JP7348108B2 - battery unit - Google Patents

Description

The present invention relates to a battery unit, and more particularly to a battery unit that allows failure diagnosis of a protection function of a battery module to be performed while the battery module is in operation.

[Conventional technology]
In recent years, as various products have become smaller and more portable, batteries have become widely used in UPS (Uninterruptible Power Supply) and the like that operate in the event of a power failure.
Furthermore, as the population declines in the future, batteries are expected to be installed in self-driving unmanned vehicles and the like that will be introduced for the same reason, and the market is expected to expand.
There are two types of batteries: disposable primary batteries and secondary batteries that can be repeatedly charged and discharged. Secondary batteries are often used, especially by general users.

In applications where environmental resistance is a priority, batteries using highly safe nickel-metal hydride cells may be considered, but lithium-ion cells with high energy density are preferred due to their advantages of compactness, portability, and long-term use. Generally widespread.

However, since lithium ion cells have a high energy density, if a short-circuit failure occurs, there is a risk of ignition or the like, which may pose a danger to the user. Therefore, a safety mechanism (protection circuit) is essential.

A normally operating battery module normally performs a discharging operation when supplying power to the load side, and a charging operation when receiving power.
A protective FET (Field Effect Transistor) is provided between the battery and the load (on the output side of the battery), which has a switch function to stop supplying power to the load in the event of an abnormality.

During charging and discharging, if the protection FET is operating normally, the gate side is in the ON state and the drain and source remain conductive.
The protection IC (Integrated Circuit) installed in the battery module controls the protection FET, and detects abnormal conditions of the battery based on the information (current, voltage, temperature, etc.) obtained from these protection components. When detected, the protection FET is turned off. This turns off the charge/discharge function and operates to maintain a safe state.

If the protective FET is normal, it is possible to transition to a safe state by turning off the protective FET in the event of an abnormality, but if the protective FET itself is malfunctioning, the protective IC will not function properly. Even if the FET is controlled to be turned off, the circuit remains on, making it impossible to stop the power supply when an abnormality occurs in the device.

[Related technology]
Incidentally, as a related prior art, there is Japanese Patent Application Publication No. 2013-084605 "Integrated circuit for battery cell" (Patent Document 1).
Patent Document 1 discloses that in a vehicle battery system, overcharging and overdischarging are diagnosed to monitor the state of battery cells, thereby improving the reliability of the entire system.

Japanese Patent Application Publication No. 2013-084605

In this way, conventional battery protection circuits have the problem of being inconvenient because it is not possible to diagnose the failure of protective function components (protective components) such as protective FETs while they are in operation. there were.
In addition, in conventional battery protection circuits, the number of components increases to diagnose failures in protective components, making the configuration complex. It is something that has not become a thing.
Furthermore, it takes time to diagnose failures of multiple protective components.

Note that Patent Document 1 does not describe that failure diagnosis of protective components can be easily performed while the battery module is in an operating state.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a battery unit in which a failure diagnosis of a protection function of a battery module can be easily performed while the battery module is in operation.

The present invention for solving the problems of the conventional example provides a battery unit including three or more plurality of battery modules, wherein each battery module has a protection function for maintaining the safety of the battery module. and a control unit that controls a plurality of protection parts corresponding to a plurality of battery modules, the control unit divides the plurality of protection parts into a plurality of groups in which at least one overlaps, and controls the protection parts for each group. The present invention is characterized in that a failure diagnosis process is performed to identify a group in which a failed protection component exists.

The present invention provides, in the above-mentioned battery unit, when the control section determines that there is a failed protection component in a specific group through a failure diagnosis process for each group, the control section detects a plurality of protection components in the specific group. The present invention is characterized in that it is divided into a plurality of smaller groups in which at least one overlaps, a failure diagnosis process is performed for each of the smaller groups, and a failed protection component is identified and notified.

In the battery unit of the present invention, the control section periodically performs and monitors failure diagnosis processing for each group, and when a group in which a failed protection component exists is identified, multiple protection components within the identified group are The protection component is divided into a plurality of smaller groups in which at least one overlaps, and a failure diagnosis process is performed on the smaller groups to identify a faulty protection component.

According to the present invention, the control unit divides a plurality of protection parts each having a protection function for maintaining the safety of a plurality of battery modules into groups in which at least one overlaps, and Since the battery unit performs fault diagnosis processing to identify the group in which the faulty protection component exists, the effect is that fault diagnosis of the protection function of the battery module can be easily performed while the battery module is in operation. be.

