CN108931725A - A kind of method and device of battery failures detection - Google Patents

Abstract

The embodiment of the present invention discloses a battery fault detection method and device. The method includes: when a cell voltage inconsistency fault occurs in the battery pack to be tested, determine the total voltage of the battery pack to be tested and the voltage of each cell contained in the battery pack to be tested. The first difference of the sum of the cell voltages of the battery; the second difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of each cell before the cell voltage inconsistency fault occurs in the battery pack to be tested ; If the difference between the first difference and the second difference is greater than the preset voltage threshold, it is determined that a voltage measurement failure occurs in the battery pack to be tested; otherwise, it is determined that a short circuit fault occurs in the battery pack to be tested or Contact resistance fault; wherein, the differential voltage of any single cell is the difference between the single cell voltage of the single cell and the average value of the single cell voltages of each single cell. Adopting the embodiment of the present invention has the advantages of improving the accuracy of battery fault detection and enhancing the applicability of battery fault detection.

Description

Method and device for battery fault detection

technical field

The invention relates to the field of battery management, in particular to a battery fault detection method and device.

Background technique

At present, with the increasing environmental problems such as smog weather, greenhouse effect, and energy crisis, people's awareness of sustainable development is gradually increasing, and sustainable energy products such as electric vehicles are also becoming more and more popular. The energy storage device of electric vehicles is a battery system, which mainly includes the integration of battery cells or battery modules, battery management systems, high/low voltage circuits, and cooling devices. In recent years, there have been many safety accidents such as spontaneous combustion of electric vehicles at home and abroad. Most of the safety accidents such as spontaneous combustion of electric vehicles are caused by the failure of the battery system. During the operation of the battery system of electric vehicles, failures such as sudden battery cell voltage inconsistency may occur, that is, the voltage of a certain battery cell is obviously inconsistent with the voltage of other battery cells. There are multiple reasons for battery faults such as sudden battery cell voltage inconsistencies. If the user cannot determine the cause of the fault in the battery system, he cannot take corresponding measures to solve the fault, and thus cannot avoid safety accidents such as spontaneous combustion of electric vehicles caused by battery faults. .

The existing technology collects or monitors battery parameters such as the terminal voltage, electromotive force, output current of a single battery, or equivalent internal resistance of a single battery in a battery system. The defined standard parameters are compared to determine whether the battery system is faulty through the comparison of parameters. For example, the existing technology calculates the equivalent internal resistance Z _i of each single cell by collecting the terminal voltage U _i of each single cell in the secondary battery pack and the output current I of the single cell, and through Z _i and The difference ΔZ _i of the reference resistance determines whether a micro-short circuit occurs in the single cell. Wherein, the reference resistance is the average value of the equivalent internal resistances of all single cells in the battery pack. If the number of single cells connected in series in the battery pack is large, the workload of collecting or monitoring the battery parameters of each single cell in the prior art is large, and the implementation is difficult. In addition, with the aging of the battery pack, the inconsistency of each single battery in the battery pack will increase. When using battery parameters such as ΔZ _i value to judge the micro-short circuit of the battery, it is easy to judge the inconsistency of the battery as a micro-short circuit, and it is easy to judge the contact resistance The internal resistance change caused by other faults is falsely reported as a micro-short circuit, and the probability of misjudgment is high. The existing technology cannot distinguish battery failures caused by different reasons, and has poor applicability.

Contents of the invention

The present application provides a battery fault detection method and device, which can improve the detection accuracy of battery fault sources, enhance the applicability of battery fault detection, and reduce the misjudgment rate of battery faults.

The first aspect provides a method for battery fault detection, which may include:

When a cell voltage inconsistency fault occurs in the battery pack to be tested, determine the first difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells contained in the battery pack to be tested;

Before the cell voltage inconsistency fault occurs in the battery pack to be tested, determine the second difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells;

If the difference between the first difference and the second difference is greater than a preset voltage threshold, it is determined that a voltage measurement failure occurs in the battery pack to be tested;

If the difference between the first difference and the second difference is less than or equal to the preset voltage threshold, then according to the difference voltages of the individual cells, it is determined that the battery pack under test has a short-circuit fault or Contact resistance failure;

Wherein, the differential voltage of any single cell is the difference between the cell voltage of any single cell and the average value of the cell voltages of each of the single cells.

It should be noted that the cell voltage inconsistency fault described in this application refers to the battery pack failure caused by the obvious inconsistency between the voltage of a certain cell (that is, the cell voltage) and the voltage of other cells in the battery pack. .

This application can determine whether the cause of the failure of the battery pack to be tested is the voltage according to the total voltage of the battery pack to be tested and the voltage of each single cell when the single cells in the battery pack to be tested have an inconsistent fault. Measurement failure. If the failure of the battery pack to be tested is not caused by a voltage measurement fault, it can also be determined whether the fault source of the battery pack to be tested is a short-circuit fault or a contact resistance fault according to the differential voltage of each single battery. The application can realize the prior diagnosis of the fault source of the battery pack to be tested, can improve the detection accuracy of the battery fault source, improves the applicability of the battery fault detection, and can further improve the safety of the battery.

With reference to the first aspect, in a first possible implementation manner, the method further includes:

Acquiring the cell voltage of each single cell in the battery pack to be tested at each of the preset N sampling moments;

Determining the differential voltages of the individual cells at each sampling moment, and determining that a cell voltage inconsistency fault occurs in the battery pack under test according to the differential voltages of the individual cells;

Wherein, the N is an integer greater than zero.

In the present application, by collecting the voltages of the single cells of the battery pack to be tested at multiple sampling moments, the differential voltage of each single cell at each sampling time can be determined. According to the differential voltage of the single cells, it can be determined that the battery pack under test has a single cell voltage inconsistent fault, which can improve the detection accuracy of the single cell voltage inconsistent faults of the battery pack to be tested, thereby improving the timeliness of battery fault detection and improving the battery life. The controllability of failure risk.

With reference to the first possible implementation of the first aspect, in the second possible implementation, the determination of the differential voltages of the individual cells at each sampling moment is determined according to the differential voltages of the individual cells. The failure of the battery pack under test to have a single voltage inconsistency includes:

Obtain the cell voltage of each cell in the battery pack to be tested at any sampling time k, and calculate the average value U _m of the cell voltage of each cell at the sampling time k;

Determine the difference voltage of each unit cell according to the cell voltage of each unit cell at the sampling time k and the difference value of U _m , and calculate the difference of the unit cell i with the largest absolute value of the difference voltage The voltage is determined as the maximum absolute difference voltage U _dmax,i at the sampling moment k;

If the _{Udmax recorded at consecutive N' sampling moments, i} is greater than the preset difference voltage threshold, then it is determined that the first _{Udmax greater than the preset difference voltage threshold occurs, and the battery pack under test occurs at the sampling moment m at which i} occurs Single voltage inconsistent fault;

Wherein, N' is an integer less than or equal to N.

The present application can pre-set the difference voltage threshold for determining the fault of inconsistent voltages of the cells of the battery pack, and can also record the maximum absolute difference voltage at each sampling moment. According to the maximum absolute difference voltage at each sampling time and the preset difference voltage threshold, the sampling time when the cell voltage is inconsistent can be determined, and then the source of the battery pack failure can be detected in time, the timeliness of fault detection can be improved, and the safety of the battery can be improved.

