Capacity adjustment device and capacity adjustment method

Abstract

This capacity adjustment device for adjusting capacities of a plurality of cells included in a battery pack comprises: a CPU 10 that detects an amount of variation in capacity of a plurality of cells C, selects an adjustment cell to be subjected to capacity adjustment from among the plurality of cells C on the basis of the detected amount of variation, and calculates a discharge target amount of the adjustment cell; and an ASIC 20 that outputs a discharge instruction to discharge the adjustment cell and discharges the adjustment cell. The CPU 10 executes selection processing of the adjustment cell and calculation processing of the discharge target amount before processing by the CPU 10 stops. The ASIC 20 discharges the adjustment cell so that an actual discharge amount of the adjustment cell reaches the discharge target amount while the processing of the CPU 10 is stopped.

Description

Capacity adjustment device and capacity adjustment method

[0001] The present invention relates to a capacity adjustment device and a capacity adjustment method for adjusting the capacity of multiple cells.

[0002] The cell balancing device described in Patent Document 1 includes a capacity adjustment circuit that can adjust the capacity of each battery cell by including a plurality of series-connected switch elements and resistors connected in parallel to each battery cell, a processor, and a watchdog unit that monitors the processor and resets the processor if it malfunctions. The processor acquires the voltage of the battery cells from the voltage detection circuit in the normal state, transitions to a sleep state when the vehicle ignition is turned off, reads out the voltage of the battery cells stored in the memory unit in the sleep state, and controls the switch elements to adjust the capacity of each battery cell.

[0003] Japanese Patent Publication No. 2010-124094

[0004] However, the above-mentioned cell balancing device has a problem in that it cannot adjust the capacity of the battery cells while the processor is in sleep mode, because it selects the cells to be discharged based on the voltage of the battery cells and performs the actual discharge process in a sleep state.

[0005] The problem that this invention aims to solve is to provide a capacity adjustment device and a capacity adjustment method that enable capacity adjustment while the processor is stopped.

[0006] The present invention solves the above problem by performing a process to select an adjustment cell based on the detected variation amount and a process to calculate the discharge target amount of the adjustment cell before the CPU processing stops, and by performing the discharge of the adjustment cell so that the discharge amount of the adjustment cell reaches the discharge target amount while the CPU processing is stopped.

[0007] According to the present invention, capacity adjustment is possible while the processor is stopped.

[0008] Figure 1 is a block diagram showing the capacity adjustment system according to this embodiment. Figure 2 is a graph showing the cell voltage, variation amount, discharge target amount, and discharge instruction for each of the multiple cells. Figure 3 is a flowchart showing the procedure of the capacity adjustment method according to this embodiment. Figure 4 is a table showing an example of the switch on and off sequence. Figure 5 is a graph showing the cell voltage, variation amount, discharge target amount, and discharge instruction for each of the multiple cells. Figure 6 is a graph showing the cell voltage, variation amount, discharge target amount, and discharge instruction for each of the multiple cells.

[0009] A capacity adjustment system 100 according to this embodiment will be described with reference to the drawings. Fig. 1 is a block diagram showing the capacity adjustment system according to this embodiment.

[0010] As shown in Figure 1, the capacity adjustment system 100 comprises a CPU 10, an ASIC 20, a discharge circuit 30, and a battery pack 40. The capacity adjustment system 100 is installed in a vehicle. The device including the CPU 10 and ASIC 20 corresponds to the "capacity adjustment device" of the present invention. Furthermore, the CPU 10 corresponds to the "processing unit" of the present invention, and the ASIC 20 corresponds to the "integrated circuit" of the present invention.

