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

Abstract

A battery pack equalization device (8) comprises a transfer circuit, a voltage measurement circuit, an ammeter (20), and a control unit (14). The control unit (14) executes: a measurement step (S106) in which, when the voltage of at least one battery reaches a discharge termination voltage, a battery, the voltage of which has not reached the discharge termination voltage, is discharged until the voltage thereof reaches the discharge termination voltage, and a discharged charge amount is measured; a transfer step (S109) for transferring charges between a plurality of batteries (b1-bn) on the basis of the charge amounts measured in the measurement step (S106); and an equalization step (S103) for starting equalization when the voltage difference (delta V) between the plurality of batteries (b1-bn) is greater than the equalization start voltage (Vth) after the transfer step (S109).

Description

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

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

[0002] 2. Description of the Related Art A technique is known in which charging and discharging (balancing current) between a plurality of batteries is used to make the SOC (State Of Charge) of each of a plurality of batteries connected in series the same.

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

[0004] Patent No. 6641665

[0005] However, in the adjustment device described in Patent Document 1, if the balancing current is limited by the circuit configuration or if there is a large variation in the deterioration of multiple batteries, the difference between the current supplied to the load and the balancing current may become large, and it may not be possible to make the SOC of multiple batteries the same.

[0006] Therefore, an object of the present disclosure is to provide a battery pack equalization device or the like that can equalize the SOC of multiple batteries even when the balancing current is limited by the circuit configuration or when there is a large variation in the deterioration of the multiple batteries.

[0007] In order to achieve the above-mentioned goal, an assembled battery equalization device according to one aspect of the present disclosure is an assembled battery equalization device that equalizes the remaining capacity of a plurality of batteries connected in series, and includes a transfer circuit that transfers charge between the plurality of batteries, a voltage measurement circuit that measures the voltage of each of the plurality of batteries, an ammeter that measures the amount of charge transferred in each of the plurality of batteries, and a control unit that controls the transfer circuit, and when the voltage of at least one of the batteries measured by the voltage measurement circuit reaches a discharge cut-off voltage that is a voltage that stops discharging of the plurality of batteries, the control unit The method includes a measurement step of discharging the batteries that have not yet reached the discharge end voltage until the voltage reaches the discharge end voltage, and measuring the amount of charge discharged by the batteries until the voltage reaches the discharge end voltage; a transfer step of supplying current from the charged batteries to a load, and then transferring charge between the plurality of batteries for a predetermined period of time by controlling the transfer circuit based on the amount of charge measured in the measurement step; and an equalization step of starting the equalization after the transfer step when the voltage difference between the plurality of batteries is greater than an equalization start voltage that is set at a predetermined voltage value.

[0008] In order to achieve the above object, a battery pack equalization method according to one aspect of the present disclosure is a battery pack equalization method using a battery pack equalization device that equalizes a plurality of batteries connected in series to make the remaining capacity of each battery the same, the battery pack equalization device including a transfer circuit that transfers charge between the plurality of batteries, a voltage measurement circuit that measures the voltage of each of the plurality of batteries, and an ammeter that measures the amount of charge transferred in each of the plurality of batteries, and the battery pack equalization method includes: a battery pack equalization device that, when the voltage of at least one of the batteries measured by the voltage measurement circuit reaches a discharge cut-off voltage that is a voltage at which discharging of the plurality of batteries is stopped, measures whether the discharge cut-off voltage has not been reached; The method includes a measurement step of discharging the batteries that have not yet reached the discharge end voltage until the voltage of the battery reaches the discharge end voltage, and measuring the amount of charge discharged from the batteries until the voltage reaches the discharge end voltage; a transfer step of supplying current from the charged batteries to a load, and then transferring charge between the plurality of batteries for a predetermined period of time by controlling the transfer circuit based on the amount of charge measured in the measurement step; and an equalization step of starting the equalization after the transfer step when the voltage difference between the plurality of batteries is larger than an equalization start voltage that is set at a predetermined voltage value.

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

[0010] The present disclosure provides a battery pack equalization device and the like that can equalize the SOC of multiple batteries even when the balancing current is limited by a circuit or when there is a large variation in the deterioration of the multiple batteries.

[0011] FIG. 1 is a block diagram showing the configuration of a system including a battery pack equalization device. FIG. 2 is a circuit diagram showing the detailed configuration of a cell balance circuit. FIG. 3 is a diagram showing the time variation of the voltage of each of a plurality of batteries. FIG. 4 is a flowchart showing the operation of the battery pack equalization device shown in FIG. 1. FIG. 5A is a diagram showing a specific example corresponding to steps S101 to S104 in FIG. 3. FIG. 5B is a diagram showing a specific example corresponding to steps S102 to S104 and steps S108 to S109 in FIG. 3.

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

[0013] 1 is a block diagram showing the configuration of a system including a battery pack equalization device 8. As shown in FIG. 1 , the present disclosure is configured with a battery pack 2, a load 4, an external power supply 6, and the battery pack equalization device 8.

[0014] The battery pack 2 is a battery in which a plurality of batteries b1 to bn (n is an integer of 2 or more) are connected in series. Note that the battery pack 2 may also be a battery in which a plurality of batteries b1 to bn are connected in parallel. The batteries used for the plurality of batteries b1 to bn are secondary batteries that can be charged and discharged, such as lead-acid batteries or lithium-ion batteries.

[0015] The load 4 is a device that operates using the power supplied by the battery pack 2, and is, for example, an actuator, a motor, or a control device.

[0016] The external power supply 6 is a power supply that supplies power to the battery pack 2. The external power supply 6 includes an AC (Alternating Current) / DC (Direct Current) converter that converts AC power into DC power.