In combination with the second possible implementation of the first aspect, in the third possible implementation, when the battery pack under test has a voltage inconsistency fault, determine the total voltage of the battery pack under test and the voltage of the battery pack under test. Measuring the first difference of the sum of the cell voltages of the individual cells contained in the battery pack includes:

Determining the sampling time m at which the voltage inconsistency of the battery pack under test occurs, and obtaining the total voltage U _total1 of the battery pack under test at the sampling time m;

Acquiring the cell voltages of the individual cells included in the battery pack to be tested at the sampling time m, and calculating the sum U1 _of the cell voltages of the individual cells;

calculating the difference between U _total1 and U1, and determining the absolute value of the difference as the _first difference.

This application can determine the sampling time when the cell voltage inconsistency fault occurs in the battery pack, and then determine the total voltage of the battery pack at the sampling time and the sum of the cell voltages of each single cell in the battery pack, and then calculate the difference between the two The value is determined as a first difference value for determining the type of failure of the battery pack. The application can determine the source of the battery pack fault according to the battery parameters corresponding to the time when the cell voltage inconsistency occurs in the battery pack, which can reduce the misjudgment rate of fault detection and improve the applicability of the battery pack fault source detection.

With reference to the second possible implementation of the first aspect, in a fourth possible implementation, before the voltage inconsistency of the cells of the battery under test occurs, determine the total voltage of the battery under test and the individual The second difference of the sum of cell voltages of the cells includes:

Determining the sampling time m at which the voltage inconsistency of the cells in the battery pack under test occurs, and obtaining the total voltage U _total2 of the battery pack under test at the sampling time m1 before the sampling time m;

Acquiring the cell voltages of the individual cells included in the battery pack to be tested at the sampling time m1, and calculating the sum U2 of the cell voltages of the individual cells _;

calculating the difference between U _total2 and U ₂ , and determining the absolute value of the difference as the second difference.

The present application can determine the sampling time when the cell voltage inconsistent fault occurs in the battery pack, and then can determine the total voltage of the battery pack at a sampling time before the sampling time, and the sum of the cell voltages of each single cell in the battery pack, and then can The difference between the two is determined as the second difference, which is used to determine the fault type of the battery pack. This application can determine the source of the battery pack fault according to the battery parameters corresponding to the sampling time before the time when the cell voltage inconsistency of the battery fault occurs in the battery pack. Suitability for battery pack fault source detection.

In combination with the third possible implementation of the first aspect or the fourth possible implementation of the first aspect, in the fifth possible implementation, after determining that the battery pack under test has a voltage inconsistent fault , the method also includes:

Determining the voltage mutation value of the single battery with inconsistent voltage in the battery pack to be tested, and determining the preset voltage threshold according to the voltage mutation value;

Wherein, the voltage mutation value is the difference in cell voltage between the sampling time before the fault occurs and the sampling time after the fault occurs for the single battery whose voltage is inconsistent.

This application can determine the parameters used to determine the voltage measurement fault of the battery according to the voltage mutation value of the single cell when the battery pack has a single cell inconsistent fault, which can improve the accuracy of parameter selection and further reduce the cost of battery pack fault detection. false positive rate.

In combination with any one of the second possible implementation manner of the first aspect to the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner, according to the differential voltages of the individual cells, Determining that a short-circuit fault or a contact resistance fault occurs in the battery pack under test includes:

Determine the sampling time m at which the voltage inconsistency of the battery pack under test occurs, and calculate the first average absolute difference value U _MAD1 of the maximum absolute difference voltage at x1 sampling times before the sampling time m;

Calculating the second average absolute difference value U _MAD2 of the maximum absolute difference voltage at x2 sampling moments after the sampling moment m, wherein, the x2=x1=x, and the x is greater than or equal to (N-1)/2 ;

If the U _MAD2 is greater than or equal to the preset multiple threshold of the U _MAD2 , it is determined that the battery pack under test has a contact resistance fault, otherwise it is determined that the battery pack under test has a short circuit fault;

Among them, the calculation expression of the mean absolute difference value U _MAD is:

Among them, U _dmax,i(t) is the maximum absolute difference voltage at the sampling time t.

This application can record multiple maximum absolute difference voltages before and after the failure after determining that the voltage of the single cells of the battery group is inconsistent, and then determine the average absolute difference value of the maximum absolute difference voltage before and after the failure of the battery group . The application can determine whether the battery pack fault is a short-circuit fault or a contact resistance fault by comparing the average absolute difference values before and after the battery pack fault, thereby quickly realizing the diagnosis of the fault source of the battery pack monomer voltage inconsistency, and improving the accuracy of the battery pack fault detection applicability.

The second aspect provides a device for battery fault detection, which may include:

A determining module, configured to determine the first difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells contained in the battery pack to be tested when a cell voltage inconsistency fault occurs in the battery pack to be tested difference;

The determination module is further configured to determine the second difference between the total voltage of the battery pack to be tested and the sum of cell voltages of the individual cells before the cell voltage inconsistency fault occurs in the battery pack to be tested value;

A failure analysis module, configured to determine that a voltage measurement failure occurs in the battery pack under test when the determination module determines that the difference between the first difference and the second difference is greater than a preset voltage threshold;

The fault analysis module is further configured to, when the determination module determines that the difference between the first difference and the second difference is less than or equal to the preset voltage threshold, according to the Differential voltage, to determine that the battery pack under test has a short-circuit fault or a contact resistance fault;

Wherein, the differential voltage of any single cell is the difference between the cell voltage of any single cell and the average value of the cell voltages of each of the single cells.

With reference to the second aspect, in a first possible implementation manner, the device further includes:

An acquisition module, configured to acquire the cell voltage of each single cell in the battery pack to be tested at each sampling time among the preset N sampling times;

The determination module is further configured to determine the differential voltage of each single battery at each sampling time according to the single cell voltage acquired by the acquisition module, and determine the battery pack to be tested according to the differential voltage of each single battery Inconsistent fault of single voltage occurs;

Wherein, the N is an integer greater than zero.

With reference to the first possible implementation manner of the second aspect, in a second possible implementation manner, the device further includes a computing module;

The obtaining module is also used to obtain the cell voltage of each cell in the battery pack to be tested at any sampling time k;

The calculation module is used to calculate the average value U _m of the cell voltages of the individual cells at the sampling time k obtained by the acquisition module;

The determination module is configured to determine the cell voltage of each cell at the sampling time k obtained by the acquisition module and the difference between the U _m calculated by the calculation module. The differential voltage of the individual batteries, and the differential voltage of the single battery i with the largest absolute value of the differential voltage is determined as the maximum absolute differential voltage U _dmax,i at the sampling time k;

The determination module is also used to determine the first U dmax that is greater than the preset difference voltage threshold when the U _dmax recorded at consecutive N' sampling moments is greater than the preset difference voltage threshold. The sampling moment m _{where i} occurs The battery pack under test has a single voltage inconsistency fault;

Wherein, N' is an integer less than or equal to N.

With reference to the second possible implementation of the second aspect, in the third possible implementation, the determination module is configured to determine the sampling time m when the battery pack under test has an inconsistent voltage fault;

The obtaining module is also used to obtain the total voltage U _total1 of the battery pack under test at the sampling time m determined by the determining module;

The acquisition module is also used to acquire the cell voltage of each cell included in the battery pack under test at the sampling moment m;

The calculation module is used to calculate the sum U ₁ of the cell voltages of the individual cells, and calculate the difference between the U _total1 and the U ₁ ;

The determination module is configured to determine the absolute value of the difference calculated by the calculation module as the first difference.

