Method and apparatus for detecting battery pack uniformity

Abstract

The application provides a battery pack connection point consistency detection method and device. The battery pack comprises a plurality of single batteries or a plurality of parallel battery modules, and the plurality of single batteries or the plurality of parallel battery modules have a connection point. The method is based on an electrochemical workstation with an auxiliary voltage division module, and comprises the following steps: on the basis that the electrochemical workstation applies an alternating current signal with different frequencies and an amplitude less than a preset value to the battery pack, simultaneously detecting the alternating current impedance spectrum of the plurality of single batteries or the plurality of parallel battery modules through the auxiliary voltage division module; and comparing the ohmic impedance and charge transfer impedance corresponding to the alternating current impedance spectrum of the plurality of single batteries or the plurality of parallel battery modules to determine the consistency of the battery pack. The application can detect and analyze the consistency of the single batteries and the electrical connection points in the battery pack, and has the characteristics of non-destructive and fast.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a method and apparatus for detecting battery pack consistency. Background Technology

[0002] Lithium-ion battery cells need to be connected in series and parallel to meet the requirements of new energy vehicles, which involves the consistency of individual cells and the reliability of series and parallel electrical connections. Lithium-ion individual cells generally need to undergo consistency sorting and grouping before being put into the battery pack production process. The sorting parameters are mainly internal resistance, capacity, and voltage. Some companies with strong manufacturing capabilities strictly control the manufacturing process, resulting in high consistency of their individual cell products, allowing them to directly enter the battery pack manufacturing process without sorting. Recent research has found that reliability issues such as poor soldering at external electrical connection points of individual cells have a far greater negative impact on the battery pack than differences in the internal resistance or capacity of the individual cells themselves. Therefore, in addition to the consistency of individual cells, the reliability of the electrical connections of the battery pack becomes particularly important. Testing methods for the reliability of individual cell electrical connections include screw torque verification, semi-destructive testing with tools, X-ray transmission imaging, and thermal imaging.

[0003] Electrochemical impedance spectroscopy (EIS) is a commonly used research method that analyzes electrode process kinetics, double layer dynamics, and diffusion by measuring the change in impedance with sinusoidal wave frequency, thereby studying the reaction mechanisms of electrode materials. Typically, when an electrochemical workstation detects the EIS of a battery, it uses channel A or channel B to detect the EIS of individual cells within the battery pack. Therefore, the measured results can only characterize the properties of that individual cell or the entire battery module, and cannot reflect the instantaneous characteristics of each individual cell within the entire battery pack, nor can they reflect the electrical connections within the battery pack. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for detecting battery pack consistency. This method and apparatus can detect and analyze the consistency of individual cells and electrical connection points in a battery pack, and is non-destructive and fast.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for detecting the consistency of a battery pack. The battery pack includes multiple individual cells or multiple parallel battery modules, and the multiple individual cells or multiple parallel battery modules have connection points. The method is based on an electrochemical workstation with an auxiliary voltage divider module. The method includes: applying AC signals with different frequencies and amplitudes less than a preset value to the battery pack by the electrochemical workstation; simultaneously detecting the AC impedance spectra of the multiple individual cells or multiple parallel battery modules through the auxiliary voltage divider module; comparing the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or multiple parallel battery modules to determine the consistency of the battery pack.

[0006] Preferably, determining the consistency of the battery pack by comparing the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules includes: determining that the battery pack is consistent normally when the ohmic impedance and charge transfer impedance among all AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules meet preset conditions. The preset conditions are that under AC signals of the same frequency, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

[0007] Preferably, determining the battery pack consistency by comparing the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules includes: determining that the battery pack consistency is abnormal when the ohmic impedance and charge transfer impedance between any AC impedance spectrum of the plurality of individual cells or the plurality of parallel battery modules and other AC impedance spectra do not meet preset conditions. The preset conditions are that under AC signals of the same frequency, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

[0008] Preferably, when the battery pack consistency is determined to be abnormal, and the battery pack is a parallel battery pack, the method further includes: determining that the individual cells corresponding to the AC impedance spectrum with a larger ohmic impedance and a difference greater than a second threshold and a difference in charge transfer impedance less than a first threshold compared with other AC impedance spectra are abnormal individual cells.

