Storage battery system

Abstract

To provide a storage battery system that eliminates the need for providing an additional power source.SOLUTION: The storage battery system 10 includes a plurality of battery packs 20, a plurality of power control units 30, and an output terminal 40. The battery pack 20 includes a chargeable / dischargeable storage battery 21. One power control unit 30 is provided for one battery pack 20. The power control unit 30 adjusts the voltage applied from the storage battery 21. The plurality of power control units 30 apply adjusted voltages to the output terminal 40. The storage battery system 10 further includes a step-down device 50, an auxiliary battery 60, and an auxiliary device 70. The step-down device 50 steps down the voltage applied from the storage battery 21 to a voltage lower than the voltage output from the output terminal 40. A voltage stepped down by the step-down device 50 is applied to the auxiliary battery 60. Auxiliary device 70 is driven by auxiliary battery 60.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a storage battery system. [Background technology]

[0002] Patent Document 1 describes a storage battery system. The storage battery system includes a storage battery, a power control unit, and an output terminal. The power control unit adjusts the voltage applied from the storage battery. The voltage from the power control unit is output to the output terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-080835 Summary of the Invention [Problem to be solved by the invention]

[0004] In a battery storage system such as that described in Patent Document 1, an auxiliary device may be provided that is driven by a low voltage lower than the voltage output from the output terminal. In this case, a power source that outputs a low voltage to drive the auxiliary device is required. However, if the low voltage is supplied from outside the battery storage system, an additional power source is required. [Means for solving the problem]

[0005] In order to solve the above problem, the storage battery system comprises a plurality of battery packs including rechargeable storage batteries, a plurality of power control units, one for each of the battery packs, that adjust the voltage applied from the storage batteries, and output terminals to which the adjusted voltages from the plurality of power control units are applied, and further comprises a step-down device that steps down the voltage applied from the storage batteries to a voltage lower than the voltage output from the output terminal, an auxiliary battery to which the stepped-down voltage from the step-down device is applied, and an auxiliary device driven by the auxiliary battery. [Effects of the Invention]

[0006] The battery system described above uses a step-down device to step down the voltage applied from the battery pack, thereby supplying the auxiliary battery with a low voltage sufficient to drive the auxiliary device, eliminating the need for an additional power source. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing a storage battery system according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing a series of processes performed by the control device of the embodiment. [Figure 3] FIG. 3 is a flowchart showing a series of processes performed by the control device of the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a storage battery system according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of a storage battery system will be described with reference to the drawings. <Battery storage system overview> The battery system 10 is a system including a large-scale stationary battery for supplying approximately 1000 kW of power, for example. The battery system 10 includes a plurality of battery packs 20, a plurality of first connection lines 25, a plurality of second connection lines 26, a plurality of power control units 30, a plurality of first output lines 35, and an output terminal 40.

[0009] The battery pack 20 includes a rechargeable storage battery 21. The storage battery 21 is, for example, a lithium-ion secondary battery. An upstream end of a first connection wiring 25 and an upstream end of a second connection wiring 26 are connected to the battery pack 20. The storage battery 21 applies a voltage to the first connection wiring 25. The voltage applied from the storage battery 21 to the first connection wiring 25 is, for example, 400 V DC. In this embodiment, the storage battery 21 is a battery that can be used as an on-board storage battery installed in a vehicle.

[0010] The battery pack 20 includes a battery state monitoring device 22 and a cutoff relay 23. The battery state monitoring device 22 monitors the state of the storage battery 21. The cutoff relay 23 is configured to be able to cut off discharge from the storage battery 21. The cutoff relay 23 is controlled by the battery state monitoring device 22, and is therefore able to switch between operating and pausing discharge from the storage battery 21.

[0011] The power control unit 30 adjusts the voltage applied from the storage battery 21. The power control unit 30 is connected to the downstream end of the first connection wiring 25. In FIG. 1, the power control unit 30 is illustrated as a PCU.

