Rechargeable battery system

Abstract

A rechargeable battery system is provided with: a plurality of battery packs including rechargeable batteries that can be charged and discharged; a plurality of power control units configured to correspondingly set and adjust voltages applied from the corresponding rechargeable batteries one by one for the plurality of battery packs; and an output terminal configured to be applied with the voltage adjusted by the plurality of power control units. The rechargeable battery system is further provided with: a step-down device configured to step down a voltage applied from the rechargeable battery to a voltage lower than a voltage output from the output terminal; an auxiliary battery configured to be applied with a voltage reduced by the step-down device; and an auxiliary device configured to be driven by the auxiliary battery.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a rechargeable battery system. BACKGROUND

[0002] A rechargeable battery system is described in Japanese Patent Application Publication No. 2022-080835. The rechargeable battery system includes a rechargeable battery, a power control unit, and an output terminal. The power control unit adjusts a voltage applied from the rechargeable battery. The voltage from the power control unit is output in the output terminal. SUMMARY

[0003] PROBLEMS TO BE SOLVED BY THE INVENTION In the rechargeable battery system described in the above publication, an auxiliary device that is driven by a low voltage lower than the voltage output from the output terminal is sometimes provided. In this case, a power source that outputs the low voltage for driving the auxiliary device is needed. However, in the case where the low voltage is supplied from the outside of the rechargeable battery system, another power source is also needed.

[0004] MEANS FOR SOLVING THE PROBLEMS A rechargeable battery system according to one embodiment of the present disclosure includes a plurality of battery groups including rechargeable batteries that can be charged and discharged, a plurality of power control units configured to be provided corresponding to the plurality of battery groups one by one and to adjust a voltage applied from the corresponding rechargeable battery, and an output terminal configured to be applied with the voltage adjusted by the plurality of power control units. The rechargeable battery system also includes a step-down device configured to step down the voltage applied from the rechargeable battery to a voltage lower than the voltage output from the output terminal, an auxiliary battery configured to be applied with the voltage stepped down by the step-down device, and an auxiliary device configured to be driven by the auxiliary battery. BRIEF DESCRIPTION OF DRAWINGS

[0005] Figure 1 is a schematic view of a rechargeable battery system according to an embodiment.

[0006] Figure 2 is a flowchart of a series of processes performed by a control device according to the embodiment shown in Figure 1

[0007] Figure 3 is a flowchart of another series of processes performed by a control device according to the embodiment shown in Figure 1

[0008] Figure 4 is a schematic view of a rechargeable battery system according to a modification. DETAILED DESCRIPTION

[0009] Hereinafter, an embodiment of a rechargeable battery system 10 will be described with reference to the drawings.​​

[0010] <Summary of rechargeable battery system> A rechargeable battery system 10 is a system including a large stationary rechargeable battery for providing electric power of around 1000 kW, for example. The rechargeable battery system 10 is provided with a plurality of battery groups 20, a plurality of first connection wirings 25, a plurality of second connection wirings 26, a plurality of power control units 30, a plurality of first output wirings 35, and an output terminal 40.

[0011] The battery group 20 includes a rechargeable battery 21 capable of charge and discharge. The rechargeable battery 21 is, for example, a lithium ion secondary battery. The first connection wiring 25 and the second connection wiring 26 are connected to the upstream end in the battery group 20. The rechargeable battery 21 applies a voltage to the first connection wiring 25. The voltage applied from the rechargeable battery 21 to the first connection wiring 25 is, for example, direct current 400 V. In the present embodiment, the rechargeable battery 21 is a battery that can be used as a vehicle-mounted rechargeable battery mounted on one vehicle.

[0012] The battery group 20 includes a battery state monitoring device 22 and a cut-off relay 23. The battery state monitoring device 22 monitors the state of the rechargeable battery 21. The cut-off relay 23 is configured to be able to cut off discharge from the rechargeable battery 21. The cut-off relay 23 is controlled by the battery state monitoring device 22, whereby the operation and the rest of the discharge from the rechargeable battery 21 can be switched.