[0009] Preferably, when the battery pack consistency is determined to be abnormal, and the battery pack is a parallel battery pack, the method further includes: determining the connection point between the individual cell corresponding to the AC impedance spectrum that has a smaller ohmic impedance and a difference greater than a second threshold and a smaller charge transfer impedance and a difference greater than a first threshold and the individual cell in the positive and negative terminal directions of the battery pack as an abnormal connection point.

[0010] Preferably, when it is determined that the battery pack consistency is abnormal, and the battery pack is a series battery pack or multiple parallel battery modules connected in series, the method further includes: determining the connection point of the end other than the positive or negative terminal of the battery pack at both ends of the single cell or parallel battery module corresponding to the AC impedance spectrum that has a larger ohmic impedance than other AC impedance spectra and a difference greater than a second threshold, and a difference in charge transfer impedance less than a first threshold, as an abnormal connection point.

[0011] This invention also provides a battery pack consistency detection device, wherein the battery pack includes multiple individual cells or multiple parallel battery modules, and the multiple individual cells or multiple parallel battery modules have connection points. The device is based on an electrochemical workstation with an auxiliary voltage divider module, and includes: a detection unit, used to simultaneously detect the AC impedance spectra of the multiple individual cells or multiple parallel battery modules through the auxiliary voltage divider module, based on the application of AC signals with different frequencies and amplitudes less than a preset value to the battery pack by the electrochemical workstation; and a processing unit, used to compare the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or multiple parallel battery modules to determine the consistency of the battery pack.

[0012] Preferably, the processing unit is used to: determine that the battery pack is consistent and normal when the ohmic impedance and charge transfer impedance between all AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules meet preset conditions. The preset conditions are that under AC signals of the same frequency, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

[0013] Preferably, the processing unit is used to: determine that the battery pack consistency is abnormal when the ohmic impedance and charge transfer impedance between any AC impedance spectrum of the plurality of individual cells or the plurality of parallel battery modules and other AC impedance spectra do not meet preset conditions. The preset conditions are that under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

[0014] Preferably, when the battery pack consistency is determined to be abnormal, and the battery pack is a parallel battery pack, the processing unit is used to: determine the connection point between the individual cell corresponding to the AC impedance spectrum that has a smaller ohmic impedance and a difference greater than a second threshold and a smaller charge transfer impedance and a difference greater than a first threshold and the individual cell in the positive and negative terminal directions of the battery pack as an abnormal connection point.

[0015] Through the above technical solution, the embodiments of the present invention provide a method and apparatus for detecting battery pack consistency, which can detect and analyze the consistency of individual cells and electrical connection points in the battery pack. It has the characteristics of being non-destructive and fast, and is suitable for consistency detection of various electrical connection methods such as screw connection and laser welding.

[0016] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a flowchart of a battery pack consistency detection method provided in an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of a battery pack consisting of two individual batteries connected in parallel, according to an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the AC impedance spectrum of a battery pack composed of two individual cells connected in parallel, provided in an embodiment of the present invention, showing normal consistency.

[0021] Figure 4 This is a schematic diagram of the AC impedance spectrum of a battery pack composed of two individual cells connected in parallel, provided by another embodiment of the present invention, showing normal consistency.

[0022] Figure 5 This is a schematic diagram of the AC impedance spectrum of a 3-parallel 3-string battery pack with normal consistency according to an embodiment of the present invention;

[0023] Figure 6-8 This is a schematic diagram of the AC impedance spectrum of a battery pack with inconsistent connection point impedances, consisting of two parallel individual batteries, provided in an embodiment of the present invention.

[0024] Figure 9 This is a schematic diagram of the AC impedance spectrum of a battery pack consisting of two parallel individual cells with inconsistent internal resistances, provided in an embodiment of the present invention.

[0025] Figure 10 This is a schematic diagram of the AC impedance spectrum of a 3-parallel 3-series battery pack with inconsistent connection point impedances according to an embodiment of the present invention;

[0026] Figure 11 This is a structural block diagram of a battery pack consistency detection device provided in an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures

[0028] 1. Detection unit 2. Processing unit Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0030] In this invention, unreliable connection problems such as loose screws or weak welds during power battery connection are referred to as "cold solder joints." Cold solder joints in the battery pack are characterized by resistance values ​​higher than other normal connection points. Since the battery voltages in a parallel battery pack are the same, the current flowing through each individual cell will differ due to variations in the internal resistance of the individual cell or the resistance of the parallel connection point. The current will selectively choose the lower resistance current path, resulting in different currents flowing through each individual cell, thereby reducing the cycle life of the battery pack.

