Power storage device, and circuit breaker failure diagnosing method

Abstract

This power storage device comprises a power storage element and a management device. The management device comprises a circuit breaker that interrupts a current pathway between the power storage element and a connection terminal for connecting the power storage element to the outside, and a control unit that controls the circuit breaker, wherein: the circuit breaker includes a composite switch that is configured by connecting a plurality of semiconductor switches in parallel; the resistance value of a normal semiconductor switch is R1 in a closed state, R2 in an open state, and R3, where R1<R3<R2, in a state in which a prescribed diagnostic gate voltage is applied; and the control unit executes measurement processing for measuring the resistance value of the composite switch in a state in which the diagnostic gate voltage is applied to the composite switch, and diagnostic processing for diagnosing a failure of the composite switch on the basis of the measured resistance value of the composite switch.

Description

Fault diagnosis method for power storage device and circuit breaker

[0001] The present disclosure relates to a power storage device and a fault diagnosis method for a circuit breaker.

[0002] Conventionally, energy storage devices have been developed that include an energy storage element and a circuit breaker that interrupts a current path of a current flowing through the energy storage element (see, for example, Patent Document 1 below). Semiconductor switches such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), and bipolar transistors are sometimes used as circuit breakers. When bonding wires or gate oxide films inside the semiconductor are damaged by electrical or thermal stress, the semiconductor switch may lose the ability to control its conductive or non-conductive state. For example, a known failure of a semiconductor switch is one in which the semiconductor switch does not close even when an appropriate gate voltage is applied to the semiconductor switch (hereinafter referred to as an open fault).

[0003] Japanese Patent Application Laid-Open No. 2016-118571

[0004] In order to reduce circuit breaker costs and simplify wiring, circuit breakers are sometimes constructed from multiple semiconductor switches connected in parallel, with the gate wiring of the multiple semiconductor switches shared. If one of the semiconductor switches in such a circuit breaker experiences an open circuit fault, current may concentrate in the normal semiconductor switches, causing the normal semiconductor switches to overheat and resulting in circuit breaker malfunction. However, if one of the semiconductor switches experiences an open circuit fault, current may flow through the other normal semiconductor switches, causing the circuit breaker to appear to operate normally, making it difficult to detect the circuit breaker fault.

[0005] The present disclosure was completed in light of the above circumstances, and has an object to diagnose open faults in semiconductor switches connected in parallel with a simple configuration.

[0006] The energy storage device of the present disclosure includes an energy storage element and a management device. The management device includes a circuit breaker that interrupts a current path between the energy storage element and a connection terminal for connecting the energy storage element to an external device, and a control unit that controls the circuit breaker. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and the resistance value of the semiconductor switch in a normal state is R １ In the open state, R ２ and when a predetermined diagnostic gate voltage is applied, R １ <R ３ <R ２ R satisfies ３ The control unit executes a measurement process of measuring a resistance value of the composite switch while the diagnostic gate voltage is applied to the composite switch, and a diagnosis process of diagnosing a fault in the composite switch based on the measured resistance value of the composite switch.

[0007] The present disclosure also provides a fault diagnosis method for a circuit breaker for diagnosing a fault in a circuit breaker provided in a power storage device. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and the resistance value of the semiconductor switch in a normal state is R １ In the open state, R ２ and when a predetermined diagnostic gate voltage is applied, R １ <R ３ <R ２ R satisfies ３ The fault diagnosis method includes a measurement step of measuring a resistance value of the composite switch while the diagnostic gate voltage is applied to the composite switch, and a diagnosis step of diagnosing a fault in the composite switch based on the measured resistance value of the composite switch.

[0008] According to the present disclosure, it is possible to diagnose open faults in semiconductor switches connected in parallel with a simple configuration.

[0009] It is a figure which shows the electrical configuration of the electric storage device concerning embodiment 1. It is a graph which shows the relationship between the resistance value and the gate voltage of the semiconductor switch. It is a flowchart which shows the open fault diagnosis processing. It is a figure which shows the electrical configuration of the electric vehicle which includes the electric storage device concerning embodiment 2.

