Battery module

Abstract

A battery module according to an embodiment comprises a cell balance circuit, a voltage comparison circuit, and an output control circuit. The voltage comparison circuit includes: a plurality of first input wiring lines and a plurality of second input wiring lines to which a plurality of battery cell voltages are supplied; and a plurality of first output wiring lines and a plurality of second output wiring lines, said plurality of first output wiring lines outputting a value obtained by subtracting, from a battery cell voltage supplied to the first input wiring lines, another battery cell voltage supplied to the second input wiring lines and outputting a plurality of differences obtained by subtracting, from a common battery cell voltage, a plurality of respective another battery cell voltages, said plurality of second output wiring lines outputting a plurality of differences obtained by subtracting, from the plurality of respective battery cell voltages, a common another battery cell voltage. The output control circuit stops discharging by the cell balance circuit when the maximum voltage battery cell or the minimum voltage battery cell specified on the basis of the plurality of differences supplied from the plurality of respective first output wiring lines and the maximum voltage battery cell or the minimum voltage battery cell specified on the basis of the plurality of differences supplied from the plurality of respective second output wiring lines are different from each other.

Description

Technical Field

[0001] Embodiments of the present invention relate to a battery module.

Background Art

[0002] In a battery module including a battery pack having a plurality of battery cells connected in series, it is known that an imbalance in the voltages of the plurality of battery cells occurs due to variations such as the capacity and leakage current of individual battery cells. When charging the battery pack in a state where an imbalance in the voltages of the plurality of battery cells has occurred, charging ends when the battery cell with a high voltage is fully charged, even if the battery cell with a low voltage is not fully charged. Also, when discharging the battery pack in a state where an imbalance in the voltages of the plurality of battery cells has occurred, discharging ends when the battery cell with a low voltage is over-discharged, even if the battery cell with a high voltage is still capable of discharging.

[0003] Therefore, in a state where an imbalance in the voltages of the plurality of battery cells has occurred, the capacity of the battery pack cannot be efficiently utilized. Thus, a battery module including a battery pack is provided with a cell balance circuit that balances the voltages of the plurality of battery cells.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Control of the cell balance circuit (cell balance control) can be realized by either software or hardware. When performing cell balance control by software, it is necessary to install a microcontroller (MCU: Micro Controller Unit) in the battery module, and costs are required for installing the MCU and the program.

[0006] When performing cell balance control only by hardware, if a cell with the maximum voltage is selected by one circuit and a cell with the minimum voltage is selected by another circuit, when an incorrect result is output by either circuit, there is a possibility that the incorrect cell may be discharged or the energy for discharging may not be sufficient, deteriorating the voltage balance state of multiple battery cells.

[0007] Embodiments of the present invention have been made in view of the above circumstances, and an object thereof is to provide a battery module that ensures the reliability of cell balance control.

Means for Solving the Problem

[0008] A battery module according to an embodiment of the present invention includes a plurality of battery cells, a detection circuit that detects voltage values of the plurality of battery cells, a cell balance circuit that can individually discharge the plurality of battery cells, a plurality of first input wirings and a plurality of second input wirings to which voltage values of the plurality of battery cells are supplied, and a plurality of comparators that output a difference obtained by comparing voltage values of different battery cells, the plurality of comparators outputting a difference obtained by subtracting a second voltage value supplied from the second input wiring from a first voltage value supplied from the first input wiring; a plurality of first output wirings to which outputs of the plurality of comparators into which voltage values are input from the common first input wiring are supplied; and a plurality of second output wirings to which outputs of the plurality of comparators into which voltage values are input from the common second input wiring are supplied, a voltage comparison circuit including: a battery cell in which a voltage specified based on a plurality of differences supplied from each of the plurality of first output wirings is maximum; and an output control circuit that stops discharging by the cell balance circuit when a battery cell in which a voltage specified based on a plurality of differences supplied from each of the plurality of second output wirings is maximum is different, or when a battery cell in which a voltage specified based on a plurality of differences supplied from each of the plurality of first output wirings is minimum is different from a battery cell in which a voltage specified based on a plurality of differences supplied from each of the plurality of second output wirings is minimum.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0010] Hereinafter, a battery module according to an embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration example of a battery module according to an embodiment. The battery module MDL of the present embodiment includes a battery pack BT and a battery monitoring circuit (CMU: Cell monitoring unit) 100.

[0011] The battery pack BT includes a plurality of battery cells C1 to C n connected in series. The battery cells C1 to C n are, for example, lithium-ion batteries. The battery cells C1 to C n are not limited to lithium-ion batteries, and may be other storage batteries such as nickel-metal hydride batteries and lead batteries.

[0012] The battery monitoring circuit 100 includes a cell balance circuit 10 and a balancer control circuit 20. The cell balance circuit 10 can individually discharge a plurality of battery cells C1 to C n The cell balance circuit 10 includes a plurality of discharge switches S1 to S n Each of the plurality of discharge switches S1 to S n corresponds to a corresponding battery cell C1 to C nIt is provided in a path that electrically connects the positive terminal and the negative terminal through a resistor. For example, when the discharge switch S1 is turned on, the positive terminal and the negative terminal of the battery cell C1 are electrically connected through a resistor, and the energy stored in the battery cell C1 is discharged. The discharge switches S1 to S n The operation is controlled by a control signal from the balancer control circuit 20.

[0013] The balancer control circuit 20 is a circuit that controls the operation of the cell balance circuit 10. The balancer control circuit 20 includes a plurality of output circuits 211 to 21 n and a cell voltage detection unit 22, a voltage comparison unit 23, a difference extraction unit 24, an output control unit 25, and a timer circuit 26. The timer circuit 26 includes timer circuits 261, 262, and 263, which will be described later.

