Lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis

Abstract

The present invention provides a lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis, which numbers the single lithium batteries in the lithium battery pack and obtains the terminal voltage data sequence of the single lithium batteries in the lithium battery pack during the charging stage; calculates the Manhattan distance between the single lithium batteries in the lithium battery pack and constructs the Manhattan matrix of the single lithium batteries in the lithium battery pack; based on the Manhattan matrix of the single lithium batteries in the lithium battery pack, determines the normal single lithium battery set and the faulty single lithium battery set in the lithium battery pack and gives a graded warning; uses the voltage difference analysis method to determine the fault type of the faulty single lithium battery. The lithium battery pack fault diagnosis method combining the Manhattan distance and the voltage difference analysis method proposed by the present invention has the advantages of simple operation, high accuracy, low calculation cost, and strong generalization ability.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and more specifically, to a lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis. Background Art

[0002] As the energy supply of new energy vehicle technology, the efficient, long-term and stable operation of lithium battery packs is crucial to new energy vehicles. However, in recent years, with the popularization of new energy vehicles, a large number of new energy vehicle safety accidents caused by lithium battery pack failures have occurred. The failure of lithium battery packs is often the result of the accumulation of multiple failures. Therefore, the fault diagnosis and early warning of lithium battery packs are crucial.

[0003] Common lithium battery packs include capacity faults, state of charge faults, internal resistance faults, connection key faults, and external short circuit faults. Due to different driving habits, there are large differences in the discharge conditions of new energy vehicles. However, the charging conditions of new energy vehicles are often unified. Therefore, it is more practical to diagnose and warn of possible faults in lithium battery packs based on the collected data of the charging stage of lithium battery packs. Manhattan distance is a metric representation of geometric distance, indicating the sum of the absolute wheelbases of two points on the standard coordinate system. Therefore, Manhattan distance can more sensitively reflect the distance change between the voltage change data sequences of the single lithium battery in the charging stage of the lithium battery pack. The voltage difference analysis method is to more accurately judge the type of lithium battery pack fault by comparing the voltage data of the faulty single lithium battery in the lithium battery pack with the voltage data of the normal single lithium battery. Therefore, based on the voltage data of the single lithium battery in the group during the charging stage of the lithium battery pack, the Manhattan distance and voltage difference analysis method are used to diagnose and warn of lithium battery pack faults, which has the advantages of high accuracy, low computational cost, and strong generalization ability. Summary of the invention

[0004] The purpose of the present invention is to provide a more accurate lithium battery pack fault diagnosis method. Based on this, the present invention proposes a lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis, which can effectively diagnose and warn lithium battery pack faults. The method involves using the Manhattan distance method to determine whether the lithium battery pack has a fault and perform a graded warning through the voltage data sequence of the single battery in the lithium battery pack during the charging stage, and based on the voltage difference analysis method, determine the type of lithium battery pack fault.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis includes the following steps:

[0007] S1. Numbering the single lithium batteries in the lithium battery pack and obtaining the terminal voltage data sequence of the single lithium batteries in the lithium battery pack during the charging phase;

[0008] S2, calculating the Manhattan distance between two lithium-ion batteries in the lithium-ion battery group, and constructing a Manhattan matrix of the lithium-ion batteries in the lithium-ion battery group;

[0009] S3, based on the Manhattan matrix of the single lithium battery in the lithium battery group, determine the normal single lithium battery group and the faulty single lithium battery group in the lithium battery group and give a graded warning;

[0010] S4. Use the voltage difference analysis method to determine the fault type of the faulty single lithium battery.

[0011] In step S1, the terminal voltage data sequence of the single lithium battery in the lithium battery pack during the charging phase is obtained as follows: in, is the terminal voltage change data sequence of the mth lithium battery in the lithium battery pack during the charging stage, V n,m is the nth sampled voltage during the charging stage of the mth single lithium battery, n is the total number of terminal voltage samples during the charging stage of the single lithium battery, and m is the total number of single lithium batteries in the lithium battery pack.

