JP2017219430A - Battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery system capable of determining the presence or absence of an inner resistance abnormality of a battery cell in a shorter time.SOLUTION: A battery system 10 includes: a battery module 12 constructed by series-connecting two or more battery cells Cn; circuits TCn for inspection connected in parallel to the battery cell Cn each including a switch SWn for inspection and a resistor ERn for inspection series-connected each other; a voltage detection circuit 22 for detecting a whole voltage value of the battery module 12 as a module voltage value; and a control device 16 for determining that a resistance abnormality is generated on the battery cell Cn corresponding to the turned-on switch SWn for inspection when a variation between a module voltage value when a whole switch SWn for inspection is turned off and the module voltage value when the switch SWn for inspection of a part of the inspection circuit is turned on is equal to or more than a predefined standard change.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery system including a battery module configured by connecting two or more battery cells in series, and more particularly to a battery system having a function of inspecting a resistance abnormality of the battery cell.

  2. Description of the Related Art Conventionally, a battery module configured by connecting a plurality of battery cells made of a chargeable / dischargeable secondary battery such as a lithium ion secondary battery in series is known. In such a battery module, it is known that the internal resistance of the battery cell gradually increases due to aging and the like. When the internal resistance increases, the voltage drop when a current flows through the battery cell increases, and the battery cell easily reaches the lower limit voltage. As a result, deterioration of the battery cell is promoted, and the performance of the battery module is reduced. Thus, a technique for inspecting the presence or absence of resistance abnormality, in which the internal resistance of the battery cell is significantly increased, has been proposed.

JP 2013-118757 A JP 11-259190 A

  For example, Patent Document 1 is an assembled battery control device including a plurality of unit cells, and includes an adjustment unit that adjusts the voltages of the plurality of unit cells to a predetermined target value, and is based on an adjustment time by the adjustment unit. Thus, a technique for determining abnormality of a single cell is disclosed. That is, the adjustment of the voltage of the unit cell is performed by discharging the unit cell and dropping the voltage to a predetermined target voltage. When the internal resistance of the unit cell increases, the output current of the unit cell decreases, and the discharge time required for voltage drop increases. Therefore, when the time required for adjustment is long, it can be determined that a resistance abnormality in which the internal resistance of the unit cell has increased has occurred.

  However, the technique of Patent Document 1 has a problem in that it takes time to adjust the voltage in order to determine the presence or absence of resistance abnormality, and it takes time to complete the determination of resistance abnormality.

  Therefore, an object of the present invention is to provide a battery system that can determine whether there is an abnormality in internal resistance of a battery cell in a shorter time.

  The battery system of the present invention is a battery module in which two or more battery cells are connected in series, and a test circuit provided for each of the one or more battery cells and connected in parallel to the one or more battery cells. Each of a test circuit including a test switch and a test resistor connected in series with each other, a voltage detection means for detecting a voltage value of the entire battery module as a module voltage value, and all of the test circuits The amount of change between the off voltage value, which is the module voltage value when the inspection switch is turned off, and the on voltage value, which is the module voltage value when the inspection switch of one or more inspection circuits is turned on, And a control device that determines that a resistance abnormality has occurred in the battery cell corresponding to the inspection switch that has been turned on when the reference change amount is greater than or equal to a predetermined amount. That.

  In a preferred aspect, the resistance abnormality determination process is performed when the current flowing through the battery module is zero. In this case, the battery system is an in-vehicle battery system mounted on an electric vehicle, and the control device determines whether or not a current flowing through the battery module is zero based on an operating state of the electric vehicle. It is desirable to do.

  In another preferred aspect, the resistance abnormality determination process is performed even when a current flowing through the battery module is not zero, and the control device sets a time for turning on the inspection switch to the battery module. Is made shorter than the time required for the current to flow through the reference change amount.

  In another preferred aspect, the control device determines whether or not a change amount between the off-voltage value and an on-voltage value when a plurality of battery cells are simultaneously turned on is equal to or greater than the reference change amount, and the change amount. Is equal to or greater than the reference change amount, it is further determined whether or not the difference amount between the on-voltage value and the off-voltage value when the plurality of battery cells are individually turned on is the reference change amount, and the determination result The battery cell in which the resistance abnormality has occurred is identified based on the above.

  In another preferred aspect, the voltage detection means includes a flying capacitor circuit.

