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

Abstract

The battery pack equalization device (8) has a transfer circuit, a voltage measurement circuit, a current meter (20), and a control section (14), and the control section (14) performs: a measurement step (S106) of discharging a battery until a voltage of a battery that does not reach a discharge termination voltage reaches the discharge termination voltage at a time point when a voltage of at least one battery reaches the discharge termination voltage, and measuring a discharged charge amount; a transfer step (S109) of performing transfer of charge among the plurality of batteries (b1-bn) based on the charge amount measured in the measurement step (S106); and an equalization step (S103) of starting equalization when a voltage difference (ΔV) among the plurality of batteries (b1-bn) is greater than an equalization start voltage (Vth) after the transfer step (S109).

Description

Technical Field

[0001] This disclosure relates to a battery pack balancing device, etc., for making the remaining capacity of each battery in a series-connected plurality of batteries consistent. Background Technology

[0002] In order to make the SOC (State of Charge) of each battery in a series connection the same, there are known techniques for charging and discharging (balancing current) among the batteries.

[0003] For example, Patent Document 1 discloses an adjustment device for the stored charge of a coil that minimizes the balance current in order to suppress power loss caused by the balance current.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6641665 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the adjustment device described in Patent Document 1, if the balancing current is limited by the circuit structure or if the deviation of the deterioration of multiple batteries is large, the difference between the current supplied to the load and the balancing current becomes large, which may result in the inability to make the SOC of multiple batteries the same.

[0009] Therefore, the purpose of this disclosure is to provide a battery pack balancing device that can make the SOC of multiple batteries the same even when the balancing current is limited by the circuit structure or when the degradation deviation of multiple batteries is large.

[0010] Solution for solving the problem

[0011] To achieve the above objectives, one aspect of the battery pack balancing device disclosed herein is a battery pack balancing device that performs balancing to ensure that the remaining capacity of each battery in a series-connected plurality of batteries is consistent. The battery pack balancing device comprises: a transfer circuit for transferring charge among the plurality of batteries; a voltage measuring circuit for measuring the voltage of each battery in the plurality of batteries; an ammeter for measuring the amount of charge movement in each battery in the plurality of batteries; and a control unit for controlling the transfer circuit, wherein the control unit executes: a measurement step, whereby the voltage of at least one battery measured by the voltage measuring circuit reaches a voltage at which discharging of the plurality of batteries is stopped, i.e., discharge. The termination voltage timing point involves discharging the batteries that have not reached the discharge termination voltage until their voltage reaches the discharge termination voltage, and measuring the amount of charge discharged by the batteries up to reaching the discharge termination voltage; a transfer step involves controlling the transfer circuit based on the amount of charge measured in the measurement step during a predetermined period after supplying current from the charged batteries to the load, thereby transferring charge among the batteries; and an equalization step involves starting the equalization process after the transfer step when the voltage difference between the batteries is greater than an equalization start voltage set at a predetermined voltage value.

[0012] To achieve the above objectives, one aspect of this disclosure relates to a battery pack balancing method, which is a method performed by a battery pack balancing device. The battery pack balancing device performs balancing to ensure that the remaining capacity of each battery in a series-connected plurality of batteries is consistent. The battery pack balancing device includes: a transfer circuit for transferring charge among the plurality of batteries; a voltage measuring circuit for measuring the voltage of each battery in the plurality of batteries; and an ammeter for measuring the amount of charge movement in each battery in the plurality of batteries. The battery pack balancing method includes a measurement step whereby the voltage of at least one battery measured by the voltage measuring circuit reaches a point where the discharge of the plurality of batteries stops. The process involves: a voltage point, i.e., the discharge termination voltage, at which the battery that has not reached the discharge termination voltage is discharged until its voltage reaches the discharge termination voltage, and measuring the amount of charge discharged by the battery until the discharge termination voltage is reached; a transfer step, in which, after supplying current from the charged batteries to the load, the transfer circuit is controlled within a predetermined period based on the amount of charge measured in the measurement step, thereby transferring charge among the batteries; and an equalization step, in which, after the transfer step, equalization is initiated when the voltage difference among the batteries is greater than an equalization start voltage set at a predetermined voltage value.

[0013] To achieve the above objectives, one aspect of this disclosure involves a program for causing a computer to execute the battery pack balancing method.

[0014] Invention Effects

[0015] According to this disclosure, a battery pack balancing device is provided that enables multiple batteries to have the same SOC even when the balancing current is limited by the circuit or when the degradation deviation of multiple batteries is large. Attached Figure Description

[0016] Figure 1 It is a block diagram showing the structure of a system including a battery pack balancing device.

[0017] Figure 2 This is a circuit diagram showing the detailed structure of a single-cell battery balancing circuit.

[0018] Figure 3 It is a graph showing the time-varying voltage of each cell in a plurality of batteries.

[0019] Figure 4 It is shown Figure 1 The flowchart shows the operation of the battery pack balancing device.

[0020] Figure 5A It is shown that... Figure 3 The figure shows a specific example corresponding to steps S101 to S104.

[0021] Figure 5B It is shown that... Figure 3 A specific example of steps S102-S104 and steps S108-S109 is shown in the figure. Detailed Implementation

[0022] The embodiments of this disclosure will now be described in detail with the aid of the accompanying drawings. Furthermore, the embodiments described below are all specific examples of this disclosure. The numerical values, structural elements, configurations and connections of structural elements, steps, order of steps, display examples, etc., shown in the following embodiments are examples and are not intended to limit this disclosure. Therefore, structural elements in the following embodiments not described in the independent claims of this disclosure are described as arbitrary structural elements. Additionally, the figures are not necessarily strictly illustrative. In the figures, substantially identical structures are labeled with the same reference numerals, and repeated descriptions are omitted or simplified.