[0011] The battery pack 40 has multiple cells C1 to C8. In the example in Figure 1, the battery pack 40 has eight cells. In the following description, the eight cells C1 to C8 included in the battery pack 40 will be collectively referred to as cell C. Similarly, the eight switches S1 to S8 included in the ASIC 20 will be collectively referred to as switch S. The number of cells C included in the battery pack 40 is not limited to eight; it can be any number. Cell C is a lithium-ion secondary battery. Examples of lithium-ion secondary batteries include, for example, those using silicon or a silicon-containing active material as the negative electrode active material, or those using a sulfur-containing active material as the positive electrode active material. Cell C may also be an electrolyte lithium-ion secondary battery or an all-solid-state lithium-ion secondary battery. Furthermore, cell C is not limited to a lithium-ion secondary battery; it may also be a lead-acid battery. Multiple cells B are connected in series. Multiple cells B may also be connected in parallel, or a combination of series and parallel connections may be used.

[0012] The CPU 10 is a central processing unit that monitors the states of the plurality of cells (battery cells) included in the battery pack 40, detects variations in the plurality of cells C, and executes calculations required to adjust for the variations.

[0013] The CPU 10 switches between executing and stopping arithmetic processing based on a system start request signal transmitted in response to the on and off state of the vehicle's main switch (ignition switch). That is, when the vehicle's main switch is switched from off to on, the CPU 10 starts up and executes various processes within the CPU 10. When the vehicle's main switch is switched from on to off, the CPU 10 shuts down and stops various processes within the CPU 10. The CPU 10 may also start and stop itself at predetermined time intervals from a system shutdown state (processing within the CPU 10 stopped). The CPU 10 receives power from the vehicle's low-voltage battery (e.g., 12V battery, auxiliary battery). When the vehicle's main switch is switched from on to off, the power supply from the low-voltage battery to the CPU 10 is interrupted, causing the CPU 10 to shut down.

[0014] The CPU 10 detects the cell voltages of the cells C and the currents flowing through the cells C by acquiring the detected voltages of the cells C and the detected currents of the battery pack 40 from a voltage sensor connected to the cells C and a current sensor connected to the battery pack 40. The CPU 10 also calculates the battery capacities (remaining capacity, full charge capacity) of the cells C based on the detected voltages and / or currents of the cells C. For example, the CPU 10 calculates the battery capacity of the cells C from an integrated value of the detected currents, or calculates the SOC based on the detected voltages of each cell C. The CPU 10 may also calculate the degradation level of each cell C. Note that the battery capacities, SOC, and degradation levels of the cells C may be calculated using a calculation method publicly known at the time of filing of this application. Thus, the CPU 10 monitors the status of the cells C based on the detected values ​​of the voltage sensor and / or the current sensor.

[0015] The CPU 10 has a function of detecting the amount of variation in the capacity of the plurality of cells C, and a function of selecting an adjustment cell based on the detected amount of variation and calculating a target discharge amount for the adjustment cell. The adjustment cell is a cell that is the target of capacity adjustment from the plurality of cells C. The CPU 10 has a variation amount detection unit 11 and a target discharge amount calculation unit 12 as functional blocks that execute each function. Note that the CPU 10 is not limited to the functions of the variation amount detection unit 11 and the target discharge amount calculation unit 12, and may have other functions. The number of functional blocks included in the CPU 10 is not limited to two as shown in FIG. 1 , but may be one, three, or more.

[0016] The variation amount detection unit 11 detects the amount of variation in the capacity of the multiple cells B based on the cell voltages of the multiple cells C. The amount of variation corresponds to the voltage difference between the cell voltages. The variation amount detection unit 11 identifies the smallest cell voltage among the cell voltages and calculates the difference between the smallest cell voltage and each of the other cell voltages. FIG. 2 is a graph showing the cell voltages, amount of variation, target discharge amount, and discharge instruction for each of the multiple cells C. Note that the cell numbers "1" to "8" indicate the order in which the multiple cells are arranged, with cell 1 corresponding to cell C1 and cells 2 to 8 corresponding to cells C2 to C8.