  According to the present invention, the presence or absence of resistance abnormality is determined based on the amount of change between the module voltage value when all the inspection switches are turned off and the module voltage value when some of the inspection switches are turned on. Yes. Therefore, time for adjusting the voltage to a desired value is not required, and it is possible to determine the presence or absence of resistance abnormality in a short time as compared with the prior art.

It is a figure which shows the structure of the battery system which is embodiment of this invention. It is a schematic diagram which shows a certain battery cell and a circuit for a detection. It is a figure which shows the relationship between a module electric current value and a module voltage value. It is a flowchart which shows the flow of an inspection of presence or absence of resistance abnormality. It is a flowchart which shows the flow of the presence or absence inspection of resistance abnormality. It is a figure which shows the structure of another battery system. It is an image figure which shows the other example of resistance presence / absence determination processing. It is a flowchart which shows the flow of the determination process of FIG. It is a table | surface which shows an example of the switching order of ON / OFF of the switch for an inspection, and the variation | change_quantity at that time.

  Hereinafter, the battery system 10 which is embodiment of this invention is demonstrated with reference to drawings. FIG. 1 is a diagram showing a configuration of a battery system 10 according to an embodiment of the present invention. The battery system 10 is mounted on an electric vehicle (for example, a hybrid vehicle or an electric vehicle) and includes a battery module 12 that can be charged and discharged. The battery module 12 is configured by connecting a plurality of chargeable / dischargeable battery cells Cn (n = 1, 2,..., Max) in series. In the following, the number of battery cells Cn is described as six (that is, max = 6), but the number of battery cells Cn is not particularly limited, and may be less than six or more than six. Each battery cell Cn is a chargeable / dischargeable secondary battery, such as a lithium ion secondary battery. Each battery cell Cn has a unique internal resistance value rn. A resistance Ern in FIG. 1 indicates the internal resistance value rn.

  Each battery cell Cn is connected to an inspection circuit TCn for inspecting the internal resistance value rn of the battery cell Cn. The inspection circuit TCn includes an inspection resistor ERn and an inspection switch SWn connected in series. In the present embodiment, the plurality of inspection resistors ERn and inspection switches SWn are mounted in one IC 14. The resistance values Rn of the plurality of inspection resistors ERn are all the same. The inspection switch SWn is turned on / off by a control signal from the control device 16 described later.

  A current value Ib flowing through the battery module 12 is detected by a current sensor 18 connected to the battery module 12. The detected module current value Ib is converted into a digital signal by the A / D converter 20 and then sent to the control device 16.

  A voltage detection circuit 22 is further connected in parallel to the battery module 12. The voltage detection circuit 22 is a circuit that detects the voltage value of the entire battery module 12, that is, the module voltage value Vm. Although various configurations of the voltage detection circuit 22 can be considered, in this embodiment, the voltage detection circuit 22 is configured using the flying capacitor circuit 24. The flying capacitor circuit 24 is a circuit in which switches SWf and SWr are provided before and after the capacitor C. When detecting the module voltage value Vm, the first-stage switch SWf is turned on, the second-stage switch SWr is turned off to charge the capacitor C, the first-stage switch SWf is turned off, and the second-stage switch SWr is turned on. The voltage value charged in C is output as a module voltage value Vm via the comparator 28. The A / D converter 26 converts the module voltage value Vm output from the comparator 28 into a digital signal, and sends the digital signal to the control device 16.

  The control device 16 outputs drive signals to the switches SWn, SWf, SWr and the A / D converters 20, 26, and controls their drive. The control device 16 includes, for example, a CPU and a memory. The CPU performs various calculations. In the memory, a control program and various control parameters are stored in advance. Further, the detected current value and voltage value are temporarily stored in the memory. Among the control parameters stored in the memory are a reference change amount ΔVref, which will be described later. Such a control apparatus 16 may be comprised as a single apparatus, and may be comprised with the several apparatus which can communicate with each other.

  The control device 16 also determines whether or not there is a resistance abnormality in the battery cell Cn based on the module voltage value Vm sent from the A / D converter 26. That is, each battery cell Cn has a unique internal resistance value rn. The internal resistance value rn increases due to aging of the battery cell Cn. When the internal resistance value rn becomes excessively large, a voltage drop when a current flows through the battery cell Cn increases, and the battery cell Cn easily reaches the lower limit voltage. In order to avoid such a problem, the state in which the internal resistance value rn is excessively large, that is, the presence or absence of a so-called resistance abnormality is determined, and if necessary, the charge / discharge power Win, Wout is limited or the battery cell Cn It is necessary to exchange. Therefore, the control device 16 determines the presence or absence of resistance abnormality for each battery cell Cn based on the module voltage value Vm. Hereinafter, this resistance abnormality determination will be described.