[0023] (Implementation Method)

[0024] [structure]

[0025] Figure 1This is a block diagram showing the structure of a system including a battery pack balancing device 8. (See diagram for example.) Figure 1 As shown, this disclosure consists of a battery pack 2, a load 4, an external power supply 6, and a battery pack balancing device 8.

[0026] Battery pack 2 is a battery obtained by connecting multiple batteries b1 to bn (n is an integer of 2 or more) in series. Alternatively, battery pack 2 can also be a battery obtained by connecting multiple batteries b1 to bn in parallel. Furthermore, the batteries used for the multiple batteries b1 to bn are rechargeable batteries, such as lead-acid batteries or lithium-ion batteries.

[0027] Load 4 is a device that operates using power supplied by battery pack 2, such as an actuator, motor, or control device.

[0028] External power source 6 is the power source that supplies power to battery pack 2. External power source 6 includes an AC (Alternating Current) / DC (Direct Current) converter that converts AC power to DC power.

[0029] The battery pack balancing device 8 is a device for balancing the remaining capacity of each battery among the multiple batteries b1 to bn in the battery pack 2. The battery pack balancing device 8 performs balancing by performing charge and discharge operations among the multiple batteries b1 to bn to eliminate SOC differences or voltage differences among the multiple batteries b1 to bn. Detailed explanations of the balancing process will be provided later.

[0030] The battery pack balancing device 8 includes a single cell balancing circuit 10, a monitoring unit 12, and a control unit 14.

[0031] The single-cell balancing circuit 10 is a circuit used to move charge between multiple cells b1~bn. Figure 2 This is a circuit diagram showing the detailed structure of the single-cell balancing circuit 10. Furthermore, Figure 2 The structure of the single-cell battery balancing circuit 10 shown is an example. As long as the function of the single-cell battery balancing circuit 10 is realized, the deformation of each structural element is within the scope of this disclosure.

[0032] like Figure 2 As shown, the single-cell battery balancing circuit 10 includes multiple voltmeters V1 to Vn (n is an integer greater than 2), a DC / DC converter 16, a capacitor 18, an ammeter 20, and switching switches SWa to SWz.

[0033] Multiple voltmeters V1 to Vn measure the voltage of each battery in a series-connected network of batteries b1 to bn. Each voltmeter V1 to Vn is connected to both the positive and negative terminals of the batteries b1 to bn to measure the voltage between the terminals of each battery. In this specification, the multiple voltmeters V1 to Vn and the wiring connected to the positive and negative terminals of the batteries b1 to bn are referred to as a voltage measurement circuit. Furthermore, the number of voltmeters in the single-cell balancing circuit 10 increases or decreases depending on the number of batteries connected. Alternatively, a single voltmeter can be used to measure the voltage of each battery in the multiple batteries b1 to bn while switching between them.

[0034] DC / DC converter 16 is a circuit that converts DC power input from each of the multiple batteries b1 to bn into DC power suitable for charging capacitor 18 and then outputs it to capacitor 18. Additionally, DC / DC converter 16 is a circuit that converts DC power input from capacitor 18 into DC power suitable for charging each of the multiple batteries b1 to bn and then outputs it to each of the multiple batteries b1 to bn respectively.

[0035] Capacitor 18 stores the charge discharged by the multiple batteries b1~bn via DC / DC converter 16. Additionally, capacitor 18 discharges the stored charge to the multiple batteries b1~bn via DC / DC converter 16.

[0036] 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. Furthermore, the ammeter 20 may also have a processing unit that measures the time of current flow. Based on the measured current value and time, the processing unit also measures the amount of charge moved through the ammeter 20.

[0037] The switching switches SWa~SWz are, for example, switching elements such as semiconductor relays. Furthermore, the number of switching switches in the single-cell battery balancing circuit 10 increases or decreases depending on the number of batteries connected.

[0038] Switches SWA~SWz are provided in the wiring that electrically connects the DC / DC converter 16 to multiple batteries b1~bn. Furthermore, in this specification, this wiring including switches SWA~SWz is referred to as a transfer circuit. A transfer circuit is a circuit used for transferring charge between the multiple batteries b1~bn.

[0039] Return to Figure 1As described above, 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 source 6 to the battery pack 2. Additionally, the monitoring unit 12 monitors the amount of charge movement measured by the ammeter 20 and identifies the battery that has discharged that charge. The monitoring unit 12 uses a voltage measurement circuit to monitor the voltage value of each of the multiple batteries b1 to bn. The monitoring unit 12 also monitors the temperature of each of the multiple batteries b1 to bn.

[0040] The monitoring unit 12 outputs various information related to the acquired current, charge movement, voltage value, and temperature to the control unit 14.

[0041] The control unit 14 controls the transfer circuit based on various information output by the monitoring unit 12, thereby controlling and balancing the charge transfer among the multiple batteries b1 to bn. Furthermore, the charge transfer among the multiple batteries b1 to bn refers to transferring charge among the multiple batteries b1 to bn in a manner that causes an imbalance in the remaining capacity of each battery among the multiple batteries b1 to bn.

[0042] The control unit 14 controls the transfer circuit to control the charge transfer between the multiple batteries b1 to bn. Specifically, the control unit 14 controls... Figure 2 The switching on and off of the switches SWa~SWz shown is used to transfer charge from the battery with a high SOC (or high remaining capacity) to the battery with a low SOC (or low remaining capacity). The control unit 14 controls the switching on and off of the switches SWa~SWz to move charge from the high-voltage battery to the capacitor 18, and also controls the switching on and off of the switches SWa~SWz to move charge from the capacitor 18 to the low-voltage battery, thereby realizing the transfer of charge.

