Internal short circuit detection method and power supply system

Abstract

To reliably detect an internal short-circuit in a battery pack including zinc batteries.SOLUTION: An internal short-circuit detection method of an embodiment is a method for detecting the presence or absence of internal short-circuit of a battery 5 including zinc batteries, and includes: a charging step of controlling charging of the battery 5; a first discharge step of controlling to discharge the battery 5 until the batter enters a predetermined charged state; a suspension step of leaving the battery 5 in a state where both ends of the battery are opened for a predetermined time; a second discharge step of controlling to discharge the battery 5 at a predetermined current value for an approximately predetermined time; and a measuring step of measuring the pole-to-pole voltage of the battery 5 in the second discharge step and determining the presence or absence of internal short-circuit based on a temporal change in the pole-to-pole voltage.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for detecting an internal short circuit in a battery pack including zinc batteries and a power supply system. [Background technology]

[0002] Patent Document 1 discloses a device for detecting the internal state of a secondary battery such as a lithium-ion battery. The device disclosed in this document measures the voltage value or the voltage value and current value of the secondary battery, and compares the measurement result with basic data to detect the internal state of the secondary battery, such as a short circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-50410 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional technology, when a battery pack consisting of multiple secondary batteries connected in series is targeted, it is difficult to reliably detect an internal short circuit in the secondary battery because the voltage of the battery pack is measured. In particular, since the voltage fluctuation due to changes in the state of charge of a zinc battery is relatively small, it is difficult to detect an internal short circuit in a zinc battery using the above-mentioned conventional technology.

[0005] It is therefore an object of the present invention to provide an internal short circuit detection method and a power supply system that can reliably detect an internal short circuit in a battery pack including zinc batteries. [Means for solving the problem]

[0006] An internal short circuit detection method according to one aspect of an embodiment is a method for detecting the presence or absence of an internal short circuit in a battery pack including zinc batteries, and includes a charging step of controlling charging of the battery pack, a first discharging step of controlling the battery pack to discharge until it reaches a predetermined charged state, a resting step of leaving the battery pack with both ends open for a predetermined time, a second discharging step of controlling the battery pack to discharge at a predetermined current value for about a predetermined time, and a measurement step of measuring the voltage between the electrodes of the battery pack in the second discharging step and determining the presence or absence of an internal short circuit based on the change over time in the voltage between the electrodes.

[0007] A power supply system according to one aspect of an embodiment includes a battery pack including a zinc battery, a control unit that controls charging and discharging of the battery pack, and a detection unit that detects the state of the zinc battery. After charging the battery pack, the control unit controls the battery pack to be discharged until it reaches a predetermined charged state, and then controls the battery pack to be left for a predetermined time with both ends open, and then to be discharged at a predetermined current value for about a predetermined time. The detection unit measures the inter-electrode voltage of the battery pack during discharging at the predetermined current value, and determines the presence or absence of an internal short circuit based on the change over time in the inter-electrode voltage.

[0008] In these internal short circuit detection methods and power supply systems, the battery pack is set to a predetermined charge state and then left for a predetermined time, after which the battery pack is discharged at a predetermined current value for about a predetermined time. Furthermore, the presence or absence of an internal short circuit in the battery pack is determined by detecting a temporal change in the voltage between the electrodes of the battery pack during discharge at the predetermined current value. This makes it possible to detect a state in which the charge amount of only the zinc battery with an internal short circuit is rapidly decreasing, so that it is possible to reliably determine the presence or absence of an internal short circuit in the zinc batteries in the battery pack.

[0009] Here, in the measurement step, it may be determined that there is an internal short circuit when the step-like time change is equal to or greater than a predetermined voltage value. In general, the relationship between the state of charge and the voltage between the electrodes of a zinc battery has a wide flat region in which the voltage between the electrodes changes little with respect to the state of charge. In the case of a battery pack including a zinc battery having such characteristics, the presence or absence of an internal short circuit in the zinc battery in the battery pack can be detected more reliably.

[0010] In addition, in the measurement step, the value of the time change and a predetermined voltage value may be compared to determine the number of zinc batteries that have an internal short circuit in the battery pack. In this case, in addition to the presence or absence of an internal short circuit in the battery pack, the number of zinc batteries that have an internal short circuit can be accurately determined.

[0011] The predetermined charging state may be a state where the ratio of the charging charge to the discharge capacity reaches a predetermined value. In this case, the predetermined value is set to correspond to a charging state where the voltage between the electrodes of the zinc battery is likely to change, so that the presence or absence of an internal short circuit in the battery pack can be determined more reliably.