[0013] The power control unit 30 adjusts the voltage applied from the rechargeable battery 21. The power control unit 30 is connected to the downstream end of the first connection wiring 25. In the present embodiment, the power control unit 30 is denoted as PCU. Figure 1

[0014] The power control unit 30 receives the voltage applied from the rechargeable battery 21 as an input voltage via the first connection wiring 25. The power control unit 30 adjusts the input voltage to a predetermined prescribed voltage. The prescribed voltage is, for example, 200 V. The power control unit 30 converts the current from direct current to alternating current. The power control unit 30 is connected to the upstream end of the first output wiring 35. The power control unit 30 applies the adjusted prescribed voltage to the first output wiring 35.

[0015] The plurality of power control units 30 adjust the respective input voltages applied thereto to prescribed voltages. The plurality of power control units 30 apply the adjusted prescribed voltages to the corresponding first output wirings 35, respectively. The downstream ends of the plurality of first output wirings 35 are connected to the output terminal 40.

[0016] ​One power control unit 30 is connected with one battery group 20 via the first connection wiring 25. That is, one power control unit 30 is provided for one battery group 20. Therefore, the number of battery groups 20 is the same as the number of power control units 30.

[0017] The regulated voltage adjusted by the plurality of power control units 30 is applied to the output terminal 40. That is, the regulated voltage adjusted by the plurality of power control units 30 is applied to the output terminal 40. In the present embodiment, the voltage of 200 V AC is applied to the output terminal 40. The output terminal 40 outputs the regulated voltage to a machine or the like connected with the output terminal 40.

[0018] The rechargeable battery system 10 is provided with the plurality of step-down devices 50, the plurality of second output wirings 55, the auxiliary battery 60, the plurality of auxiliary devices 70, the control device 80, and various sensors 90 for acquiring the load parameter LP.

[0019] The step-down device 50 is connected with the downstream end of the second connection wiring 26. The step-down device 50 steps down the voltage applied from the rechargeable battery 21 via the second connection wiring 26 to a voltage lower than the voltage output from the output terminal 40. For example, the step-down device 50 steps down the applied voltage to 12 V.

[0020] The step-down device 50 includes a DCDC converter 51 and a switch 52. The switch 52 switches between a state in which the DCDC converter 51 is operating and a state in which the DCDC converter 51 is at rest. In the state in which the DCDC converter 51 is operating, charging of the auxiliary battery 60 by the step-down device 50 is performed. In the state in which the DCDC converter 51 is at rest, charging of the auxiliary battery 60 by the step-down device 50 is stopped. The operation of the switch 52 is performed, and thus the switching between the operation and the rest of the DCDC converter 51 can be performed. In the present embodiment, the switch 52 is denoted as SW. Figure 1

[0021] The DCDC converter 51 is connected with the upstream end of the second output wiring 55. The DCDC converter 51 applies the stepped-down voltage obtained by stepping down the voltage applied from the rechargeable battery 21 to the second output wiring 55. In the present embodiment, the DCDC converter 51 is denoted as DCDC. Figure 1

[0022] The plurality of step-down devices 50 respectively step down the applied voltage. The plurality of step-down devices 50 respectively apply the stepped-down voltage obtained by stepping down the applied voltage to the corresponding second output wiring 55. The downstream ends of the plurality of second output wirings 55 are connected with the auxiliary battery 60.

[0023] ​​Thus, a step-down device 50 is connected to a battery pack 20 via a second connection wiring 26. That is, one step-down device 50 is provided for one battery pack 20. Therefore, the number of step-down devices 50 is the same as the number of battery packs 20. Thus, the number of step-down devices 50 is the same as the number of power control units 30.

[0024] An auxiliary battery 60 is connected to the downstream ends of the plurality of second output wirings 55. A step-down voltage is applied from the plurality of step-down devices 50 to the auxiliary battery 60 via the plurality of second output wirings 55. The auxiliary battery 60 is, for example, a lead storage battery.