[0010] (Summary of the present embodiment) (1) The energy storage device of the present disclosure includes an energy storage element and a management device. The management device includes a circuit breaker that interrupts a current path between the energy storage element and a connection terminal for connecting the energy storage element to an external device, and a control unit that controls the circuit breaker. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and the resistance value of the semiconductor switch in a normal state is R １ In the open state, R ２ and when a predetermined diagnostic gate voltage is applied, R １ <R ３ <R ２ R satisfies ３ The control unit executes a measurement process of measuring a resistance value of the composite switch while the diagnostic gate voltage is applied to the composite switch, and a diagnosis process of diagnosing a fault in the composite switch based on the measured resistance value of the composite switch.

[0011] According to the above configuration, the control unit determines whether the resistance value of the normal semiconductor switch is R ３ The resistance of the composite switch is measured while a diagnostic gate voltage is applied to the composite switch such that the resistance of the composite switch is measured. The resistance of the composite switch measured in this manner shows a significant difference depending on whether or not at least one semiconductor switch has an open circuit fault. Therefore, it is possible to diagnose an open circuit fault in the semiconductor switches that make up the composite switch.

[0012] (2) In the energy storage device of (1) above, the composite switch may include a parasitic diode connected in parallel to the semiconductor switch, and the control unit may perform the measurement process in a state where no current flows through the parasitic diode.

[0013] With this configuration, the resistance value of the compound switch can be measured more accurately, thereby improving the accuracy of fault diagnosis.

[0014] (3) In the energy storage device of (1) or (2) above, the composite switch may be a discharge cut-off unit that cuts off the current flowing from the energy storage element to the connection terminal, and the control unit may perform the measurement process during the shutdown of a system to which the energy storage element is electrically connected.

[0015] With this configuration, the current flowing from the storage element to the connection terminal is reduced during the system shutdown process, so that the amount of heat generated in the semiconductor switch during the measurement process can be reduced.

[0016] (4) In the storage device of (1) or (2) above, the composite switch may be a charge cut-off unit that cuts off the current flowing from the connection terminal to the storage element, and the control unit may perform the measurement process during CV charging at the end of CCCV charging.

[0017] With this configuration, the current flowing from the connection terminal to the storage element is reduced during CV charging, so that the amount of heat generated in the semiconductor switch during measurement processing can be reduced.

[0018] (5) A fault diagnosis method for a circuit breaker disclosed herein diagnoses a fault in a circuit breaker provided in a power storage device. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and the resistance value of the semiconductor switch in a normal state is R １ In the open state, R ２ and when a predetermined diagnostic gate voltage is applied, R １ <R ３ <R ２ R satisfies ３ The fault diagnosis method includes a measurement step of measuring a resistance value of the composite switch while the diagnostic gate voltage is applied to the composite switch, and a diagnosis step of diagnosing a fault in the composite switch based on the measured resistance value of the composite switch.

[0019] According to the above-mentioned fault diagnosis method for a circuit breaker, the resistance value of a normal semiconductor switch is R ３The resistance of the composite switch is measured with a diagnostic gate voltage that satisfies the following equation: The resistance of the composite switch measured in this manner shows a significant difference depending on whether or not at least one semiconductor switch has an open circuit fault. Therefore, it is possible to diagnose an open circuit fault in the semiconductor switches that make up the composite switch.

[0020] (6) In the circuit breaker fault diagnosis method described above in (5), the composite switch may include a parasitic diode connected in parallel to the semiconductor switch, and the measurement step may be performed in a state where no current flows through the parasitic diode.

[0021] According to this method for diagnosing a fault in a circuit breaker, the resistance value of the compound switch can be measured more accurately, thereby improving the accuracy of the fault diagnosis.

[0022] (7) In the circuit breaker fault diagnosis method described above in (5) or (6), the composite switch may be a discharge interruption unit that interrupts the current flowing from the storage element to the connection terminal, and the measurement process may be performed during the shutdown of a system to which the storage device is electrically connected.

[0023] According to this method for diagnosing a fault in a circuit breaker, the amount of current flowing from the storage element to the connection terminal is reduced during the system shutdown process, so that the amount of heat generated in the semiconductor switch can be reduced during the measurement process.

