A lithium-ion battery peak current estimation and testing method

Abstract

The present invention relates to the technical field of lithium ion battery testing, and discloses a lithium ion battery peak current estimation and testing method, comprising the following steps: respectively estimating the initial value of the charge / discharge test current; S2: performing response voltage determination processing on the initial value of the charge / discharge test current, and judging whether the response voltage of the initial value of the charge / discharge test current meets the charge / discharge test requirements; S3: if the charge / discharge test requirements are met, the initial value of the charge / discharge test current is the maximum charge / discharge current value of the tested lithium ion battery; if the charge / discharge test requirements are not met, the initial value of the charge / discharge test current is subjected to current test value iteration processing to obtain the charge / discharge test current iteration value; S4: performing response voltage determination processing on the charge / discharge test current iteration value to obtain the maximum charge / discharge current value of the tested lithium ion battery. The present invention estimates the initial value and iteratively adjusts the test current, reduces human intervention, and improves test accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery testing, and in particular to a lithium ion battery peak current estimation and testing method. Background Art

[0002] The peak current test of lithium-ion batteries, namely the charging MAP (Maximum Available Power, MAP for short) and the discharging MAP test, is used to find the maximum charging current and maximum discharging current of the battery. Taking the discharge test as an example, given a certain value of current, if the response voltage at a certain moment satisfies: discharge cut-off voltage < response voltage < discharge cut-off voltage + redundancy, then the current value at this moment is the maximum value that meets the requirements, otherwise the current value is corrected to continue the test.

[0003] In order to make the charging MAP and discharging MAP cover various geographical environments and various extreme operating conditions in my country as much as possible, it is usually required to test multiple combinations of test points. The test process includes multiple steps, and the duration of each step can be classified into fixed time and variable time. The variable time is related to the number of tests. If the initial test current does not meet the requirements, it will take a certain period of time to adjust the state and stand still before testing again until a current test value that meets the conditions is obtained. That is, the variable time increases exponentially with the number of tests.

[0004] At the same time, considering that the current charging MAP and discharging MAP tests mostly use manual trial and error methods, the test efficiency and accuracy are greatly limited. When the initial test current value cannot be determined, the test personnel need to make subjective judgments to give the initial current test value, and when adjusting, the current value is increased or decreased by subjective judgment (that is, relying on experienced skilled technicians). Therefore, the success rate of the first test is usually low, and the actual number and duration of tests may far exceed expectations, increasing the test cost and time cost. Summary of the invention

[0005] The purpose of the present invention is to provide a lithium-ion battery peak current estimation and testing method to solve the problem that the peak current test cannot accurately predict the current value of the initial test and the subsequent adjustment relies on subjective judgment, resulting in low test efficiency.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A lithium-ion battery peak current estimation and testing method comprises the following steps:

[0008] S1: Estimate the initial value of the charge / discharge test current based on the historical measured data of the lithium-ion battery under test;

[0009] S2: performing response voltage determination processing on the initial value of the charge / discharge test current to determine whether the response voltage of the initial value of the charge / discharge test current meets the charge / discharge test requirement;

[0010] S3: If the charge / discharge test requirements are met, the initial value of the charge / discharge test current is the maximum charge / discharge current value of the lithium-ion battery under test; if the charge / discharge test requirements are not met, the initial value of the charge / discharge test current is iteratively processed as a current test value to obtain an iterative value of the charge / discharge test current;

[0011] S4: performing response voltage determination processing on the charge / discharge test current iteration value to obtain the maximum charge / discharge current value of the tested lithium-ion battery.

[0012] According to the above technical means, the present invention makes full use of the historical measured data of the lithium-ion battery under test to scientifically estimate the initial value of the predicted test current. Compared with the traditional manual experience judgment, it can be closer to the actual performance of the battery, thereby greatly improving the accuracy of the initial test current value and reducing the number of invalid tests caused by improper initial value setting.