[0012] The power control unit 30 receives the voltage applied from the storage battery 21 via the first connection wiring 25 as an input voltage and adjusts the input voltage to a predetermined specified voltage. The specified voltage is, for example, 200 V. The power control unit 30 then 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 specified voltage to the first output wiring 35.

[0013] The plurality of power control units 30 adjust their respective input voltages to specified voltages. Then, the plurality of power control units 30 apply the adjusted specified voltages to the first output wirings 35. The downstream ends of the plurality of first output wirings 35 are connected to the output terminal 40.

[0014] Furthermore, one power control unit 30 is connected to one battery pack 20 via the first connection wiring 25. That is, one power control unit 30 is provided for one battery pack 20. Therefore, the number of battery packs 20 is the same as the number of power control units 30.

[0015] The output terminal 40 receives a specified voltage adjusted by the plurality of power control units 30. That is, the specified voltage adjusted by each of the plurality of power control units 30 is applied to the output terminal 40. In this embodiment, an AC voltage of 200 V is applied to the output terminal 40. The output terminal 40 outputs the specified voltage to a device or the like connected to the output terminal 40.

[0016] The storage battery system 10 includes a plurality of step-down devices 50, a plurality of second output wirings 55, an auxiliary battery 60, a plurality of auxiliary devices 70, a control device 80, and various sensors 90 for acquiring a load parameter LP.

[0017] The step-down device 50 is connected to the downstream end of the second connection wiring 26. The step-down device 50 steps down the voltage applied from the storage battery 21 via the second connection wiring 26 to a voltage lower than the voltage output from the output terminal 40. For example, the voltage stepped down by the step-down device 50 is 12V.

[0018] The step-down device 50 includes a DC-DC converter 51 and a switch 52. The switch 52 switches the DC-DC converter 51 between an operating state and a resting state. When the DC-DC converter 51 is operating, the step-down device 50 is charging the auxiliary battery 60. When the DC-DC converter 51 is resting, the step-down device 50 is stopping charging the auxiliary battery 60. The operation of the switch 52 enables the DC-DC converter 51 to be switched between operating and resting. In FIG. 1, the switch 52 is illustrated as SW.

[0019] The DC-DC converter 51 is connected to the upstream end of the second output wiring 55. The DC-DC converter 51 applies a stepped-down voltage obtained by stepping down the voltage applied from the storage battery 21 to the second output wiring 55. In FIG. 1, the DC-DC converter 51 is illustrated as DCDC.

[0020] Each of the plurality of step-down devices 50 steps down a voltage. Then, the plurality of step-down devices 50 apply the stepped-down voltage to each of the second output wirings 55. The downstream ends of the plurality of second output wirings 55 are connected to the auxiliary battery 60.

[0021] In this way, one step-down device 50 is connected to one battery pack 20 via the 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. Therefore, the number of step-down devices 50 is the same as the number of power control units 30.

[0022] The auxiliary battery 60 is connected to downstream ends of the plurality of second output wirings 55. A stepped-down voltage from the plurality of step-down devices 50 is applied to the auxiliary battery 60 via the plurality of second output wirings 55. The auxiliary battery 60 is, for example, a lead storage battery.

[0023] The auxiliary device 70 is connected to the second output wiring 55. The auxiliary device 70 is also connected to the auxiliary battery 60 via a wiring. Therefore, the auxiliary device 70 is driven by the voltage applied to the second output wiring 55 or the auxiliary battery 60. A switching relay (not shown) switches the power supply source to the auxiliary device 70 between the second output wiring 55 and the auxiliary battery 60.

[0024] The auxiliary device 70 is driven by a low voltage of 12 V output from the auxiliary battery 60. The auxiliary device 70 is, for example, a control circuit of the power control unit 30, a cooling device of the storage battery system 10, and a circuit that manages the entire storage battery system 10. In this embodiment, one of the multiple auxiliary devices 70 is a control device 80. In other words, the control device 80 is driven by power supplied from the auxiliary battery 60.