[0043] Furthermore, the control unit 14 determines the voltage difference ΔV between the multiple batteries b1 to bn. Additionally, when the voltage difference ΔV is greater than the equalization start voltage Vth set at a predetermined voltage value (e.g., 50mV), the control unit 14 begins equalization. Then, the control unit 14 controls the transfer circuit to charge batteries with high SOC (or high remaining capacity) to batteries with low SOC (or low remaining capacity). Specifically, the control unit 14 controls the switching of switches SWA to SWz to move charge from the high-SOC battery to the capacitor 18, and controls the switching of switches SWA to SWz to move charge from the capacitor 18 to the low-SOC battery, thereby achieving equalization. Furthermore, in this specification, the voltage difference ΔV between the multiple batteries b1 to bn refers to the voltage difference between any two batteries. When the voltage difference between any two batteries is greater than the equalization start voltage Vth, the control unit 14 begins equalization. Additionally, the current flowing through the transfer circuit during equalization is called the balancing current.

[0044] In addition, the control unit 14 controls the timing at which the monitoring unit 12 acquires various information (such as the current and voltage values ​​monitored by the monitoring unit 12).

[0045] Furthermore, the monitoring unit 12 and the control unit 14 are implemented using a microcomputer or processor, etc. That is, the functions of the monitoring unit 12 and the control unit 14 are implemented by executing programs stored in memory using a microcomputer or processor, etc.

[0046] [On Equilibrium]

[0047] use Figure 3 The above equilibrium will be explained. Figure 3 This is a graph showing the time-varying voltage of each of the multiple batteries b1~bn. Figure 3 In the graph shown, the vertical axis represents voltage (mV), and the horizontal axis represents the battery's discharge capacity (mAh), which is also the case in the subsequent attached graphs. Additionally, in Figure 3 The instructions specify the case where there are 5 batteries. Figure 3 (a) is a graph showing the time change of the control unit 14 from the start of supplying current from the five batteries b1 to b5 to the load 4 until the current supply is stopped. Figure 3 (b) is to be by Figure 3 The enlarged view of the area enclosed by the dotted line shown in (a). Furthermore, in Figure 3 The description provides specific examples of situations where the balancing current is not limited by the circuit structure, or where the degradation deviation of the five batteries b1~b5 is small. That is, in... Figure 3 The description provides a specific example where the difference between the current supplied from the five batteries b1 to b5 to the load 4 and the current involved in charging a battery with a high SOC to a battery with a low SOC is small.

[0048] exist Figure 3 In the graph shown in (a), the dashed line marked at 4200mV represents the battery voltage at full charge, and the dashed line marked at 2500mV represents the discharge termination voltage. Full charge refers to a state of charge where the battery's remaining capacity is 100%. The discharge termination voltage is the voltage at which at least one of the batteries b1~bn stops discharging, i.e., the voltage at which at least one battery's remaining capacity is 0%. Furthermore, the battery voltage at full charge and the discharge termination voltage are the same in the graphs shown in the subsequent figures.

[0049] like Figure 3 As shown in (a), starting from the control unit 14, the current is supplied from the five batteries b1 to b5 to the load 4. As time passes, the voltage of each of the five batteries b1 to b5 decreases.

[0050] exist Figure 3 In the graph shown in (b), periods (A), (C), and (E) are the periods during which the control unit 14 supplies current from the five batteries b1 to b5 to the load 4 without performing balancing. Periods (B) and (D) are the periods during which the control unit 14 performs balancing and supplies current from the five batteries b1 to b5 to the load 4.

[0051] like Figure 3 As shown in (b), during the period of (A), the voltage difference ΔV between the five batteries b1~b5 is less than the equalization start voltage Vth, so the control unit 14 supplies current from the five batteries b1~b5 to the load 4.

[0052] At the beginning of period (B), the voltage difference ΔV between the five batteries b1 to b5 is greater than the equalization start voltage Vth. Therefore, 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 batteries with high SOC and low SOC and begins charging from the high-SOC battery to the low-SOC battery. Then, the control unit 14 performs this charging until the SOC of the five batteries b1 to b5 is consistent, that is, equalization is achieved. In addition, during the equalization period, the control unit 14 acquires the voltage of each of the five batteries b1 to b5 measured by the voltage measurement circuit at predetermined intervals, re-identifies the batteries with high SOC and low SOC, and begins charging from the high-SOC battery to the low-SOC battery.

[0053] During (B), the difference between the current supplied from the five batteries b1 to b5 to the load 4 and the current supplied from the battery with high SOC to the battery with low SOC is small. Therefore, the battery pack balancing device 8 can complete the balancing before stopping the current supply from the five batteries b1 to b5 to the load 4.

[0054] During (C), the voltage difference ΔV between the five batteries b1~b5 is less than the equalization start voltage Vth. The control unit 14 supplies current from the five batteries b1~b5 to the load 4 in a manner that keeps the difference in discharge capacity between the five batteries b1~b5 constant.

[0055] At the beginning of period (D), the voltage difference ΔV between the five batteries b1~b5 is greater than the equalization start voltage Vth. Therefore, the control unit 14 performs equalization in the same way as in period (B) during period (D) and supplies current from the five batteries b1~b5 to the load 4.

[0056] During period (E), the voltage difference ΔV between the five batteries b1 to b5 is less 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 in the same manner as during period (C), maintaining the difference in discharge capacity between the five batteries b1 to b5 at a constant level. Furthermore, at the end of period (E), the voltage of each of the five batteries b1 to b5 reaches the discharge termination voltage (i.e., 2500mV).

[0057] As described above, when the balancing current is not limited by the circuit structure or when the deviation in the deterioration of the multiple batteries b1 to bn is small, the battery pack balancing device 8 can achieve the discharge termination voltage of each battery among the multiple batteries b1 to bn by performing balancing.

[0058] [Action Example]

[0059] Next, use Figure 4 The operation of the battery pack balancing device 8 according to this embodiment will be explained. Figure 4 It is shown Figure 1 The flowchart shows the operation of the battery pack balancing device 8.

[0060] First, the control unit 14 begins to supply current from multiple batteries b1 to bn to the load 4 (step S101).