[0031] Using the technical solution of this invention, cold solder joints in parallel circuits can be detected without charging and discharging the battery pack, falling within the scope of non-destructive testing technology. Of course, the technical solution of this invention is also effective for detecting cold solder joints in series circuits. Furthermore, the individual cells used to assemble the battery pack have all undergone AC impedance spectroscopy measurements before assembly. After being sorted by parameters such as internal resistance, capacity, and voltage, the AC impedance spectroscopy curves of the individual cells entering the assembly process all overlap, indicating excellent consistency among the individual cells.

[0032] Figure 1 This is a flowchart of a battery pack consistency detection method provided in an embodiment of the present invention. Figure 1 As shown, the battery pack includes multiple individual cells or multiple parallel battery modules, and the multiple individual cells or multiple parallel battery modules have connection points. This method is based on an electrochemical workstation with an auxiliary voltage divider module, and the method includes:

[0033] Step S101: Based on the electrochemical workstation applying AC signals with different frequencies and amplitudes less than a preset value to the battery pack, the AC impedance spectrum of the multiple individual cells or the multiple parallel battery modules is simultaneously detected by the auxiliary voltage divider module.

[0034] In this embodiment of the invention, the electrochemical workstation with auxiliary voltage divider modules is preferably a SolartronEchemlab XM type electrochemical workstation, equipped with a 100V voltage module and four standard auxiliary voltage divider modules. The main channel of the electrochemical workstation with auxiliary voltage divider modules is used to apply an AC signal of different frequency and amplitude less than a preset value to the battery pack, measuring the change in the ratio of the AC signal voltage to the current (this ratio is the impedance of the battery pack) with the sinusoidal wave frequency, or the change in the phase angle of the impedance with the sinusoidal wave frequency. The auxiliary voltage divider modules are used to measure the change in the instantaneous impedance of the individual cells or multiple parallel battery modules of the battery pack with the sinusoidal wave frequency, or the change in the phase angle of the instantaneous impedance of the individual cells or multiple parallel battery modules with the sinusoidal wave frequency, after an AC signal of different frequency and amplitude less than a preset value is applied to the battery pack. This electrochemical workstation with auxiliary voltage divider modules can achieve synchronous measurement of the in-situ AC impedance spectra of the battery pack and its individual cells or multiple parallel battery modules under the same AC signal.

[0035] Step S102: Compare the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or the multiple parallel battery modules to determine the consistency of the battery pack.

[0036] In this invention, a square aluminum-cased lithium iron phosphate battery with a nominal capacity of 30Ah is selected as an example for illustration. Aluminum tabs are laser-welded onto the battery cell terminals, and then SUS304 stainless steel screws are used to connect the battery tabs to achieve series-parallel connection of the battery cells. The design of "virtual solder joints" is achieved by controlling the tightness of the connecting screws; normally, the screws are tightened with a wrench, while the design for virtual solder joints involves not tightening the connecting screws. In this embodiment, the AC impedance spectrum test conditions for a 2-parallel 60Ah battery pack are a frequency range of 2000Hz-0.01Hz and a current amplitude of 200mA; the test conditions for a 3-parallel 3-series battery pack are a frequency range of 2000Hz-0.01Hz and a current amplitude of 3000mA.