[0025] The control device 80 controls the plurality of step-down devices 50. As will be described later, the control device 80 performs partial charging control in which some of the step-down devices 50 are operated to charge the auxiliary battery 60.

[0026] The various sensors 90 acquire the load current LA of each step-down device 50. The control device 80 acquires the load current LA from each step-down device 50 acquired by the sensors 90. The sensors 90 are current sensors.

[0027] The control device 80 acquires the continuous operation time as a load parameter LP indicating the load L of each step-down device 50, based on the load current LA acquired from the sensor 90. In this way, the control device 80 acquires the load parameter LP for each step-down device 50.

[0028] The control device 80 also calculates the total value of the load currents LA from each step-down device 50 obtained from the sensor 90 as a charging parameter CP for the auxiliary battery 60. The charging parameter CP is a parameter that correlates with the amount of charge per unit time. In this embodiment, the charging parameter CP is the amount of charge per unit time. In this way, the control device 80 obtains the charging parameter CP for the auxiliary battery 60.

[0029] The control device 80 selects the step-down device 50 to be operated to charge the auxiliary battery 60 using the acquired load parameter LP and charging parameter CP for the auxiliary battery 60. The control device 80 includes an execution device 81 which is a CPU, a peripheral circuit 82, a RAM 83, a storage device 84, and a bus 85. The bus 85 connects the execution device 81, the peripheral circuit 82, the RAM 83, and the storage device 84 so that they can communicate with one another.

[0030] The execution device 81 processes information by executing various programs stored in the storage device 84. The peripheral circuit 82 includes a circuit that generates a clock signal that regulates internal operation, a power supply circuit, a reset circuit, etc. The RAM 83 stores data generated as the execution device 81 operates. The storage device 84 stores a first charging program P1 and a second charging program P2 for the auxiliary battery 60 by the step-down devices 50 that are executed by the execution device 81. The first charging program P1 is a program for switching the step-down devices 50 to be operated, with the step-down devices 50 being the target. The second charging program P2 is a program for increasing or decreasing the number of step-down devices 50 to be operated, with the auxiliary battery 60 being charged.

[0031] The execution device 81 performs partial charging control in which the auxiliary battery 60 is charged only by some of the step-down devices 50 among the plurality of step-down devices 50. Specifically, when operation of the battery storage system 10 is started, the execution device 81 starts charging the auxiliary battery 60 by one predetermined step-down device 50 among the plurality of step-down devices 50.

[0032] <Switching of step-down device 50> When charging of the auxiliary battery 60 by the step-down device 50 is started, the execution device 81 starts executing the first charging program P1 for the step-down device 50 in question.

[0033] 2, when the execution device 81 starts executing the first charging program P1, the execution device 81 first performs the process of step S11. In step S11, the execution device 81 determines whether the storage battery system 10 has stopped operating. If the storage battery system 10 has stopped operating (S11: YES), the execution device 81 stops charging by the target step-down device 50 and ends the current series of processes.

[0034] On the other hand, when the operation of the storage battery system 10 is not stopped (S11: NO), the executing device 81 proceeds to step S12. In step S12, the executing device 81 acquires the load parameter LP of the target step-down device 50. Thereafter, the executing device 81 proceeds to step S13.

[0035] In step S13, the execution device 81 determines whether the load L indicated by the acquired load parameter LP is greater than a predetermined specified load RL. The specified load RL is set in advance through testing or simulation as a continuous operation time that results in a load that does not cause excessive heat generation. In this embodiment, the execution device 81 determines whether the continuous operation time that is the acquired load parameter LP is shorter than the time that results in the specified load RL. If the load L indicated by the load parameter LP is equal to or less than the specified load RL (S13: NO), the execution device 81 returns the process to step S11.