[0013] During the test process, the current test value is iteratively processed. The present invention can automatically adjust the test current value through preset algorithms and logics without relying too much on the subjective judgment of the inspectors. This not only reduces the workload of the inspectors, but also avoids errors introduced by human factors, thereby improving the objectivity and consistency of the test.

[0014] In the discharge test, as the current increases, the battery voltage will gradually decrease; similarly, in the charging test, as the current increases, the battery voltage will gradually rise. The present invention performs precise voltage measurement for each test current iteration value to record the response voltage of the battery. By actually measuring the response voltage of the battery, the performance of the battery under different currents can be more directly observed. If at a certain test current iteration value, the response voltage of the battery remains within the set threshold or range, and further increasing the current will cause the voltage to exceed the threshold or range, then the test current iteration value is considered to be the maximum charging current value (for charging test) or the maximum discharge current value (for discharge test) of the battery.

[0015] The present invention reduces the number of invalid tests and the time for manual adjustment, so that the process of the entire peak current test is accelerated, thereby significantly improving the test efficiency.

[0016] Furthermore, the S1 step specifically includes:

[0017] S11: For the charge / discharge test, based on the historical measured data of the tested lithium-ion battery, a current / rate-internal resistance characteristic diagram of the tested lithium-ion battery at different states of charge, different temperatures and different health states is constructed;

[0018] S12: fitting a current / rate-internal resistance function relationship according to the current / rate-internal resistance characteristic diagram;

[0019] S13: Combining the voltage estimation formula with the current / rate-internal resistance function relationship, debugging is performed to obtain the initial value of the current according to the required cut-off voltage redundancy interval range.

[0020] According to the above technical means, by analyzing the historical measured data of the lithium-ion battery under test, a relationship diagram between the current / rate and the internal resistance under different charge states is constructed, and the data-driven method is fully utilized to capture the change law of the internal resistance of the battery under different states, providing a solid foundation for subsequent predictions. Based on the constructed current / rate-internal resistance characteristic diagram, a specific functional relationship is fitted through mathematical methods, and the complex experimental data is converted into a quantifiable mathematical model, which reduces human intervention and subjective judgment during the test. After obtaining the current / rate-internal resistance functional relationship, combined with the voltage estimation formula, the initial value of the current is debugged according to the required cut-off voltage redundant interval range, avoiding the problem of frequent adjustment of the current value during the test, thereby improving the test efficiency.

[0021] Furthermore, the historical measured data includes discharge capacity energy test data, rate charge and discharge test data, mixed pulse power characteristic test data, reference performance test data and any data captured and recorded by the system during battery use in actual application scenarios.

[0022] According to the above technical means, the present invention utilizes historical measured data including discharge capacity energy test data, rate charge and discharge test data, mixed pulse power characteristic test data and repeated pulse test data to construct a more comprehensive and accurate prediction model.

[0023] Furthermore, the step S12 specifically includes:

[0024] Based on the current / rate-internal resistance characteristic diagram obtained from historical data, the least squares method is used to construct t The internal resistance function relationship corresponding to the current of different rates at the moment is:

[0025] R ( t )= f ( I ( t )),

[0026] in, tFor any moment with the same charge / discharge duration at different current rates, I ( t )for t The test current at the moment, R ( t )for t The fitted internal resistance value at time, function f It is any one of a linear function, a quadratic function, an exponential function, a power function and a logarithmic function.

[0027] According to the above technical means,

[0028] Furthermore, the voltage estimation formula is:

[0029] V ( t )= V 0 - I ( t )* R ( t ),

[0030] in, V ( t )for t The estimated voltage value at time, V 0 for t The test current at the moment, I ( t )for t The fitting internal resistance value at time R ( t ) is the internal resistance.

[0031] Furthermore, the step S13 specifically includes: combining the voltage estimation formula with the current / rate-internal resistance function relationship, adjusting the test current I ( t ),like V ( t ) falls within the required cut-off voltage redundancy range, then I ( t ) is the initial value of the test current.