[0061] 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 voltage of each battery among the multiple batteries b1~bn measured by the voltage measurement circuit, and determines whether the voltage difference ΔV is greater than the equalization start voltage Vth (step S102).

[0062] If the control unit 14 determines that the voltage difference ΔV is below the equalization start voltage Vth (in step S102, it is "No"), it continues to supply current from the multiple batteries b1 to bn to the load 4.

[0063] When the control unit 14 determines that the voltage difference ΔV is greater than the equalization start voltage Vth ("Yes" in step S102), it begins equalization to make the remaining capacity of each of the multiple batteries b1 to bn consistent (step S103). Furthermore, during the equalization process, the control unit 14 can either continue supplying current from the multiple batteries b1 to bn to the load 4 or stop supplying current based on a request from the load 4.

[0064] The control unit 14 determines that the voltage of at least one battery, as measured by the voltage measurement circuit, has reached the discharge termination voltage (step S104). After the determination in step S104, the control unit 14 stops the supply of current from the plurality of batteries b1 to bn to the load 4. Furthermore, the control unit 14 determines whether there are any batteries with residual charge (step S105).

[0065] If the control unit 14 determines that there are no batteries with residual charge ("No" in step S105), it uses the external power supply 6 to charge the multiple batteries b1 to bn (step S107).

[0066] If the control unit 14 determines that a battery with residual charge exists ("Yes" in step S105), it discharges the battery until the voltage of the battery that has not reached the discharge termination voltage reaches the discharge termination voltage, and measures the amount of charge discharged by the battery until the discharge termination voltage is reached (step S106). Specifically, the control unit 14 acquires the amount of charge movement measured by the ammeter 20, and acquires information for determining the battery that has discharged the charge.

[0067] Furthermore, in step S106, the control unit 14 determines the voltage and current of the batteries when charge transfer begins among the multiple batteries b1~bn, based on the amount of charge measured by the ammeter 20. Additionally, the control unit 14 determines the voltage and current such that charge transfer is completed before equalization begins.

[0068] After step S106, the control unit 14 uses the external power supply 6 to charge the multiple batteries b1 to bn (step S107). Alternatively, the control unit 14 may use the charge stored in step S106 to charge the multiple batteries b1 to bn. For example, when using the charge stored in step S106 to charge the multiple batteries b1 to bn, the control unit 14 may distribute the charge evenly among the batteries b1 to bn, or distribute the charge in a manner opposite to the magnitude of the charge measured in step S106.

[0069] The control unit 14 restarts the supply of current from the multiple batteries b1 to bn to the load 4 (step S108).

[0070] The control unit 14 controls the transfer circuit based on the charge amount measured in step S106 during a predetermined period, thereby transferring charge between the multiple batteries b1 to bn (step S109). Specifically, the control unit 14 starts the charge transfer between the multiple batteries b1 to bn based on the voltage and current determined according to the measured charge amount. Furthermore, the control unit 14 transfers charge between the multiple batteries b1 to bn in a manner opposite to the magnitude of the charge amount discharged (charge consumed) by each battery in step S106. The predetermined period refers to the period during which the voltage difference ΔV calculated by the control unit 14 is less than the equilibrium start voltage Vth. Alternatively, the predetermined period can also refer to the period from the start of discharge of the multiple batteries b1 to bn until a certain amount of charge is discharged, regardless of whether the voltage difference ΔV is greater than the equilibrium start voltage Vth.

[0071] Furthermore, in step S106, if multiple batteries have not reached the discharge termination voltage, the control unit 14 discharges each battery until the voltage reaches the discharge termination voltage, and measures the amount of charge discharged by each battery up to the discharge termination voltage. Additionally, the control unit 14 may store the discharged charge in the capacitor 18.

[0072] Furthermore, in step S107, the control unit 14 can either charge the batteries b1 to bn until the remaining capacity of each battery is 100% (i.e., fully charged), or charge them to a certain percentage. Additionally, to ensure that the remaining capacity of each battery b1 to bn is 100%, the control unit 14 can also perform equalization during the charging of the batteries b1 to bn.

[0073] in addition, Figure 4 In the example shown, step S103 corresponds to the balancing step performed by the control unit 14, step S106 corresponds to the measurement step performed by the control unit 14, and step S109 corresponds to the transmission step performed by the control unit 14.

[0074] According to the above description, before performing equalization, the battery pack equalization device 8 measures the imbalance state of the amount of charge consumed among multiple batteries b1~bn in the measurement step, and performs charge transfer based on the imbalance state.

[0075] Furthermore, before equalization, the battery pack equalization device 8 performs charge transfer among the multiple batteries b1 to bn to increase the remaining capacity of the worst-performing battery and decrease the remaining capacity of the least-performing battery. In other words, charge transfer among the multiple batteries b1 to bn before equalization eliminates the imbalance in charge consumption measured beforehand. Therefore, even when there is a large difference between the current supplied from the multiple batteries b1 to bn to the load 4 and the current involved in charging from the battery with a high SOC to the battery with a low SOC, the battery pack equalization device 8 can still achieve equalization.

[0076] In addition, the battery pack equalization device 8 starts the transfer of charge between multiple batteries b1 to bn based on the determined voltage and current of the battery, so that the charge transfer can be completed before the equalization begins.

[0077] In addition, the battery pack equalization device 8 completes the charge transfer during the period when the voltage difference ΔV between multiple batteries b1~bn is less than the equalization start voltage Vth, thus allowing time for equalization.

[0078] In addition, the battery equalization device 8 uses the charge discharged by the battery in the measurement step (S106) to charge the multiple batteries b1 to bn, thus reducing the amount of charge required to charge the multiple batteries b1 to bn supplied from the external power source 6.