[0014] The plurality of output circuits 211 to 21 n are circuits that output control signals to the plurality of discharge switches S1 to S n The balancer control circuit 20 outputs control signals to each of the plurality of discharge switches S1 to S n and includes a plurality of output circuits 211 to 21 that output control signals to each of them. n

[0015] The cell voltage detection unit 22 is a detection circuit that detects the voltage value (or voltage equivalent value) of each of the plurality of battery cells C1 to C n The cell voltage detection unit 22 includes a differential amplifier (not shown) that converts the voltage of each of the plurality of battery cells C1 to C connected in series into a value based on the ground potential (GND). The differential amplifier includes, for example, a plurality of (n) operational amplifiers. The operational amplifiers receive the value of the positive terminal voltage and the negative value of the negative terminal voltage of the corresponding battery cells C1 to C n The operational amplifier outputs a value (cell voltage equivalent values Cell(1) to Cell(n)) obtained by amplifying the difference between the positive terminal voltage and the negative terminal voltage of the corresponding battery cells C1 to C n n

[0016] ​​​The voltage comparison unit 23 compares a plurality of cell voltage equivalent values Cell(1) to Cell(n) supplied from the cell voltage detection unit 22, and selects the battery cell with the maximum voltage and the battery cell with the minimum voltage among the plurality of battery cells C1 to C n . The voltage comparison unit 23 includes a voltage comparison circuit 231, registers 232C and 232R, selection circuits 233C and 233R, and a diagnosis circuit 234.

[0017] The voltage comparison circuit 231 is a circuit that compares the cell voltage equivalent values Cell(1) to Cell(n) of the plurality of battery cells C1 to C n . The voltage comparison circuit 231 outputs the results of comparing each of the cell voltage equivalent values Cell(1) to Cell(n) with all other cell voltage equivalent values Cell(1) to Cell(n). That is, the voltage comparison circuit 231 outputs the results of comparing the cell voltage equivalent value Cell(1) with all other cell voltage equivalent values Cell(2) to Cell(n), and outputs the results of comparing the cell voltage equivalent value Cell(2) with all other cell voltage equivalent values Cell(1), Cell(3) to Cell(n),..., and can output the results of comparing the cell voltage equivalent value Cell(n) with all other cell voltage equivalent values Cell(1) to Cell(n - 1).

[0018] FIG. 2 is a diagram schematically showing a configuration example of the voltage comparison circuit shown in FIG. 1. Note that the arrangement positions of the elements included in the circuit of FIG. 2 are merely examples, and any circuit that does not change the electrical connection state of the circuit can be applied to the battery module MDL of the present embodiment. In this example, the voltage comparison circuit 231 compares the cell voltage equivalent values Cell(A) to Cell(E) of a plurality (n = 5) of battery cells C A to C E . The voltage comparison circuit 231 includes a plurality of first input wirings Wi1, a plurality of second input wirings Wi2, a plurality of first output wirings Wo1, a plurality of second output wirings Wo2, and a plurality of voltage comparators COM.

[0019] The plurality of first input wirings Wi1 are wirings that supply the cell voltage equivalent values Cell(A) to Cell(E) of the plurality of battery cells C A ~C E to the input terminals of the voltage comparator COM. Each first input wiring Wi1 extends parallel to the first direction D1, and the plurality of first input wirings Wi1 are arranged side by side along the second direction D2 that intersects the first direction D1 with an interval therebetween.

[0020] The plurality of second input wirings Wi2 are wirings that supply the cell voltage equivalent values Cell(A) to Cell(E) of the plurality of battery cells C A ~C E to the negative input terminals of the voltage comparator COM. Each second input wiring Wi2 extends parallel to the second direction D2, and the plurality of second input wirings Wi2 are arranged side by side along the first direction D1 with an interval therebetween.

[0021] The plurality of voltage comparators COM output the difference obtained by comparing the cell voltage equivalent values Cell(A) to Cell(E) of different battery cells C A ~C E . Each of the plurality of voltage comparators COM includes an input terminal, a negative input terminal, and an output terminal. The cell voltage equivalent values Cell(A) to Cell(E) (first voltage values) are input from the first input wiring Wi1 to the input terminal of the voltage comparator COM. The cell voltage equivalent values Cell(A) to Cell(E) (second voltage values) are input from the second input wiring Wi2 to the negative input terminal of the voltage comparator COM. The voltage comparator COM outputs from the output terminal the difference obtained by subtracting the cell voltage equivalent values Cell(A) to Cell(E) input to the negative input terminal from the second input wiring Wi2 from the cell voltage equivalent values Cell(A) to Cell(E) supplied to the input terminal from the first input wiring Wi1.

[0022] The plurality of voltage comparators COM are arranged in the vicinity of the position where the first input wiring Wi1 and the second input wiring Wi2 that supply different cell voltage equivalent values Cell(A) to Cell(E) intersect.

[0023] A plurality of voltage comparators COM to which cell voltage equivalent values Cell(A) to Cell(E) common to the input terminals are input are arranged side by side along a first input wiring Wi1 that supplies the common cell voltage equivalent values Cell(A) to Cell(E). A plurality of voltage comparators COM to which cell voltage equivalent values Cell(A) to Cell(E) common to the negative input terminals are input are arranged side by side along a second input wiring Wi2 that supplies the common cell voltage equivalent values Cell(A) to Cell(E).

[0024] For example, a plurality of voltage comparators COM to which a cell voltage equivalent value Cell(A) common to the input terminals is input are arranged side by side along a first input wiring Wi1 that supplies the cell voltage equivalent value Cell(A), and are respectively arranged in the vicinity of positions where a plurality of second input wirings Wi2 that supply cell voltage equivalent values Cell(B) to Cell(E) and the first input wiring Wi1 that supplies the cell voltage equivalent value Cell(A) intersect.

[0025] For example, a plurality of voltage comparators COM to which a cell voltage equivalent value Cell(B) common to the negative input terminals is input are arranged side by side along a second input wiring Wi2 that supplies the cell voltage equivalent value Cell(B), and are respectively arranged in the vicinity of positions where a plurality of first input wirings Wi1 that supply cell voltage equivalent values Cell(A), Cell(C) to Cell(E) and the second input wiring Wi2 that supplies the cell voltage equivalent value Cell(B) intersect.

[0026] Each of the plurality of first output wirings Wo1 supplies the output values of a plurality of voltage comparators COM arranged side by side along each of the plurality of first input wirings Wi1 to the register 232C. For example, the output values (differences in cell voltage equivalent values B - A, B - C, B - D, B - E) of a plurality of voltage comparators COM arranged side by side along the first input wiring Wi1 that supplies the cell voltage equivalent value Cell(B) are supplied to the register 232C by a common first output wiring Wo1. The first output wiring Wo1 may include a plurality of wirings that supply each of the differences in cell voltage equivalent values B - A, B - C, B - D, B - E to the register 232C.