[0032] Furthermore, the test current iteration value is obtained by the following formula:

[0033] For the discharge test:

[0034] ,

[0035] in, I k ( t ) is the test current iteration value, Ik-1 ( t ) is the current value of the last test, t For any moment with the same charge / discharge duration at different current rates, V 01 is the open circuit voltage of the battery before discharge, V k-1 ( t ) is the response voltage of the previous test, V min1 is the discharge cut-off voltage, V max1 is the sum of the discharge cut-off voltage and the redundancy;

[0036] For charging test:

[0037] ,

[0038] in, I k ( t ) is the test current iteration value, I k-1 ( t ) is the current value of the last test, t For any moment with the same charge / discharge duration at different current rates, V 02 is the open circuit voltage of the battery before charging, V k-1 ( t ) is the response voltage of the previous test, V min2 is the difference between the charging cut-off voltage and the redundancy, V max2 is the charging cut-off voltage.

[0039] Furthermore, the charge / discharge test requirements include:

[0040] For discharge test: discharge cut-off voltage < response voltage < discharge cut-off voltage + redundancy;

[0041] For charging test: charging cut-off voltage - redundancy < response voltage < charging cut-off voltage.

[0042] Further, the S4 step includes:

[0043] S41: performing response voltage determination processing on the charge / discharge test current iteration value to determine whether the response voltage of the charge / discharge test current iteration value meets the charge / discharge test requirement;

[0044] S42: If the charge / discharge test requirements are met, the charge / discharge test current iteration value is the maximum charge / discharge current value of the lithium-ion battery being tested.

[0045] Furthermore, the S4 step further includes:

[0046] S42': If the charge / discharge test requirement is not met, return to step S3 according to the response voltage to re-acquire the charge / discharge test current iteration value.

[0047] Beneficial effects achieved by the present invention:

[0048] 1. Improve the accuracy of the initial test current value: The present invention makes full use of the historical measured data of the lithium-ion battery under test to scientifically estimate the initial value of the predicted test current. Compared with the traditional manual experience judgment, it can be closer to the actual performance of the battery, thereby greatly improving the accuracy of the test current value and reducing the number of invalid tests caused by improper initial value setting.

[0049] 2. Reduce human intervention and improve the degree of test automation: During the test process, the current test value is iteratively processed. The present invention can automatically adjust the test current value through preset algorithms and logics without relying too much on the subjective judgment of the inspectors. This not only reduces the workload of the inspectors, but also avoids errors introduced by human factors, thereby improving the objectivity and consistency of the test.

[0050] 3. Speed ​​up the test process and improve test efficiency: Since the present invention reduces the number of invalid tests and the time for manual adjustment, the process of the entire peak current test is accelerated, thereby significantly improving the test efficiency. The present invention can be applied to battery management systems to assist in predicting the available power of the battery under a specific state (state of charge, temperature, and health state). BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the steps of the present invention;

[0052] Figure 2 It is a schematic diagram of the application logic flow of the present invention;

[0053] Figure 3 This is a schematic diagram of the sub-steps of step S1 of the present invention;

[0054] Figure 4 This is a schematic diagram of the sub-steps of step S4 of the present invention.

[0055] The drawings are only used for illustrative purposes and should not be construed as limitations on this patent. In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The same or similar numbers correspond to the same or similar parts. The terms describing the positional relationship in the drawings are only used for illustrative purposes and should not be construed as limitations on this patent. DETAILED DESCRIPTION

[0056] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific embodiments should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the specific technical solution of the present application will be further described in detail below in conjunction with the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application, but are not used to limit the scope of the present application.

[0058] In the embodiments of the present application, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0059] The technical solution of the present invention is described in detail below in conjunction with the specific drawings.