[0037] Specifically, the battery pack is considered to have normal consistency when the ohmic impedance and charge transfer impedance across all AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules meet preset conditions. The preset conditions are that, under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold, and the difference in ohmic impedance is less than a second threshold. The following is an example of a battery pack with normal consistency:

[0038] Figure 2 This is a schematic diagram of a battery pack composed of two individual battery cells connected in parallel, according to an embodiment of the present invention. Figure 2As shown, the normal resistance of the two electrical connection points between the positive and negative terminals is R1 = R2 = 0.2 mΩ. The AC impedance spectra of the battery pack and individual cells at this time are as follows: Figure 3 As shown, the AC impedance spectra of the two individual cells overlap (under AC signals of the same frequency, the difference in charge transfer impedance is less than the first threshold, and the difference in ohmic impedance is less than the second threshold; the values ​​of the first and second thresholds can be determined according to the consistency requirements of the battery pack, the same below), indicating that the connection points of the battery pack are normally consistent. Of course, if the normal resistance values ​​of both the positive and negative electrical connection points are relatively large, such as R1 = R2 = 0.7mΩ, then the AC impedance spectra of the battery pack and the individual cells are as follows... Figure 4 As shown, this also indicates that the connection points of the battery pack are relatively consistent, but the ohmic impedance of the battery pack (0.83mΩ) is significantly higher than that of a normally connected battery pack (0.66mΩ).

[0039] Figure 5 This is a schematic diagram of the AC impedance spectrum of a 3-parallel, 3-string battery pack with normal consistency, provided in an embodiment of the present invention. Figure 5 As shown, the resistance of all electrical connection points in the 3-parallel 3-series battery pack is 0.2mΩ, and the AC impedance spectra of each individual cell are quite similar after sorting. The AC impedance spectra of the three parallel battery modules also overlap in the entire battery pack, showing a high degree of consistency.

[0040] Furthermore, if the ohmic impedance and charge transfer impedance between any AC impedance spectrum of the plurality of individual cells or the plurality of parallel battery modules and other AC impedance spectra do not meet preset conditions, the battery pack consistency is determined to be abnormal. The preset conditions are that, under AC signals of the same frequency, the difference in charge transfer impedance is less than a first threshold, and the difference in ohmic impedance is less than a second threshold. The following is an example of a battery pack consistency abnormality.

[0041] Figure 6-8 This is a schematic diagram of the AC impedance spectrum of a battery pack composed of two parallel individual cells with inconsistent connection point impedances, provided in an embodiment of the present invention. For example... Figure 6-8 As shown, when the impedance of one of the positive and negative electrode connection points is higher than that of the other, the position and shape of the AC impedance spectrum curve of the parallel single cell will deviate. The AC impedance spectrum of the cell with smaller current will shift towards the direction of smaller ohmic impedance, while the charge transfer impedance will also decrease as the impedance value of one electrical connection point increases.

[0042] By adjusting the resistance R2 at the negative electrode connection point, it can be observed that as the resistance R2 increases, the current flowing through cell 2 during charging and discharging decreases. Consequently, in the comparison of the in-situ AC impedance spectra, cell 2 first shows a decrease in charge transfer impedance (e.g., when R2 = 0.5 mΩ), and then a simultaneous decrease in both charge transfer impedance and ohmic impedance (e.g., when R2 = 2 mΩ). Meanwhile, cell 1 shows a slight increase in ohmic impedance, resulting in a significant mismatch between the AC impedance spectra of the two cells. As the negative electrode connection point impedance increases from 0.2 mΩ to 2 mΩ, the ohmic impedance of the battery pack, as shown in the AC impedance spectra, also increases significantly, from 0.66 mΩ to 0.84 mΩ.

[0043] Based on this, it can be determined which specific connection point is abnormal. That is, the connection point between the individual cell and the individual cell in the positive and negative terminal directions of the battery pack corresponding to the AC impedance spectrum that has a smaller ohmic impedance and a difference greater than the second threshold and a smaller charge transfer impedance and a difference greater than the first threshold compared with other AC impedance spectra is identified as the abnormal connection point.

[0044] Figure 9 This is a schematic diagram of the AC impedance spectrum of a battery pack composed of two parallel individual cells, provided in an embodiment of the present invention, where the internal resistances of the individual cells are inconsistent. For example... Figure 9 As shown, when two individual cells with different internal resistances are connected in parallel to form a group, their positive and negative electrode electrical connection impedances are both normal connection points (0.2mΩ). At this time, the individual cells with different internal resistances exhibit different ohmic impedances in the battery pack. The individual cell with larger internal resistance exhibits a larger ohmic impedance. The difference from the trend of AC impedance spectrum changes caused by a poor solder joint at an electrical connection point is that the charge transfer impedances in the in-situ AC impedance spectra of the two individual cells with different internal resistances are still similar.

