Internal short-circuit detection apparatus, electricity storage device, internal short-circuit detection method, and program

Abstract

To provide an internal short circuit detection apparatus, an electricity storage device, an internal short circuit detection method, and a program that are capable of quickly detecting an internal short circuit in a secondary battery.SOLUTION: An internal short-circuit detection device includes a current acquisition unit that acquires a charging current for each of a plurality of secondary batteries that are charged by constant-current constant-voltage charging, a charging control unit that individually charges the plurality of secondary batteries for a predetermined period of time when the charging current to the plurality of secondary batteries decreases, and a short-circuit detection unit that detects an internal short circuit in the secondary batteries on the basis of the charging current of each secondary battery during individual charging.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an internal short - circuit detection device for detecting an internal short - circuit of a secondary battery, a power storage device, an internal short - circuit detection method, and a program.

Background Art

[0002] Conventionally, in secondary batteries such as nickel - zinc batteries, it is known that during charging, metallic zinc is deposited from the negative electrode, zinc dendrites are formed that penetrate the separator and reach the positive electrode, and an internal short - circuit occurs. In a secondary battery in which an internal short - circuit has occurred, since the self - discharge amount during discharge increases, the amount of decrease in the battery current becomes faster compared to a normal secondary battery, and the life of the secondary battery is shortened. Therefore, in a secondary battery, an internal short - circuit detection process for detecting an internal short - circuit is performed (see, for example, Patent Document 1).

[0003] In such an internal short - circuit detection process, for example, attention is paid to the difference in the amount of decrease in the battery voltage during self - discharge between a normal secondary battery and a secondary battery with an internal short - circuit, and based on the difference in the battery voltage at the time when a predetermined time has elapsed, the internal short - circuit of the secondary battery is detected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the temporal change amount of the battery voltage during self - discharge of a secondary battery in which an internal short - circuit has occurred is slight even compared to a normal secondary battery 1. Therefore, since it takes a long time to obtain a voltage difference sufficient to detect an internal short - circuit, there has been a problem that it takes time to detect an internal short - circuit.

[0006] An object of the present disclosure is to provide an internal short - circuit detection device, a power storage device, an internal short - circuit detection method, and a program that can quickly detect an internal short - circuit of a secondary battery.

Means for Solving the Problems

[0007] The internal short - circuit detection device according to the present disclosure includes a current acquisition unit that acquires a charging current for each of a plurality of secondary batteries charged by constant - current constant - voltage charging; a charge control unit that individually charges the plurality of secondary batteries for a predetermined time when the charging current to the plurality of secondary batteries decreases; a short - circuit detection unit that detects an internal short - circuit of the secondary battery based on the charging current of each of the secondary batteries in the individual charging and is provided with.

[0008] In addition, the power storage device according to the present disclosure includes a plurality of secondary batteries charged by constant - current constant - voltage charging; the above - mentioned internal short - circuit detection device and is provided with.

[0009] Furthermore, the internal short - circuit detection method according to the present disclosure includes acquiring a charging current for each of a plurality of secondary batteries charged by constant - current constant - voltage charging; when the charging current to the plurality of secondary batteries decreases, individually charging the plurality of secondary batteries for a predetermined time; detecting an internal short - circuit of the secondary battery based on the charging current of each of the secondary batteries in the individual charging.

[0010] Furthermore, the program according to the present disclosure causes a computer to execute the above - mentioned internal short - circuit detection method.

Advantages of the Invention

[0011] According to the present disclosure, an internal short - circuit of a secondary battery can be quickly detected.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present disclosure. In addition, the present disclosure includes all combinations of configurations that can be combined among the configurations shown in the following embodiments. Also, in each figure, those with the same reference numerals are the same or corresponding ones, which is common throughout the entire specification.

[0014] [Configuration of Power Storage Device 100] FIG. 1 is a circuit diagram showing an example of the configuration of the power storage device 100 according to the present embodiment. As shown in FIG. 1, the power storage device 100 includes a plurality of secondary batteries 1, a switch unit 2, a detection unit 3, and a control unit 4.