With reference to the second possible implementation of the second aspect, in a fourth possible implementation, the determination module is configured to determine the sampling time m when the battery pack under test has an inconsistent fault of cell voltage;

The obtaining module is also used to obtain the total voltage U _total2 of the battery pack under test at the sampling time m1 before the sampling time m determined by the determining module;

The acquiring module is further configured to acquire the individual voltage of each individual battery contained in the battery pack under test at the sampling moment m1;

The calculation module is configured to calculate the sum U ₂ of the cell voltages of the individual cells obtained by the acquisition module, and calculate the difference between the U _total2 and the U ₂ ;

The determination module is configured to determine the absolute value of the difference calculated by the calculation module as the second difference.

In combination with the fourth possible implementation of the second aspect or the fourth possible implementation of the second aspect, in a fifth possible implementation, the determining module is further configured to:

Determining the voltage mutation value of the single battery with inconsistent voltage in the battery pack to be tested, and determining the preset voltage threshold according to the voltage mutation value;

Wherein, the voltage mutation value is the difference in cell voltage between the sampling time before the fault occurs and the sampling time after the fault occurs for the single battery whose voltage is inconsistent.

In combination with any one of the second possible implementation manner of the second aspect to the fifth possible implementation manner of the second aspect, in a sixth possible implementation manner, the determination module is configured to determine the Sampling time m at which a single voltage inconsistency fault occurs in the group;

The calculation module is used to calculate the first average absolute difference value U _MAD1 of the maximum absolute difference voltage at x1 sampling moments before the sampling moment m determined by the determination module;

The calculation module is also used to calculate the second average absolute difference value U _MAD2 of the maximum absolute difference voltage at x2 sampling moments after the sampling moment m, wherein, the x2=x1=x, and the x is greater than or Equal to (N-1)/2;

The fault analysis module is used to determine that the battery pack under test has a contact resistance fault when the U _MAD2 calculated by the calculation module is greater than or equal to the preset multiple threshold of the U _MAD2 , otherwise determine that the battery pack to be tested has a contact resistance fault. A short-circuit fault occurs in the battery pack;

Among them, the calculation expression of the mean absolute difference value U _MAD is:

Among them, U _dmax,i(t) is the maximum absolute difference voltage at the sampling time t.

In a third aspect, an embodiment of the present invention provides a terminal device, including: a memory and a processor;

The memory is used to store a set of program codes;

The processor is configured to call the program code stored in the memory to execute the method provided in the first aspect above.

In a fourth aspect, an embodiment of the present application provides a computer storage medium for storing computer software instructions used by the above-mentioned terminal device, which includes a program designed to execute the method provided by the above-mentioned first aspect.

This application can determine whether the cause of the failure of the battery pack to be tested is the voltage according to the total voltage of the battery pack to be tested and the voltage of each single cell when the single cells in the battery pack to be tested have an inconsistent fault. Measurement failure. If the failure of the battery pack to be tested is not caused by a voltage measurement fault, it can also be determined whether the fault source of the battery pack to be tested is a short-circuit fault or a contact resistance fault according to the differential voltage of each single battery. The application can realize the prior diagnosis of the fault source of the battery pack to be tested, and can improve the detection accuracy of the fault source of the battery. Further, the present application can record a plurality of maximum absolute difference voltages before and after the failure after determining that the voltage of the single cells of the battery group is inconsistent, and then determine the average of the maximum absolute difference voltages before and after the failure of the battery group Absolute difference value. This application can determine whether the battery pack fault is a short-circuit fault or a contact resistance fault by comparing the average absolute difference value before and after the battery pack fault, so as to quickly realize the diagnosis of the source of the battery pack monomer voltage inconsistency fault and improve the applicability of battery fault detection , thereby improving the safety of the battery.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without making creative efforts.

FIG. 1 is a schematic structural diagram of a battery fault detection system provided by an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a terminal device provided by an embodiment of the present invention;

Fig. 3 is a schematic flowchart of a method for detecting a battery fault provided by an embodiment of the present invention;

Fig. 4 is another schematic flow chart of the battery fault detection method provided by the embodiment of the present invention;

Fig. 5a is a schematic diagram of a battery cell voltage inconsistency fault provided by an embodiment of the present invention;

Fig. 5b is another schematic diagram of the battery cell voltage inconsistency fault provided by the embodiment of the present invention;

Fig. 6a is another schematic diagram of the battery cell voltage inconsistency fault provided by the embodiment of the present invention;

Fig. 6b is another schematic diagram of the battery cell voltage inconsistency fault provided by the embodiment of the present invention;

Fig. 7 is a schematic diagram of the average absolute difference U _MAD of the battery pack provided by the embodiment of the present invention;

Fig. 8 is a schematic structural diagram of a battery fault detection device provided by an embodiment of the present invention.

Detailed ways

The battery fault detection method provided by the embodiment of the present invention can be applied to a terminal device, and the above-mentioned terminal device can be built into an existing battery management system (battery management system, BMS), or can be a device including an existing BMS, The details can be determined according to the requirements of the actual application scenario, and there is no limitation here. The terminal equipment may also be called user equipment (user equipment, UE), mobile station (mobile station, MS), mobile terminal (mobile terminal), and so on. The above-mentioned terminal device may also be a mobile device such as a portable device, a pocket device, a handheld device, a computer built-in device, or a vehicle-mounted device. For example, the terminal device may be a mobile phone (or called a "cellular" phone), or a computer with a mobile nature, or an electric car, and so on. The embodiments of the present invention will be described by taking an electric vehicle as an example. It should be understood that, in addition to the terminal device, the method for detecting a battery failure provided by the embodiment of the present invention may also be applied to other devices using secondary batteries, which is not limited here. The battery cells (also known as single cells) with inconsistent cell voltages described in the embodiments of the present invention may be a single cell in a battery pack in series, or a single cell that works independently. The application scenario is determined, and there is no limitation here.

During the operation of the electric vehicle battery system, a sudden cell voltage inconsistency fault may occur, that is, the voltage of a certain cell is obviously inconsistent with the voltage of other cells. In the electric vehicle battery system, the reasons for the inconsistency of the voltage of the single cell mainly include: battery voltage measurement failure, contact resistance growth, battery short circuit, etc. When the fault sources of the electric vehicle battery system are different, different processing methods need to be adopted. For example, if the cell voltage inconsistency fault of the electric vehicle battery system is caused by a voltage measurement fault, the electric vehicle in motion can continue to drive normally to the repair place. If the fault of inconsistent cell voltage of the electric vehicle battery system is caused by the increase of contact resistance, the electric vehicle can "limp home" by limiting the power. If the fault of inconsistent cell voltage of the electric vehicle battery system is a short circuit of the battery, then Therefore, when the electric vehicle battery system fails, how to identify the fault source of the electric vehicle battery system, such as voltage measurement fault, contact resistance fault or short circuit fault, is one of the important problems to be solved urgently to improve the safety of electric vehicles .