[0024] (8) In the circuit breaker fault diagnosis method described above in (5) or (6), the composite switch is a charge cut-off unit that cuts off the current flowing from the connection terminal to the storage element, and the measurement process may be performed during CV charging at the end of CCCV charging.

[0025] According to this method for diagnosing circuit breaker faults, the current flowing from the connection terminal to the storage element is reduced during CV charging, so that the amount of heat generated in the semiconductor switch can be reduced during the measurement process.

[0026] First Embodiment A first embodiment of the present disclosure will be described with reference to Fig. 1 to Fig. 3. A power storage device 1 according to this embodiment is mounted on a vehicle such as an engine vehicle, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a two-wheeled vehicle, or another mobile object.

[0027] As shown in FIG. 1 , the energy storage device 1 includes a battery pack 2, a battery management system (hereinafter referred to as BMS) 3, and connection terminals 4A and 4B. The battery pack 2 is an example of an energy storage element and is configured by connecting multiple cells C in series. Each cell C is a rechargeable secondary battery, such as a lithium-ion battery. The battery pack 2 of this embodiment has four cells C. Note that the battery pack may be configured with only one cell, or two, three, or five or more cells connected in series.

[0028] The BMS 3 is an example of a management device and includes a control unit 31, a circuit breaker 32, gate drivers 36A and 36B, voltage sensors 37A and 37B, and a current sensor 38.

[0029] The control unit 31 has a central processing unit (hereinafter referred to as CPU) and memory. Various programs for controlling the operation of the BMS 3 are stored in the memory, and the CPU controls each part of the BMS 3 in accordance with the programs read from the memory. The memory includes RAM and ROM. Note that the media on which the various programs are stored may be non-volatile memories such as a CD-ROM, a hard disk drive, or a flash memory, in addition to RAM.

[0030] The circuit breaker 32 is provided in the current path between the battery pack 2 and the connection terminal 4A. The circuit breaker 32 includes a discharge cutoff unit 33 and a charge cutoff unit 34. The discharge cutoff unit 33 cuts off the current (discharge current) that flows when the battery pack 2 supplies power to a load or the like. The charge cutoff unit 34 cuts off the current (charge current) that flows when the battery pack 2 is charged by a charger. The discharge cutoff unit 33 and the charge cutoff unit 34 are each an example of a composite switch.

[0031] The discharge cutoff unit 33 is configured to include three semiconductor switches 35A, 35B, and 35C connected in parallel. The charge cutoff unit 34 is configured to include three semiconductor switches 35D, 35E, and 35F connected in parallel. In this embodiment, the semiconductor switches 35A to 35F are FETs. More specifically, the semiconductor switches 35A to 35F are N-channel MOSFETs. Hereinafter, when there is no need to distinguish between the semiconductor switches 35A to 35F, they may be described as semiconductor switch 35. Parasitic diodes D1 to D6 are connected in parallel to each of the semiconductor switches 35A to 35F.

[0032] The forward direction of the parasitic diodes D1 to D3 is the charging direction of the battery pack 2. When the semiconductor switches 35A to 35C are opened, the discharging current from the battery pack 2 is cut off, but the charging current to the battery pack 2 flows through the parasitic diodes D1 to D3. The forward direction of the parasitic diodes D4 to D6 is the discharging direction of the battery pack 2. When the semiconductor switches 35D to 35F are opened, the charging current to the battery pack 2 is cut off, but the discharging current from the battery pack 2 flows through the parasitic diodes D4 to D6.

[0033] The sources of the discharge cutoff unit 33 and the charge cutoff unit 34 are connected in common, i.e., back-to-back. The drain of the discharge cutoff unit 33 is connected to the positive electrode of the battery pack 2. The drain of the charge cutoff unit 34 is connected to the connection terminal 4A. The gates of the discharge cutoff unit 33 and the charge cutoff unit 34 are connected to gate drivers 36A and 36B, respectively. The gates of the semiconductor switches 35A to 35C are unified. The gates of the semiconductor switches 35D to 35F are unified.

[0034] Gate drivers 36A, 36B are each configured to receive a control signal from control unit 31, and in response to the control signal from control unit 31, discharge cut-off unit 33 and charge cut-off unit 34 are each set to a closed (on) state, an open (off) state, or a diagnostic state, which will be described later.

