JP5099097B2 - Battery monitoring device - Google Patents

Description

  The present invention relates to a battery monitoring device.

  Conventionally, for example, Patent Literature 1 proposes a battery control device having a failure diagnosis function for detecting that a threshold value for battery overcharge detection or overdischarge detection has spontaneously changed. Specifically, Patent Document 1 proposes a configuration in which a battery voltage is detected and the voltage is compared with a threshold value.

  In this configuration, when the battery voltage is compared with the threshold value, the threshold value is forcibly shifted from the original value by a fixed value. That is, the threshold value is switched by one level. The battery control device determines that the spontaneous change in the threshold is large when the magnitude relationship between the threshold and the battery voltage does not reverse despite the forced change of the threshold. In this way, the threshold characteristic deviation can be detected.

JP 2003-92840 A

  However, in the above conventional technique, when the threshold value is switched in one stage at the time of failure diagnosis, even if the threshold voltage does not cause a characteristic deviation, the battery voltage and the threshold value are There is a possibility that the magnitude relationship of will be reversed. For this reason, a failure may be erroneously detected.

  An object of this invention is to provide the battery monitoring apparatus which can improve the reliability of a failure diagnosis in view of the said point.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a battery monitoring device for monitoring the state of a plurality of battery cells connected in series,
Block voltage detecting means for detecting block voltages at both ends of a plurality of battery cells connected in series;
Monitoring means for inputting the battery voltage at both ends of the battery cell for each of the plurality of battery cells, comparing the battery voltage with the threshold value and outputting the comparison result, respectively;
While determining the state of each of the plurality of battery cells based on the comparison result of the monitoring means, the threshold value of the monitoring means is relatively changed in a plurality of stages for each of the plurality of battery cells and compared with the battery voltage and based on the comparison result. Determination means for performing failure diagnosis for detecting abnormality of the monitoring means,
The determination means receives the block voltage from the block voltage detection means, and performs failure diagnosis after confirming that the fluctuation of the block voltage is within the reference range.

  According to this, since the failure diagnosis is performed when the fluctuation of the block voltage is within the reference range, that is, the block voltage is stable, the erroneous detection of the failure can be prevented. Therefore, the reliability of failure diagnosis can be improved.

  In the invention according to claim 2, when the determination unit finishes the failure diagnosis of the monitoring unit related to one battery cell, the block voltage is input from the block voltage detection unit, and the fluctuation of the block voltage is within the reference range. After confirming this, the failure diagnosis of the monitoring means related to the next battery cell is performed.

  According to this, since the block voltage is detected for each battery cell and it is confirmed that the voltage fluctuation is within the reference range, the failure diagnosis can be performed while the voltage of the battery cell is stable. Therefore, the reliability of failure diagnosis can be improved.

In the invention according to claim 3, when a unit for dividing a plurality of battery cells into a predetermined number is a block, a plurality of blocks are set,
The block voltage detecting means and the monitoring means are provided for each of a plurality of blocks,
When the determination unit finishes the failure diagnosis of the monitoring unit related to one block, the block voltage is input from the block voltage detection unit related to the next block, and after confirming that the fluctuation of the block voltage is within the reference range The failure diagnosis of the monitoring means related to the next block is performed.

  According to this, since the block voltage is detected for each block and it is confirmed that the voltage fluctuation is within the reference range, failure diagnosis can be performed with the block voltage being stable. Therefore, the reliability of failure diagnosis can be improved.

  In the invention according to claim 4, the plurality of battery cells are at least one of monitoring means, a battery package in which the plurality of battery cells are packaged, and a connection connector between the plurality of battery cells and the monitoring means. It is characterized by being modularized in units.

  According to this, since the block voltage can be detected for each component in which the fluctuation of the block voltage may occur, the fluctuation of the block voltage can be easily detected. Therefore, the reliability of failure diagnosis can be improved.

As in the invention described in claim 5, the monitoring means includes a plurality of resistors and a plurality of switches for dividing the voltage of the battery cell,
The determination means can be configured to relatively change the threshold value in a plurality of stages by switching a plurality of switches and dividing the voltage of the battery cell by a plurality of resistors.