[0017] In the example of Fig. 2, the variation amount detection unit 11 calculates the voltage difference between the cell voltage of cell C3, which has the smallest cell voltage, and each of the cell voltages of cells C1, C2, C4 to C8. In the example of Fig. 2, the voltage difference between cell C1 and cell C3 is the largest, so the variation amount of cell C1 is the largest. Note that the variation amount detection unit 11 is not limited to the voltage difference between multiple cells C, but may also calculate the difference in remaining capacity between each cell C and detect the calculated difference in remaining capacity as the variation amount.

[0018] The discharge target amount calculation unit 12 selects an adjustment cell from among the plurality of cells C based on the amount of variation detected by the variation amount detection unit 11. The discharge target amount calculation unit 12 selects the cell C with the largest amount of variation from among the plurality of cells C. In the example of FIG. 2 , the discharge target amount calculation unit 12 selects cell C1 as the adjustment cell. The discharge target amount calculation unit 12 also selects an adjustment cell from the cells C other than cell C1. The discharge target amount calculation unit 12 may select an adjustment cell such that the number of adjacent cells that are subject to capacity adjustment is equal to or less than a predetermined number. The predetermined number indicates the upper limit (upper limit number) of the number of adjacent cells that are subject to capacity adjustment.

[0019] As shown in FIG. 1 , multiple switches S1 to S8 are connected in parallel to multiple cells C1 to C8, and multiple resistors R are connected between the multiple cells C1 to C8 and the multiple switches S1 to S8. For example, when switch S1 is turned on, a closed circuit including cell C1, switch S1, and multiple resistors R becomes electrically conductive, allowing a discharge current to flow. When an adjacent switch S is turned on, the discharge current increases as the number of series-connected cells C in the electrically conductive closed circuit increases. Furthermore, the inrush current flowing immediately after switch S is turned on increases as the number of series-connected cells C increases. In this embodiment, to prevent a large inrush current from flowing during capacity adjustment, a maximum number of adjacent cells that are subject to capacity adjustment is predetermined. The maximum number is determined based on the withstand voltage of the circuitry within the ASIC 20 when discharging a cell C. In the example of FIG. 2 , the maximum number is set to "2."

[0020] Cell C2 is adjacent to cell C1, which has already been determined as the adjustment cell, and the variation amount of cell C2 is greater than zero. Therefore, the discharge target amount calculation unit 12 selects cell C2 as the adjustment cell. Since the variation amount of cell C3 is zero, it is not subject to capacity adjustment. Since the variation amounts of cells C4 and C5 are greater than zero and the number of adjacent cells is less than or equal to the upper limit, the discharge target amount calculation unit 12 selects cells C4 and C5 as adjustment cells. Although the variation amount of cell C6 is greater than zero, if cell C6 were to be the adjustment cell, the number of adjacent cells would exceed the upper limit, so the discharge target amount calculation unit 12 does not select cell C6 as the adjustment cell. Since the variation amounts of cells C7 and C8 are greater than zero and the number of adjacent cells is less than or equal to the upper limit, the discharge target amount calculation unit 12 selects cells C7 and C8 as adjustment cells. As a result, the discharge target amount calculation unit 12 selects adjustment cells that are subject to capacity adjustment and whose number of adjacent cells is less than or equal to a predetermined number.

[0021] The discharge target amount calculation unit 12 calculates a discharge target amount based on the amount of variation detected by the variation amount detection unit 11. The discharge target amount is calculated, for example, by multiplying the voltage difference corresponding to the amount of variation by a predetermined value, and is expressed as a discharge time. The predetermined value is a value determined in advance depending on the resistance value of the resistor R included in the discharge circuit 30 and the discharge current flowing through the discharge circuit 10 and the ASIC 20 when cell B is discharged, and corresponds to the rate of decrease in the cell voltage due to the discharge of cell B. The discharge target amount may also be the difference in remaining capacity of cell C (current capacity: Ah).

[0022] In the example of FIG. 2, the discharge target amount calculation unit 12 calculates the discharge target amount for each of the cells C1, C2, C4, C5, C7, and C8 selected as the adjustment cells.

