Control method and power supply system for zinc batteries

Abstract

This invention provides a control method for zinc batteries that can extend their lifespan. [Solution] This zinc battery control method involves repeatedly performing cycles that include charging the zinc battery and discharging the zinc battery after charging. Based on the state of charge (SOC) of the zinc battery, the timing of the end of charging and the end of discharging in each cycle are determined. The SOC of the zinc battery used as the criterion for determining the end of charging is less than 100%. The SOC of the zinc battery used as the criterion for determining the end of discharging is less than 50%.

Description

Technical Field

[0001] The present disclosure relates to a method for controlling a zinc battery and a power supply system.

Background Art

[0002] Patent Document 1 discloses a technique related to a battery control device. This battery control device includes an information acquisition unit and a control unit. The information acquisition unit acquires charge rate information regarding the charge rate of the battery and temperature information regarding the temperature of the battery. The control unit switches the battery to a discharged state when the charge rate of the battery is equal to or higher than a first threshold charge rate and the temperature of the battery drops below a first threshold temperature based on the charge rate information and the temperature information acquired by the information acquisition unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in automobiles and electric vehicles, a power supply system using a battery is used. In a power supply system using a battery, charging and discharging are repeated, and the battery gradually deteriorates (cycle deterioration). Therefore, the life of the battery is important. This is because the longer the life of the battery, the longer the battery replacement cycle, and the operating cost can be suppressed. In recent years, zinc batteries have attracted attention as the batteries of power supply systems. For example, a nickel-zinc battery is an aqueous battery using an aqueous electrolyte such as an aqueous potassium hydroxide solution, and thus has high safety. In addition, due to the combination of a zinc electrode and a nickel electrode, it has a high electromotive force as an aqueous battery. Furthermore, a nickel-zinc battery has advantages such as low cost in addition to excellent input / output performance.

[0005] One aspect of the present invention aims to provide a method for controlling a zinc battery and a power supply system equipped with a zinc battery that can extend the lifespan of the zinc battery. [Means for solving the problem]

[0006] [1] In order to solve the above-mentioned problems, a zinc battery control method according to one aspect of the present invention repeatedly performs cycles including charging the zinc battery and discharging the zinc battery after charging. Based on the size of the State of Charge (SOC) of the zinc battery, the end timing of charging and the end timing of discharging in each cycle are determined. The SOC of the zinc battery that serves as the criterion for determining the end timing of charging is less than 100%. The SOC of the zinc battery that serves as the criterion for determining the end timing of discharging is less than 50%. The power supply system also comprises a zinc battery and a control unit that controls the charging and discharging of the zinc battery. The control unit repeatedly performs cycles including charging the zinc battery and discharging the zinc battery after charging. Based on the size of the State of Charge (SOC) of the zinc battery, the control unit determines the end timing of charging and the end timing of discharging in each cycle. The SOC of the zinc battery that serves as the criterion for determining the end timing of charging is less than 100%. The SOC of the zinc battery that serves as the criterion for determining the end timing of discharging is less than 50%.

[0007] In these control methods and power supply systems, the State of Charge (SOC) of the zinc battery, which serves as the criterion for determining the end of charging, is less than 100%, and the SOC of the zinc battery, which serves as the criterion for determining the end of discharging, is less than 50%. Through our investigations conducted through cycle tests, we have found that when the SOC used as the criterion for determining the end of charging and discharging satisfies these conditions, the cycle life of the zinc battery is significantly extended. Therefore, the control method and power supply system described in [1] above can effectively extend the life of the zinc battery.

[0008] [2] In the control method or power supply system described in [1] above, the SOC of the zinc battery used as a criterion for determining the timing of the end of charging may be 95% or less. Alternatively, [3] In the control method or power supply system described in [1] above, the SOC of the zinc battery used as a criterion for determining the timing of the end of charging may be less than 80%.

[0009] [4] In any of the control methods or power supply systems described in [1] to [3] above, the difference between the State of Charge (SOC) of the zinc battery used as a criterion for determining the end of charging and the State of Charge (SOC) of the zinc battery used as a criterion for determining the end of discharging may be 95% or less.

[0010] [5] In any of the control methods or power supply systems described in [1] to [4] above, the difference between the State of Charge (SOC) of the zinc battery used as a criterion for determining the end of charging and the State of Charge (SOC) of the zinc battery used as a criterion for determining the end of discharging may be greater than 45%.