1 is an overall configuration diagram of a battery monitoring system including a battery monitoring device according to an embodiment. It is the figure which showed the structure with respect to one battery cell in the monitoring circuit shown by FIG. It is the flowchart which showed the flow of the failure diagnosis of a battery monitoring apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a battery monitoring system including a battery monitoring apparatus according to the present embodiment. As shown in FIG. 1, the battery monitoring system includes a battery cell 10 and a battery monitoring device 20.

  The battery cell 10 is a voltage source capable of generating a constant voltage, and is a so-called single cell. The battery cell 10 is used, for example, as a power source for driving a load or a power source for an electronic device. For example, a rechargeable secondary battery is employed as the battery cell 10. In the present embodiment, a lithium ion secondary battery is used as the battery cell 10.

  In addition, a plurality of battery cells 10 are connected in series to form a block 11. The block 11 is a unit for dividing the plurality of battery cells 10 into a predetermined number. In the present embodiment, six battery cells 10 are connected in series to form a block 11. That is, the block 11 is obtained by modularizing a plurality of battery cells 10. In FIG. 1, only one block 11 is shown, but actually, a plurality of blocks 11 are set, and a plurality of blocks 11 are combined in series to form one assembled battery.

  The battery monitoring device 20 has an overcharge / discharge detection function for monitoring overcharge and overdischarge as the state of the battery cell 10, and a failure diagnosis function for diagnosing a deviation in the threshold characteristic of these overcharge / discharge detections. It is. These overcharge and overdischarge states are abnormal in the battery cell 10.

  The overcharge / discharge detection function is a function of monitoring the voltage of the battery cell 10 by comparing the voltage of the battery cell 10 with a threshold value. When the battery cell 10 is a secondary battery, the battery monitoring device 20 monitors whether the voltage of the battery cell 10 is between a threshold value for detecting overcharge and a threshold value for detecting overdischarge.

  The failure diagnosis function is a function for detecting that the threshold for detecting overcharge / discharge has changed for some reason (for example, a circuit failure or the like). In other words, the failure diagnosis function uses the failure detection threshold for diagnosing whether there is an abnormality in the threshold for overcharge / discharge detection, and detects abnormalities (failures, disturbances, etc.) of each part that realizes the overcharge / discharge detection function. It is a function to detect.

  Such a battery monitoring device 20 includes a monitoring circuit 30, a discharging circuit 40, a block voltage detection unit 50, and a microcomputer 60 (hereinafter referred to as a microcomputer 60).

  The monitoring circuit 30 is a circuit configured to input battery voltages at both ends of the plurality of battery cells 10, compare them with threshold values, and output the comparison results. This monitoring circuit 30 is provided for each block 11. For example, an IC is used as the monitoring circuit 30.

  FIG. 2 is a diagram showing a configuration for one battery cell 10 in the monitoring circuit 30. In FIG. 2, the discharge circuit 40 is omitted. As shown in this figure, the monitoring circuit 30 includes a switching unit 31, a band gap unit 32, a comparator 33, and a transistor 34 for one battery cell 10.

  The switching unit 31 generates a threshold voltage corresponding to the threshold from the voltage of one battery cell 10. For this reason, the switching unit 31 is connected between the first wiring 35 electrically connected to the positive voltage of the battery cell 10 and the second wiring 36 electrically connected to the negative voltage of the battery cell 10. ing.

  Such a switching unit 31 includes a plurality of resistors 37 and a plurality of switches 38 in order to generate a threshold voltage that is a threshold value. The plurality of resistors 37 are connected in series between the first wiring 35 and the second wiring 36.

  The switch 38 is a path switching circuit configured by, for example, a resistance element or a transistor. Each switch 38 is connected to a connection point of each resistor 37, and each switch 38 is connected in parallel. A connection point where the switches 38 are connected in parallel is connected to a non-inverting input terminal (+) of the comparator 33.

  In the present embodiment, eleven resistors 37 are connected in series, and ten switches 38 are connected to the connection points of the resistors 37, respectively. The resistor 37 located closest to the second wiring 36 among the resistors 37 is a variable resistor for performing overcharge detection. On the other hand, the resistor 37 located closest to the first wiring 35 among the resistors 37 is a resistor for detecting overdischarge.