[0017] The battery pack equalizer 8 is a device that equalizes the remaining capacity of each of the multiple batteries b1 to bn in the battery pack 2. The battery pack equalizer 8 performs equalization by charging and discharging the multiple batteries b1 to bn so as to eliminate differences in SOC or voltage among the multiple batteries b1 to bn. A detailed description of equalization will be given later.

[0018] The battery pack equalization device 8 includes a cell balance circuit 10 , a monitoring unit 12 , and a control unit 14 .

[0019] The cell balance circuit 10 is a circuit for transferring electric charges among a plurality of batteries b1 to bn. Fig. 2 is a circuit diagram showing a detailed configuration of the cell balance circuit 10. Note that the configuration of the cell balance circuit 10 shown in Fig. 2 is one example, and modifications of each component are within the scope of the present disclosure as long as the functions of the cell balance circuit 10 are fulfilled.

[0020] As shown in FIG. 2, the cell balance circuit 10 includes a plurality of voltmeters V1 to Vn (n is an integer equal to or greater than 2), a DC / DC converter 16, a capacitor 18, an ammeter 20, and changeover switches SWa to SWz.

[0021] The multiple voltmeters V1 to Vn measure the voltages of the multiple batteries b1 to bn connected in series. The multiple voltmeters V1 to Vn are connected to the positive and negative electrodes of the multiple batteries b1 to bn, respectively, and measure the voltages between the electrodes of the multiple batteries b1 to bn. In this specification, the multiple voltmeters V1 to Vn and the wiring connected to the positive and negative electrodes of the multiple batteries b1 to bn are referred to as a voltage measurement circuit. The number of voltmeters included in the cell balance circuit 10 increases or decreases depending on the number of connected batteries. Alternatively, a single voltmeter may be used to measure the voltages of the multiple batteries b1 to bn by switching between them.

[0022] DC / DC converter 16 is a circuit that converts DC power input from each of the plurality of batteries b1 to bn into DC power suitable for charging capacitor 18 and outputs it to capacitor 18. DC / DC converter 16 is also a circuit that converts DC power input from capacitor 18 into DC power suitable for charging each of the plurality of batteries b1 to bn and outputs it to each of the plurality of batteries b1 to bn.

[0023] The capacitor 18 stores the electric charge discharged from each of the plurality of batteries b1 to bn via the DC / DC converter 16. The capacitor 18 also discharges the stored electric charge to each of the plurality of batteries b1 to bn via the DC / DC converter 16.

[0024] The ammeter 20 measures the current value of the DC power input from each of the plurality of batteries b1 to bn and the current value of the DC power input from the capacitor 18. The ammeter 20 may also have a processing unit that measures the time during which the current flows. The processing unit further measures the amount of transfer of charge that has passed through the ammeter 20 based on the measured current value and time.

[0025] The changeover switches SWa to SWz are, for example, switching elements such as semiconductor relays, etc. The number of changeover switches included in the cell balance circuit 10 increases or decreases depending on the number of batteries connected.

[0026] The changeover switches SWa to SWz are provided on the wiring that electrically connects the DC / DC converter 16 and the plurality of batteries b1 to bn. In this specification, the wiring including the changeover switches SWa to SWz is referred to as a transfer circuit. The transfer circuit is a circuit for transferring electric charge between the plurality of batteries b1 to bn.

[0027] Returning to the explanation of Figure 1, the monitoring unit 12 monitors the amount of current supplied from the battery pack 2 to the load 4 and the amount of current supplied from the external power supply 6 to the battery pack 2. The monitoring unit 12 also monitors the amount of charge transfer measured by the ammeter 20 and identifies the battery that discharged the charge. The monitoring unit 12 monitors the voltage value of each of the multiple batteries b1 to bn using a voltage measurement circuit. The monitoring unit 12 monitors the temperature of each of the multiple batteries b1 to bn.

[0028] The monitoring unit 12 outputs various pieces of information relating to the acquired current amount, charge transfer amount, voltage value, temperature, etc. to the control unit 14 .

[0029] The control unit 14 controls the transfer of charge between the multiple batteries b1 to bn and controls the equalization by controlling the transfer circuit based on various information output by the monitoring unit 12. Note that the transfer of charge between the multiple batteries b1 to bn means transferring charge between the multiple batteries b1 to bn so that the remaining capacities of the multiple batteries b1 to bn are unbalanced.

[0030] The control unit 14 controls the transfer circuit to control the transfer of charge between the multiple batteries b1 to bn. Specifically, the control unit 14 controls the on / off of the selector switches SWa to SWz shown in Figure 2 to transfer charge from a battery with a high SOC (or a large remaining capacity) to a battery with a low SOC (or a small remaining capacity). The control unit 14 controls the on / off of the selector switches SWa to SWz to transfer charge from the high-voltage battery to the capacitor 18, and further controls the on / off of the selector switches SWa to SWz to transfer charge from the capacitor 18 to the low-voltage battery, thereby achieving the transfer of charge.

[0031] The control unit 14 also determines the voltage difference ΔV between the multiple batteries b1 to bn. The control unit 14 initiates equalization when the voltage difference ΔV is greater than an equalization start voltage Vth, which is set to a predetermined voltage value (e.g., 50 mV). The control unit 14 then controls the transfer circuit to charge the battery with a lower SOC (or a lower remaining capacity) from the battery with a higher SOC (or a higher remaining capacity). Specifically, the control unit 14 controls the on / off of the selector switches SWa to SWz to transfer charge from the battery with a higher SOC to the capacitor 18, and then controls the on / off of the selector switches SWa to SWz to transfer charge from the capacitor 18 to the battery with a lower SOC, thereby achieving equalization. Note that, in this specification, the voltage difference ΔV between the multiple batteries b1 to bn refers to the voltage difference between any two batteries. The control unit 14 initiates equalization when the voltage difference between any two batteries is greater than the equalization start voltage Vth. The current that flows through the delivery circuit as a result of equalization is called a balance current.