[0011] According to our findings through cycle tests, the cycle life of a zinc battery can be further extended when the State of Charge (SOC) used as a criterion for determining the end of charging, and / or the SOC used as a criterion for determining the end of discharging, satisfies any of the above conditions [2] to [5]. [Effects of the Invention]

[0012] According to one aspect of the present invention, a zinc battery control method and power supply system can extend the lifespan of the zinc battery. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram illustrating an example of a power supply system and its surrounding configuration. [Figure 2] Figure 2 shows an example of the hardware configuration of the control unit. [Figure 3] Figure 3 is a graph showing an example of the change in state of charge (SOC) of a zinc battery. [Figure 4]Figure 4 is a flowchart showing a method for controlling a zinc battery. [Figure 5] Figure 5 is a chart showing the results of the cycle test. [Figure 6] Figure 6 is a chart showing the results of the cycle test. [Modes for carrying out the invention]

[0014] Specific examples of the present disclosure will be described below with reference to the drawings. However, the present invention is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims, as defined by the claims. In the following description, identical elements in the drawings are denoted by the same reference numerals, and redundant descriptions are omitted.

[0015] Figure 1 is a schematic diagram showing an example of the configuration of the power supply system 1 and its surroundings. The application of the power supply system 1 is not limited to any particular situation; for example, the power supply system 1 can be applied to both stationary and mobile objects. The power supply system 1 can be installed in, for example, automobiles, industrial mobility (means of transportation and transport systems in the industrial sector), etc.

[0016] The power supply system 1 is installed between a supply element 2 capable of supplying power to the power supply system 1 and a demand element (load) 4 capable of receiving power from the power supply system 1. The power supply system 1, the supply element 2, and the demand element 4 are electrically connected via wiring 6 through which DC or AC current flows. The electricity generated by the supply element 2, or the power stored in the power supply system 1, is supplied to the demand element 4 through wiring 6.

[0017] Supply element 2 is a device or equipment capable of supplying power to power system 1. The type of supply element 2 is not limited in any way. For example, supply element 2 may be a power generation device mounted on a fixed or mobile object. The power generation method and the type of power generation device are not limited in any way.

[0018] The demand element 4 is a device or equipment that can receive power from the power supply system 1. The type of the demand element 4 is not limited in any way. The demand element 4 may be a load that is a set of one or more devices or apparatuses that consume power. Examples of the load include auxiliary machines and a starter motor mounted on an automobile.

[0019] The power supply system 1 includes a power converter 8, a zinc battery 10, a battery control unit (BCU) 12, and a control unit 14. The zinc battery 10 and the power converter 8 are electrically connected via a DC wiring 7. In the example of FIG. 1, the power supply system 1 includes one set of the power converter 8 and the zinc battery 10, but the number of sets is not limited and may be two or more. When there are a plurality of sets, the performance (for example, rated capacity, response speed, etc.) of the zinc battery 10 and the performance (for example, rated output, response speed, etc.) of the power converter 8 may be unified or may not be unified. The control unit 14 is communicably connected to the power converter 8 via a communication line.

[0020] The zinc battery 10 is a device that converts and stores the electricity provided from the supply element 2 into chemical energy and is capable of charge and discharge. The zinc battery 10 is, for example, a nickel-zinc battery and includes a plurality of cells connected in series. A BCU 12 as a control function is connected to the zinc battery 10. The BCU 12 transmits data regarding the zinc battery 10 to the control unit 14.

[0021] The BCU 12 also serves as an SOC measurement unit in the present embodiment. That is, the BCU 12 measures the state of charge (SOC) of the zinc battery 10. For example, the BCU 12 measures the SOC by measuring and integrating the current passed through the zinc battery 10. Information regarding the SOC measured by the BCU 12 is transmitted to the control unit 14 together with other data. Note that the BCU 12 may transmit information necessary for calculating the SOC (for example, open circuit voltage of the battery, discharge current amount and charge current amount, or integrated amount of discharge current and integrated amount of charge current) to the control unit 14, and the control unit 14 may calculate the SOC.