[0027] That is, one of the plurality of first output wirings Wo1 outputs a value obtained by subtracting other cell voltage equivalent values Cell(A), Cell(C) to Cell(E) that do not overlap with the cell voltage equivalent value Cell(B) supplied to the first input wiring Wi1 from the cell voltage equivalent value Cell(B) supplied to the second input wiring Wi2, and outputs a plurality of differences obtained by subtracting each of the other plurality of cell voltage equivalent values from the common cell voltage equivalent value.

[0028] Each of the plurality of second output wirings Wo2 supplies the output values of the plurality of voltage comparators COM arranged along each of the plurality of second input wirings Wi2 to the register 232R. For example, the output values (differences A-C, B-C, D-C, E-C of the cell voltage equivalent values) of the plurality of voltage comparators COM arranged along the second input wiring Wi2 that supplies the cell voltage equivalent value Cell(C) are supplied to the register 232R by the common second output wiring Wo2. The second output wiring Wo2 may include a plurality of wirings that supply each of the differences A-C, B-C, D-C, E-C of the cell voltage equivalent values to the register 232R.

[0029] That is, one of the plurality of second output wirings Wo2 outputs a value obtained by subtracting the cell voltage equivalent value Cell(C) that does not overlap with the cell voltage equivalent values Cell(A), Cell(B), Cell(D), Cell(E) supplied to the second input wiring Wi2 from the cell voltage equivalent values Cell(A), Cell(B), Cell(D), Cell(E) supplied to the first input wiring Wi1, and outputs a plurality of differences obtained by subtracting a common other cell voltage equivalent value from each of the plurality of cell voltage equivalent values.

[0030] The register 232C temporarily holds the values supplied from the plurality of first output wirings Wo1. The values held in the register 232C are supplied to the selection circuit 233C. The values held in the register 232C are updated at the timing when the signal φ1 is supplied from the timer circuit 262.

[0031] Register 232R temporarily holds the values supplied from the plurality of second output wirings Wo2. The value held in register 232R is supplied to selection circuit 233R. The value held in register 232R is updated at the timing when signal φ1 is supplied from timer circuit 261. Note that timer circuit 261 and timer circuit 262 are circuits that output signal φ1 at a common timing, and they may be integrally configured.

[0032] FIG. 3 is a diagram schematically showing a configuration example of the selection circuit shown in FIG. 1. Selection circuit (first selection circuit) 233C is a circuit that identifies the battery cell with the maximum voltage and the battery cell with the minimum voltage among the battery cells C A ~C E based on the plurality of differences supplied from each of the plurality of first output wirings Wo1. Selection circuit 233C includes a plurality of maximum value selection circuits CA1 to CE1 and a plurality of minimum value selection circuits CA2 to CE2.

[0033] Values (A - B, A - C, A - D, A - E) from a common first output wiring Wo1 are supplied to maximum value selection circuit CA1 and minimum value selection circuit CA2 via register 232C. Values (B - A, B - C, B - D, B - E) from a common first output wiring Wo1 are supplied to maximum value selection circuit CB1 and minimum value selection circuit CB2 via register 232C. Values (C - A, C - B, C - D, C - E) from a common first output wiring Wo1 are supplied to maximum value selection circuit CC1 and minimum value selection circuit CC2 via register 232C. Values (D - A, D - B, D - C, D - E) from a common first output wiring Wo1 are supplied to maximum value selection circuit CD1 and minimum value selection circuit CD2 via register 232C. Values (E - A, E - B, E - C, E - D) from a common first output wiring Wo1 are supplied to maximum value selection circuit CE1 and minimum value selection circuit CE2 via register 232C.

[0034] The maximum value selection circuit and the minimum value selection circuit to which values from the common first output wiring Wo1 are supplied via the register 232C correspond to a common battery cell. For example, the first output wiring Wo1 that supplies the values obtained by subtracting other cell voltage equivalent values Cell(A), Cell(B), Cell(D), and Cell(E) from the voltage equivalent value Cell(C) (C - A, C - B, C - D, C - E) is common to the maximum value selection circuit CC1 and the minimum value selection circuit CC2, and the maximum value selection circuit CC1 and the minimum value selection circuit CC2 correspond to the common battery cell C C corresponds.

[0035] Each of the plurality of maximum value selection circuits CA1 to CE1 is provided corresponding to each of the plurality of battery cells C A ~C E and outputs a high (H) level value when the cell voltage equivalent values Cell(A) to Cell(E) of the corresponding battery cell C A ~C E are the maximum values.

[0036] Each of the plurality of maximum value selection circuits CA1 to CE1 includes a logical product circuit with (n - 1) inputs. To each of the plurality of maximum value selection circuits CA1 to CE1, the value supplied from the corresponding first output wiring Wo1 to the register 232C and held in the register 232C is input. Each of the maximum value selection circuits CA1 to CE1 has an output value of 1 (H level) when all of the input values are positive (H level).

[0037] For example, when the cell voltage equivalent value Cell(A) is greater than the other cell voltage equivalent values Cell(B) to Cell(E) (is the maximum value), the differences A - B, A - C, A - D, A - E of the cell voltage equivalent values input to the maximum value selection circuit CA1 are all positive (H level), and the output value of the maximum value selection circuit CA1 becomes 1 (H level). For example, when the cell voltage equivalent value Cell(A) is not the maximum value, at least one of the differences A - B, A - C, A - D, A - E of the cell voltage equivalent values input to the maximum value selection circuit CA1 is negative (L level), and the output value of the maximum value selection circuit CA1 becomes 0 (L level).

[0038] Each of the plurality of minimum value selection circuits CA2 to CE2 corresponds to each of the plurality of battery cells C A ~C E and is provided. When the cell voltage equivalent values Cell(A) to Cell(E) of the corresponding battery cells C A ~C E are the minimum values, it outputs a high (H) level value.

[0039] Each of the plurality of minimum value selection circuits CA2 to CE2 includes (n - 1) NOT circuits and an (n - 1)-input AND circuit to which the output values of the NOT circuits are input. To each of the minimum value selection circuits CA2 to CE2, a value is supplied from the corresponding first output wiring Wo1 to the register 232C and the value held in the register 232C is input. Each of the minimum value selection circuits CA2 to CE2 outputs a value of 1 (H level) when all the input values are negative (L level).