[0015] In addition, the power storage device 100 includes a charging terminal 101 and a grounding terminal 102. The charging terminal 101 and the grounding terminal 102 are provided for connection to an external device. For example, when charging the secondary battery of the power storage device 100, the charging terminal 101 and the grounding terminal 102 are connected to an external power source that is a power supply.

[0016] Although not shown, the power storage device 100 is provided with a discharge terminal that is connected to an external load to be powered when discharging the power stored in the secondary battery.

[0017] The plurality of secondary batteries 1 are rechargeable batteries and are connected in parallel. Each secondary battery 1 is composed of one or a plurality of secondary battery cells. When each of the secondary batteries 1 is composed of a plurality of secondary battery cells, the secondary battery 1 is configured, for example, by connecting the secondary battery cells in series. The secondary battery 1 is, for example, a nickel-zinc battery.

[0018] When charging, the secondary battery 1 is connected to the charging terminal 101 and the grounding terminal 102. Thereby, a charging path that connects the charging terminal 101 and the grounding terminal 102 is formed in the power storage device 100.

[0019] The switch unit 2 is disposed between the charging terminal 101 and the secondary battery 1 in the charging path. The switch unit 2 has a plurality of charging switches 20 that individually correspond to the plurality of secondary batteries 1. Each charging switch 20 switches the connection and disconnection of the charging path of the corresponding secondary battery 1 based on control by the control unit. Thereby, charging and stopping of charging for each secondary battery 1 are switched.

[0020] The detection unit 3 is a current sensor that detects the charging current of each secondary battery 1. Then, the detection unit 3 supplies the detected charging current to the control unit.

[0021] The control unit 4 controls the entire power storage device 100. In the present embodiment, the control unit 4 controls the charging switch 20 of the switch unit 2, and performs an internal short circuit detection process for detecting an internal short circuit of the secondary battery 1 based on the charging current of each secondary battery 1 detected by the detection unit 3 at that time. Details of the internal short circuit detection process will be described later.

[0022] FIG. 2 is a functional block diagram showing an example of the configuration of the control unit 4 in FIG. 1. In FIG. 2, only the processing units related to the functions related to the internal short circuit detection process among the functions provided in the control unit 4 are shown. As shown in FIG. 2, the control unit 4 includes a current acquisition unit 41, a comparison determination unit 42, a switch control unit 43, an extraction unit 44, an arithmetic unit 45, and a storage unit 46.

[0023] The current acquisition unit 41 acquires the charging current of each secondary battery 1 detected by the detection unit 3. The acquired charging current is supplied to the comparison determination unit 42 and the extraction unit 44.

[0024] The comparison determination unit 42 determines whether the charging current flowing through the entire secondary battery 1 has decreased from the current value during constant current charging based on the charging current of each secondary battery 1 supplied from the current acquisition unit 41.

[0025] Also, the comparison determination unit 42 compares the difference value ΔI calculated by the arithmetic unit 45 with the threshold value I TH stored in the storage unit 46 to determine whether an internal short circuit has occurred in the secondary battery 1. Then, when the comparison determination unit 42 determines that an internal short circuit has occurred in the secondary battery 1, it determines that the secondary battery 1 with the maximum charging current has an internal short circuit. The comparison determination unit 42 corresponds to the "short circuit detection unit" of the present disclosure.

[0026] The switch control unit 43 controls the charging switch 20 of the switch unit 2 based on the determination result of the charging current decrease by the comparison determination unit 42. When it is determined by the comparison determination unit 42 that the charging current has decreased, the switch control unit 43 outputs a control signal for controlling the ON and OFF of the corresponding charging switch 20 so that each of the plurality of secondary batteries 1 is individually and sequentially charged. The switch control unit 43 corresponds to the "charging control unit" of the present disclosure.