[0012] In the first discharging step, a predetermined state of charge may be detected based on an open circuit voltage of the battery pack. In this case, the state of charge of the battery pack can be easily detected, and the presence or absence of an internal short circuit of the battery pack can be easily detected.

[0013] In the first discharging step, the predetermined state of charge may be detected based on an integrated value of the discharge current of the battery pack. In this case as well, the state of charge of the battery pack can be detected easily and with high accuracy. Effect of the Invention

[0014] According to one aspect of the embodiment, it is possible to provide an internal short circuit detection method and a power supply system that can reliably detect an internal short circuit in a battery pack including zinc batteries. [Brief description of the drawings]

[0015] [Figure 1]1 is a diagram illustrating an example of the configuration of a power supply system 1. FIG. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device 8. [Diagram 3] 2 is a graph showing an example of the relationship between the charging rate and the open circuit voltage when a cell constituting the battery 5 is discharged. [Figure 4] 4 is a graph showing the change over time of the discharge current controlled by the control device 8. [Diagram 5] 4 is a flowchart showing the procedure of a state detection process executed by the power supply system 1. [Figure 6] 11 is a graph showing the time change in the inter-electrode voltage of a battery 5 analyzed by a control device 8 when a state detection process is performed. [Figure 7] 5 is a graph showing the time change in the inter-electrode voltage of a battery 5 when a cycle of charge / discharge control in accordance with the time change shown in FIG. 4 is repeatedly executed. [Figure 8] 5 is a graph showing the time change in the inter-electrode voltage of a battery 5 when charging and discharging are stopped after repeatedly executing cycles of charge and discharge control in accordance with the time change shown in FIG. 4 for the battery 5. [Figure 9] 9 is a graph showing the voltage drop after 40 hours of rest corresponding to each number of cycles in the measurement results of FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiment of the zinc battery internal short circuit detection method and power supply system according to the present invention will be described in detail with reference to the attached drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. In the following description, the zinc battery is a concept of a battery that uses zinc in the negative electrode, such as a nickel-zinc battery, an air-zinc battery, and a silver-zinc battery. A nickel-zinc battery is adopted as the zinc battery in this embodiment.

[0017] FIG. 1 is a diagram showing a schematic diagram of an example of a power supply system 1 and its peripheral configuration. The power supply system 1 monitors the internal short-circuit state of the storage battery while controlling the charging and discharging of the storage battery, and notifies the user of the monitoring result. The application of the power supply system 1 is not limited, and for example, the power supply system 1 can be applied to both fixed objects and mobile objects. As an example of application to a fixed object, the power supply system 1 can be used as a UPS in various places such as homes, offices, factories, and farms. As an object to be controlled for charging and discharging by the power supply system 1, a battery pack in which a plurality of single zinc battery cells are connected in series is preferably used. In FIG. 1, electrical connection paths are indicated by solid lines without arrows, and transmission paths of detection signals and control signals are indicated by solid lines with arrows.

[0018] The power supply system 1 includes a voltage detection circuit 2, a temperature detection circuit 3, a current detection circuit 4, a battery 5 which is a battery pack, a charge control circuit 6, a discharge control circuit 7, and a control device 8. The voltage detection circuit 2, the temperature detection circuit 3, the current detection circuit 4, and the control device 8 constitute a detection unit that detects the state of the battery 5, and the charge control circuit 6, the discharge control circuit 7, and the control device 8 constitute a control unit that controls the charging and discharging (charging and discharging) of the battery 5.

[0019] Battery 5 is a device that converts the power provided from charge control circuit 6 into chemical energy and stores it, and is capable of charging and discharging. Battery 5 is configured to include multiple cells (zinc batteries) connected in series. Battery 5 is configured by storing multiple cells in a single housing.

[0020] The voltage detection circuit 2 is a sensor unit that senses (measures) the voltage (potential difference) between the two poles of the battery 5. The voltage detection circuit 2 is connected to the positive and negative poles of the battery 5 so as to sense the voltage between the two poles of the battery 5, which includes a plurality of cells connected in series with each other. In this way, the voltage detection circuit 2 senses the total voltage between the two poles of the plurality of cells included in the battery 5. The voltage detection circuit 2 is connected to the control device 8 so as to be able to output a detection signal (e.g., a voltage signal) indicating the value of the sensed voltage to the control device 8.