[0036] On the other hand, if the load L indicated by the load parameter LP is greater than the specified load RL (S13: YES), the executing device 81 proceeds to step S14. In step S14, the executing device 81 stops the operation of the target step-down device 50. Thereafter, the executing device 81 proceeds to step S15.

[0037] 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 step-down device 50 that starts the operation in step S15 is determined according to a predetermined order.

[0038] For example, identification numbers are assigned to a plurality of step-down devices 50. Then, the executing device 81 selects a step-down device 50 that has been assigned an identification number next to the identification number of the step-down device 50 that was stopped in step S14 as another step-down device 50 and subjects it to the processing of step S15. Thereafter, the executing device 81 ends this series of processing.

[0039] Note that, as a result of the processing of step S15, the execution device 81 starts executing the first charging program P1 for the other step-down device 50 that has started operating. As a result, the execution device 81 performs the processing of steps S11 to S15 for the other step-down device 50.

[0040] In this way, the executing device 81 switches between the step-down devices 50 to be operated based on the load parameter LP of the step-down device 50 to be operated. In particular, in this embodiment, the executing device 81 switches between the step-down devices 50 to be operated in order. That is, the executing device 81 charges the auxiliary battery 60 by operating some of the step-down devices 50 in rotation among the plurality of step-down devices 50.

[0041] <Increase or decrease in the number of step-down devices 50> When charging of the auxiliary battery 60 by the step-down device 50 starts, the execution device 81 starts executing the second charging program P2.

[0042] 3, when the execution device 81 starts executing the second charging program P2, the execution device 81 first performs the process of step S21. In step S21, the execution device 81 determines whether the storage battery system 10 has stopped operating. If the storage battery system 10 has stopped operating (S21: YES), the execution device 81 stops charging by the target step-down device 50 and ends the current series of processes.

[0043] On the other hand, if the operation of the storage battery system 10 is not stopped (S21: NO), the execution device 81 proceeds to step S22. In step S22, the execution device 81 acquires the charging parameters CP of the auxiliary battery 60. Thereafter, the execution device 81 proceeds to step S23.

[0044] In step S23, the execution device 81 determines whether the charging parameter CP is smaller than a predetermined lower limit value L1. The lower limit value L1 is the lower limit of the charge amount per unit time required to charge the auxiliary battery 60. The lower limit value L1 is determined in advance through testing and simulation as the minimum charge amount per unit time required to charge the auxiliary battery 60.

[0045] When the charging parameter CP is smaller than the lower limit value L1 (S23: YES), the executing device 81 proceeds to step S24. In step S24, the executing device 81 increases the number of step-down devices 50 to be operated by one. That is, the executing device 81 adds one of the step-down devices 50 that are inactive as a step-down device 50 to be operated.

[0046] Specifically, the executing device 81 selects one of the step-down devices 50 that are inactive among the plurality of step-down devices 50 as the step-down device 50 to be added. For example, the executing device 81 extracts a step-down device 50 that has an identification number that is larger by a predetermined value than the identification number of the step-down device 50 that is in operation among the plurality of step-down devices 50. If the extracted step-down device 50 is inactive, the executing device 81 selects the step-down device 50 as the step-down device 50 to be added. On the other hand, if the extracted step-down device 50 is in operation, the executing device 81 again extracts a step-down device 50 that has an identification number next to that of the extracted step-down device 50. By repeating this process, the executing device 81 selects the inactive step-down device 50 as the step-down device 50 to be added. Note that if all step-down devices 50 are in operation, the executing device 81 continues the process as is. Thereafter, the executing device 81 returns the process to step S21.

[0047] However, when the charging parameter CP is equal to or greater than the lower limit L1 (S23: NO), the execution device 81 proceeds to step S25. In step S25, the execution device 81 determines whether the charging parameter CP is equal to or greater than the upper limit L2. The upper limit L2 is the excessive charge amount per unit time when charging the auxiliary battery 60. The upper limit L2 is determined in advance through testing and simulation as the excessive charge amount per unit time when charging the auxiliary battery 60.

