Method and device for determining power battery capacity evaluation parameters and medium

Abstract

The invention provides a power battery capacity evaluation parameter determination method and device and a medium, and the method comprises the steps: obtaining first test data of a power battery, the first test data comprising accumulated charging energy of the power battery at each charging moment in a first charging test, and accumulated discharging energy of the power battery at each discharging moment in a first discharging test; determining a corresponding first charging moment when the state of charge of the power battery is a first preset state of charge and a corresponding second charging moment when the state of charge of the power battery is a second preset state of charge in the first charging test; determining an accumulated charging coulomb of the power battery in a time period from the first charging moment to the second charging moment; determining a corresponding target discharge moment when the accumulated discharge coulomb of the power battery is equal to the accumulated charge coulomb in the first discharge test; and dividing the target accumulated discharge energy by the difference between the second accumulated charge energy and the first accumulated charge energy to obtain energy efficiency. According to the technical scheme, the accuracy of power battery capacity evaluation can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power batteries, in particular to a method and device for determining a power battery capacity evaluation parameter and a medium. BACKGROUND

[0002] A power battery is the power source of an electric vehicle. Before the power battery is installed in the vehicle, the capacity of the power battery needs to be evaluated. Precise evaluation of the capacity of the power battery has an important influence on the vehicle's cruising range, battery life, and maintenance cost, and is a key link for ensuring the performance of the vehicle. For example, precise evaluation of the capacity of the power battery can ensure the accuracy of the estimated cruising range, help to monitor the state of the battery in real time, optimize the charging and discharging strategy, prolong the cycle life of the battery, ensure stable power output of the power battery under different working conditions, ensure the power performance of the vehicle, and improve the driving smoothness and response speed. Therefore, how to provide a method for improving the precision of the evaluation of the capacity of the power battery is a technical problem to be solved. SUMMARY

[0003] Embodiments of the present application provide a method and device for determining a power battery capacity evaluation parameter and a medium. The technical solutions provided in the present application can improve the precision of the evaluation of the capacity of the power battery.

[0004] Other characteristics and advantages of the present application will become apparent from the following detailed description, or will be learned by practice of the present application.

[0005] According to a first aspect of the embodiments of the present application, a method for determining a capacity evaluation parameter of a power battery is provided. The capacity evaluation parameter includes energy efficiency. The method comprises: obtaining first test data of the power battery, the first test data being obtained by sequentially performing a first charging test and a first discharging test on the power battery at a first set temperature, the first test data including accumulated charging energy of the power battery at each charging time in the first charging test and accumulated discharging energy of the power battery at each discharging time in the first discharging test; determining, based on the first test data, a first charging time corresponding to a first preset state of charge of the power battery in the first charging test and a second charging time corresponding to a second preset state of charge of the power battery, the second preset state of charge being greater than the first preset state of charge; determining, based on the first test data, accumulated charging coulomb of the power battery in a time period from the first charging time to the second charging time; determining, based on the first test data, a target discharging time corresponding to a case that accumulated discharging coulomb of the power battery is equal to the accumulated charging coulomb in the first discharging test; and obtaining the energy efficiency by dividing target accumulated discharging energy by a difference between second accumulated charging energy and first accumulated charging energy, the target accumulated discharging energy being the accumulated discharging energy corresponding to the target discharging time in the first test data, the first accumulated charging energy being the accumulated charging energy corresponding to the first charging time in the first test data, and the second accumulated charging energy being the accumulated charging energy corresponding to the second charging time in the first test data.

[0006] In some embodiments of the present application, based on the foregoing scheme, determining, based on the first test data, the first charging time corresponding to the first preset state of charge of the power battery in the first charging test comprises: obtaining a nominal capacity of the power battery; and determining, based on the nominal capacity and the first test data, the first charging time.

[0007] In some embodiments of the present application, based on the foregoing scheme, the first test data further includes charging current of the power battery at each charging time in the first charging test, and determining, based on the nominal capacity and the first test data, the first charging time comprises: calculating the first charging time by the following formula:

[0008]

[0009] wherein, SOC1 represents the first preset state of charge, i(t) represents the charging current, t0 represents a charging start time of the first charging test, t1 represents the first charging time, and Q represents the nominal capacity.