[0023] Before shutting down, the CPU 10 executes processing by the variation amount detection unit 11 and processing by the discharge target amount calculation unit 12, and transmits to the ASIS 20 the selection information of the cell C selected as the adjustment cell and a signal including the discharge target amount of the adjustment cell.

[0024] ASIC20 is an integrated circuit used for discharging cells, and it discharges the adjustment cells by outputting a discharge instruction to discharge the adjustment cells. ASIC20 has a plurality of switches S1 to S8. The plurality of switches S1 to S8 correspond one-to-one with cells C1 to C8. The switching instruction for switching switches S1 to S8 on and off corresponds to the discharge instruction for discharging the adjustment cells.

[0025] The ASIC20 obtains power from the battery pack 40. Even when the vehicle's main switch is turned from on to off, the ASIC20 can still obtain power from the battery pack 40. The ASIC20 can continue to control the on and off switching of switches S1 to S8 even after the vehicle's main switch has been turned from on to off. For example, the ASIC20 has channels corresponding to the number of cells in cell C, and the ASIC20 is designed to repeatedly turn switches S on and off at a predetermined cycle for each channel. The ASIC20 allows setting the time for each channel to turn on switch S. For example, to turn on switch S1, the on time for switch S1 should be set to a predetermined time, and to turn off switch S1, the on time for switch S1 should be set to zero. When the vehicle's main switch is turned off, the ASIC20 repeatedly turns switches S on and off at a predetermined cycle so that the time that switch S is on becomes the set on time. In other words, the longer the set on time, the more times switch S will switch on and off. As described above, when the vehicle's main switch is turned from on to off, the CPU 10 shuts down. In other words, the ASIC 20 can discharge the regulating cell while the CPU 10 is shut down.

[0026] The ASIC 20 has a discharge instruction output unit 21 as a functional block for executing the discharge instruction output function. The ASIC 20 may have other functions besides the discharge instruction output unit 21, and the number of functional blocks included in the CPU 10 is not limited to one, as shown in Figure 1, but may be two or more.

[0027] When the discharge instruction output unit 21 receives a signal from the CPU 10 that includes the selection information of the adjustment cell and the target discharge amount of the adjustment cell, it stores the received information in the memory of the ASIC 20. When the vehicle's main switch is turned off, the discharge instruction output unit 21 retrieves the selection information of the adjustment cell and the target discharge amount of the adjustment cell from the memory. The discharge instruction output unit 21 outputs a discharge instruction to the switch S corresponding to the adjustment cell so that the switch S is turned on for a discharge time corresponding to the target discharge amount. On the other hand, the discharge instruction output unit 21 does not output a discharge instruction to a switch S that does not correspond to an adjustment cell. The discharge instruction corresponds to an ON command that switches the switch S to ON.

[0028] In the example shown in Figure 2, the adjustment cells are cells C1, C2, C4, C5, C7, and C8. Switches S1, C2, C4, C5, C7, and C8 corresponding to the adjustment cells are turned on, while switches S3 and S6, which do not correspond to the adjustment cells, remain in the off state. When the on time of switches S1, C2, C4, C5, C7, and C8 reaches the discharge time corresponding to the discharge target amount, the discharge instruction output unit 21 turns off switches S1, C2, C4, C5, C7, and C8. As a result, the discharge instruction output unit 21 performs discharge of the adjustment cells so that the discharge amount of the adjustment cells reaches the discharge target amount while the CPU 10 is stopped processing. The discharge amount is the battery capacity actually discharged from cell S.

[0029] If the discharge target amount is calculated based on the difference in remaining capacity (current capacity: Ah) of cell C, the discharge instruction output unit 21 may calculate the on-time of switch S by converting the difference in remaining capacity into the discharge time of cell C, and turn on switch S for the calculated on-time. In other words, the discharge instruction output unit 21 may determine that the discharge amount has reached the discharge target amount by turning on switch S for the calculated discharge time, without calculating the discharge amount during the discharge of cell C. When calculating the discharge amount during the discharge of cell C, the discharge instruction output unit 21 may calculate the discharge amount from, for example, the integrated value of the discharge current.

