves this function using the equalization processing circuit 20, the monitoring unit 22, and the control unit 24. The following describes the function of the equalization processing circuit 20, the monitoring unit 22, and the control unit 24 to adjust the remaining capacities of multiple batteries.

[0022] Here, first to fourth examples of the equalization processing circuit 20 will be described in detail.

[0023] First, a first example of the equalization processing circuit 20 will be described with reference to FIG.

[0024] FIG. 2 is a circuit diagram showing a first example of the equalization processing circuit 20 according to the embodiment.

[0025] The equalization processing circuit 20 of the first example includes changeover switches SWa to SWi, voltmeters V1 to V4, and an isolated DC / DC converter .

[0026] Voltmeters V1 to V4 measure the voltages of batteries b1 to b4, respectively. Voltmeter V1 is connected in parallel to battery b1 and measures the voltage between the electrodes of battery b1. Voltmeter V2 is connected in parallel to battery b2 and measures the voltage between the electrodes of battery b2. Voltmeter V3 is connected in parallel to battery b3 and measures the voltage between the electrodes of battery b3. Voltmeter V4 is connected in parallel to battery b4 and measures the voltage between the electrodes of battery b4. Information indicating the voltages measured by voltmeters V1 to V4 is input to monitoring unit 22. The number of voltmeters included in equalization processing circuit 20 increases or decreases depending on the number of batteries constituting battery pack 2. Furthermore, one voltmeter may be connected to different batteries while measuring the voltages of batteries b1 to b4. In other words, the voltage measurement circuit that measures the voltage of each of the batteries b1 to b4 that make up the battery pack 2 may be realized by a single voltmeter, or may be realized by a voltmeter provided for each of the batteries b1 to b4.

[0027] The changeover switches SWa to SWi are provided between the isolated DC / DC converter 36 and the batteries b1 to b4. The changeover switches SWa to SWi are controlled by the control unit 24. The changeover switches SWa to SWi are, for example, semiconductor switches. The number of changeover switches included in the equalization processing circuit 20 increases or decreases depending on the number of batteries that make up the battery pack 2.

[0028] For example, if battery b3 is a degraded battery as described below, and the remaining capacity of battery b3 is to be made greater than that of other batteries b1, b2, and b4 at the completion of discharging, or the remaining capacity of battery b3 is to be made less than that of other batteries b1, b2, and b4 at the completion of charging, the change-over switches SWb, SWc, SWg, and SWh are controlled when batteries b1 to b4 are being discharged or charged.

[0029] The isolated DC / DC converter 36 is a bidirectional DC / DC converter that boosts DC power input from any of batteries b1 to b4 to DC power suitable for charging the battery pack 2 and outputs it to the battery pack 2, and also reduces DC power input from the battery pack 2 to DC power suitable for charging any of batteries b1 to b4 and outputs it to that battery. Note that a capacitor or an independent power supply may be connected to the isolated DC / DC converter 36. In this case, the isolated DC / DC converter 36 may boost the DC power input from any of batteries b1 to b4 to DC power suitable for charging the capacitor or power supply and output it to that capacitor or power supply, or may reduce the DC power input from the capacitor or power supply to DC power suitable for charging any of batteries b1 to b4 and output it to that battery.

[0030] Next, a second example of the equalization processing circuit 20 will be described with reference to FIG.

[0031] FIG. 3 is a circuit diagram showing a second example of the equalization processing circuit 20 according to the embodiment.

[0032] The equalization circuit 20 of the second example differs from the equalization circuit 20 of the first example in that a non-insulated DC / DC converter 34 is provided instead of the isolated DC / DC converter 36, and a capacitor 32 is connected to the non-insulated DC / DC converter 34. The remaining points are the same as those of the equalization circuit 20 of the first example, and therefore a description thereof will be omitted.

[0033] The non-insulated DC / DC converter 34 boosts the DC power input from any one of the batteries b1 to b4 to DC power suitable for charging the capacitor 32 and outputs it to the capacitor 32, and also reduces the DC power input from the capacitor 32 to DC power suitable for charging any one of the batteries b1 to b4 and outputs it to that battery.

[0034] Instead of the capacitor 32 , an independent power supply may be connected to the non-insulated DC / DC converter 34 .

[0035] Next, a third example of the equalization processing circuit 20 will be described with reference to FIG.

[0036] FIG. 4 is a circuit diagram showing a third example of the equalization processing circuit 20 according to the embodiment.

[0037] The equalization processing circuit 20 of the third example differs from the equalization processing circuit 20 of the first example in that an isolated DC / DC converter 36 is provided for each of the batteries b1 to b4 instead of the changeover switches SWa to SWi. The other points are the same as those of the equalization processing circuit 20 of the first example, and therefore a description thereof will be omitted.