Referring to FIG. 1 , it is a schematic structural diagram of a battery fault detection system provided by an embodiment of the present invention. The battery fault detection system provided by the embodiment of the present invention may be the battery fault detection system contained in the above-mentioned terminal equipment, or it may be a battery fault detection system built in the existing BMS, which may be determined according to the actual application scenario, and will not be described here. Do limit. The battery fault detection system provided by the embodiment of the present invention includes a battery pack to be tested, a monitoring management unit, a fault analysis unit, and the like. Wherein, the above-mentioned monitoring and management unit may specifically be an existing BMS or a relevant monitoring and management unit included in the BMS, which may be determined according to an actual application scenario, and is not limited here. The above-mentioned monitoring and management unit can be used to record the working state data of the battery pack to be tested and the single cells contained therein in real time during the working process of the battery pack, including the terminal voltage of the battery pack to be tested at each voltage sampling moment (that is, the output voltage of the battery pack) Voltage, also known as the total voltage of the battery pack) and battery parameters such as the cell voltage of each single cell in the battery pack to be tested. The above fault analysis unit is used to monitor various battery parameters detected by the management unit to determine the fault source of the battery pack under test, such as voltage measurement fault, contact resistance fault or short circuit fault. Further, the fault analysis unit can feed back the detected fault source of the battery pack to the monitoring management unit, store, record and/or feed back to the user through the monitoring management unit.

The method and device for battery fault detection provided by the embodiments of the present invention will be described in detail below with reference to FIGS. 2 to 8 .

Referring to FIG. 2 , it is a schematic structural diagram of a terminal device provided by an embodiment of the present invention. As shown in FIG. 2 , the terminal device provided in this embodiment of the present invention may include: a memory 100, a processor 200, a display 300, and the like. Among them, the memory 100 stores a set of program codes, which are used to realize the detection and recording of the working state data of the battery pack to be tested and the single cells contained therein, as well as the differential voltage of the single cells, the maximum absolute differential voltage, the average absolute Operations such as calculation of battery parameters such as differential values. The processor 200 is used to read the program code in the memory 100, and then execute the method defined by the program code. For example, the processor 200 can read the program codes stored in the memory 100 to perform operations such as battery fault detection.

The processor 200 may include one or more processors, for example, the processor 200 may include one or more central processing units. When the processor 200 includes multiple processors, the multiple processors can be integrated on the same chip, or can be independent chips. A processor may include one or more processing cores. The following embodiments all use multi-core as an example to introduce, but the battery fault detection method provided by the embodiment of the present invention can also be applied to a single-core processor, and the details can be determined according to the actual application scenario Requirements are determined, and there is no limitation here.

In addition, the memory 100 also stores other data except the program codes, which may include data generated after the processor executes the above program codes, such as working status data of the battery pack to be tested and the single cells contained therein. The storage 100 generally includes internal memory and external storage. Memory can be random access memory (RAM), read-only memory (ROM), and high-speed cache (CACHE). External storage can be hard disk, CD, USB disk, floppy disk or tape drive, etc. Program code is usually stored in external memory, and the processor loads the program code from external memory into memory before performing processing.

Referring to FIG. 3 , it is a schematic flowchart of a battery fault detection method provided by an embodiment of the present invention. The battery fault detection method described in the embodiment of the present invention includes the detection of battery cell voltage inconsistent faults, the battery pack voltage measurement fault detection, the battery pack short circuit fault detection, and the battery pack contact resistance fault detection and so on.

The method that the embodiment of the present invention provides comprises steps:

S1. It is determined that the fault of inconsistent cell voltage occurs in the battery pack under test.

In some feasible implementation manners, firstly, it can be determined according to the difference of the cell voltages of the individual cells in the battery group to be tested whether there is an inconsistent voltage failure of the single cells in the battery group to be tested. In a specific implementation, the cell voltage of each cell in the battery pack to be tested at each of the preset N sampling moments can be obtained first, and then the differential voltage of each cell at each sampling moment can be determined. Further, it can be determined according to the difference voltages of the individual cells that the battery pack under test has a cell voltage inconsistency fault. In the specific implementation, refer to FIG. 4 , which is another schematic flow chart of the battery fault detection method provided by the embodiment of the present invention. The identification method for the fault of inconsistent cell voltage of the battery pack under test may include steps S11-S14:

S11. Calculate the average value U _m of the cell voltage of each cell at the sampling time k.

Assuming that the battery pack has a total of n single cells, the sampling time k is any one of the preset N sampling times, that is, the calculation of the average voltage at any sampling time can be implemented in the following manner. In the specific implementation, the sampling time described in the embodiment of the present invention can be each data collection time point when the BMS collects battery parameter data such as the total voltage of the battery pack according to the set sampling interval, and the above-mentioned N sampling time points can be the time points of the battery pack collected by the BMS. N continuous acquisition time points of battery parameter data such as total voltage. The voltage of each single cell in the battery pack to be tested can be collected by the BMS system without adding additional sensors, and the amount of data to be stored and the amount of data calculation are small, which reduces the difficulty of battery fault detection. The cell voltages of the above individual cells can also be detected by other voltage detectors, which is not limited here.

The terminal device can first obtain the cell voltage of each cell at the sampling time k from the data recorded by the BMS, and then calculate the average voltage U _m (k):

Wherein, U _i (k) represents the voltage of the i-th cell collected at the k-th time, that is, the cell voltage of the i-th cell at sampling time k. U _m (k) represents the average voltage collected at the kth time, that is, the average value of the cell voltages of each cell in the battery pack to be tested at the sampling time k.

S12. Calculate the differential voltage U _d,i (k) of each single battery:

U _d,i (k)=U _i (k)-U _m (k)

Among them, U _d,i (k) represents the differential voltage of the i-th single battery at the k-time sampling, that is, the differential voltage of the i-th single battery at the sampling time k.

S13. Record the differential voltage U _dmax,i with the largest absolute value of the differential voltage at the same sampling moment.

Assuming that the absolute value |U _d,i (k)| of the difference voltage of the i-th cell in the battery pack to be tested is greater than the absolute value of the difference voltage of any other cell in the k battery pack at the sampling moment, then it can be Record U _d,i (k) as U _dmax,i . Wherein, U _dmax recorded above is hereinafter referred to as the maximum absolute difference voltage.

In some feasible implementation manners, the terminal device may record U _dmax,i at each sampling moment in the N sampling moments according to the implementation manner of the above steps S11-S13, so as to obtain N U _dmax,i . Wherein, the aforementioned N may be 2x+1, and x may be a natural number such as 10. Wherein, the value of x can be determined according to the choice of the missed detection rate or false detection rate of the fault detection of the battery pack to be tested. Wherein, a larger value of x can increase the misjudgment rate, and a smaller value of x can increase the misjudgment rate. The embodiment of the present invention will use 10 as an example for illustration. In a specific implementation, each time the terminal device records the collected data, the recorded data may be updated once, that is, only the latest 2x+1 collected data is recorded.

S14. According to the differential voltages of the individual cells, it is determined that a cell voltage inconsistency fault occurs in the battery pack to be tested.

In some feasible implementation manners, after the terminal device has recorded the maximum absolute difference voltage at each sampling moment, it can identify whether the cell voltage inconsistency fault occurs in the battery pack under test according to the data recorded at each sampling moment. When the U _{dmax of the same single battery (assumed to be a single battery i) consecutive N' sampling moments, i} is greater than the preset difference voltage threshold, it can be determined that the first U _{dmax greater than the preset difference voltage threshold,} At the sampling time m when _i occurs, the cell voltage of the cell i appears to be inconsistent, that is, the battery pack under test has a fault of cell voltage inconsistency. For example, when the unit battery i is greater than the preset differential voltage threshold for three consecutive U _dmax,i , it can be considered that the battery unit i has a voltage inconsistency fault when the first U _dmax,i occurs. Wherein, the above-mentioned preset difference voltage threshold may be an average value of the first x U _dmax which is more than a times. Wherein, the above-mentioned a can be determined according to the choice of the missed detection rate or false detection rate of the fault detection of the battery pack to be tested, for example, 5 and so on. Specifically, the value of a may be determined according to an actual application scenario, and the embodiment of the present invention will use 5 as an example for description.

