Method for determining maximum allowable current of battery during charging / discharging process

Abstract

The present invention relates to a method for determining the maximum allowable current of a battery during the charging process / discharging process, belonging to the technical field of battery testing. The method includes: determining the open-circuit voltage of the battery at different test temperatures and different SOCs during the charging process; for a certain test temperature and a certain SOC, calculating the open-circuit voltage of the battery after pulse charging according to the initial maximum allowable charging current and the set charging duration; calculating the charging current of the battery according to the open-circuit voltage after charging and the charging cut-off voltage, where the charging current is the current when the battery voltage reaches the charging cut-off voltage from the open-circuit voltage corresponding to the SOC 充 ; judging whether the charging current is equal to the initial maximum allowable charging current. If not, adjust the initial maximum allowable charging current until the calculated charging current is equal to the maximum allowable charging current. At this time, the maximum allowable charging current is the maximum allowable current of the battery during the charging process. The present invention greatly shortens the test cycle through calculation means.

Description

Technical Field

[0001] The invention relates to a method for determining a maximum allowable current of a battery during a charging process / discharging process, and belongs to the technical field of battery testing. Background Art

[0002] With the gradual upgrading of green energy and environmental protection concepts, more and more people are beginning to choose electric vehicles as their travel mode, and power lithium-ion battery products have experienced explosive growth in recent years. In order to ensure that the performance of lithium-ion power batteries can meet the daily use needs of customers, various performance tests need to be performed on the power batteries. In order to determine whether the vehicle can meet the requirements of starting, climbing, overtaking and feedback strategies when running at different temperatures and SOCs, it is necessary to perform a test current test on the power battery. The test current test is the maximum current allowed to charge (discharge) for a certain time (t) at a certain SOC and temperature. The test current test during the discharge process is as follows: Figure 1-1 Shown: The instantaneous voltage U at the end of discharge ns With discharge cut-off voltage U 截止 If the difference is within 10mV, the current discharge current is the maximum allowable discharge current at the SOC and temperature. The test current test during the charging process is as follows: Figure 1-2 Shown: voltage U at the moment charging ends ns With charging cut-off voltage U 截止 If the difference is within 10mV, the current charging current is the maximum allowable charging current at this SOC and temperature.

[0003] The existing test current test method steps are as follows:

[0004] 1) Determine whether the test is a charge test current or a discharge test current, determine the SOC point to be tested, usually every 5% SOC, such as (100% SOC, 95% SOC, ..., 10% SOC, 5% SOC), determine the test temperature, usually the test temperature is 25℃, 30℃, 35℃, 45℃, 40℃, 45℃, 50℃, 55℃, 20℃, 15℃, 10℃, 5℃, 0℃ (only test discharge), -5℃ (only test discharge), -10℃ (only test discharge), -15℃ (only test discharge), -20℃ (only test discharge), -25℃ (only test discharge), -30℃ (only test discharge), etc., determine the maximum current and time for the test current test;

[0005] 2) Charge or discharge the battery at a certain temperature and SOC using a current of 0.5C to 1.0C until the battery reaches the specified SOC, and then place it for a long time. The shelf time is generally 3 hours at room temperature, 12 hours at high temperature (>25°C), and 18 hours at low temperature (<25°C) until the voltage stabilizes;

[0006] 3) Pulse charge and discharge the battery at a specified SOC with a set current and for a set duration, and record the instantaneous voltage U when the pulse charge and discharge is completed. ns If ns the difference between U and the charge and discharge cut-off voltage is within 10 mV, the set current is the maximum current. If the condition is not met, try repeatedly. An experienced engineer needs 2 - 3 attempts to test a single SOC point until the requirement is met.

[0007] 4) Adjust the SOC to conduct the trial current test for the next SOC point. After completing the trial current test at one temperature, conduct the trial current test at the next temperature point.