  When any one of the switches 38 is turned on, the voltage of the battery cell 10 is divided by each resistor 37, and this divided voltage is input to the non-inverting input terminal of the comparator 33 as a threshold voltage. The Therefore, when the switch 38 closest to the first wiring 35 among the switches 38 is turned on, one resistor 37 connected to the first wiring 35 and ten resistors 37 connected to the second wiring 36 are connected. The partial pressure is input to the comparator 33 as an overdischarge detection threshold, that is, a threshold voltage. The microcomputer 60 controls on / off of each switch 38.

  Thus, by switching each switch 38, the partial pressure of the battery cell 10 corresponding to any one of the overcharge detection threshold, the first threshold to the eighth threshold, and the overdischarge detection threshold is switched as the threshold voltage. The data is output from the unit 31 to the comparator 33.

  These overcharge detection threshold values, the first threshold value to the eighth threshold value, and the overdischarge detection threshold value are set within the voltage range of the battery cell 10. When a lithium ion battery is used as the battery cell 10, the overcharge detection threshold is set to 4.25V, for example, and the overdischarge detection threshold is set to 1.75V, for example. Therefore, the first threshold value to the eighth threshold value between the overcharge detection threshold value and the overdischarge detection threshold value are set in the operating voltage range of the battery cell 10, and are set, for example, between 1.75V and 4.25V, respectively. .

  Thus, the first threshold value to the eighth threshold value are switched stepwise within the voltage range used in the battery cell 10. By setting each threshold in this way, it is not necessary to switch the threshold stepwise for the entire range from the minimum value to the maximum value of the voltage of the battery cell 10.

  Moreover, each threshold value of the first threshold value to the eighth threshold value is used for the battery monitoring device 20 to perform failure diagnosis. Each threshold value of the first threshold value to the eighth threshold value is a constant value and is set so as to be relatively changed in a plurality of stages. For example, if the constant value is 0.1 V, each threshold value is set so that the difference between the first threshold value and the second threshold value is 0.1 V, and the difference between the second threshold value and the third threshold value is 0.1 V. ing. In other words, the resistance value of each resistor 37 is determined so that each threshold value changes stepwise with a constant value. In the present embodiment, at the time of failure diagnosis, switching is performed in stages from the largest first threshold value to the smallest eighth threshold value.

  The band gap part 32 is a voltage source that generates a constant reference voltage. The band gap portion 32 is connected between the inverting input terminal of the comparator 33 and the second wiring 36.

  The comparator 33 receives a threshold voltage from the switching unit 31 and a reference voltage from the band gap unit 32, and outputs these comparison results from an output terminal. The comparison result is output to the microcomputer 60. As such a comparator 33, a comparator can be used.

  As described above, the reference voltage is input to the inverting input terminal of the comparator 33, and the threshold voltage is input to the non-inverting input terminal. Therefore, when the threshold voltage is larger than the reference voltage, the output is a high level signal, and when the threshold voltage is smaller than the reference voltage, the output is a low level signal.

  The transistor 34 is dark current blocking means for preventing dark current from flowing through the resistors 37 connecting the first wiring 35 and the second wiring 36 when the battery cell 10 is not used. Thereby, when the battery cell 10 is not used, the battery cell 10 can be prevented from being consumed by the dark current.

  The above configuration is a configuration for one battery cell 10. Therefore, the monitoring circuit 30 is provided with the above configuration for each battery cell 10.

  The discharge circuit 40 is a circuit that constitutes an equalization circuit for reducing the voltage variation of each battery cell 10 constituting the block 11. The discharge circuit 40 is connected between the first wiring 35 and the second wiring 36 and serves as a current path through which a current flows from the positive electrode side to the negative electrode side of one battery cell 10.

  The equalization circuit has, for example, a voltage dividing circuit composed of the same number of resistors as the number of battery cells 10 constituting the block 11. Then, the equalization circuit equally divides the voltage across the block 11 by this voltage dividing circuit, and the feedback circuit using the operational amplifier provides the potential of the connection point of each battery cell 10 and the connection point of the voltage dividing resistor corresponding thereto. Each battery cell 10 is discharged using the discharge circuit 40 so that the potential matches. The configurations of the discharge circuit 40 and the equalization circuit are not limited to this, and other circuit configurations may be adopted.

  The block voltage detection unit 50 detects a voltage across the block 11, that is, a block voltage in which six battery cells 10 are connected in series. For this reason, the block voltage detection part 50 is connected to the positive electrode side of the battery cell 10 located on the highest voltage side in the block 11 and the negative electrode side of the battery located on the lowest voltage side. The block voltage detected by the block voltage detector 50 is output to the microcomputer 60.