In a specific implementation, if the terminal device determines that the battery pack under test has a voltage inconsistency fault, step S2 may be executed. That is to further determine the fault source of the inconsistent voltage of the cells in the battery pack, for example, a voltage measurement fault, a short circuit fault, or a contact resistance fault. If it is not recognized that the voltages of the cells are inconsistent, step S11 may be continued, that is, the state of the cell voltages of the cells of the battery pack may be continuously monitored.

5a and 5b below are a schematic diagram of a battery cell voltage inconsistency fault provided by an embodiment of the present invention.

Figure 5a and Figure 5b show that the cell voltage is collected once every 1s, that is, the sampling time interval of the cell voltage is 1s, for example, the collection cycle of BMS to collect battery data is 1s. Figure 5a shows a battery pack consisting of 12 single cells (assumed to be a battery pack A), and one single cell in the battery pack A has a voltage inconsistency. From Figure 5a, it can be found that at 3600s, the single battery represented by the dotted line voltage curve in the A battery pack began to have a failure problem that was inconsistent with the single battery voltage of most other single batteries. Figure 5b shows another battery pack (set B battery pack) consisting of 12 battery cells. In the B battery pack, there is a phenomenon that the voltage of a single cell is inconsistent. It can be seen from the figure that at 3600s, the single battery represented by the dotted line voltage curve in the B battery pack began to have a failure problem that was inconsistent with the voltage of most other single batteries.

Figures 6a and 6b are another schematic diagram of the battery cell voltage inconsistency fault provided by the embodiment of the present invention.

Figures 6a and 6b are the change curves of the voltage difference between the individual cells in the two battery packs (including A battery pack and B battery pack) from 3500s to 3800s. It can be found that after 3600s, there is a voltage in both A battery pack and B battery pack. The single battery has obvious abnormal battery difference voltage. Record the maximum difference voltage absolute value U _dmax,i at the same sampling moment. The number of records is 2x+1, and x is set to 10 in the embodiment of the present invention, and each record is updated once, that is, only the latest 21 times of data are recorded. When three consecutive U _dmax,i are greater than 5 times the average value of the first 10 recorded values (that is, the absolute value of the maximum difference voltage U _dmax,i ), it is considered that the single battery appears when the first U _dmax,i A voltage inconsistency fault occurs. It is also identified that the single battery represented by the dotted line in FIG. 6a and the single battery represented by the dotted line in FIG. 6b both had a voltage inconsistency fault within 3600s.

S2. Determine the first difference between the total voltage of the battery pack under test and the sum of the cell voltages of the individual cells contained in the battery pack under test when the cell voltage inconsistency fault occurs in the battery pack under test.

S3. Determine a second difference between the total voltage of the battery pack under test and the sum of cell voltages of the individual cells before the cell voltage inconsistency fault occurs in the battery pack under test.

In some feasible implementation manners, after the terminal device determines that the cell voltage inconsistency fault occurs in the battery pack to be tested, it may first determine whether the source of the cell voltage inconsistency fault is a voltage measurement fault. In a specific implementation, the terminal can determine whether the magnitude of the voltage change is within a preset change range according to the voltage change state before and after the cell voltage inconsistency fault of the battery pack occurs, so as to determine whether it is a voltage measurement fault. Specifically, the terminal device may determine the sampling time m at which the battery pack under test has a cell voltage inconsistency fault according to the implementation described in steps S11-S14 above. The terminal device can obtain the total voltage U _total1 of the battery under test at the sampling time m from the data recorded by the BMS. For example, the battery terminal voltage shown in Figure 1, etc. The terminal device can also obtain the cell voltage of each cell in the battery pack to be tested at the sampling time m from the data recorded by the BMS, and then can calculate the sum U ₁ of the cell voltages of the cells. Further, the difference between U _total1 and U ₁ can be calculated, and the absolute value of the difference can be determined as the first difference, which can be set as |dU _total | _p to determine the fault source of the battery pack. As shown in the following expression:

Wherein, U _total is the total voltage of the battery pack to be tested, and the total voltage can be collected by the BMS or measured in real time by other voltage measuring equipment, which is not limited here. U _i is the cell voltage of cell i, which can be measured by BMS or other voltage measuring equipment in real time.

In some feasible implementations, the terminal device can also calculate the difference between the total voltage of the battery pack under test and the sum of the cell voltages of each single cell before the cell voltage inconsistency fault occurs in the battery pack under test according to the above expression |dU _total | _a . In a specific implementation, the terminal device may acquire the total voltage U _total2 of the battery pack to be tested at the sampling time m1 before the sampling time m. Wherein, the above-mentioned sampling time m1 may be a sampling time before the sampling time m, and the position of the sampling time m1 may also be determined according to actual application scenario requirements. That is, the collection time interval between the sampling time m1 and the sampling time m may be one sampling period of the BMS, or may be multiple sampling intervals of the BMS, which is not limited here. The embodiment of the present invention will be described by taking one sampling period as an example, for example, 1s.

The terminal device can also obtain the cell voltage of each cell included in the battery pack to be tested at the sampling time m1 from the data recorded by the BMS, and calculate the sum U ₂ of the cell voltage of each cell. Further, the above-mentioned difference between U _total2 and U ₂ can be calculated, and the absolute value of the difference can be determined as the second difference, which is set as |dU _total | _a , which is used to determine the fault source of the battery pack.

S4, judging that the difference between the first difference and the second difference is greater than a preset voltage threshold, if yes, then determining that a voltage measurement fault occurs in the battery pack to be tested, otherwise, go to step S5.

In some feasible implementation manners, if the above-mentioned difference between |dU _total | _p and |dU _total | _a is greater than a preset voltage threshold, it can be determined that a voltage measurement fault occurs in the battery pack under test. Wherein, the above-mentioned preset voltage threshold can be determined by the voltage mutation value of the single battery that has a voltage sudden change when the battery pack under test has a voltage inconsistent fault. For example, the above-mentioned preset voltage threshold may be 30% of the voltage mutation value of the single battery in which a voltage mutation occurs. Wherein, the above-mentioned sudden change in voltage refers to the cell voltage difference between the cell voltages before and after the fault of the cell with the cell voltage inconsistency. For example, the sudden change in voltage value described after the embodiment of the present invention is the absolute difference in voltage between 3599s and 3600s of the voltage inconsistent monomer. If the above-mentioned difference between |dU _total | _p and |dU _total | _a exceeds 30% of the voltage mutation value of the single battery, it can be determined that the voltage inconsistent fault of the battery pack under test is caused by a voltage measurement fault. Wherein, the above 30% of the voltage mutation value is only an example of the embodiment of the present invention, and the preset voltage threshold can be determined according to the requirements of the actual application scenario, and is not limited here.

In specific implementation, if the source of the voltage inconsistency fault of the battery pack under test is not a voltage measurement fault, it can be further determined whether the fault source is a short circuit fault or a contact resistance fault.