[0040] For example, when the cell voltage equivalent value Cell(B) is smaller (the minimum value) than the other cell voltage equivalent values Cell(A), Cell(C) to Cell(E), the differences B - A, B - C, B - D, B - E of the cell voltage equivalent values input to the minimum value selection circuit CB2 are all negative (L level), and the output value of the minimum value selection circuit CB2 becomes 1 (H level). For example, when the cell voltage equivalent value Cell(B) is not the minimum value, at least one of the differences B - A, B - C, B - D, B - E of the cell voltage equivalent values input to the minimum value selection circuit CB2 is positive (H level), and the output value of the minimum value selection circuit CB2 becomes 0 (L level).

[0041] The values of the output signals MAX(C)A to MAX(C)E of the plurality of maximum value selection circuits CA1 to CE1 and the values of the output signals MIN(C)A to MIN(C)E of the plurality of minimum value selection circuits CA2 to CE2 are supplied to the diagnostic circuit 234 and the difference extraction unit 24.

[0042] FIG. 4 is a diagram schematically showing a configuration example of the selection circuit shown in FIG. 1. The selection circuit (second selection circuit) 233R is based on the plurality of differences supplied from each of the plurality of second output wirings Wo2, and the battery cells C A ~CE It is a circuit that identifies the battery cell with the maximum voltage and the battery cell with the minimum voltage. The selection circuit 233R includes a plurality of maximum value selection circuits RA1 to RE1 and a plurality of minimum value selection circuits RA2 to RE2.

[0043] Values (B - A, C - A, D - A, E - A) from the common second output wiring Wo2 are supplied to the maximum value selection circuit RA1 and the minimum value selection circuit RA2 via the register 232R. Values (A - B, C - B, D - B, E - B) from the common second output wiring Wo2 are supplied to the maximum value selection circuit RB1 and the minimum value selection circuit RB2 via the register 232R. Values (A - C, B - C, D - C, E - C) from the common second output wiring Wo2 are supplied to the maximum value selection circuit RC1 and the minimum value selection circuit RC2 via the register 232R. Values (A - D, B - D, C - D, E - D) from the common first output wiring Wo2 are supplied to the maximum value selection circuit RD1 and the minimum value selection circuit RD2 via the register 232R. Values (A - E, B - E, C - E, D - E) from the common second output wiring Wo2 are supplied to the maximum value selection circuit RE1 and the minimum value selection circuit RE2 via the register 232R.

[0044] The maximum value selection circuit and the minimum value selection circuit to which values from the common second output wiring Wo2 are supplied via the register 232R correspond to the common battery cell. For example, the second output wiring Wo2 that supplies values (A - C, B - C, D - C, E - C) obtained by subtracting the other cell voltage equivalent value Cell(C) common to these from the voltage equivalent values Cell(A), CELL(B), CELL(D), CELL(E) is common to the maximum value selection circuit RC1 and the minimum value selection circuit RC2, and the maximum value selection circuit RC1 and the minimum value selection circuit RC2 correspond to the common battery cell C C corresponds.

[0045] Each of the plurality of maximum value selection circuits RA1 to RE1 is provided corresponding to each of the plurality of battery cells C A ~C E and is provided corresponding to the corresponding battery cell C A ~C EWhen the cell voltage equivalent values of Cell(A) to Cell(E) are at their maximum values, it outputs a high (H) level value.

[0046] Each of the plurality of maximum value selection circuits RA1 to RE1 includes a NOT circuit of (n - 1) and a logical product circuit of (n - 1) inputs to which the output value of the NOT circuit is input. To each of the plurality of maximum value selection circuits RA1 to RE1, a value supplied from the corresponding second output wiring Wo2 to the register 232R and held in the register 232R is input. Each of the maximum value selection circuits RA1 to RE1 has an output value of 1 (H level) when all of the input values are negative (L level).

[0047] For example, when the cell voltage equivalent value Cell(A) is greater than the other cell voltage equivalent values Cell(B) to Cell(E) (is the maximum value), the differences B - A, C - A, D - A, E - A of the cell voltage equivalent values input to the maximum value selection circuit RA1 are all negative (L level), and the output value of the maximum value selection circuit RA1 becomes 1 (H level). For example, when the cell voltage equivalent value Cell(A) is not the maximum value, at least one of the differences B - A, C - A, D - A, E - A of the cell voltage equivalent values input to the maximum value selection circuit RA1 is positive (H level), and the output value of the maximum value selection circuit CA1 becomes 0 (L level).

[0048] Each of the plurality of minimum value selection circuits RA2 to RE2 A ~C E is provided corresponding to each of the plurality of battery cells C A ~C E and outputs a high (H) level value when the cell voltage equivalent values of Cell(A) to Cell(E) corresponding to the corresponding battery cell C

[0049] Each of the plurality of minimum value selection circuits RA2 to RE2 includes a logical product circuit of (n - 1) inputs. To each of the minimum value selection circuits RA2 to RE2, a value supplied from the corresponding second output wiring Wo2 to the register 232R and held in the register 232R is input. Each of the minimum value selection circuits RA2 to RE2 has an output value of 1 (H level) when all of the input values are positive (H level).

[0050] For example, when the cell voltage equivalent value Cell(B) is smaller (the minimum value) than other cell voltage equivalent values Cell(A), Cell(C) to Cell(E), the differences A - B, C - B, D - B, E - B of the cell voltage equivalent values input to the minimum value selection circuit RB2 are all positive (H level), and the output value of the minimum value selection circuit RB2 becomes 1 (H level). For example, when the cell voltage equivalent value Cell(B) is not the minimum value, at least one of the differences A - B, C - B, D - B, E - B of the cell voltage equivalent values input to the minimum value selection circuit RB2 is negative (L level), and the output value of the minimum value selection circuit CB2 becomes 0 (L level).

[0051] The values of the output signals MAX(R)A to MAX(R)E of the plurality of maximum value selection circuits RA1 to RE1 and the values of the output signals MIN(R)A to MIN(R)E of the plurality of minimum value selection circuits RA2 to RE2 are supplied to the diagnosis circuit 234 and the difference extraction unit 24.

[0052] FIG. 5 is a diagram schematically showing a configuration example of the diagnosis circuit shown in FIG. 1. The diagnosis circuit 234 includes a selection circuit output diagnosis unit C1 and a voltage comparison circuit output diagnosis unit C2. The selection circuit output diagnosis unit C1 includes an exclusive NOR circuit EQ, and logic product circuits A1 and A2.

