Battery pack pseudo soldering detection method, device, equipment and medium

Abstract

The invention relates to the technical field of batteries, in particular to a battery pack pseudo soldering detection method, device and equipment and a medium. The battery pack welding problem is judged through the electrochemical test, and if the battery pack has the pseudo soldering problem, the resistance is increased and the voltage difference between the battery cells is increased when the current bearing area on the battery cells is reduced and the battery pack is discharged through large current. With the increase of the internal resistance, short circuit may be caused and safety problems may be caused. The voltage difference range is set by performing the electrochemical test on the battery pack, the defective battery pack is quickly judged, the occurrence of the defective battery pack in the design verification stage is reduced, and meanwhile, the efficiency of checking the cold solder joint problem of the battery pack is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of batteries, and particularly to a method, device, equipment and medium for detecting virtual soldering of a battery pack. Background Art

[0002] With the development of new energy technologies, more and more new energy vehicles have come into people's view. As the power source of new energy vehicles, battery packs have been widely studied. The mass production of battery packs has also brought about many process problems. The consistency from battery cells to modules to the whole pack is the focus of people's attention.

[0003] As a new energy battery, lithium-ion batteries have been widely used in new energy vehicles due to their advantages such as high working voltage, high specific capacity, long charge and discharge life, and no memory effect. A battery pack is composed of monomers and then modules. Before the battery pack is formed, there are high requirements for the consistency of single battery cells, especially for lithium iron phosphate batteries. However, there are often problems of virtual soldering during the assembly process, resulting in an increasing voltage difference between battery cells, thereby reducing the capacity and energy of the whole pack. Further, due to the excessive internal resistance at a connection point of the battery cells, there may also be a situation of short circuit of the battery pack, causing safety risks.

[0004] Welding is a key link in the battery pack. At present, the main method for detecting whether the welding is qualified is pry inspection. However, if the strength is not enough, the problem cannot be eliminated. At the same time, there are also certain errors in manual operation, and the traditional detection of virtual soldering problems is accidental. Manual operation also requires the input of a certain amount of manpower.

[0005] In summary, there is an urgent need for an automated technical solution for detecting virtual soldering of a battery pack. Summary of the Invention

[0006] In view of the above problems, the present disclosure provides a method, device, equipment and medium for detecting virtual soldering of a battery pack.

[0007] In a first aspect, a method for detecting virtual soldering of a battery pack, the method includes:

[0008] Discharging and charging a battery pack assembled from battery cells of the same batch until the voltage of any single battery cell reaches the charging termination voltage, to obtain a battery pack to be detected;

[0009] Subjecting the battery pack to be detected to constant current discharge and large current pulse discharge until the voltage of any single battery cell reaches the discharge cut-off voltage;

[0010] Statistical voltage values of all battery cells in the battery pack at the end of discharge, statistically the highest voltage and the lowest voltage among the voltage values of all battery cells, calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference; when the maximum voltage difference is greater than a first preset threshold, it is determined that there is a possibility of virtual soldering in the battery pack.

[0011] Specifically, the preset threshold varies for different battery pack projects and has no specific value. Generally, it is set at 50 mV, and the standard will be adjusted according to the data of the first 200 battery packs off the production line.

[0012] Further, the voltage values of all the battery cells in the battery pack at the end of discharge are statistically counted and then replaced with:

[0013] Statistically count the highest voltage and the lowest voltage among the voltage values of all the battery cells, and calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference.

[0014] Statistically count the second-highest voltage and the second-lowest voltage among the voltage values of all the battery cells, and calculate the difference between the second-highest voltage and the second-lowest voltage, that is, the second-highest voltage difference.

[0015] When the difference between the maximum voltage difference and the second-highest voltage difference is greater than the second preset threshold, it is determined that there is a problem of loose soldering in the battery pack.

[0016] Further, for the battery packs assembled with battery cells of the same batch, they are discharged and charged respectively until the voltage of any single battery cell reaches the charging termination voltage, including:

[0017] The battery pack is discharged at a constant current to the discharge cut-off voltage at room temperature, the battery pack is left standing for a time T1, and the battery pack is charged using a fast charging strategy, where charging stops when the voltage of any single battery cell reaches the charging termination voltage.

[0018] Further, using a fast charging strategy to charge the battery pack, including:

[0019] The fast charging current is not greater than the charging capacity of the battery cell, and liquid cooling and liquid heating are turned on during the charging process to keep the battery cell in the best charging state.

[0020] Further, the battery pack to be tested is discharged at a constant current and discharged with a large current pulse until the voltage of any single battery cell reaches the discharge cut-off voltage, including:

[0021] Discharge at a constant current until the SOC reaches a ratio of K, leave it standing for a time T2, perform a large current pulse discharge on the battery pack, with a discharge time of T3, leave it standing for a time T4 after the pulse ends, and then continue to discharge at a constant current until the voltage of any single battery cell reaches the discharge cut-off voltage.