[0038] In the equalization processing circuit 20 of the third example, each isolated DC / DC converter 36 boosts the DC power input from the corresponding battery to DC power suitable for charging the battery pack 2 and outputs it to the battery pack 2, and also reduces the DC power input from the battery pack 2 to DC power suitable for charging the corresponding battery and outputs it to that battery. In the equalization processing circuit 20 of the third example, two or more of batteries b1 to b4 can be simultaneously charged or discharged via the isolated DC / DC converter 36. Note that in the third example as well, a capacitor or an independent power source may be connected to each isolated DC / DC converter 36.

[0039] Next, a fourth example of the equalization processing circuit 20 will be described with reference to FIG.

[0040] FIG. 5 is a circuit diagram showing a fourth example of the equalization processing circuit 20 according to the embodiment.

[0041] The equalization processing circuit 20 of the fourth example includes changeover switches SWj to SWm, voltmeters V1 to V4, and resistors R1 to R4.

[0042] The voltmeters V1 to V4 measure the voltages of the batteries b1 to b4, respectively, in the same manner as the equalization processing circuit 20 of the first example.

[0043] The changeover switch SWj and resistor R1 are connected in series, and the changeover switch SWj and resistor R1 are connected in parallel with battery b1. The changeover switch SWk and resistor R2 are connected in series, and the changeover switch SWk and resistor R2 are connected in parallel with battery b2. The changeover switch SWl and resistor R3 are connected in series, and the changeover switch SWl and resistor R3 are connected in parallel with battery b3. The changeover switch SWm and resistor R4 are connected in series, and the changeover switch SWm and resistor R4 are connected in parallel with battery b4.

[0044] For example, if the remaining capacity of battery b3 is to be made smaller than the remaining capacity of the other batteries b1, b2 and b4 when charging is completed, the changeover switch SW1 is controlled during charging.

[0045] Returning to the explanation of FIG. 1 , the monitoring unit 22 acquires deterioration information indicating the degree of deterioration of each of the batteries b1 to b4. The monitoring unit 22 is an example of an acquisition unit. The monitoring unit 22 may acquire the deterioration information by estimating the degree of deterioration of each of the batteries b1 to b4. The monitoring unit 22 outputs the acquired deterioration information to the control unit 24.

[0046] For example, the monitoring unit 22 may acquire deterioration information by obtaining, from the voltmeters V1 to V4, the voltages of the batteries b1 to b4 measured by the voltmeters V1 to V4. For example, the equalization processing circuit 20 may include an ammeter that measures the amount of charge transfer in each of the batteries b1 to b4, and the monitoring unit 22 may acquire deterioration information by obtaining, from the ammeter, the amount of charge transfer in each of the batteries b1 to b4 measured by the ammeter. For example, the monitoring unit 22 may acquire deterioration information by estimating the SOH (State of Health) of the batteries b1 to b4. For example, the equalization processing circuit 20 may include an ohmmeter that measures the internal resistance of each of the batteries b1 to b4, and the monitoring unit 22 may acquire deterioration information by obtaining, from the ohmmeter, the internal resistance of each of the batteries b1 to b4 measured by the ohmmeter. For example, the equalization processing circuit 20 may be equipped with a thermometer that measures the temperature of each of the batteries b1 to b4, and the monitoring unit 22 may obtain the deterioration information by acquiring the temperature of each of the batteries b1 to b4 measured by the thermometer.

[0047] The control unit 24 is a circuit that causes the equalization processing circuit 20 to adjust the capacities of the batteries b1 to b4. Specifically, the control unit 24 controls the switches and DC / DC converters of the equalization processing circuit 20 to transfer the charges of the batteries b1 to b4 among the batteries b1 to b4. Furthermore, the control unit 24 determines the most deteriorated battery among the batteries b1 to b4 based on the deterioration information, and performs an adjustment process to adjust the remaining capacities of the batteries b1 to b4. The control unit 24 is an example of a determination unit and an adjustment unit.

[0048] For example, in the first example of the equalization processing circuit 20, when the remaining capacity of battery b3 is to be greater than the remaining capacities of batteries b1, b2, and b4 during discharging of batteries b1 to b4, the control unit 24 controls the changeover switches SWb, SWc, SWg, and SWh to the on state and causes the isolated DC / DC converter 36 to perform a step-down operation, thereby transferring the charge of battery b3 to battery b3. For example, in the first example of the equalization processing circuit 20, when the remaining capacity of battery b3 is to be less than the remaining capacities of batteries b1, b2, and b4 during charging of batteries b1 to b4, the control unit 24 controls the changeover switches SWb, SWc, SWg, and SWh to the on state and causes the isolated DC / DC converter 36 to perform a step-up operation, thereby transferring the charge of battery b3 to the battery pack 2 (batteries b1 to b4).

[0049] The control unit 24 is a computer including a processor and a memory. The memory may be a read-only memory (ROM) or a random access memory (RAM), and may store programs to be executed by the processor. The control unit 24 is realized by a processor that executes programs stored in the memory. For example, the control unit 24 may be a microcomputer.

[0050] Next, the operation of the assembled battery equalizing device 18 (specifically, the control unit 24) will be described in detail with reference to FIG.