FIG. 3 is a schematic diagram of a circuit configuration of a first battery unit. FIG. 3 is a schematic diagram of a circuit configuration of a second battery unit. FIG. 3 is a schematic diagram of a circuit configuration of a third battery unit. FIG. 3 is a schematic diagram illustrating a failure diagnosis procedure for a plurality of battery modules. It is an explanatory diagram of the operation mode in this unit device.

Embodiments of the present invention will be described with reference to the drawings.
[Overview of embodiment]
The battery unit (this unit) according to the embodiment of the present invention is equipped with a control section that performs failure diagnosis of protective components even when the battery is being driven, and can easily prevent failures without stopping the device. It is possible to realize diagnosis. In other words, this unit is a battery unit equipped with a failure diagnosis function.
Next, regarding this unit, the battery units of the first to third embodiments (first to third battery units) will be specifically described.

[First battery unit: Figure 1]
The first battery unit will be explained with reference to FIG. 1. FIG. 1 is a schematic circuit diagram of a first battery unit.
As shown in FIG. 1, the first battery unit is equipped with one battery module and has two protection circuits, including a battery 1a as a battery module, and protection FETs 2a and 2b as protection circuits. , a protection IC 3a, a current sense resistor 4a, switches (SW) 5a, 5b, current sense resistors 6a, 6b, rectifier diodes 7a, 7b, a control section 8, and a load 9.

Further, in the first battery unit, one end of a current sense resistor 4a is connected to the negative terminal (-terminal) side of the battery 1a, and the other end is grounded.
A positive terminal (+terminal) of battery 1a is connected to the source terminals of protective FETs 2a and 2b, and its drain terminals are connected to the anodes of rectifier diodes 7a and 7b via current sense resistors 6a and 6b. Moreover, the output terminals of SW5a and 5b are connected to the gate terminals of protection FETs 2a and 2b.

The protection IC 3a is connected to the positive terminal and the negative terminal of the battery 1a and the other end of the current sense resistor 4a, receives these voltages, detects the voltage value, and detects the current value flowing through the current sense resistor 4a. There is.
The protection IC 3a is also connected to the control section 8 and is controlled by the control section 8. Specific control will be described later.

The SWs 5a and 5b are supplied with power from the protection IC 3a, and turn on/off the gate terminals of the protection FETs 2a and 2b under control from the control section 8.
Further, the cathodes of the rectifying diodes 7a and 7b are coupled, and current is supplied to the load 9.

Although the control unit 8 is provided inside the load 9, it may be configured separately. In the case of a separate configuration, the current supplied to the load 9 is branched and input to the control unit 8.
The control unit 8 performs input/output with the protection IC 3a, detects the current value flowing through the current sense resistors 6a and 6b, and outputs an on/off switching control instruction to the SWs 5a and 5b.
Further, the control unit 8 performs a failure diagnosis process on the protective component, and when a failure is detected, specifies and notifies the user of the protective component diagnosed as having failed.

[Operation of first battery unit]
The first battery unit has a structure in which a battery 1a is protected by a protection IC 3a.
Specifically, the protection IC 3a measures and monitors the current flowing through the battery 1a with the current sense resistor 4a, and when it determines that the current is larger than the threshold value, turns off the protection FETs 2a and 2b via the control unit 8. This stops the power supply from the battery 1a and activates the protection function.

The protection FETs 2a and 2b are controlled to be turned on and off by SWs 5a and 5b according to instructions from the control section 8.
Note that in order to monitor the normality/abnormality of the protective components, the control section 8 may turn off the protective FETs 2a and 2b to operate the protective function. This operation will be described later.

To explain the details of the operation of the first battery unit, normally one of the protective FETs 2a and 2b is in an on state (conducting state), and for example, power is supplied to the load 9 with the protective FET 2a in an on state. .

When the protection IC 3a detects that the load 9 is short-circuited and the current flowing through the current sense resistor 4a has become larger than usual, the control unit 8 turns off the SWs 5a and 5b, and turns off the protection FETs 2a and 2b. (non-conducting state), the power supply to the load 9 is stopped. At this time, the control unit 8 monitors the current flowing through the current sense resistors 6a, 6b connected to the latter stages of the protective FETs 2a, 2b.