[0079] Furthermore, when the battery pack balancing device 8 uses the charge stored in the measurement step (S106) during the charging of multiple batteries b1 to bn, it distributes the charge in a manner opposite to the magnitude of the charge measured in the measurement step (S106). Therefore, it can distribute more charge to batteries with smaller capacity (or those experiencing more degradation). Since smaller capacity batteries reach full charge earlier than larger capacity (or those with less degradation), the battery pack balancing device 8 can shorten the balancing time involved in charging by distributing more charge to smaller capacity batteries. Additionally, after the measurement step (S106), the battery pack balancing device 8 distributes more charge to smaller capacity batteries, maintaining their voltage at a higher level, thus reducing the rate of degradation of those batteries.

[0080] use Figure 5A and Figure 5B The specific examples shown illustrate that in Figure 4 The battery pack balancing device 8 described herein performs the following actions. Figure 5A and Figure 5B The description specifies a scenario where there are 5 batteries, and battery b3 is the least efficient among the 5 batteries (b1~b5). Furthermore, Figure 5A and Figure 5BThe specific examples shown are cases where the balancing current is limited by the circuit structure, or cases where the degradation deviation of the five batteries b1~b5 is large. That is, in... Figure 5A and Figure 5B The description provides a specific example of a situation where the difference between the amount of current supplied from the five batteries b1 to b5 to the load 4 and the amount of current involved in charging a battery with a high SOC to a battery with a low SOC is large.

[0081] Figure 5A It is shown that... Figure 3 The figure shows a specific example corresponding to steps S101 to S104. Figure 5A (a) is a graph showing the time variation of the voltage of each of the five batteries b1 to b5 when the control unit 14 does not perform charge transfer between the five batteries b1 to b5 during a specified period but performs equalization of the five batteries b1 to b5. Figure 5A (b) is shown in Figure 5A A schematic diagram showing the remaining capacity of each of the five batteries b1~b5 at the time point shown in (a). Furthermore, in Figure 5A In (b), the diagonal lines shown in each of the five batteries b1 to b5 are lines representing the remaining capacity of each of the five batteries b1 to b5.

[0082] like Figure 5A As shown in (a), at time (I), the control unit 14 begins supplying current from the five batteries b1~b5 to the load 4. This is in accordance with... Figure 4 The action corresponding to step S101.

[0083] At time point (II), the voltage difference ΔV between the five batteries b1~b5 is less than the equalization start voltage Vth, therefore control unit 14 continues to supply current from the five batteries b1~b5 to the load 4. This is in contrast to... Figure 4 In step S102, the control unit 14 performs the action corresponding to the "no" determination.

[0084] At time point (III), the voltage difference ΔV between the five batteries b1~b5 is greater than the equalization start voltage Vth, therefore control unit 14 begins equalization. This is related to... Figure 4 The action corresponding to step S103 (that is, the balancing step).

[0085] During 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 referred to as the normal discharge period.

[0086] At time point (IV), the voltage of at least one of the five batteries b1-b5 reaches the discharge termination voltage, therefore the control unit 14 stops the current supply from the five batteries b1-b5 to the load 4. This is related to... Figure 4 The action corresponding to step S104.

[0087] During (III) to (IV), control unit 14 performs... Figure 2 The process described above balances the current supply from the five batteries b1~b5 to the load 4. This period is called the balancing period.

[0088] like Figure 5A As shown in (b), in (I) to (IV), the remaining capacity of each of the five batteries b1 to b5 decreases. (As shown in...) Figure 5A As explained in (a), periods (I) to (III) are the normal discharge periods, during which no charge transfer occurs between the five batteries b1 to b5, therefore the least degraded battery b3 has the least remaining capacity. Periods (III) to (IV) are the balancing periods, during which the charging of batteries with high SOC is balanced to those with low SOC, and current is supplied from the five batteries b1 to b5 to the load 4. During periods (III) to (IV), the difference between the current supplied from the five batteries b1 to b5 to the load 4 and the current involved in charging from the high-SOC battery to the low-SOC battery is large, therefore the battery balancing device 8 cannot complete the balancing. Consequently, at time point (IV), the remaining capacity of the five batteries b1 to b5 will not simultaneously reach 0%.

[0089] Figure 5B It is shown that... Figure 4 A specific example of steps S102-S104 and steps S108-S109 is shown in the figure. Figure 5B It is shown in Figure 5A Then Control Unit 14 executes Figure 4 The diagram shows a specific example of step S106 (i.e., the measurement step) and restarting the supply of current from the five batteries b1~b5 to the load 4. Figure 5B (a) is a graph showing the time variation of the voltage of each of the five batteries b1 to b5 when the control unit 14 performs charge transfer between the five batteries b1 to b5 and balances the five batteries b1 to b5 during a specified period. Figure 5B (b) is shown in Figure 5B A schematic diagram showing the remaining capacity of each of the five batteries b1~b5 at the time point shown in (a). Furthermore, in Figure 5B In (b), the diagonal lines shown in each of the five batteries b1 to b5 are lines representing the remaining capacity of each of the five batteries b1 to b5.

[0090] like Figure 5B As shown in (a), at time (V), control unit 14 restarts the supply of current from the five batteries b1~b5 to load 4. This is in accordance with... Figure 4 The action corresponding to step S108.

[0091] At time point (VI), the voltage of any one of the five batteries b1 to b5 reaches the voltage of the battery at which charge transfer begins among the five batteries b1 to b5, therefore the control unit 14 initiates charge transfer among the five batteries b1 to b5. This is in contrast to... Figure 4 The action corresponding to step S109 (that is, the transmission step).

[0092] During (V) to (VI), the control unit 14 only supplies current from the five batteries b1 to b5 to the load 4 (during normal discharge).

[0093] At time point (VII), the voltage difference ΔV between the five batteries b1~b5 is greater than the equalization start voltage Vth, therefore control unit 14 begins equalization. This is related to... Figure 4 The action corresponding to step S103 (that is, the balancing step).

[0094] During periods (VI) to (VII), the control unit 14 performs charge transfer between the five batteries b1 to b5 and supplies current from the five batteries b1 to b5 to the load 4. This period is referred to as the pre-charge migration period.