[0051] Fig. 6 is a flowchart showing an example of the operation of the battery pack equalization device 18 according to the embodiment. The process shown in Fig. 6 is initiated when the voltage of any one of the batteries b1 to b4 falls below a predetermined voltage during discharge of the battery pack 2, or when the voltage of any one of the batteries b1 to b4 rises above a predetermined voltage during charge of the battery pack 2, and equalization is performed to make the remaining capacities of the batteries b1 to b4 uniform.

[0052] First, the control unit 24 acquires current polarity information indicating whether the battery pack 2 is being charged or discharged (step S11). For example, the control unit 24 may acquire the current polarity information from a higher-level system, or may acquire the current polarity information based on the polarity of the current measured by an ammeter that measures the current flowing through the battery pack 2.

[0053] Next, the control unit 24 estimates the deterioration of the batteries b1 to b4 (step S12). Specifically, the control unit 24 determines the deteriorated battery among the batteries b1 to b4 that is the battery with the highest degree of deterioration based on the deterioration information. The method for determining the deteriorated battery will be described later.

[0054] Next, the control unit 24 measures the voltages of each of the batteries b1 to b4 via the monitoring unit 22, and stores the maximum cell voltage (Vcell_max) and its cell number among the voltages of the batteries b1 to b4, the minimum cell voltage (Vcell_min) and its cell number among the voltages of the batteries b1 to b4, and the average cell voltage (Vcell_ave) of the batteries b1 to b4 (step S13).

[0055] Next, the control unit 24 performs an adjustment process to adjust the remaining capacity of the batteries b1 to b4 (step S14). The adjustment process will now be described with reference to FIGS.

[0056] FIG. 7 is a diagram for explaining the adjustment process of the assembled battery equalizing device 18 according to the embodiment.

[0057] FIG. 8 is a diagram showing an example of adjustment processing during charging by the assembled battery equalization device 18 according to the embodiment.

[0058] FIG. 9 is a diagram showing an example of adjustment processing during discharge by the assembled battery equalizing device 18 according to the embodiment.

[0059] FIG. 10 is a diagram showing another example of the adjustment process during charging by the assembled battery equalization device 18 according to the embodiment.

[0060] FIG. 11 is a diagram showing another example of the adjustment process during discharge of the assembled battery equalizing device 18 according to the embodiment.

[0061] The SOC (State of Charge) shown in Figures 7 to 11 means the current capacity / current maximum capacity. Also, Cell 1 shown in Figures 8 to 11 is a degraded battery, and Cell 2 is a non-degraded battery. For example, if battery b3 of batteries b1 to b4 is a degraded battery, then battery b3 is Cell 1, and batteries b1, b2, and b4 are Cell 2.

[0062] As shown in the upper part of Figure 7, when the battery pack 2 is being charged, the control unit 24 performs adjustment processing so that the SOC of the degraded battery is lower than the SOC of the other batteries b1 to b4 when charging of the batteries b1 to b4 is completed.

[0063] As shown in the lower part of Figure 7, when the battery pack 2 is being discharged, the control unit 24 performs adjustment processing so that the SOC of the deteriorated battery is higher than the SOC of the other batteries b1 to b4 when the discharge of the batteries b1 to b4 is completed.

[0064] For example, as shown in Figure 8, if equalization is performed during the previous discharge to align the remaining capacities of batteries b1 to b4 to SOC_min, and then batteries b1 to b4 are charged, Cell 1, which is more deteriorated, has a smaller maximum capacity and therefore a larger increase in SOC than Cell 2, which is less deteriorated. Therefore, after charging of batteries b1 to b4 begins, the voltage of Cell 1, one of batteries b1 to b4, first reaches a predetermined voltage or higher, and equalization and adjustment processing begins. Specifically, equalization and adjustment processing are performed so that the SOC of Cell 1 becomes SOC_max1 and the SOC of Cell 2 becomes SOC_max2.

[0065] For example, the control unit 24 acquires the measurement results of the voltages of batteries b1 to b4 during charging, adds an offset voltage to the measurement result of Cell 1 during charging of batteries b1 to b4, and then aligns the measurement result of Cell 1's voltage with the measurement result of Cell 12's voltage after the charging of batteries b1 to b4 is completed, thereby performing an adjustment process so that the SOC of Cell 1 is lower than the SOC of Cell 2. For example, by adding 50 mV as an offset voltage to the measurement result of Cell 1's voltage, the voltage of Cell 1 is considered to be 50 mV higher than the actual voltage, and equalization is performed. Therefore, SOC_max1 at the completion of charging can be made 50 mV lower than SOC_max2. In this way, by adding an offset voltage to the measured Cell 1 voltage, an adjustment process can be performed so that the SOC of Cell 1 is lower than the SOC of Cell 2 at the completion of charging.