[0012] Furthermore, the method for constructing a Manhattan matrix of single lithium batteries in a lithium battery pack in step S2 includes:

[0013] (1) Based on the obtained terminal voltage data sequence of the single lithium battery in the lithium battery pack during the charging phase, the Manhattan distance between two single lithium batteries in the lithium battery pack is calculated. The calculation method is: d i,j =|V 1,i -V 1,j |+|V 2,i -V 2,j |+L+|V n,i -V n,j |, where d i,j is the Manhattan distance between single lithium battery i and single lithium battery j in the lithium battery pack, where i = 1, 2, ..., m, j = 1, 2, ..., m;

[0014] (2) The Manhattan matrix of the single lithium battery in the lithium battery pack is constructed by the maximum and minimum value normalization method: Among them, d i ' ,j is the normalized value of the Manhattan distance between single lithium battery i and single lithium battery j in the lithium battery pack. The specific calculation method of the maximum and minimum value normalization method is: Among them, d max =max{d 1,1 ,d 1,2 ,K,di,j}, d min =min{d 1,1 ,d 1,2 ,K,d i,j}.

[0015] Furthermore, the method for determining the normal single lithium battery set and the faulty single lithium battery set in the lithium battery group and giving a graded warning in step S3 is:

[0016] Based on the Manhattan matrix of single lithium battery in lithium battery pack Identify normal single lithium battery groups and faulty single lithium battery groups in the lithium battery group and give graded warnings.

[0017] Preferably, the basis for determining whether a normal single lithium battery set and a faulty single lithium battery set in a lithium battery group are:

[0018] (1) The normalized Manhattan distance between any two lithium-ion batteries in a normal lithium-ion battery set is in the range of (0, 0.15];

[0019] (2) Except for the single lithium battery in the normal single lithium battery group, the remaining single lithium batteries in the lithium battery group are judged as faulty batteries;

[0020] Faulty single lithium battery in lithium battery pack r The graded fault warning standards are:

[0021] (a) Level 1 Warning: Existence

[0022] (b) Level 2 Warning: Existence

[0023] (c) Level 3 warning: Existence Among them, h t It is the number of normal single lithium battery in the lithium battery pack, t=1,2,L,p; k r is the number of the faulty single lithium battery in the lithium battery pack, r = 1, 2, L, q, q is the total number of faulty single lithium batteries in the lithium battery pack;

[0024] The priority of lithium battery pack fault warning is: level 3 warning > level 2 warning > level 1 warning.

[0025] In step S4, determining the fault type of the faulty single lithium battery by using the voltage difference analysis method includes:

[0026] (1) Calculate the average voltage data sequence of normal single lithium battery cells in the lithium battery pack and the voltage residual data sequence of faulty single lithium battery cells;

[0027] (2) Analyze the characteristics of the residual voltage data sequence of the faulty single-cell lithium battery, and determine the fault type of the faulty single-cell lithium battery based on the change trend of the residual voltage data of the faulty single-cell lithium battery.

[0028] Furthermore, the average terminal voltage data sequence of the normal single lithium battery in the lithium battery pack during the charging stage is: Where c = 1, 2, L, n,

[0029] The residual data sequence of the faulty single lithium battery voltage is:

[0030]

[0031] Furthermore, the fault type of the faulty single-cell lithium battery is determined based on the residual voltage data change trend of the faulty single-cell lithium battery, wherein the determination is based on the following:

[0032] 1) If the residual voltage data of the faulty single lithium battery changes within the range of [0,0.5), it is judged as an early internal resistance fault;

[0033] 2) The starting point and end point of the residual voltage data of the faulty single lithium battery are within the range of [-0.5, 0), which is judged as a low state of charge fault;

[0034] 3) The residual voltage data change trend of the faulty single lithium battery is irregular as a whole, and there is some voltage change data in the range of [0.5, 1.5], which is judged as a capacity fault;