[0008] Problems existing in the existing trial current test method are as follows:

[0009] The test time is long and the equipment occupancy rate is high: The trial current test at room temperature requires at least 60 tests, with a duration of about 1 month. The SOC - DCR test duration at high temperature is about 3 months, and the SOC - DCR test duration at low temperature is about 5 months.

[0010] In summary, the existing test method has a long cycle and a high equipment occupancy rate. Summary of the Invention

[0011] The purpose of this application is to provide a method for determining the maximum allowable current of a battery during the charging process / discharging process to solve the problems of long cycle and high equipment occupancy rate of the existing test methods.

[0012] To achieve the above purpose, this application proposes a technical solution for a method for determining the maximum allowable current of a battery during the charging process, including the following steps:

[0013] 1) Determine the open - circuit voltage of the battery at different test temperatures and different SOCs during the charging process.

[0014] 2) For a certain test temperature and a certain SOC, calculate the charging capacity of the battery after pulse charging according to the initial maximum allowable charging current and the set charging duration, and then calculate the SOC after charging based on this SOC and the charging capacity. 充 ;

[0015] 3) Calculate the charging current of the battery according to the open - circuit voltage corresponding to the SOC 充 and the charging cut - off voltage. The charging current is the current when the battery voltage reaches the charging cut - off voltage from the open - circuit voltage corresponding to the SOC 充 corresponding.

[0016] 4) Determine whether the charging current obtained in step 3) is equal to the initial maximum allowable charging current in step 2). If they are not equal, adjust the initial maximum allowable charging current, and repeat steps 2) to 3) according to the adjusted maximum allowable charging current until the calculated charging current is equal to the maximum allowable charging current. At this time, the maximum allowable charging current is the maximum allowable current of the battery at this test temperature and this SOC during the charging process.

[0017] The beneficial effect of the technical solution of the method for determining the maximum allowable current of the battery during the charging process of the present invention is as follows: Based on obtaining the open-circuit voltages of the battery at different test temperatures and different SOCs during the charging process, the present invention calculates the open-circuit voltage of the battery after pulse charging according to the initial maximum allowable charging current and the set charging duration, calculates the charging current according to the open-circuit voltage after charging and the charging cut-off voltage. When the charging current is not equal to the initial maximum allowable charging current, adjust the initial maximum allowable charging current until the adjusted maximum allowable charging current is equal to the charging current. The adjusted maximum allowable charging current is the maximum allowable current of the battery during the charging process. The present invention greatly shortens the test cycle by means of calculation.

[0018] Further, in order to shorten the test cycle, the steps of determining the open-circuit voltages of the battery at different test temperatures and different SOCs in step 1) include:

[0019] Charge the battery at at least two different charging rates at different test temperatures;

[0020] During the charging process, record the voltages corresponding to different charging rates at the same set SOC;

[0021] Perform linear fitting on different charging rates and their corresponding voltages at the same set SOC, calculate the voltage when the charging rate is zero according to the fitted straight line, and use the voltage when the charging rate is zero as the open-circuit voltage.

[0022] Further, in step 4), the adjustment process of the initial maximum allowable charging current is as follows: If the calculated charging current is greater than the initial maximum allowable charging current, increase the initial maximum allowable charging current; if the calculated charging current is less than the initial maximum allowable charging current, decrease the initial maximum allowable charging current.

[0023] Further, the calculation process of the SOC 充 is as follows: wherein, I max充 is the maximum allowable charging current, t 充 is the set charging duration, and C is the rated capacity of the battery.

[0024] Further, the calculation process of the charging current is as follows:

[0025]

[0026] where I 充 is the charging current, R is the internal resistance of the battery, and OCV ns充 is the open-circuit voltage corresponding to the SOC 充 and U 充截 is the charging cut-off voltage.