[0048] If the charging parameter CP is smaller than the upper limit L2 (S25: NO), the execution unit 81 returns the process to step S21. On the other hand, if the charging parameter CP is equal to or greater than the upper limit L2 (S25: YES), the execution unit 81 proceeds to step S26.

[0049] In step S26, the executing device 81 reduces the number of operating step-down devices 50 by one. That is, the executing device 81 suspends one of the operating step-down devices 50. As a result, the executing device 81 stops charging the auxiliary battery 60 by that step-down device 50.

[0050] The executing device 81 selects the step-down device 50 to be put into a halt based on the load parameter LP. Specifically, the executing device 81 selects one of the step-down devices 50 that are operating among the plurality of step-down devices 50 as the step-down device 50 to be put into a halt. For example, the executing device 81 selects the step-down device 50 with the largest load parameter LP among the operating step-down devices 50 as the step-down device 50 to be put into a halt. Thereafter, the executing device 81 returns the process to step S21.

[0051] In this way, while the storage battery system 10 continues to operate, the executing device 81 increases or decreases the number of operating step-down devices 50 based on the charging parameter CP for the auxiliary battery 60. Then, when the storage battery system 10 stops operating (S21: YES), the executing device 81 ends the series of processes.

[0052] <Operation of this embodiment> The storage battery system 10 includes a step-down device 50, an auxiliary battery 60, and an auxiliary device 70. The step-down device 50 steps down the voltage applied from the storage battery 21 to a voltage lower than the voltage output from the output terminal 40. The auxiliary battery 60 receives the stepped-down voltage from the step-down device 50. The auxiliary device 70 is driven by power supplied from the auxiliary battery 60.

[0053] <Effects of this embodiment> (1) The storage battery system 10 uses the step-down device 50 to step down the voltage applied from the storage battery 21, thereby applying a low voltage to the auxiliary battery 60 that drives the auxiliary device 70. Therefore, the storage battery system 10 does not necessarily need to provide an additional power source to drive the auxiliary device 70.

[0054] (2) The number of step-down devices 50 is the same as the number of power control units 30. That is, in the storage battery system 10, a step-down device 50 is provided corresponding to each of all the battery packs 20. Therefore, it is possible to separately supply low voltages from the storage batteries 21 of all the battery packs 20.

[0055] (3) The battery storage system 10 includes a plurality of step-down devices 50 and a control device 80 that controls the plurality of step-down devices 50. The control device 80 performs partial charge control in which the auxiliary battery 60 is charged by only some of the step-down devices 50 among the plurality of step-down devices 50. By using partial charge control, the battery storage system 10 can suspend operation of the step-down devices 50 that are not performing charging while still charging the auxiliary battery 60. Therefore, by avoiding the step-down devices 50 from constantly operating due to charging, the battery storage system 10 can suppress accelerated deterioration of the step-down devices 50 that would otherwise occur if the same step-down devices 50 were operating for a long period of time.

[0056] (4) The control device 80 acquires a load parameter LP for each step-down device 50. The control device 80 switches between some of the step-down devices 50 that perform partial charge control based on the acquired load parameter LP. Therefore, the storage battery system 10 performs partial charge control using a step-down device 50 other than the step-down device 50 with a large load parameter LP. As a result, the step-down device 50 that is in operation can be put into a halt before the load L of the step-down device 50 becomes excessively large, and charging of the auxiliary battery 60 can be continued.

[0057] (5) The storage battery system 10 increases or decreases the number of step-down devices 50 to be charged based on the charging parameter CP. Therefore, the storage battery system 10 can adjust the amount of charge per unit time to the auxiliary battery 60 by increasing or decreasing the number of step-down devices 50 to be charged.