[0032] The control unit 14 also controls the timing at which the monitoring unit 12 acquires various information (information such as the amount of current and voltage values ​​monitored by the monitoring unit 12).

[0033] The monitoring unit 12 and the control unit 14 are realized by a microcomputer, a processor, etc. That is, the functions of the monitoring unit 12 and the control unit 14 are realized by the microcomputer, the processor, etc. executing a program stored in a memory.

[0034] [Regarding Equalization] The above-mentioned equalization will be explained using FIG. 3 . FIG. 3 is a diagram showing the time change in the voltage of each of the plurality of batteries b1 to bn. In the graph shown in FIG. 3 , the vertical axis represents voltage (mV) and the horizontal axis represents battery discharge capacity (mAh), as in the graphs shown in the following drawings. The explanation of FIG. 3 also describes a case where there are five batteries. (a) of FIG. 3 is a diagram showing the time change from when the control unit 14 starts supplying current from the five batteries b1 to b5 to the load 4 until it stops supplying current. (b) of FIG. 3 is an enlarged view of the area surrounded by the dotted line in (a) of FIG. 3 . Note that the explanation of FIG. 3 describes a specific example where the balancing current is not limited by the circuit configuration or where there is little variation in the deterioration of the five batteries b1 to b5. In other words, the explanation of FIG. 3 describes a specific example where there is little difference between the amount of current required to supply current from the five batteries b1 to b5 to the load 4 and the amount of current required to charge a battery with a high SOC to a battery with a low SOC.

[0035] In the graph shown in Figure 3(a), the dashed line at 4200 mV indicates the battery voltage when fully charged, and the dashed line at 2500 mV indicates the discharge cut-off voltage. Full charge refers to a state of charge in which the remaining capacity of the battery is 100%. The discharge cut-off voltage refers to the voltage at which the voltage of at least one of the multiple batteries b1 to bn stops discharging the multiple batteries b1 to bn, that is, the voltage when the remaining capacity of at least one battery is 0%. The battery voltage and discharge cut-off voltage when fully charged are the same in the graphs shown in the following drawings.

[0036] As shown in FIG. 3A, as time passes after the control unit 14 starts supplying current from the five batteries b1 to b5 to the load 4, the voltage of each of the five batteries b1 to b5 decreases.

[0037] In the graph shown in Figure 3(b), periods (A), (C), and (E) are periods during which the control unit 14 does not perform equalization and supplies current from the five batteries b1 to b5 to the load 4. Periods (B) and (D) are periods during which the control unit 14 performs equalization and supplies current from the five batteries b1 to b5 to the load 4.

[0038] As shown in (b) of Figure 3, during the period (A), the voltage difference ΔV between the five batteries b1 to b5 is smaller than the equalization start voltage Vth, so the control unit 14 supplies current from the five batteries b1 to b5 to the load 4.

[0039] At the start of period (B), the voltage difference ΔV between the five batteries b1 to b5 is greater than the equalization start voltage Vth, so the control unit 14 performs equalization and supplies current from the five batteries b1 to b5 to the load 4. Specifically, the control unit 14 identifies the battery with a high SOC and the battery with a low SOC, and starts charging from the battery with the high SOC to the battery with the low SOC. The control unit 14 then continues charging until the SOCs of the five batteries b1 to b5 are the same, that is, performs equalization. Note that while performing equalization, the control unit 14 acquires the voltages of the five batteries b1 to b5 measured by the voltage measurement circuit at predetermined intervals, re-identifies the battery with a high SOC and the battery with a low SOC, and starts charging from the battery with the high SOC to the battery with the low SOC.

[0040] During the period (B), the difference between the amount of current required to supply current from the five batteries b1 to b5 to the load 4 and the amount of current required to charge the battery with a lower SOC from the battery with a higher SOC is small, so the battery pack equalization device 8 can complete equalization before stopping the supply of current from the five batteries b1 to b5 to the load 4.

[0041] During the period (C), the voltage difference ΔV among the five batteries b1 to b5 is smaller than the equalization start voltage Vth. The control unit 14 supplies current from the five batteries b1 to b5 to the load 4 so as to maintain the difference in discharge capacity among the five batteries b1 to b5 constant.

[0042] At the start of period (D), the voltage difference ΔV between the five batteries b1 to b5 is greater than the equalization start voltage Vth, so the control unit 14 performs equalization in period (D) in the same way as in period (B), and supplies current from the five batteries b1 to b5 to the load 4.

[0043] During period (E), the voltage difference ΔV among the five batteries b1 to b5 is smaller than the equalization start voltage Vth. During period (E), the control unit 14 supplies current from the five batteries b1 to b5 to the load 4 so as to maintain the difference in discharge capacity among the five batteries b1 to b5 constant, as in period (C). Furthermore, at the end of period (E), the voltages of the five batteries b1 to b5 have all reached the discharge end voltage (i.e., 2500 mV).

[0044] As described above, when the balancing current is not limited by the circuit configuration, or when there is little variation in the deterioration of the multiple batteries b1 to bn, the battery pack equalization device 8 can make the voltage of each of the multiple batteries b1 to bn reach the discharge end voltage by performing equalization.

[0045] [Operation Example] Next, the operation performed by the battery pack equalization device 8 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the operation of the battery pack equalization device 8 shown in Fig. 1 .

[0046] First, the control unit 14 starts supplying current from the plurality of batteries b1 to bn to the load 4 (step S101).

[0047] The control unit 14 calculates the voltage difference ΔV between the battery with the highest voltage and the battery with the lowest voltage based on the voltages of each of the multiple batteries b1 to bn measured by the voltage measurement circuit, and determines whether the voltage difference ΔV is greater than the equalization start voltage Vth (step S102).