[0027] In addition, the present application also proposes a technical solution for determining the maximum allowable current of the battery during the discharging process, including the following steps:

[0028] 1) Determine the open-circuit voltage of the battery at different test temperatures and different SOCs during the discharging process;

[0029] 2) For a certain test temperature and a certain SOC, calculate the discharging capacity of the battery after pulsed discharging according to the initial maximum allowable discharging current and the set discharging duration, and then calculate the SOC after discharging based on this SOC and the discharging capacity 放 ;

[0030] 3) Calculate the discharging current of the battery according to the open-circuit voltage corresponding to the SOC 放 and the discharging cut-off voltage. The discharging current is the current when the battery voltage reaches the discharging cut-off voltage from the open-circuit voltage corresponding to the SOC 放 ;

[0031] 4) Determine whether the discharging current obtained in step 3) is equal to the initial maximum allowable discharging current in step 2). If not, adjust the initial maximum allowable discharging current, and repeat steps 2) to 3) according to the adjusted maximum allowable discharging current until the calculated discharging current is equal to the maximum allowable discharging current. At this time, the maximum allowable discharging current is the maximum allowable current of the battery at this test temperature and this SOC during the discharging process.

[0032] The beneficial effect of the technical solution of the method for determining the maximum allowable current of the battery during the discharging process of the present invention is as follows: Based on obtaining the open-circuit voltage of the battery at different test temperatures and different SOCs during the discharging process, the present invention calculates the open-circuit voltage of the battery after pulsed discharging according to the initial maximum allowable discharging current and the set discharging duration, calculates the discharging current according to the open-circuit voltage after discharging and the discharging cut-off voltage, and adjusts the initial maximum allowable discharging current when the discharging current is not equal to the initial maximum allowable discharging current until the adjusted maximum allowable discharging current is equal to the discharging current. The adjusted maximum allowable discharging current is the maximum allowable current of the battery during the discharging process. The present invention greatly shortens the test cycle through calculation.

[0033] Further, in order to shorten the test cycle, the step of determining the open-circuit voltage of the battery at different test temperatures and different SOCs during the discharge process in step 1) includes:

[0034] Discharge the battery at at least two different discharge rates at different test temperatures;

[0035] During the discharge process, record the voltages corresponding to different discharge rates at the same set SOC;

[0036] Perform linear fitting on different discharge rates and their corresponding voltages at the same set SOC, calculate the voltage when the discharge rate is zero according to the fitted straight line, and use the voltage when the discharge rate is zero as the open-circuit voltage.

[0037] Further, in step 4), the adjustment process of the initial maximum allowable discharge current is as follows: if the calculated discharge current is greater than the initial maximum allowable discharge current, increase the initial maximum allowable discharge current; if the calculated discharge current is less than the initial maximum allowable discharge current, decrease the initial maximum allowable discharge current.

[0038] Further, the calculation process of the SOC 放 is as follows: wherein, I max放 is the maximum allowable discharge current, t 放 is the set discharge duration, and C is the rated capacity of the battery.

[0039] Further, the calculation process of the discharge current is as follows:

[0040]

[0041] wherein, I 放 is the discharge current, R is the internal resistance of the battery, OCV ns放 is the open-circuit voltage corresponding to the SOC 放 and U 放截 is the discharge cut-off voltage. Description of the Drawings

[0042] Figure 1-1 is a schematic diagram of the test current during the discharge process of the prior art;

[0043] Figure 1-2 is a schematic diagram of the test current during the charging process of the prior art;

[0044] Figure 2 is a flowchart of the method for determining the maximum allowable current of the battery during the charging process of the present invention;

[0045] Figure 3It is a flowchart of the method for determining the maximum allowable current of the battery during the discharging process of the present invention. Detailed implementation mode

[0046] Example of the method for determining the maximum allowable current of the battery during the charging process:

[0047] The main concept of the present invention is that after determining the OCV (open circuit voltage) at different test temperatures and different SOCs during the charging process, without conducting actual pulsed charging tests, only calculate the charging capacity through the initial maximum allowable charging current and the set charging duration, and then determine the SOC after charging 充 The corresponding open circuit voltage to simulate the process of the charging test. Finally, obtain the charging current based on the open circuit voltage after charging and the charging cut-off voltage. When the charging current is not equal to the initial maximum allowable charging current, adjust the initial maximum allowable charging current until the adjusted maximum allowable charging current is equal to the charging current. At this time, the maximum allowable charging current is the maximum allowable current of the battery during the charging process. The present invention greatly shortens the test cycle through calculation.