[0021] The temperature detection circuit 3 is a sensor unit that senses (measures) the temperature around the battery 5. The temperature detection circuit 3 is provided, for example, on the side of the housing of the battery 5, and senses the temperature around the battery 5. This temperature detection circuit 3 may be provided around any one of the multiple cells included in the battery 5, or multiple temperature detection circuits 3 may be provided around the multiple cells. In addition, the temperature detection circuit 3 may be provided away from the housing of the battery 5 as long as it can sense the temperature around the battery 5. The temperature detection circuit 3 is connected to the control device 8 so as to be able to output a detection signal (for example, a voltage signal) indicating the value of the sensed ambient temperature to the control device 8.

[0022] The current detection circuit 4 is a sensor unit that senses (measures) the charging current supplied to the battery 5 or the discharging current output from the battery 5. The current detection circuit 4 is, for example, an ammeter electrically connected between both electrodes of the battery 5. This current detection circuit 4 only needs to be able to sense the charging current or discharging current supplied to the entire battery 5, and may be provided connected to both electrodes of any one of the multiple cells that make up the battery 5, or may be provided connected to both electrodes of the battery 5. The current detection circuit 4 is connected to the control device 8 so as to be able to output a detection signal (for example, a voltage signal) indicating the value of the sensed current to the control device 8.

[0023] The charge control circuit 6 is a circuit unit that supplies a charging current to the battery 5. The charge control circuit 6 is connected to the control device 8 so as to be able to charge the battery 5 at a constant voltage in response to a control signal (e.g., a voltage signal) received from the control device 8. The discharge control circuit 7 is a circuit unit that variably controls the discharge current output from the battery 5. The discharge control circuit 7 is connected to the control device 8 so as to be able to set the magnitude of the discharge current output from the battery 5 in response to a control signal (e.g., a voltage signal) received from the control device 8. The charge control circuit 6 and the discharge control circuit 7 are also configured so as to be able to open the two electrodes of the battery 5 by setting a high resistance between the two electrodes of the battery 5 in response to a control signal from the control device 8.

[0024] The control device 8 is a computer (e.g., a microcomputer) that controls charging and discharging of the battery 5 and detects whether or not there is an internal short circuit in the battery 5. FIG. 2 is a diagram showing an example of the hardware configuration of the control device 8. As shown in this diagram, the control device 8 has a processor 11, a memory 12, a communication interface 13, and an output interface 14. The processor 11 is, for example, a CPU, and the memory 12 is, for example, a flash memory, but the types of hardware devices that configure the control device 8 are not limited to these and may be selected arbitrarily. Each function of the control device 8 is realized by the processor 11 executing a program stored in the memory 12. For example, the processor 11 performs a predetermined calculation on data read from the memory 12 or data based on a detection signal received via the communication interface 13, and outputs the calculation result to another device via the communication interface 13 and the output interface 14, thereby controlling the other device. For example, the other device may be a charge control circuit 6, a discharge control circuit 7, a display, a speaker, a lamp, a vibrator, an alarm device, etc. Alternatively, the processor 11 stores the received data or the calculation result in the memory 12. The control device 8 may be configured as one computer, or may be configured as a collection of multiple computers (that is, a distributed system).

[0025] During normal times when the power of the battery 5 is not required, the power supply system 1, such as a UPS, maintains the charged state of the battery 5 and waits until a power outage occurs (standby state). At that time, the control device 8 controls the charging control circuit 6 to control charging so as to maintain the charged state of the battery 5 (charging step). The control device 8 also starts a state detection process that detects the presence or absence of an internal short circuit in the battery 5 at any timing during the standby state (for example, at a preset timing or at a timing when a command is input to the control device 8 via the communication interface 13). The principle and processing procedure of the state detection process will be described in detail below.

[0026] FIG. 3 is a graph showing an example of the relationship between the state of charge (SOC), which is the ratio of the charge amount to the discharge capacity, and the open circuit voltage (OCV) during discharge of a cell constituting the battery 5. As shown in this graph, in a zinc battery cell, the characteristic of the change in OCV with respect to SOC has a wide flat region, so that the presence or absence of an internal short circuit cannot be accurately determined by the method of determining the decrease in OCV during rest when neither discharging nor charging is performed as described in JP 2002-50410 A. In addition, since the battery 5 includes a plurality of cells connected in series, the presence or absence of an internal short circuit cannot be accurately determined by the change in the voltage between the two electrodes of the battery 5. On the other hand, the present inventors have found a phenomenon in which, in a cell in which an internal short circuit has occurred, when the SOC has decreased to less than about 30%, the voltage between the two electrodes decreases rapidly during discharge, and have devised a method of detecting the presence or absence of an internal short circuit by utilizing this phenomenon.