[0022] The State of Charge (SOC) can be measured, for example, as follows: First, the amount of current flowing into the zinc battery 10 during charging is obtained. Then, the charging capacity is calculated from this current. Next, the amount of current flowing from the zinc battery 10 during discharging is obtained. Then, the discharge capacity is calculated from this current. Based on these charging and discharging capacities, the SOC can be calculated.

[0023] The power converter 8 is a device that controls the charging and discharging of the zinc battery 10. The power converter 8 receives an instruction signal (data signal) from the control unit 14 and controls the charging and discharging of the zinc battery 10 based on that instruction signal. In particular, the control unit 14 in this embodiment controls the charging and discharging of the zinc battery 10 by controlling the operation of the power converter 8 based on the State of Charge (SOC) of the zinc battery 10 obtained from the BCU 12. In charging mode, the power converter 8 stores electricity flowing from the supply element 2 in the zinc battery 10, and in discharging mode, it forcibly discharges the zinc battery 10 and supplies power to the outside. The power converter 8 may be, for example, a DC / DC converter or an AC / DC converter.

[0024] The control unit 14 is a computer (e.g., a microcomputer) that controls the charging and discharging of the zinc battery 10. Figure 2 shows an example of the hardware configuration of the control unit 14. As shown in this figure, the control unit 14 has a processor 141, a memory 142, and a communication interface 143. The processor 141 is, for example, a CPU, and the memory 142 is, for example, flash memory, but the types of hardware devices that make up the control unit 14 are not limited to these and may be arbitrarily selected. Each function of the control unit 14 is realized by the processor 141 executing a program stored in the memory 142. For example, the processor 141 performs a predetermined operation on data read from the memory 142 or data received via the communication interface 143, and controls other devices by outputting the result of the operation to those devices. Alternatively, the processor 141 stores the received data or the result of the operation in the memory 142. The control unit 14 may consist of a single computer or a collection of multiple computers (i.e., a distributed system).

[0025] Here, the charge and discharge control by the control unit 14 will be explained in detail. Figure 3 is a graph showing an example of the change in the state of charge (SOC) of the zinc battery 10. As shown in Figure 3, the control unit 14 repeatedly performs a cycle that includes a charging operation of the zinc battery 10 (period P11) and a discharge operation of the zinc battery 10 after the charging operation (period P12). The charging and discharging operations may be continuous, or a pause may be provided between the charging and discharging operations. The period Ta of a cycle including one charging operation and one discharging operation may be a predetermined constant period, or it may differ from cycle to cycle.

[0026] The charging operation refers to the operation of the power converter 8 shown in Figure 1 to supply power from the wiring 6 to the zinc battery 10 and store charge in the zinc battery 10. The control unit 14 terminates the charging operation when the State of Charge (SOC) of the zinc battery 10 reaches a predetermined value. For example, the control unit 14 first supplies a constant current to the zinc battery 10, and switches to applying a constant voltage when the battery voltage of the zinc battery 10 reaches a predetermined voltage. Then, the control unit 14 terminates the charging operation when the current flowing through the zinc battery 10 drops to a value corresponding to the SOC set as the timing for terminating the charging operation. Alternatively, the control unit 14 may terminate the charging operation when the SOC of the zinc battery 10 reaches a predetermined value using a Coulomb counter that calculates the amount of charge or discharge of the zinc battery 10 by integrating the current flowing through the zinc battery 10 over time. Alternatively, the control unit 14 may supply a constant current to the zinc battery 10 and terminate the charging operation when the battery voltage of the zinc battery 10 rises to a voltage value corresponding to the State of Charge (SOC) set as the termination timing for the charging operation. In this case, the voltage value corresponding to the SOC set as the termination timing for the charging operation may be changed according to the ambient temperature or the battery temperature.

[0027] The discharge operation refers to the operation of the power converter 8 shown in Figure 1 to release charge from the zinc battery 10 and supply power from the zinc battery 10 to the wiring 6. The control unit 14 releases charge from the zinc battery 10 in accordance with the power consumption of the demand element 4. The control unit 14 terminates the discharge operation when the State of Charge (SOC) of the zinc battery 10 reaches a predetermined value. Alternatively, the control unit 14 may terminate the discharge operation when the battery voltage of the zinc battery 10 drops to a voltage value corresponding to the SOC set as the termination timing for the discharge operation. In this case, the voltage value corresponding to the SOC set as the termination timing for the discharge operation may be changed according to the ambient temperature or the battery temperature.