[0060] like Figure 1 As shown, the present invention proposes a lithium-ion battery peak current estimation and testing method, comprising:

[0061] S1: Estimate the initial value of the charge / discharge test current based on the historical measured data of the lithium-ion battery under test;

[0062] S2: performing response voltage determination processing on the initial value of the charge / discharge test current to determine whether the response voltage of the initial value of the charge / discharge test current meets the charge / discharge test requirement;

[0063] S3: If the charge / discharge test requirements are met, the initial value of the charge / discharge test current is the maximum charge / discharge current value of the lithium-ion battery under test; if the charge / discharge test requirements are not met, the initial value of the charge / discharge test current is iteratively processed as a current test value to obtain an iterative value of the charge / discharge test current;

[0064] S4: performing response voltage determination processing on the charge / discharge test current iteration value to obtain the maximum charge / discharge current value of the tested lithium-ion battery.

[0065] The present invention makes full use of the historical measured data of the lithium-ion battery under test to scientifically estimate the initial value of the predicted test current. Compared with the traditional manual experience judgment, it can be closer to the actual performance of the battery, thereby greatly improving the accuracy of the initial test current value and reducing the number of invalid tests caused by improper initial value setting. During the test, the current test value is iteratively processed. The present invention can automatically adjust the test current value through preset algorithms and logics without relying too much on the subjective judgment of the inspector. It not only reduces the workload of the inspector, but also avoids errors introduced by human factors, thereby improving the objectivity and consistency of the test. Since the present invention reduces the number of invalid tests and the time for manual adjustment, the process of the entire peak current test is accelerated, thereby significantly improving the test efficiency.

[0066] The present invention is based on commercial battery testing software that is programmable and can customize the process steps. Through the linkage between the test bench and the incubator, the peak current test of lithium-ion batteries is carried out in combination with the above method. The overall logic is as follows: Figure 2 As shown, specifically:

[0067] S1: Estimate the initial value of the predicted test current based on the historical measured data of the lithium-ion battery under test, and preset the calculated initial current test value in the programmable process step file to achieve a well-founded initial current test value and reduce the total number of tests, such as Figure 3 As shown:

[0068] S11: Based on the historical measured data of the battery, such as the Hybrid Pulse Power Characterization (HPPC) test data, construct the current / rate (c)-internal resistance (R) characteristic diagram of the battery at different states of charge (SOC), different temperatures and different health states;

[0069] S12: Based on the current / rate-internal resistance characteristic diagram obtained from historical data, the internal resistance function relationship corresponding to the current of different rates at time t is constructed using the least squares method: R ( t )= f ( I ( t )),in, t For any moment with the same charge / discharge duration at different current rates, I ( t )for t The test current at the moment, R ( t )for t The fitting internal resistance value at the moment, the function type can be a linear function, a quadratic function, an exponential function, a power function, a logarithmic function, etc., preferably a quadratic polynomial function;

[0070] S13: Combined voltage estimation formula V ( t )= V 0 - I ( t )* R ( t ),in, V ( t )for t The estimated voltage value at time, V 0 is the battery open circuit voltage, I ( t )for t The test current at the moment, R ( t )for t The fitting internal resistance value at the moment, adjust the test current I ( t ),like V(t) If it falls within the required cut-off voltage redundancy range, then I ( t ) is the appropriate initial value of the test current.

[0071] S2: performing response voltage determination processing on the initial value of the charge / discharge test current to determine whether the response voltage of the initial value of the charge / discharge test current meets the charge / discharge test requirement;

[0072] Charge / discharge test requirements include:

[0073] For discharge test: discharge cut-off voltage < response voltage < discharge cut-off voltage + redundancy;

[0074] For charging test: charging cut-off voltage - redundancy < response voltage < charging cut-off voltage.

[0075] S3: If the charge / discharge test requirements are met, the initial value of the charge / discharge test current is the maximum charge / discharge current value of the lithium-ion battery under test; if the charge / discharge test requirements are not met, the initial value of the charge / discharge test current is iteratively processed with a current test value to obtain a charge / discharge test current iteration value; the test current iteration algorithm is preset in a programmable step file, the initial value is iteratively processed with a current test value to obtain a test current iteration value, which no longer relies on experienced operators, can decouple manpower, improve test accuracy, and reduce the total number of tests;

[0076] The test current iteration algorithm is shown as follows:

[0077] For the discharge test:

[0078] ,

[0079] in, I k ( t ) is the test current iteration value, I k-1 ( t ) is the current value of the last test, t For any moment with the same charge / discharge duration at different current rates, V 01 is the open circuit voltage of the battery before discharge, V k-1 ( t ) is the response voltage of the previous test, V min1 is the discharge cut-off voltage, V max1 is the sum of the discharge cut-off voltage and the redundancy value;

[0080] For charging test:

[0081] ,

[0082] in, I k ( t ) is the test current iteration value, I k-1 ( t ) is the current value of the last test, t For any moment with the same charge / discharge duration at different current rates, V 02 is the open circuit voltage of the battery before charging, V k-1 ( t ) is the response voltage of the previous test, V min2 is the difference between the charging cut-off voltage and the redundancy, V max2 is the charging cut-off voltage.

[0083] S4: Perform response voltage determination processing on the test current iteration value, load the customized process step file, link the test bench with the temperature chamber, automatically perform the test, and obtain the maximum charging current value and the maximum discharging current value of the tested lithium-ion battery, thereby avoiding the consumption of invalid time and reducing the total test time, such as Figure 4 As shown:

[0084] S41: performing response voltage determination processing on the charge / discharge test current iteration value to determine whether the response voltage of the charge / discharge test current iteration value meets the charge / discharge test requirement;

[0085] S42: If the charge / discharge test requirements are met, the charge / discharge test current iteration value is the maximum charge / discharge current value of the lithium-ion battery under test; if the charge / discharge test requirements are not met, return to step S3 according to the response voltage to re-acquire the charge / discharge test current iteration value.

[0086] Embodiment 1

[0087] This example uses the actual measurement of lithium iron phosphate battery to illustrate: discharge at 25°C, V ( t ) The qualified range is (2.5V, 2.65V), as shown in Table 1:

[0088] Table 1

[0089]

[0090] The test results showed that the initial predicted current accuracy was 55.6%, the second iteration current accuracy was 95%, the third iteration current accuracy was 100%, and the test time was reduced by more than 51.1%.

[0091] Embodiment 2

[0092] This example uses the actual measurement of lithium iron phosphate battery to illustrate: discharge at -20℃, V ( t ) The qualified interval is (2.0V, 2.15V), as shown in Table 2:

[0093] Table 2

[0094]

[0095] The test results showed that the initial predicted current accuracy was 33.3%, the second iteration current accuracy was 63.3%, the third iteration current accuracy was 100%, and the test time was reduced by more than 36.3%.

[0096] Embodiment 3

[0097] This embodiment uses the actual measurement of lithium iron phosphate battery to illustrate: charging at -5°C, the qualified range of V(t) is (3.5V, 3.65V), as shown in Table 3:

[0098] Table 3

[0099]

[0100] The test results showed that the initial predicted current accuracy was 77.8%, the secondary iterative current accuracy was 100%, and the test time was reduced by more than 38.9%.

[0101] Embodiment 4

[0102] This example uses the actual measurement of lithium iron phosphate battery to illustrate: charging at -10℃,V ( t ) The qualified range is (3.5V, 3.65V), as shown in Table 4:

[0103] Table 4

[0104]

[0105] The test results showed that the initial predicted current accuracy was 91.1%, the secondary iterative current accuracy was 100%, and the test time was reduced by more than 45.6%.