[0066] For example, as shown in Figure 9, if equalization is performed during the previous charge to align the remaining capacities of batteries b1 to b4 to SOC_max, and then batteries b1 to b4 are discharged, Cell 1, which is more deteriorated, has a smaller maximum capacity and therefore experiences a larger decrease in SOC than Cell 2, which is less deteriorated. Therefore, after batteries b1 to b4 start discharging, the voltage of Cell 1, one of batteries b1 to b4, drops below a predetermined voltage first, and equalization and adjustment processing begins. Specifically, equalization and adjustment processing are performed so that the SOC of Cell 1 becomes SOC_min1 and the SOC of Cell 2 becomes SOC_min2.

[0067] For example, the control unit 24 acquires the measurement results of the voltages of batteries b1 to b4 during discharge, subtracts an offset voltage from the measurement result of Cell 1 during discharge of batteries b1 to b4, and then, upon completion of discharge of batteries b1 to b4, aligns the measurement result of Cell 1's voltage from which the offset voltage has been subtracted with the measurement result of Cell 12, thereby performing an adjustment process so that the SOC of Cell 1 is higher than the SOC of Cell 2. For example, by subtracting 50 mV as an offset voltage from the measurement result of Cell 1's voltage, the voltage of Cell 1 is considered to be 50 mV lower than the actual voltage, and equalization is performed. Therefore, SOC_min1 at the completion of charging can be made 50 mV higher than SOC_min2. In this way, by subtracting the offset voltage from the measured Cell 1 voltage, an adjustment process can be performed so that the SOC of Cell 1 is higher than the SOC of Cell 2 at the completion of discharge.

[0068] In addition to the battery with the highest degree of degradation, a battery with the next highest degree of degradation may also be determined as a degraded battery, i.e., multiple degraded batteries may be determined. In this case, an offset voltage may be added to or subtracted from the measurement results of the voltages of the multiple degraded batteries. Furthermore, if the multiple degraded batteries have different degrees of degradation, the magnitude of the offset voltage to be added or subtracted may be adjusted depending on the degree of degradation.

[0069] As shown in Fig. 10, even if the equalization and adjustment processes were performed during the previous discharge and the remaining capacity of Cell 1 became SOC_min1 and the remaining capacity of Cell 2 became SOC_min2, charging is performed so that the SOC of Cell 1 becomes SOC_max1 and the SOC of Cell 2 becomes SOC_max2, as in the description of Fig. 8. Also, as shown in Fig. 11, even if the equalization and adjustment processes were performed during the previous charge and the remaining capacity of Cell 1 became SOC_max1 and the remaining capacity of Cell 2 became SOC_max2, discharging is performed so that the SOC of Cell 1 becomes SOC_min1 and the SOC of Cell 2 becomes SOC_min2, as in the description of Fig. 9.

[0070] In this way, when a degraded battery that is likely to experience accelerated degradation is charged, the remaining capacities of batteries b1 to b4 are adjusted so that the SOC of the degraded battery does not reach the upper limit of the SOC usage range. Alternatively, when a degraded battery that is likely to experience accelerated degradation is discharged, the remaining capacities of batteries b1 to b4 are adjusted so that the SOC of the degraded battery does not reach the lower limit of the SOC usage range. Therefore, the usable range of the SOC of the degraded battery can be narrowed, thereby suppressing the rate of degradation of the degraded battery.

[0071] Next, a method for determining whether a battery is degraded will be described.

[0072] For example, remaining charge capacity or remaining discharge capacity may be used to determine a degraded battery. Specifically, when the battery pack 2 is being charged, the monitoring unit 22 acquires, as degradation information, the remaining charge capacity of each of the batteries b1 to b4 after the start of charging of the batteries b1 to b4 and before the start of the adjustment process. Alternatively, when the battery pack 2 is being discharged, the monitoring unit 22 acquires, as degradation information, the remaining discharge capacity of each of the batteries b1 to b4 after the start of discharging of the batteries b1 to b4 and before the start of the adjustment process. Because there is a correlation between battery voltage and remaining battery capacity, the monitoring unit 22 can acquire the remaining charge capacity or remaining discharge capacity of each of the batteries b1 to b4 by acquiring the voltage of each of the batteries b1 to b4. Then, the control unit 24 determines, as the degraded battery, the battery with the highest remaining charge capacity or the lowest remaining discharge capacity among the batteries b1 to b4. The battery with the highest remaining charge capacity or the lowest remaining discharge capacity is the battery with the highest degree of deterioration among batteries b1 to b4, so the deterioration rate of deteriorated batteries with high remaining charge capacity or low remaining discharge capacity can be suppressed.