  The voltage value of the entire module, that is, the module voltage value Vm is a total value of the voltage values Vcn at both ends of each battery cell Cn (hereinafter referred to as “terminal voltage Vcn”). That is, in the example of FIG. 1, Vm = Vc1 + Vc2 + ... + Vc6. Here, the voltage Vcn between the terminals decreases when the inspection switch SWn of the corresponding inspection circuit TCn is switched from OFF to ON. When the inter-terminal voltage Vcn decreases, the module voltage value Vm also decreases. When the resistance values Rn of the plurality of test resistors ERn are equal to each other, the decrease amount (change amount ΔV) increases as the internal resistance value rn increases.

  This will be described with reference to FIG. FIG. 2 is a schematic diagram showing a certain battery cell Cn and a test circuit TCn connected in parallel to the battery cell Cn. When the inspection switch SWn is switched from OFF to ON, the current flowing through the battery cell Cn increases or decreases, and the inter-terminal voltage Vcn changes by ΔV. The amount of change ΔV is determined by the divided voltage value of the internal resistance value rn of the battery cell Cn and the resistance value Rn of the inspection resistor ERn. That is, when the potential difference of the battery cell Cn is VOn, the voltage between terminals Vcn = VOn when the inspection switch SWn is off. On the other hand, when the inspection switch SWn is on, the terminal voltage Vcn = VOn · Rn / (rn + Rn). Accordingly, the change amount ΔV of the inter-terminal voltage Vcn when the inspection switch SWn is switched from OFF to ON is ΔV = VOn · rn (rn + Rn), and the change amount ΔV increases as the internal resistance value rn increases.

  FIG. 3 is a diagram illustrating the relationship between the module current value Ib and the module voltage value Vm. In FIG. 3, a solid line indicates a module voltage value when all the inspection switches SWn are turned off (hereinafter referred to as “off voltage value Vm_off”), and a broken line indicates a module when some of the inspection switches SWn are turned on. The voltage value (hereinafter referred to as “ON voltage value Vm_on”) is shown. A thick line indicates a module voltage value when there is no internal resistance abnormality, and a thin line indicates a module voltage value when there is an internal resistance abnormality.

  As is apparent from FIG. 3, the module voltage value Vm decreases as the module current value Ib increases. Regardless of whether there is a resistance abnormality, when the inspection switch SWn is turned on, the module voltage value Vm decreases. However, the amount of decrease (change amount ΔV2) when there is a resistance abnormality is larger than the amount of decrease (change amount ΔV1) when there is no resistance abnormality. In this embodiment, the presence / absence determination of the internal resistance is performed using this principle.

  FIG. 4 and FIG. 5 are flowcharts showing the flow of inspection for presence / absence of resistance abnormality. In the present embodiment, the presence / absence inspection of the resistance abnormality is performed in principle when the module current value Ib is zero, that is, when the battery system 10 is not used. This is because the module voltage value Vm changes according to the module current value Ib as shown in FIG. In order to accurately determine whether or not there is a resistance abnormality, it is necessary to acquire the change amount ΔV in a state where the change in the module voltage value Vm due to the change in the module current value Ib has not occurred. Therefore, the control device 16 monitors the module current value Ib (S10), and determines whether or not the module current value Ib is zero (S12). As a result of the determination, when the module current value Ib exceeds zero, the control device 16 stands by without performing the presence / absence determination of resistance abnormality. On the other hand, when the module current value Ib is zero, the control device 16 executes resistance abnormality determination processing (S14).

  In the resistance abnormality determination process, the control device 16 first turns off all the inspection switches SWn (S20). In this state, the module voltage value output from the voltage detection circuit 22 is acquired as the off-voltage value Vm_off (S22). Next, the control device 16 initializes the cell number n, that is, sets n = 1 (S24). Subsequently, the control device 16 outputs a control signal for turning on the n-th inspection switch SWn to the IC 14 (S26). When the n-th inspection switch SWn is turned on, the control device 16 acquires the module voltage value Vm output from the voltage detection circuit 22 as the on-voltage value Vm_on in that state (S28).