[0048] When it is determined that the voltage difference ΔV is equal to or less than the equalization start voltage Vth (No in step S102), the control unit 14 continues supplying current from the plurality of batteries b1 to bn to the load 4.

[0049] If it is determined that the voltage difference ΔV is greater than the equalization start voltage Vth (Yes in step S102), the control unit 14 starts equalization to equalize the remaining capacities of the plurality of batteries b1 to bn (step S103). Note that while equalization is being performed, the control unit 14 may continue or stop supplying current from the plurality of batteries b1 to bn to the load 4 in response to a request from the load 4.

[0050] The control unit 14 determines that the voltage of at least one battery measured by the voltage measurement circuit has reached the discharge end voltage (step S104). After the determination in step S104, the control unit 14 stops the supply of current from the multiple batteries b1 to bn to the load 4. Furthermore, the control unit 14 determines whether any battery has a remaining charge (step S105).

[0051] If it is determined that there is no battery with remaining charge (No in step S105), the control unit 14 charges the plurality of batteries b1 to bn using the external power supply 6 (step S107).

[0052] If it is determined that there is a battery with remaining charge (Yes in step S105), the control unit 14 discharges the battery that has not yet reached the discharge end voltage until the voltage reaches the discharge end voltage, and measures the amount of charge discharged by the battery before the discharge end voltage is reached (step S106). Specifically, the control unit 14 obtains the amount of charge transfer measured by the ammeter 20 and also obtains information identifying the battery that discharged the charge.

[0053] In step S106, the control unit 14 determines the voltage and current of the batteries when the transfer of charge between the batteries b1 to bn begins, based on the charge amount measured by the ammeter 20. The control unit 14 determines the voltage and current amount that will complete the transfer of charge before the start of equalization.

[0054] After step S106, the control unit 14 charges the plurality of batteries b1 to bn using the external power supply 6 (step S107). Note that the control unit 14 may charge the plurality of batteries b1 to bn using the charge stored in step S106. For example, when charging the plurality of batteries b1 to bn using the charge stored in step S106, the control unit 14 distributes the charge evenly to each of the plurality of batteries b1 to bn, or distributes the charge so that the magnitude relationship of the charge amounts is reverse to that measured in step S106.

[0055] The control unit 14 resumes the supply of current from the plurality of batteries b1 to bn to the load 4 (step S108).

[0056] The control unit 14 controls the transfer circuit based on the charge amount measured in step S106 to transfer charge among the plurality of batteries b1 to bn for a predetermined period of time (step S109). Specifically, the control unit 14 starts transferring charge among the plurality of batteries b1 to bn based on the voltage and current amount determined from the measured charge amount. The control unit 14 also transfers charge among the plurality of batteries b1 to bn so as to reverse the magnitude relationship of the charge amount (consumed charge amount) discharged by each battery in step S106. The predetermined period is a period during which the voltage difference ΔV calculated by the control unit 14 is smaller than the equalization start voltage Vth. The predetermined period may also be a period from when the plurality of batteries b1 to bn start discharging until a certain amount of charge is discharged, regardless of whether the voltage difference ΔV is greater than the equalization start voltage Vth.

[0057] In step S106, if the plurality of batteries have not reached the discharge cut-off voltage, the control unit 14 discharges each battery until the voltage reaches the discharge cut-off voltage, and measures the amount of charge discharged by each battery until the discharge cut-off voltage is reached. The control unit 14 may also store the charge discharged by the batteries in the capacitor 18.

[0058] In step S107, the control unit 14 may charge the batteries b1 to bn until the remaining capacity of each of the batteries b1 to bn reaches 100% (i.e., fully charged), or may charge the batteries to a certain percentage. The control unit 14 may also equalize the remaining capacity of the batteries b1 to bn during charging so that the remaining capacity of each of the batteries b1 to bn reaches 100%.

[0059] In addition, in the operation example shown in FIG. 4, step S103 corresponds to an equalization step performed by the control unit 14, step S106 corresponds to a measurement step performed by the control unit 14, and step S109 corresponds to a transfer step performed by the control unit 14.

[0060] As explained above, the battery pack equalization device 8 measures the imbalance in the amount of consumed charge among the plurality of batteries b1 to bn in the measurement step before performing equalization, and transfers charge based on the imbalance.

[0061] Furthermore, before performing equalization, the battery pack equalizer 8 transfers charge among the plurality of batteries b1 to bn so as to increase the remaining capacity of the most deteriorated battery and decrease the remaining capacity of the least deteriorated battery. In other words, before equalization, charge is transferred among the plurality of batteries b1 to bn so as to cancel out the imbalance in consumed charge measured in advance. This allows the battery pack equalizer 8 to complete equalization even if there is a large difference between the amount of current required to supply current from the plurality of batteries b1 to bn to the load 4 and the amount of current required to charge a battery with a higher SOC to a battery with a lower SOC.

[0062] Furthermore, the battery pack equalization device 8 starts transferring charge between the multiple batteries b1 to bn based on the determined battery voltage and current amount, so that the transfer of charge can be completed before equalization begins.

[0063] Furthermore, the battery pack equalization device 8 completes the transfer of charge during the period in which the voltage difference ΔV between the multiple batteries b1 to bn is smaller than the equalization start voltage Vth, so that the time required to perform equalization can be left.

[0064] Furthermore, the battery pack equalization device 8 charges the plurality of batteries b1 to bn using the charge discharged from the batteries in the measurement step (S106), thereby reducing the amount of charge required to charge the plurality of batteries b1 to bn supplied from the external power source 6.