[0025] An auxiliary device 70 is connected to the second output wiring 55. The auxiliary device 70 is connected to the auxiliary battery 60 via a wiring. Therefore, the auxiliary device 70 is driven by a voltage applied to the second output wiring 55 or a voltage output from the auxiliary battery 60. By omitting the illustrated switching relay, the power supply to the auxiliary device 70 is switched to one of the second output wiring 55 and the auxiliary battery 60.

[0026] The auxiliary device 70 is driven by a low voltage of 12 V output from the auxiliary battery 60. The auxiliary device 70 includes, for example, a control circuit of the power control unit 30, a cooling device of the rechargeable battery system 10, and a circuit that manages the entire rechargeable battery system 10. In the present embodiment, one of the plurality of auxiliary devices 70 is a control device 80. That is, the control device 80 is driven by a power supply from the auxiliary battery 60.

[0027] The control device 80 controls the plurality of step-down devices 50. As described later, the control device 80 performs partial charging control that causes a part of the plurality of step-down devices 50 to operate and charges the auxiliary battery 60.

[0028] Various sensors 90 acquire load currents LA output from the respective step-down devices 50. The control device 80 acquires the load currents LA output from the respective step-down devices 50 acquired by the sensors 90. The sensors 90 are current sensors.

[0029] The control device 80 acquires, as a load parameter LP indicating a load L of each step-down device 50, a continuous operation time of each step-down device 50 based on the load current LA acquired from the sensor 90. Thus, the control device 80 acquires the load parameter LP of each step-down device 50.

[0030] The control device 80 calculates, as a charging parameter CP, a total value of the load currents LA output from the respective step-down devices 50 acquired from the sensors 90. The charging parameter CP is a parameter related to a charging amount to the auxiliary battery 60 per unit time. In the present embodiment, the charging parameter CP is a charging amount to the auxiliary battery 60 per unit time. Thus, the control device 80 acquires the charging parameter CP.

[0031] The control device 80 uses the acquired load parameters LP and charging parameters CP to select the step-down device 50 that operates to charge the auxiliary battery 60.

[0032] The control device 80 includes a CPU (execution device) 81, peripheral circuitry 82, RAM 83, storage device 84, and a bus 85. The bus 85 connects the execution device 81, peripheral circuitry 82, RAM 83, and storage device 84 in a communicative manner.

[0033] The execution device 81 performs information processing by executing various programs stored in the storage device 84. The peripheral circuitry 82 includes circuits for generating clock signals that define internal operations, power supply circuits, reset circuits, etc. The RAM 83 stores data generated in conjunction with the operation of the execution device 81. The storage device 84 stores a first charging program P1 and a second charging program P2 executed by the execution device 81 and related to the charging of the auxiliary battery 60 via the buck converter 50. The first charging program P1 is a program for switching between operating buck converters 50. The second charging program P2 is a program for increasing or decreasing the number of operating buck converters 50, targeting the auxiliary battery 60 being charged.

[0034] The actuator 81 performs partial charging control, charging the auxiliary battery 60 only through a portion of the multiple step-down devices 50. Specifically, when the rechargeable battery system 10 starts operating, the actuator 81 begins charging the auxiliary battery 60 through a predetermined step-down device 50 among the multiple step-down devices 50.

[0035] <Switching of step-down device 50> When charging of the auxiliary battery 60 via the step-down device 50 begins, the execution device 81 begins to execute the first charging program P1 with respect to the step-down device 50.

[0036] like Figure 2 As shown, when the execution device 81 begins the execution of the first charging procedure P1, the execution device 81 first performs the process of step S11. In step S11, the execution device 81 determines whether the rechargeable battery system 10 has stopped operating. When the rechargeable battery system 10 has stopped operating (S11: Yes), the execution device 81 stops charging the auxiliary battery 60 through the step-down device 50, and ends the current series of processes.

[0037] On the other hand, when the chargeable battery system 10 is not stopped (S11: No), the execution device 81 advances the process to step S12. In step S12, the execution device 81 acquires the load parameter LP of the subject step-down device 50. Thereafter, the execution device 81 advances the process to step S13.