[0095] At time point (VIII), the voltage of at least one of the five batteries b1-b5 reaches the discharge termination voltage, therefore control unit 14 stops the current supply from the five batteries b1-b5 to the load 4. This is in accordance with... Figure 4 The action corresponding to step S104.

[0096] During periods (VII) to (VIII), control unit 14 performs... Figure 2 The process is balanced, and current is supplied from the five batteries b1~b5 to the load 4 (during the balancing period).

[0097] like Figure 5B As shown in (b), the period from (V) to (VI) is the normal discharge period, therefore... Figure 5A Similarly, during periods (I) to (II) shown in (b), the remaining capacity of each of the five batteries b1 to b5 decreases. Furthermore, at time point (VI), similarly to time point (II), battery b3 has the lowest remaining capacity.

[0098] Furthermore, the periods (VI) to (VII) are the pre-charge migration period; therefore, at time point (VII), battery b3 has the highest remaining capacity, while batteries b1 and b5 have the lowest remaining capacity. This is because the control unit 14, in conjunction with... Figure 5A The remaining capacity of each of the five batteries b1 to b5 at time point (IV) shown in (b) was in the opposite order, and the charge transfer between the five batteries b1 to b5 was carried out.

[0099] The periods (VII) to (VIII) are equilibrium periods, and... Figure 5A Similarly, during periods (III) to (IV) shown in (b), charging balancing is performed from the battery with high SOC to the battery with low SOC, and current is supplied from the five batteries b1 to b5 to the load 4. The control unit 14 performs charge transfer during periods (VI) to (VII), thus enabling the battery pack balancing device 8 to complete balancing. Therefore, at time point (VIII), the remaining capacity of the five batteries b1 to b5 simultaneously becomes 0%.

[0100] Furthermore, the pre-charge migration period (i.e., the periods (VI) to (VII)) may not immediately precede the equilibrium period (i.e., the periods (VII) to (VIII)). For example, the timing may be configured such that the equilibrium period begins after the pre-charge migration period, followed by the normal discharge period.

[0101] [Effect]

[0102] Based on the above description, the battery pack balancing device 8 according to this embodiment is a battery pack balancing device 8 for balancing the remaining capacity of each battery in a plurality of series-connected batteries b1 to bn. The battery pack balancing device 8 includes: a transfer circuit for transferring charge among the plurality of batteries b1 to bn; a voltage measuring circuit for measuring the voltage of each battery in the plurality of batteries b1 to bn; an ammeter 20 for measuring the amount of charge movement in each battery in the plurality of batteries b1 to bn; and a control unit 14 for controlling the transfer circuit, wherein the control unit 14 executes: a measurement step (S106), in which the voltage of at least one battery measured by the voltage measuring circuit reaches the voltage at which the discharge of the plurality of batteries b1 to bn is stopped, i.e., discharge. The timing of the termination voltage is such that batteries that have not reached the discharge termination voltage are discharged until their voltage reaches the discharge termination voltage, and the amount of charge discharged by the batteries until the discharge termination voltage is reached is measured; in the transfer step (S109), after supplying current from the multiple charged batteries b1~bn to the load 4, the transfer circuit is controlled based on the amount of charge measured in the measurement step (S106) for a predetermined period of time, thereby transferring charge between the multiple batteries b1~bn; and in the equalization step (S103), after the transfer step (S109), equalization is started when the voltage difference ΔV between the multiple batteries b1~bn is greater than the equalization start voltage Vth set by a predetermined voltage value.

[0103] Before balancing, this battery pack balancing device 8 measures the imbalance of charge consumption among multiple batteries b1 to bn in a measurement step, and performs charge transfer based on this imbalance. Therefore, even if the balancing current is limited by the circuit or if the degradation deviation among the multiple batteries b1 to bn is large, the battery pack balancing device 8 can ensure that the state of charge (SOC) of the multiple batteries b1 to bn is the same.

[0104] Furthermore, in the battery pack balancing device 8 according to this embodiment, the control unit 14 transfers charge between multiple batteries b1 to bn in the transfer step (S109) in a manner opposite to the magnitude of the charge discharged by each battery in the measurement step (S106).

[0105] Before equalization, this battery pack equalization device 8 performs charge transfer among multiple batteries b1 to bn to increase the remaining capacity of the worst-performing battery and decrease the remaining capacity of the least-performing battery. In other words, by transferring charge among multiple batteries b1 to bn before equalization, it eliminates the imbalance in charge consumption measured beforehand. Therefore, even when there is a large difference between the current supplied from multiple batteries b1 to bn to the load 4 and the current involved in charging from a battery with a high SOC to a battery with a low SOC, the battery pack equalization device 8 can still achieve equalization.

[0106] Furthermore, in the battery pack balancing device 8 according to this embodiment, the specified period is the period during which the voltage difference ΔV between the multiple batteries b1 to bn is smaller than the balancing start voltage Vth.

[0107] Such a battery pack balancing device 8 completes the charge transfer during the period when the voltage difference ΔV between multiple batteries b1~bn is less than the balancing start voltage Vth, thus allowing time for balancing.

[0108] Furthermore, in the battery pack balancing device 8 according to this embodiment, the control unit 14 determines the voltage and current of the battery when the transfer of charge between multiple batteries b1 to bn begins in the transfer step (S109) based on the amount of charge measured in the measurement step (S106).

[0109] This battery pack balancing device 8 starts the transfer of charge between multiple batteries b1~bn based on the determined voltage and current of the batteries, thus enabling the transfer of charge to be completed before balancing begins.

[0110] In addition, in the battery pack balancing device 8 according to this embodiment, the control unit 14 also stores the charge discharged by the battery in the measurement step (S106), and uses the stored charge when charging multiple batteries b1 to bn.

[0111] Such a battery pack equalization device 8 uses the charge discharged by the battery in the measurement step (S106) to charge multiple batteries b1~bn, thus reducing the amount of charge required to charge multiple batteries b1~bn supplied from the external power source 6.