[0027] That is, the control device 8 has a function of executing a state detection process in the following procedure.

[0028] First, when the state detection process is started, the control device 8 controls the discharge control circuit 7 so as to discharge the battery 5 at a predetermined discharge current (for example, a constant discharge current between "0.2C" and "1C") until a predetermined state of charge (SOC) is reached. The discharge current "0.2C" here is a current value at which the design value of the discharge capacity of the battery 5 when fully charged is completely discharged in 5 hours, and the discharge capacity "1C" is a current value at which the design value is completely discharged in 1 hour. At this time, the control device 8 specifies the SOC of the battery 5 each time based on the OCV of the battery 5 detected by the voltage detection circuit 2, and controls the battery 5 to discharge until the SOC reaches, for example, 30%. The control device 8 may also specify the SOC at the start of discharge based on the OCV of the battery 5, specify the amount of discharged charge thereafter by integrating the discharge current sensed by the current detection circuit 4, and specify the SOC of the battery 5 each time based on the SOC at the start of discharge and the specified discharge current.

[0029] Next, the control device 8 controls the charge control circuit 6 and the discharge control circuit 7 to leave the battery 5 open (maintained in a high resistance state) for a predetermined time. The predetermined time can be set to any time equal to or greater than 1 second, but is set to, for example, 1 hour to 24 hours. Preferably, the predetermined time is set to the time required for the SOC of the battery 5 to decrease from 30% to approximately 20% due to natural discharge.

[0030] Thereafter, the control device 8 controls the discharge control circuit 7 to discharge the battery 5 at a predetermined discharge current (for example, a constant discharge current between 0.2C and 1C) for a predetermined time (for example, 60 seconds). At the same time, the control device 8 analyzes the temporal change in the inter-electrode voltage of the battery 5 detected by the voltage detection circuit 2, and determines the presence or absence of an internal short circuit in the cells of the battery 5 based on the change.

[0031] 4 is a graph showing the time change in the discharge current controlled by the control device 8 at this time. In the example shown in this graph, the discharge control circuit 7 controls the battery 5 to be discharged with a discharge current of 77.8 A corresponding to "0.97 C (≒ 1 C)" for 59 seconds, and then the discharge control circuit 7 controls the battery 5 to be discharged with a discharge current of 300 A for 1 second, and then the charge control circuit 6 controls the battery 5 to be charged (constant voltage charging) with a maximum charge current of 100 A at a constant voltage of 14.8 V. However, the control to charge the battery 5 at a constant voltage may be omitted.

[0032] The control device 8 detects the width of the step-like voltage change in the time change of the voltage between the electrodes of the battery 5 during the above 59 seconds, and compares the width with a predetermined voltage value (e.g., 1.5 V) to determine the presence or absence of an internal short circuit. Specifically, if the width of the voltage change exceeds the predetermined voltage value, it is determined that there is an "internal short circuit." The control device 8 can also determine the number of cells in the battery 5 that have an internal short circuit by comparing the width of the step-like voltage change with a voltage value that is an integer multiple of the predetermined voltage value. Specifically, if the width of the voltage change is greater than a voltage value that is n times (n is an integer) the predetermined voltage value and smaller than a voltage value that is n+1 times the predetermined voltage value, it determines that the number of cells in the battery 5 that have an internal short circuit is "n."

[0033] Then, the control device 8 outputs the result of the determination to other devices such as a display, a speaker, a lamp, a vibrator, an alarm device, etc. via the communication interface 13 and the output interface 14. For example, the control device 8 outputs a message indicating the presence or absence of an internal short circuit and the number of cells in which an internal short circuit has occurred to the display and the speaker.

[0034] The following describes the procedure of the state detection process executed by the above-mentioned power supply system 1, and the internal short-circuit detection method according to this embodiment. Fig. 5 is a flowchart showing the procedure of the state detection process executed by the power supply system 1.

[0035] First, when the state detection process is started in the standby state of the battery 5, the control device 8 controls the discharge control circuit 7 to start discharging the battery 5 at a predetermined discharge current (step S1, start of the first discharge step). After that, the control device 8 controls the discharge control circuit 7 to stop discharging at the predetermined discharge current when the SOC of the battery 5 reaches a predetermined value (step S2, end of the first discharge step).

