CN108931725B

CN108931725B - Method and device for detecting battery fault

Info

Publication number: CN108931725B
Application number: CN201710384131.8A
Authority: CN
Inventors: 刘兵晓; 张光辉; 郑岳久
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2017-05-26
Filing date: 2017-05-26
Publication date: 2020-12-01
Anticipated expiration: 2037-05-26
Also published as: CN108931725A

Abstract

The embodiment of the invention discloses a method and a device for detecting battery faults, wherein the method comprises the following steps: when the battery pack to be tested has a single voltage inconsistency fault, determining a first difference value between the total voltage of the battery pack to be tested and the sum of the single voltages of all single batteries contained in the battery pack to be tested; before the battery pack to be tested has the fault of inconsistent monomer voltage, determining a second difference value of the total voltage of the battery pack to be tested and the sum of the monomer voltages of the monomer batteries; if the difference value of the first difference value and the second difference value is larger than a preset voltage threshold value, determining that a voltage measurement fault occurs in the battery pack to be measured; otherwise, determining that the battery pack to be tested has a short-circuit fault or a contact resistance fault according to the difference voltage of each single battery; the differential voltage of any single battery is the difference between the single voltage of the single battery and the average value of the single voltage of each single battery. The embodiment of the 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 detecting battery fault

Technical Field

The invention relates to the field of battery management, in particular to a method and a device for detecting battery faults.

Background

At present, along with the increasing aggravation of environmental problems such as haze weather, greenhouse effect, energy crisis and the like, the sustainable development consciousness of people is gradually improved, and sustainable energy products such as electric automobiles and the like are also increasingly popularized. An energy storage device of an electric vehicle is a battery system, and mainly comprises modules such as an integration of a battery cell or a battery module, a battery management system, a high/low voltage circuit, a cooling device and the like. In recent years, many safety accidents such as spontaneous combustion of electric vehicles occur at home and abroad, and many safety accidents such as spontaneous combustion of electric vehicles are caused by faults of battery systems. The battery system of the electric vehicle may have faults such as sudden voltage inconsistency of the battery cells in the operation process, that is, the voltage of a certain battery cell is obviously inconsistent with the voltages of other battery cells. The battery system has the advantages that a plurality of battery faults such as sudden battery cell voltage inconsistency and the like are caused, if a user cannot determine the fault reason of the battery system, the fault cannot be solved by adopting corresponding measures, and further the safety accidents such as spontaneous combustion of the electric automobile and the like caused by the battery faults cannot be avoided.

In the prior art, battery parameters such as terminal voltage, electromotive force, output current of each battery cell or equivalent internal resistance of each battery cell in a battery system are collected or monitored, the collected or monitored battery parameters are compared with predefined standard parameters, and whether the battery system fails or not is determined through parameter comparison. For example, the prior art has collected the terminal voltage U of each single battery in the secondary battery pack_iAnd calculating the equivalent internal resistance Z of each single battery_iAnd through Z_iDifference value DeltaZ from reference resistance_iIt is determined whether the unit cell is micro-shorted. The reference resistance is the average value of the equivalent internal resistances of all the single batteries in the battery pack. If the number of the single batteries connected in series in the battery pack is large, the workload of acquiring or monitoring the battery parameters of each single battery in the prior art is large, and the realization difficulty is high. Furthermore, as the battery pack ages, the inconsistencies of the individual cells in the battery pack may increase, using Δ Z_iWhen the battery parameters such as the values and the like judge the micro short circuit of the battery, the inconsistency of the battery is easily judged as the micro short circuit, and the internal resistance change caused by the faults such as the contact resistance and the like is easily mistaken as the micro short circuit, so that the misjudgment probability is high. The prior art can not distinguish battery faults caused by different reasons, and has poor applicability.

Disclosure of Invention

The application provides a method and a device for detecting battery faults, 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.

A first aspect provides a method of battery fault detection, which may include:

when a cell voltage inconsistency fault occurs in a battery pack to be tested, determining a first difference value between the total voltage of the battery pack to be tested and the sum of the cell voltages of all the single cells contained in the battery pack to be tested;

before the battery pack to be tested has the fault of inconsistent monomer voltage, determining a second difference value of the total voltage of the battery pack to be tested and the sum of the monomer voltages of the monomer batteries;

if the difference value of the first difference value and the second difference value is larger than a preset voltage threshold value, determining that a voltage measurement fault occurs in the battery pack to be tested;

if the difference value between the first difference value and the second difference value is smaller than or equal to the preset voltage threshold value, determining that the battery pack to be tested has a short-circuit fault or a contact resistance fault according to the difference voltage of each single battery;

the differential voltage of any single battery is the difference between the single voltage of any single battery and the average value of the single voltages of all the single batteries.

It should be noted that the cell voltage inconsistency fault described in the present application refers to a fault of the battery pack caused by a voltage (i.e., a cell voltage) of one of the cells in the battery pack being obviously inconsistent with voltages of other cells.

According to the method and the device, when the single batteries in the battery pack to be tested have the inconsistent single voltage faults, whether the fault reason of the battery pack to be tested is the voltage measurement fault or not is determined according to the total voltage of the battery pack to be tested and the single voltage of each single battery. If the reason that the battery pack to be tested has the fault is not the voltage measurement fault, whether the fault source of the battery pack to be tested is the short-circuit fault or the contact resistance fault can be determined according to the difference voltage of each single battery. The method and the device can realize the prior diagnosis of the fault source of the battery pack to be detected, can improve the accuracy of the detection of the fault source of the battery, improve the applicability of the battery fault detection, and 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 monomer voltage of each monomer battery in the battery pack to be tested at each preset sampling time in N sampling times;

determining the difference voltage of each single battery at each sampling moment, and determining the single voltage inconsistency fault of the battery pack to be tested according to the difference voltage of each single battery;

wherein N is an integer greater than zero.

The single battery of group battery that this application accessible was surveyed in the monomer voltage of a plurality of sampling moments, and then can confirm each monomer battery's difference voltage at each sampling moment. The method can determine that the battery pack to be detected has the fault of inconsistent cell voltage according to the differential voltage of the cell batteries, can improve the detection accuracy of the fault of inconsistent cell voltage of the battery pack to be detected, further can improve the timeliness of battery fault detection, and improves the controllability of battery fault risk.