[0030] The discharge circuit 30 has a plurality of resistors R, which are provided on lines connecting the positive and negative terminals of the cells C to both ends of the switch S. The number of resistors R may be any number depending on the number of cells C. The battery pack 40 has a plurality of cells C. The battery pack 40 is a high-voltage battery that serves as a power source for the vehicle motor, etc. The voltage of the battery pack 40 is higher than the voltage of the low-voltage battery for auxiliary equipment.

[0031] A capacity adjustment method using the capacity adjustment system according to this embodiment will be described with reference to FIG. 3 . FIG. 3 is a flowchart showing the steps of the capacity adjustment method. The CPU 10 executes the following control flow, steps S1 to S3, while the vehicle's main switch is on. In step S1, the CPU 10 detects the amount of variation in the capacities of the multiple cells C based on the cell voltages of the multiple cells C. In step S2, the CPU 10 selects an adjustment cell from the multiple cells C based on the amount of variation. In step S3, the CPU 10 calculates a target discharge amount for the adjustment cell based on the amount of variation. The CPU 10 also transmits a signal including adjustment cell selection information and the target discharge amount for the adjustment cell to the ASIS 20. In step S4, if the CPU 10 has shut down due to a command to operate the vehicle's main switch, the process proceeds to Yes in the determination flow of step S4. If the CPU 10 has not shut down, the process proceeds to No in the determination flow of step S4. Note that if the CPU 10 has not shut down, the CPU 10 may execute the control flow of steps S1 to S3 again.

[0032] In step S5, the ASIC 20 outputs a discharge instruction to turn on the switch S corresponding to the adjustment cell. In step S6, the ASIC 20 determines whether the on-time of the switch S has exceeded the discharge time corresponding to the target discharge amount. If the on-time of the switch S has not exceeded the discharge time, the ASIC 20 continues discharging the cell C. If the on-time of the switch S has exceeded the discharge time, the ASIC 20 switches the switch S from on to off in step S7. The ASIC 20 executes the control flow of steps S5 to S7 for each of the multiple switches S corresponding to the multiple adjustment cells. Then, when the on-time of all the switches S has exceeded the discharge time, the discharging of the multiple cells C ends, and the control flow shown in FIG. 3 ends.

[0033] Note that the adjustment cell should be discharged once per trip. That is, the control flow of steps S5 to S7 is executed once per trip for each of the multiple switches S corresponding to the multiple adjustment cells. One trip is the period from when the vehicle's main switch is turned off until the main switch is next turned on, and corresponds to the time the vehicle is parked. In the example of FIG. 2, cells S1, 2, 4, 5, 7, and 8 are discharged during the current trip, and after cells S1, 2, 4, 5, 7, and 8 have finished discharging, cells S1, 2, 4, 5, 7, and 8 are not discharged during the same current trip. Furthermore, cells S3 and S6 are not selected as adjustment cells, so they are not discharged during the current trip.

[0034] As described above, in this embodiment, the CPU 10 detects the amount of variation in the capacities of the multiple cells C, selects an adjustment cell to be subjected to capacity adjustment from the multiple cells C based on the detected amount of variation, and calculates the target discharge amount of the adjustment cell. The ASIC 20 outputs a discharge instruction to discharge the adjustment cell, thereby discharging the adjustment cell. Before processing by the CPU 10 is stopped, the CPU 10 executes the adjustment cell selection process and the calculation process of the target discharge amount. While processing by the CPU 10 is stopped, the ASIC 20 executes the discharge of the adjustment cell so that the amount of discharge of the adjustment cell reaches the target discharge amount.