[0038] In step S13, the execution device 81 determines whether the load L indicated by the acquired load parameter LP is greater than a predetermined prescribed load RL. The prescribed load RL is set in advance by a test or simulation as a load for which the continuous operation time of the step-down device 50 does not excessively heat. In the present embodiment, the execution device 81 determines whether the acquired load parameter LP, i.e., the continuous operation time, is longer than the time set as the prescribed load RL. When the load L indicated by the load parameter LP is equal to or less than the prescribed load RL (S13: No), the execution device 81 returns the process to step S11.

[0039] On the other hand, when the load L indicated by the load parameter LP is greater than the prescribed load RL (S13: Yes), the execution device 81 advances the process to step S14. In step S14, the execution device 81 stops the operation of the subject step-down device 50. Thereafter, the execution device 81 advances the process to step S15.

[0040] In step S15, the execution device 81 starts the operation of a step-down device 50 different from the step-down device 50 stopped in step S14. The other step-down device 50 that starts the operation in step S15 is determined in a predetermined order.

[0041] For example, an identification number is assigned to each of the plurality of step-down devices 50. The execution device 81 causes the step-down device 50 of the next identification number to the identification number of the step-down device 50 stopped in step S14 to be the other step-down device 50, and causes it to start the operation in the process of step S15. Thereafter, the execution device 81 ends the series of processes this time.

[0042] By performing the process of step S15, the execution device 81 starts the execution of the first charging program PI with the other step-down device 50 that started the operation as the subject. Thereby, the execution device 81 performs the processes of steps S11 to S15 on the other step-down device 50.

[0043] Thus, the execution device 81 switches the step-down device 50 that is the operation subject on the basis of the load parameter LP of the step-down device 50 that is operating. In particular, in the present embodiment, the execution device 81 switches the step-down device 50 that is the operation subject sequentially. That is, the execution device 81 charges the auxiliary battery 60 by causing a part of the plurality of step-down devices 50 to take turns in the operation.

[0044] <Increase or decrease in the number of step-down devices 50> When the auxiliary battery 60 is charged through the step-down device 50, the execution device 81 begins the execution of the second charging procedure P2.

[0045] like Figure 3 As shown, when the execution device 81 begins the execution of the second charging procedure P2, the execution device 81 first performs the process of step S21. In step S21, the execution device 81 determines whether the rechargeable battery system 10 has stopped operating. When the rechargeable battery system 10 has stopped operating (S21: Yes), the execution device 81 stops charging the auxiliary battery 60 through the step-down device 50, and ends the current series of processes.

[0046] On the other hand, when the rechargeable battery system 10 is not operating (S21: No), the execution device 81 causes the process to proceed to step S22. In step S22, the execution device 81 acquires the charging parameters CP of the auxiliary battery 60. Afterward, the execution device 81 causes the process to proceed to step S23.

[0047] In step S23, the execution device 81 determines whether the charging parameter CP is less than a predetermined lower limit value L1. The lower limit value L1 is the minimum amount of charge required per unit time when charging the auxiliary battery 60. The lower limit value L1 is determined in advance through experiments or simulations as the minimum amount of charge required per unit time when charging the auxiliary battery 60.

[0048] When the charging parameter CP is less than the lower limit value L1 (S23: Yes), the execution device 81 causes the process to proceed to step S24. In step S24, the execution device 81 increments the number of operating step-down devices 50 by 1. That is, the execution device 81 adds one of the idle step-down devices 50 to the list of operating step-down devices 50.