[0048] Specifically, the method for determining the maximum allowable current of the battery during the charging process is as Figure 2 shown, and includes the following steps:

[0049] 1) Determine the OCV of the battery at different test temperatures and different SOCs during the charging process.

[0050] In this step, taking the test temperature of 25°C as an example, the determination process of the OCV at different SOCs is described in detail:

[0051] a. At the test temperature of 25°C, charge the battery with at least two different charging rates (generally, two charging rates are selected as 0.33C and 0.5C, and three charging rates are generally selected as 0.33C, 0.5C, and 0.8C) to increase the SOC of the battery from 0 to 100%. During the charging process, record the voltages corresponding to different charging rates at the same set SOC.

[0052] b. Perform linear fitting on different charging rates and their corresponding voltages at the same set SOC, fit out the straight-line curve of the charging rate and voltage at the same set SOC, calculate the voltage when the charging rate is zero according to the fitted straight line, and use the voltage when the charging rate is zero as the open circuit voltage OCV.

[0053] c. Obtain the open circuit voltages at different SOCs.

[0054] d. Change the test temperature, and repeat steps a, b, and c to obtain the OCV at different test temperatures and different SOCs during the charging process.

[0055] 2) Calculate the charging capacity after the battery is pulse-charged at a certain test temperature and a certain SOC according to the initial maximum allowable charging current and the set charging duration, and then calculate the SOC after charging based on this SOC and the charging capacity. 充 , and determine the SOC 充 corresponding to the OCV ns充 .

[0056] The calculation process of SOC 充 is as follows:

[0057] Among them, I max充 is the maximum allowable charging current, t 充 is the set charging duration, and C is the rated capacity of the battery; here t 充 is generally selected as 60 s; I max充 × t 充 is the charging capacity.

[0058] Here, the method in step 1) is used to determine the OCV 充 corresponding to the SOC ns充 .

[0059] 3) According to the OCV ns充 , the charging cut-off voltage U 充截 , obtain the charging current when the battery voltage reaches the charging cut-off voltage from the OCV ns充 .

[0060] The calculation process of the charging current is as follows:

[0061]

[0062] Among them, I 充 is the charging current, and R is the internal resistance of the battery.

[0063] 4) Judge whether the charging current calculated in step 3) is equal to the initial maximum allowable charging current in step 2). If not, adjust the initial maximum allowable charging current, and repeat steps 2) to 3) according to the adjusted maximum allowable charging current until the calculated charging current is equal to the adjusted maximum allowable charging current. At this time, the adjusted maximum allowable charging current is the maximum allowable current of the battery at this test temperature and this SOC during the charging process.

[0064] In this step, the adjustment process of the initial maximum allowable charging current is as follows: if the calculated charging current is greater than the initial maximum allowable charging current, increase the initial maximum allowable charging current; if the calculated charging current is less than the initial maximum allowable charging current, decrease the initial maximum allowable charging current. As other implementation manners, it is also possible to adjust the magnitude of increasing or decreasing the charging current according to experience in combination with the calculated charging current.

[0065] 5) After calculating for all test temperatures and SOCs, the mapping diagram of the maximum allowable current of the battery during the final charging process is obtained.

[0066] For example: During the charging process, the maximum allowable current of a battery with a rated capacity of 230 Ah at 25°C and 90% SOC is:

[0067] Assume the initial maximum allowable charging current I max充 is 460 A, and the set charging duration is 60 s. Therefore, the charging capacity is 7.667 Ah, and then the SOC 充 = 90% + (7.667 / 230) = 93.33%.