  Next, the control device 16 calculates a difference value (Vm_off−Vm_on) between the OFF voltage value Vm_off and the ON voltage value Vm_on as the change amount ΔV (S30). If the change amount ΔV can be calculated, the change amount ΔV is then compared with a reference change amount ΔVref stored in advance in the memory (S32). The reference change amount ΔVref is a value obtained in advance by an experiment or a simulator. The reference change amount ΔVref is a value obtained by adding a slight allowable error amount to the voltage change amount that can occur when the inspection switch SWn is switched off / on when the internal resistance value rn of the battery cell Cn is a normal value. It is. This reference change amount ΔVref may be a fixed value, or may vary depending on the temperature and the state of the battery module 12 (for example, the elapsed time since the start of use, the assumed material deterioration degree of the battery cell Cn, etc.). It may be a value.

  As a result of the comparison, when the change amount ΔV is equal to or less than the reference change amount ΔVref, the control device 16 determines that the internal resistance value rn of the nth battery cell Cn is normal (S34). On the other hand, when the change amount ΔV is larger (excess) than the reference change amount ΔVref, the control device 16 determines that the internal resistance value rn of the nth battery cell Cn is abnormal (S36). In this case, the control device 16 stores a flag indicating that in the memory. And a warning is notified to a user as needed, and the charging / discharging electric power of the battery module 12 is restrict | limited.

  If the presence or absence of resistance abnormality can be determined for one battery cell Cn, the control device 16 determines whether or not the cell number n has reached the maximum value max (S38). If the cell number n is less than the maximum value max as a result of the determination, the cell number n is incremented (S39), and steps S26 to S38 are repeated. When the cell number n reaches the maximum value max, the abnormality determination process ends.

  As is clear from the above description, in this embodiment, the presence or absence of resistance abnormality is determined based on the change amount ΔV of the module voltage value Vm when the inspection switch SWn is switched from OFF to ON. In other words, since it is not necessary to adjust the voltage value of the battery cell Cn, the time required for determining whether there is a resistance abnormality can be reduced as compared with the conventional technique such as Patent Document 1.

  In the present embodiment, the presence / absence of resistance abnormality is determined not based on the change amount of the inter-terminal voltage Vcn of each battery cell Cn but on the change amount of the module voltage value Vm. Therefore, unlike Patent Document 2, it is not necessary to provide the voltage detection circuit 22 for each battery cell Cn, and the circuit configuration can be simplified and the cost can be reduced. Also, as in Patent Document 2, when determining the presence or absence of resistance abnormality based on the amount of change in the inter-terminal voltage Vcn of each battery cell Cn, the inspection switch SWn is turned off for each battery cell Cn. It is necessary to acquire the module voltage value Vm when the module voltage is turned on and the module voltage value Vm when the module voltage is turned on. In other words, in this case, in order to determine resistance abnormality of max battery cells Cn, it is necessary to detect the voltage value (2 × max) times. On the other hand, in the present embodiment, as is clear from the above description, the module voltage value Vm (off voltage value Vm_off) when the inspection switch SWn is turned off only needs to be acquired once, so (1 + max) times only. What is necessary is just to detect a voltage value. Therefore, according to the present embodiment, it is possible to determine the presence / absence of resistance abnormality in a short time compared to the case where the presence / absence of resistance abnormality is determined based on the change amount of the inter-terminal voltage Vcn of each battery cell Cn. .

  The configuration described so far is merely an example, and a resistance abnormality is caused based on a change amount ΔV of the module voltage value between when all the inspection switches SWn are turned off and when some of the inspection switches SWn are turned on. As long as it is determined whether or not there is, other configurations may be changed as appropriate. For example, in the present embodiment, the module voltage value Vm is detected using the flying capacitor circuit 24, but the voltage detection circuit 22 may be changed as appropriate. For example, as shown in FIG. 6, the module voltage value Vm may be detected by a normal operation amplification circuit 30. In this case, the voltage detection time can be shortened as compared with the voltage detection circuit 22 using the flying capacitor circuit 24.

  In the above description, one inspection circuit TCn is provided for one battery cell Cn. However, one inspection circuit TCn may be provided for every two or more battery cells Cn. For example, as shown in FIG. 6, one test circuit TC1, TC2 is connected in parallel to three battery cells (C1, C2, C3), (C4, C5, C6) arranged in series. It is good. In this case, the specific range of the battery cell Cn having a resistance abnormality is expanded. That is, if the change amount ΔV becomes large before and after the first inspection switch SW1 is switched off / on, it is understood that there is a resistance abnormality in the first to third battery cells C1, C2, and C3. It is not possible to specify which of the first to third battery cells C1, C2, C3 has a resistance abnormality. However, in this case, since the elements constituting the inspection circuit TCn can be further reduced, the cost can be further reduced.