[0053] The exclusive NOR circuit EQ outputs high (H) level signals MAX(x)A to MAX(x)E when each of the output signals MAX(C)A to MAX(C)E of the selection circuit 233C and the output signals MAX(R)A to MAX(R)E of the selection circuit 233R has the same value. When there are different values in the corresponding ones among the output signals MAX(C)A to MAX(C)E of the selection circuit 233C and the output signals MAX(R)A to MAX(R)E of the selection circuit 233R (for example, when the values of the signal MAX(C)E and the signal MAX(R)E are different), the values of the corresponding output signals MAX(x)A to MAX(x)E of the exclusive NOR circuit EQ become low (L) level. The output signals MAX(x)A to MAX(x)E of the exclusive NOR logic sum circuit EQ are input to the AND circuit A1.

[0054] The exclusive NOR logic sum circuit EQ outputs high (H)-level signals MIN(x)A to MIN(x)E when each of the output values MIN(R)A to MIN(R)E of the selection circuit 233C and the output values MIN(R)A to MIN(R)E of the selection circuit 233R are the same value. When there are different values in the corresponding ones among the output values MIN(C)A to MIN(C)E of the selection circuit 233C and the output values MIN(R)A to MIN(R)E of the selection circuit 233R, the values of the corresponding output signals MIN(x)A to MIN(x)E of the exclusive NOR logic sum circuit EQ become low (L) level. The output signals MIN(x)A to MIN(x)E of the exclusive NOR logic sum circuit EQ are input to the AND circuit A2.

[0055] The AND circuit A1 outputs the logical product value of the input signals MAX(x)A to MAX(x)E as the output signal MAX_Enable. The AND circuit A2 outputs the logical product value of the input signals MIN(x)A to MIN(x)E as the output signal MIN_Enable.

[0056] FIG. 6 is a diagram for explaining an example of the operation of the selection circuit output diagnosis unit of the diagnosis circuit shown in FIG. 5. Here, the output value (difference value corresponding to the cell voltage) of the voltage comparison circuit 231 is described in a matrix form such that the values supplied to the register 232C by each first output wiring Wo1 are arranged in the row direction and the values supplied to the register 232R by each second output wiring Wo2 are arranged in the column direction.

[0057] In the selection circuit 233C, the battery cells corresponding to the first output wirings Wo1 whose output values are all high (H) level are regarded as the battery cells with the maximum voltage, and the battery cells corresponding to the first output wirings Wo1 whose output values are all low (L) level are regarded as the battery cells with the minimum voltage, and the signals MAX(C)A to MAX(C)E and the signals MIN(C)A to MIN(C)E are output.

[0058] In the selection circuit 233R, the battery cell corresponding to the first output wiring Wo1 whose output values are all at the low (L) level is taken as the battery cell with the maximum voltage, and the battery cell corresponding to the first output wiring Wo1 whose output values are all at the high (H) level is taken as the battery cell with the minimum voltage, and signals MAX(R)A to MAX(R)E and signals MIN(R)A to MIN(R)E are output.

[0059] The selection circuit output diagnosis unit C1 compares the output value of the selection circuit 233C with the output value of the selection circuit 233R, and diagnoses the possibility of abnormalities in the voltage comparison circuit 231, the registers 232C and 232R, and the selection circuits 233C and 233R.

[0060] The output signal MAX_Enable of the AND circuit A1 becomes the low (L) level, for example, when the battery cell with the maximum voltage selected by the selection circuit 233C is different from the battery cell with the maximum voltage selected by the selection circuit 233R.

[0061] That is, when the output signal MAX_Enable is at the high (H) level, the selection circuits 233C and 233R and the circuits before them are operating normally, and the values output by the selection circuits 233C and 233R can be trusted. When the output signal MAX_Enable is at the low (L) level, there is a possibility that the voltage comparison circuit 231, the registers 232C and 232R, and the selection circuits 233C and 233R are not operating normally, and the reliability of the values output by the selection circuits 233C and 233R is low.

[0062] Also, the output signal MIN_Enable of the AND circuit A2 becomes the low (L) level, for example, when the battery cell with the minimum voltage selected by the selection circuit 233C is different from the battery cell with the minimum voltage selected by the selection circuit 233R.

[0063] That is, when the output signal MIN_Enable is at the high (H) level, the selection circuits 233C, 233R and the circuits before them are operating normally, and the values output by the selection circuits 233C, 233R can be trusted. When the output signal MIN_Enable is at the low (L) level, there is a possibility that the voltage comparison circuit 231, the registers 232C, 232R, and the selection circuits 233C, 233R are not operating normally, and the reliability of the values output by the selection circuits 233C, 233R is low. The output signals MAX_Enable and MIN_Enable of the selection circuit output diagnosis unit C1 are supplied to the output control circuit 252 of the output control unit 25.

[0064] The voltage comparison circuit output diagnosis unit C2 includes a plurality of exclusive OR circuits EX1, EX2 and a plurality of AND circuits A3, A4, A5. The values held in the register 232C are supplied to the plurality of exclusive OR circuits EX1. A difference value calculated from two cell voltage equivalent values is input to each exclusive OR circuit EX1. The voltage comparison circuit output diagnosis unit C2 includes an exclusive OR circuit EX1 for each combination of two cell voltage equivalent values. For example, FIG. 5 illustrates an exclusive OR circuit EX1 to which the values of the difference A - B and B - A calculated from the cell voltage equivalent value Cell(A) and the cell voltage equivalent value (B) are input.

[0065] FIG. 7 is a diagram for explaining an example of the operation of the voltage comparison circuit output diagnosis unit of the diagnosis circuit shown in FIG. 5. The exclusive OR circuit EX1 outputs a high (H) level output signal C_check when the two input values are at different levels, and outputs a low (L) level output signal C_check when the two input values are at the same level.

[0066] The output signals C_check of the plurality of exclusive OR circuits EX1 are input to the AND circuit A3. A plurality of exclusive OR circuits EX2 are supplied with the value held in register 232R. Each exclusive OR circuit EX2 receives a difference value calculated from two cell voltage equivalent values. The voltage comparison circuit output diagnosis unit C2 includes an exclusive OR circuit EX2 for each combination of two cell voltage equivalent values. For example, FIG. 5 illustrates an exclusive OR circuit EX2 to which the values of the differences A-B and B-A calculated from the cell voltage equivalent value Cell(A) and the cell voltage equivalent value (B) are input.