[0065] Furthermore, when the battery pack equalization device 8 uses the charge stored in the measurement step (S106) to charge the plurality of batteries b1 to bn, the battery pack equalization device 8 distributes the charge in a manner that is opposite to the magnitude relationship of the charge amounts measured in the measurement step (S106), thereby distributing more charge to batteries with smaller capacities (or batteries with more advanced degradation). Since batteries with smaller capacities reach full charge more quickly than batteries with larger capacities (or batteries with less advanced degradation), the battery pack equalization device 8 distributes more charge to batteries with smaller capacities, thereby shortening the time required for equalization during charging. Furthermore, after the measurement step (S106), the battery pack equalization device 8 distributes more charge to batteries with smaller capacities to maintain the voltage of the batteries high, thereby slowing the rate of deterioration of the batteries.

[0066] The operation of the battery pack equalization device 8 described in FIG. 4 will be explained using a specific example shown in FIGS. 5A and 5B. The explanations in FIGS. 5A and 5B describe a case in which there are five batteries, and battery b3 is the most deteriorated of the five batteries b1 to b5. The specific examples shown in FIGS. 5A and 5B are examples in which the balancing current is limited by the circuit configuration or the deterioration of the five batteries b1 to b5 varies greatly. In other words, the explanations in FIGS. 5A and 5B describe a specific example in which there is a large difference between the amount of current required to supply current from the five batteries b1 to b5 to the load 4 and the amount of current required to charge the battery with a higher SOC from the battery with a lower SOC.

[0067] 5A is a diagram showing a specific example corresponding to steps S101 to S104 in FIG. 3. (a) of FIG. 5A is a diagram showing the time change in the voltage of each of the five batteries b1 to b5 when the control unit 14 equalizes the five batteries b1 to b5 without transferring charge among them for a predetermined period of time. (b) of FIG. 5A is a schematic diagram showing the remaining capacity of each of the five batteries b1 to b5 at the time shown in (a) of FIG. 5A. Note that in (b) of FIG. 5A, the diagonal lines shown on each of the five batteries b1 to b5 indicate the remaining capacity of each of the five batteries b1 to b5.

[0068] As shown in (a) of Fig. 5A, at time (I), the control unit 14 starts supplying current from the five batteries b1 to b5 to the load 4. This is the operation corresponding to step S101 in Fig. 4.

[0069] At time (II), the voltage difference ΔV between the five batteries b1 to b5 is smaller than the equalization start voltage Vth, so the control unit 14 continues to supply current from the five batteries b1 to b5 to the load 4. This is the operation that corresponds to when the control unit 14 determines No in step S102 of FIG.

[0070] At time (III), the voltage difference ΔV between the five batteries b1 to b5 is greater than the equalization start voltage Vth, so the control unit 14 starts equalization. This operation corresponds to step S103 in FIG. 4 (i.e., the equalization step).

[0071] During the periods (I) to (III), the control unit 14 only supplies current from the five batteries b1 to b5 to the load 4. This period is called a normal discharge period.

[0072] At time (IV), the voltage of at least one of the five batteries b1 to b5 has reached the discharge end voltage, so the control unit 14 stops the supply of current from the five batteries b1 to b5 to the load 4. This operation corresponds to step S104 in FIG.

[0073] During the periods (III) to (IV), the control unit 14 performs the equalization described in Fig. 2 and supplies current from the five batteries b1 to b5 to the load 4. This period is called the balancing period.

[0074] As shown in (b) of FIG. 5A , the remaining capacity of each of the five batteries b1 to b5 decreases from (I) to (IV). As explained in (a) of FIG. 5A , the periods (I) to (III) are normal discharge periods, during which no charge is transferred between the five batteries b1 to b5. Therefore, the remaining capacity of the most degraded battery b3 is the lowest. Furthermore, the periods (III) to (IV) are balancing periods, during which equalization is performed by charging the battery with the higher SOC to the battery with the lower SOC, while supplying current from the five batteries b1 to b5 to the load 4. During the periods (III) to (IV), the difference between the amount of current required to supply current from the five batteries b1 to b5 to the load 4 and the amount of current required to charge the battery with the higher SOC to the battery with the lower SOC is large, so the battery pack equalization device 8 cannot complete equalization. Therefore, at the time point (IV), the remaining capacities of the five batteries b1 to b5 do not simultaneously reach 0%.

[0075] FIG. 5B is a diagram showing a specific example corresponding to steps S102 to S104 and steps S108 to S109 in FIG. 4 . FIG. 5B is a diagram showing a specific example when, after FIG. 5A , the control unit 14 executes step S106 (i.e., the measurement step) in FIG. 4 and resumes the supply of current from the five batteries b1 to b5 to the load 4. (a) of FIG. 5B is a diagram showing the time change in the voltage of each of the five batteries b1 to b5 when the control unit 14 transfers charge among the five batteries b1 to b5 and equalizes the five batteries b1 to b5 over a predetermined period. (b) of FIG. 5B is a schematic diagram showing the remaining capacity of each of the five batteries b1 to b5 at the time shown in (a) of FIG. 5B . Note that in (b) of FIG. 5B , the diagonal lines shown for each of the five batteries b1 to b5 indicate the remaining capacity of each of the five batteries b1 to b5.

[0076] As shown in (a) of Figure 5B, at time (V), the control unit 14 resumes supplying current from the five batteries b1 to b5 to the load 4. This is the operation corresponding to step S108 in Figure 4.

[0077] At time (VI), the voltage of any one of the five batteries b1 to b5 has reached the battery voltage at which charge transfer between the five batteries b1 to b5 begins, so the control unit 14 starts transferring charge between the five batteries b1 to b5. This corresponds to step S109 in FIG. 4 (i.e., the transfer step).

[0078] During the periods (V) to (VI), the control unit 14 only supplies current from the five batteries b1 to b5 to the load 4 (normal discharge period).