[0010] In some embodiments of the present application, based on the foregoing scheme, the first test data further comprises accumulated charge capacity of the power battery at each charging time in the first charging test, and the first charging time is determined based on the nominal capacity and the first test data, including: calculating the product of the first preset state of charge and the nominal capacity as a target accumulated charge capacity; determining the charging time corresponding to the target accumulated charge capacity from the first test data as the first charging time.

[0011] In some embodiments of the present application, based on the foregoing scheme, the first test data further comprises charging current of the power battery at each charging time in the first charging test, and the accumulated charge coulomb of the power battery in the time period from the first charging time to the second charging time is determined based on the first test data, including: summing the charging current of the power battery at each charging time between the first charging time and the second charging time as the accumulated charge coulomb.

[0012] In some embodiments of the present application, based on the foregoing scheme, the first charging test is performed according to the charging performance parameter table of the power battery, and the charging performance parameter table records the correspondence among the state of charge, the temperature and the charging rate, the first discharging test is performed according to the first discharging rate, or the first charging test is performed according to the set charging rate, and the first discharging test is performed according to the second discharging rate.

[0013] In some embodiments of the present application, based on the foregoing scheme, the capacity evaluation parameter further comprises a mean value of discharging capacity and a mean value of discharging energy, and the method further comprises: obtaining second test data, the second test data being obtained by performing multiple charging and discharging tests on the power battery, the charging and discharging test comprising a second charging test and a second discharging test performed in sequence, and the second test data comprising a first accumulated discharging capacity and a first accumulated discharging energy of the power battery at the end of the second discharging test; calculating the average value of each first accumulated discharging capacity corresponding to each charging and discharging test to obtain the mean value of discharging capacity; and calculating the average value of each first accumulated discharging energy corresponding to each charging and discharging test to obtain the mean value of discharging energy.

[0014] In some embodiments of the present application, based on the foregoing scheme, the capacity evaluation parameter further includes a capacity retention rate and an energy retention rate, and the method further includes: obtaining third test data, the third test data being obtained by sequentially performing a third charge test and a third discharge test on the power battery; the third charge test being performed at a first set temperature, and the third discharge test being performed at a second set temperature, the second set temperature being greater than or less than the first set temperature; the third test data including a second cumulative discharge capacity and a second cumulative discharge energy of the power battery at an end time of the third discharge test; obtaining fourth test data, the fourth test data being obtained by sequentially performing a fourth charge test and a fourth discharge test on the power battery at the first set temperature, the fourth test data including a third cumulative discharge capacity and a third cumulative discharge energy of the power battery at an end time of the fourth discharge test; calculating a ratio of the second cumulative discharge capacity to the third cumulative discharge capacity to obtain the capacity retention rate; and calculating a ratio of the second cumulative discharge energy to the third cumulative discharge energy to obtain the energy retention rate.

[0015] According to a second aspect of the embodiments of the present application, a device for determining a capacity evaluation parameter of a power battery is provided, the capacity evaluation parameter including an energy efficiency, and the device includes: an obtaining unit, configured to obtain first test data of the power battery, the first test data being obtained by sequentially performing a first charge test and a first discharge test on the power battery at a first set temperature, the first test data including cumulative charge energy of the power battery at each charge time in the first charge test and cumulative discharge energy of the power battery at each discharge time in the first discharge test; a first determining unit, configured to determine, based on the first test data, a first charge time corresponding to a first preset state of charge of the power battery in the first charge test and a second charge time corresponding to a second preset state of charge of the power battery, the second preset state of charge being greater than the first state of charge; a second determining unit, configured to determine, based on the first test data, cumulative charge coulombs of the power battery in a time period from the first charge time to the second charge time; a third determining unit, configured to determine, based on the first test data, a target discharge time corresponding to a condition that cumulative discharge coulombs of the power battery are equal to the cumulative charge coulombs in the first discharge test; and a fourth determining unit, configured to divide a target cumulative discharge energy by a difference between second cumulative charge energy and first cumulative charge energy to obtain the energy efficiency, the target cumulative discharge energy being the cumulative discharge energy corresponding to the target discharge time in the first test data, the first cumulative charge energy being the cumulative charge energy corresponding to the first charge time in the first test data, and the second cumulative charge energy being the cumulative charge energy corresponding to the second charge time in the first test data.