[0028] The State of Charge (SOC) of the zinc battery 10, which serves as the criterion for determining the timing of the end of the charging operation (hereinafter referred to as the SOC at the end of charging), is less than 100%. The SOC at the end of charging may be, for example, 95% or less, less than 80%, 60% or less, 40% or less, or 20% or less, but is not limited to these values. Figure 3 shows an example where the SOC at the end of charging is 95%.

[0029] Furthermore, the State of Charge (SOC) of the zinc battery 10, which serves as a criterion for determining the timing of the end of the discharge operation (hereinafter referred to as the SOC at the end of discharge), is less than 50%. The SOC at the end of discharge is, for example, 40% or less, 30% or less, 20% or less, or 10% or less, but is not limited to these values. Figure 3 shows an example where the SOC at the end of discharge is 40%. The discharge rate during the discharge operation (or the average discharge rate during the discharge period if the discharge rate is not constant) is most preferably 1C, followed by a range of 0.2C to 1C, and then a range of 0.2C to 5C.

[0030] The difference between the State of Charge (SOC) at the end of charging and the State of Charge (SOC) at the end of discharging, ΔSOC, is 95% or less. ΔSOC is, for example, 90% or less, less than 80%, or 60% or less, but is not limited to these values. Furthermore, ΔSOC is greater than 45%, greater than 50%, greater than 60%, or greater than 70%.

[0031] In this embodiment, the State of Charge (SOC) of the zinc battery 10 is the value obtained by setting the theoretical capacity of the Ni positive electrode active material to 100%. Specifically, when the charge rate is 0.2C and the charge voltage is 1.88V, the capacity at which the charge rate reaches 0.05C as the termination condition is defined as the capacity corresponding to 100% SOC.

[0032] At least one of the State of Charge (SOC) at the end of charging and the State of Charge (SOC) at the end of discharging may be changed according to the ambient temperature or battery temperature. For example, when the ambient temperature or battery temperature is higher than the reference temperature, the SOC at the end of charging may be set lower than the reference value, and when the ambient temperature or battery temperature is lower than the reference temperature, the SOC at the end of charging may be set higher than the reference value.

[0033] If the charging operation is performed for a fixed period of time, the State of Charge (SOC) at the end of charging depends on the SOC at the start of charging, the charging voltage (constant voltage), and the charging time. The length of the period from the start to the end of charging and the charging voltage should be determined so that the SOC at the end of charging is less than 100%.

[0034] Here, a method for controlling the zinc battery 10 using the power supply system 1 will be described. Figure 4 is a flowchart of the control method for the zinc battery 10 in this embodiment. In this control method, a charging step S1 for charging the zinc battery 10 and a discharging step S2 for discharging the zinc battery 10 are performed alternately and repeatedly. The repetition period of the charging step S1 and the discharging step S2 may be indeterminate, and the end timing of the charging step S1 and the end timing of the discharging step S2 are determined based on the size of the State of Charge (SOC) of the zinc battery 10. In that case, as mentioned above, the SOC of the zinc battery 10 that serves as the criterion for determining the end timing of the charging step S1 (SOC at the end of charging) is less than 100%. The SOC at the end of charging is, for example, 95% or less, less than 80%, 60% or less, 40% or less, or 20% or less, but is not limited to these values. Also, the SOC of the zinc battery 10 that serves as the criterion for determining the end timing of the discharging step S2 (SOC at the end of discharging) is less than 50%. The State of Charge (SOC) at the end of discharge may be, for example, 40% or less, 30% or less, 20% or less, or 10% or less, but is not limited to these values.

[0035] The effects obtained by the control method and power supply system 1 of the zinc battery 10 described above will now be explained. In this embodiment, the State of Charge (SOC) at the end of charging is less than 100%, and the State of Charge (SOC) at the end of discharging is less than 50%. Through considerations based on cycle tests conducted by the inventors, it has become clear that the cycle life of the zinc battery 10 is significantly extended when the SOC at the end of charging and the SOC at the end of discharging satisfy these conditions. Therefore, the control method and power supply system 1 of this embodiment can effectively extend the life of the zinc battery 10.