[0049] Specifically, the execution device 81 selects one of the stepped-down voltage devices 50 that is in the rest as the stepped-down voltage device 50 to be added. For example, the execution device 81 selects the stepped-down voltage device 50 to which the identification number larger than the identification number of the stepped-down voltage device 50 that is in operation by a predetermined value is assigned among the plurality of stepped-down voltage devices 50. If the selected stepped-down voltage device 50 is in the rest, the execution device 81 selects the selected stepped-down voltage device 50 as the stepped-down voltage device 50 to be added. On the other hand, if the selected stepped-down voltage device 50 is in operation, the execution device 81 selects the stepped-down voltage device 50 of the next identification number of the selected stepped-down voltage device 50 again. By repeating the above steps, the execution device 81 selects the stepped-down voltage device 50 in the rest as the stepped-down voltage device 50 to be added. If all of the stepped-down voltage devices 50 are in operation, the execution device 81 directly advances the process. Thereafter, the execution device 81 returns the process to step S21.

[0050] In step S23, when the charge parameter CP is equal to or larger than the lower limit value LI (S23: No), the execution device 81 advances the process to step S25. In step S25, the execution device 81 determines whether the charge parameter CP is equal to or larger than the upper limit value L2. The upper limit value L2 is the excessive charge amount per unit time when the auxiliary battery 60 is charged. The upper limit value L2 is determined in advance as the excessive charge amount per unit time when the auxiliary battery 60 is charged through experiments or simulations.

[0051] When the charge parameter CP is smaller than the upper limit value L2 (S25: No), the execution device 81 returns the process to step S21. On the other hand, when the charge parameter CP is equal to or larger than the upper limit value L2 (S25: Yes), the execution device 81 advances the process to step S26.

[0052] In step S26, the execution device 81 decreases the number of the stepped-down voltage devices 50 in operation by 1. That is, the execution device 81 rests one of the stepped-down voltage devices 50 in operation. Thereby, the execution device 81 stops the charging of the auxiliary battery 60 by the stepped-down voltage device 50.

[0053] The execution device 81 selects the stepped-down voltage device 50 to be rested on the basis of the load parameter LP. Specifically, the execution device 81 selects one of the stepped-down voltage devices 50 in operation as the stepped-down voltage device 50 to be rested. For example, the execution device 81 selects the stepped-down voltage device 50 in operation in which the load parameter LP is the largest as the stepped-down voltage device 50 to be rested. Thereafter, the execution device 81 returns the process to step S21.

[0054] Thus, during the operation of the rechargeable battery system 10, the execution device 81 increases or decreases the number of the step-down devices 50 that are in operation, based on the charge parameter CP of the auxiliary battery 60. When the operation of the rechargeable battery system 10 is stopped (S21: YES), the execution device 81 ends the series of processes.

[0055] <Effects of the Present Embodiment> The rechargeable battery system 10 includes the step-down devices 50, the auxiliary battery 60, and the auxiliary device 70. The step-down devices 50 step down the voltage applied from the rechargeable battery 21 to a voltage lower than the voltage output from the output terminal 40. The voltage stepped down by the step-down devices 50 is applied to the auxiliary battery 60. The auxiliary device 70 is driven by the electric power supplied from the auxiliary battery 60.

[0056] <Effects of the Present Embodiment> (1) The rechargeable battery system 10 steps down the voltage applied from the rechargeable battery 21 by the step-down devices 50, and thus can apply a low voltage for driving the auxiliary device 70 to the auxiliary battery 60. Therefore, the rechargeable battery system 10 does not need to provide another power source for driving the auxiliary device 70.

[0057] (2) The number of the step-down devices 50 is the same as the number of the power control units 30. That is, in the rechargeable battery system 10, the step-down devices 50 are provided corresponding to all the battery groups 20, respectively. Therefore, a low voltage can be supplied from the rechargeable battery 21 of all the battery groups 20 to the auxiliary battery 60, respectively.

[0058] (3) The rechargeable battery system 10 includes the plurality of step-down devices 50 and the control device 80 that controls the plurality of step-down devices 50. The control device 80 performs partial charge control of charging the auxiliary battery 60 by only a part of the plurality of step-down devices 50. The rechargeable battery system 10 can suspend the operation of the step-down devices 50 that are not used for charging the auxiliary battery 60 among the plurality of step-down devices 50, while charging the auxiliary battery 60, by the partial charge control. Therefore, the rechargeable battery system 10 can suppress the deterioration of the step-down devices 50 caused by the long-time operation of the same step-down devices 50, by avoiding the case where the same step-down devices 50 are always in operation in association with the charging of the auxiliary battery 60.