[0016] According to a third aspect of the embodiments of the present application, a computer readable storage medium is provided. The computer readable storage medium stores at least one program code. The at least one program code is loaded and executed by a processor to implement the operations performed by the method according to any one of the first aspect.

[0017] In a conventional process of determining the energy efficiency of a power battery, the energy efficiency is usually calculated directly by Ah integration of a power battery charging and discharging device. However, the Ah integration is affected by factors such as power battery internal resistance heat loss, power battery charging and discharging device conversion efficiency error, cumulative integration error, etc., resulting in errors in the obtained energy efficiency, and ultimately leading to inaccurate evaluation of the capacity of the power battery. However, based on the technical solutions of the present application, the number of actual transferred electrons is directly measured by Coulomb (charge quantity), avoiding the interference of energy loss and measurement error, making the calculation of energy efficiency (especially the charging electric efficiency in a specific SOC interval, i.e., the SOC interval from the first preset state of charge to the second preset state of charge) closer to the actual electrochemical reaction quantity, and significantly improving the accuracy of the determined energy efficiency. Finally, based on the energy efficiency, the capacity of the power battery is evaluated, which can improve the accuracy of the evaluation of the capacity of the power battery.

[0018] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and are not limiting to the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. It is clear that the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings. In the drawings:

[0020] Figure 1 Fig. 1 shows an architectural schematic diagram of a test system of a power battery according to an embodiment of the present application;

[0021] Figure 2 Fig. 2 shows a first flow schematic diagram of a method for determining a capacity evaluation parameter of a power battery according to an embodiment of the present application;

[0022] Figure 3 Fig. 3 shows a detailed flow schematic diagram of determining a first charging time corresponding to a first preset state of charge of a power battery in a first charging test based on first test data according to an embodiment of the present application;

[0023] Figure 4Fig. 2 shows a second flowchart illustrating a method for determining a power battery capacity evaluation parameter according to an embodiment of the present application;

[0024] Figure 5 Fig. 3 shows a third flowchart illustrating a method for determining a power battery capacity evaluation parameter according to an embodiment of the present application;

[0025] Figure 6 Fig. 4 shows a block diagram of a device for determining a power battery capacity evaluation parameter according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the implementations set forth in this disclosure; rather, these implementations are provided so that this disclosure will be thorough and complete, and fully convey the scope of example implementations to those skilled in the art. Like reference numerals may refer to like elements throughout.

[0027] Moreover, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the application. One skilled in the relevant art will recognize, however, that the

[0028] The block diagrams in the drawings show only the functionality of the features and can not imply a physical or architectural arrangement of the features. That is, the functionality can be implemented in software, hardware, or a combination thereof. The functionality can be implemented in one or more modules or components, which can collect data and / or perform one or more operations.

[0029] The flow diagrams depicted herein are merely illustrative examples, which can or can not be executed in the order as shown. That is, various steps can be executed in an order different than that shown or can be executed concurrently. Further, some operations can be combined or omitted.

[0030] It should be noted that the term "a plurality of" means two or more. The term "and / or" describes associative relationship of associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally means that the associated objects before and after are in an "or" relationship.

[0031] It should be noted that the terms "first", "second", and the like in the description and claims of the application and above figures are used for distinguishing between similar objects and not necessarily for describing a specific sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of orderly execution or performance under other sequences than those illustrated or otherwise described herein.

[0032] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0033] It should be noted that the technical solutions of the present application are used to determine the capacity evaluation parameters of the power battery, wherein the capacity evaluation parameters include the energy efficiency, and can also include one or more of the discharge capacity average, the discharge energy average, the capacity retention rate, and the energy retention rate.

[0034] It should also be noted that the capacity retention rate can include the low-temperature capacity retention rate and the high-temperature capacity retention rate, and the energy retention rate can include the low-temperature energy retention rate and the high-temperature energy retention rate.

[0035] The technical solutions of the present application are applied before the power battery is loaded into a vehicle, in order to determine the capacity evaluation parameters of the power battery, the power battery needs to be tested in advance to obtain the first test data required to determine the energy efficiency, the second test data required to determine the discharge capacity average and the discharge energy average, and the third test data and the fourth test data required to determine the capacity retention rate and the energy retention rate.