[Fault diagnosis processing]
Next, a description will be given of a process for diagnosing a failure of a protective component in the control unit 8.
If the current value flowing through the current sense resistor 4a of the battery 1a is C, the current value flowing through the current sense resistor 6a is A, and the current value flowing through the current sense resistor 6b is B, the control unit 8 determines that "A+B=C". If so, the protective FETs 2a and 2b are operating normally, and are determined to be normal as a result of the failure diagnosis.

Next, when the control unit 8 determines that "A+B≠C", it diagnoses that the protective FET 2a or the protective FET 2b has failed. However, it is assumed that the current C flowing through the current sense resistor 4a is a normal value.

When the control unit 8 determines that "A+B≠C", the current values of A+B and C that are monitored when the device is operating normally with a constant current value (for example, 1 ampere) are determined. compare. In order to determine that the sum of the currents A and B is within the normal range, it is necessary to maintain a threshold value within the control unit 8.

For example, when A=B=0.5 ampere, the total is 1 ampere, and the current value of C is not 1 ampere, so it can be seen that the current value of C flowing through the current sense resistor 4a is NG.
In other words, it can be determined that there is a high possibility of failure of the current sense resistor 4a, and the control unit 8 notifies the user of the possibility of failure of the current sense resistor 4a.

Furthermore, in the case of A≠B, the current value of A or B becomes NG, which means that the protective FET 2a or the protective FET 2b may be out of order, and the current cannot flow. In this case as well, the control unit 8 notifies the user of the possibility of failure of the protective FET 2a or the protective FET 2b.

Next, when the control unit 8 determines that the current value of A or B being monitored is out of the normal range of steady current, SW5a or SW5b is connected to the path of the current value out of the normal range. Turn off the current value and check again that one current value matches the current value C.

For example, if current value B<current value A, by turning off SW5b of the path where current value B flows, if it is confirmed that current value A≒current value C, then protection of the path through which current value B flows. It can be determined that there is a high possibility that the protection FET 2b is out of order, and the control unit 8 notifies the user of the possibility that the protection FET 2b is out of order.

In this way, in the first battery unit, if one protective FET fails, the other protective FET can operate, so the failure diagnosis process is performed while the operating state continues, and the user is informed of the possibility of failure. It is something that can notify the gender.

[Second battery unit: Figure 2]
Next, the second battery unit will be explained with reference to FIG. 2. FIG. 2 is a schematic diagram of the circuit configuration of the second battery unit.
As shown in FIG. 2, the second battery unit is equipped with two battery modules and has correspondingly two protection circuits, including batteries 1b and 1c, protection FETs 2c and 2d, and protection circuits. It includes ICs 3b and 3c, current sense resistors 4b and 4c, rectifier diodes 7c and 7d, a control section 8, and a load 9.

Furthermore, in the second battery unit, one end of current sense resistors 4b, 4c is connected to the negative terminal (-terminal) side of batteries 1b, 1c, and the other end is grounded.
The positive terminals (+ terminals) of the batteries 1b, 1c are connected to the source terminals of the protective FETs 2c, 2d, and the drain terminals thereof are connected to the anodes of the rectifier diodes 7c, 7d. Furthermore, protection ICs 3b and 3c are connected to the gate terminals of the protection FETs 2c and 2d.

The protection ICs 3b, 3c are connected to the positive and negative terminals of the batteries 1b, 1c, and the other ends of the current sense resistors 4b, 4c, and input these voltages to detect the voltage value, and also connect to the current sense resistors 4b, 4c. The value of the current flowing through is detected.
The protection ICs 3b and 3c are also connected to the control section 8 and are controlled by the control section 8. Specific control will be described later.

The cathodes of the rectifier diodes 7c and 7d are coupled together, and current is supplied to one end of the load 9. Further, the other end of the load 9 is grounded.
Although the control unit 8 is provided inside the load 9, it may be configured separately.
The control unit 8 performs input/output between the protection ICs 3b and 3c, controls the voltage output to the gate terminals of the protection FETs 2c and 2d, and controls the operation of the protection FETs 2c and 2d.

[Operation of second battery unit]
In the second battery unit, the on/off control of the protective FETs 2c and 2d via the protection ICs 3b and 3c by the control section 8 enables a protective operation (off operation of the protective FETs 2c and 2d) in the event of an abnormality.