[0027] The extraction unit 44 extracts the maximum value I max and the minimum value I min from the charging current supplied from the current acquisition unit 41. The extracted maximum value I max and minimum value I min of the charging current are supplied to the arithmetic unit 45.

[0028] The arithmetic unit 45 calculates the difference value ΔI between the maximum value I max and the minimum value I min of the charging current supplied from the extraction unit 44. The difference value ΔI obtained by the calculation is supplied to the comparison determination unit 42.

[0029] The storage unit 46 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory), HDD (Hard Disk Drive), or SSD (Solid State Drive), etc. The storage unit 46 stores various information used in the control unit 4. In the present embodiment, the storage unit 46 stores in advance the threshold value I TH used in the comparison determination unit 42.

[0030] FIG. 3 is a block diagram showing an example of the main part of the control system of the control unit 4 according to the present embodiment. As shown in FIG. 3, the control unit 4 includes a CPU (Central Processing Unit) 1001, a ROM (Read Only Memory) 1002, a RAM (Random Access Memory) 1003, and the like. Each part constituting the control unit 4 is connected by a bus 1005. Further, a storage device 1004 corresponding to the storage unit 46 in FIG. 2 is also connected to the bus 1005.

[0031] The CPU 1001 reads out a program corresponding to the processing content from the ROM 1002 and expands it in the RAM 1003, and controls the operation of the power storage device 100 in cooperation with the expanded program. The storage device 1004 stores various data used for the operations of the CPU 1001 and the like.

[0032] [Internal short - circuit detection process of secondary battery 1] Next, a method for detecting an internal short - circuit of the secondary battery 1 will be described. As also described in the background art section, conventionally, an internal short - circuit of the secondary battery 1 has been detected based on the amount of change in the battery voltage during the self - discharge of the secondary battery 1.

[0033] For example, when the secondary battery 1 is a nickel - zinc battery, the secondary battery 1 usually uses a constant - current constant - voltage charging method in which, after charging the secondary battery 1 with a constant charging current, it is charged with a constant charging voltage. Then, when the secondary battery 1 reaches a fully - charged state and the charging process stops, thereafter, the battery voltage of the secondary battery 1 gradually decreases due to self - discharge. At this time, whether or not an internal short - circuit has occurred in the secondary battery 1 can be determined based on the amount of decrease in the battery voltage during self - discharge.

[0034] FIG. 4 is a graph for explaining the change in the battery voltage of the secondary battery 1. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the battery voltage. In the example shown in FIG. 4, the change in the battery voltage after the full - charge of the secondary battery 1, which is a nickel - zinc battery, is detected is shown. Also, the solid - line graph shows the change in the battery voltage of the normal secondary battery 1. The dashed - line graph shows the change in the battery voltage of the secondary battery 1 in which an internal short - circuit has occurred.

[0035] As shown in FIG. 4, when a full charge of the secondary battery 1 is detected, the battery voltage of the secondary battery 1 gradually decreases due to self-discharge. At this time, the secondary battery 1 in which an internal short circuit has occurred has a larger amount of decrease in battery voltage compared to the normal secondary battery 1. Therefore, a voltage difference ΔV occurs in the battery voltage between the normal secondary battery 1 and the secondary battery 1 in which an internal short circuit has occurred at a certain point in time. Therefore, the internal short circuit of the secondary battery 1 can be detected based on this voltage difference ΔV.

[0036] However, the temporal change amount (decrease amount) of the battery voltage during self-discharge of the secondary battery 1 in which an internal short circuit has occurred is slight even when compared to the normal secondary battery 1. Therefore, in order to detect the internal short circuit of the secondary battery 1, it takes a certain amount of time after the full charge is detected.