[0073] For example, the remaining capacity at the end of discharge may be used to determine a degraded battery. Specifically, the monitoring unit 22 acquires the remaining capacity at the end of discharge of each of the batteries b1 to b4 at the time of completion of discharge as degradation information. Because there is a correlation between the voltage of a battery and the remaining capacity of the battery, the monitoring unit 22 can acquire the remaining capacity at the end of discharge of each of the batteries b1 to b4 by acquiring the voltage of each of the batteries b1 to b4 at the time of completion of discharge. Note that the monitoring unit 22 may acquire the remaining capacity at the end of discharge by measuring the amount of charge transferred when a battery whose remaining capacity is the remaining capacity at the end of discharge is further discharged until the remaining capacity becomes zero. Then, the control unit 24 determines the battery with the smallest remaining capacity at the end of discharge among the batteries b1 to b4 as the degraded battery. Because the battery with the smallest remaining capacity at the end of discharge is the battery with the highest degree of degradation among the batteries b1 to b4, the degradation rate of the degraded battery with a small remaining capacity at the end of discharge can be suppressed.

[0074] For example, the SOH may be used to determine the degraded battery. Specifically, the monitoring unit 22 acquires the SOH of each of the batteries b1 to b4 as degradation information. The control unit 24 then determines the battery with the lowest SOH among the batteries b1 to b4 as the degraded battery. Because the battery with the lowest SOH is the battery with the highest degree of degradation among the batteries b1 to b4, the degradation rate of the degraded battery with a low SOH can be suppressed.

[0075] For example, the internal resistance of a battery may be used to determine a degraded battery. Specifically, the monitoring unit 22 acquires the internal resistance of each of the batteries b1 to b4 as degradation information. The control unit 24 then determines the battery with the highest internal resistance among the batteries b1 to b4 as the degraded battery. Because the battery with the highest internal resistance is the battery with the highest degree of degradation among the batteries b1 to b4, the degradation rate of the degraded battery with the high internal resistance can be suppressed.

[0076] For example, the temperature of the battery may be used to determine the degraded battery. Specifically, the monitoring unit 22 acquires the temperature of each of the batteries b1 to b4 as degradation information. The control unit 24 then determines the battery with the highest temperature among the batteries b1 to b4 as the degraded battery. Because the battery with the highest temperature is the battery with the highest degree of degradation among the batteries b1 to b4, the degradation rate of the degraded battery with the highest temperature can be suppressed.

[0077] For example, the maximum initial capacity of a battery (e.g., the maximum capacity of a battery at the time of shipment) may be used to determine a degraded battery. Specifically, the monitoring unit 22 acquires the maximum initial capacity of each of the batteries b1 to b4 as degradation information. The control unit 24 then determines the battery with the smallest maximum initial capacity among the batteries b1 to b4 as the degraded battery. The battery with the smallest maximum initial capacity has a high risk of degradation and a fast rate of degradation. In other words, the battery with the smallest maximum initial capacity is the battery with the highest possibility of future degradation among the batteries b1 to b4, and therefore the rate of degradation of the degraded battery with the smallest maximum initial capacity can be suppressed.

[0078] It should be noted that at least two of these methods for determining whether a battery is degraded may be used in combination.

[0079] Returning to the explanation of FIG. 6 , the control unit 24 determines whether the maximum cell voltage (Vcell_max) is lower than the full charge voltage (Vfull) and whether the minimum cell voltage (Vcell_min) is higher than the discharge cut-off voltage (Vcut) (step S15). For example, the full charge voltage is 4.2 V, and the discharge cut-off voltage is 2.5 V. If the control unit 24 determines that the maximum cell voltage is lower than the full charge voltage and that the minimum cell voltage is not higher than the discharge cut-off voltage (No in step S15), that is, if the maximum cell voltage is equal to or higher than the full charge voltage or the minimum cell voltage is equal to or lower than the discharge cut-off voltage, an abnormality may have occurred and the process is stopped.

[0080] If the control unit 24 determines that the maximum cell voltage is lower than the full charge voltage and that the minimum cell voltage is higher than the discharge end voltage (Yes in step S15), it determines whether equalization is necessary (step S16). For example, if the difference between the maximum cell voltage and the minimum cell voltage is equal to or greater than a predetermined value, the control unit 24 determines that equalization is necessary because the remaining capacities of the batteries b1 to b4 vary. For example, if the difference between the maximum cell voltage and the minimum cell voltage is less than a predetermined value, the control unit 24 determines that equalization is unnecessary (i.e., equalization is completed) because the remaining capacities of the batteries b1 to b4 are the same. If the control unit 24 determines that equalization is not necessary (No in step S16), it stops the process and starts the next charge or discharge at an arbitrary timing.

[0081] If the control unit 24 determines that equalization is necessary (Yes in step S16), it determines a target cell to be charged or discharged for equalization and determines whether to charge or discharge the target cell (step S17). For example, if the difference between the maximum cell voltage and the average cell voltage is equal to or greater than the difference between the minimum cell voltage and the average cell voltage, the control unit 24 determines the battery with the maximum cell voltage as the target cell and determines to discharge the target cell. For example, if the difference between the maximum cell voltage and the average cell voltage is smaller than the difference between the minimum cell voltage and the average cell voltage, the control unit 24 determines the battery with the minimum cell voltage as the target cell and determines to charge the target cell.