[0036] As mentioned above, the State of Charge (SOC) at the end of charging may be 95% or less, or even less than 80%. The SOC at the end of discharging may also be 30% or less. Furthermore, the difference between the SOC at the end of charging and the SOC at the end of discharging may be 95% or less, or greater than 45%. Based on our observations through cycle tests, the cycle life of the zinc battery can be further extended when the SOC at the end of charging and / or the SOC at the end of discharging meet either of the above conditions. (Examples)

[0037] The inventors conducted a cycle test using a nickel-zinc battery. The procedure was as follows. In the following description, "C" relatively represents the magnitude of the current when discharging from a fully charged state to the rated capacity at a constant current, and means "discharge current value (A) / battery capacity (Ah)". For example, the current that can discharge the rated capacity in 1 hour is defined as "1C", and the current that can discharge in 2 hours is defined as "0.5C".

[0038] First, as an initial capacity verification test, the nickel-zinc battery was charged at a constant voltage of 1.88V at an ambient temperature of 25°C until the current value decreased to 0.05C, and then discharged at a constant current of 0.33C until the battery voltage reached 1.1V. Hereafter, the discharge capacity measured by this initial capacity verification test was used as the standard for 100% State of Charge (SOC).

[0039] Next, multiple cycle tests were conducted, each involving a cycle of constant-voltage charging (charging voltage 1.88V) and constant-current discharging. During these tests, the State of Charge (SOC) at the end of charging and the State of Charge (SOC) at the end of discharging were set to various values ​​for each cycle test. In the charging operation where the SOC at the end of charging was set to 100%, the nickel-zinc battery was charged at a constant voltage until the current decreased to 0.05C. Under conditions where the SOC at the end of charging was a value other than 100%, the nickel-zinc battery was charged until it reached a discharge capacity equivalent to the set ΔSOC, or until the current decreased to 0.05C. Furthermore, in the charging operation where the SOC at the end of discharging was set to 0%, the nickel-zinc battery was discharged at a constant current until the battery voltage reached 1.1V. Under conditions where the SOC at the end of discharging was a value other than 0%, the nickel-zinc battery was discharged at a constant current until it reached a discharge capacity equivalent to the set ΔSOC, or until the battery voltage reached 1.1V. During the cycle test, a capacity verification test was performed every 25 cycles under the same conditions as the initial capacity verification test, and the cycle life was defined as the number of cycles at which the discharge capacity retention rate decreased to 70%.

[0040] Figures 5 and 6 are charts showing the results of cycle tests. Figure 5 shows the results of 3 cycle tests as a comparative example and the results of 23 cycle tests as an example. Figure 6 shows the results of 24 cycle tests as an example. In these figures, the upper limit SOC represents the SOC at the end of charging, the lower limit SOC represents the SOC at the end of discharging, and ΔSOC represents the difference between the SOC at the end of charging and the SOC at the end of discharging. The discharge rate is the discharge current per 5 hours of discharge operation (constant current discharge at 0.2C).

[0041] As shown in the comparative example in Figure 5, when the upper limit of SOC was set to 100%, the cycle life of the nickel-zinc battery was a low value of 100 to 150 cycles. In contrast, as shown in the examples in Figures 5 and 6, when the upper limit of SOC was set to less than 100% (specifically 95% or less), the cycle life of the nickel-zinc battery was a high value of 150 to 650 cycles, confirming the extended lifespan of the nickel-zinc battery. Furthermore, in the examples, when the upper limit of SOC was set to 80% or less, 60% or less, 40% or less, or 20% or less, the cycle life of the nickel-zinc battery was 200 cycles or more, 275 cycles or more, 350 cycles or more, or 600 cycles or more, respectively, confirming even further extended lifespan of the nickel-zinc battery.

[0042] Furthermore, as shown in Figure 5, when ΔSOC was set to 100%, the cycle life of the nickel-zinc battery was a low value of 100 to 125 cycles. In contrast, as shown in Figures 5 and 6, when ΔSOC was set to 95% or less, the cycle life of the nickel-zinc battery was a high value of 150 to 650 cycles, confirming the extended lifespan of the nickel-zinc battery. In addition, in the examples, when ΔSOC was set to 80% or less or 60% or less, the cycle life of the nickel-zinc battery was 150 cycles or more or 200 cycles or more, respectively, confirming further extended lifespan of the nickel-zinc battery.