[0037] On the other hand, the inventor has found that in a nickel-zinc battery, when an internal short circuit occurs, the amount of decrease when the charging current decreases from a constant value during charging becomes gentler compared to the normal secondary battery 1. This is presumably because zinc oxide that inhibits discharge is formed inside the secondary battery 1 in which an internal short circuit has occurred. Also, the temporal change amount of the charging current at this time is larger compared to the temporal change amount of the battery voltage. Therefore, in the present embodiment, the internal short circuit of the secondary battery 1 is detected based on the change amount of the charging current when the charging current of the secondary battery 1 decreases.

[0038] FIG. 5 is a graph for explaining the change in the charging current of the secondary battery 1. In FIG. 5, the horizontal axis represents time, and the vertical axis represents the charging current. In the example shown in FIG. 5, the change in the charging current near the full charge of the secondary battery 1, which is a nickel-zinc battery, is shown. Also, the solid line graph shows the change in the charging current of the normal secondary battery 1. The dashed line graph shows the change in the charging current of the secondary battery 1 in which an internal short circuit has occurred.

[0039] As shown in FIG. 5, after charging the secondary battery 1 with a constant current, the charging current decreases. At this time, when the secondary battery 1 is a nickel-zinc battery, the secondary battery 1 in which an internal short circuit has occurred has a smaller decrease in the charging current compared to the normal secondary battery 1.

[0040] Also, the temporal change amount of the charging current at this time is larger compared to the temporal change amount of the battery voltage shown in FIG. 4. Therefore, by detecting the internal short circuit of the secondary battery 1 that is a nickel-zinc battery based on the change amount of the charging current, the internal short circuit can be detected more quickly than by detecting the internal short circuit based on the change amount of the conventional battery voltage.

[0041] (Specific example of internal short circuit detection process) Next, the internal short circuit detection process according to the present embodiment will be described with a specific example. Hereinafter, the case of detecting the internal short circuit of the secondary battery 1 in the power storage device 100 including three secondary batteries 1A, 1B, and 1C connected in parallel will be considered.

[0042] FIG. 6 is a circuit diagram for explaining the flow of the charging current during constant current charging in the power storage device 100 according to the present embodiment. FIG. 7 is a circuit diagram for explaining the flow of the charging current when the charging current decreases in the power storage device 100 according to the present embodiment. Note that FIGS. 6 and 7 show only the charging path in the power storage device 100 for ease of explanation. Also, the arrows in the figures indicate the paths through which the charging current flows.

[0043] As shown in FIG. 6, the power storage device 100 in this example includes three secondary batteries 1A, 1B, and 1C connected in parallel. The power storage device 100 also includes a switch unit 2 having charging switches 20A, 20B, and 20C provided corresponding to the respective secondary batteries 1A, 1B, and 1C.

[0044] First, as shown in FIG. 6, during constant current charging, the control unit 4 controls the switch unit 2 so that a charging current flows through all the secondary batteries 1A, 1B, and 1C. That is, the control unit 4 controls the switch unit 2 so that all of the charging switches 20A, 20B, and 20C of the switch unit 2 are "ON". Thereby, the charging current is flowing through all the secondary batteries 1A, 1B, and 1C.

[0045] When a decrease in the charging current is detected from the state shown in FIG. 6, the control unit 4 controls the switch unit 2 so that the respective secondary batteries 1A, 1B, and 1C are individually and sequentially charged, as shown in FIG. 7. That is, the control unit 4 controls the switch unit 2 so that any one of the charging switches 20A, 20B, and 20C is "ON". Here, it is assumed that the secondary batteries 1A, 1B, and 1C are individually charged every 3 seconds.

[0046] For example, at the time when 0 seconds have elapsed since the decrease in the charging current was detected (the time when the decrease in the charging current was detected), the control unit 4 controls the switch unit 2 so that the charging current flows only through the secondary battery 1A. That is, the control unit 4 controls the switch unit 2 so that the charging switch 20A is "ON" and the charging switches 20B and 20C are "OFF". Thereby, the charging current flows only through the secondary battery 1A.