[0068] SOC 充 The corresponding OCV when it is 93.33% ns充 is 3.343 V, U 充截 is 3.65 V, and the internal resistance of the battery is 0.667 mΩ, then we get:

[0069] I 充 = (3650 - 3343) / 0.667 = 460 A.

[0070] It can be seen that I max充 is equal to I 充 Therefore, the maximum allowable current of the battery at 25°C and 90% SOC is 460 A.

[0071] In the above embodiments, in order to improve the test efficiency, the open circuit voltage is obtained by fitting. As other embodiments, the open circuit voltage can also be determined by the test method of long-term shelving.

[0072] Embodiment of the method for determining the maximum allowable current of the battery during the discharging process:

[0073] The main idea of the present invention is that after determining the OCV (open circuit voltage) at different test temperatures and different SOCs during the discharging process, without performing an actual pulsed discharge test, only the discharge capacity is calculated through the initial maximum allowable discharge current and the set discharge duration, and then the SOC after discharge is determined 充 The corresponding open circuit voltage to simulate the process of the discharge test. Finally, the discharge current is obtained based on the open circuit voltage after discharge and the discharge cut-off voltage. When the discharge current is not equal to the initial maximum allowable discharge current, the initial maximum allowable discharge current is adjusted until the adjusted maximum allowable discharge current is equal to the discharge current. At this time, the maximum allowable discharge current is the maximum allowable current of the battery during the discharging process. The present invention greatly shortens the test cycle through calculation.

[0074] Specifically, the method for determining the maximum allowable current of the battery during the discharging process is as follows Figure 3 and includes the following steps:

[0075] 1) Determine the OCV of the battery at different test temperatures and different SOCs during the discharging process.

[0076] In this step, taking the test temperature of 25°C as an example, the determination process of the OCV at different SOCs is described in detail as follows:

[0077] a. At a test temperature of 25°C, discharge the battery at at least two different discharge rates (generally, two discharge rates are selected as 0.33C and 0.5C, and three discharge rates are generally selected as 0.33C, 0.5C, and 0.8C) to increase the SOC of the battery from 0 to 100%. During the discharging process, record the voltages corresponding to different discharge rates at the same set SOC.

[0078] b. Perform linear fitting on the different discharge rates and their corresponding voltages at the same set SOC to fit out the straight-line curve of the discharge rate and voltage at the same set SOC. Calculate the voltage when the discharge rate is zero according to the fitted straight line, and take the voltage when the discharge rate is zero as the open-circuit voltage OCV.

[0079] c. Obtain the open-circuit voltages at different SOCs.

[0080] d. Change the test temperature and repeat steps a, b, and c to obtain the OCVs at different test temperatures and different SOCs during the discharging process.

[0081] 2) Calculate the discharge capacity of the battery after pulsed discharge at a certain temperature and a certain SOC according to the initial maximum allowable discharge current and the set discharge duration, and then calculate the SOC after discharge based on the SOC and the discharge capacity 放 , determine the SOC 放 corresponding OCV ns放 .

[0082] The calculation process of SOC is as follows: 放 where I

[0083] is the maximum allowable discharge current, t max放 is the set discharge duration, and C is the rated capacity of the battery; here t 放 is generally selected as 60s; I 放 ×t max放 is the discharge capacity. 放 is the discharge capacity.

[0084] Here, the method in step 1) is used to determine the OCV 放 corresponding to the SOC ns放 .

[0085] 3) According to the OCV ns放 and the discharge cut-off voltage U 放截 obtain the discharge current when the battery voltage reaches the discharge cut-off voltage from the OCV ns放 .

[0086] The calculation process of the discharge current is as follows:

[0087]

[0088] where I 放 is the discharge current and R is the internal resistance of the battery.