[0112] Furthermore, in the battery pack equalization device 8 according to this embodiment, when the control unit uses the charge stored in the measurement step (S106) during the charging of multiple batteries, it distributes the charge in a manner opposite to the magnitude of the charge measured in the measurement step (S106).

[0113] When charging multiple batteries b1 to bn, this battery equalization device 8 uses the charge stored in the measurement step (S106) to distribute the charge in a manner opposite to the magnitude of the charge measured in the measurement step (S106). Therefore, it can distribute more charge to batteries with smaller capacity (or those experiencing more degradation). Since smaller capacity batteries reach full charge earlier than larger capacity (or less deteriorated) batteries, the battery equalization device 8 can shorten the equalization time during charging by distributing more charge to smaller capacity batteries. Furthermore, after the measurement step (S106), the battery equalization device 8 distributes more charge to smaller capacity batteries, maintaining their voltage at a higher level, thus reducing the rate of degradation of those batteries.

[0114] Furthermore, the battery pack balancing method involved in this embodiment is performed by a battery pack balancing device 8. The battery pack balancing device 8 performs balancing to ensure that the remaining capacity of each battery in a series-connected plurality of batteries b1 to bn is consistent. The battery pack balancing device 8 includes: a transfer circuit for transferring charge between the plurality of batteries b1 to bn; a voltage measurement circuit for measuring the voltage of each battery in the plurality of batteries b1 to bn; and an ammeter 20 for measuring the amount of charge movement in each battery in the plurality of batteries b1 to bn. The battery pack balancing method includes a measurement step (S106), where the voltage of at least one battery measured by the voltage measurement circuit reaches the voltage at which the discharge of the plurality of batteries b1 to bn is stopped, i.e., discharge is terminated. The voltage timing point is used to discharge the batteries that have not reached the discharge termination voltage until the voltage of the batteries that have not reached the discharge termination voltage reaches the discharge termination voltage, and the amount of charge discharged by the batteries until the discharge termination voltage is reached is measured; in the transfer step (S109), after supplying current from the multiple charged batteries b1~bn to the load 4, the transfer circuit is controlled based on the amount of charge measured in the measurement step (S106) for a specified period, thereby transferring the charge between the multiple batteries b1~bn; and in the equalization step (S103), after the transfer step (S109), equalization is started when the voltage difference ΔV between the multiple batteries b1~bn is greater than the equalization start voltage Vth set by a specified voltage value.

[0115] In this battery pack balancing method, before balancing, the imbalance of charge consumption among multiple batteries b1~bn is measured in a measurement step, and charge transfer is performed based on this imbalance. Therefore, even when the balancing current is limited by the circuit or when the degradation deviation among the multiple batteries b1~bn is large, this battery pack balancing method can ensure that the state of charge (SOC) of the multiple batteries b1~bn is the same.

[0116] Furthermore, the program involved in this embodiment causes the computer to execute the battery pack balancing method described above.

[0117] This procedure achieves the same effect as the battery pack balancing method described above.

[0118] [Variation Example]

[0119] The battery pack balancing device and the like disclosed herein have been described above based on the aforementioned embodiments, but this disclosure is not limited to the above embodiments. As long as they do not depart from the spirit of this disclosure, various modifications to the above embodiments that can be conceived by those skilled in the art, and ways of constructing by combining structural elements from different embodiments, may also be included within the scope of one or more of these methods.

[0120] Furthermore, in the above embodiments, each structural element can also be constructed using dedicated hardware, or implemented by executing software programs suitable for each structural element. Each structural element can also be implemented by a program execution unit such as a CPU or processor reading and executing software programs recorded on a recording medium such as a hard disk or semiconductor memory.

[0121] In addition, in the above embodiments, the functions of each structural element can also be partially or fully realized by executing programs through a processor such as a CPU.

[0122] Some or all of the structural elements constituting the aforementioned devices may also be configured as modules consisting of detachable IC cards or individual units relative to each device. The aforementioned IC card or module is a computer system composed of a microprocessor, ROM, RAM, etc. The aforementioned IC card or module may also include a multi-function LSI. The microprocessor operates according to a computer program, thereby enabling the aforementioned IC card or module to perform its functions. The IC card or module may also be designed to be tamper-proof.

[0123] [Postscript]

[0124] Based on the above description of the embodiments, the following technology is disclosed.

[0125] (Technology 1) A battery pack balancing device for balancing the remaining capacity of each battery in a series-connected plurality of batteries, the battery pack balancing device comprising: a transfer circuit for transferring charge among the plurality of batteries; a voltage measuring circuit for measuring the voltage of each battery in the plurality of batteries; a galvanometer for measuring the amount of charge movement in each battery in the plurality of batteries; and a control unit for controlling the transfer circuit, wherein the control unit executes: a measurement step, at a time point when the voltage of at least one battery measured by the voltage measuring circuit reaches the voltage at which the discharge of the plurality of batteries is stopped, i.e., the discharge termination voltage, to prevent the discharge of the plurality of batteries from reaching the discharge termination voltage. The battery discharges until the voltage of the battery that has not yet reached the discharge termination voltage reaches the discharge termination voltage, and the amount of charge discharged by the battery up to reaching the discharge termination voltage is measured; a transfer step, after supplying current from the charged plurality of batteries to the load, controls the transfer circuit based on the amount of charge measured in the measurement step for a predetermined period, thereby transferring charge among the plurality of batteries; and an equalization step, after the transfer step, when the voltage difference among the plurality of batteries is greater than an equalization start voltage set at a predetermined voltage value, the equalization is initiated.

[0126] (Technology 2) The battery pack balancing device according to Technology 1, wherein the control unit, in the transfer step, performs charge transfer among the plurality of batteries in a manner opposite to the magnitude of the charge discharged by each of the batteries in the measurement step.