With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner, the determining the difference voltage of each single battery at each sampling time, and determining that a single voltage inconsistency fault occurs in the battery pack to be tested according to the difference voltage of each single battery includes:

acquiring the monomer voltage of each monomer battery at any sampling moment k in the battery pack to be tested, and calculating the average value U of the monomer voltages of the monomer batteries at the sampling moment k_m；

According to the cell voltage of each cell at the sampling time k and the U_mDetermines the difference voltage of each single battery, and determines the difference voltage of the single battery i with the maximum absolute value of the difference voltage as the maximum absolute difference voltage U of the sampling time k_dmax，i；

If U recorded at N' consecutive sampling moments_dmax，iIf the difference voltage is greater than the preset difference voltage threshold value, the first U greater than the preset difference voltage threshold value is determined_dmax，iAt the sampling moment m, the battery pack to be tested has a single voltage inconsistency fault;

wherein N' is an integer less than or equal to N.

The method and the device can preset the difference voltage threshold value for determining the inconsistent faults of the single voltages of the battery pack, and can record the maximum absolute difference voltage at each sampling moment. The sampling time at which the monomer voltages are inconsistent can be determined according to the maximum absolute difference voltage at each sampling time and the preset difference voltage threshold, so that the source of the battery pack fault can be detected in time, the timeliness of fault detection is improved, and the safety of the battery is improved.

With reference to the second possible implementation manner of the first aspect, in a third possible implementation manner, when the battery pack to be tested has a cell voltage inconsistency fault, determining a first difference between a total voltage of the battery pack to be tested and a sum of cell voltages of the individual cells included in the battery pack to be tested includes:

determining the sampling time m of the inconsistent single voltage fault of the battery pack to be tested, and acquiring the total voltage U of the battery pack to be tested at the sampling time m_total1；

Acquiring the monomer voltage of each single battery contained in the battery pack to be tested at the sampling moment m, and calculating the sum U of the monomer voltages of each single battery₁；

Calculating the U_total1And the U₁And determining an absolute value of the difference as the first difference.

The sampling moment that the inconsistent trouble of monomer voltage takes place for the group battery can be confirmed to this application, and then the total voltage of this sampling moment group battery can be confirmed to and the monomer voltage's of each battery cell of group battery sum, and then can confirm the difference between them as first difference for confirm the fault type of group battery. According to the method and the device, the battery pack fault source can be determined according to the battery parameters corresponding to the moment when the inconsistency of the single voltage of the battery pack occurs in the battery fault, the misjudgment rate of the detection fault detection can be reduced, and the applicability of the detection of the battery pack fault source is improved.

With reference to the second possible implementation manner of the first aspect, in a fourth possible implementation manner, before the battery pack to be tested has a cell voltage inconsistency fault, determining a second difference value between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells includes:

determining the sampling time m of the battery pack to be tested when the voltage of the battery pack to be tested is inconsistent, and acquiring the total voltage U of the battery pack to be tested at the sampling time m1 before the sampling time m_total2；

Acquiring the monomer voltage of each single battery contained in the battery pack to be tested at the sampling time m1, and calculating the sum U of the monomer voltages of each single battery₂；

Calculating the U_total2And the U₂And determining an absolute value of the difference as the second difference.

The sampling moment that the inconsistent trouble of monomer voltage takes place for the group battery can be confirmed to this application, and then the total voltage of a preceding sampling moment group battery of this sampling moment of determinable to and the monomer voltage's of each battery cell of group battery sum, and then can confirm the difference between them as the second difference for confirm the fault type of group battery. The battery pack fault source can be determined according to the battery parameters corresponding to the sampling time before the time when the inconsistency of the single voltage of the battery pack occurs in the battery pack, the selection flexibility of the sampling time is high, the misjudgment rate of the detection fault detection can be reduced, and the applicability of the detection of the battery pack fault source is improved.

With reference to the third possible implementation manner of the first aspect or the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner, after it is determined that a cell voltage inconsistency fault occurs in the battery pack to be tested, the method further includes:

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

the voltage sudden change value is a single voltage difference value of the single battery with inconsistent generated voltage at the sampling time before the fault occurs and the sampling time after the fault occurs.

According to the method and the device, the parameters for determining the voltage measurement fault of the battery can be determined according to the voltage sudden change value of the single battery when the battery pack has the inconsistent fault of the single battery, the accuracy of parameter selection can be improved, and the misjudgment rate of battery pack fault detection can be reduced.

With reference to 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, the determining that the battery pack to be tested has the short-circuit fault or the contact resistance fault according to the differential voltage of each single battery includes:

determining the sampling time m of the battery pack to be tested when the voltage of the battery pack to be tested is inconsistent, and calculating a first average absolute difference value U of the maximum absolute difference voltage of x1 sampling times before the sampling time m_MAD1；

Calculating a second average absolute difference value U of the maximum absolute difference voltage at x2 sampling times after the sampling time m_MAD2Wherein x2 is x1 is x, and x is greater than or equal to (N-1)/2;

if the U is_MAD2Greater than or equal to U_MAD2If the preset multiple threshold value is not reached, determining that the battery pack to be tested has a contact resistance fault, otherwise determining that the battery pack to be tested has a short-circuit fault;

wherein the absolute difference value U is averaged_MADThe calculation expression of (a) is:

wherein, U_dmax,i(t)Is the maximum absolute difference voltage at the sampling instant t.

According to the method and the device, after the condition that the battery pack has the inconsistent single voltage faults of the single batteries is determined, the multiple maximum absolute difference voltages before and after the faults can be recorded respectively, and then the average absolute difference value of the maximum absolute difference voltages before and after the faults of the battery pack can be determined. According to the method and the device, the battery pack fault is determined to be a short-circuit fault or a contact resistance fault through comparison of the average absolute difference values before and after the battery pack fault, so that diagnosis of the voltage inconsistency fault source of the battery pack monomer is rapidly achieved, and the applicability of battery pack fault detection is improved.