  The microcomputer 60 includes a CPU, ROM, EEPROM, RAM, and the like (not shown), and monitors the state of the battery cell 10 and diagnoses a failure of the monitoring circuit 30 in accordance with a program stored in the ROM.

  The above is the overall configuration of the battery monitoring device 20 according to the present embodiment and the battery monitoring system including the battery monitoring device 20. As described above, a plurality of blocks 11 are actually connected in series, and a plurality of monitoring circuits 30 are connected to each block 11. Each monitoring circuit 30 is electrically connected to a common microcomputer 60. In FIG. 1, one block 11 and one monitoring circuit 30 are shown.

  Next, the monitoring operation of the battery monitoring device 20 according to the present embodiment, that is, the operation of overcharge / discharge detection will be described. The operation of monitoring the battery cell 10 in the battery monitoring device 20 is started, for example, when the battery monitoring device 20 is turned on or off, or when the battery monitoring device 20 receives an external command. The

  The overcharge / discharge detection function of the microcomputer 60 includes an overcharge detection mode and an overdischarge detection mode.

  First, overcharge detection will be described. In the battery monitoring device 20, when the overcharge detection mode is started, the microcomputer 60 outputs a threshold voltage corresponding to the overcharge detection threshold from the switching unit 31 of the monitoring circuit 30 corresponding to the battery cell 10 to be monitored. The switch 38 is switched as follows. Then, the comparator 33 compares the magnitude relationship between the threshold voltage corresponding to the overcharge detection threshold and the reference voltage, and the result is input from the comparator 33 to the microcomputer 60. The microcomputer 60 determines whether or not the voltage of the battery cell 10 is overcharged depending on whether each output of the comparator 33 is high level or low level.

  On the other hand, in the battery monitoring device 20, when the overdischarge detection mode is started, the microcomputer 60 outputs a threshold voltage corresponding to the overdischarge detection threshold from the switching unit 31 of the monitoring circuit 30 corresponding to the battery cell 10 to be monitored. The switch 38 is switched as described above. The comparator 33 compares the threshold voltage corresponding to the overdischarge detection threshold with the reference voltage, and the result is input from the comparator 33 to the microcomputer 60. The microcomputer 60 determines whether or not the voltage of the battery cell 10 is overdischarged depending on whether the output of the comparator 33 is high level or low level.

  As described above, the microcomputer 60 determines the states of the plurality of battery cells 10 based on the comparison result of the monitoring circuit 30.

  Next, the operation of failure diagnosis of the battery monitoring device 20 will be described with reference to FIG. FIG. 3 is a flowchart showing a flow of failure diagnosis of the battery monitoring device 20. Hereinafter, the failure diagnosis process will be described with reference to the flowchart shown in FIG. The failure diagnosis process is started, for example, when the battery monitoring device 20 is turned on or off, or when the battery monitoring device 20 receives an external command.

  First, when failure diagnosis processing is started, block voltage detection is performed in step 100. That is, the block voltage of the block 11 detected by the block voltage detection unit 50 is input to the microcomputer 60.

  In step 110, it is determined whether or not the block voltage varies, in other words, whether or not the block voltage variation is within a reference range. Here, “within reference range” means that the block voltage acquired in step 100 is within a certain range with respect to the block voltage acquired last time, or the minimum and maximum values of the block voltage for a certain period of time. This indicates a determination condition such that the difference is within an allowable range. Therefore, in this step, it is determined whether or not such a determination condition is satisfied.

  Then, when it is determined that the fluctuation of the block voltage is out of the reference range, that is, there is a fluctuation in the block voltage, the failure diagnosis ends. This is because when the block voltage varies and the block voltage is not stable, there is a possibility that the voltage of the battery cell 10 is largely varied, and accurate failure diagnosis cannot be performed. On the other hand, if it is determined that the fluctuation of the block voltage is within the reference range, that is, the block voltage is stable, the process proceeds to step 120.

  In step 120, failure diagnosis of the monitoring circuit 30 is executed. The failure diagnosis is performed as follows.

  First, the microcomputer 60 acquires the average value of the voltage of each battery cell 10 by dividing the block voltage acquired in step 100 by the number of battery cells 10 constituting the block 11.