[0035] Furthermore, in the capacity adjustment method according to this embodiment, the steps executed by the CPU 10 include a step of detecting the amount of variation in the capacity of a plurality of cells C, a selection step of selecting an adjustment cell from the plurality of cells C based on the detected amount of variation, and a calculation step of calculating the discharge target amount of the adjustment cell. The steps executed by the ASIC 20 include a discharge step of outputting a discharge instruction to the adjustment cell and discharging the adjustment cell so that the discharge amount of the adjustment cell reaches the discharge target amount. The selection step and the calculation step are executed before processing by the processing unit stops, and the discharge step is executed while processing by the processing unit is stopped. Steps S2 and S3 correspond to the selection step and the calculation step, and steps S5 to S7 correspond to the discharge step.

[0036] This allows for capacitance adjustment while the CPU 10 system is stopped, with the on / off state of the capacitance adjustment switch S fixed. Furthermore, when adjusting the capacitance of cell C while the CPU 10 system is stopped, the ASIC 20 can fix the on / off state of switch S. For example, if switch S, which should remain in the off state as it is not to be adjusted, is accidentally turned on, and a large number of adjacent cells C become electrically connected, there is a risk of a large inrush current flowing. In this embodiment, since the on / off state of the capacitance adjustment switch S is fixed while the CPU 10 system is stopped, a large inrush current can be prevented, and the load on the circuit inside the ASIC 20 can be suppressed.

[0037] Furthermore, the CPU 10 is subject to capacity adjustment, and it selects adjustment cells so that the number of adjacent cells is less than or equal to a predetermined number. This ensures flexibility in the combination of cell numbers that are allowed to discharge. In addition, the load applied to the circuit within the ASIC 20 during cell discharge can be kept below the circuit's withstand voltage.

[0038] In this embodiment, the CPU 10 selects the cell with the largest variation as the adjustment cell. This allows the cell C with the largest variation to be discharged preferentially. As a result, the cell C that needs capacity adjustment can be adjusted early.

[0039] In this embodiment, the ASIC 20 switches on and off the current flowing through the discharge circuit 30, has multiple switches S connected to multiple cells C, switches on and off the switches S connected to the adjustment cells, and maintains the switches S connected to cells C not selected as adjustment cells in an off state during the discharge of the adjustment cells. For example, the ASIC 20 is configured to repeatedly turn on and off the switches S for each channel at a predetermined cycle. When cells C2, C4, C6, and C8 are selected as adjustment cells, the ASIC 20 controls the switches S1 to S8 in the sequence shown in the table of FIG. 4. Note that in the example of FIG. 4, for simplicity's sake, the number of times the switches S2, S4, S6, and S8 are turned on and off is the same, but the actual number of times varies depending on the target discharge amounts of cells C2, S4, S6, and S8. 4, even if switches S2, 4, 6, and 8 are turned on, switches S1, 3, 5, and 7 are maintained in the off state, so that a large number of adjacent cells C are not electrically connected within one trip. As a result, the on / off state of the capacity adjustment switch S is fixed while the CPU 10 system is stopped, preventing a large inrush current from flowing and suppressing the load on the circuitry within the ASIC 20.