[0035] Voltage sensor 37A measures the voltage between the drain and source of discharge cutoff unit 33. Voltage sensor 37B measures the voltage between the drain and source of charge cutoff unit 34. Each of voltage sensors 37A and 37B transmits the voltage measurement results to control unit 31.

[0036] The current sensor 38 measures the current flowing through the current path between the battery pack 2 and the connection terminal 4. The current sensor 38 transmits the current measurement result to the control unit 31.

[0037] 2 is a graph plotting the resistance value of a normal semiconductor switch 35 against the gate voltage applied to the gate of the semiconductor switch 35. "Normal" here means a state in which there is no failure. A normal semiconductor switch 35 has a resistance of V １ When a gate voltage of R is applied to the semiconductor switch 35, the semiconductor switch 35 is in a closed state. １ The normal semiconductor switch 35 is V ２ When a gate voltage of R is applied to the semiconductor switch 35, the semiconductor switch 35 is in an open state. ２ is.

[0038] In this embodiment, the gate drivers 36A and 36B apply a predetermined diagnostic gate voltage (voltage value V3) to put the semiconductor switch 35 into a diagnostic state. The diagnostic gate voltage is a voltage applied when the resistance value of the semiconductor switch 35 is R １ <R ３ <R ２ R satisfies ３ It is defined as the gate voltage at which R １ is, for example, several hundred microohms to several milliohms. ２ Although the figure shows ２ may be too large to be measured.

[0039] The control unit 31 of this embodiment executes a measurement process to measure the resistance value of the composite switch (discharge cut-off unit 33 or charge cut-off unit 34) in the above-mentioned diagnostic state, and a diagnostic process to diagnose whether at least one of the semiconductor switches 35 included in the composite switch has an open fault based on the results of the measurement process (open fault diagnostic process).

[0040] The measurement process is performed by applying a predetermined threshold I Ｓ For example, when an open fault diagnosis process is performed on the semiconductor switches 35A to 35C of the discharge cutoff unit 33, if there is a positive current I Ｓ The measurement process is performed when the following discharge current is flowing: When a charge current is flowing in the current path, no current flows through the semiconductor switches 35A to 35C, but current flows through the parasitic diodes D1 to D3, and therefore the measurement process cannot be performed.

[0041] When performing open circuit fault diagnosis on the semiconductor switches 35D to 35F of the charge cutoff unit 34, the current path is Ｓ The measurement process is performed when the following charging current is flowing: When a discharging current is flowing in the current path, no current flows through the semiconductor switches 35D to 35F, but current flows through the parasitic diodes D4 to D6, and therefore the measurement process cannot be performed.

[0042] Threshold I Ｓ For example, R ３ ・(I Ｓ / 3) ２ This setting is made so that the amount of heat generated by the semiconductor switch 35 represented by the formula (1) does not become excessive. This makes it possible to prevent the semiconductor switch 35 from being damaged due to overheating during the measurement process.

[0043] 3 is a flowchart showing an example of the procedure for the open circuit fault diagnosis process. Here, the procedure for the open circuit fault diagnosis process will be described in detail using the example in which the composite switch to be diagnosed is the discharge cutoff unit 33. The control unit 31 inputs an ON signal to the gate driver 36A to close the semiconductor switches 35A to 35C of the discharge cutoff unit 33 (S1).

[0044] Next, the current value input from the current sensor 38, that is, the current value flowing through the discharge cutoff unit 33, is determined as I Ｓ It is determined whether the current value flowing through the discharge cutoff unit 33 is equal to or less than I ＳIf the current value is equal to or less than I (S2: YES), the control unit 31 executes the measurement process. Ｓ If it is greater than the predetermined value (S2: NO), the control unit 31 does not execute the measurement process. In this case, for example, after a predetermined time has elapsed, the process returns to S2.