When the second battery unit is operating normally, the batteries 1b and 1c are discharging, but when diagnosing a failure, the control unit 8 sends a control signal to the protection ICs 3b and 3c to protect them. OFF control of the FETs 2c and 2d can be performed.

For example, when diagnosing a failure of the protection FET 2c, the protection IC 3b monitors the current flowing through the current sense resistor 4b with the protection FET 2c turned on. This monitored current value is defined as data 1 (DATA1). Furthermore, the value of the current flowing through the current sense resistor 4b is monitored with the protection FET 2c turned off. This monitored current value is defined as data 2 (DATA2). Confirm that the difference in the acquired data does not become less than the current value including the error.

In other words,
(DATA1-DATA2) - If current value including error > 0, "normal"
(DATA1-DATA2) - If the current value including error ≦0, "abnormality (failure)"
The control unit 8 diagnoses the problem, and in the case of failure, notifies the user of the failure of the protective FET 2c. Note that the current value that includes an error is a specific value that has been measured in advance.

[Third battery unit: Figure 3]
Next, the third battery unit will be explained with reference to FIG. 3. FIG. 3 is a schematic diagram of the circuit configuration of the third battery unit.
The third battery unit operates with three or more battery modules and performs failure diagnosis. Note that FIG. 3 shows an example in which three battery modules are mounted.

As shown in FIG. 3, the third battery unit is equipped with three battery modules and has correspondingly three protection circuits, including batteries 1d, 1e, 1f, protection FETs 2e, 2f, 2g, protection ICs 3d, 3e, 3f, current sense resistors 4d, 4e, 4f, 4g, rectifier diodes 7e, 7f, 7g, a control section 8, and a load 9.

Furthermore, in the third battery unit, one end of current sense resistors 4d, 4e, 4f is connected to the negative terminal (-terminal) side of batteries 1d, 1e, 1f, and the other end is grounded.
The positive terminals (+ terminals) of the batteries 1d, 1e, 1f are connected to the source terminals of the protective FETs 2e, 2f, 2g, and the drain terminals thereof are connected to the anodes of the rectifier diodes 7e, 7f, 7g. Furthermore, protection ICs 3d, 3e, and 3f are connected to the gate terminals of the protection FETs 2e, 2f, and 2g.

The protection ICs 3d, 3e, and 3f are connected to the positive and negative terminals of the batteries 1d, 1e, and 1f, and the other ends of the current sense resistors 4d, 4e, and 4f, input these voltages, and detect the voltage values. The current value flowing through current sense resistors 4d, 4e, and 4f is detected.
The protection ICs 3d, 3e, and 3f are also connected to the control section 8 and are controlled by the control section 8. Specific control will be described later.

The cathodes of the rectifier diodes 7e, 7f, and 7g are connected, and current is supplied to one end of the load 9. Further, the other end of the load 9 is grounded.
Although the control unit 8 is configured separately from the load 9, it may be configured to be provided inside the load 9.
The control unit 8 performs input/output between the protection ICs 3d, 3e, and 3f, controls the voltage output to the gate terminals of the protection FETs 2e, 2f, and 2g, and controls the operations of the protection FETs 2e, 2f, and 2g. ing.
Further, the control unit 8 inputs the current value of the entire current flowing through the current sense resistor 4g, and utilizes it for fault diagnosis. Specifically, this will be explained with reference to FIG.

[Operation of third battery unit]
The operation of the third battery unit is similar to that of the second battery unit, and the fault diagnosis processing is also similar. However, since there are multiple battery modules, they are divided into groups and diagnostic processing is performed simultaneously within each group.
For example, in FIG. 3, the protection IC 3d and the protection IC 3e are set as the first group, the protection IC 3e and the protection IC 3f are set as the second group, and the fault diagnosis process is performed for each group to identify the group in which the faulty component exists, and I'm trying to narrow down the parts.

Here, the protection ICs included in the group need to be duplicated, and the number of protection FETs to be diagnosed in duplicate is approximately the same as the number of protection FETs to be diagnosed in each group. Thereby, if there is a faulty part, it is possible to quickly narrow down the search until it is identified.