[0059] (4) The control device 80 acquires the load parameter LP of each of the step-down devices 50. The control device 80 switches the step-down device 50 used for the partial charging control on the basis of the acquired load parameter LP. Thus, the chargeable battery system 10 performs the partial charging control by the step-down device 50 different from the step-down device 50 with a large load parameter LP. As a result, it is possible to suspend the step-down device 50 before the load L of the step-down device 50 in operation becomes excessively large, and it is possible to continue the charging of the auxiliary battery 60.

[0060] (5) The chargeable battery system 10 increases or decreases the number of the step-down devices 50 that charge the auxiliary battery 60 on the basis of the charging parameter CP. The chargeable battery system 10 is able to adjust the amount of charge per unit time to the auxiliary battery 60 by increasing the number of the step-down devices 50 that charge the auxiliary battery 60.

[0061] (6) The control device 80 selects the step-down device 50 to be suspended on the basis of the acquired load parameter LP when decreasing the number of the step-down devices 50 in operation. The chargeable battery system 10 selects the step-down device 50 with the largest load parameter LP as the step-down device 50 to be suspended. Thus, the chargeable battery system 10 is able to avoid excessive loads L on the step-down devices 50.

[0062] <Modification Example> The above-described embodiments can be modified and implemented as follows. The above-described embodiments and the following modification examples can be implemented in combination with each other within a range in which they are not technically contradictory.

[0063] • The configuration of the battery group 20 is not limited to the example of the above-described embodiment. The battery group 20 can include only the chargeable battery 21, and for example, the battery state monitoring device 22 can be included in the control device 80 or can be omitted from the chargeable battery system 10.

[0064] • The type of the chargeable battery 21 is not limited to the lithium-ion secondary battery. The chargeable battery 21 can also be a lead storage battery.

[0065] • The types of the chargeable batteries 21 included in the plurality of battery groups 20 can also be different from each other. For example, the chargeable battery system 10 can be provided with a battery group 20 including a chargeable battery 21 that is a lithium-ion secondary battery and a battery group 20 including a chargeable battery 21 that is a lead storage battery.

[0066] • The output voltages of the plurality of battery groups 20 can also be different. In this case, it is only necessary to adjust the output voltage of the power control unit 30 provided corresponding to each battery group 20 so that the same voltage is output to the output terminal 40.

[0067] The power control unit 30 can also output a boosted voltage to the output terminal 40 based on the voltage applied from the rechargeable battery 21. As in the modified example described above, when the output voltages from multiple battery packs 20 are different, the power control unit 30 can boost or buck the applied voltage according to the output voltage from the corresponding battery pack 20.

[0068] The specified voltage for adjusting the voltage output to the output terminal 40 by the power control unit 30 is not limited to 200V. For example, the specified voltage could also be 100V. The power control unit 30 may also not convert the applied current from DC to AC.

[0069] In the above embodiment, the number of battery packs 20, power control units 30, and step-down devices 50 is three, but not limited to this. Their number can be two or more.

[0070] The number of step-down devices 50 may not be the same as the number of power control units 30. For example, in Figure 4 In the example shown, the number of step-down devices 50 in the rechargeable battery system 110 is less than the number of power control units 30. One of the multiple step-down devices 50 is connected to two battery packs 20. Voltage is applied to this step-down device 50 from two rechargeable batteries 21. Therefore, there are three battery packs 20, and two step-down devices 50. Thus, the multiple step-down devices 50 can also include step-down devices 50 that apply voltage from more than two rechargeable batteries 21. Therefore, it is not necessary to provide a separate step-down device 50 for each battery pack 20.

[0071] In this case, the switch 52 of the step-down device 50 can also be switched to allow voltage to be applied to the DC-DC converter 51 from any one of the two or more rechargeable batteries 21. The rechargeable battery system 10 may also have only one step-down device 50. In this case, one step-down device 50 can be connected to all the battery packs 20.