[0079] At time (VII), the voltage difference ΔV between the five batteries b1 to b5 is greater than the equalization start voltage Vth, so the control unit 14 starts equalization. This operation corresponds to step S103 in FIG. 4 (i.e., the equalization step).

[0080] During the periods (VI) to (VII), the control unit 14 transfers charge among the five batteries b1 to b5, and also supplies current from the five batteries b1 to b5 to the load 4. This period is called the pre-charge transition period.

[0081] At time (VIII), the voltage of at least one of the five batteries b1 to b5 has reached the discharge end voltage, so the control unit 14 stops the supply of current from the five batteries b1 to b5 to the load 4. This operation corresponds to step S104 in FIG.

[0082] During the periods (VII) to (VIII), the control unit 14 performs the equalization described with reference to FIG. 2 and supplies current from the five batteries b1 to b5 to the load 4 (balancing period).

[0083] As shown in (b) of Figure 5B, the period from (V) to (VI) is a normal discharge period, and so the remaining capacity of each of the five batteries b1 to b5 decreases, just as in the period from (I) to (II) shown in (b) of Figure 5A. Also, at time (VI), just as at time (II), battery b3 has the smallest remaining capacity.

[0084] Furthermore, since the period from (VI) to (VII) is a pre-charge transition period, at time (VII), battery b3 has the largest remaining capacity, and batteries b1 and b5 have the smallest remaining capacities. This is because the control unit 14 transfers charge among the five batteries b1 to b5 so that the magnitude relationship of the remaining capacities among the five batteries b1 to b5 at time (IV) shown in (b) of Figure 5A is reversed.

[0085] The period from (VII) to (VIII) is a balancing period, during which, similar to the period from (III) to (IV) shown in FIG. 5A (b), equalization is performed by charging the battery with the higher SOC to the battery with the lower SOC, while supplying current from the five batteries b1 to b5 to the load 4. Because the control unit 14 has transferred charge during the period from (VI) to (VII), the assembled battery equalization device 8 can complete equalization. Therefore, at the time point (VIII), the remaining capacities of the five batteries b1 to b5 simultaneously become 0%.

[0086] The pre-charge transition period (i.e., the period from (VI) to (VII)) does not have to be immediately before the balancing period (i.e., the period from (VII) to (VIII)). For example, the sequence may be configured so that the pre-charge transition period is followed by a normal discharge period and then the balancing period.

[0087] [Effects] As explained above, the battery pack equalization device 8 according to this embodiment is an assembled battery equalization device 8 that equalizes the remaining capacity of each of a plurality of series-connected batteries b1 to bn, and includes a transfer circuit that transfers charge between the plurality of batteries b1 to bn, a voltage measurement circuit that measures the voltage of each of the plurality of batteries b1 to bn, an ammeter 20 that measures the amount of charge transferred in each of the plurality of batteries b1 to bn, and a control unit 14 that controls the transfer circuit, and when the voltage of at least one battery measured by the voltage measurement circuit reaches a discharge cut-off voltage that is a voltage at which discharge of the plurality of batteries b1 to bn is stopped, the control unit 14 detects that the voltage of a battery that has not reached the discharge cut-off voltage has reached the discharge cut-off voltage. a measurement step (S106) of discharging a battery that has not yet reached the discharge end voltage until the voltage reaches the discharge end voltage and measuring the amount of charge discharged by the battery until the discharge end voltage is reached; a transfer step (S109) of causing the charged batteries b1 to bn to supply current to a load 4, and then transferring charge between the batteries b1 to bn for a predetermined period by controlling a transfer circuit based on the amount of charge measured in the measurement step (S106); and an equalization step (S103) of starting equalization after the transfer step (S109) when the voltage difference ΔV between the batteries b1 to bn is greater than an equalization start voltage Vth that is set at a predetermined voltage value.

[0088] In this battery pack equalization device 8, before equalization, the battery pack equalization device 8 measures the imbalance in the amount of consumed charge among the plurality of batteries b1 to bn in a measurement step, and transfers charge based on the imbalance. This allows the battery pack equalization device 8 to equalize the SOC of the plurality of batteries b1 to bn even when the balancing current is limited by a circuit or when there is a large variation in the deterioration of the plurality of batteries b1 to bn.

[0089] In addition, in the battery pack equalization device 8 according to this embodiment, in the transfer step (S109), the control unit 14 transfers charge among the plurality of batteries b1 to bn so that the magnitude relationship of the charge amounts discharged from each battery is reversed from that of the amount discharged from each battery in the measurement step (S106).

[0090] Before performing equalization, the battery pack equalizer 8 transfers charge among the batteries b1 to bn so as to increase the remaining capacity of the most deteriorated battery and decrease the remaining capacity of the least deteriorated battery. In other words, before equalization, charge is transferred among the batteries b1 to bn so as to cancel out the imbalance in consumed charge measured in advance. This allows the battery pack equalizer 8 to complete equalization even if there is a large difference between the amount of current required to supply current from the batteries b1 to bn to the load 4 and the amount of current required to charge a battery with a higher SOC to a battery with a lower SOC.

[0091] Furthermore, in the assembled battery equalization device 8 according to this embodiment, the predetermined period is a period during which the voltage difference ΔV among the plurality of batteries b1 to bn is smaller than the equalization start voltage Vth.

[0092] Such a battery pack equalization device 8 completes the transfer of charge during the period in which the voltage difference ΔV between the multiple batteries b1 to bn is smaller than the equalization start voltage Vth, thereby leaving the time necessary to perform equalization.

[0093] Furthermore, in the battery pack equalization device 8 according to this embodiment, the control unit 14 determines the battery voltage and current amount at the time when the transfer of charge between the plurality of batteries b1 to bn is started in the transfer step (S109) based on the amount of charge measured in the measurement step (S106).