[0022] Further, the constant current is 1I1 (A), the charging cut-off voltage is 3800 mV, and the discharge cut-off voltage is 2500 Mv. Here, I1 (A) represents the 1-hour rate discharge current, and its value is equal to the 1-hour rate rated capacity Ah.

[0023] Further, the large current pulse discharge uses the current value corresponding to the maximum power that the battery pack can provide when applied to the vehicle.

[0024] Second aspect, a device for detecting virtual soldering of a battery pack, comprising:

[0025] A preprocessing unit, a discharging unit and a statistical detection unit;

[0026] The preprocessing unit is configured to discharge and charge a battery pack assembled from battery cells of the same batch until the voltage of any single battery cell reaches the charging termination voltage, so as to obtain a battery pack to be detected;

[0027] The discharging unit is configured to discharge the battery pack to be detected by constant current discharging and large current pulse discharging until the voltage of any single battery cell reaches the discharging cut-off voltage;

[0028] The statistical detection unit is configured to statistically calculate the voltage values of all battery cells in the battery pack at the end of discharging, statistically calculate the highest voltage and the lowest voltage among the voltage values of all battery cells, and calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference; when the maximum voltage difference is greater than a first preset threshold, it is determined that there is a possibility of virtual soldering in the battery pack.

[0029] Third aspect, an electronic device, comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory complete communication with each other through the communication bus;

[0030] The memory stores a computer program;

[0031] The processor is configured to implement the above-mentioned method for detecting virtual soldering of a battery pack when executing the computer program stored on the memory.

[0032] Fourth aspect, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned method for detecting virtual soldering of a battery pack is implemented.

[0033] The present disclosure at least includes the following beneficial effects:

[0034] The present disclosure determines the soldering problem of the battery pack through electrochemical testing. If there is a virtual soldering problem in the battery pack, due to the reduction of the current-carrying area on the battery cell, when the battery pack is discharged with a large current, the resistance increases and the voltage difference between the battery cells increases. With the increase of the internal resistance, short circuit may be caused, bringing safety problems. The present disclosure sets a voltage difference range through electrochemical testing of the battery pack, quickly determines the problematic battery pack, reduces the occurrence of problematic battery packs in the design verification stage, and improves the efficiency of troubleshooting the virtual soldering problem of the battery pack.

[0035] Other features and advantages of the present disclosure will be described in the following description, and some of them will be obvious from the description, or understood by implementing the present disclosure. The objectives and other advantages of the present disclosure can be realized and obtained by the structures pointed out in the description and the drawings. Description of the Drawings

[0036] To more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic flow chart of the detection method in the embodiments of the present disclosure;

[0038] Figure 2 It is a schematic structural diagram of the detection device in the embodiments of the present disclosure;

[0039] Figure 3 It is a schematic structural diagram of the electronic device in the embodiments of the present disclosure. Specific embodiments

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present disclosure with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present disclosure.

[0041] As Figure 1 shown, a method for detecting virtual soldering of a battery pack, the method includes:

[0042] S101, for the battery packs assembled from the same batch of battery cells, discharge and charge them respectively until the voltage of any single battery cell reaches the charging termination voltage to obtain the battery pack to be detected;

[0043] S102, subject the battery pack to be detected to constant current discharge and large current pulse discharge until the voltage of any single battery cell reaches the discharge cut-off voltage;

[0044] S103, count the voltage values of all the battery cells in the battery pack at the end of the discharge, count the highest voltage and the lowest voltage among all the voltage values of the battery cells, calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference; when the maximum voltage difference is greater than the first preset threshold, it is determined that there is a possibility of virtual soldering in the battery pack.

[0045] Specifically, the implementation is as follows:

[0046] At room temperature, discharge the battery pack at a current of 1I1(A) until the discharge cut-off voltage. After the battery pack is left standing for a period of time, charge the battery pack according to the fast charge strategy. Considering the loss from the single cell to the battery pack, the fast charge current is not greater than the charging capacity of the single cell. During the charging process, turn on the liquid cooling and heating to keep the single cell in the optimal charging state. Stop charging when the voltage of any single cell reaches the charging termination voltage. Leave it standing for 30 min (i.e., T1), discharge at a current of 1I1(A) until the SOC reaches 20% (i.e., ratio K), leave it standing for 30 min (i.e., T2), apply a large current to the battery pack for pulsed discharge, with a discharge time of 10 s (i.e., T3). After the pulse ends, leave it standing for 30 min (i.e., T4), and then continue to discharge at a current of 1I1(A) until the voltage of any single cell reaches the discharge cut-off voltage. If there is a problem of loose welding in the battery pack, due to the reduced current-carrying area on the single cell, when discharging the battery pack with a large current, the resistance increases and the voltage difference between the single cells increases.