S5. Determine that a short-circuit fault or a contact resistance fault occurs in the battery pack under test according to the differential voltages of the individual cells.

In some feasible implementation manners, after the terminal device determines that a voltage inconsistency fault occurs in the battery pack under test and is not caused by a voltage measurement fault, it needs to determine whether it is a contact voltage fault or a short circuit fault. In the specific implementation, the terminal equipment can separately calculate the average absolute differential value of the maximum absolute difference voltage U _dmax,i before and after the fault, and judge whether it is a contact resistance fault or a short-circuit fault according to the ratio of the average absolute differential value before and after the fault, so as to quickly realize Diagnosis of voltage inconsistency fault sources in electric vehicles. In a specific implementation, the terminal device can determine the sampling time m when the voltage inconsistency of the cells of the battery pack under test occurs, and calculate the first average absolute differential value U _MAD1 of the maximum absolute difference voltage at x1 sampling times before the sampling time m. Further, the terminal device may also calculate the second average absolute differential value U _MAD2 of the maximum absolute differential voltage at x2 sampling instants after the sampling instant m, where x2=x1=x, and x may be 10. If the above-mentioned U _MAD2 is greater than or equal to the preset multiple threshold of the above-mentioned U _MAD2 (set to 1 times), it is determined that the battery pack under test has a contact resistance fault, otherwise it is determined that the battery pack under test has a short-circuit fault.

Steps S51-S52 as shown in Figure 4:

S51. Calculate the average absolute difference U _{MAD, p} and U _{MAD, a} of the x recorded values before and after the voltage inconsistent fault occurs.

Calculate the average absolute difference value of the x recorded values before and after the voltage inconsistency fault of the battery pack under test respectively, so as to obtain the average absolute difference U _{MAD, p} after the voltage inconsistency fault occurs and the average absolute difference before the voltage inconsistency fault occurs Value U _{MAD, a} . For example, the average absolute difference value is calculated for the recorded values at 10 sampling moments (such as 3590-3599s and 3601-3610s) before and after the failure of the cell voltage inconsistency.

The calculation expression of the mean absolute difference value U _MAD is:

Among them, U _dmax,i(t) is the maximum absolute difference voltage at sampling time t, and U _MAD represents the average absolute difference value, referred to as MAD value.

S52. When U _{MAD, p} > l · U _{MAD, a} , it indicates that the dynamics become stronger after the voltage inconsistent fault, and then it can be determined as a contact resistance fault, otherwise it is a short circuit fault. Among them, the above l is determined by the actual project, and generally can be taken as 5, which is not limited here.

Referring to FIG. 7 , it is a schematic diagram of the average absolute difference U _MAD of the battery pack provided by the embodiment of the present invention. Figure 7 shows the MAD values of the two battery packs in the experiment before and after the fault of inconsistent cell voltage. Wherein, the No. A2 single battery represents the No. 2 single battery in the A battery pack, that is, the single battery represented by the dotted line in FIG. 5a and FIG. 6a. Unit B3 represents the No. 3 unit battery of the B battery pack, that is, the unit battery represented by the dotted line in Fig. 5b and Fig. 6b above. Among them, the MAD value of the maximum absolute difference voltage of the A battery pack calculated after the voltage inconsistency fault of the A2 single battery is more than 5 times the MAD value calculated before the fault, and the gap is large, indicating that the voltage after the voltage inconsistency fault occurs The voltage dynamics become stronger, and it can be determined that the fault source of the A2 single battery is the contact resistance fault. The MAD value difference before and after the voltage inconsistency fault of the B3 single battery is small, and then it can be determined that the fault source of the B3 single battery is a short-circuit fault.

According to the method provided by the embodiment of the present invention, the diagnosis of the source of the voltage inconsistency in the electric vehicle can be quickly realized in the existing products, and it can also give prompts of three kinds of fault sources when the voltage inconsistency occurs during the driving of the electric vehicle, and Users are advised to take corresponding measures to ensure the safety of electric vehicles. In the implementation mode provided by the embodiment of the present invention, the amount of pre-embedded data is small, the implantation is simple, the requirement for hardware resources is low, and the applicability is high.

The embodiment of the present invention can determine whether the cause of the failure of the battery pack under test is Faulty voltage measurement. If the failure of the battery pack to be tested is not caused by a voltage measurement fault, it can also be determined whether the fault source of the battery pack to be tested is a short-circuit fault or a contact resistance fault according to the differential voltage of each single battery. The application can realize the prior diagnosis of the fault source of the battery pack to be tested, and can improve the detection accuracy of the fault source of the battery. Further, the present application can record a plurality of maximum absolute difference voltages before and after the failure after determining that the voltage of the single cells of the battery group is inconsistent, and then determine the average of the maximum absolute difference voltages before and after the failure of the battery group Absolute difference value. This application can determine whether the battery pack fault is a short-circuit fault or a contact resistance fault by comparing the average absolute difference value before and after the battery pack fault, so as to quickly realize the diagnosis of the source of the battery pack monomer voltage inconsistency fault and improve the applicability of battery fault detection , thereby improving the safety of the battery.

Referring to FIG. 8 , it is a schematic structural diagram of a battery fault detection device provided by an embodiment of the present invention. The detection device that the embodiment of the present invention provides comprises:

A determining module 81, configured to determine the first value of the sum of the total voltage of the battery pack under test and the sum of the cell voltages of the individual cells contained in the battery pack under test when a cell voltage inconsistency fault occurs in the battery pack under test. a difference.

The determining module 81 is also used to determine the second value of the total voltage of the battery pack under test and the sum of the cell voltages of the individual cells before the cell voltage inconsistency fault occurs in the battery pack under test. difference.

The failure analysis module 82 is configured to determine that a voltage measurement failure occurs in the battery pack under test when the determination module 81 determines that the difference between the first difference and the second difference is greater than a preset voltage threshold.

The fault analysis module 82 is further configured to, when the determination module 81 determines that the difference between the first difference and the second difference is less than or equal to the preset voltage threshold, according to the The differential voltage of the battery is used to determine that a short-circuit fault or a contact resistance fault occurs in the battery pack to be tested;

Wherein, the differential voltage of any single cell is the difference between the cell voltage of any single cell and the average value of the cell voltages of each of the single cells.

In some feasible implementation manners, the device also includes:

The obtaining module 83 is used to obtain the cell voltage of each single cell in the battery pack under test at each sampling time among the preset N sampling time points.

The determination module 81 is further configured to determine the differential voltage of each single cell at each sampling time according to the cell voltage acquired by the acquisition module 83, and determine the voltage to be tested according to the differential voltage of each single cell. The battery pack has a single voltage inconsistency fault;

Wherein, the N is an integer greater than zero.

In some feasible implementation manners, the device further includes a calculation module 84;

The obtaining module 83 is also used to obtain the cell voltage of each cell in the battery pack under test at any sampling time k.

The calculation module 84 is configured to calculate the average value U _m of the cell voltages of the individual cells at the sampling time k obtained by the acquisition module 83 .

The determining module 81 is configured to determine the voltage of each single battery at the sampling time k acquired by the acquiring module 83 and the difference between the U _m calculated by the calculating module. The difference voltage of each single battery, and the difference voltage of the single battery i with the largest absolute value of the difference voltage is determined as the maximum absolute difference voltage U _dmax,i at the sampling time k.