[0094] Such a battery pack equalization device 8 starts transferring charge between multiple batteries b1 to bn based on the determined battery voltage and current amount, so that the transfer of charge can be completed before equalization begins.

[0095] Furthermore, in the battery pack equalization device 8 according to this embodiment, the control unit 14 further stores the charge discharged from the battery in the measurement step (S106) and uses the stored charge when charging the plurality of batteries b1 to bn.

[0096] Such a battery pack equalization device 8 charges the multiple batteries b1 to bn using the charge discharged from the batteries in the measurement step (S106), thereby reducing the amount of charge required to charge the multiple batteries b1 to bn that is supplied from the external power source 6.

[0097] Furthermore, in the battery pack equalization device 8 according to this embodiment, when the charge stored in the measurement step (S106) is used to charge a plurality of batteries, the control unit distributes the charge so that the magnitude relationship of the charge amounts measured in the measurement step (S106) is reversed.

[0098] When the electric charge stored in the measurement step (S106) is used to charge the plurality of batteries b1 to bn, the battery pack equalization device 8 distributes the electric charge in a manner opposite to the magnitude relationship of the electric charge measured in the measurement step (S106), thereby distributing more electric charge to batteries with smaller capacities (or batteries with more advanced degradation). Since batteries with smaller capacities reach full charge more quickly than batteries with larger capacities (or batteries with less advanced degradation), the battery pack equalization device 8 distributes more electric charge to batteries with smaller capacities, thereby shortening the time required for equalization during charging. Furthermore, after the measurement step (S106), the battery pack equalization device 8 distributes more electric charge to batteries with smaller capacities to maintain the voltage of the batteries high, thereby slowing the rate of deterioration of the batteries.

[0099] Furthermore, the battery pack equalization method according to this embodiment is a battery pack equalization method using a battery pack equalizer 8 that equalizes the remaining capacity of each of a plurality of series-connected batteries b1 to bn, and the battery pack equalization device 8 includes a transfer circuit that transfers charge between the plurality of batteries b1 to bn, a voltage measurement circuit that measures the voltage of each of the plurality of batteries b1 to bn, and an ammeter 20 that measures the amount of charge transferred in each of the plurality of batteries b1 to bn. The battery pack equalization method includes the steps of: when the voltage of at least one battery measured by the voltage measurement circuit reaches a discharge cut-off voltage, which is a voltage that stops discharging of the plurality of batteries b1 to bn, the voltage of a battery that has not reached the discharge cut-off voltage decreases to the discharge cut-off voltage the discharge end voltage is reached, and the amount of charge discharged by the battery until the discharge end voltage is reached is measured; a transfer step (S109) in which, after supplying current from the charged batteries b1 to bn to a load 4, charge is transferred between the batteries b1 to bn for a predetermined period by controlling a transfer circuit based on the amount of charge measured in the measurement step (S106); and an equalization step (S103) in which, after the transfer step (S109), equalization is started when a voltage difference ΔV between the batteries b1 to bn is greater than an equalization start voltage Vth set at a predetermined voltage value.

[0100] In this battery pack equalization method, prior to equalization, the imbalance in the amount of consumed charge among the plurality of batteries b1 to bn is measured in a measurement step, and charge is transferred based on the imbalance. This makes it possible to equalize the SOC of the plurality of batteries b1 to bn even when the balancing current is limited by a circuit or when there is a large variation in the deterioration of the plurality of batteries b1 to bn.

[0101] The program according to the present embodiment causes a computer to execute the above-described battery pack equalization method.

[0102] Such a program provides the same effects as the battery pack equalization method described above.

[0103] [Modifications] While the battery pack equalization device and the like according to the present disclosure have been described above based on the above-described embodiment, the present disclosure is not limited to the above-described embodiment. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the above-described embodiment and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects.

[0104] In the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0105] In the above-described embodiments, some or all of the functions of the components may be realized by a processor such as a CPU executing a program.

[0106] Some or all of the components constituting each of the above devices may be configured as an IC card or a standalone module that can be attached to or detached from each device. The IC card or module is a computer system composed of a microprocessor, ROM, RAM, etc. The IC card or module may include a super multi-function LSI. The IC card or module achieves its functions when the microprocessor operates in accordance with a computer program. The IC card or module may be tamper-resistant.

[0107] [Additional Notes] The above description of the embodiments discloses the following techniques.

[0108] (Technology 1) A battery pack equalization device that equalizes the remaining capacity of a plurality of batteries connected in series, the device comprising: a transfer circuit that transfers charge between the plurality of batteries; a voltage measurement circuit that measures the voltage of each of the plurality of batteries; an ammeter that measures the amount of charge transferred in each of the plurality of batteries; and a control unit that controls the transfer circuit, wherein when the voltage of at least one of the batteries measured by the voltage measurement circuit reaches a discharge cut-off voltage that is a voltage that stops discharging of the plurality of batteries, the control unit controls the voltage of each of the batteries that has not reached the discharge cut-off voltage to be equalized until the voltage reaches the discharge cut-off voltage. a measuring step of discharging the batteries that have not yet reached the discharge end voltage and measuring the amount of charge discharged from the batteries before the discharge end voltage is reached; a transferring step of transferring charge between the plurality of batteries by controlling the transferring circuit based on the amount of charge measured in the measuring step for a predetermined period after supplying current from the charged plurality of batteries to a load; and an equalizing step of starting the equalization after the transferring step when a voltage difference between the plurality of batteries is greater than an equalization start voltage that is set at a predetermined voltage value.

[0109] (Technology 2) In the battery pack equalization device described in Technology 1, in the transfer step, the control unit transfers charge between the plurality of batteries so that the magnitude relationship between the amounts of charge discharged from each of the batteries in the measurement step is reversed.