[0036] Next, the control device 8 controls the charge control circuit 6 and the discharge control circuit 7 to suspend charging and discharging of the battery 5 for a predetermined time with both ends of the battery 5 disconnected from the load (step S3, suspend step). Furthermore, the control device 8 controls the discharge control circuit 7 to discharge the battery 5 at a predetermined discharge current for a predetermined time. At the same time, the control device 8 analyzes the change over time in the inter-electrode voltage of the battery 5 detected by the voltage detection circuit 2 (step S4, second discharge step and measurement step).

[0037] In the above analysis, the control device 8 compares the amplitude of step-like voltage change in the temporal change in the voltage between the electrodes of the battery 5 with a predetermined voltage value (step S5, measurement step). If the comparison shows that the amplitude of the voltage change exceeds the predetermined voltage value (step S5; Yes), the control device 8 determines that the battery 5 has an "internal short circuit," and further compares the amplitude of the voltage change with a voltage value that is an integer multiple of the predetermined voltage value to identify the number of cells in which an internal short circuit has occurred (step S6, measurement step). On the other hand, if the comparison in step S5 shows that the amplitude of the voltage change is equal to or less than the predetermined voltage value (step S5; No), the control device 8 determines that the battery 5 has no "internal short circuit."

[0038] Finally, the control device 8 outputs a message, an alarm, or the like based on the determination result regarding the internal short circuit to other devices (step S7). With the above, the state detection process is completed.

[0039] FIG. 6 is a graph showing the time change of the inter-electrode voltage of the battery 5 analyzed by the control device 8 when the state detection process is performed on the battery 5 including eight cells. Here, the analysis results are shown when the state detection process is performed after a predetermined number of cycles (1, 3601, 36001, ...) of 120-second cycles in which the charge / discharge control is performed according to the time change shown in FIG. 4 is repeated during standby of the battery 5. As shown in the analysis results, when the number of cycles of the charge / discharge control is relatively small (36001 or less), no step-like voltage change is observed in the discharge process from 0 to 59 seconds. On the other hand, when the number of cycles of the charge / discharge control is relatively large (39601 or more), a large step-like voltage change is observed in the discharge process from 0 to 59 seconds. This is considered to be due to the occurrence of an internal short circuit in the cell due to 39601 or more cycles of the charge / discharge control. According to the control device 8 of this embodiment, the presence or absence of an internal short circuit in the cell in the battery 5 can be determined by detecting a step-like voltage drop in the above-mentioned discharge process.

[0040] FIG. 7 is a graph showing the time change of the inter-electrode voltage of the battery 5 when the charge / discharge control cycle according to the time change shown in FIG. 4 is repeatedly performed on the battery 5 including eight cells after the standby state. Here, the inter-electrode voltage during 300A discharge at 60 seconds in each cycle is shown. As shown in the results, it was found that a voltage drop was observed in the inter-electrode voltage after the 39600th cycle, and the voltage drop was repeatedly observed in the following 3 to 5 cycles, after which the voltage drop temporarily recovered. This result indicates that the control device 8 may be able to determine the presence or absence of an internal short circuit in the battery 5 by analyzing the inter-electrode voltage during the 300A discharge control for 1 second in the state detection process.

[0041] In the power supply system 1 according to the present embodiment described above, the battery 5 is set to a predetermined charge state and then left for a predetermined time, after which the battery 5 is discharged at a predetermined current value for about a predetermined time. Furthermore, the presence or absence of an internal short circuit in the battery 5 is determined by detecting a temporal change in the voltage between the electrodes of the battery 5 during discharge at the predetermined current value. This makes it possible to detect a state in which the charge amount of only a cell with an internal short circuit drops rapidly, and therefore makes it possible to reliably determine the presence or absence of an internal short circuit in the cells of the battery 5.

[0042] Here, the control device 8 judges that there is an internal short circuit when the change in the voltage between the electrodes of the battery 5 during discharge at a predetermined current value is equal to or greater than a predetermined voltage value. In general, the relationship between SOC and OCV in a zinc battery has a wide flat region in which the OCV changes little with respect to SOC. According to this embodiment, when the battery 5 includes a zinc battery having such properties as a cell, the presence or absence of an internal short circuit in the cell of the battery 5 can be detected more reliably.

[0043] Furthermore, the control device 8 compares the variation in the inter-electrode voltage of the battery 5 during discharge at a predetermined current value with a predetermined voltage value to determine the number of cells in the battery 5 that have an internal short circuit. In this case, in addition to determining whether or not there is an internal short circuit in the battery 5, the number of cells that have an internal short circuit can be determined with high accuracy.