[0089] 4) Determine whether the discharge current calculated in step 3) is equal to the initial maximum allowable discharge current in step 2). If not, adjust the initial maximum allowable discharge current, and repeat steps 2) to 3) according to the adjusted maximum allowable discharge current until the calculated discharge current is equal to the adjusted maximum allowable discharge current. At this time, the maximum allowable discharge current is the maximum allowable current of the battery at this test temperature and this SOC during the discharge process.

[0090] In this step, the adjustment process of the initial maximum allowable discharge current is as follows: if the calculated discharge current is greater than the initial maximum allowable discharge current, increase the initial maximum allowable discharge current; if the calculated discharge current is less than the initial maximum allowable discharge current, decrease the initial maximum allowable discharge current. As other embodiments, the magnitude of the discharge current can also be adjusted to increase or decrease according to experience in combination with the calculated discharge current

[0091] 5) After calculating for all test temperatures and SOCs, obtain the mapping diagram of the maximum allowable current of the battery during the final discharge process.

[0092] For example: during the discharge process, the maximum allowable current of a battery with a rated capacity of 230 Ah at 25°C and 20% SOC is as follows:

[0093] Assume that the initial maximum allowable discharge current I max放 is 345 A, and the set discharge duration is 60 s. Therefore, the discharge capacity is 5.75 Ah, and then the SOC 放 = 20% - (5.75 / 230) = 17.5%.

[0094] The OCV 放 corresponding to the SOC ns放 of 17.5% is 3.083 V, U 放截 is 2.5 V, and the internal resistance of the battery is 1.69 mΩ, and we get:

[0095] I放 =(3083 - 2500) / 1.69 = 345 A.

[0096] It can be seen that I max放 is equal to I 放 . Therefore, the maximum allowable current of the battery at 25 °C and 20% SOC is 345 A.

[0097] In the present invention, the test time for the OCV at all test temperatures is determined to be 20 days (all test temperatures include 10 temperature points in the charging state and 14 temperature points in the discharging state, and about 18 h for one temperature point, so the total test time is 20 days). Then, the maximum current for the allowable charge / discharge setting duration at different test temperatures and different SOCs can be obtained through calculation. Finally, the range between the calculated result and the actually measured result is less than 5%. Moreover, the mapping diagram calculated using the method of the invention can be shortened from the original 9 months to 20 days, greatly improving the test efficiency, reducing the test cost, and decreasing the installation investment of equipment. The method of the present invention is applicable to all lithium-ion batteries, and the material types include ternary batteries, lithium iron phosphate batteries, and lithium cobalt oxide batteries. The battery types include soft-pack batteries, aluminum-shell batteries, cylindrical batteries, etc.

Claims

1. A method for determining the maximum allowable current of a battery during charging, characterized in that, it includes the following steps: 1) Determine the open-circuit voltage of the battery at different test temperatures and different SOCs during charging; 2) For a certain test temperature and a certain SOC, calculate the charging capacity of the battery after pulse charging according to the initial maximum allowable charging current and the set charging duration, and then calculate the SOC after charging based on this SOC and the charging capacity 充 ; 3) According to the SOC 充 The charging current of the battery is calculated based on the corresponding open-circuit voltage and the charging cut-off voltage. The charging current is the current when the battery voltage reaches the charging cut-off voltage starting from the open-circuit voltage corresponding to the SOC 充 ; 4) Determine whether the charging current obtained in step 3) is equal to the initial maximum allowable charging current in step 2). If not, adjust the initial maximum allowable charging current, and repeat steps 2) to 3) according to the adjusted maximum allowable charging current until the calculated charging current is equal to the maximum allowable charging current. At this time, the maximum allowable charging current is the maximum allowable current of the battery at this test temperature and this SOC during charging.