A second aspect provides an apparatus for battery fault detection, which may include:

the device comprises a determining module, a judging module and a judging module, wherein the determining module is used for determining a first difference value between the total voltage of a battery pack to be tested and the sum of the single voltages of all single batteries contained in the battery pack to be tested when the single voltage inconsistency fault occurs in the battery pack to be tested;

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

the fault analysis module is used for determining that the voltage measurement fault occurs in the battery pack to be tested when the determination module determines that the difference value between the first difference value and the second difference value is greater than a preset voltage threshold value;

the fault analysis module is further configured to determine that the battery pack to be tested has a short-circuit fault or a contact resistance fault according to the differential voltage of each single battery when the determination module determines that the difference value between the first difference value and the second difference value is smaller than or equal to the preset voltage threshold;

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

the acquisition module is used for acquiring the monomer voltage of each monomer battery in the battery pack to be tested at each preset sampling time in N sampling times;

the determining module is further configured to determine a difference voltage of each single battery at each sampling time according to the single voltage acquired by the acquiring module, and determine that a single voltage inconsistency fault occurs in the battery pack to be tested according to the difference voltage of each single battery;

wherein 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 apparatus further includes a calculation module;

the acquisition module is further used for acquiring the monomer voltage of each monomer battery in the battery pack to be tested at any sampling moment k;

the calculation module is used for calculating the average value U of the cell voltages of the single cells at the sampling time k acquired by the acquisition module_m；

The determining module is configured to obtain the U at the sampling time k according to the cell voltage of each cell at the sampling time k obtained by the obtaining module and the U calculated by the calculating module_mDetermines the difference voltage of each single battery, and determines the difference voltage of the single battery i with the maximum absolute value of the difference voltage as the maximum absolute difference voltage U of the sampling time k_dmax，i；

The determining module is also used for recording U at continuous N' sampling moments_dmax，iWhen the difference voltage is larger than the preset difference voltage threshold value, determining that the first U is larger than the preset difference voltage threshold value_dmax，iAt the sampling moment m, the battery pack to be tested has a single voltage inconsistency fault;

wherein N' is an integer less than or equal to N.

With reference to the second possible implementation manner of the second aspect, in a third possible implementation manner, the determining module is configured to determine a sampling time m when a cell voltage inconsistency fault occurs in the battery pack to be tested;

the obtaining module is further configured to obtain the total voltage U of the battery pack to be tested at the sampling time m determined by the determining module_total1；

The acquisition module is further configured to acquire the cell voltage of each cell included in the battery pack to be tested at the sampling time m;

the calculation module is used for calculating the sum U of the single voltages of the single batteries₁And calculating the U_total1And the U₁Difference of (2)；

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

With reference to the second possible implementation manner of the second aspect, in a fourth possible implementation manner, the determining module is configured to determine a sampling time m when a cell voltage inconsistency fault occurs in the battery pack to be tested;

the obtaining module is further configured to obtain the total voltage U of the battery pack to be tested at the sampling time m1 before the sampling time m determined by the determining module_total2；

The obtaining module is further configured to obtain the cell voltages of the individual cells included in the battery pack to be tested at the sampling time m 1;

the calculation module is used for calculating the sum U of the cell voltages of the single cells acquired by the acquisition module₂And calculating the U_total2And the U₂A difference of (d);

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

With reference to the fourth possible implementation manner of the second aspect or the fourth possible implementation manner of the second aspect, in a fifth possible implementation manner, the determining module is further configured to:

With reference to 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 determining module is configured to determine a sampling time m when a cell voltage inconsistency fault occurs in the battery pack to be tested;

the computing moduleAnd the first average absolute difference value U is used for calculating the maximum absolute difference voltage of x1 sampling moments before the sampling moment m determined by the determination module_MAD1；

The calculating module is further configured to calculate a second average absolute difference value U of the maximum absolute difference voltage at x2 sampling times after the sampling time m_MAD2Wherein x2 is x1 is x, and x is greater than or equal to (N-1)/2;

the fault analysis module is used for calculating the U calculated by the calculation module_MAD2Greater than or equal to U_MAD2When the preset multiple threshold value is reached, determining that the battery pack to be tested has a contact resistance fault, otherwise determining that the battery pack to be tested has a short-circuit fault;

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

the memory is used for storing a group of program codes;

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

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

According to the method and the device, when the single batteries in the battery pack to be tested have the inconsistent single voltage faults, whether the fault reason of the battery pack to be tested is the voltage measurement fault or not is determined according to the total voltage of the battery pack to be tested and the single voltage of each single battery. If the reason that the battery pack to be tested has the fault is not the voltage measurement fault, whether the fault source of the battery pack to be tested is the short-circuit fault or the contact resistance fault can be determined according to the difference voltage of each single battery. The method and the device can realize the prior diagnosis of the fault source of the battery pack to be detected, and can improve the accuracy of the detection of the fault source of the battery. Furthermore, according to the method and the device, after the condition that the single-cell voltage of the single cell of the battery pack is inconsistent is determined, a plurality of maximum absolute difference voltages before and after the fault can be recorded respectively, and then the average absolute difference value of the maximum absolute difference voltages before and after the fault of the battery pack can be determined. The battery pack fault is determined to be a short-circuit fault or a contact resistance fault through comparison of the average absolute difference values before and after the battery pack fault, so that diagnosis of the source of the voltage inconsistency fault of the battery pack is rapidly achieved, the applicability of battery fault detection is improved, and the safety of the battery can be improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a battery failure detection system provided in an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a terminal device according to an embodiment of the present invention;

FIG. 3 is a flow chart of a method of battery fault detection provided by an embodiment of the invention;

FIG. 4 is a schematic flow chart of a method for battery fault detection according to an embodiment of the present invention;

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

FIG. 5b is another schematic diagram of a cell voltage inconsistency fault provided by an embodiment of the present invention;

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

FIG. 6b is another schematic diagram of a cell voltage inconsistency fault provided by an embodiment of the present invention;

fig. 7 shows an average absolute difference U of the battery pack according to the embodiment of the present invention_MADA schematic diagram;

fig. 8 is a schematic structural diagram of a device for detecting battery failure according to an embodiment of the present invention.