[0045] Based on this, it can be determined which specific cell is abnormal. That is, the cell corresponding to the AC impedance spectrum that is larger than other AC impedance spectra and has a difference greater than the second threshold, and has a difference in charge transfer impedance less than the first threshold, is the abnormal cell.

[0046] Figure 10 This is a schematic diagram of the AC impedance spectrum of a 3-parallel, 3-series battery pack with inconsistent connection point impedances according to an embodiment of the present invention. Figure 10As shown, if one of the two series connection points in a 3-parallel, 3-series battery pack is increased to 0.5 mΩ, the ohmic impedance of module 1 is significantly higher than that of modules 2 and 3 in the in-situ AC impedance spectrum test. In this case, the ohmic impedance and charge transfer impedance of the entire battery pack are significantly greater than those of a battery pack with normal connection points. The same principle applies to battery packs consisting of individual cells connected in series. That is, if there is inconsistency in the connection points in the series circuit, the parallel battery module or individual cell connected to the nearest positive or negative terminal of the series battery pack at the connection point with the larger resistance value will exhibit a larger ohmic impedance. Simultaneously, the ohmic impedance and charge transfer impedance of the entire series battery pack are greater than those of a normally connected battery pack.

[0047] Based on this, it can be determined which specific connection point is abnormal. That is, the connection point at the end other than the positive or negative terminal of the battery pack at both ends of the single cell or parallel battery module corresponding to the AC impedance spectrum that has a larger ohmic impedance than other AC impedance spectra and a difference greater than the second threshold, and a difference in charge transfer impedance less than the first threshold, is identified as the abnormal connection point.

[0048] Figure 11 This is a structural block diagram of a battery pack consistency detection device provided in an embodiment of the present invention. Figure 11 As shown, the battery pack includes multiple individual cells or multiple parallel battery modules, with connection points between the multiple individual cells or multiple parallel battery modules. The device is based on an electrochemical workstation with an auxiliary voltage divider module. The device includes: a detection unit 1, used to simultaneously detect the AC impedance spectra of the multiple individual cells or multiple parallel battery modules through the auxiliary voltage divider module, based on the AC signals with different frequencies and amplitudes less than a preset value applied to the battery pack by the electrochemical workstation; and a processing unit 2, used to compare the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or multiple parallel battery modules to determine the consistency of the battery pack.

[0049] Preferably, the processing unit 2 is used to: determine that the battery pack is consistent and normal when the ohmic impedance and charge transfer impedance between all AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules meet preset conditions. The preset conditions are that under AC signals of the same frequency, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

[0050] Preferably, the processing unit 2 is used to: determine that the battery pack consistency is abnormal when the ohmic impedance and charge transfer impedance between any AC impedance spectrum of the plurality of individual cells or the plurality of parallel battery modules and other AC impedance spectra do not meet preset conditions. The preset conditions are that under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

[0051] Preferably, when the battery pack consistency is determined to be abnormal, and the battery pack is a parallel battery pack, the processing unit 2 is used to: determine the connection point between the individual cell corresponding to the AC impedance spectrum that has a smaller ohmic impedance and a difference greater than a second threshold and a smaller charge transfer impedance and a difference greater than a first threshold and the individual cell in the positive and negative terminal directions of the battery pack as an abnormal connection point.

[0052] The embodiments of the battery pack consistency detection device described above are similar to the embodiments of the battery pack consistency detection method described above, and will not be repeated here.