[0045] In the measurement process, the control unit 31 inputs a diagnostic signal to the gate driver 36A and applies a diagnostic gate voltage V ３ is applied (S3). This places the semiconductor switches 35A to 35C in a diagnostic state. Then, with the diagnostic gate voltage V3 applied, the voltage value between the drain and source of the discharge cutoff unit 33 measured by the voltage sensor 37A and the current value measured by the current sensor 38 are acquired (S4). From the voltage value and current value acquired in S4, the resistance value (hereinafter referred to as R ＤＩＡＧ ) is calculated (S5).

[0046] The normal semiconductor switch 35 has a resistance value R ３ Therefore, if all of the semiconductor switches 35A to 35C are normal, R ＤＩＡＧ is R ３ On the other hand, if the semiconductor switch 35A has an open fault and the semiconductor switches 35B and 35C are normal, R ＤＩＡＧ is R ３ For example, if the semiconductor switches 35A and 35B have an open circuit fault and the semiconductor switch 35C is normal, R ＤＩＡＧ is R ３ In this way, R ＤＩＡＧ Based on this, it is possible to diagnose whether or not at least one of the semiconductor switches 35A to 35C included in the discharge cutoff unit 33 has an open circuit fault. ＤＩＡＧ is a predetermined threshold R Ｓ It is determined whether R is greater than R (S6, diagnostic process). Ｓ is R ３ / 3 or more, and R ３ / 2. That is, R Ｓis the R when all the semiconductor switches 35A to 35C included in the discharge cutoff unit 33 are normal. ＤＩＡＧ In addition, when any one of the semiconductor switches 35A to 35C included in the discharge cutoff unit 33 has an open fault and the others are normal, R ＤＩＡＧ Considering the individual differences in the electrical characteristics of the semiconductor switch 35, R Ｓ is, for example, R ３ It is preferable that the value be slightly larger than 1 / 3.

[0047] The control unit 31 is ＤＩＡＧ is R Ｓ If it is greater than R (S6: YES), it is diagnosed that at least one of the semiconductor switches 35A to 35C has an open circuit fault (S7). ＤＩＡＧ is R Ｓ If the following is true, it is determined that none of the semiconductor switches 35A to 35C has an open circuit fault, that is, the semiconductor switches 35A to 35C are normal (S8). With the above, the open circuit fault diagnosis process for the discharge cutoff unit 33 is completed.

[0048] The control unit 31 may include a display unit that displays text information of the diagnosis result (e.g., "Open fault present," "No open fault present," etc.) after S7 or S8. Alternatively, the control unit 31 may notify the user terminal of the information of the diagnosis result.

[0049] R ３ , R Ｓ , and I Ｓ Regarding R Ｓ ・I Ｓ is within a range that can be detected by the voltage sensor 37A, and the heat generation amount R of the semiconductor switch 35 is ３ ・(I Ｓ / 3) ２ From this viewpoint, it is preferable to set the value so that both R ３ is R １ It is preferable that the density is several to several hundred times higher than that of the conventional method.

[0050] (Effects of First Embodiment) According to the first embodiment, the control unit 31 detects whether the resistance value of the semiconductor switch 35 is R３ The diagnostic gate voltage V ３ is applied to the composite switch (the discharge cutoff unit 33 or the charge cutoff unit 34), the resistance value R ＤＩＡＧ The resistance value R of the compound switch measured in this way is ＤＩＡＧ shows a significant difference depending on whether or not there is an open fault in at least one semiconductor switch 35. Therefore, it is possible to diagnose an open fault in the semiconductor switches 35 that constitute the compound switch.

[0051] In the first embodiment, the control unit 31 executes the measurement process of the discharge cutoff unit 33 while no current flows through the parasitic diodes D1 to D3. The control unit 31 executes the measurement process of the charge cutoff unit 34 while no current flows through the parasitic diodes D4 to D6. With this configuration, the resistance value of the combined switch (the discharge cutoff unit 33 or the charge cutoff unit 34) can be measured more accurately, thereby improving the accuracy of fault diagnosis.

[0052] Second Embodiment A second embodiment of the present disclosure will be described with reference to Fig. 4. The power storage device according to this embodiment is an auxiliary battery 101 mounted on an electric vehicle 100. The auxiliary battery 101 has a configuration similar to that of the power storage device 1 according to the first embodiment. Fig. 4 schematically shows the electrical configuration of the electric vehicle 100. In addition to the auxiliary battery 101, the electric vehicle 100 is configured to include a drive battery 110, a charger 120, a DC / DC converter 130, a load 140, an inverter 150, a drive motor 160, a system main relay 170, and the like.