[0035] 4) If the residual voltage data of the faulty single lithium battery increases momentarily by more than 0.5 at the initial stage, it is judged to be a connection key failure;

[0036] 5) The residual voltage data of the faulty single lithium battery is less than 0, and the change trend decreases rapidly, which is judged as an external short circuit fault.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: based on the voltage data sequence of the single lithium battery in the lithium battery pack during the charging stage, the present invention calculates the Manhattan distance between the two single lithium batteries in the lithium battery pack, and then determines whether the lithium battery pack has a fault, and formulates a graded early warning strategy. By using the voltage difference analysis method, the voltage data of the faulty single lithium battery in the lithium battery pack and the voltage data of the normal single lithium battery are compared and analyzed to determine the type of lithium battery pack fault, and the present invention has the advantages of high accuracy, low calculation cost, and strong generalization ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis of the present invention;

[0039] Figure 2It is a display diagram of the residual voltage data sequence of a faulty single lithium battery provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0042] like Figure 1 FIG. 1 is a lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis provided by an embodiment of the present invention. Figure 1 The method shown includes the following steps:

[0043] S1. Numbering the single lithium batteries in the lithium battery pack and obtaining the terminal voltage data sequence of the single lithium batteries in the lithium battery pack during the charging phase;

[0044] S2, calculating the Manhattan distance between two lithium-ion batteries in the lithium-ion battery group, and constructing a Manhattan matrix of the lithium-ion batteries in the lithium-ion battery group;

[0045] S3, based on the Manhattan matrix of the single lithium battery in the lithium battery group, determine the normal single lithium battery group and the faulty single lithium battery group in the lithium battery group and give a graded warning;

[0046] S4. Use the voltage difference analysis method to determine the fault type of the faulty single lithium battery.

[0047] In a more specific exemplary embodiment, the steps of the method of the present invention are more specifically:

[0048] S1. Number the single lithium batteries in the lithium battery pack and obtain the terminal voltage data sequence of the single lithium batteries in the lithium battery pack during the charging phase.

[0049] In the embodiment of the present invention, in step S1, the terminal voltage data sequence of the single lithium battery in the lithium battery pack during the charging phase is specifically in the form of: in, is the terminal voltage change data sequence of the mth lithium battery in the lithium battery pack during the charging stage, V n,m is the nth sampled voltage during the charging stage of the mth single lithium battery, n is the total number of terminal voltage samples during the charging stage of the single lithium battery, and m is the total number of single lithium batteries in the lithium battery pack.

[0050] S2. Calculate the Manhattan distance between two lithium-ion batteries in a lithium-ion battery pack, and construct a Manhattan matrix of lithium-ion batteries in the lithium-ion battery pack.

[0051] In the embodiment of the present invention, in step S2, the method for constructing the Manhattan matrix of the single lithium battery in the lithium battery pack is:

[0052] (1) Based on the acquired terminal voltage data sequence of the single lithium battery in the lithium battery pack during the charging phase Calculate the Manhattan distance between two lithium-ion batteries in a lithium-ion battery pack. The calculation method is: d i,j =|V 1,i -V 1,j |+|V 2,i -V 2,j |+L+|V n,i -V n,j |, where is the terminal voltage change data sequence of the mth lithium battery in the lithium battery pack during the charging stage, V n,m is the nth sampled voltage of the mth single lithium battery during the charging stage, n is the total number of terminal voltage samples of the single lithium battery during the charging stage, m is the total number of single lithium batteries in the lithium battery pack, d i,j is the Manhattan distance between single lithium battery i and single lithium battery j in the lithium battery pack, i = 1, 2, ..., m, j = 1, 2, ..., m;

[0053] (2) The Manhattan matrix of the single lithium battery in the lithium battery pack is constructed by the maximum and minimum value normalization method: Among them, d i ' ,j is the normalized value of the Manhattan distance between single lithium battery i and single lithium battery j in the lithium battery pack. The specific calculation method of the maximum and minimum value normalization method is: Among them, d max =max{d 1,1 ,d 1,2 ,K,d i,j}, d min =min{d 1,1 ,d 1,2 ,K,d i,j}.