2. The method for determining the maximum allowable current of a battery during charging according to claim 1, characterized in that, the step of determining the open-circuit voltage of the battery at different test temperatures and different SOCs during charging in step 1) includes: Charge the battery at at least two different charging rates at different test temperatures; During the charging process, record the voltages corresponding to different charging rates at the same set SOC; Perform linear fitting on different charging rates and their corresponding voltages at the same set SOC, calculate the voltage when the charging rate is zero according to the fitted straight line, and use the voltage when the charging rate is zero as the open-circuit voltage.

3. The method for determining the maximum allowable current of a battery during charging according to claim 1 or 2, characterized in that, in step 4), the adjustment process of the initial maximum allowable charging current is: if the calculated charging current is greater than the initial maximum allowable charging current, increase the initial maximum allowable charging current; if the calculated charging current is less than the initial maximum allowable charging current, decrease the initial maximum allowable charging current.

4. The method for determining the maximum allowable current of a battery during charging according to claim 1 or 2, characterized in that, The SOC 充 has a calculation process as follows: where I max充 is the maximum allowable charging current, t 充 is the set charging duration, and C is the rated capacity of the battery.

5. The method for determining the maximum allowable current of a battery during charging according to claim 1 or 2, characterized in that, the calculation process of the charging current is: Among them, I 充 is the charging current, R is the internal resistance of the battery, and OCV ns充 is the open-circuit voltage corresponding to SOC 充 , and U 充截 is the charging cut-off voltage.

6. A method for determining the maximum allowable current of a battery during discharging, characterized in that, it includes the following steps: 1) Determine the open-circuit voltage of the battery at different test temperatures and different SOCs during discharging; 2) For a certain test temperature and a certain SOC, calculate the discharge capacity of the battery after pulsed discharge according to the initial maximum allowable discharge current and the set discharge duration, and then calculate the SOC after discharge based on this SOC and the discharge capacity 放 ; 3) According to the SOC 放 Calculate the discharge current of the battery based on the corresponding open-circuit voltage and discharge cut-off voltage. The discharge current is the current when the battery voltage reaches the discharge cut-off voltage starting from the open-circuit voltage corresponding to the SOC 放 ; 4) Determine whether the discharging current obtained in step 3) is equal to the initial maximum allowable discharging current in step 2). If not, adjust the initial maximum allowable discharging current, and repeat steps 2) to 3) according to the adjusted maximum allowable discharging current until the calculated discharging current is equal to the maximum allowable discharging current. At this time, the maximum allowable discharging current is the maximum allowable current of the battery at this test temperature and this SOC during discharging.

7. The method for determining the maximum allowable current of a battery during discharging according to claim 6, characterized in that, the step of determining the open-circuit voltage of the battery at different test temperatures and different SOCs during discharging in step 1) includes: Discharge the battery at at least two different discharging rates at different test temperatures; During the discharging process, record the voltages corresponding to different discharging rates at the same set SOC; Perform linear fitting on different discharging rates and their corresponding voltages at the same set SOC, calculate the voltage when the discharging rate is zero according to the fitted straight line, and use the voltage when the discharging rate is zero as the open circuit voltage.

8. The method for determining the maximum allowable current of the battery during the discharging process according to claim 6 or 7, characterized in that, in the step 4), the adjustment process of the initial maximum allowable discharging current is as follows: if the calculated discharging current is greater than the initial maximum allowable discharging current, increase the initial maximum allowable discharging current; if the calculated discharging current is less than the initial maximum allowable discharging current, decrease the initial maximum allowable discharging current.

9. The method for determining the maximum allowable current of the battery during the discharging process according to claim 6 or 7, characterized in that, The SOC 放 has a calculation process as follows: where I max放 is the maximum allowable discharge current, t 放 is the set discharge duration, and C is the rated capacity of the battery.

10. The method for determining the maximum allowable current of the battery during the discharging process according to claim 6 or 7, characterized in that, the calculation process of the discharging current is as follows: Where, I 放 is the discharge current, R is the internal resistance of the battery, OCV ns放 is the open circuit voltage corresponding to SOC 放 , and U 放截 is the discharge cut-off voltage.

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