[0058] (6) When reducing the number of operating step-down devices 50, the control device 80 selects the step-down devices 50 to be inactive based on the acquired load parameter LP. The storage battery system 10 selects the step-down device 50 with the largest load parameter LP as the step-down device 50 to be inactive. Therefore, the storage battery system 10 can avoid applying an excessive load L to the step-down devices 50.

[0059] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0060] The configuration of the battery pack 20 is not limited to the example of the above embodiment. The battery pack 20 only needs to include the storage battery 21. For example, the battery state monitoring device 22 may be included in the control device 80 or may be omitted.

[0061] The type of storage battery 21 is not limited to a lithium ion secondary battery. The storage battery 21 may be a lead storage battery. The types of storage batteries 21 included in the multiple battery packs 20 may be different from each other. For example, the storage battery system 10 may include a battery pack 20 including a storage battery 21 that is a lithium-ion secondary battery and a battery pack 20 including a storage battery 21 that is a lead-acid battery.

[0062] The battery packs 20 may have different output voltages. Even in this case, the power control units 30 provided for each step-down device 50 need only adjust the output voltages to the output terminals 40 so that the same voltage is output.

[0063] The power control unit 30 may output a boosted voltage to the output terminal 40 in accordance with the voltage applied from the storage battery 21. When the output voltages from the plurality of battery packs 20 are different, as in the above-described modified example, the power control unit 30 may boost or lower the voltage in accordance with the output voltage from the corresponding battery pack 20.

[0064] The specified voltage that the power control unit 30 adjusts to the output terminal 40 is not limited to 200 V. It may be 100 V. Furthermore, the power control unit 30 does not need to convert from DC to AC.

[0065] In the above embodiment, the number of battery packs 20, the number of power control units 30, and the number of step-down devices 50 are three, but this is not limited to three. They may be two, or four or more.

[0066] The number of step-down devices 50 does not have to be the same as the number of power control units 30. For example, in the example shown in FIG. 4 , the number of step-down devices 50 in the storage battery system 110 is smaller than the number of power control units 30. Of the multiple step-down devices 50, one step-down device 50 is connected to two battery packs 20. Voltage is applied to the step-down device 50 from two storage batteries 21. Therefore, while there are three battery packs 20, there are only two step-down devices 50. In this way, the multiple step-down devices 50 may include a step-down device 50 to which voltage is applied from two or more storage batteries 21. This eliminates the need to provide a step-down device 50 for each of the battery packs 20.

[0067] In this case, the switch 52 of the step-down device 50 may be switchable so that voltage is applied from one of the storage batteries 21 to the DC-DC converter 51. Also, the storage battery system 10 may be provided with only one step-down device 50. In this case, it is sufficient that the step-down device 50 is connected to all the battery packs 20.

[0068] The number of auxiliary devices 70 may be one. For example, the battery system 10 may include only the control device 80 as the auxiliary device 70. The auxiliary device 70 does not have to 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.

[0069] The timing at which the control device 80 starts operation of the step-down device 50 is not limited to the timing at which the storage battery system 10 starts operation. For example, the control device 80 may start operation of the step-down device 50 when the charge level of the auxiliary battery 60 falls below a specified level. In this case, the execution device 81 may start charging the auxiliary battery 60 using a predetermined one of the step-down devices 50 when the charge level of the auxiliary battery 60 falls below the specified level.

[0070] The control device 80 does not have to select the step-down device 50 to be put into a halt based on the load parameter LP. For example, in the process of step S26, when there are multiple step-down devices 50 in operation, the control device 80 may randomly select a step-down device 50 as the step-down device 50 to be put into a halt. Also, for example, in the process of step S26, when there are multiple step-down devices 50 in operation, the control device 80 may put into a halt the step-down device 50 with the smallest identification number.