[0047] Then, the control unit 4 acquires the charging current flowing through the secondary battery 1A at this time. It is preferable that the control unit 4 acquires the charging current detected by the detection unit 3 at a predetermined time before, such as 1 second before the switch unit 2 is next controlled. This is because if the charging current is acquired immediately after the switch unit 2 is controlled, a measurement error may occur due to noise or the like caused by the switching of the switch. That is, in this example, the control unit 4 acquires the charging current detected at the time when 2 seconds have elapsed since the decrease in the charging current was detected.

[0048] Next, when 3 seconds have elapsed since the detection of the decrease in the charging current, the control unit 4 controls the switch unit 2 so that the charging current flows only through the secondary battery 1B. That is, the control unit 4 controls the switch unit 2 so that the charging switch 20B is turned "ON" and the charging switches 20A and 20C are turned "OFF". Thereby, the charging current flows only through the secondary battery 1B.

[0049] And the control unit 4 acquires the charging current flowing through the secondary battery 1B at this time. For example, the control unit 4 acquires the charging current detected at the time when 5 seconds have elapsed since the detection of the decrease in the charging current (the time when 2 seconds have elapsed since the charging current started to flow only through the secondary battery 1B).

[0050] Next, when 6 seconds have elapsed since the detection of the decrease in the charging current, the control unit 4 controls the switch unit 2 so that the charging current flows only through the secondary battery 1C. That is, the control unit 4 controls the switch unit 2 so that the charging switch 20C is turned "ON" and the charging switches 20A and 20B are turned "OFF". Thereby, the charging current flows only through the secondary battery 1C.

[0051] And the control unit 4 acquires the charging current flowing through the secondary battery 1C at this time. For example, the control unit 4 acquires the charging current detected at the time when 8 seconds have elapsed since the detection of the decrease in the charging current (the time when 2 seconds have elapsed since the charging current started to flow only through the secondary battery 1C).

[0052] In this way, when the charging currents flowing through all of the secondary batteries 1A, 1B, and 1C are acquired individually, the control unit 4 determines the maximum value I max and the minimum value I min from the charging currents of the respective secondary batteries 1A, 1B, and 1C. Further, the control unit 4 calculates a difference value ΔI, which is the difference between the maximum value I max and the minimum value I min of the charging current.

[0053] Here, when no internal short circuit has occurred in any of the secondary batteries 1A, 1B, and 1C, there is almost no difference in the charging currents of the respective secondary batteries 1A, 1B, and 1C that are obtained. Therefore, the calculated difference value ΔI becomes approximately "0".

[0054] On the other hand, when an internal short circuit has occurred in any of the secondary batteries 1A, 1B, and 1C, the difference value ΔI becomes a significant value. Therefore, the control unit 4 compares the calculated difference value ΔI with a preset threshold value I TH and, when the difference value ΔI is equal to or greater than the threshold value I TH it can be determined that an internal short circuit has occurred in any of the secondary batteries 1A, 1B, and 1C.

[0055] Also, as described above, in the case of a nickel-zinc battery, when an internal short circuit occurs, the amount of decrease in current becomes gentler than in the normal state. Therefore, the control unit 4 can determine that an internal short circuit has occurred in the secondary battery 1 in which the maximum value I max of the charging current with the least amount of decrease in the charging current is detected.

[0056] (Processing flow) FIG. 8 is a flowchart showing an example of the flow of the internal short circuit detection process by the power storage device 100 according to the present embodiment. The internal short circuit detection process is performed when the charging process for a plurality of secondary batteries 1 mounted on the power storage device 100 is started.

[0057] First, in step S1, the current acquisition unit 41 of the control unit 4 acquires the total charging current flowing through all the secondary batteries 1. The acquisition of the total charging current by the current acquisition unit 41 is performed periodically every predetermined time.

[0058] In this case, for example, the current acquisition unit 41 acquires the respective charging currents flowing through the respective secondary batteries 1 detected by the detection unit 3. Then, the current acquisition unit 41 acquires the total charging current by adding all the acquired charging currents.