[0047] Analyze the off-line test data of the battery packs assembled from the single cells of the same batch, with the number of battery pack samples ≥ 30 sets. Statistically record the voltage values of all the single cells in the battery pack at the end of discharge, and calculate the difference between the highest voltage and the lowest voltage.

[0048] Compare the voltage differences of the problem battery packs and the normal battery packs. It is found that when discharging the problem battery packs with a large current, although some of the problem single cells may show an outlier problem, the voltage difference is still within the normal range. Therefore, a second judgment is added, that is, statistically record the difference between the second highest voltage and the second lowest voltage, and then compare the difference between the maximum voltage difference and the second highest voltage difference. Increasing the sample size will show that the maximum voltage difference and the second highest voltage difference of the normal battery packs are close and ≤ 10 mV (i.e., the second preset threshold). Therefore, if there is a problem of loose welding in the battery pack, adding the judgment of the highest voltage difference and the second highest voltage difference after the pulsed discharge ends can improve the efficiency and accuracy of troubleshooting the battery pack problems.

[0049] The battery is a lithium iron phosphate battery, and the single cells are of the same batch.

[0050] The charging cut-off voltage is 3800 mV, and the discharge cut-off voltage is 2500 mV. Room temperature is 25 ± 3°C.

[0051] The pulsed discharge current is the current value corresponding to the maximum power that the battery pack can provide when applied to the whole vehicle.

[0052] The difference between the highest voltage difference and the second highest voltage difference is the voltage value statistically recorded for all the single cells at the end of the pulsed discharge.

[0053] As Figure 2 shown, a device for detecting loose welding of a battery pack includes:

[0054] A pretreatment unit 201, a discharge unit 202, and a statistical detection unit 203;

[0055] A preprocessing unit 201, configured to discharge and charge a battery pack assembled from battery cells of the same batch until the voltage of any single battery cell reaches the charging termination voltage, so as to obtain a battery pack to be detected;

[0056] A discharging unit 202, configured to discharge the battery pack to be detected by using constant current discharging and high current pulse discharging until the voltage of any single battery cell reaches the discharging cut-off voltage;

[0057] A statistical detection unit 203, configured to count the voltage values of all the battery cells in the battery pack at the end of discharging, count the highest voltage and the lowest voltage among the voltage values of all the battery cells, and calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference; when the maximum voltage difference is greater than a first preset threshold, it is determined that there is a possibility of false soldering in the battery pack.

[0058] As Figure 3 shown, the present disclosure provides an electronic device, including a processor 301, a communication interface 302, a memory 303, and a communication bus 304, wherein the processor 301, the communication interface 302, and the memory 303 complete mutual communication through the communication bus 304;

[0059] The memory 303 stores a computer program;

[0060] The processor 301 is configured to implement the above method when executing the computer program stored on the memory 303.

[0061] The present disclosure provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the above method is implemented.

[0062] The computer-readable storage medium may be included in the device / apparatus described in the above embodiments; or it may exist alone without being assembled into the device / apparatus. The above computer-readable storage medium carries one or more programs, and when the one or more programs are executed, the method according to the embodiments of the present disclosure is implemented.

[0063] According to an embodiment of the present disclosure, the computer-readable storage medium may be a non-volatile computer-readable storage medium, for example, it may include but is not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present disclosure, the computer-readable storage medium may be any tangible medium that contains or stores a program, and the program may be used by or in combination with an instruction execution system, device, or apparatus.

[0064] To enable those skilled in the art to better understand the present disclosure, the principles of the present disclosure are described below with reference to the accompanying drawings:

[0065] As Figure 1 shown, the series-parallel connection mode of the battery cells in the battery pack is 1P110S, and the cooling mode of the battery pack is liquid cooling and liquid heating. At room temperature, a charge-discharge test is performed on it. After discharging to 20% SOC, a 10s high-current pulse is applied to the battery pack, and then the maximum voltage difference and the second-highest voltage difference of all monomers at the end of the discharge are counted. If the difference between the two is greater than 10mv (i.e., the second preset threshold), it indicates that there may be a problem of virtual soldering in the battery pack, and the battery pack cannot be shipped. The data is exported to professional engineers for further analysis.