[0071] The method of increasing or decreasing the number of step-down devices 50 based on the charging parameter CP of the control device 80 is not limited to the example of the above embodiment. For example, the control device 80 may drive the step-down device 50 with a predetermined identification number when operating one step-down device 50, but may drive the step-down device 50 with a predetermined identification number when operating two step-down devices 50. In other words, the method of increasing or decreasing the number of step-down devices 50 is not limited to pausing one of the step-down devices 50 that are operating or operating one of the step-down devices 50 that are paused. If 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 or decrease the number of step-down devices 50 by switching the combination of step-down devices 50 that are operating.

[0072] The control device 80 may simply increase the number of step-down devices 50 based on the charging parameter CP. In this case, the execution device 81 may omit the processes of steps S25 and S26.

[0073] The control device 80 may simply reduce the number of step-down devices 50 based on the charging parameter CP. For example, the control device 80 may operate all of the step-down devices 50 when the storage battery system 10 starts operating, and then gradually reduce the number of step-down devices 50. In this case, the execution device 81 may omit the processes of steps S23 and S24, and perform the process of step S25 after the process of step S22.

[0074] The control device 80 does not need to increase or decrease the number of step-down devices 50 based on the charging parameter CP. In this case, the execution device 81 does not need to execute the second charging program P2. For example, the control device 80 may always operate the same number of step-down devices 50.

[0075] The load parameter LP is not limited to the continuous operation time. For example, the load parameter LP may be the heat generation amount calculated based on the continuous operation time and the current value. The heat generation amount increases as the continuous operation time increases and as the current value increases. Furthermore, for example, the load parameter LP may be the integrated value of the current value.

[0076] When the control device 80 switches the step-down device 50 to be operated based on the load parameter LP, the method of selecting the step-down device 50 to be operated next is not limited to the example in the above embodiment. The control device 80 may randomly select the step-down device 50 to be operated next without being limited to the identification number.

[0077] Furthermore, for example, the control device 80 may store a history of the load parameter LP in the storage device 84, and select the step-down device 50 to be operated next based on the history of the load parameter LP. In particular, when the control device 80 stores the integrated value of the load parameter LP, it may select the step-down device 50 having the smallest integrated value of the load parameter LP as the step-down device 50 to be operated next.

[0078] The control device 80 may not switch among some of the step-down devices 50 that perform partial charging control based on the acquired load parameter LP. In this case, the execution device 81 may not execute the first charging program P1.

[0079] The control device 80 does not have to perform partial charge control. The control device 80 may charge the auxiliary battery 60 by operating all of the step-down devices 50. Note that in the above embodiment, even if the number of operating step-down devices 50 becomes two or more due to the second charging program P2 while the execution device 81 is executing the first charging program P1, partial charge control is performed using some of the step-down devices 50.

[0080] The control device 80 may be configured as a circuit including one or more processors that execute various processes according to a computer program (software). The control device 80 may also be configured as a circuit including one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that execute at least some of the various processes, or a combination thereof. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0081] The sensor 90 is not limited to one that detects the load current LA. For example, the sensor 90 may include one that detects the charge amount of the auxiliary battery 60. Furthermore, for example, the sensor 90 may include one that detects the operating time of each step-down device 50. In these cases, the control device 80 may acquire the charge amount of the auxiliary battery 60 from the sensor 90 as a charge parameter CP, or may acquire the operating time of each step-down device 50 from the sensor 90 as a load parameter LP.

[0082] The battery system 10 does not need to include a control device 80 that controls multiple step-down devices 50. For example, when the battery system 10 is operating, all of the step-down devices 50 may always charge the auxiliary battery 60.

[0083] <Additional Notes> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. [Appendix 1] A storage battery system comprising a plurality of battery packs including rechargeable storage batteries, a plurality of power control units, one for each of the battery packs, that adjust the voltage applied from the storage batteries, and output terminals to which the adjusted voltages from the plurality of power control units are applied, the storage battery system further comprising a step-down device that steps down the voltage applied from the storage batteries to a voltage lower than the voltage output from the output terminals, an auxiliary battery to which the stepped-down voltage from the step-down device is applied, and an auxiliary device driven by the auxiliary battery.