[0054] S3. Based on the Manhattan matrix of the single lithium battery in the lithium battery group, the normal single lithium battery group and the faulty single lithium battery group in the lithium battery group are judged and graded warnings are issued.

[0055] In the embodiment of the present invention, in step S3, the method for determining the normal single lithium battery set and the faulty single lithium battery set in the lithium battery group and giving a graded warning is:

[0056] Based on the Manhattan matrix of single lithium battery in lithium battery pack The normal single lithium battery set and the faulty single lithium battery set in the lithium battery group are judged based on:

[0057] (1) The normalized Manhattan distance between any two lithium-ion batteries in a normal lithium-ion battery set is in the range of (0, 0.15];

[0058] (2)

[0059] Except for the single lithium battery in the normal single lithium battery group, the remaining single lithium batteries in the lithium battery group are judged as faulty batteries;

[0060] Faulty single lithium battery in lithium battery pack r The graded fault warning standards are:

[0061] (a) Level 1 Warning: Existence

[0062] (b) Level 2 Warning: Existence

[0063] (c) Level 3 warning: Existence

[0064] Among them, h t It is the number of normal single lithium battery in the lithium battery pack, t=1,2,L,p; k r is the number of the faulty single lithium battery in the lithium battery pack, r = 1, 2, L, q, q is the total number of faulty single lithium batteries in the lithium battery pack;

[0065] The priority of lithium battery pack fault warning is: level 3 warning > level 2 warning > level 1 warning.

[0066] S4. Use the voltage difference analysis method to determine the fault type of the faulty single lithium battery.

[0067] In the embodiment of the present invention, in step S4, the voltage difference analysis method determines the fault type of the faulty single lithium battery in the following specific steps:

[0068] (1) Calculate the average voltage data sequence of normal single lithium battery cells in the lithium battery group and the residual voltage data sequence of faulty single lithium battery cells:

[0069] The average terminal voltage data sequence of a normal single lithium battery in a lithium battery pack during the charging phase is: c=1,2,L,n, where

[0070] The residual data sequence of the faulty single lithium battery voltage is:

[0071]

[0072] (2) Analyze the characteristics of the residual voltage data sequence of the faulty single lithium battery, and judge the fault type of the faulty single lithium battery based on the change trend of the residual voltage data of the faulty single lithium battery. The judgment basis is as follows:

[0073] 1) If the residual voltage data of the faulty single lithium battery changes within the range of [0,0.5), it is judged as an early internal resistance fault;

[0074] 2) The starting point and end point of the residual voltage data of the faulty single lithium battery are within the range of [-0.5, 0), which is judged as a low state of charge fault;

[0075] 3) The residual voltage data change trend of the faulty single lithium battery is irregular as a whole, and there is some voltage change data in the range of [0.5, 1.5], which is judged as a capacity fault;

[0076] 4) If the residual voltage data of the faulty single lithium battery increases momentarily by more than 0.5 at the initial stage, it is judged to be a connection key failure;

[0077] 5) The residual voltage data of the faulty single lithium battery is less than 0, and the change trend decreases rapidly, which is judged as an external short circuit fault.

[0078] In order to demonstrate the process and estimated performance of the lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis proposed by the present invention, an example is used here to illustrate.

[0079] Eight single lithium batteries of a certain brand with a rated capacity of 2.4Ah were connected in series to form a group. Internal resistance fault batteries, low state of charge fault batteries, low capacity fault batteries, connection key fault batteries, and external short circuit fault batteries were pre-implanted, and then the lithium battery pack charge and discharge experiment was carried out. Based on the voltage data of the single lithium battery in the lithium battery pack during the charging stage measured in the laboratory, the lithium battery pack was subjected to a fault diagnosis and early warning experiment. The specific operation steps are as follows:

[0080] (1) The single lithium batteries in the lithium battery pack are numbered B1 to B8, and the terminal voltage data sequence of the single lithium batteries in the lithium battery pack during the charging stage is counted.