[0059] Note that the method for obtaining the overall charging current is not limited to this example. For example, an ammeter may be pre - arranged in the charging path before it branches to each secondary battery 1, and the current acquisition unit 41 may acquire the overall charging current obtained using this ammeter.

[0060] In step S2, the comparison and determination unit 42 determines whether the overall charging current acquired by the current acquisition unit 41 has decreased. For example, the comparison and determination unit 42 compares the overall charging current acquired this time with the overall charging current acquired last time, and determines that the overall charging current has decreased when the current value has decreased by a predetermined value or more.

[0061] Note that the method for determining the decrease in the overall charging current is not limited to this example. For example, a threshold value may be set in advance for the overall charging current, and the comparison and determination unit 42 may determine that the overall charging current has decreased when the acquired charging current is less than (or less than or equal to) the threshold value.

[0062] When it is determined that the overall charging current has decreased (step S2: Yes), the process proceeds to step S3. When it is determined that the overall charging current has not decreased (step S2: No), the process returns to step S1.

[0063] In step S3, the switch control unit 43 controls the charging switch 20 of the switch unit 2 so as to charge the plurality of secondary batteries 1 individually.

[0064] In step S4, the comparison and determination unit 42 determines whether a predetermined time has elapsed since the charging switch 20 was controlled. When the predetermined time has elapsed (step S4: Yes), the current acquisition unit 41 acquires the charging current of the individually charged secondary battery 1 in step S5. On the other hand, when the predetermined time has not elapsed (step S4: No), the process returns to step S4, and the process of step S4 is repeated until the predetermined time elapses.

[0065] In step S6, the comparison determination unit 42 determines whether the charging current has been acquired for all the secondary batteries 1. When the charging current of all the secondary batteries 1 has been acquired (step S6: Yes), the process proceeds to step S7.

[0066] On the other hand, when the charging current of all the secondary batteries 1 has not been acquired (step S6: No), the process returns to step S3, and the switch control unit 43 controls the charging switch 20 to charge the next secondary battery 1. Then, the processes from step S3 to step S6 are repeated until the charging current of all the secondary batteries 1 is acquired.

[0067] In step S7, the extraction unit 44 extracts the maximum value I max and the minimum value I min from the acquired respective charging currents. In step S8, the calculation unit 45 calculates the difference value ΔI between the maximum value I max and the minimum value I min of the charging currents extracted by the extraction unit 44.

[0068] In step S9, the comparison determination unit 42 compares the difference value ΔI calculated by the calculation unit 45 with the threshold value I TH stored in the storage unit 46, and determines whether the difference value ΔI is greater than or equal to the threshold value I TH . As a result of the comparison, when the difference value ΔI is greater than or equal to the threshold value I TH (step S9: Yes), the comparison determination unit 42 detects an internal short circuit in the secondary battery 1 in step S10. Further, the comparison determination unit 42 determines that an internal short circuit has occurred in the secondary battery 1 in which the charging current has become the maximum value I max .

[0069] On the other hand, when the difference value ΔI is less than the threshold value I TH (step S9: No), the process proceeds to step S3. In this case, the charging switch 20 corresponding to the first secondary battery 1 is switched to ON, and the processes from step S3 to step S9 are repeated.

[0070] As described above, in the power storage device 100 according to the present embodiment, the charging current of the entire plurality of secondary batteries 1 charged by constant current constant voltage charging is detected, and when the charging current to the plurality of secondary batteries 1 decreases, the plurality of secondary batteries 1 are sequentially charged individually for a predetermined time. Then, an internal short circuit of the secondary battery 1 is detected based on the charging current of each secondary battery 1 when charged individually.

[0071] At this time, the charging current of the secondary battery 1 in which the internal short circuit has occurred has a large temporal change amount compared to the battery voltage. Therefore, by detecting the internal short circuit of the secondary battery 1 based on the charging current, the internal short circuit of the secondary battery can be detected more quickly than in the prior art.

