Testing device and method for monitoring battery consistency on line

Abstract

According to the testing device and method for online monitoring battery consistency evaluation of the new energy automobile, the data acquisition speed of 100 k / s can be achieved, impedance changes of all electrochemical processes in the microsecond-second level are captured, and by comparing the impedance differences of all batteries under different # imgabs0 #, the consistency of the batteries is evaluated, so that the consistency of the batteries is evaluated, and the consistency of the batteries is evaluated. Therefore, the consistency of the battery can be evaluated in a more refined manner. The testing device comprises a charging and discharging instrument connected with a to-be-tested battery and a high-flux data collecting and processing system, and the high-flux data collecting and processing system comprises a high-frequency current and voltage data collecting module connected with the positive electrode and the negative electrode of the to-be-tested battery. And the data processing and consistency analysis module is connected with the high-frequency current and voltage data acquisition module. The test method is applied to the test device, and particularly relates to a high-frequency current and voltage data acquisition module and a data processing and consistency analysis module.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery consistency monitoring, and in particular relates to a testing device and method for online monitoring of battery consistency. Background Art

[0002] In new energy vehicles, nearly a hundred lithium-ion batteries are often used in series or parallel. Therefore, the consistency between the batteries in the battery pack is very important. Otherwise, the failure of a battery is likely to cause the entire car to catch fire. Therefore, an effective way to evaluate the consistency between the batteries in the battery pack of new energy vehicles is urgently needed.

[0003] At present, the parameters commonly used to evaluate the consistency between batteries are: open circuit voltage, DC internal resistance and temperature of the battery. These parameters are relatively rough and not precise enough, especially for lithium iron phosphate batteries, whose voltage platform is relatively flat, so open circuit voltage cannot effectively evaluate their consistency.

[0004] The battery consistency evaluation method disclosed in patent CN117805629A only performs consistency evaluation through parameters such as voltage and 1000Hz internal resistance, which is not comprehensive enough and cannot achieve online evaluation. Summary of the invention

[0005] The main purpose of the present invention is to provide a testing device and method for online monitoring of battery consistency, which can solve the problems existing in the prior art and achieve faster data acquisition speed, so as to capture the impedance changes of various electrochemical processes within subtle to second levels, thereby achieving more precise battery consistency evaluation.

[0006] In order to achieve the above object, one of the solutions of the present invention is: A test device for online monitoring of battery consistency, comprising a charge and discharge instrument connected to a battery to be tested and a high-throughput data acquisition and processing system; the high-throughput data acquisition and processing system comprises a high-frequency current and voltage data acquisition module connected to the positive and negative electrodes of the battery to be tested, and a data processing and consistency analysis module connected to the high-frequency current and voltage data acquisition module; The high-frequency current and voltage data acquisition module uses a 5V DC constant current source as input, and sends the data to the single-chip microcomputer circuit after DAC adjustment, integral / differential amplifier, 1.3M SPS ADC high-frequency sampling, low-delay filtering and data frame packaging. The single-chip microcomputer circuit has the functions of timer timing control, system parameter initialization and communication transceiver; The calculation and analysis logic of the data processing and consistency analysis module is as follows: after the data is input, the current change moment is determined as the change point, and the current before and after the change point is extracted. The current and voltage data of 10 seconds are collected, and then Laplace transform is performed on the current and voltage data to calculate the average equivalent impedance, and then the overall impedance is calculated. The consistency of the batteries is compared through the overall impedance, and finally the abnormal batteries are screened out according to the comparison results.