[0066] The voltages of all monomers within a certain period of time at the end of charge and discharge are plotted, and the voltages corresponding to all monomers are analyzed to determine the position of the problematic battery cell; according to the 24-bit code of the battery cell, the shipping inspection data of the battery cell is traced, and the capacity of the single battery cell and the voltage and capacity of the entire battery pack are analyzed to eliminate the influence of the battery cell. Then, combined with the position of the voltage acquisition point, it is found that the position of the problematic battery cell is the busbar welding position. Preliminary investigation shows that the increase in the resistance of this battery cell is caused by the module welding reason, so as to quickly find the cause of the problem.

[0067] Although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A method for detecting virtual soldering of a battery pack, characterized in that, The method includes: For battery packs assembled with cells of the same batch, discharge and charge them respectively until the voltage of any single cell reaches the charge termination voltage to obtain the battery pack to be detected; Apply constant current discharge and high current pulse discharge to the battery pack to be detected until the voltage of any single cell reaches the discharge cut-off voltage; Statistically record the voltage values of all cells in the battery pack at the end of discharge, statistically record the highest voltage and the lowest voltage among the voltage values of all cells, calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference; when the maximum voltage difference is greater than the first preset threshold, it is determined that there is a possibility of a loose weld in the battery pack.

2. The method for detecting loose welds in a battery pack according to claim 1, wherein: Statistically record the voltage values of all cells in the battery pack at the end of discharge, and then replace it with: Statistically record the highest voltage and the lowest voltage among the voltage values of all cells, calculate the difference between the highest voltage and the lowest voltage, that is, the maximum voltage difference; Statistically record the second highest voltage and the second lowest voltage among the voltage values of all cells, calculate the difference between the second highest voltage and the second lowest voltage, that is, the second highest voltage difference; When the difference between the maximum voltage difference and the second highest voltage difference is greater than the second preset threshold, it is determined that there is a loose weld problem in the battery pack.

3. The method for detecting loose welds in a battery pack according to claim 1, wherein: For battery packs assembled with cells of the same batch, discharging and charging them respectively until the voltage of any single cell reaches the charge termination voltage includes: The battery pack is discharged at a constant current to the discharge cut-off voltage at room temperature, the battery pack is left standing for a time T1, and a fast charge strategy is used to charge the battery pack, and charging stops when the voltage of any single cell reaches the charge termination voltage.

4. The method for detecting loose welds in a battery pack according to claim 3, wherein: Using a fast charge strategy to charge the battery pack includes: The fast charge current is not greater than the charging capacity of the cell, and liquid cooling and liquid heating are turned on during the charging process to keep the cell in the optimal charging state.

5. The method for detecting loose welds in a battery pack according to claim 1, wherein: Applying constant current discharge and high current pulse discharge to the battery pack to be detected until the voltage of any single cell reaches the discharge cut-off voltage includes: Discharge at a constant current until the SOC reaches a ratio of K, leave it standing for a time T2, perform high current pulse discharge on the battery pack, the discharge time is T3, leave it standing for a time T4 after the pulse ends, and then continue to discharge at a constant current until the voltage of any single cell reaches the discharge cut-off voltage.

6. The method for detecting loose welds in a battery pack according to claim 3 or 5, wherein: The constant current is 1I1 (A), the charge cut-off voltage is 3800 mV, and the discharge cut-off voltage is 2500 Mv, where I1 (A) represents the 1-hour rate discharge current, and its value is equal to the 1-hour rate rated capacity Ah.

7. The method for detecting loose welds in a battery pack according to claim 1, wherein: The high current pulse discharge uses the current value corresponding to the maximum power that the battery pack can provide when applied to the vehicle.

8. A virtual soldering detection device for a battery pack, characterized in that, It includes: A preprocessing unit, a discharge unit, and a statistical detection unit; The preprocessing unit is used to discharge and charge respectively the battery packs assembled with cells of the same batch until the voltage of any single cell reaches the charge termination voltage to obtain the battery packs to be detected; A discharge unit, configured to discharge a battery pack to be detected by constant current discharge and high current pulse discharge until the voltage of any single cell reaches the discharge cut-off voltage; A statistical detection unit, configured to count the voltage values of all the battery cells in the battery pack at the end of the discharge, count the highest voltage and the lowest voltage among the voltage values of all the battery cells, calculate the difference between the highest voltage and the lowest voltage, i.e., the maximum voltage difference; when the maximum voltage difference is greater than a first preset threshold, it is determined that there is a possibility of a loose weld in the battery pack.

9. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus. Among them, the processor, the communication interface, and the memory complete mutual communication through the communication bus; The memory stores a computer program; The processor is configured to implement a method for detecting loose welds in a battery pack according to any one of claims 1-7 when executing the computer program stored on the memory.

10. A computer-readable storage medium storing a computer program, characterized in that, The computer program, when executed by the processor, implements a method for detecting loose welds in a battery pack according to any one of claims 1-7.

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