[0040] As a first modification of this embodiment, the CPU 10 may select an even-numbered or odd-numbered cell in the arrangement order of the multiple cells as the adjustment cell. FIG. 5 is a graph showing the cell voltages, variations, target discharge amounts, and discharge instructions for each of the multiple cells C. The cell voltages and variations of the multiple cells C shown in FIG. 5 are the same as those of the multiple cells C shown in FIG. 2. The target discharge amount calculation unit 12 of the CPU 10 selects the even-numbered cells C as the adjustment cells. In the example of FIG. 5, the target discharge amount calculation unit 12 selects cells C2, C4, C6, and C8 as adjustment cells. If the variation amount of an even-numbered cell C is zero, the cell is excluded from capacity adjustment. The target discharge amount calculation unit 12 calculates the target discharge amounts of cells C2, C4, C6, and C8 based on the variations of cells C2, C4, C6, and C8. Before shutting down, the CPU 10 transmits a signal to the ASIS 20 containing information on the selection of cells C2, 4, 6, and 8 and the target discharge amount of the adjustment cell. While the CPU 10 is stopped, the ASIS 20 turns on switches S2, 4, 6, and 8 to discharge the adjustment cells (cells C2, 4, 6, and 8) so that the actual discharge amount of the adjustment cells reaches the target discharge amount. After the adjustment cells are discharged, the vehicle's main switch is turned on, and the CPU 10 starts up. The target discharge amount calculation unit 12 selects the odd-numbered cell C as the adjustment cell. That is, if the even-numbered cell C was selected as the adjustment cell during the previous startup of the CPU 10, the odd-numbered cell C is selected as the adjustment cell during the current startup of the CPU 10. The ASIS 20 then discharges the odd-numbered cell C in the same manner as the even-numbered cell C. This prevents adjacent cells C from being discharged at the same time, preventing a large inrush current from flowing and reducing the load on the circuitry within the ASIC 20 .

[0041] In the modified example 1, the CPU 10 may select either an even-numbered or odd-numbered cell as the adjustment cell so that the cell with the largest variation is included in the adjustment cell. Figure 6 is a graph showing the cell voltage, variation, discharge target amount, and discharge instruction for each of the multiple cells C. Note that the cell voltage and variation of the multiple cells C shown in Figure 6 are the same as the cell voltage and variation of the multiple cells C shown in Figure 2. In the example in Figure 6, since cell C1, which has the largest variation, is an odd-numbered cell, the discharge target amount calculation unit 12 of the CPU 10 selects an odd-numbered cell C as the adjustment cell. However, since the variation of cell C3 is zero, the discharge target amount calculation unit 12 does not select cell C3 as the adjustment cell. Then, while the CPU 10 is stopped, the ASIS 20 turns on switches S1, 5, and 7 to discharge the adjustment cells (cells C1, 5, and 7) so that the discharge amount of the adjustment cells reaches the discharge target amount.

[0042] In the modified example 1, the CPU 10 may select either an even-numbered or odd-numbered cell as the adjustment cell, so as not to select the cell with the smallest variation. In the example in Figure 5, since cell C3, which has the smallest variation, is an odd-numbered cell, the CPU 10's discharge target amount calculation unit 12 selects an even-numbered cell C as the adjustment cell. Then, while the CPU 10 is stopped, the ASIS 20 turns on switches S2, 4, 6, and 8 to discharge the adjustment cells (cells C2, 4, 6, and 8) so that the discharge amount of the adjustment cells reaches the discharge target amount. In other words, the CPU 10 does not select the cell with the smallest variation as the adjustment cell. This allows the discharge amount of the battery pack 40 to be prioritized and the discharge amount to be maximized.

[0043] In a second variation of this embodiment, if the largest maximum variation among the plurality of cells C is equal to or greater than a predetermined value, the CPU 10 may select the cell C with the largest variation as the adjustment cell. If the maximum variation is less than the predetermined value, the CPU 10 may select adjustment cells so that the number of cells to be adjustment cells is maximized. If the maximum variation is equal to or greater than the predetermined value, the voltage difference between the highest and lowest voltages among cells C1 to C8 is large, so priority is given to narrowing that voltage difference through capacitance adjustment. On the other hand, if the maximum variation is less than the predetermined value, the voltage difference among cells C1 to C8 is small, so priority is given to reducing the respective voltage differences and averaging the voltages of cells C1 to C8 rather than reducing the maximum voltage difference. If the maximum variation is equal to or greater than the predetermined value, the CPU 10 may include the cell with the largest variation as an adjustment cell and select adjustment cells so that the number of adjacent cells is equal to or less than a predetermined number. Alternatively, the CPU 10 may include the cell with the largest variation among the adjustment cells, and then select either an even-numbered cell or an odd-numbered cell as the adjustment cell, as in Modification Example 1. When the maximum variation is less than a predetermined value, the CPU 10 may select adjustment cells such that the number of cells to be adjustment cells is maximized, while satisfying the condition that the number of adjacent cells is equal to or less than a predetermined number. Alternatively, the CPU 10 may select adjustment cells such that the number of cells to be adjustment cells is maximized, while satisfying the condition that either an even-numbered cell or an odd-numbered cell is selected. In this way, when the variation among cells C is small, overall balance is prioritized for discharging, and when a specific cell begins to vary, capacity adjustment of the specific cell is prioritized for discharging, thereby maximizing the overall performance of the adjustment capability.