[0110] (Technology 3) The battery pack equalizer according to Technology 1 or 2, wherein the predetermined period is a period during which the voltage difference among the plurality of batteries is smaller than the equalization start voltage.

[0111] (Technology 4) The battery pack equalization device described in any one of Technologies 1 to 3, wherein the control unit determines the voltage and current of the batteries when starting to transfer charge between the plurality of batteries in the transfer step based on the amount of charge measured in the measurement step.

[0112] (Technology 5) The battery pack equalization device according to any one of Technologies 1 to 4, wherein the control unit further stores the charge discharged from the batteries in the measurement step and uses the stored charge when charging the plurality of batteries.

[0113] (Technology 6) In the battery pack equalization device described in Technology 5, when the charge stored in the measurement step is used to charge the plurality of batteries, the control unit distributes the charge so that the magnitude relationship of the charge amounts measured in the measurement step is reversed.

[0114] (Technology 7) A battery pack equalization method using a battery pack equalization device that equalizes the remaining capacity of each of a plurality of batteries connected in series, the battery pack equalization device comprising a transfer circuit that transfers charge between the plurality of batteries, a voltage measurement circuit that measures the voltage of each of the plurality of batteries, and an ammeter that measures the amount of charge transferred in each of the plurality of batteries, the battery pack equalization method including: when the voltage of at least one of the batteries measured by the voltage measurement circuit reaches a discharge end voltage that is a voltage at which discharge of the plurality of batteries is stopped, a voltage of a battery that has not reached the discharge end voltage reaches the discharge end voltage; a measuring step of discharging the batteries that have not yet reached the discharge end voltage until the discharge end voltage is reached, and measuring the amount of charge discharged from the batteries until the discharge end voltage is reached; a transferring step of transferring charge between the plurality of batteries for a predetermined period of time after supplying current from the charged plurality of batteries to a load by controlling the transferring circuit based on the amount of charge measured in the measuring step; and an equalizing step of starting the equalization after the transferring step when a voltage difference between the plurality of batteries is larger than an equalization start voltage that is set at a predetermined voltage value.

[0115] (Technology 8) A program for causing a computer to execute the battery pack equalization method according to Technology 7.

[0116] The assembled battery equalizing device and the like according to the present disclosure are useful, for example, as a device for equalizing the remaining capacity of each of a plurality of batteries connected in series.

[0117] 2 battery pack 4 load 6 external power supply 8 battery pack equalizer 10 cell balance circuit 12 monitoring unit 14 control unit 16 DC / DC converter 18 capacitor 20 ammeter b1 to bn multiple batteries V1 to Vn multiple voltmeters SWa to SWz changeover switch

Claims

1. A battery equalization device that equalizes a plurality of batteries connected in series to make the remaining capacity of each battery the same, comprising: a transfer circuit that transfers charge between the plurality of batteries; a voltage measurement circuit that measures the voltage of each of the plurality of batteries; an ammeter that measures the amount of charge transferred in each of the plurality of batteries; and a control unit that controls the transfer circuit, wherein the control unit performs a measurement step in which, when the voltage of at least one of the batteries measured by the voltage measurement circuit reaches a discharge end voltage that is a voltage at which discharge of the plurality of batteries is stopped, the control unit discharges the batteries that have not reached the discharge end voltage until their voltages reach the discharge end voltage, and measures the amount of charge discharged by the batteries until the discharge end voltage is reached; and a transfer step in which, after current is supplied from the charged plurality of batteries to a load, charge is transferred between the plurality of batteries for a predetermined period of time by controlling the transfer circuit based on the amount of charge measured in the measurement step. After the transferring step, an equalizing step is performed in which the equalization is started when the voltage difference among the plurality of batteries is greater than an equalization start voltage that is set as a predetermined voltage value.

2. The battery pack equalization device according to claim 1, wherein in the transfer step, the control unit transfers charge between the plurality of batteries so that the magnitude relationship of the amount of charge discharged from each of the batteries in the measurement step is reversed.

3. The battery pack equalization device according to claim 1, wherein the predetermined period is a period during which the voltage difference between the plurality of batteries is smaller than the equalization start voltage.

4. The battery pack equalization device according to claim 1, wherein the control unit determines the voltage and current of the batteries when the transfer of charge between the plurality of batteries begins in the transfer step, based on the amount of charge measured in the measurement step.

5. The battery pack equalization device according to claim 1, wherein the control unit further stores the charge discharged from the batteries in the measurement step, and uses the stored charge when charging the plurality of batteries.

6. The battery pack equalization device according to claim 5, wherein when the charge stored in the measurement step is used to charge the plurality of batteries, the control unit distributes the charge so that the magnitude relationship of the charge amounts measured in the measurement step is reversed.

7. A method for equalizing a plurality of batteries connected in series by a battery equalization device that equalizes the remaining capacity of each battery, the battery equalization device comprising: a transfer circuit that transfers charge between the plurality of batteries; a voltage measurement circuit that measures the voltage of each of the plurality of batteries; and an ammeter that measures the amount of charge transferred in each of the plurality of batteries, the battery equalization method comprising: a measurement step of, when the voltage of at least one of the batteries measured by the voltage measurement circuit reaches a discharge end voltage that is a voltage at which discharge of the plurality of batteries is stopped, discharging the batteries that have not reached the discharge end voltage until their voltages reach the discharge end voltage, and measuring the amount of charge discharged by the batteries until the discharge end voltage is reached; and a transfer step of, after supplying current from the charged batteries to a load, transferring charge between the plurality of batteries for a predetermined period by controlling the transfer circuit based on the amount of charge measured in the measurement step. an equalization step of starting the equalization when a voltage difference among the plurality of batteries is greater than an equalization start voltage that is set as a predetermined voltage value, after the transfer step.

8. A program for causing a computer to execute the battery pack equalization method according to claim 7.

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