[0053] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0054] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0055] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0056] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0057] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0058] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0059] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0060] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0061] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for detecting battery pack consistency, wherein the battery pack comprises multiple individual cells or multiple parallel battery modules, and the multiple individual cells or the multiple parallel battery modules have connection points, characterized in that, This method is based on an electrochemical workstation with an auxiliary voltage divider module, and includes: Based on the electrochemical workstation applying AC signals with different frequencies and amplitudes less than a preset value to the battery pack, the AC impedance spectrum of the multiple individual cells or the multiple parallel battery modules is simultaneously detected by the auxiliary voltage divider module. By comparing the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or the multiple parallel battery modules, the consistency of the battery pack is determined. When it is determined that the battery pack consistency is abnormal and the battery pack is a parallel battery pack, the individual cells corresponding to the AC impedance spectrum that has a larger ohmic impedance and a difference greater than the second threshold and a difference in charge transfer impedance less than the first threshold compared with other AC impedance spectra are determined to be abnormal individual cells. When it is determined that the battery pack consistency is abnormal and the battery pack is a parallel battery pack, the connection point between the individual cell corresponding to the AC impedance spectrum that is smaller in ohmic impedance and has a difference greater than the second threshold and smaller in charge transfer impedance and has a difference greater than the first threshold and the individual cell in the positive and negative terminal directions of the battery pack is determined to be an abnormal connection point. When it is determined that the battery pack consistency is abnormal, and the battery pack is a series battery pack or multiple parallel battery modules connected in series, the connection point of the single cell or parallel battery module corresponding to the AC impedance spectrum that has a larger ohmic impedance and a difference greater than the second threshold, and a charge transfer impedance difference less than the first threshold, is identified as the abnormal connection point.

2. The method for detecting battery pack consistency according to claim 1, characterized in that, Determining the consistency of the battery pack by comparing the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or the multiple parallel battery modules includes: When the ohmic impedance and charge transfer impedance between all AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules meet preset conditions, the battery pack is determined to be in good consistency. The preset conditions are that, under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

3. The method for detecting battery pack consistency according to claim 1, characterized in that, Determining the battery pack consistency by comparing the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or the multiple parallel battery modules includes: When the ohmic impedance and charge transfer impedance between any AC impedance spectrum of the plurality of individual cells or the plurality of parallel battery modules and other AC impedance spectra do not meet preset conditions, the battery pack is determined to be inconsistent. The preset conditions are that, under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

4. A battery pack consistency detection device, wherein the battery pack comprises multiple individual cells or multiple parallel battery modules, and the multiple individual cells or the multiple parallel battery modules have connection points, characterized in that, The device is based on an electrochemical workstation with an auxiliary voltage divider module, and includes: The detection unit is used to simultaneously detect the AC impedance spectra of the multiple individual cells or the multiple parallel battery modules by means of the auxiliary voltage divider module, based on the AC signals with different frequencies and amplitudes less than a preset value applied to the battery pack by the electrochemical workstation. The processing unit is used to compare the ohmic impedance and charge transfer impedance corresponding to the AC impedance spectra of the multiple individual cells or the multiple parallel battery modules to determine the consistency of the battery pack. When the battery pack consistency is determined to be abnormal, and the battery pack is a parallel battery pack, the unit determines that the individual cells corresponding to the AC impedance spectra with a larger ohmic impedance (a difference greater than a second threshold) and a charge transfer impedance difference less than a first threshold compared to other AC impedance spectra are abnormal individual cells. When the battery pack consistency is determined to be abnormal, and the battery pack is a parallel battery pack, the unit determines that the ohmic impedance is smaller and the difference is larger compared to other AC impedance spectra. For the second threshold, the connection point between the individual cell corresponding to the AC impedance spectrum with a smaller charge transfer impedance and a difference greater than the first threshold and the individual cell in the positive and negative terminal directions of the battery pack is an abnormal connection point; when it is determined that the battery pack consistency is abnormal, and the battery pack is a series battery pack or multiple series parallel battery modules, the connection point at the end of the individual cell or parallel battery module corresponding to the AC impedance spectrum with a larger ohmic impedance and a difference greater than the second threshold and a charge transfer impedance difference less than the first threshold, other than the positive or negative terminal of the battery pack, is determined to be an abnormal connection point.

5. The battery pack consistency detection device according to claim 4, characterized in that, The processing unit is used for: When the ohmic impedance and charge transfer impedance between all AC impedance spectra of the plurality of individual cells or the plurality of parallel battery modules meet preset conditions, the battery pack is determined to be in good consistency. The preset conditions are that, under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

6. The battery pack consistency detection device according to claim 4, characterized in that, The processing unit is used for: When the ohmic impedance and charge transfer impedance between any AC impedance spectrum of the plurality of individual cells or the plurality of parallel battery modules and other AC impedance spectra do not meet preset conditions, the battery pack is determined to be inconsistent. The preset conditions are that, under the same frequency AC signal, the difference in charge transfer impedance is less than a first threshold and the difference in ohmic impedance is less than a second threshold.

Images