[0127] (Technology 3) The battery pack balancing device according to Technology 1 or 2, wherein the specified period is a period in which the voltage difference between the plurality of batteries is smaller than the balancing start voltage.

[0128] (Technology 4) A battery pack equalization device according to any one of technologies 1 to 3, wherein the control unit determines the voltage and current of the battery 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.

[0129] (Technology 5) A battery pack balancing device according to any one of technologies 1 to 4, wherein the control unit further stores the charge discharged by the battery in the measurement step, and uses the stored charge when the plurality of batteries are charged.

[0130] (Technology 6) The battery pack equalization device according to Technology 5, wherein, when the control unit uses the charge stored in the measurement step during the charging of the plurality of batteries, the charge is distributed in a manner opposite to the magnitude of the charge measured in the measurement step.

[0131] (Technology 7) A battery pack balancing method, performed by a battery pack balancing device, the battery pack balancing device balancing the remaining capacity of each battery in a series-connected plurality of batteries to be consistent, wherein the battery pack balancing device comprises: a transfer circuit for transferring charge among the plurality of batteries; a voltage measuring circuit for measuring the voltage of each battery in the plurality of batteries; and an ammeter for measuring the amount of charge movement in each battery in the plurality of batteries, the battery pack balancing method comprising: a measurement step, when the voltage of at least one battery measured by the voltage measuring circuit reaches a voltage that stops the discharge of the plurality of batteries, i.e., a discharge termination voltage. The process involves: a discharge point, in which the batteries that have not reached the discharge termination voltage are discharged until their voltage reaches the discharge termination voltage, and the amount of charge discharged by the batteries up to reaching the discharge termination voltage is measured; a transfer step, in which, after supplying current from the charged batteries to the load, the transfer circuit is controlled within a predetermined period based on the amount of charge measured in the measurement step, thereby transferring charge among the batteries; and an equalization step, in which, after the transfer step, equalization is initiated when the voltage difference among the batteries is greater than an equalization start voltage set at a predetermined voltage value.

[0132] (Technology 8) A program for causing a computer to perform the battery pack balancing method according to Technology 7.

[0133] Industrial availability

[0134] The battery pack balancing device disclosed herein is useful, for example, as a means of making the remaining capacity of each battery in a series-connected plurality of batteries consistent.

[0135] Explanation of reference numerals in the attached figures

[0136] 2 Battery Packs

[0137] 4. Load

[0138] 6. External power supply

[0139] 8. Battery pack balancing device

[0140] 10 Single-cell battery balancing circuit

[0141] 12. Surveillance Department

[0142] 14 Control Department

[0143] 16 DC / DC converter

[0144] 18 Capacitors

[0145] 20 Ammeter

[0146] Multiple batteries from b1 to bn

[0147] Multiple voltmeters V1~Vn

[0148] SWa~SWz Toggle switch.

Claims

1. A battery pack balancing device for balancing the remaining capacity of each battery in a series-connected plurality of batteries, the battery pack balancing device comprising: A charge transfer circuit that performs charge transfer among the plurality of batteries; A voltage measuring circuit that measures the voltage of each of the plurality of batteries; A galvanometer that measures the amount of charge movement in each of the plurality of batteries; as well as The control unit controls the transmission circuit. The control unit performs the following: The measurement step involves the voltage of at least one of the batteries measured by the voltage measurement circuit reaching the discharge termination voltage, i.e., the voltage at which the discharge of the plurality of batteries is stopped. The batteries that have not reached the discharge termination voltage are then discharged until their voltages reach the discharge termination voltage. The amount of charge discharged by the batteries up to the point where the discharge termination voltage is reached is then measured. The transfer step involves, after supplying current from the charged plurality of batteries to the load, controlling the transfer circuit based on the amount of charge measured in the measurement step within a predetermined period, thereby performing charge transfer between the plurality of batteries; and The balancing step is initiated after the transfer step, when the voltage difference between the plurality of batteries is greater than a balancing start voltage set with a predetermined voltage value.

2. The battery pack balancing device according to claim 1, wherein, In the transfer step, the control unit transfers charge between the plurality of batteries in a manner opposite to the magnitude of the charge discharged by each of the batteries in the measurement step.

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

4. The battery pack balancing device according to claim 1, wherein, The control unit determines the voltage and current of the battery when the charge transfer 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 balancing device according to claim 1, wherein, The control unit also stores the charge discharged by the battery during the measurement step, and uses the stored charge when the plurality of batteries are being charged.

6. The battery pack balancing device according to claim 5, wherein, When the control unit uses the charge stored in the measurement step during the charging of the plurality of batteries, it distributes the charge in a manner opposite to the magnitude of the charge measured in the measurement step.

7. A battery pack balancing method, performed by a battery pack balancing device, wherein the battery pack balancing device performs balancing to ensure that the remaining capacity of each battery in a series-connected plurality of batteries is consistent, wherein... The battery pack balancing device includes: A charge transfer circuit that performs charge transfer among the plurality of batteries; A voltage measuring circuit that measures the voltage of each of the plurality of batteries; as well as A galvanometer that measures the amount of charge movement in each of the plurality of batteries. The battery pack balancing method includes: The measurement step involves the voltage of at least one of the batteries measured by the voltage measurement circuit reaching the discharge termination voltage, i.e., the voltage at which the discharge of the plurality of batteries is stopped. The batteries that have not reached the discharge termination voltage are then discharged until their voltages reach the discharge termination voltage. The amount of charge discharged by the batteries up to the point where the discharge termination voltage is reached is then measured. The transfer step involves, after supplying current from the charged plurality of batteries to the load, controlling the transfer circuit based on the amount of charge measured in the measurement step within a predetermined period, thereby performing charge transfer between the plurality of batteries; and The balancing step is initiated after the transfer step, when the voltage difference between the plurality of batteries is greater than a balancing start voltage set with a predetermined voltage value.

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

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