[0007] The second solution of the present invention is: A method for online monitoring of battery consistency, using the test device, comprising: Step 1: Signal acquisition Use charging current When the battery under test is charged with constant current, the charging current is changed to and continue seconds, and at the next moment change the charging current to and continue seconds, of which The current and voltage signals are collected by the high-throughput data acquisition and processing system with a sampling frequency of 100kHz and a sampling accuracy of 0.02% of the current and voltage. ,Voltage Over time The changing curve and ; Step 2: Data processing In the data processing and consistency analysis module, Laplace transform is used to and Analyze the time domain data into frequency domain data and obtain and , and calculate the equivalent impedance , and its calculation formula is as follows: ; ; ; in, represents the angular frequency; represents the base of natural logarithms; represents the convergence region of the Laplace transform; represents the imaginary unit; Select Characteristic angular frequency to The average equivalent impedance of the battery is The average equivalent impedance in the state , At least 3, and the calculation formula is as follows: ; Step 3: Cycle test Cycle Steps 1 and 2 are performed to test the battery. The average equivalent impedance under , to achieve different battery Real-time, online battery consistency evaluation is performed based on the impedance under load.

[0008] In the step 2, 3, 3 characteristic angular frequencies , and They are 1300rad / s, 130rad / s and 13rad / s respectively.

[0009] The battery consistency evaluation is selected , , and These four different , calculate the overall impedance of the battery , and its calculation formula is as follows: ; Then, the overall impedance of different batteries is calculated distribution, and specify the upper and lower specification lines; if a battery exceeds the overall impedance If the upper and lower specification lines are not within the specified range, it indicates that the battery has poor consistency and a warning is required.

[0010] After adopting the above technical solution, the present invention has the following technical effects: ① Ability to realize online detection - the equivalent impedance can be tested and the consistency of the battery can be evaluated without stopping charging; ② Wider applicability: Since batteries are charged and discharged in the form of DC, they can be extended to the BMS of new energy vehicles; ③Higher accuracy - overall impedance Combining different frequency bands, different The electrochemical impedance information under the condition reflects the electrochemical process inside the battery more comprehensively, thus improving the screening accuracy; ④Lower cost, large-scale full inspection can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of a testing device according to a specific embodiment of the present invention.

[0012] Figure 2 This is a functional design diagram of a high-frequency current and voltage data acquisition module according to a specific embodiment of the present invention.

[0013] Figure 3 It is a calculation and analysis logic diagram of the data processing and consistency analysis module of a specific embodiment of the present invention.

[0014] Figure 4 The test logic and flow chart of a specific embodiment of the present invention.

[0015] Figure 5 is a current and voltage curve diagram obtained during testing of a specific embodiment of the present invention; wherein, Figure 5 (a) Five different The average equivalent impedance under The curve diagram of the current and voltage changing with time during the test. Figure 5 (b) The third test A partial enlarged view of the current and voltage curves when .

[0016] Figure 6 The overall impedance of 45 batteries tested in the specific embodiment of the present invention is Distribution map of . DETAILED DESCRIPTION

[0017] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0018] During the charge and discharge process, if the battery is stimulated by an additional, instantaneous current, its internal balance will be destroyed, causing more electrochemical behaviors of electrons or ions, including electrons flowing from the external current, lithium ions passing through the SEI membrane, and charge transfer between lithium ions and electrons. Some processes are very fast and are completed in microseconds or milliseconds, such as the transportation of electrons; some processes are relatively slow and take hundreds of milliseconds to complete, such as the process of lithium ions passing through the SEI membrane; and some processes are even slower and take seconds to complete, such as the charge transfer process between lithium ions and electrons.

[0019] Based on this principle, the present invention proposes a method for online monitoring battery consistency evaluation for new energy vehicles, which can achieve a data acquisition speed of 100k / s, thereby capturing the impedance changes of various electrochemical processes within microseconds to seconds, and comparing different The impedance difference of each battery can be measured to achieve a more refined evaluation of battery consistency.

[0020] Since lithium-ion batteries are charged and discharged in a direct current process, and the present invention is also based on direct current, consistency evaluation can be achieved during the battery charging and discharging process, that is, online and real-time evaluation can be achieved.

[0021] The present invention discloses a method for online monitoring of battery consistency. Figure 1 The test device includes a charge and discharge instrument connected to the battery to be tested and a high-throughput data acquisition and processing system; the high-throughput data acquisition and processing system includes a high-frequency current and voltage data acquisition module connected to the positive and negative electrodes of the battery to be tested, and a data processing and consistency analysis module connected to the high-frequency current and voltage data acquisition module.