[0082] Next, the control unit 24 executes charging and discharging of the target cell (step S18). For example, the control unit 24 charges and discharges the target cell with a current equivalent to the charging current or discharging current of the battery pack 2, and stops the charging and discharging after a predetermined time (for example, several seconds to several tens of seconds).

[0083] The processes from step S13 to step S18 are then repeated until step S16 returns No, that is, until equalization is complete. As described above, since adjustment processing is also performed when equalization is performed, when equalization is complete and charging of batteries b1 to b4 is complete, the SOC of the degraded battery will be lower than the SOC of the other batteries, and when equalization is complete and discharging of batteries b1 to b4 is complete, the SOC of the degraded battery will be higher than the SOC of the other batteries. Therefore, the usable range of the SOC of the degraded battery can be narrowed, and the rate of deterioration of the degraded battery can be suppressed.

[0084] (Other Embodiments) As described above, the embodiments have been described as examples of the technology according to the present disclosure. However, the technology according to the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. For example, the following modifications are also included in one embodiment of the present disclosure.

[0085] For example, when charging of batteries b1 to b4 is completed, adjustment processing may be performed so that the SOC of the degraded battery is lower than the SOC of the other batteries, and when discharging batteries b1 to b4, adjustment processing may not be performed so that the SOC of the degraded battery is higher than the SOC of the other batteries. In other words, adjustment processing may be performed only when charging, and adjustment processing may not be performed when discharging. Alternatively, when discharging batteries b1 to b4, adjustment processing may be performed so that the SOC of the degraded battery is higher than the SOC of the other batteries, and when charging of batteries b1 to b4 is completed, adjustment processing may not be performed so that the SOC of the degraded battery is lower than the SOC of the other batteries. In other words, adjustment processing may be performed only when discharging, and adjustment processing may not be performed when charging.

[0086] For example, the present disclosure can be realized not only as the assembled battery equalization device 18, but also as an assembled battery equalization method including steps (processing) performed by the components (e.g., the monitoring unit 22 and the control unit 24) that make up the assembled battery equalization device 18.

[0087] FIG. 12 is a flowchart showing an example of a battery pack equalization method according to another embodiment.

[0088] The battery pack equalization method is a method executed by a battery pack equalization device 18 that equalizes the remaining capacities of multiple batteries connected in series, and as shown in FIG. 12 , includes an acquisition step (step S101) of acquiring deterioration information indicating the degree of deterioration of each of the multiple batteries, a determination step (step S102) of determining, based on the deterioration information, a deteriorated battery that is the battery with the highest degree of deterioration among the multiple batteries, and an adjustment step (step S103) of performing an adjustment process to adjust the remaining capacities of the multiple batteries. In the adjustment step, the adjustment process is performed so that the SOC of the deteriorated battery is lower than the SOC of the other batteries among the multiple batteries when charging of the multiple batteries is complete, or so that the SOC of the degraded battery is higher than the SOC of the other batteries when discharging of the multiple batteries is complete.

[0089] For example, the present disclosure can be realized as a program for causing a computer (processor) to execute the steps included in the battery pack equalization method. Furthermore, the present disclosure can be realized as a non-transitory computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0090] For example, when the present disclosure is realized as a program (software), each step is performed by running the program using hardware resources such as a computer's CPU, memory, input / output circuits, etc. In other words, each step is performed by the CPU acquiring data from memory or input / output circuits, etc., performing calculations, and outputting the calculation results to memory or input / output circuits, etc.

[0091] In the above embodiment, each component included in the assembled battery equalization device 18 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.

[0092] Some or all of the functions of the assembled battery equalization device 18 according to the above embodiment are typically realized as an LSI, which is an integrated circuit. These may be individually implemented as single chips, or some or all of them may be integrated into a single chip. Furthermore, the integrated circuit is not limited to an LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array), which can be programmed after LSI manufacturing, or a reconfigurable processor, which can reconfigure the connections and settings of circuit cells within an LSI, may also be used.

[0093] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, that technology may naturally be used to integrate the components included in the battery pack equalization device 18 into integrated circuits.

[0094] In addition, this disclosure also includes forms obtained by making various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope that does not deviate from the intent of this disclosure.

[0095] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0096] (Technology 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, the battery pack equalization device comprising: an acquisition unit that acquires deterioration information indicating the degree of deterioration of each of the plurality of batteries; a determination unit that determines a deteriorated battery that is the battery of the plurality of batteries that has the highest degree of deterioration based on the deterioration information; and an adjustment unit that performs an adjustment process to adjust the remaining capacities of the plurality of batteries, wherein the adjustment unit performs the adjustment process so that the SOC of the deteriorated battery is lower than the SOC of other batteries of the plurality of batteries when charging of the plurality of batteries is completed, or performs the adjustment process so that the SOC of the degraded battery is higher than the SOC of the other batteries when discharging of the plurality of batteries is completed.