[0043] Furthermore, as shown in Figures 5 and 6, when the upper and lower SOC limits were kept the same and only the discharge rate was varied, the cycle life was longest when the discharge rate was 1C, the second longest when the discharge rate was 0.2C, and the shortest when the discharge rate was 10C. Therefore, it can be said that the discharge rate of 1C is most preferable, followed by the range of 0.2C to 1C, and then the range of 0.2C to 5C.

[0044] Furthermore, the inventors discovered the following facts through the above cycle test: In capacity verification tests performed at predetermined cycle intervals (for example, every 25 cycles in the above cycle test), when battery capacity and Coulomb efficiency were checked, there was little decrease in battery capacity and almost no decrease in Coulomb efficiency. Therefore, it was found that the main cause of the decrease in discharge capacity retention rate in the above cycle test was insufficient charging.

[0045] In the cycle test described above, the charging voltage for constant voltage charging was set to 1.88V, and the charging operation was terminated when the current value decreased to 0.05C. However, if the charging voltage is set to a relatively low voltage such as 1.88V or 1.86V, it becomes possible to charge an amount of electricity close to the capacity corresponding to the discharge capacity retention rate by setting the charging termination condition to a low value such as 0.01C.

[0046] The zinc battery control method and power supply system according to the present invention are not limited to the embodiments described above, but are shown in the claims and are intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of Symbols]

[0047] 1...Power system, 2...Supply element, 4...Demand element, 6...Wiring, 7...DC wiring, 8...Power converter, 10...Zinc battery, 12...Battery control unit (BCU), 14...Control unit, 141...Processor, 142...Memory, 143...Communication interface, S1...Charging step, S2...Discharging step, Ta...Cycle.

Claims

1. The cycle of charging the zinc battery and discharging the zinc battery after charging is repeated. Based on the size of the SOC of the zinc battery, the timing of the end of charging and the timing of the end of discharging in each cycle are determined. The SOC of the zinc battery, which serves as the criterion for determining the timing of the end of the charging, is less than 100%. A method for controlling a zinc battery, wherein the State of Charge (SOC) of the zinc battery, which serves as a criterion for determining the timing of the termination of the discharge, is less than 50%.

2. The zinc battery control method according to claim 1, wherein the SOC of the zinc battery, which serves as a criterion for determining the timing of the end of charging, is 95% or less.

3. The zinc battery control method according to claim 1, wherein the SOC of the zinc battery, which serves as a criterion for determining the timing of the end of charging, is less than 80%.

4. The method for controlling a zinc battery according to claim 1, wherein the difference between the SOC of the zinc battery used as a criterion for determining the timing of the end of charging and the SOC of the zinc battery used as a criterion for determining the timing of the end of discharging is 95% or less.

5. A method for controlling a zinc battery according to any one of claims 1 to 4, wherein the difference between the SOC of the zinc battery used as a criterion for determining the timing of the end of charging and the SOC of the zinc battery used as a criterion for determining the timing of the end of discharging is greater than 45%.

6. Zinc batteries and A control unit for controlling the charging and discharging of the zinc battery, Equipped with, The control unit repeatedly performs a cycle including charging the zinc battery and discharging the zinc battery after charging. The control unit determines the timing for ending the charge and the timing for ending the discharge in each cycle based on the size of the SOC of the zinc battery. The SOC of the zinc battery, which serves as the criterion for determining the timing of the end of the charging, is less than 100%. A power supply system in which the State of Charge (SOC) of the zinc battery, which serves as a criterion for determining the timing of the termination of the discharge, is less than 50%.

7. The power supply system according to claim 6, wherein the SOC of the zinc battery, which serves as a criterion for determining the timing of the end of charging, is 95% or less.

8. The power supply system according to claim 6, wherein the SOC of the zinc battery, which serves as a criterion for determining the timing of the end of charging, is less than 80%.

9. The power supply system according to claim 6, wherein the difference between the SOC of the zinc battery used as a criterion for determining the timing of the end of charging and the SOC of the zinc battery used as a criterion for determining the timing of the end of discharging is 95% or less.

10. The power supply system according to any one of claims 6 to 9, wherein the difference between the SOC of the zinc battery used as a criterion for determining the timing of the end of charging and the SOC of the zinc battery used as a criterion for determining the timing of the end of discharging is greater than 45%.

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