Detailed Description

The method for detecting battery faults provided by the embodiment of the invention can be applied to terminal equipment, and the terminal equipment can be specifically built in an existing Battery Management System (BMS) or equipment comprising the existing BMS, can be specifically determined according to actual application scene requirements, and is not limited herein. The terminal device may also be referred to as a User Equipment (UE), a Mobile Station (MS), a mobile terminal (mobile terminal), and so on. The terminal equipment can also be a portable, pocket, hand-held, computer built-in or vehicle-mounted mobile device and the like. For example, the terminal device may be a mobile phone (or referred to as a "cellular" phone), or a computer of a mobile nature, or an electric car, etc. The embodiment of the present invention will be described by taking an electric vehicle as an example. It should be understood that, besides the terminal device, the method for detecting battery failure provided by the embodiment of the present invention may also be applied to other devices using a secondary battery, and is not limited herein. The battery cell (also called a single battery) in which the voltage of the cell is inconsistent described in the embodiment of the present invention may be a single battery in a series battery pack, or may be a single battery that works independently, and may be determined specifically according to an actual application scenario, which is not limited herein.

Sudden single-cell voltage inconsistency faults may occur in the operation process of the battery system of the electric automobile, namely the voltage of a certain single cell is obviously inconsistent with the voltages of other single cells. In an electric vehicle battery system, the causes of the cell voltage inconsistency fault mainly include: battery voltage measurement failures, contact resistance growth, battery short circuits, etc. When the failure sources of the battery systems of the electric automobiles are different, different treatment modes need to be adopted. For example, if a cell voltage inconsistency fault of the battery system of the electric vehicle is caused by a voltage measurement fault, the running electric vehicle may continue to normally run to a maintenance site. If the cell voltage inconsistency fault of the battery system of the electric automobile is caused by the increase of the contact resistance, the electric automobile can 'limp home' in a mode of limiting power. And if the fault of the electric automobile battery system with inconsistent cell voltage is a battery short circuit, the automobile should be abandoned. Therefore, when the battery system of the electric vehicle fails, how to identify the failure source of the battery system of the electric vehicle, such as a voltage measurement failure, a contact resistance failure or a short-circuit failure, is one of the important issues to be solved urgently to improve the safety of the electric vehicle.

Fig. 1 is a schematic structural diagram of a battery failure detection system according to an embodiment of the present invention. The battery fault detection system provided by the embodiment of the invention can be a battery fault detection system contained in the terminal equipment, can also be a battery fault detection system built in the existing BMS, can be determined according to the actual application scene, and is not limited herein. The battery fault detection system provided by the embodiment of the invention comprises a battery pack to be detected, a monitoring management unit, a fault analysis unit and the like. The monitoring management unit may be an existing BMS or a related monitoring management unit included in the BMS, and may be determined according to an actual application scenario, which is not limited herein. The monitoring management unit can be used for recording the working state data of the battery pack to be tested and the single batteries contained in the battery pack in real time in the working process of the battery pack, and comprises battery parameters such as terminal voltage of the battery pack to be tested (namely output voltage of the battery pack, also called total voltage of the battery pack) and single voltage of each single battery in the battery pack to be tested at each voltage sampling time. The fault analysis unit is used for monitoring various battery parameters detected by the management unit to determine a fault source of the battery pack to be tested, such as a voltage measurement fault, a contact resistance fault or a short-circuit fault. Further, the fault analysis unit can feed back the detected fault source of the battery pack to the monitoring management unit, and the fault source is stored, recorded and/or fed back to a user through the monitoring management unit.

The method and the apparatus for battery fault detection according to the embodiment of the present invention will be described in detail with reference to fig. 2 to 8.

Fig. 2 is a schematic structural diagram of a terminal device according to an embodiment of the present invention. As shown in fig. 2, the terminal device provided in the embodiment of the present invention may include: memory 100, processor 200, and display 300. The memory 100 stores a set of program codes for implementing operations such as detecting and recording the operating state data of the battery pack to be tested and the single batteries contained in the battery pack, and calculating battery parameters such as differential voltage, maximum absolute differential voltage, and average absolute differential value of the single batteries. 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 may read program code stored in the memory 100 to perform operations such as battery failure detection.

Processor 200 may include one or more processors, for example, processor 200 may include one or more central processors. When the processor 200 includes multiple processors, the multiple processors may be integrated on the same chip or may be separate chips. One processor may include one or more processing cores, and the following embodiments are all described by taking multiple cores as an example, but the method for detecting a battery fault provided in the embodiment of the present invention may also be applied to a single-core processor, and may be specifically determined according to requirements of an actual application scenario, which is not limited herein.

In addition, the memory 100 stores other data besides the program codes, and the other data may include data generated after the processor executes the program codes, such as operating state data of the battery pack to be tested and the battery cells included in the battery pack to be tested. Memory 100 generally includes both internal memory and external memory. The memory may be Random Access Memory (RAM), Read Only Memory (ROM), CACHE (CACHE), etc. The external memory can be a hard disk, an optical disk, a USB disk, a floppy disk or a tape drive. The program code is typically stored in an external memory from which the processor loads the program code into the internal memory before performing the processing.

Referring to fig. 3, a flow chart of the method for detecting a battery fault according to the embodiment of the present invention is shown. The method for detecting the battery faults described in the embodiment of the invention comprises the implementation modes of operations such as detecting the voltage inconsistency fault of the battery pack, detecting the voltage measurement fault of the battery pack, detecting the short-circuit fault of the battery pack, detecting the contact resistance fault of the battery pack and the like.

The method provided by the embodiment of the invention comprises the following steps:

and S1, determining that the cell voltage inconsistency fault of the battery pack to be tested occurs.