[0022] See also Figure 2 The high-frequency current and voltage data acquisition module uses a 5V DC constant current source as input, and after DAC adjustment, integral / differential amplifier, 1.3M SPS ADC high-frequency sampling, low-latency filtering and data frame packaging, the data is sent to the single-chip microcomputer circuit. The single-chip microcomputer circuit has the functions of timer timing control, system parameter initialization and communication transceiver. In this embodiment, the 1.3M SPS ADC high-frequency sampling part uses TI's ADS127L18 analog-to-digital conversion chip, which can have a data rate of up to 1.3M SPS when using a low-latency filter, and has the advantages of excellent AC performance, DC accuracy and low power consumption; the data frame packaging part uses a SPI (serial peripheral interface) serial peripheral interface with a clock frequency of more than 30MHz to meet high-throughput data transmission; the single-chip microcomputer circuit uses a 32-bit Arm®Cortex®-M7 CPU with a processing frequency of up to 550MHz to meet the timely calculation and processing of high-throughput data.

[0023] See also Figure 3 , the calculation and analysis logic of the data processing and consistency analysis module is: After the data is input, the current change moment is determined as the change point, and the current before and after the change point is extracted. The current and voltage data of 10 seconds are collected, and then Laplace transform is performed on the current and voltage data to calculate the average equivalent impedance, and then the overall impedance is calculated. The consistency of the batteries is compared through the overall impedance, and finally the abnormal batteries are screened out according to the comparison results.

[0024] See also Figure 4 , the specific steps of the method are as follows: Step 1: Signal acquisition For a battery, if it can be fully charged with a certain current for 1 hour, then this current is the 1C rate current of the battery. Taking a 20Ah lithium iron phosphate battery as an example, if you want to fully charge the battery in 1 hour, you need a 20A current for constant current charging, then the 1C rate current of the 20Ah lithium iron phosphate battery is 20A.

[0025] When a 20Ah lithium iron phosphate battery is charged at a current of 10A When constant current charging is performed, the charging current is changed to and continue seconds, and at the next moment change the charging current to and continue seconds to ensure that the average charging current remains at 10A, where It is 1 / 10 of the 1C rate current. During the whole process, the current and voltage signals are collected by using a high-throughput data acquisition and processing system. The sampling frequency is 100kHz, and the sampling accuracy of current and voltage is 0.02%. For 10 seconds, the current can be obtained ,Voltage Over time The changing curve and , see Figure 5 .

[0026] Step 2: Data processing In the data processing and consistency analysis module, Laplace transform is used to and Analyze the time domain data into frequency domain data and obtain and , and calculate the equivalent impedance , and its calculation formula is as follows: ; ; ; in, represents the angular frequency; represents the base of natural logarithms; represents the convergence region of the Laplace transform; Represents the imaginary unit.

[0027] For large capacity batteries, select Characteristic angular frequency to The average equivalent impedance of the battery is The average equivalent impedance in the state , At least 3, and the calculation formula is as follows: .

[0028] In this embodiment, the above 3, 3 characteristic angular frequencies , and They are 1300rad / s, 130rad / s and 13rad / s respectively, which can effectively represent the impedance encountered by the three electrochemical processes of the battery: electron migration, ion migration, and charge transfer between electrons and ions.

[0029] Step 3: Cycle test Cycle Steps 1 and 2 are performed to test the battery. The average equivalent impedance under , to achieve different battery Real-time, online diagnosis and evaluation of impedance.

[0030] In this embodiment, five different charging steps are performed during the entire continuous charging process. The average equivalent impedance under The curves of current and voltage changing with time during the test are as follows: Figure 5 As shown in (a), Figure 5 (b) Yes Figure 5 (a) is a partial enlarged view of the current and voltage curves during the third test.