[0067] The exclusive OR circuit EX2 outputs a high (H) level output signal R_check when the two input values are at different levels, and outputs a low (L) level output signal R_check when the two input values are at the same level. The output signals R_check of the plurality of exclusive OR circuits EX2 are input to the AND circuit A4.

[0068] The AND circuit A3 supplies the logical product of the values of the signals C_check supplied from the plurality of exclusive OR circuits EX1 to the AND circuit A5. The AND circuit A4 supplies the logical product of the values of the signals R_check supplied from the plurality of exclusive OR circuits EX2 to the AND circuit A5. The AND circuit A5 outputs the logical product value of the output value of the AND circuit A3 and the output value of the AND circuit A4 as the value of the signal CR_check.

[0069] That is, when the signs of the two values input to each of the exclusive OR circuits EX1 are different (including the H level and the L level), or when the signs of the two values input to each of the exclusive OR circuits EX2 are different (including the H level and the L level), the value of the output signal CR_check of the AND circuit A5 becomes high (H) level.

[0070] Here, if the voltage comparison circuit 231, the registers 232C and 232R, and the wiring included in the comparison circuit 23 are operating normally, the binary codes input to the exclusive-OR circuits EX1 and EX2 will not match (except when the voltages of the two battery cells are equal). Therefore, when the value of the output signal CR_check of the AND circuit A5 is at the high (H) level, it means that the voltage comparison circuit 231 and the registers 232C and 232R are operating normally. In this case, the selection results of the battery cell with the maximum voltage and the battery cell with the minimum voltage based on the output value of the voltage comparison circuit 231 are reliable.

[0071] On the other hand, when the value of the output signal CR_check of the AND circuit A5 is at the low (L) level, it means that the binary values input to at least one of the multiple exclusive-OR circuits EX1 and EX2 are at the same level, and there is a possibility that the voltage comparison circuit 231 and the registers 232C and 232R are not operating normally. In this case, the reliability of the selection results of the battery cell with the maximum voltage and the battery cell with the minimum voltage based on the output value of the voltage comparison circuit 231 is low. The output signal CR_check of the voltage comparison circuit output diagnosis unit C2 is supplied to the output control circuit 252 of the output control unit 25.

[0072] FIG. 8 is a diagram schematically showing a configuration example of the differential extraction unit and the output control unit shown in FIG. 1. The differential extraction unit 24 includes multiplexers 241 and 242 and a differential amplifier 243.

[0073] The multiplexer 241 includes a plurality of switching elements. The voltage equivalent values of the corresponding battery cells are input to the input terminals of the plurality of switching elements. The output terminals of the plurality of switching elements are electrically connected to the input terminals of the differential amplifier 243. The signals MAX(C)A to MAX(C)E or the signals MAX(R)A to MAX(R)E corresponding to each are input to the control terminals of the plurality of switching elements. The switching element of the multiplexer 241 conducts between the input terminal and the output terminal when a high (H) level signal is input to the control terminal. Therefore, the multiplexer 241 supplies the voltage equivalent value of the battery cell with the maximum voltage to the input terminal of the differential amplifier 243.

[0074] The multiplexer 242 includes a plurality of switching elements. The voltage equivalent values of the corresponding battery cells are input to the input terminals of the plurality of switching elements. The output terminals of the plurality of switching elements are electrically connected to the negative input terminal of the differential amplifier 243. The signals MIN(C)A to MIN(C)E or the signals MIN(R)A to MIN(R)E corresponding to each are input to the control terminals of the plurality of switching elements. The switching element of the multiplexer 242 conducts between the input terminal and the output terminal when a high (H) level signal is input to the control terminal. Therefore, the multiplexer 242 supplies the voltage equivalent value of the battery cell with the minimum voltage to the negative input terminal of the differential amplifier 243.

[0075] The differential amplifier 243 outputs an amplified value of the difference obtained by subtracting the value input to the negative input terminal from the value input to the input terminal. That is, the differential amplifier 243 outputs an amplified value (voltage difference ΔV) of the difference obtained by subtracting the voltage equivalent value of the battery cell with the minimum voltage from the voltage equivalent value of the battery cell with the maximum voltage. The output of the differential amplifier 243 is input to the output control unit 25.

[0076] The output control unit 25 includes a comparator 251, an output control circuit 252, and an enable signal output unit 253 (shown in FIG. 1). Comparator 251 outputs a value dV_Enable obtained by subtracting a threshold value Vref from the voltage difference ΔV output from differential amplifier 243. When the voltage difference ΔV is equal to or greater than the threshold value Vref, the output signal dV_Enable becomes positive (high level), and at this time, cell balance control is executed. When the voltage difference ΔV is smaller than the threshold value Vref, the output signal dV_Enable becomes negative (low level), and at this time, cell balance control is stopped.

[0077] From the above, by appropriately setting the threshold value Vref, when the voltages of a plurality of battery cells are balanced, cell balance control is executed and the voltage balance is not disrupted. In this embodiment, the threshold value Vref is, for example, 10 mV. By providing a threshold value Vref for the battery cell voltage when executing cell balance control, the voltage difference of the battery cells in which cell balance circuit 10 operates can be made variable.

[0078] Enable signal output unit 253 generates and outputs an enable signal (or disable signal) other than the output signal dV_Enable of comparator 251 and the output signals MAX_Enable and MIN_Enable of selection circuit output diagnosis unit C1. The enable signal (or disable signal) output from enable signal output unit 253 is supplied to output control circuit 252.

[0079] Enable signal output unit 253 acquires, for example, at least one of the temperature of a plurality of battery cells (or battery pack BT), the current flowing through battery pack BT, the voltage of battery pack BT (or a plurality of battery cells), and the remaining capacity of battery pack BT (or a plurality of battery cells), and generates an enable signal (or disable signal). The temperature value of a plurality of battery cells or battery pack BT may be the temperature in the vicinity (surroundings) of any battery cell or battery pack BT, or an average value or median value of a plurality of temperature values acquired at a plurality of locations in the vicinity of a plurality of battery cells may be used.