  In the configuration of FIG. 1, the module current value Ib is determined based on the detection value of the current sensor 18. However, the module current value Ib may be determined based on another control signal instead of the detection value of the current sensor 18. For example, in the case of the battery module 12 mounted on a vehicle, a system main relay is provided between the battery module 12 and an external circuit. Normally, when the system main relay is off, the current value Ib flowing through the battery module 12 is zero. Therefore, it may be determined whether or not the module current value Ib is zero based on a signal indicating the operating state of the electric vehicle, such as a control signal for driving the system main relay.

  Further, in the above-described embodiment, in order to eliminate the influence of the fluctuation of the module voltage value Vm caused by the fluctuation of the module current value Ib, the presence / absence determination of the resistance abnormality is performed only when Ib = 0. However, if the off-voltage value Vm_off and the on-voltage value Vm_on can be acquired at intervals sufficiently shorter than the time when the module current value Ib changes, the presence / absence of resistance abnormality may be determined when Ib ≠ 0. FIG. 7 is an image diagram showing this resistance abnormality presence / absence determination process. In FIG. 7, the upper part shows the module current value Ib, the middle part shows the drive timing of the test switch SWn, and the lower part shows the module voltage value Vm.

  As shown in FIG. 7, in this case, the on-voltage value Vm_on is acquired immediately after the off-voltage value Vm_off is acquired. Therefore, unlike the above-described embodiment, in this case, it is necessary to acquire the off voltage value Vm_off and the on voltage value Vm_on for each battery cell Cn. With such a configuration, the time from when the off voltage value Vm_off is acquired to when the on voltage value Vm_on is acquired can be sufficiently shortened compared to the change speed of the module current value Ib. As a result, the influence of the change in the module current value Ib in the change amount ΔV can be reduced, and whether or not there is a resistance abnormality can be determined when Ib ≠ 0. In the example of FIG. 7, it can be determined that the fourth battery cell C4 having the large change amount ΔV of the module current value has a resistance abnormality.

  FIG. 8 is a flowchart showing a flow of resistance abnormality presence / absence determination processing in this case. As shown in FIG. 8, in this case, the control device 16 first initializes the cell number n (that is, sets n = 1) (S40). Subsequently, the control device 16 turns off all the inspection switches SWn (S42), and acquires the module voltage value Vm detected in that state as the off-voltage value Vm_off (S44). If the off-voltage value Vm_off can be acquired, the control device 16 turns on the n-th inspection switch SWn before the module current value Ib changes greatly (S46). Then, the module voltage value Vm detected in this state is acquired as the ON voltage value Vm_on (S48). If the off voltage value Vm_off and the on voltage value Vm_on are obtained, the control device 16 calculates the difference value between them as the change amount ΔVn (S50). Then, the control device 16 compares the obtained change amount ΔVn with the reference change amount ΔVref stored in the memory (S52). As a result of the comparison, when the change amount ΔVn is equal to or less than the reference change amount ΔVref, the control device 16 determines that the internal resistance value rn of the nth battery cell Cn is normal (S54). On the other hand, when the change amount ΔVn exceeds the reference change amount ΔVref, the control device 16 determines that the internal resistance value rn of the nth battery cell Cn is abnormal (S56).

  If the presence or absence of resistance abnormality can be determined for one battery cell Cn, the control device 16 determines whether or not the cell number n has reached the maximum value max (S58). If the cell number n is less than the maximum value max as a result of the determination, the cell number n is incremented (S60), and steps S42 to S58 are repeated again. When the cell number n reaches the maximum value max, the abnormality determination process ends.

  As described above, if the time difference between the acquisition timing of the off voltage value Vm_off and the acquisition timing of the on voltage value Vm_on can be shortened, it is possible to determine whether there is a resistance abnormality even if Ib ≠ 0. As a result, more opportunities for determining the presence or absence of resistance abnormality can be obtained.