In some possible embodiments, whether the cell voltage inconsistency fault of the cell battery occurs in the battery pack to be tested may be determined according to the difference of the cell voltages of the respective cell batteries in the battery pack to be tested. In specific implementation, the cell voltage of each cell in the battery pack to be tested at each preset N sampling moments can be obtained, and then the difference voltage of each cell at each sampling moment can be determined. Furthermore, the battery pack to be tested can be determined to have the fault of inconsistent single voltage according to the difference voltage of each single battery. In specific implementation, referring to fig. 4, which is another schematic flow chart of the method for detecting battery faults provided in the embodiment of the present invention, the identification method of the inconsistent cell voltage fault of the battery pack to be tested may include steps S11-S14:

s11, calculating the average value U of the single voltage of each single battery at the sampling moment k_m。

Assuming that the battery pack has N single batteries in total, the sampling time k is any one of preset N sampling times, that is, the following implementation mode can be adopted for calculating the average voltage at any sampling time. In a specific implementation, the sampling time described in the embodiment of the present invention may be each data acquisition time point at which the BMS acquires battery parameter data such as a total voltage of the battery pack according to a set sampling interval, and the N sampling times may be consecutive N acquisition time points at which the BMS acquires battery parameter data such as a total voltage of the battery pack. The individual voltage of each individual battery in the battery pack to be detected can be acquired by the BMS system, no additional sensor is needed, the data volume and the data calculation amount which need to be stored are small, and the difficulty of battery fault detection is reduced. The cell voltage of each cell may also be detected by other voltage detectors, which is not limited herein.

The terminal equipment can firstly obtain the monomer voltage of each monomer battery at the sampling time k from the data recorded by the BMS, and can further calculate the average voltage U_m(k)：

Wherein, U_i(k) And the voltage of the ith single battery collected at the kth time is represented, namely the single voltage of the ith single battery at the sampling time k. U shape_m(k) And the average voltage collected at the kth time is represented, namely the average value of the single voltage of each single battery in the battery pack to be tested at the sampling time k.

S12, calculating the difference voltage U of each single battery_d,i(k)：

U_d,i(k)＝U_i(k)-U_m(k)

Wherein, U_d,i(k) And the differential voltage of the ith single battery at the kth acquisition time, namely the differential voltage of the ith single battery at the sampling time k is represented.

S13, recording the differential voltage U with the maximum absolute value of the differential voltage at the same sampling moment_dmax,i。

Suppose the absolute value | U of the differential voltage of the ith cell in the battery pack to be tested_d,i(k) If | is greater than the absolute value of the difference voltage of any other single battery in the k battery pack at the sampling moment, U can be converted into_d,i(k) Is recorded as U_dmax,i. Wherein the recorded U_dmaxHereinafter, the maximum absolute difference voltage is abbreviated.

In some possible embodiments, the terminal device may record U of each of the N sampling instants according to the implementation manner of the above steps S11-S13_dmax,iTo obtain N U_dmax,i. Wherein, the N can be 2x +1, wherein, x can be a natural number such as 10. Wherein, the value of x can be determined according to the battery pack to be testedAnd (4) judging the acceptance or rejection of the false judgment rate or the false judgment rate of the fault detection. In which, a larger value of x may improve the false positive rate, and a smaller value of x may improve the false negative rate, and the embodiment of the present invention will be described with reference to fig. 10 as an example. In a specific implementation, the terminal device may update the recorded data once every time it records the acquired data, that is, only records the data acquired last 2x +1 times.

S14, determining that the battery pack to be tested has the fault of inconsistent single voltage according to the difference voltage of each single battery.

In some feasible embodiments, after the terminal device records the maximum absolute difference voltage at each sampling time, it can identify whether the battery pack to be tested has a single voltage inconsistency fault according to the data recorded at each sampling time. When U of continuous N' sampling moments of the same single battery (assumed to be a single battery i) appears_dmax，iGreater than the predetermined difference voltage threshold, then U at the first greater than the predetermined difference voltage threshold may be determined_dmax，iAnd at the sampling moment m, the single battery i has the single voltage inconsistency, namely, the battery pack to be tested has the single voltage inconsistency fault. For example, when the single battery i is continuous with 3U_dmax,iIf the difference voltage is greater than the preset difference voltage threshold, the battery cell i is considered to have the first U_dmax,iA voltage inconsistency fault occurs. Wherein the preset difference voltage threshold can be the first x U s more than a times_dmaxAverage value of (a). The a may be determined according to a trade-off of a false positive rate or a false negative rate of the fault detection of the battery pack to be tested, for example, 5. Specifically, the value of a may be determined according to an actual application scenario, and the embodiment of the present invention will be described with reference to fig. 5 as an example.

In a specific implementation, if the terminal device determines that the cell voltage inconsistency fault occurs in the battery pack to be tested, step S2 may be executed. The method further determines the fault source of the battery pack with the cell voltage inconsistency fault, such as a voltage measurement fault, a short-circuit fault or a contact resistance fault. If the cell voltage is not identified to be inconsistent, step S11 may be executed to continue monitoring the cell voltage status of the battery pack.

Referring to fig. 5a and 5b, a schematic diagram of a cell voltage inconsistency fault according to an embodiment of the present invention is shown.

In fig. 5a and 5b, the cell voltage is collected once for 1s, that is, the sampling time interval of the cell voltage is 1s, and the collection period of the BMS collecting the battery data is 1s, for example. Fig. 5a shows a battery pack (assumed as a battery pack) consisting of 12 single cells, in which a phenomenon of voltage inconsistency occurs in one single cell. It can be seen from fig. 5a that at 3600s, the single cell represented by the dashed voltage curve in the a-cell group begins to experience a failure problem that is inconsistent with the cell voltages of most other single cells. Fig. 5B shows another battery pack (designated as a B battery pack) consisting of 12 battery cells. In the B battery pack, a phenomenon that the voltage of one single battery is inconsistent occurs. It can be seen from the figure that at 3600s, the single battery represented by the dashed voltage curve in the B battery pack begins to have a failure problem inconsistent with the voltages of most other single batteries.

Fig. 6a and 6b are another schematic diagrams of a cell voltage inconsistency fault provided by an embodiment of the present invention.