[0080] The enable signal output unit 253 generates and outputs an enable signal (or a disable signal for stopping the cell balance control) for executing (starting) the cell balance control when, for example, the temperatures of a plurality of battery cells are higher than a predetermined temperature, lower than the predetermined temperature, or within a predetermined temperature range.

[0081] The enable signal output unit 253 generates and outputs an enable signal (or a disable signal for stopping the cell balance control) for executing (starting) the cell balance control when, for example, the current (charging current or discharging current) flowing through the battery pack BT is greater than a predetermined current, less than the predetermined current, or within a predetermined current range.

[0082] The enable signal output unit 253 generates and outputs an enable signal (or a disable signal for stopping the cell balance control) for executing (starting) the cell balance control when, for example, the voltage of the battery pack BT (or a plurality of battery cells) is greater than a predetermined voltage, less than the predetermined voltage, or within a predetermined voltage range.

[0083] The enable signal output unit 253 generates and outputs an enable signal (or a disable signal for stopping the cell balance control) for executing (starting) the cell balance control when, for example, the remaining capacity of the battery pack BT (or a plurality of battery cells) is more than a predetermined capacity, less than the predetermined capacity, or within a predetermined capacity range.

[0084] The output control circuit 252 acquires the output signal dV_Enable of the comparator 251, the output signals MAX_Enable and MIN_Enable of the selection circuit output diagnosis unit C1, the output signal of the enable signal output unit 253, the output signals MAX(R)A~E and MIN(R)A~E of the register 232R, the output signals MAX(C)A~E and MIN(C)A~E of the register 232C, the output signal φ2 of the timer circuit 263, and the output signal CR_check of the voltage comparison circuit output diagnosis unit C2, and outputs control signals CB_MAX (or output signals CB_MIN) corresponding to each of n output circuits 211~21.

[0085] Note that the timer circuit 263 outputs a high-level signal φ2 to the output control circuit 252 during the period when the cell balance circuit 10 operates, and outputs a low-level signal φ2 to the output control circuit 252 during the period when the cell balance circuit 10 is in a standby state. For example, the timer circuit 263 can stop the cell balance circuit 10 during the period when the voltages of a plurality of battery cells are being measured to ensure the accuracy of the measured voltages.

[0086] Also, the output control circuit 252 only needs to acquire at least one of the output signals MAX(R)A~E and MIN(R)A~E of the register 232R and the output signals MAX(C)A~E and MIN(C)A~E of the register 232C, and it is not necessary to acquire the output values of both the register 232R and the register 232C.

[0087] The signals acquired by the output control circuit 252 are values based on the ground potential. However, the output control circuit 252 outputs output signals CB_MAX (or output signals CB_MIN) based on the negative electrode potential of each of the plurality of battery cells to the output circuits 211~21 n for output.

[0088] The output control circuit 252 outputs a control signal CB_Max to the cell balance circuit 10 to discharge at least the battery cell with the maximum voltage when, for example, all the acquired enable signals are at a high level (positive) (or all the disable signals are negative), the output signal CR_check of the voltage comparison circuit output diagnosis unit C2 is at a high (H) level, and it is a period during which the cell balance circuit 10 set by the timer circuit 263 operates (the output signal φ2 is at a high level).

[0089] FIG. 9 is a diagram for explaining an example of the input signals and output signals of the output control circuit shown in FIG. 8. Here, the values of the enable signal (or disable signal) input from the enable signal output unit 253 to the output control circuit 252, the output signal CR_check of the voltage comparison circuit output diagnosis unit C2, the output signals MIN(R)A~E of the register 232R, and the output signals MIN(C)A~E of the register 232C are omitted. In this example, the output control circuit 252 outputs a control signal CB_Max for forcibly discharging the battery cell with the maximum voltage to the cell balance circuit 10.

[0090] When the output signal φ2 of the timer circuit 263 is at a low (L) level, the output control circuit 252 outputs an output signal CB_Max for turning off all the discharge switches S1~S n and does not discharge all the battery cells. Also, when the output signal φ2 of the timer circuit 263 is at a high (H) level, the output control circuit 252 outputs an output signal CB_Max for turning off all the discharge switches S1~S n when at least any one of the values of the enable signals dV_Enable, MAX_Enable, MIN_Enable and the output signal CR_check of the voltage comparison circuit output diagnosis unit C2 is at a low (L) level, and does not discharge all the battery cells.

[0091] When the output signal φ2 of the timer circuit 263 is at a high (H) level and all values of the enable signals dV_Enable, MAX_Enable, and MIN_Enable are at a high (H) level, the output control circuit 252 outputs a signal CB_Max for discharging the battery cell with the maximum voltage based on the values of the output signals MAX(R)A to E of the register 232R or the output signals MAX(C)A to E of the register 232C.

[0092] Note that the output control circuit 252 only needs to obtain at least one of the output signals MAX(R)A to E of the register 232R and the output signals MAX(C)A to E of the register 232C, and it is not necessary to obtain the output values of both the register 232R and the register 232C.

[0093] The output control circuit 252 may output a control signal CB_Min to the cell balance circuit 10 so as to discharge all battery cells other than the battery cell with the minimum voltage.

[0094] FIG. 10 is a diagram for explaining another example of the input signals and output signals of the output control circuit shown in FIG. 8. Here, the values of the enable signal (or disable signal) input from the enable signal output unit 253 to the output control circuit 252, the output signal CR_check of the voltage comparison circuit output diagnosis unit C2, the output signals MAX(R)A to E of the register 232R, and the output signals MAX(C)A to E of the register 232C are omitted. In this example, the output control circuit 252 outputs a control signal CB_Min for forcibly discharging all battery cells other than the battery cell with the minimum voltage to the cell balance circuit 10.

[0095] When the output signal φ2 of the timer circuit 263 is at a low (L) level, the output control circuit 252 turns off all discharge switches S1 to S regardless of the values of other input signals. nOutputs an output signal CB_Max to turn off and does not discharge all battery cells. Also, when the output signal φ2 of the timer circuit 263 is at the high (H) level, the output control circuit 252 outputs an output signal CB_Max to turn off and does not discharge all battery cells when at least any one of the values of the enable signals dV_Enable, MAX_Enable, MIN_Enable and the output signal CR_check of the voltage comparison circuit output diagnosis unit C2 is at the low (L) level, and discharges all battery cells except the battery cell with the minimum voltage based on the values of the output signals MIN(R)A~E of the register 232R or the output signals MIN(C)A~E of the register 232C when all the values of the enable signals dV_Enable, MAX_Enable, MIN_Enable are at the high (H) level. n Outputs an output signal CB_Max to turn off and does not discharge all battery cells.