[Fault diagnosis procedure for multiple battery modules: Figure 4]
Next, a failure diagnosis procedure for a configuration equipped with a plurality of battery modules will be described with reference to FIG. 4. FIG. 4 is a schematic diagram illustrating a failure diagnosis procedure for a plurality of battery modules.
In FIG. 4, assuming that nine battery modules are mounted in the entire device and their protective FETs are designated as protective FETs (1) to (9), the groups are divided as follows.
Group A: Protection FETs (1) to (6)
Group B: Protection FETs (4) to (9)

[Fault diagnosis procedure 1 (1)]
First, the overall current value when all the protection FETs (1) to (9) are in the on state is measured by the current sense resistor 4g, and the control unit 8 stores it as the overall total current value I(1-9). put.
Then, group A is targeted for failure diagnosis, and the control unit 8 controls the protection ICs belonging to group A to turn off the protection FETs (1) to (6), and turns off the protection FETs (7) to (6) that do not belong to group A. (9) is turned on, and the current value I(7-9) when protection FETs (7) to (9) are turned on is measured and stored using a current sense resistor of 4 g.

Next, the difference between the overall total current value I(1-9) and the current value I(7-9) is calculated, and it is determined whether the difference matches the steady current value Ir1. The steady current value is a differential current value obtained when all of the protection FETs (1) to (9) have no failure (all are normal).

Then, when the calculated difference [I(1-9)-I(7-9)]=Ir1, the protection FETs (1) to (6) of group A are determined to be normal.
If [I(1-9)-I(7-9)]≠Ir1, it is determined that the failed protection FET is included in the protection FETs (1) to (6) of group A.

[Fault diagnosis procedure 1 (2)]
Similarly, if the failure diagnosis is performed with group B as the target, it will be confirmed that the protection FETs (4) to (9) of group B are normal, or that the protection FETs (4) to (9) of group B are normal. It is determined that the faulty protection FET is included in the protection FET.
If group A is normal and group B is normal, it can be diagnosed that there is no malfunctioning protective component through two diagnostic processes.

[Fault diagnosis procedure 2 (1)]
If it is determined that a faulty component exists in step 1 (1) and step 1 (2) above, and if group A is normal, protect FETs (7) to (9) that do not belong to group A are checked for fault diagnosis. It is further divided into two groups: a group of protection FETs (7) to (8) (group 7-8) and a group of protection FETs (8) to (9) (group 8-9).
Then, the control unit 8 controls the protection ICs belonging to group A and group 7-8 to turn off the protection FETs (1) to (8), and turns off the protection FETs (9) that do not belong to group A and group 7-8. is turned on, and the current value I(9) when the protection FET (9) is on is measured and stored using the current sense resistor 4g.

Next, the difference between the overall total current value I(1-9) and the current value I(9) is calculated, and it is determined whether the difference matches the steady current value Ir2. The steady-state current value Ir2 is also a value measured in advance during normal operation.
If the difference [I(1-9)-I(9)]=Ir2, the protection FETs (1) to (8) are normal, and the protection FET (9) can be determined to be a failed component. Up to this point, the faulty component can be identified by performing the fault diagnosis process three times.

Also, if the difference [I(1-9)-I(9)]≠Ir2, protection FETs (1) to (6), and (9) are normal, and protection FETs (7) to (8) are normal. It can be determined that it is a failed part. After this, turn on only the protection FET (7) or the protection FET (8), calculate the difference from the overall total current value I (1-9), and judge whether it matches the steady current value Ir2. to diagnose the failure and identify the failed part. Up to this point, the faulty component can be identified by performing the fault diagnosis process four times.

[Fault diagnosis procedure 2 (2)]
If it is determined that a faulty component exists in step 1 (1) and step 1 (2) above, and group B is normal, protect FETs (1) to (3) that do not belong to group B are The target is further divided into two groups: a group of protection FETs (1) to (2) (group 1-2) and a group of protection FETs (2) to (3) (group 2-3), and the same as above. Performs fault diagnosis processing.

[Fault diagnosis procedure 2 (3)]
If it is determined that a faulty part exists in step 1 (1) and step 1 (2) above, and if group A contains the faulty part and group B also contains the faulty part, it will be classified as group A. This means that there is a faulty component among the protective components in which group B overlaps.

In this case, the protection FETs (4) to (6), which are the overlapping parts, are targeted for failure diagnosis, and the group of protection FETs (4) to (5) (group 4-5) and the protection FET (5) The failure diagnosis process is divided into two groups (groups 5-6) of (6) to (6).