Fig. 6a and 6B are variation curves of the differential voltage of the single cells in two battery packs (including the battery pack a and the battery pack B) from 3500s to 3800s, and it can be found that after 3600s, a single cell in both the battery pack a and the battery pack B has a phenomenon of significant differential voltage abnormality of the single cell. For the absolute value U of the maximum difference voltage at the same sampling moment_dmax,iAnd recording is carried out. The number of records is 2x +1, and the embodiment x of the invention takes 10, and the data is updated once every record, namely only the last 21 times of data are recorded. When 3U are continuous_dmax,iGreater than 5 times the first 10 recorded values (i.e. the absolute value of the maximum difference voltage U)_dmax,i) Is considered to be the first U to appear in the cell_dmax,iA voltage inconsistency fault occurs. It is recognized that the voltage inconsistency fault occurred at 3600s in both the unit cell represented by the dotted line in fig. 6a and the unit cell represented by the dotted line in fig. 6 b.

And S2, determining a first difference value between the total voltage of the battery pack to be tested and the sum of the single voltages of the single batteries contained in the battery pack to be tested when the battery pack to be tested has the single voltage inconsistency fault.

And S3, determining a second difference value of the sum of the total voltage of the battery pack to be tested and the single voltage of each single battery before the battery pack to be tested has the single voltage inconsistency fault.

In some possible embodiments, 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 specific implementation, the terminal can determine whether the amplitude of voltage change is within a preset change range according to the voltage change states before and after the battery pack generates the voltage inconsistency fault, so as to determine whether the voltage measurement fault is generated. Specifically, the terminal device may determine the sampling time m when the cell voltage inconsistency fault occurs in the battery pack to be tested according to the implementation manners described in the above steps S11-S14. The terminal equipment can obtain the total voltage U of the battery to be tested at the sampling moment m from the data recorded by the BMS_total1. For example, the battery terminal voltage shown in fig. 1, etc. The terminal equipment can also obtain the monomer voltage of each single battery in the battery pack to be tested at the sampling moment m from the data recorded by the BMS, and further can calculate the sum U of the monomer voltages of the single batteries₁. Further, U may be calculated_total1And U₁Is determined as a first difference value, set to | dU_total|_pAnd is used for determining the fault source of the battery pack. The following expression is shown:

wherein, U_totalThe total voltage of the battery pack to be measured can be acquired by the BMS and also can be measured in real time by other voltage measuring equipment, which is not limited herein. U shape_iThe cell voltage of the cell i can be measured by the BMS or measured by other voltage measuring equipment in real time.

In some possible embodimentsThe terminal equipment can also calculate the difference | dU between the total voltage of the battery pack to be tested and the sum of the single voltages of the single batteries before the single voltage inconsistency fault of the battery pack to be tested occurs according to the expression_total|_a. In specific implementation, the terminal device may obtain the total voltage U of the battery pack to be tested at the sampling time m1 before the sampling time m_total2. The sampling time m1 may be a previous sampling time of the sampling time m, and the position of the sampling time m1 may also be determined according to the requirements of the actual application scenario. That is, the sampling time interval between the sampling time m1 and the sampling time m may be one sampling period of the BMS or may be a plurality of sampling intervals of the BMS, which is not limited herein. The embodiment of the present invention will be described by taking one sampling period as an example, for example, 1 s.

The terminal equipment can also obtain the single voltage of each single battery contained in the battery pack to be tested at the sampling time m1 from the data recorded by the BMS, and calculate the sum U of the single voltages of each single battery₂. Further, the above U can be calculated_total2And U₂And determining the absolute value of the difference as a second difference, set to | dU_total|_aAnd is used for determining the fault source of the battery pack.

And S4, judging that the difference value between the first difference value and the second difference value is larger than a preset voltage threshold value, if so, determining that the battery pack to be tested has a voltage measurement fault, otherwise, executing the step S5.

In some possible embodiments, if the above | dU_total|_pAnd | dU_total|_aIf the difference is greater than the preset voltage threshold, it can be determined that the battery pack to be measured has a voltage measurement fault. The preset voltage threshold value can be determined by the voltage mutation value of the single battery with voltage mutation when the battery pack to be tested has a single voltage inconsistency fault. For example, the preset voltage threshold may be 30% of a voltage jump value of a unit cell in which a voltage jump occurs. The voltage jump value is a cell voltage difference value between a cell with inconsistent cell voltages before and after a fault occurs. For example, the voltage-change value described later in the embodiments of the present invention is the occurrence voltageThe absolute difference of the voltages of the uniform cell at 3599s and 3600 s. If the above | dU_total|_pAnd | dU_total|_aIf the difference value exceeds 30% of the voltage mutation value of the single battery, the fact that the voltage inconsistency fault of the single battery pack to be tested is caused by the voltage measurement fault can be determined. The voltage variation value of 30% is only an example of the embodiment of the present invention, and the setting of the preset voltage threshold may be determined according to the requirements of the actual application scenario, which is not limited herein.

In specific implementation, if the source of the inconsistent cell voltage fault of the battery pack to be tested is not a voltage measurement fault, whether the fault source is a short-circuit fault or a contact resistance fault can be further determined.

And S5, determining that the battery pack to be tested has a short-circuit fault or a contact resistance fault according to the difference voltage of each single battery.

In some possible embodiments, when the terminal device determines that the voltage inconsistency fault of the battery pack to be tested occurs and the non-voltage measurement fault is caused, it needs to determine whether the battery pack is a contact voltage fault or a short-circuit fault. In specific implementation, the terminal device can respectively calculate the maximum absolute difference voltage U before and after the fault_dmax,iThe average absolute difference value of the voltage difference value is judged to be a contact resistance fault or a short-circuit fault according to the ratio of the average absolute difference value before and after the fault, so that the diagnosis of the voltage inconsistency fault source in the electric vehicle is quickly realized. In specific implementation, the terminal device can determine a sampling time m of a to-be-detected battery pack with a single voltage inconsistency fault, and calculate a first average absolute difference value U of maximum absolute difference voltages at x1 sampling times before the sampling time m_MAD1. Further, the terminal device may calculate a second average absolute difference value U of the maximum absolute difference voltage at x2 sampling times after the sampling time m_MAD2Wherein, x2 is x1 is x, and x may be 10. If the above-mentioned U is_MAD2Greater than or equal to U_MAD2If the preset multiple threshold value is set to be l times, determining that the battery pack to be tested has contact resistance faults, otherwise determining that the battery pack to be tested has short-circuit faults.