[0072] • The number of auxiliary devices 70 can also be one. For example, the rechargeable battery system 10 may only have a control device 80 as an auxiliary device 70.

[0073] • The auxiliary device 70 may not be connected to the second output wiring 55. The auxiliary device 70 only needs to be driven by at least the output voltage from the auxiliary battery 60.

[0074] • The timing at which the control device 80 causes the step-down device 50 to start operation is not limited to the timing at which the chargeable battery system 10 starts operation. For example, the control device 80 can also cause the step-down device 50 to start operation when the charge amount of the auxiliary battery 60 becomes less than a prescribed amount. In this case, as long as the execution device 81 starts charging of the auxiliary battery 60 by a predetermined one of the plurality of step-down devices 50 when the charge amount of the auxiliary battery 60 becomes less than the prescribed amount.

[0075] • The control device 80 can also not select the step-down device 50 to be suspended on the basis of the load parameter LP. For example, the control device 80 can also, in the process of Step S26, randomly select a step-down device 50 to be suspended when there are a plurality of step-down devices 50 that are operating. Also, for example, the control device 80 can also, in the process of Step S26, cause the step-down device 50 having the smallest identification number to be suspended when there are a plurality of step-down devices 50 that are operating.

[0076] • The method by which the control device 80 increases and decreases the number of step-down devices 50 that are operating on the basis of the charge parameter CP is not limited to the example of the above-described embodiment. For example, the control device 80 can also drive one step-down device 50 to which a predetermined identification number is assigned when causing one step-down device 50 to operate, and on the other hand, drive two step-down devices 50 to which two predetermined identification numbers are respectively assigned when causing two step-down devices 50 to operate. That is, the method by which the number of step-down devices 50 that are operating is increased and decreased is not limited to causing one of the step-down devices 50 that are operating to be suspended, or causing one of the step-down devices 50 that are suspended to operate. As long as a predetermined combination of step-down devices 50 is set for each number of step-down devices 50 that are operating, the control device 80 can increase and decrease the number of step-down devices 50 that are operating by switching the combination of step-down devices 50 that are operating.

[0077] • The control device 80 can also increase the number of step-down devices 50 that are operating on the basis of only the charge parameter CP. In this case, the execution device 81 can omit the processes of Step S25 and Step S26 in the second charging program P2.

[0078] • The control device 80 can also decrease the number of step-down devices 50 that are operating on the basis of only the charge parameter CP. For example, the control device 80 can also gradually decrease the number of step-down devices 50 that are operating after causing all of the step-down devices 50 to operate at the start of operation of the chargeable battery system 10. In this case, the execution device 81 can omit the processes of Step S23 and Step S24 when executing the second charging program P2, and can perform the process of Step S25 after the process of Step S22.

[0079] • The control device 80 can also not increase or decrease the number of the step-down devices 50 that are made to act based on the charge parameter CP. In this case, the execution device 81 can simply not execute the second charge program P2. For example, the control device 80 can also always make the same number of the step-down devices 50 act.

[0080] • The load parameter LP is not limited to the continuous operation time. For example, the load parameter LP can also be a heat generation amount that is calculated based on the continuous operation time and the current value. The heat generation amount is a value that is larger the longer the continuous operation time is and the larger the current value is. In addition, for example, the load parameter LP can also be a cumulative value of the current value.

[0081] • The method by which the control device 80 selects the next step-down device 50 that is made to act when switching the step-down device 50 that is made to act based on the load parameter LP is not limited to the example of the above-described embodiment. The control device 80 can also randomly select the next step-down device 50 that is made to act instead of selecting the next step-down device 50 that is made to act based on the identification number.

[0082] In addition, for example, the control device 80 can also store a history of the load parameter LP in the storage device 84 and select the next step-down device 50 that is made to act based on the history of the load parameter LP. In detail, for example, the control device 80 can select the step-down device 50 for which the cumulative value of the load parameter LP is the smallest as the next step-down device 50 that is made to act in the case where the cumulative value of the load parameter LP is stored.