[0044] REFERENCE SIGNS LIST 10 Discharge circuit 11 Amount detection unit 12 Discharge target amount calculation unit 21 Discharge instruction output unit 30 Discharge circuit 40 Assembled battery 100 Capacity adjustment system C1 to C8 Cells S1 to S8 Switches

Claims

1. A capacity adjustment device that adjusts the capacity of a plurality of cells included in a battery pack, comprising: a processing unit that detects a variation in the capacities of the plurality of cells, selects an adjustment cell from the plurality of cells to be subject to capacity adjustment based on the detected variation, and calculates a target discharge amount for the adjustment cell; and an integrated circuit that outputs a discharge instruction to discharge the adjustment cell, thereby discharging the adjustment cell, wherein the processing unit executes a process of selecting the adjustment cell and a process of calculating the target discharge amount before processing by the processing unit is stopped, and the integrated circuit executes discharging the adjustment cell while processing by the processing unit is stopped so that the amount of discharge of the adjustment cell reaches the target discharge amount.

2. A capacity adjustment device according to claim 1, wherein the processing unit selects the adjustment cell to be subjected to capacity adjustment so that the number of adjacent cells is equal to or less than a predetermined number.

3. A capacity adjustment device according to claim 1, wherein the processing unit selects, as the adjustment cell, a cell that is even-numbered or odd-numbered in the arrangement order of the plurality of cells.

4. A capacity adjustment device according to claim 2 or 3, wherein said processing unit selects the cell having the largest amount of variation as said adjustment cell.

5. A capacity adjustment device according to claim 2 or 3, wherein said processing unit does not select the cell with the smallest amount of variation as said adjustment cell.

6. A capacity adjustment device according to claim 2 or 3, wherein the processing unit selects the cell with the largest amount of variation as the adjustment cell when the largest amount of variation among the amounts of variation for each of the plurality of cells is equal to or greater than a predetermined value, and when the maximum amount of variation is less than the predetermined value, selects the adjustment cells so as to maximize the number of cells that become the adjustment cells.

7. A capacity adjustment device according to any one of claims 1 to 6, wherein the plurality of cells are connected to a discharge circuit including a resistor, and the integrated circuit has a plurality of switches that switch on and off a current flowing through the discharge circuit and are connected to the plurality of cells, and switches on and off the switches connected to the adjustment cells, and maintains the switches connected to the cells not selected as the adjustment cells in an off state while the adjustment cells are being discharged.

8. A capacity adjustment method for adjusting the capacity of a plurality of cells included in a battery pack, wherein the steps executed by a processing unit include: a step of detecting an amount of variation in capacity of the plurality of cells; a selection step of selecting an adjustment cell to be subject to capacity adjustment from the plurality of cells based on the detected amount of variation; and a calculation step of calculating a target discharge amount of the adjustment cell, and the steps executed by an integrated circuit include: a discharge step of outputting a discharge instruction to discharge the adjustment cell, and discharging the adjustment cell so that the amount of discharge performed of the adjustment cell reaches the target discharge amount, wherein the selection step and the calculation step are executed before processing by the processing unit is stopped, and the discharge step is executed while processing by the processing unit is stopped.

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