  On the other hand, the microcomputer 60 switches the switch 38 of the switching unit 31 corresponding to the circuit for one battery cell 10 in the monitoring circuit 30 to relatively change the reference voltage in a plurality of stages and compare it with the battery voltage. That is, the microcomputer 60 switches the threshold value step by step from the first threshold value to the eighth threshold value by switching the switch 38 of the switching unit 31. Thereby, the comparator 33 compares the threshold voltage corresponding to each threshold value with the reference voltage, and each comparison result is input from the comparator 33 to the microcomputer 60. Then, the microcomputer 60 obtains the value of the battery voltage, which threshold value among the first threshold value to the eighth threshold value determines the magnitude relationship with the reference voltage from each comparison result.

  Then, the microcomputer 60 compares the average value of the battery cells 10 obtained from the block voltage with the battery voltage obtained from the monitoring circuit 30. If each value is within the normal range, there is no abnormality in the monitoring circuit 30, and if it is outside the normal range, it is detected that an abnormality has occurred in the monitoring circuit 30. In this way, the microcomputer 60 performs a failure diagnosis of the monitoring circuit 30.

  As described above, the failure diagnosis in step 120 is performed on the circuit for one battery cell 10 provided in the monitoring circuit 30.

  Next, in step 130, it is determined whether or not diagnosis of all battery cells 10 has been completed. In this step, when it is determined that the failure diagnosis of the monitoring circuit 30 for all the battery cells 10 is finished, the failure diagnosis is finished. On the other hand, if it is determined in this step that the failure diagnosis of the monitoring circuit 30 for all the battery cells 10 has not been completed, the process returns to step 100.

  If the block voltage is acquired again and the block voltage fluctuates, the failure diagnosis ends. If the block voltage does not fluctuate, the circuit of the monitoring circuit 30 for the battery cell 10 next to the battery cell 10 diagnosed above is obtained. Fault diagnosis is performed on

  That is, the microcomputer 60 inputs a block voltage from the block voltage detection unit 50 and performs a failure diagnosis after confirming that the fluctuation of the block voltage is within the reference range. Then, the microcomputer 60 confirms that the fluctuation of the block voltage input from the block voltage detection unit 50 is within the reference range, and then performs a fault diagnosis on one battery cell 10 constituting the block 11 in steps 100 to step 100. The operation 130 is repeated. In this way, failure diagnosis is performed.

  As described above, in the present embodiment, it is determined whether or not the block voltage has fluctuated before performing the fault diagnosis of the monitoring circuit 30, and when it has not fluctuated, the fault diagnosis is performed. It is characterized by not performing fault diagnosis.

According to this, since the microcomputer 60 performs the failure diagnosis in a state where the block voltage does not fluctuate, that is, in a state where the block voltage is stable, it is possible to prevent erroneous detection in the failure diagnosis. Therefore, the reliability of the failure diagnosis can be improved. In the present embodiment, the block voltage is detected before the monitoring circuit 30 performs the failure diagnosis of the circuit corresponding to one battery cell 10, and the voltage fluctuation is detected. Since it is confirmed that it is within the reference range, failure diagnosis can be performed in a state where the voltage of the battery cell 10 is stable.

  As for the correspondence between the description of the present embodiment and the description of the claims, the block voltage detection unit 50 corresponds to the “block voltage detection means” in the claims, and the monitoring circuit 30 claims Corresponds to “monitoring means”. The microcomputer 60 corresponds to “determination means” in the claims.

(Other embodiments)
In the above-described embodiment, whether or not the block voltage has changed is determined, and if it has not changed, a failure diagnosis of the circuit corresponding to one battery cell 10 is performed. However, this diagnosis method is an example. As described above, when a plurality of blocks 11 are provided, a plurality of block voltage detection units 50 and monitoring circuits 30 are provided for each of the plurality of blocks 11. In such a case, the microcomputer 60 responds to the block voltage detection unit 50 after confirming that the fluctuation of the block voltage of the block 11 input from one of the plurality of block voltage detection units 50 is within the reference range. For the monitored circuit 30, failure diagnosis of all the circuits corresponding to all the battery cells 10 monitored by the monitoring circuit 30 is performed. Thereafter, the block voltage is acquired for the monitoring circuit 30 corresponding to the next block voltage detection unit 50, and if the block voltage does not vary, the monitoring circuit 30 corresponding to the block voltage detection unit 50 is monitored by the monitoring circuit 30. You may make it repeat the operation | movement of performing failure diagnosis of all the circuits corresponding to all the battery cells 10 to be.