[0053] The drive battery 110 has a rated voltage of, for example, 100 V to 400 V. The drive battery 110 can be charged by a charger 120. The drive battery 110 is connected to a drive motor 160, which is the main load, via an inverter 150. The inverter 150 converts the power of the drive battery 110 from direct current to alternating current and supplies it to the drive motor 160. The drive motor 160 drives the electric vehicle 100 and drives the axles to which the wheels are attached.

[0054] The auxiliary battery 101 has a rated voltage of, for example, 12 V. The auxiliary battery 101 is connected to the charger 120 via a DC / DC converter 130. The DC / DC converter 130 charges the auxiliary battery 101 by stepping down the output voltage of the charger 120 and supplying the power to the auxiliary battery 101.

[0055] The auxiliary battery 101 is connected to a load 140. The load 140 is, for example, an electronic control unit (hereinafter referred to as an ECU), a clock, a light, an audio system, a security system, etc. The ECU is a higher-level device of the BMS 3 and is capable of communicating with a control unit 31 of the BMS 3.

[0056] The ECU controls the opening and closing of the system main relay 170. When the driver turns on the start switch to request system startup of the electric vehicle 100, the ECU outputs a signal to close (turn on) the system main relay 170. When the system main relay 170 is in the closed state, the drive battery 110 and the drive motor 160 are connected.

[0057] Furthermore, when the driver turns off the start switch to request a system shutdown of the electric vehicle 100, the ECU outputs a signal to open (turn off) the system main relay 170. When the system main relay 170 is in the open state, the electrical connection between the drive battery 110 and the drive motor 160 is released.

[0058] During the system shutdown process, the auxiliary battery 101 provides the power to the load 140. Until the system is completely shut down, the value of the discharge current from the auxiliary battery 101 decreases over time. Therefore, during the system shutdown process, the discharge current decreases to I Ｓ In the following cases, the control unit 31 may execute the measurement process of the open circuit fault diagnosis process of the discharge cutoff unit 33.

[0059] In this embodiment, the system main relay 170 is in the OFF state, and the auxiliary battery 101 is CCCV (Constant Current, Constant Voltage) charged by the charger 120. CCCV charging is a charging method in which charging is performed at a constant current value (CC charging) in the early stages of charging, and when the battery voltage value reaches a predetermined value close to the rated voltage, charging is performed at a constant voltage value (CV charging) to avoid overcharging. During CV charging at the end of CCCV charging, the charging current decreases over time. Therefore, during CV charging, Ｓ In the following cases, the control unit 31 may execute the measurement process of the open circuit fault diagnosis process of the charge cutoff unit 34.

[0060] Effect of Second Embodiment In the second embodiment, during the system shutdown process, a measurement process is executed for the open circuit fault diagnosis process of the discharge cutoff unit 33. Since the discharge current is small during the system shutdown process, the amount of heat generated in the semiconductor switch 35 of the discharge cutoff unit 33 can be suppressed during the measurement process.

[0061] In the second embodiment, during CV charging at the end of CCCV charging, the measurement process for the open circuit fault diagnosis process of the charge cutoff unit 34 is executed. Because the charging current is small during CV charging, the amount of heat generated in the semiconductor switch 35 of the charge cutoff unit 34 can be suppressed during the measurement process.

[0062] <Other Embodiments> The present disclosure is not limited to the embodiments described above and illustrated in the drawings, but is intended to include all modifications within the meaning and scope of the claims as defined by the claims. The technical scope of the present disclosure also includes, for example, the following embodiments.

[0063] In the first embodiment, the diagnostic gate voltage V3 is a voltage value between V2 and V1, but the diagnostic gate voltage does not have to be a voltage value between the gate voltage that closes the semiconductor switch and the gate voltage that opens the semiconductor switch.

[0064] In the first embodiment, the circuit breaker 32 includes two compound switches, the discharge circuit breaker 33 and the charge circuit breaker 34, but the circuit breaker may include one compound switch or three or more compound switches.