[0072] As described above, the present embodiment has been described. However, the present disclosure is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the gist of the present disclosure. For example, in the present embodiment, it has been described that when the difference value ΔI of the charging current is equal to or greater than the threshold value I TH it is determined that an internal short circuit has occurred in the secondary battery 1, but this is not limited to this example.

[0073] For example, even if an internal short circuit has occurred in the secondary battery 1, due to some factor, the difference value ΔI of the charging current may be less than the threshold value I TH . Therefore, the control unit 4 repeatedly performs the control of charging the plurality of secondary batteries 1 individually for a predetermined time a plurality of times, and when the difference value ΔI continuously becomes equal to or greater than a predetermined value smaller than the threshold value I TH for a predetermined number of times such as three times, it may be determined that an internal short circuit has occurred in the secondary battery 1. After repeatedly performing the control of charging the plurality of secondary batteries 1 individually for a predetermined time a plurality of times in this way, the control unit 4 controls the switch unit 2 so as to charge the entire plurality of secondary batteries 1.

[0074] In addition, in this embodiment, the case where the secondary battery 1 is a nickel-zinc battery has been described. However, for example, any secondary battery that performs constant current-constant voltage charging and has the characteristic that the amount of decrease in the charging current is less than that of a normal secondary battery when an internal short circuit occurs can apply the internal short circuit detection process according to this embodiment.

Explanation of Signs

[0075] 1, 1A, 1B, 1C Secondary battery 2 Switch unit 3 Detection unit 4 Control unit 20, 20A, 20B, 20C Charging switch 41 Current acquisition unit 42 Comparison and judgment unit 43 Switch control unit 44 Extraction unit 45 Calculation unit 46 Storage unit 100 Power storage device 101 Charging terminal 102 Grounding terminal

Claims

1. A current acquisition unit that acquires a charging current for each of a plurality of secondary batteries charged by constant current constant voltage charging; A charging control unit that individually charges the plurality of secondary batteries for a predetermined time when the charging current to the plurality of secondary batteries decreases; A short-circuit detection unit that detects an internal short circuit of the secondary battery based on the charging current of each of the secondary batteries in the individual charging An internal short-circuit detection device comprising:

2. The short-circuit detection unit: When a difference value between a maximum value and a minimum value of the charging current of each of the secondary batteries in the individual charging is equal to or greater than a threshold value, detects an internal short circuit of the secondary battery The internal short-circuit detection device according to claim 1.

3. The charging control unit: Repeats the individual charging, The short-circuit detection unit: When a state in which a difference between a maximum value and a minimum value of the charging current of each of the secondary batteries in the individual charging is equal to or greater than a predetermined value smaller than the threshold value continues for a predetermined number of times, detects an internal short circuit of the secondary battery The internal short-circuit detection device according to claim 2.

4. The charging control unit: After repeating the individual charging a predetermined number of times, simultaneously charges all of the plurality of secondary batteries The internal short-circuit detection device according to claim 3.

5. The short-circuit detection unit: When an internal short circuit of the secondary battery is detected, determines that the secondary battery having the maximum charging current in the individual charging is internally short-circuited The internal short-circuit detection device according to claim 2 or 3.

6. A plurality of secondary batteries charged by constant current constant voltage charging; The internal short-circuit detection device according to claim 1 A power storage device comprising

7. The secondary battery is a nickel-zinc battery The power storage device according to claim 6.

8. The plurality of secondary batteries are connected in parallel The power storage device according to claim 6.

9. Obtain the charging current for each of a plurality of secondary batteries charged by constant current constant voltage charging, When the charging current to the plurality of secondary batteries decreases, charge the plurality of secondary batteries individually for a predetermined time each, Detect an internal short circuit of the secondary battery based on the charging current of each of the secondary batteries in the individual charging Internal short circuit detection method.

10. A program for causing a computer to execute the internal short circuit detection method according to claim 9.

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