Specifically, the control unit 8 controls the protection ICs belonging to group A and group 7-8 to turn off protection FETs (1) to (5), (7) to (9), and turns off protection FETs (6) and 7-8. is turned on, and the current value I(6) when the protection FET (6) is on is measured and stored using the current sense resistor 4g.

After this, calculate the difference between the overall total current value I (1-9) and the current value I (6), judge whether it matches the steady current value Ir2, perform a fault diagnosis, and identify the faulty part. .
FIG. 4 shows an example in which the protection FET (5) is identified as a failed component. With nine protective parts, a faulty part can be identified through four diagnostic processes.

[Operating mode: Figure 5]
Next, the operation mode of this unit will be explained with reference to FIG. FIG. 5 is an explanatory diagram of operation modes in this unit.
As shown in Figure 5, the mode of this device is changed during operation, and the mode changes from normal mode to periodic monitoring mode, which monitors the failure status of the device at fixed time intervals (for example, every hour). .

In the periodic monitoring mode, failure diagnosis procedures 1(1) and 1(2) are performed to determine whether there is a failure. If there is no failure, it returns to normal mode.
If there is a failure, the system shifts to failure location identification mode, performs failure diagnosis procedures 2(1), 2(2), and 2(3) to identify the failure location and displays an error message to the user. As an error display, a log display, a lamp (LED) display, etc. are performed, and the system returns to the normal mode.
In this way, the mode is changed in this device.

[Effects of embodiment]
According to this unit, while multiple protective parts are in operation, the protective functions of the protective parts are diagnosed and the user is notified of the malfunctioning parts, making it easy to identify malfunctioning parts. There is.

[Effects of first battery unit]
According to the first battery unit, one battery module is equipped with two systems of protective parts, and while operating with one protective part, failure diagnosis is performed with the other protective part. Therefore, there is an effect that failure diagnosis can be performed while the battery module is in an operating state.

[Effects of second battery unit]
According to the second battery unit, the two battery modules are each equipped with their own protective parts, and while one of the battery modules is operated with the other protective part, failure diagnosis is performed with the other protective part. This has the effect of allowing failure diagnosis to be performed while the battery module is in an operating state.

[Effects of third battery unit]
According to the third battery unit, three or more battery modules are each equipped with their own protective parts, the protective parts are divided into two overlapping groups, and some of the protective parts are operated. Since the failure diagnosis of other protective parts is performed while the battery module is in the operating state, there is an effect that the failure diagnosis can be performed while the battery module is in the operating state.

INDUSTRIAL APPLICABILITY The present invention is suitable for a battery unit in which a failure diagnosis of a protection function of a battery module can be easily performed while the battery module is in operation.

1a, 1b, 1c, 1d, 1e, 1f...Battery, 2a, 2b, 2c, 2d, 2e, 2f, 2g...Protection FET, 3a, 3b, 3c. 3d, 3e, 3f...Protection IC, 4a, 4b, 4c, 4d, 4e, 4f, 4g...Current sense resistor, 5a, 5b...Switch (SW), 6a, 6b...Current sense resistor, 7a, 7b, 7c, 7d, 7e, 7f, 7g... Rectifier diode, 8... Control unit, 9... Load

Claims (3)

A battery unit comprising three or more battery modules,
Each of the battery modules includes a protection component having a protection function that maintains the safety of the battery module, and a control unit that controls the plurality of protection components corresponding to the plurality of battery modules,
The control unit divides the plurality of protective components into a plurality of groups in which at least one overlaps, performs a failure diagnosis process for each group, and identifies a group in which a failed protective component exists. Features a battery unit. When the control unit determines that there is a failed protective component in a specific group through failure diagnosis processing for each group, the control unit converts the multiple protective components in the specific group into multiple additional protective components in which at least one overlaps. 2. The battery unit according to claim 1, wherein the battery unit is divided into small groups, a failure diagnosis process is performed for each small group, and a failed protection component is identified and notified. When the control unit periodically performs and monitors failure diagnosis processing for each group and identifies a group in which a failed protective component exists, it determines whether at least one of the multiple protective components in the identified group is duplicated. The battery unit according to claim 2, wherein the battery unit is divided into a plurality of smaller groups, and a failure diagnosis process is performed in each of the smaller groups to identify the failed protection component.

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