[0096] When the output signal φ2 of the timer circuit 263 is at the high (H) level and all the values of the enable signals dV_Enable, MAX_Enable, MIN_Enable are at the high (H) level, the output control circuit 252 outputs a signal CB_Min to discharge all battery cells except the battery cell with the minimum voltage based on the values of the output signals MIN(R)A~E of the register 232R or the output signals MIN(C)A~E of the register 232C.

[0097] Note that the output control circuit 252 only needs to acquire at least any one of the output signals MIN(R)A~E of the register 232R and the output signals MIN(C)A~E of the register 232C, and it is not necessary to acquire the output values of both the register 232R and the register 232C.

[0098] According to the battery module MDL of the present embodiment, the cell balance circuit 10 can be controlled by the control signal CB_Max or the control signal CB_Min generated as described above, and highly reliable cell balance control can be realized.

[0099] For example, when performing cell balance control by software, it is necessary to mount an MCU on the battery module, and costs are required for mounting the MCU and the program. On the other hand, since the battery module MDL of the present embodiment performs cell balance control only by hardware, cell balance control can be realized at low cost, and a circuit that operates at high speed without sequential operations such as during program execution can be realized.

[0100] Also, if a battery cell with the maximum voltage is selected by one circuit and a battery cell with the minimum voltage is selected by another circuit, when an incorrect result is output by either circuit, there is a possibility that the incorrect cell may be discharged or the energy for discharging may be insufficient, deteriorating the balance state of the cell voltages.

[0101] On the other hand, in the battery module MDL of the present embodiment, for all combinations of the voltages (or voltage equivalent values) of a plurality of battery cells, the voltage comparison matrix obtained by comparing after changing the order of values is used to compare the magnitudes of the cell voltages (or voltage equivalent values), and the vertical axis (the value held in register 232R) and the horizontal axis (the value held in register 232C), which are the results of the voltage comparison matrix, are compared, enabling highly reliable cell balance control. Further, in the battery module MDL of the present embodiment, when the balancer control circuit 20 is operating normally, circuit diagnosis is performed based on items (for example, the difference A - B and B - A of the cell voltage equivalent values) that do not necessarily result in equality except in the case of zero, enabling highly reliable cell balance control. According to the present embodiment, by performing appropriate cell balance control as described above, it is possible to provide a battery module that ensures the charge and discharge capacity of the battery module MDL and guarantees the reliability of the cell balance control.

[0102] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and the equivalent scope thereof.

[0103] In the battery module MDL of the above-described embodiment, in the diagnostic circuit 234, diagnosis using the output values of the selection circuits 233C and 233R and diagnosis using the output values of the registers 232C and 232R are performed. However, the diagnostic circuit 234 does not necessarily perform both of these diagnoses. Even when the diagnostic circuit 234 performs only one of the diagnosis using the output values of the selection circuits 233C and 233R and the diagnosis using the output values of the registers 232C and 232R, the same effects as those of the above-described embodiment can be obtained.

Claims

1. A plurality of battery cells; A detection circuit for detecting voltage values of the plurality of battery cells; A cell balance circuit capable of discharging the plurality of battery cells individually; A plurality of first input wirings and a plurality of second input wirings to which voltage values of the plurality of battery cells are supplied, and a plurality of comparators for outputting a difference obtained by comparing voltage values of the battery cells different from each other, the plurality of comparators for outputting a difference obtained by subtracting a second voltage value supplied from the second input wiring from a first voltage value supplied from the first input wiring; a plurality of first output wirings to which outputs of the plurality of comparators into which a voltage value is input from the common first input wiring are supplied; and a plurality of second output wirings to which outputs of the plurality of comparators into which a voltage value is input from the common second input wiring are supplied, a voltage comparison circuit; An output control circuit for stopping discharging by the cell balance circuit when a battery cell having the maximum voltage specified based on a plurality of differences supplied from each of the plurality of first output wirings is different from a battery cell having the maximum voltage specified based on a plurality of differences supplied from each of the plurality of second output wirings, or when a battery cell having the minimum voltage specified based on a plurality of differences supplied from each of the plurality of first output wirings is different from a battery cell having the minimum voltage specified based on a plurality of differences supplied from each of the plurality of second output wirings, a battery module.

2. The plurality of battery cells include a first battery cell and a second battery cell, The output control circuit stops discharging by the cell balance circuit when signs of a difference obtained by subtracting the voltage value of the second battery cell from the voltage value of the first battery cell supplied from the first output wiring and a difference obtained by subtracting the voltage value of the first battery cell from the voltage value of the second battery cell supplied from the second output wiring are the same. The battery module according to claim 1.

3. The output control circuit stops discharging by the cell balance circuit when a voltage difference obtained by subtracting a minimum value from a maximum value of voltages of the plurality of battery cells is smaller than a predetermined threshold value. The battery module according to claim 1.

4. The output control circuit discharges the battery cell having the maximum voltage by the cell balance circuit based on a plurality of differences supplied from each of the plurality of first output wirings or a plurality of differences supplied from each of the plurality of second output wirings. The battery module according to claim 1.

5. The battery module according to claim 1, wherein the output control circuit causes the cell balance circuit to discharge battery cells other than the battery cell having the minimum voltage based on a plurality of differences supplied from each of the plurality of first output wirings or a plurality of differences supplied from each of the plurality of second output wirings.

6. The battery module according to any one of claims 1 to 5, wherein the output control circuit stops or starts discharging by the cell balance circuit when the voltage value of the battery pack including the plurality of battery cells is smaller than a predetermined threshold or larger than the predetermined threshold.

7. The battery module according to any one of claims 1 to 5, wherein the output control circuit stops or starts discharging by the cell balance circuit when the current flowing through the plurality of battery cells is smaller than a predetermined threshold or larger than the predetermined threshold.

8. The battery module according to any one of claims 1 to 5, wherein the output control circuit stops or starts discharging by the cell balance circuit when the temperature around the plurality of battery cells is smaller than a predetermined threshold or larger than the predetermined threshold.

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