[0097] According to this, when a degraded battery that is likely to experience accelerated degradation is charged, the remaining capacities of the multiple batteries are adjusted so that the SOC of the degraded battery does not reach the upper limit of the SOC usage range. Alternatively, when a degraded battery that is likely to experience accelerated degradation is discharged, the remaining capacities of the multiple batteries are adjusted so that the SOC of the degraded battery does not reach the lower limit of the SOC usage range. Therefore, the usage range of the SOC of the degraded battery can be narrowed, thereby suppressing the rate of degradation of the degraded battery.

[0098] (Technology 2) In the battery pack equalization device described in Technology 1, the acquisition unit acquires, as the degradation information, the remaining charge capacity of each of the plurality of batteries after the start of charging of the plurality of batteries and before the start of the adjustment process, or the remaining discharge capacity of each of the plurality of batteries after the start of discharging of the plurality of batteries and before the start of the adjustment process, and the determination unit determines, as the degraded battery, the battery of the plurality of batteries with the highest remaining charge capacity or the lowest remaining discharge capacity.

[0099] According to this, the battery with the highest remaining capacity when charging or the battery with the lowest remaining capacity when discharging is the battery with the highest degree of deterioration among the multiple batteries, so the deterioration rate of deteriorated batteries with high remaining capacity when charging or low remaining capacity when discharging can be suppressed.

[0100] (Technology 3) In the battery pack equalization device described in Technology 1 or 2, the acquisition unit acquires, as the degradation information, the remaining capacity at the time of discharge completion of each of the plurality of batteries when discharge of the plurality of batteries is completed, and the determination unit determines, as the degraded battery, the battery among the plurality of batteries with the smallest remaining capacity at the time of discharge completion.

[0101] According to this, the battery with the least remaining capacity at the end of discharge is the battery with the highest degree of degradation among the plurality of batteries, and therefore the rate of degradation of degraded batteries with low remaining capacity at the end of discharge can be suppressed.

[0102] (Technology 4) The battery pack equalization device described in any one of Technologies 1 to 3, wherein the acquisition unit acquires the SOH of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the lowest SOH among the plurality of batteries as the degraded battery.

[0103] According to this, the battery with the lowest SOH is the battery with the highest degree of degradation among the plurality of batteries, and therefore the rate of degradation of the degraded battery with a low SOH can be suppressed.

[0104] (Technology 5) A battery pack equalization device according to any one of Technologies 1 to 4, wherein the acquisition unit acquires the internal resistance of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the highest internal resistance among the plurality of batteries as the degraded battery.

[0105] According to this, the battery with the highest internal resistance is the battery with the highest degree of degradation among the plurality of batteries, and therefore the rate of degradation of the degraded battery with high internal resistance can be suppressed.

[0106] (Technology 6) The battery pack equalization device described in any one of Technologies 1 to 5, wherein the acquisition unit acquires the temperature of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the highest temperature among the plurality of batteries as the degraded battery.

[0107] According to this, the battery with the highest temperature is the battery with the highest degree of degradation among the plurality of batteries, and therefore the rate of degradation of the degraded battery with the highest temperature can be suppressed.

[0108] (Technology 7) A battery pack equalization device according to any one of Technologies 1 to 6, wherein the acquisition unit acquires the maximum initial capacity of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the smallest maximum initial capacity among the plurality of batteries as the degraded battery.

[0109] According to this, since the battery with the smallest maximum initial capacity is the battery that is most likely to deteriorate in the future among the plurality of batteries, the deterioration rate of the deteriorated battery with the smallest maximum initial capacity can be suppressed.

[0110] (Technology 8) The battery pack equalization device according to any one of Techniques 1 to 7, wherein the adjustment unit acquires measurement results of the voltages of the plurality of batteries when the plurality of batteries are being charged or discharged, adds an offset voltage to the measurement result of the voltage of the degraded battery when the plurality of batteries are being charged, and subtracts the offset voltage from the measurement result of the voltage of the degraded battery when the plurality of batteries are being discharged, and performs the adjustment process by aligning the measurement result of the voltage of the degraded battery to which the offset voltage has been added and the measurement results of the voltages of the other batteries when charging of the plurality of batteries is completed, so that the SOC of the degraded battery is lower than the SOC of the other batteries, or by aligning the measurement result of the voltage of the degraded battery from which the offset voltage has been subtracted and the measurement results of the voltages of the other batteries when discharging of the plurality of batteries is completed, so that the SOC of the degraded battery is higher than the SOC of the other batteries.

[0111] According to this, by adding or subtracting the offset voltage to or from the measured voltage of the deteriorated battery, an adjustment process can be performed so that the SOC of the deteriorated battery is lower or higher than the SOC of other batteries.

[0112] (Technology 9) A battery pack equalization method executed by a battery pack equalization device that equalizes the remaining capacities of a plurality of batteries connected in series, the battery pack equalizing method including: an acquisition step of acquiring deterioration information indicating a degree of deterioration of each of the plurality of batteries; a determination step of determining a deteriorated battery among the plurality of batteries that is the battery with the highest degree of deterioration based on the deterioration information; and an adjustment step of performing an adjustment process to adjust the remaining capacities of the plurality of batteries, wherein the adjustment step performs the adjustment process so that, when charging of the plurality of batteries is completed, the SOC of the deteriorated battery is lower than the SOC of other batteries among the plurality of batteries, or so that, when discharging of the plurality of batteries is completed, the SOC of the degraded battery is higher than the SOC of the other batteries.