[0084] [Appendix 2] A storage battery system as described in Appendix 1, comprising a plurality of the step-down devices, one step-down device for each battery pack, and the number of the step-down devices being the same as the number of the power control units.

[0085] [Appendix 3] A storage battery system as described in Appendix 1, comprising a plurality of the step-down devices, including a step-down device to which voltage is applied from two or more of the storage batteries, and the number of the step-down devices is less than the number of the power control units.

[0086] [Appendix 4] A storage battery system as described in any one of Appendices 1 to 3, comprising a plurality of the step-down devices and a control device that controls the plurality of step-down devices, wherein the control device performs partial charging control in which the auxiliary battery is charged only by some of the step-down devices among the plurality of step-down devices.

[0087] [Appendix 5] The control device acquires load parameters indicating the degree of load on each step-down device, and switches between the some of the step-down devices that perform the partial charging control based on the acquired load parameters.

[0088] [Appendix 6] A storage battery system as described in Appendix 4 or Appendix 5, wherein the control device acquires charging parameters that correlate with the amount of charge per unit time to the auxiliary battery, and increases or decreases the number of step-down devices that charge the auxiliary battery based on the acquired charging parameters.

[0089] [Appendix 7] A storage battery system according to any one of Appendices 1 to 6, comprising a control device for controlling the step-down device, wherein the control device acquires a load parameter indicating the degree of load on the step-down device, and stops charging by the step-down device based on the acquired load parameter. [Explanation of symbols]

[0090] 10, 110... Battery storage system 20...Battery pack 21...Storage battery 22...Battery status monitor 23...Shut-off relay 25...First connection wiring 26...Second connection wiring 30...Power control unit 35...First output wiring 40...Output terminal 50...Step-down device 51...DCDC converter 52...Switch 55...Second output wiring 60...Auxiliary battery 70...Auxiliary equipment 80...Control device 81...Execution device 82...Peripheral circuit 83...RAM 84…Storage device 85...Bus 90...Sensor CP: Charging parameters L...Load L1: Lower limit L2: Upper limit LA…Load current LP: Load parameter P1: First charging program P2: Second charging program RL…specified load

Claims

1. A storage battery system comprising: a plurality of battery packs including chargeable and dischargeable storage batteries; a plurality of power control units provided for each of the battery packs and adjusting voltages applied from the storage batteries; and output terminals to which the adjusted voltages from the plurality of power control units are applied, The power supply further includes a step-down device that steps down the voltage applied from the storage battery to a voltage lower than the voltage output from the output terminal, an auxiliary battery to which the voltage stepped down from the step-down device is applied, and an auxiliary device that is driven by the auxiliary battery. Battery storage system.

2. The system includes a plurality of the step-down devices, One step-down device is provided for one battery pack, The number of the step-down devices is the same as the number of the power control units. The battery system according to claim 1 .

3. The system includes a plurality of the step-down devices, the plurality of step-down devices include step-down devices to which voltages are applied from two or more of the storage batteries, The number of the plurality of step-down devices is less than the number of the power control units. The battery system according to claim 1 .

4. a plurality of the step-down devices; and a control device that controls the plurality of the step-down devices, The control device performs partial charging control to charge the auxiliary battery only by some of the step-down devices. The battery system according to claim 1 .

5. The control device acquiring a load parameter indicating the degree of load for each of the step-down devices; The part of the step-down devices that performs the partial charge control is switched based on the acquired load parameters. The battery system according to claim 4 .

6. The control device acquiring a charging parameter correlated with a charging amount per unit time to the auxiliary battery; The number of the step-down devices that charge the auxiliary battery is increased or decreased based on the acquired charging parameters. The battery system according to claim 4 or claim 5.

7. a control device for controlling the step-down device, the control device acquires a load parameter indicating a degree of load on the step-down device; Charging by the step-down device is stopped based on the acquired load parameters. The battery system according to claim 1 .

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