[0031] In the battery consistency evaluation, the present invention selects , , and These four different , calculate the overall impedance of the battery , and its calculation formula is as follows: ; Then, the overall impedance of different batteries is calculated distribution, and specify the upper and lower specification lines; if a battery exceeds the overall impedance If the upper and lower specification lines are not within the specified range, it indicates that the battery has poor consistency and a warning is required. Figure 6 Shows the overall impedance of forty-five batteries The distribution of cells, among which there are seven inconsistent cells, achieves effective screening.

[0032] Through the above scheme, the present invention has the following advantages: ① Ability to realize online detection - the equivalent impedance can be tested and the consistency of the battery can be evaluated without stopping charging; ② Wider applicability: Since batteries are charged and discharged in the form of DC, they can be extended to the BMS of new energy vehicles; ③Higher accuracy - overall impedance Combining different frequency bands, different The electrochemical impedance information under the condition reflects the electrochemical process inside the battery more comprehensively, thus improving the screening accuracy; ④Lower cost, large-scale full inspection can be carried out.

[0033] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A test device for online monitoring of battery consistency, characterized in that: It includes a charging and discharging instrument connected to the battery to be tested and a high-throughput data acquisition and processing system; the high-throughput data acquisition and processing system includes a high-frequency current and voltage data acquisition module connected to the positive and negative electrodes of the battery to be tested, and a data processing and consistency analysis module connected to the high-frequency current and voltage data acquisition module; The high-frequency current and voltage data acquisition module takes a 5V DC constant current source as input, and sends the data to the single-chip microcomputer circuit after DAC adjustment, integral / differential amplifier, 1.3M SPS ADC high-frequency sampling, low-delay filtering and data frame packaging. The single-chip microcomputer circuit has the functions of timer timing control, system parameter initialization and communication transceiver; The calculation and analysis logic of the data processing and consistency analysis module is as follows: after the data is input, the current change moment is determined as the change point, and the current before and after the change point is extracted. The current and voltage data of 10 seconds are collected, and then Laplace transform is performed on the current and voltage data to calculate the average equivalent impedance, and then the overall impedance is calculated. The consistency of the batteries is compared through the overall impedance, and finally the abnormal batteries are screened out according to the comparison results.

2. A method for online monitoring of battery consistency, using the online monitoring of battery consistency testing device as claimed in claim 1, characterized in that include: Step 1: Signal acquisition Use charging current When the battery under test is charged with constant current, the charging current is changed to and continue seconds, and at the next moment change the charging current to and continue seconds, of which The current and voltage signals are collected by the high-throughput data acquisition and processing system with a sampling frequency of 100kHz and a sampling accuracy of 0.02% of the current and voltage. ,Voltage Over time The changing curve and ; Step 2: Data processing In the data processing and consistency analysis module, Laplace transform is used to and Analyze the time domain data into frequency domain data and obtain and , and calculate the equivalent impedance , and its calculation formula is as follows: ； ； ； in, represents the angular frequency; represents the base of natural logarithms; represents the convergence region of the Laplace transform; represents the imaginary unit; Select Characteristic angular frequency to The average equivalent impedance of the battery is taken as The average equivalent impedance in the state , At least 3, and the calculation formula is as follows: ； Step 3: Cycle test Cycle Steps 1 and 2 are performed to test the battery. The average equivalent impedance under , to achieve different battery Real-time, online battery consistency evaluation is performed based on the impedance under load.

3. The method for online monitoring of battery consistency according to claim 2, characterized in that: In the step 2, 3, 3 characteristic angular frequencies , and They are 1300rad / s, 130rad / s and 13rad / s respectively.

4. The method for online monitoring of battery consistency according to claim 2, characterized in that: The battery consistency evaluation is selected , , and These four different , calculate the overall impedance of the battery , and its calculation formula is as follows: ； Then, the overall impedance of different batteries is calculated distribution, and specify the upper and lower specification lines; if a battery exceeds the overall impedance If the upper and lower specification lines are not within the specified range, it indicates that the battery has poor consistency and a warning is required.

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