[0083] • The control device 80 can also not switch the step-down device 50 for partial charge control based on the acquired load parameter LP. In this case, the execution device 81 can simply not execute the first charge program PI.

[0084] • The control device 80 can also not perform partial charge control. The control device 80 can also charge the auxiliary battery 60 by making all of the step-down devices 50 act. In the above-described embodiment, in the case where the execution device 81 executes the first charge program PI, partial charge control is performed by only a part of the plurality of step-down devices 50 even in the case where the number of the step-down devices 50 that are made to act by the second charge program P2 is two or more.

[0085] • The control device 80 can have: 1) a processing circuit including one or more processors that execute various processes according to a computer program (software); 2) a processing circuit including one or more special-purpose hardware circuits such as an application-specific integrated circuit (ASIC) that execute at least a part of the various processes; or 3) a processing circuit including a combination of the above processing circuits. The processor includes a CPU and a memory such as a RAM and a ROM. The memory stores program codes or instructions that configure the CPU to execute the processes. The memory, which is a computer-readable medium, includes various available media that can be accessed by a general-purpose or special-purpose computer.

[0086] • The sensor 90 is not limited to a sensor that detects the load current LA. For example, the sensor 90 can also include a sensor that detects the charge amount of the auxiliary battery 60. In this case, the control device 80 can also acquire the charge amount of the auxiliary battery 60 acquired from the sensor 90 as the charge parameter CP. Also, for example, the sensor 90 can include a sensor that detects the operation time of each voltage reduction device 50. In this case, the control device 80 can also acquire the operation time of each voltage reduction device 50 acquired from the sensor 90 as the load parameter LP.

[0087] • The rechargeable battery system 10 can also not have the control device 80 that controls the plurality of voltage reduction devices 50. For example, all of the voltage reduction devices 50 can always charge the auxiliary battery 60 while the rechargeable battery system 10 is operating.

Claims

1. A rechargeable battery system comprising: a plurality of battery packs including rechargeable batteries capable of charge and discharge; a plurality of power control units configured to be provided corresponding to the plurality of battery packs one by one and to adjust a voltage applied from the corresponding rechargeable batteries; and an output terminal configured to be applied with a voltage adjusted by the plurality of power control units, the rechargeable battery system further comprising: a step-down device configured to step down the voltage applied from the rechargeable batteries to a voltage lower than a voltage output from the output terminal; an auxiliary battery configured to be applied with a voltage stepped down by the step-down device; and an auxiliary device configured to be driven by the auxiliary battery.

2. The rechargeable battery system according to claim 1, wherein the step-down device is one of a plurality of step-down devices provided corresponding to the plurality of battery packs one by one, and the number of the step-down devices is the same as the number of the power control units.

3. The rechargeable battery system according to claim 1, wherein the step-down device is one of a plurality of step-down devices, the plurality of step-down devices include step-down devices configured to be applied with a voltage from two or more of the rechargeable batteries, and the number of the plurality of step-down devices is less than the number of the power control units.

4. The rechargeable battery system according to claim 1, wherein the step-down device is one of a plurality of step-down devices, the rechargeable battery system further comprises a control device configured to control the plurality of step-down devices, and the control device is configured to perform partial charging control of charging the auxiliary battery only by a part of the plurality of step-down devices.

5. The rechargeable battery system according to claim 4, wherein the control device is configured to acquire a load parameter indicating a degree of a load of each of the step-down devices, and switch the step-down device used for the partial charging control on the basis of the acquired load parameter.

6. The rechargeable battery system according to claim 4 or 5, wherein the control device is configured to acquire a charging parameter related to a charging amount per unit time to the auxiliary battery, and increase or decrease the number of the step-down devices that act for charging of the auxiliary battery on the basis of the acquired charging parameter.

7. The rechargeable battery system according to claim 1, comprising a control device configured to control the step-down device, the control device being configured to acquire a load parameter indicating a degree of a load of the step-down device, and stop charging of the auxiliary battery by the step-down device on the basis of the acquired load parameter. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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