  In the above description, only the example in which the inspection switches SWn are turned on one by one has been described. However, a plurality of inspection switches SWn may be turned on simultaneously. FIG. 9 is a table showing an example of the switching order of the inspection switch SWn in the configuration of FIG. 1 and the change amount ΔV at that time. As shown in FIG. 9, in the first time, all the inspection switches SWn are turned off to obtain the off voltage value Vm_off. Subsequently, in the second time, the first and second inspection switches SW1 and SW2 are turned on, in the third time, the third and fourth inspection switches SW3 and SW4 are turned on, and in the fourth time, The fifth and sixth inspection switches SW5 and SW6 are turned on to detect the on-voltage value Vm_on. Then, a difference value between the off voltage value Vm_off obtained at the first time and the on voltage value Vm_on obtained at the second to fourth times is calculated as the change amount ΔV. As a result, it is assumed that the change amount ΔV obtained for the second time and the third time is smaller than the reference change amount ΔVref, and the change amount ΔV obtained for the fourth time is larger than the reference change amount ΔVref. In this case, it can be determined that the fifth battery cell C5 or the sixth battery cell C6 has a resistance abnormality. Therefore, in this case, the control device 16 turns on only the fifth inspection switch SW5 and acquires the on-voltage value Vm_on at that time. Then, the difference value between the obtained on-voltage value Vm_on and the first-off voltage value Vm_off is calculated as the change amount ΔV. As shown in FIG. 9, when the change amount ΔV obtained at the fifth time is smaller than the reference change amount ΔVref, it can be determined that the sixth battery cell C6 has a resistance abnormality. On the other hand, if the change amount ΔV obtained for the fifth time is larger than the reference change amount ΔVref, it can be determined that the fifth battery cell C5 has a resistance abnormality. In this case, it can be seen that the fifth battery cell C5 has a resistance abnormality, but it cannot be determined whether or not the sixth battery cell C6 has a resistance abnormality. Therefore, when the fifth change amount ΔV is larger than the reference change amount ΔVref, the sixth voltage detection is also performed after the sixth inspection switch SW6 is turned on.

  As is apparent from the above description, in the case of FIG. 9, the battery cell Cn with abnormal resistance can be identified by detecting the module voltage value Vm five or six times. Therefore, the number of times of voltage detection can be reduced and the time for resistance abnormality determination processing can be further reduced as compared with the case where the inspection switches SWn are switched on / off one by one.

  DESCRIPTION OF SYMBOLS 10 Battery system, 12 Battery module, 16 Control apparatus, 18 Current sensor, 20, 26 A / D converter, 22 Voltage detection circuit, 24 Flying capacitor circuit, 28 Comparator, 30 Operation amplification circuit, C capacitor, Cn Battery cell, ERn Inspection resistance, Ern internal resistance, Ib module current value, SWn inspection switch, TCn inspection circuit.

Claims (6)

A battery module in which two or more battery cells are connected in series;
A test circuit provided for each of one or more battery cells and connected in parallel to the one or more battery cells, each including a test switch and a test resistor connected in series with each other An inspection circuit;
Voltage detection means for detecting the voltage value of the entire battery module as a module voltage value;
An off-voltage value that is the module voltage value when the inspection switches of all the inspection circuits are turned off, and an on-voltage value that is the module voltage value when the inspection switches of one or more inspection circuits are turned on A control device that determines that a resistance abnormality has occurred in the battery cell corresponding to the turned-on test switch when the amount of change is equal to or greater than a predetermined reference change amount;
A battery system comprising: The battery system according to claim 1,
The battery abnormality determination process is performed when the current flowing through the battery module is zero. The battery system according to claim 2,
The battery system is an in-vehicle battery system mounted on an electric vehicle,
The said control apparatus determines whether the electric current which flows into the said battery module is zero based on the operation state of the said electric vehicle. The battery system according to claim 1,
The resistance abnormality determination process is performed even when the current flowing through the battery module is not zero,
The control device makes the time for turning on the inspection switch shorter than the time when the current flowing through the battery module changes by the reference change amount,
A battery system characterized by that. The battery system according to any one of claims 1 to 4,
The control device determines whether the amount of change between the off-voltage value and the on-voltage value when a plurality of battery cells are simultaneously turned on is greater than or equal to the reference variation, and the variation is greater than or equal to the reference variation. In this case, it is further determined whether or not a difference amount between the on-voltage value and the off-voltage value when the plurality of battery cells are individually turned on is the reference change amount, and a resistance abnormality occurs based on the determination result. A battery system characterized by specifying a battery cell. The battery system according to any one of claims 1 to 5,
The battery system, wherein the voltage detection means includes a flying capacitor circuit.

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