As shown in FIG. 4, steps S51-S52:

s51, calculating the average absolute difference value U of x recorded values before and after the fault of inconsistent voltage_MAD，pAnd U_MAD，a。

Respectively calculating the average absolute difference value of x recorded values before and after the voltage inconsistency fault of the battery pack to be tested, thereby obtaining the average absolute difference value U after the voltage inconsistency fault occurs_MAD，pAnd the average absolute difference value U before the voltage inconsistency fault_MAD，a. For example, the average absolute difference value is calculated for the recorded values of 10 sampling moments (such as 3590-3599 s and 3601-3610 s) before and after the single voltage inconsistency fault occurs.

Mean absolute difference value U_MADThe calculation expression is:

wherein, U_dmax,i(t)Maximum absolute difference voltage, U, at sampling time t_MADRepresenting the mean absolute difference value, abbreviated MAD value.

S52, when U_MAD，p>l·U_MAD，aWhen the voltage is inconsistent, the dynamic property becomes strong after the voltage is inconsistent, and then the contact resistance fault can be determined, otherwise, the short-circuit fault is determined. Wherein, the above l is actually determined by engineering, and may be generally 5, which is not limited herein.

Referring to fig. 7, it is an average absolute difference U of the battery pack according to the embodiment of the present invention_MADSchematic representation. The MAD values of the two battery packs before and after the cell voltage inconsistency failure of the experiment are shown in fig. 7. The a2 single battery represents the 2 single battery in the a battery pack, i.e. the single battery represented by the dotted line in fig. 5a and fig. 6 a. The B3 # cell represents the 3 # cell of the B battery pack, i.e., the cell represented by the dotted line in fig. 5B and 6B described above. Wherein, the MAD value of the maximum absolute difference voltage of the A battery pack calculated after the A2 single battery cell generates the voltage inconsistency fault is more than 5 times of the MAD value calculated before the fault, and the difference is large, which indicates that the MAD value after the voltage inconsistency fault occursThe voltage dynamics became strong, and it was determined that the failure source of the a2 # cell was a contact resistance failure. The MAD value difference between the B3 single battery before and after the voltage inconsistency fault is small, and the fault source of the B3 single battery can be determined to be a short-circuit fault.

According to the method provided by the embodiment of the invention, the diagnosis of the voltage inconsistency source fault in the electric vehicle can be quickly realized in the existing product, the prompt of three fault sources can be given when the voltage inconsistency occurs in the driving process of the electric vehicle, and the user is advised to adopt corresponding measures to ensure the driving safety of the electric vehicle. In the implementation mode provided by the embodiment of the invention, the embedded data amount is small, the implantation is simple, the requirement on hardware resources is low, and the applicability is high.

According to the embodiment of the invention, when the single battery in the battery pack to be tested has the single voltage inconsistency fault, whether the fault reason of the battery pack to be tested is the voltage measurement fault or not is determined according to the total voltage of the battery pack to be tested and the single voltage of each single battery. If the reason that the battery pack to be tested has the fault is not the voltage measurement fault, whether the fault source of the battery pack to be tested is the short-circuit fault or the contact resistance fault can be determined according to the difference voltage of each single battery. The method and the device can realize the prior diagnosis of the fault source of the battery pack to be detected, and can improve the accuracy of the detection of the fault source of the battery. Furthermore, according to the method and the device, after the condition that the single-cell voltage of the single cell of the battery pack is inconsistent is determined, a plurality of maximum absolute difference voltages before and after the fault can be recorded respectively, and then the average absolute difference value of the maximum absolute difference voltages before and after the fault of the battery pack can be determined. The battery pack fault is determined to be a short-circuit fault or a contact resistance fault through comparison of the average absolute difference values before and after the battery pack fault, so that diagnosis of the source of the voltage inconsistency fault of the battery pack is rapidly achieved, the applicability of battery fault detection is improved, and the safety of the battery can be improved.

Fig. 8 is a schematic structural diagram of a device for detecting battery failure according to an embodiment of the present invention. The detection device provided by the embodiment of the invention comprises:

the determining module 81 is configured to determine, when a cell voltage inconsistency fault occurs in the battery pack to be tested, a first difference between a total voltage of the battery pack to be tested and a sum of cell voltages of the individual cells included in the battery pack to be tested.

The determining module 81 is further configured to determine a second difference value between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells before the battery pack to be tested has a cell voltage inconsistency fault.

And the fault analysis module 82 is configured to determine that a voltage measurement fault occurs in the battery pack to be tested 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 determine that the battery pack to be tested has a short-circuit fault or a contact resistance fault according to the differential voltage of each single battery when the determination module 81 determines that the difference between the first difference and the second difference is smaller than or equal to the preset voltage threshold;

In some possible embodiments, the apparatus further comprises:

the obtaining module 83 is configured to obtain a cell voltage of each cell in the battery pack to be tested at each preset sampling time in N preset sampling times.

The determining module 81 is further configured to determine a difference voltage of each single battery at each sampling time according to the single voltage acquired by the acquiring module 83, and determine that a single voltage inconsistency fault occurs in the battery pack to be tested according to the difference voltage of each single battery;

wherein N is an integer greater than zero.

In some possible embodiments, the apparatus further comprises a calculation module 84;

the obtaining module 83 is further configured to obtain the cell voltage of each cell in the battery pack to be tested at any sampling time k.

The calculating module 84 is configured to calculate an average value U of the cell voltages of the individual cells at the sampling time k, which is obtained by the obtaining module 83_m。

The determining module 81 is configured to obtain the cell voltage of each cell at the sampling time k according to the cell voltage obtained by the obtaining module 83 at the sampling time k and the U calculated by the calculating module_mDetermines the difference voltage of each single battery, and determines the difference voltage of the single battery i with the maximum absolute value of the difference voltage as the maximum absolute difference voltage U of the sampling time k_dmax，i。

The determining module 81 is further configured to record U at N' consecutive sampling time instants_dmax，iWhen the difference voltage is larger than the preset difference voltage threshold value, determining that the first U is larger than the preset difference voltage threshold value_dmax，iAt the sampling moment m, the battery pack to be tested has a single voltage inconsistency fault;

wherein N' is an integer less than or equal to N.