The determination module 81 is also used to determine the first U dmax greater than the preset difference voltage threshold when the U _{dmax recorded at consecutive N' sampling moments, when i} is greater than the preset difference voltage threshold, the sampling moment at _{which i} occurs m The battery pack under test has a single voltage inconsistent fault;

Wherein, N' is an integer less than or equal to N.

In some feasible implementation manners, the determination module 81 is configured to determine the sampling time m when the fault of inconsistent cell voltage occurs in the battery pack under test.

The acquiring module 83 is further configured to acquire the total voltage U _total1 of the battery pack under test at the sampling moment m determined by the determining module 81 .

The obtaining module 83 is also used to obtain the cell voltage of each cell included in the battery pack under test at the sampling time m.

The calculation module 84 is configured to calculate the sum U ₁ of the cell voltages of the individual cells, and calculate the difference between the U _total1 and the U ₁ .

The determination module 81 is configured to determine the absolute value of the difference calculated by the calculation module as the first difference.

In some feasible implementation manners, the determination module 81 is configured to determine the sampling time m when the fault of inconsistent cell voltage occurs in the battery pack under test.

The acquisition module 83 is further configured to acquire the total voltage U _total2 of the battery pack under test at the sampling time m1 before the sampling time m determined by the determination module 81 .

The obtaining module 83 is further configured to obtain the cell voltage of each cell included in the battery pack under test at the sampling time m1.

The calculation module 84 is configured to calculate the sum U ₂ of the cell voltages of the individual cells acquired by the acquisition module, and calculate the difference between the U _total2 and the U ₂ .

The determining module 81 is configured to determine the absolute value of the difference calculated by the calculating module 84 as the second difference.

In some feasible implementation manners, the determination module 81 is also used for:

Determining the voltage mutation value of the single battery with inconsistent voltage in the battery pack to be tested, and determining the preset voltage threshold according to the voltage mutation value;

Wherein, the voltage mutation value is the difference in cell voltage between the sampling time before the fault occurs and the sampling time after the fault occurs for the single battery whose voltage is inconsistent.

In some feasible implementation manners, the determination module 81 is configured to determine the sampling time m when the fault of inconsistent cell voltage occurs in the battery pack under test.

The calculating module 84 is configured to calculate the first average absolute difference value U _MAD1 of the maximum absolute difference voltage at x1 sampling times before the sampling time m determined by the determining module.

The calculation module 84 is further configured to calculate the second average absolute difference value U _MAD2 of the maximum absolute difference voltage at x2 sampling moments after the sampling moment m, wherein, the x2=x1=x, and the x is greater than Or equal to (N-1)/2.

The failure analysis module 82 is configured to determine that the battery pack under test has a contact resistance failure when the U _MAD2 calculated by the calculation module is greater than or equal to the preset multiple threshold of the U _MAD2 , otherwise determine that the The battery pack under test has a short-circuit fault;

Among them, the calculation expression of the mean absolute difference value U _MAD is:

Among them, U _dmax,i(t) is the maximum absolute difference voltage at the sampling time t.

In a specific implementation, the above-mentioned device for detecting a battery failure may specifically be a terminal device provided in an embodiment of the present invention, and each built-in module may perform the implementation described in each step of the above-mentioned method for detecting a battery failure. For a specific implementation process, reference may be made to the implementation manners described in the above steps, which will not be repeated here. The fault analysis module described in the embodiment of the present invention can specifically be the fault analysis unit in Figure 1, and the determination module, acquisition module and calculation module can be the functional modules included in the monitoring and management unit in Figure 1, and can also be the fault analysis unit The included functional modules may be specifically determined according to the operation mode performed by each module, which is not limited here.

The embodiment of the present invention can determine whether the cause of the failure of the battery pack under test is Faulty voltage measurement. If the failure of the battery pack to be tested is not caused by a voltage measurement fault, it can also be determined whether the fault source of the battery pack to be tested is a short-circuit fault or a contact resistance fault according to the differential voltage of each single battery. The application can realize the prior diagnosis of the fault source of the battery pack to be tested, and can improve the detection accuracy of the fault source of the battery. Further, the present application can record a plurality of maximum absolute difference voltages before and after the failure after determining that the voltage of the single cells of the battery group is inconsistent, and then determine the average of the maximum absolute difference voltages before and after the failure of the battery group Absolute difference value. This application can determine whether the battery pack fault is a short-circuit fault or a contact resistance fault by comparing the average absolute difference value before and after the battery pack fault, so as to quickly realize the diagnosis of the source of the battery pack monomer voltage inconsistency fault and improve the applicability of battery fault detection , thereby improving the safety of the battery.

The terms "first", "second", "third" and "fourth" in the specification, claims and drawings of the present invention are used to distinguish different objects, rather than to describe a specific order. Furthermore, the terms "include" and "have", as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes unlisted steps or units, or optionally further includes For other steps or units inherent in these processes, methods, systems, products or devices.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be implemented through computer programs to instruct related hardware, and the programs can be stored in a computer-readable storage medium. During execution, it may include the processes of the embodiments of the above-mentioned methods. Wherein, the storage medium may be a magnetic disk, an optical disk, a read-only memory (Read-Only Memory, ROM) or a random access memory (Random Access Memory, RAM) and the like.

Claims (14)