[0081] (2) Based on the terminal voltage data sequence of the single lithium battery in the lithium battery group during the charging stage, the Manhattan distance between the two single lithium batteries in the lithium battery group is calculated, and the maximum and minimum value normalization method is used to construct the Manhattan matrix of the single lithium battery in the lithium battery group:

[0082] (3) Statistical analysis of the Manhattan matrix of lithium-ion batteries in the lithium-ion battery group shows that the normal lithium-ion batteries in the lithium-ion battery group are B3, B4, and B8, and the faulty lithium-ion batteries are B1, B2, B5, B6, and B7. The fault warning is determined by using the lithium-ion battery group graded fault warning standard: B1: first-level warning; B2: first-level warning; B5: second-level warning; B6: second-level warning; B7: third-level warning.

[0083] (4) Using the voltage difference analysis method to determine the type of lithium battery pack fault: Calculate the data sequence of normal single lithium battery cells in the lithium battery pack, and further calculate the voltage residual data sequence of the faulty single lithium battery cells. Figure 2 This is a diagram showing the residual voltage data sequence of a faulty single lithium battery. Figure 2 From the residual voltage data of the faulty single lithium battery, we can judge that: B1 is a low charge state fault; B2 is an internal resistance fault; B5 is a connection key fault; B6 is an external short circuit fault; B7 is a capacity fault.

[0084] It can be seen that the lithium battery pack fault diagnosis method proposed in the present invention has the advantages of simple operation, high accuracy, low calculation cost, strong generalization ability, etc.

[0085] Compared with other inventions, the difference of the solution proposed by the present invention is:

[0086] 1. The research object of the present invention is a lithium battery pack;

[0087] 2. The present invention utilizes the voltage data of the single lithium battery in the lithium battery pack during the charging phase to perform multi-fault diagnosis and early warning of the lithium battery pack;

[0088] 3. The specific research method of the present invention is: firstly, the Manhattan distance between two single lithium batteries in the lithium battery pack is calculated to determine whether the lithium battery pack has a fault; secondly, based on the Manhattan distance between two single lithium batteries in the lithium battery pack, a hierarchical early warning strategy is formulated; finally, according to the voltage data characteristics of the faulty single lithium batteries in the lithium battery pack during the charging stage, the type of lithium battery pack fault is determined;

[0089] 4. The present invention is based on a voltage difference analysis method to analyze the residual voltage data change trend of a faulty single lithium battery and determine the fault type of the faulty single lithium battery.

[0090] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

[0091] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified and replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis, characterized in that: The method comprises the following steps: S1. Numbering the single lithium batteries in the lithium battery pack and obtaining the terminal voltage data sequence of the single lithium batteries in the lithium battery pack during the charging phase; S2, calculating the Manhattan distance between two lithium-ion batteries in the lithium-ion battery group, and constructing a Manhattan matrix of the lithium-ion batteries in the lithium-ion battery group; S3, based on the Manhattan matrix of the single lithium battery in the lithium battery group, determine the normal single lithium battery group and the faulty single lithium battery group in the lithium battery group and give a graded warning; S4. Determine the fault type of the faulty single lithium battery by using a voltage difference analysis method; The step S4 uses the voltage difference analysis method to determine the fault type of the faulty single lithium battery, including: (1) Calculate the average voltage data sequence of normal single lithium battery cells in the lithium battery pack and the voltage residual data sequence of faulty single lithium battery cells; (2) Analyze the characteristics of the residual voltage data sequence of the faulty single lithium battery, and determine the fault type of the faulty single lithium battery based on the change trend of the residual voltage data of the faulty single lithium battery; The average terminal voltage data sequence of a normal single lithium battery in a lithium battery pack during the charging phase is: Where c = 1, 2, ..., n, The residual data sequence of the faulty single lithium battery voltage is: The basis for judging whether a lithium battery pack is normal or faulty is as follows: (1) The normalized Manhattan distance between any two lithium-ion batteries in a normal lithium-ion battery set is in the range of (0, 0.15]; (2) Total number of single-cell lithium batteries in a normal single-cell lithium battery pack Wherein, m is the total number of single lithium batteries in the lithium battery pack; Except for the single lithium battery in the normal single lithium battery group, the remaining single lithium batteries in the lithium battery group are judged as faulty batteries; Faulty single lithium battery in lithium battery pack r The graded fault warning standards are: (a) Level 1 Warning: Existence (b) Level 2 Warning: Existence (c) Level 3 warning: Existence Among them, h t is the number of normal single lithium battery in the lithium battery pack, t=1,2,...,p, p is the total number of normal single lithium battery in the lithium battery pack; k r is the number of the faulty single lithium battery in the lithium battery pack, r = 1, 2, ..., q, q is the total number of faulty single lithium batteries in the lithium battery pack; The priority of lithium battery pack fault warning is: level 3 warning > level 2 warning > level 1 warning.