  In this way, failure diagnosis can be performed in units of the monitoring circuit 30. As described above, even when failure diagnosis is performed in units of the monitoring circuit 30, the block voltage is detected for each block 11 and it is confirmed that the voltage fluctuation is within the reference range, so that the block voltage is stable. Each fault diagnosis can be performed. Therefore, the reliability of failure diagnosis can be improved.

  In the above embodiment, one block 11 is provided so as to correspond to one monitoring circuit 30. That is, the block 11 is provided in units of the monitoring circuit 30. However, this is an example. For example, the block 11 may be set in a unit of a battery package in which a plurality of battery cells 10 are packaged in a predetermined number or a unit of a connection connector between the plurality of battery cells 10 and the battery monitoring device 20.

  As described above, in the battery package, the connection connector, etc., the block voltage fluctuation can be easily detected by detecting the block voltage for each unit in which the block voltage fluctuation is likely to occur. Therefore, the reliability of failure diagnosis can be improved.

  In each said embodiment, although the lithium ion secondary battery was demonstrated to the example as the battery cell 10, you may employ | adopt another secondary battery. Moreover, this secondary battery can be applied to a vehicle-mounted battery mounted on an electric vehicle such as a hybrid vehicle. Since such a vehicle-mounted battery is likely to fluctuate in voltage, the fault monitoring can be prevented by performing a fault diagnosis with the battery monitoring device 20 described above. The reliability of failure diagnosis can be improved in the battery monitoring device 20 used in a vehicle for which safety and reliability are desired.

  The circuit configuration of the monitoring circuit 30 shown in the above embodiment shows an example, and other circuit configurations may be used.

10 battery cells 11 blocks 30 monitoring circuit (monitoring means)
37 resistor 38 switch 50 block voltage detector (block voltage detector)
60 Microcomputer (determination means)

Claims (5)

A battery monitoring device for monitoring the state of a plurality of battery cells connected in series,
Block voltage detecting means for detecting a block voltage at both ends of the plurality of battery cells connected in series;
Monitoring means for inputting the battery voltage at both ends of the battery cell for each of the plurality of battery cells, comparing the battery voltage with a threshold value, and outputting the comparison result;
While determining the state of each of the plurality of battery cells based on the comparison result of the monitoring unit, the threshold value of the monitoring unit is relatively changed in a plurality of stages for each of the plurality of battery cells and compared with the battery voltage. Determination means for performing failure diagnosis for detecting an abnormality of the monitoring means based on the comparison result,
The battery monitoring apparatus, wherein the determination unit inputs the block voltage from the block voltage detection unit and performs the failure diagnosis after confirming that the fluctuation of the block voltage is within a reference range.   When the determination unit finishes the failure diagnosis of the monitoring unit relating to one battery cell, the block voltage is input from the block voltage detection unit, and after confirming that the fluctuation of the block voltage is within a reference range, The battery monitoring apparatus according to claim 1, wherein a failure diagnosis of the monitoring unit relating to the next battery cell is performed. When a unit that divides the plurality of battery cells every predetermined number is a block, a plurality of the blocks are set,
The block voltage detection means and the monitoring means are provided corresponding to each of the plurality of blocks,
When the determination unit finishes the failure diagnosis of the monitoring unit related to one block, the block voltage is input from the block voltage detection unit related to the next block, and the fluctuation of the block voltage is within a reference range. The battery monitoring apparatus according to claim 1, wherein after the confirmation, a failure diagnosis of the monitoring unit according to a next block is performed.   The plurality of battery cells are modularized at least in any unit of the monitoring unit, a battery package in which the plurality of battery cells are packaged, and a connection connector between the plurality of battery cells and the monitoring unit. The battery monitoring device according to claim 1, wherein the battery monitoring device is provided. The monitoring means has a plurality of resistors and a plurality of switches for dividing the voltage of the battery cell,
5. The determination unit according to claim 1, wherein the determination unit switches the plurality of switches to divide the voltage of the battery cell by the plurality of resistors to relatively change the threshold value in a plurality of stages. The battery monitoring device according to one.

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