1. A method for battery fault detection, comprising: When a cell voltage inconsistency fault occurs in the battery pack to be tested, determine the first difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells contained in the battery pack to be tested; Before the cell voltage inconsistency fault occurs in the battery pack to be tested, determine the second difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells; If the difference between the first difference and the second difference is greater than a preset voltage threshold, it is determined that a voltage measurement failure occurs in the battery pack to be tested; If the difference between the first difference and the second difference is less than or equal to the preset voltage threshold, then according to the difference voltages of the individual cells, it is determined that the battery pack under test has a short-circuit fault or Contact resistance failure; Wherein, the differential voltage of any single cell is the difference between the cell voltage of any single cell and the average value of the cell voltages of each of the single cells. 2. The method of claim 1, further comprising: Acquiring the cell voltage of each single cell in the battery pack to be tested at each of the preset N sampling moments; Determining the differential voltages of the individual cells at each sampling moment, and determining that a cell voltage inconsistency fault occurs in the battery pack under test according to the differential voltages of the individual cells; Wherein, the N is an integer greater than zero. 3. The method according to claim 2, characterized in that, determining the differential voltage of each single battery at each sampling time, and determining the occurrence of the battery pack under test according to the differential voltage of each single battery Inconsistent faults of monomer voltage include: Obtain the cell voltage of each cell in the battery pack to be tested at any sampling time k, and calculate the average value U _m of the cell voltage of each cell at the sampling time k; Determine the difference voltage of each unit cell according to the cell voltage of each unit cell at the sampling time k and the difference value of U _m , and calculate the difference of the unit cell i with the largest absolute value of the difference voltage The voltage is determined as the maximum absolute difference voltage U _dmax,i at the sampling moment k; If the _{Udmax recorded at consecutive N' sampling moments, i} is greater than the preset difference voltage threshold, then it is determined that the first _{Udmax greater than the preset difference voltage threshold occurs, and the battery pack under test occurs at the sampling moment m at which i} occurs Single voltage inconsistent fault; Wherein, N' is an integer less than or equal to N. 4. The method according to claim 3, characterized in that, when the battery pack under test has a voltage inconsistency fault, determine the total voltage of the battery pack under test and the voltage of each cell included in the battery pack under test. The first difference of the sum of cell voltages of the bulk battery includes: Determining the sampling time m at which the voltage inconsistency of the battery pack under test occurs, and obtaining the total voltage U _total1 of the battery pack under test at the sampling time m; Acquiring the cell voltages of the individual cells included in the battery pack to be tested at the sampling time m, and calculating the sum U1 _of the cell voltages of the individual cells; calculating the difference between U _total1 and U1, and determining the absolute value of the difference as the _first difference. 5. The method according to claim 3, wherein the total voltage of the battery pack to be tested and the cell voltages of the individual cells are determined before the cell voltage inconsistency fault occurs in the battery pack to be tested. The second difference of the sum consists of: Determining the sampling time m at which the voltage inconsistency of the cells in the battery pack under test occurs, and obtaining the total voltage U _total2 of the battery pack under test at the sampling time m1 before the sampling time m; Acquiring the cell voltages of the individual cells included in the battery pack to be tested at the sampling time m1, and calculating the sum U2 of the cell voltages of the individual cells _; calculating the difference between U _total2 and U ₂ , and determining the absolute value of the difference as the second difference. 6. The method according to claim 4 or 5, characterized in that, after determining that the voltage inconsistency of the cells has occurred in the battery pack to be tested, the method further comprises: Determining the voltage mutation value of the single battery with inconsistent voltage in the battery pack to be tested, and determining the preset voltage threshold according to the voltage mutation value; Wherein, the voltage mutation value is the difference in cell voltage between the sampling time before the fault occurs and the sampling time after the fault occurs for the single battery whose voltage is inconsistent. 7. The method according to any one of claims 3-6, wherein, according to the differential voltages of the individual cells, determining that a short-circuit fault or a contact resistance fault occurs in the battery pack to be tested comprises: Determine the sampling time m at which the voltage inconsistency of the battery pack under test occurs, and calculate the first average absolute difference value U _MAD1 of the maximum absolute difference voltage at x1 sampling times before the sampling time m; Calculating the second average absolute difference value U _MAD2 of the maximum absolute difference voltage at x2 sampling moments after the sampling moment m, wherein, the x2=x1=x, and the x is greater than or equal to (N-1)/2 ; If the U _MAD2 is greater than or equal to the preset multiple threshold of the U _MAD2 , it is determined that the battery pack under test has a contact resistance fault, otherwise it is determined that the battery pack under test has a short circuit fault; Among them, the calculation expression of the mean absolute difference value U _MAD is: Among them, U _dmax,i(t) is the maximum absolute difference voltage at the sampling time t. 8. A device for battery fault detection, characterized in that it comprises: A determining module, configured to determine the first difference between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells contained in the battery pack to be tested when a cell voltage inconsistency fault occurs in the battery pack to be tested difference; The determination module is further configured to determine the second difference between the total voltage of the battery pack to be tested and the sum of cell voltages of the individual cells before the cell voltage inconsistency fault occurs in the battery pack to be tested value; A failure analysis module, configured to determine that a voltage measurement failure occurs in the battery pack under test when the determination module determines that the difference between the first difference and the second difference is greater than a preset voltage threshold; The failure analysis module is further configured to, when the determination module determines that the difference between the first difference and the second difference is less than or equal to the preset voltage threshold, according to the Differential voltage, to determine that the battery pack under test has a short-circuit fault or a contact resistance fault; Wherein, the differential voltage of any single cell is the difference between the cell voltage of any single cell and the average value of the cell voltages of each of the single cells. 9. The device of claim 8, further comprising: An acquisition module, configured to acquire the cell voltage of each single cell in the battery pack to be tested at each sampling time among the preset N sampling times; The determination module is further configured to determine the differential voltage of each single battery at each sampling time according to the single cell voltage acquired by the acquisition module, and determine the battery pack to be tested according to the differential voltage of each single battery Inconsistent fault of monomer voltage occurs; Wherein, the N is an integer greater than zero. 10. The device according to claim 9, further comprising a computing module; The obtaining module is also used to obtain the cell voltage of each cell in the battery pack to be tested at any sampling time k; The calculation module is used to calculate the average value U _m of the cell voltages of the individual cells at the sampling time k obtained by the acquisition module; The determination module is configured to determine the cell voltage of each cell at the sampling time k obtained by the acquisition module and the difference between the U _m calculated by the calculation module. The differential voltage of the individual batteries, and the differential voltage of the single battery i with the largest absolute value of the differential voltage is determined as the maximum absolute differential voltage U _dmax,i at the sampling time k; The determination module is also used to determine the first U dmax that is greater than the preset difference voltage threshold when the U _dmax recorded at consecutive N' sampling moments is greater than the preset difference voltage threshold. The sampling moment m _{where i} occurs The battery pack under test has a single voltage inconsistency fault; Wherein, N' is an integer less than or equal to N. 11. The apparatus of claim 10, wherein The determination module is used to determine the sampling time m when the voltage inconsistency of the cells of the battery pack under test occurs; The obtaining module is also used to obtain the total voltage U _total1 of the battery pack under test at the sampling time m determined by the determining module; The acquisition module is also used to acquire the cell voltage of each cell included in the battery pack under test at the sampling moment m; The calculation module is used to calculate the sum U ₁ of the cell voltages of the individual cells, and calculate the difference between the U _total1 and the U ₁ ; The determination module is configured to determine the absolute value of the difference calculated by the calculation module as the first difference. 12. The apparatus of claim 10, wherein The determination module is used to determine the sampling time m when the voltage inconsistency of the cells of the battery pack under test occurs; The obtaining module is also used to obtain the total voltage U _total2 of the battery pack under test at the sampling time m1 before the sampling time m determined by the determining module; The acquiring module is further configured to acquire the individual voltage of each individual battery contained in the battery pack under test at the sampling moment m1; The calculation module is configured to calculate the sum U ₂ of the cell voltages of the individual cells obtained by the acquisition module, and calculate the difference between the U _total2 and the U ₂ ; The determination module is configured to determine the absolute value of the difference calculated by the calculation module as the second difference. 13. The device according to claim 11 or 12, wherein the determining module is further configured to: Determining the voltage mutation value of the single battery with inconsistent voltage in the battery pack to be tested, and determining the preset voltage threshold according to the voltage mutation value; Wherein, the voltage mutation value is the difference in cell voltage between the sampling time before the fault occurs and the sampling time after the fault occurs for the single battery whose voltage is inconsistent. 14. The device according to any one of claims 10-13, wherein The determination module is used to determine the sampling time m when the voltage inconsistency of the cells of the battery pack under test occurs; The calculation module is used to calculate the first average absolute difference value U _MAD1 of the maximum absolute difference voltage at x1 sampling moments before the sampling moment m determined by the determination module; The calculation module is also used to calculate the second average absolute difference value U _MAD2 of the maximum absolute difference voltage at x2 sampling moments after the sampling moment m, wherein, the x2=x1=x, and the x is greater than or Equal to (N-1)/2; The fault analysis module is used to determine that the battery pack under test has a contact resistance fault when the U _MAD2 calculated by the calculation module is greater than or equal to the preset multiple threshold of the U _MAD2 , otherwise determine that the battery pack to be tested has a contact resistance fault. A short-circuit fault occurs in the battery pack; Among them, the calculation expression of the mean absolute difference value U _MAD is: Among them, U _dmax,i(t) is the maximum absolute difference voltage at the sampling time t.