2. The lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis as claimed in claim 1, characterized in that: The terminal voltage data sequence of the single lithium battery in the lithium battery pack during the charging phase obtained in step S1 is: in, is the terminal voltage change data sequence of the mth lithium battery in the lithium battery pack during the charging stage, V n,m is the nth sampled voltage during the charging stage of the mth single lithium battery, n is the total number of terminal voltage samples during the charging stage of the single lithium battery, and m is the total number of single lithium batteries in the lithium battery pack.

3. The lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis as claimed in claim 2, characterized in that: The method for constructing a Manhattan matrix of single lithium batteries in a lithium battery pack in step S2 comprises: (1) Based on the obtained terminal voltage data sequence of the single lithium battery in the lithium battery pack during the charging phase, the Manhattan distance between two single lithium batteries in the lithium battery pack is calculated. The calculation method is: d i,j =|V 1,i -V 1,j |+|V 2,i -V 2,j |+...+|V n,i -V n,j |, where d i,j is the Manhattan distance between single lithium battery i and single lithium battery j in the lithium battery pack, where i = 1, 2, ..., m, j = 1, 2, ..., m; (2) The Manhattan matrix of the single lithium battery in the lithium battery pack is constructed by the maximum and minimum value normalization method: Among them, d i ' ,j is the normalized value of the Manhattan distance between single lithium battery i and single lithium battery j in the lithium battery pack. The specific calculation method of the maximum and minimum value normalization method is: Among them, d max =max{d 1,1 ,d 1,2 ,...,d i,j }, d min =min{d 1,1 ,d 1,2 ,...,d i,j }.

4. The lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis as claimed in claim 3, characterized in that: The method for determining the normal single lithium battery set and the faulty single lithium battery set in the lithium battery group and giving a graded warning in step S3 is: Based on the Manhattan matrix of single lithium battery in lithium battery pack Identify normal single lithium battery groups and faulty single lithium battery groups in the lithium battery group and give graded warnings.

5. The lithium battery pack fault diagnosis method based on Manhattan distance and voltage difference analysis as claimed in claim 1, characterized in that: The fault type of the faulty single lithium battery is determined based on the residual voltage data change trend of the faulty single lithium battery, wherein the determination is based on the following: 1) If the residual voltage data of the faulty single lithium battery changes within the range of [0,0.5), it is judged as an early internal resistance fault; 2) The starting point and end point of the residual voltage data of the faulty single lithium battery are within the range of [-0.5, 0), which is judged as a low state of charge fault; 3) The residual voltage data change trend of the faulty single lithium battery is irregular as a whole, and there is some voltage change data in the range of [0.5, 1.5], which is judged as a capacity fault; 4) If the residual voltage data of the faulty single lithium battery increases momentarily by more than 0.5 at the initial stage, it is judged to be a connection key failure; 5) The residual voltage data of the faulty single lithium battery is less than 0, and the change trend decreases rapidly, which is judged as an external short circuit fault.

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