[0106] The serial numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments. The above are only preferred embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A lithium-ion battery peak current estimation and testing method, characterized in that: The following steps are involved: S1: Estimate the initial value of the charge / discharge test current based on the historical measured data of the lithium-ion battery under test: S11: For the charge / discharge test, based on the historical measured data of the tested lithium-ion battery, a current / rate-internal resistance characteristic diagram of the tested lithium-ion battery at different states of charge, different temperatures and different health states is constructed; S12: fitting a current / rate-internal resistance function relationship according to the current / rate-internal resistance characteristic diagram; S13: combining the voltage estimation formula and the current / rate-internal resistance function relationship, and debugging to obtain the initial value of the charge / discharge test current according to the required cut-off voltage redundancy interval range; S2: performing response voltage determination processing on the initial value of the charge / discharge test current to determine whether the response voltage of the initial value of the charge / discharge test current meets the charge / discharge test requirement; S3: If the charge / discharge test requirements are met, the initial value of the charge / discharge test current is the maximum charge / discharge current value of the lithium-ion battery under test; if the charge / discharge test requirements are not met, the initial value of the charge / discharge test current is iteratively processed to obtain a charge / discharge test current iteration value; the test current iteration value is obtained by the following formula: For the discharge test: ， in, I k ( t ) is the test current iteration value, I k-1 ( t ) is the current value of the last test, t For any moment with the same charge / discharge duration at different current rates, V 01 is the open circuit voltage of the battery before discharge, V k-1 ( t ) is the response voltage of the previous test, V min1 is the discharge cut-off voltage, V max1 is the sum of the discharge cut-off voltage and the redundancy value; For charging test: ， in, I k ( t ) is the test current iteration value, I k-1 ( t ) is the current value of the last test, t For any moment with the same charge / discharge duration at different current rates, V 02 is the open circuit voltage of the battery before charging, V k-1 ( t ) is the response voltage of the previous test, V min2 is the difference between the charging cut-off voltage and the redundancy, V max2 is the charging cut-off voltage; S4: performing response voltage determination processing on the charge / discharge test current iteration value to obtain the maximum charge / discharge current value of the tested lithium-ion battery.

2. A lithium-ion battery peak current estimation and testing method according to claim 1, characterized in that: The historical measured data includes discharge capacity energy test data, rate charge and discharge test data, mixed pulse power characteristic test data, reference performance test data and any data captured and recorded by the system during battery use in actual application scenarios.

3. A lithium-ion battery peak current estimation and testing method according to claim 1, characterized in that: The step S12 specifically includes: Based on the current / rate-internal resistance characteristic diagram obtained from historical data, the least squares method is used to construct t The internal resistance function relationship corresponding to the current of different rates at the moment is: R ( t )= f ( I ( t ))， in, t For any moment with the same charge / discharge duration at different current rates, I ( t )for t The test current at the moment, R ( t )for t The fitted internal resistance value at time, function f It is any one of a linear function, a quadratic function, an exponential function, a power function and a logarithmic function.

4. A lithium-ion battery peak current estimation and testing method according to claim 1, characterized in that: The voltage estimation formula is: V ( t )= V 0- I ( t )* R ( t )， in, V ( t )for t The estimated voltage value at time, V 0 is the battery open circuit voltage, I ( t )for t The test current at the moment, R ( t )for t The fitted internal resistance value at the moment.

5. A lithium-ion battery peak current estimation and testing method according to claim 4, characterized in that: The step S13 specifically includes: combining the voltage estimation formula with the current / rate-internal resistance function relationship to adjust the test current I ( t ),like V ( t ) falls within the required cut-off voltage redundancy range, then I ( t ) is the initial value of the charge / discharge test current under this state of charge, temperature and healthy state.

6. A lithium-ion battery peak current estimation and testing method according to claim 1, characterized in that: The charge / discharge test requirements include: For discharge test: discharge cut-off voltage < response voltage < discharge cut-off voltage + redundancy; For charging test: charging cut-off voltage - redundancy < response voltage < charging cut-off voltage.

7. A lithium-ion battery peak current estimation and testing method according to claim 6, characterized in that: The S4 step includes: S41: performing response voltage determination processing on the charge / discharge test current iteration value to determine whether the response voltage of the charge / discharge test current iteration value meets the charge / discharge test requirement; S42: If the charge / discharge test requirements are met, the charge / discharge test current iteration value is the maximum charge / discharge current value of the lithium-ion battery being tested.

8. A lithium-ion battery peak current estimation and testing method according to claim 7, characterized in that: The S4 step further includes: S42': If the charge / discharge test requirements are not met, return to step S3 according to the response voltage to re-acquire the charge / discharge test current iteration value.

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