[0065] In embodiment 1, the discharge cut-off unit 33 and the charge cut-off unit 34 each have three semiconductor switches 35 connected in parallel, but the composite switch may also have two or four or more semiconductor switches connected in parallel.

[0066] In the first embodiment, the semiconductor switch 35 is an N-channel MOSFET, but the semiconductor switch may be a P-channel MOSFET. Also, the semiconductor switch may be other FETs.

[0067] The control unit that executes the open circuit fault diagnosis process of the present disclosure does not have to be provided inside the moving body.

[0068] DESCRIPTION OF SYMBOLS 1: Energy storage device 2: Battery pack (energy storage element) 3: BMS (management device) 4A, 4B: Connection terminal 31: Control unit 32: Circuit breaker 33: Discharge cutoff unit (composite switch) 34: Charge cutoff unit (composite switch) 35, 35A, 35B, 35C, 35D, 35E, 35F: Semiconductor switch 36A, 36B: Gate driver 37A, 37B: Voltage sensor 38: Current sensor D1, D2, D3, D4, D5, D6: Parasitic diode

Claims

1. A power storage device comprising a power storage element and a management device, wherein the management device comprises a circuit breaker that interrupts a current path between the power storage element and a connection terminal for connecting the power storage element to an external device, and a control unit that controls the circuit breaker, wherein the circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and the resistance value of the semiconductor switch in a normal state is R １ and in the open state, R ２ and when a predetermined diagnostic gate voltage is applied, R １ <R ３ <R ２ R satisfies ３ wherein the control unit executes a measurement process of measuring a resistance value of the composite switch with the diagnostic gate voltage applied to the composite switch, and a diagnosis process of diagnosing a failure of the composite switch based on the measured resistance value of the composite switch.

2. The energy storage device according to claim 1, wherein the composite switch includes a parasitic diode connected in parallel to the semiconductor switch, and the control unit executes the measurement process in a state where no current flows through the parasitic diode.

3. The power storage device according to claim 1 or 2, wherein the control unit executes the measurement process when the value of the current flowing through the compound switch is equal to or less than a predetermined value.

4. A storage device according to any one of claims 1 to 3, wherein the composite switch is a discharge cut-off unit that cuts off the current flowing from the storage element to the connection terminal, and the control unit executes the measurement process during the shutdown of a system to which the storage element is electrically connected.

5. The energy storage device according to any one of claims 1 to 3, wherein the composite switch is a charge cut-off unit that cuts off the current flowing from the connection terminal to the energy storage element, and the control unit executes the measurement process during CV charging at the end of CCCV charging.

6. The power storage device according to any one of claims 1 to 5, wherein the control unit notifies a user terminal of result information of the diagnostic processing.

7. A fault diagnosis method for a circuit breaker provided in a power storage device, wherein the circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and the resistance value of the normal semiconductor switch is R １ In the open state, R ２ and when a predetermined diagnostic gate voltage is applied, R １ <R ３ <R ２ R satisfies ３ a measuring step of measuring a resistance value of the composite switch with the diagnostic gate voltage applied to the composite switch; and a diagnosing step of diagnosing a fault in the composite switch based on the measured resistance value of the composite switch.

8. The circuit breaker fault diagnosis method according to claim 7, wherein the composite switch includes a parasitic diode connected in parallel to the semiconductor switch, and the measuring step is performed in a state where no current flows through the parasitic diode.

9. A fault diagnosis method for a circuit breaker according to claim 7 or claim 8, wherein the measuring step is performed when the value of the current flowing through the compound switch is equal to or less than a predetermined value.

10. A fault diagnosis method for a circuit breaker as set forth in any one of claims 7 to 9, wherein the composite switch is a discharge interruption unit that interrupts the current flowing from the storage element to the connection terminal, and the measurement process is performed during the shutdown of a system to which the storage device is electrically connected.

11. A circuit breaker fault diagnosis method as set forth in any one of claims 7 to 9, wherein the composite switch is a charge cutoff unit that cuts off the current flowing from the connection terminal to the storage element, and the measurement process is performed during CV charging at the end of CCCV charging.

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