[0044] Furthermore, the control device 8 sets the timing for stopping the initial discharge control in the state detection process to the state where the SOC reaches a predetermined value. In this case, by setting the predetermined value to correspond to the SOC at which the cell electrode-to-electrode voltage is likely to change, the presence or absence of an internal short circuit in the battery 5 can be determined more reliably.

[0045] Furthermore, the control device 8 detects whether or not the SOC has reached a predetermined value based on the OCV of the battery 5. In this case, the SOC of the battery 5 can be easily detected, and the presence or absence of an internal short circuit in the battery 5 can be easily detected.

[0046] Furthermore, the control device 8 detects whether or not the SOC has reached a predetermined value based on the integrated value of the discharge current of the battery 5. In this case as well, the SOC of the battery 5 can be detected easily and with high accuracy.

[0047] FIG. 8 is a graph showing the time change of the inter-electrode voltage of the battery 5 when the charge / discharge control cycle according to the time change shown in FIG. 4 is repeatedly performed on the battery 5 and then the charge / discharge control is suspended. FIG. 9 is a graph showing the voltage drop after 40 hours of suspension corresponding to each number of cycles in the measurement results of FIG. 8. As shown in the measurement results, the voltage drop during suspension of the battery 5 increases almost in proportion to the number of cycles of the charge / discharge control. Therefore, it is not possible to stably determine whether or not an internal short circuit has occurred by analyzing the voltage change during suspension. In contrast, according to the present embodiment, the presence or absence of an internal short circuit can be accurately determined by analyzing the time change of the voltage during discharge control at a predetermined current value in the state detection process.

[0048] The internal short circuit detection method and power supply system according to the present invention are not limited to the above-described exemplary embodiments, but are defined by the claims, and are intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0049] 1...power supply system, 2...voltage detection circuit (detection unit), 3...temperature detection circuit (detection unit), 4...current detection circuit (detection unit), 5...battery (battery pack), 6...charge control circuit (control unit), 7...discharge control circuit (control unit), 8...control device (control unit, detection unit).

Claims

1. A method for detecting the presence or absence of an internal short circuit in a battery pack including a zinc battery, comprising: a charging step of controlling charging of the battery pack; a first discharging step of controlling the battery pack to be discharged until a predetermined state of charge (SOC) that is a ratio of a charging charge amount to a discharging capacity is lower than 30%; a resting step of leaving the battery pack for a predetermined period of time with both ends open; a second discharging step of controlling the battery pack so as to discharge the battery pack at a predetermined current value for a predetermined period of time; a measuring step of measuring a voltage between both electrodes of the battery pack in the second discharging step and determining whether or not there is an internal short circuit based on a change over time in the voltage between both electrodes; An internal short circuit detection method comprising:

2. In the measuring step, it is determined that there is an internal short circuit when the step-like temporal change is equal to or greater than a predetermined voltage value. The method for detecting an internal short circuit according to claim 1 .

3. In the measuring step, the value of the time change is compared with a predetermined voltage value to determine the number of the zinc batteries having an internal short circuit in the battery pack. The method for detecting an internal short circuit according to claim 1 or 2.

4. The predetermined charge state is a state in which the ratio of the charge charge amount to the discharge capacity reaches a predetermined value. The method for detecting an internal short circuit according to any one of claims 1 to 3.

5. In the first discharging step, the predetermined state of charge is detected based on an open circuit voltage of the battery pack. The method for detecting an internal short circuit according to claim 4.

6. the first discharging step detects the predetermined state of charge based on an integrated value of a discharging current of the battery pack; The method for detecting an internal short circuit according to claim 4 or 5.

7. A battery pack including a zinc battery; A control unit that controls charging and discharging of the battery pack; A detection unit that detects the state of the zinc battery; Equipped with The control unit is After charging the battery pack, the battery pack is controlled to be discharged until a predetermined state of charge (SOC) that is a ratio of a charging charge amount to a discharge capacity is lower than 30%. The battery pack is left for a predetermined period of time with both ends open. Thereafter, the battery pack is controlled so as to be discharged at a predetermined current value for a predetermined period of time; The detection unit is measuring a voltage between both electrodes of the battery pack during discharge at the predetermined current value, and determining whether or not there is an internal short circuit based on a change in the voltage between both electrodes over time; Power supply system.

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