In some possible embodiments, the determining module 81 is configured to determine a sampling time m when a cell voltage inconsistency fault occurs in the battery pack to be tested.

The obtaining module 83 is further configured to obtain the total voltage U of the battery pack to be tested at the sampling time m determined by the determining module 81_total1。

The obtaining module 83 is further configured to obtain the cell voltage of each cell included in the battery pack to be tested at the sampling time m.

The calculating module 84 is configured to calculate a sum U of the cell voltages of the respective cells₁And calculating the U_total1And the U₁The difference of (a).

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

The obtaining module 83 is further configured to obtain the total voltage U of the battery pack to be tested at the sampling time m1 before the sampling time m determined by the determining module 81_total2。

The obtaining module 83 is further configured to obtain the cell voltage of each cell included in the battery pack to be tested at the sampling time m 1.

The calculating module 84 is configured to calculate a sum U of the cell voltages of the cell batteries acquired by the acquiring module₂And calculating the U_total2And the U₂The difference of (a).

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 possible embodiments, the determining module 81 is further configured to:

The calculating module 84 is configured to calculate a first average absolute difference value U of the maximum absolute difference voltage at x1 sampling moments before the sampling moment m determined by the determining module_MAD1。

The calculating module 84 is further configured to calculate a second average absolute difference value U of the maximum absolute difference voltage at x2 sampling times after the sampling time m_MAD2Wherein x2 is x1 is x, and x is greater than or equal to (N-1)/2.

The fault analysis module 82 is used for calculating the U in the calculation module_MAD2Greater than or equal to U_MAD2When the preset multiple threshold value is reached, determining that the battery pack to be tested has a contact resistance fault, otherwise determining that the battery pack to be tested has a short-circuit fault;

In a specific implementation, the battery failure detection apparatus may be specifically a terminal device provided in the embodiment of the present invention, and may execute the implementation manner described in each step in the battery failure detection method through each built-in module of the terminal device. For a specific implementation process, reference may be made to the implementation manners described in the above steps, which are not described herein again. The failure analysis module described in the embodiment of the present invention may specifically be the failure analysis unit in fig. 1, and the determination module, the obtaining module, and the calculation module may be function modules included in the monitoring management unit in fig. 1, and may also be function modules included in the failure analysis unit, and may specifically be determined according to operation modes executed by each module, which is not limited herein.

The terms "first," "second," "third," and "fourth," etc. in the description, claims, and drawings of the present invention are used for distinguishing between different objects and not necessarily for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, system, article, or apparatus.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

Claims

1. A method of battery fault detection, comprising:

2. The method of claim 1, wherein the method further comprises:

wherein N is an integer greater than zero.

3. The method of claim 2, wherein the determining the difference voltage of each single battery at each sampling moment, and the determining that the battery pack to be tested has the fault of inconsistent cell voltages according to the difference voltage of each single battery comprises:

wherein N' is an integer less than or equal to N.

4. The method of claim 3, wherein determining a first difference value between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells included in the battery pack to be tested when the cell voltage inconsistency fault occurs in the battery pack to be tested comprises:

5. The method of claim 3, wherein determining a second difference value between the total voltage of the battery pack to be tested and the sum of the cell voltages of the individual cells before the cell voltage inconsistency fault occurs in the battery pack to be tested comprises:

Calculating the U_total2And the U₂Difference of (2)And determining an absolute value of the difference as the second difference.

6. The method according to claim 4 or 5, wherein after determining that the cell voltage inconsistency fault occurs in the battery pack under test, the method further comprises:

7. The method according to any one of claims 3 to 5, wherein the determining that the battery pack to be tested has the short-circuit fault or the contact resistance fault according to the difference voltage of each single battery comprises:

8. The method according to claim 6, wherein the determining that the battery pack to be tested has the short-circuit fault or the contact resistance fault according to the difference voltage of the single batteries comprises:

9. An apparatus for battery fault detection, comprising:

10. The apparatus of claim 9, wherein the apparatus further comprises:

wherein N is an integer greater than zero.

11. The apparatus of claim 10, wherein the apparatus further comprises a computing module;

The determining module is used for determining each monomer acquired by the acquiring moduleThe cell voltage of the battery at the sampling moment k and the U calculated by the calculation module_mDetermines the difference voltage of each single battery, and determines the difference voltage of the single battery i with the maximum absolute value of the difference voltage as the maximum absolute difference voltage U of the sampling time k_dmax，i；

wherein N' is an integer less than or equal to N.

12. The apparatus of claim 11,

the determining module is used for determining the sampling time m of the battery pack to be tested when the voltage of the battery pack to be tested is inconsistent;

the calculation module is used for calculating the sum U of the single voltages of the single batteries₁And calculating the U_total1And the U₁A difference of (d);

13. The apparatus of claim 11,

the obtaining module is further configured to obtain the sampling time m before the sampling time m determined by the determining moduleSample time m1 total voltage U of battery pack to be tested_total2；

14. The apparatus of claim 12 or 13, wherein the determination module is further configured to:

15. The apparatus of any one of claims 11-13,

the calculating module is configured to calculate a first average absolute difference value U of the maximum absolute difference voltage at x1 sampling moments before the sampling moment m determined by the determining module_MAD1；

the fault analysis module is used for calculating the U calculated by the calculation module_MAD2Is greater than or equal toIs equal to the U_MAD2When the preset multiple threshold value is reached, determining that the battery pack to be tested has a contact resistance fault, otherwise determining that the battery pack to be tested has a short-circuit fault;

16. The apparatus of claim 14,

17. A computer-readable storage medium, characterized in that it stores a computer program which, when executed by hardware, is capable of implementing the method of any one of claims 1 to 8.