[0113] This makes it possible to provide a battery pack equalization method that can suppress the rate of deterioration of deteriorated batteries.

[0114] The present disclosure can be applied to devices that equalize the remaining capacity of multiple batteries connected in series.

[0115] 2 assembled battery 4 load 6A, 6B, 14A, 14B relay 8 external power supply 10 AC power supply 12 conversion section 16 ammeter 18 assembled battery equalization device 20 equalization processing circuit 22 monitoring section 24 control section 32 capacitor 34 non-insulated DC / DC converter 36 insulated DC / DC converter b1 to b4 batteries R1 to R4 resistors SWa to SWm changeover switches V1 to V4 voltmeter

Claims

1. A battery pack equalization device that equalizes the remaining capacity of multiple batteries connected in series, comprising: an acquisition unit that acquires deterioration information indicating the degree of deterioration of each of the multiple batteries; a determination unit that determines, based on the deterioration information, a deteriorated battery among the multiple batteries that is the battery with the highest degree of deterioration; and an adjustment unit that performs adjustment processing to adjust the remaining capacities of the multiple batteries, wherein the adjustment unit performs the adjustment processing so that, when charging of the multiple batteries is complete, the SOC (State of Charge) of the deteriorated battery is lower than the SOC of the other batteries among the multiple batteries, or performs the adjustment processing so that, when discharging of the multiple batteries is complete, the SOC of the deteriorated battery is higher than the SOC of the other batteries.

2. The battery pack equalization device of claim 1, wherein the acquisition unit acquires, as the degradation information, the remaining charge capacity of each of the plurality of batteries after the start of charging of the plurality of batteries and before the start of the adjustment process, or the remaining discharge capacity of each of the plurality of batteries after the start of discharging of the plurality of batteries and before the start of the adjustment process, and the determination unit determines, as the deteriorated battery, the battery of the plurality of batteries with the highest remaining charge capacity or the lowest remaining discharge capacity.

3. The battery pack equalization device according to claim 1, wherein the acquisition unit acquires, as the degradation information, the remaining capacity at the time of discharge completion of each of the plurality of batteries, and the determination unit determines, as the degraded battery, the battery among the plurality of batteries with the smallest remaining capacity at the time of discharge completion.

4. The battery pack equalization device according to claim 1, wherein the acquisition unit acquires the SOH (State of Health) of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the lowest SOH among the plurality of batteries as the degraded battery.

5. The battery pack equalization device according to claim 1, wherein the acquisition unit acquires the internal resistance of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the highest internal resistance among the plurality of batteries as the degraded battery.

6. The battery pack equalization device according to claim 1, wherein the acquisition unit acquires the temperature of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the highest temperature among the plurality of batteries as the degraded battery.

7. The battery pack equalization device according to claim 1, wherein the acquisition unit acquires the maximum initial capacity of each of the plurality of batteries as the degradation information, and the determination unit determines the battery with the smallest maximum initial capacity among the plurality of batteries as the degraded battery.

8. The battery pack equalization device according to any one of claims 1 to 7, wherein the adjustment unit: acquires measurement results of the voltages of the multiple batteries when the multiple batteries are being charged or discharged; adds an offset voltage to the measurement result of the voltage of the degraded battery when the multiple batteries are being charged; subtracts the offset voltage from the measurement result of the voltage of the degraded battery when the multiple batteries are being discharged; and performs the adjustment process when charging of the multiple batteries is complete, by aligning the measurement result of the voltage of the degraded battery to which the offset voltage has been added and the measurement results of the voltages of the other batteries, so that the SOC of the degraded battery is lower than the SOC of the other batteries; or performs the adjustment process when discharging of the multiple batteries is complete, by aligning the measurement result of the voltage of the degraded battery from which the offset voltage has been subtracted and the measurement results of the voltages of the other batteries, so that the SOC of the degraded battery is higher than the SOC of the other batteries.

9. A battery pack equalization method executed by a battery pack equalization device that equalizes the remaining capacity of a plurality of batteries connected in series, comprising: an acquisition step of acquiring deterioration information indicating the degree of deterioration of each of the plurality of batteries; a determination step of determining, based on the deterioration information, a deteriorated battery that is the battery with the highest degree of deterioration among the plurality of batteries; and an adjustment step of performing an adjustment process to adjust the remaining capacities of the plurality of batteries, wherein in the adjustment step, the adjustment process is performed so that, when charging of the plurality of batteries is completed, the SOC of the deteriorated battery is lower than the SOC of the other batteries among the plurality of batteries; or, when discharging of the plurality of batteries is completed, the adjustment process is performed so that the SOC of the degraded battery is higher than the SOC of the other batteries.

Images