[0036] In the present application, the specific implementation of testing the power battery is not limited, and can be designed according to actual conditions. The following will be described in combination with Figure 1 An exemplary preferred embodiment is shown.

[0037] Referring to Figure 1 , a schematic diagram of the architecture of a test system for a power battery according to an embodiment of the present application is shown.

[0038] The test system for the power battery includes a variable temperature box 10, the power battery 11 is placed in the variable temperature box, and a battery management system (BMS) 12, the test system further includes a power battery charging and discharging device 20, wherein the power battery 11 and the power battery charging and discharging device 20 are connected through a CAN bus, and the power battery 11 and the battery management system 12 are connected through a CAN bus.

[0039] The power battery 11 comprises a plurality of battery monomers.

[0040] In the test system, the variable temperature box 10 can be adjusted according to different requirements, and can be set to a constant temperature mode or a temperature dynamic cycle mode to meet the temperature requirements in the test of the power battery.

[0041] In the test system, the power battery charging and discharging device 20 is used for charging test and discharging test of the power battery, and records the performance data of the power battery 11 in the test process, including but not limited to the charging time, the discharging time, the charging current at different charging time in the charging test, the cumulative charging capacity (i.e. charging ampere-hour), the cumulative charging energy (i.e. charging watt-hour), the discharging current at different discharging time in the discharging test, the cumulative discharging capacity, the cumulative discharging energy, etc.

[0042] In the test system, the power battery management system 12 is used for obtaining the state of charge of the power battery 11, the state of charge of the battery monomer, the highest voltage of the battery monomer, the lowest voltage of the battery monomer, the highest temperature and the lowest temperature of the battery monomer, etc. at different time in the charging test and the discharging test.

[0043] It can be understood that the power battery management system 12 realizes online monitoring of the state of the power battery 11, including SOC estimation, state analysis and implementation of necessary thermal management, etc., to ensure safe operation of the power battery 11 and prolong the cycle life of the power battery 11. It can analyze whether the SOC is too high, whether the temperature of the power battery is too high / low, whether the voltage of the battery monomer is too high / low, whether the temperature rise of the power battery 11 is too fast, whether the insulation is faulty, whether there is communication failure, etc. For example, the end voltage of each battery monomer in the power battery 11 can be collected and monitored in real time to prevent overcharging or overdischarging of the power battery 11.

[0044] It should be noted that in the test, the time interval for collecting and recording data of the power battery by the power battery charging and discharging device 20 and the power battery management system 12 can be 1s.

[0045] After setting up the test system of the power battery, the power battery can be tested according to the following steps 1 to 17:

[0046] Step 1, test preparation, in which the temperature of the variable temperature box is adjusted to a specific temperature T1, the power battery is discharged by using a standard discharging method, and the power battery is fully rested after the discharging is completed.

[0047] It should be noted that the purpose of fully resting the power battery after the end of discharging is to eliminate the polarization of the electrode and to adapt the temperature of the power battery to the temperature difference ΔT of the variable temperature box, because the temperature is an important factor affecting the discharge capacity of the power battery.

[0048] In the embodiment, the specific temperature T1 can be set to 20℃≤T1≤25℃, and the temperature difference ΔT can be set to ΔT≤2℃. Preferably, the specific temperature T1 is set to 25℃, and the temperature difference ΔT is set to 2℃. The time requirement for fully resting the power battery is ≥30min to ensure that the temperature difference ΔT meets the requirement, and the specific adjustment can be made according to the actual situation, which is not limited in the application.

[0049] It should be further noted that the standard discharge refers to constant current discharge at 1 / 3C (i.e. discharge rate is 1 / 3 rate, and the size of the discharge current is 1 / 3 of the rated capacity of the battery) to the voltage of any one battery monomer in the power battery being lower than the voltage lower limit V Limit- (Example, 2.5V) in the environment of the temperature of the variable temperature box being the specific temperature T1, wherein the voltage lower limit V Limit- is provided by the cell supplier, and the specific adjustment can be made according to the actual situation, which is not limited in the application.

[0050] Step 2, maintain the temperature of the variable temperature box as the specific temperature T1, and charge the power battery in the standard charging mode, and fully rest the power battery after charging.

[0051] It should be noted that the standard charging is to achieve full charging by using the step constant current charging method, and the specific method is as follows: in the T1 environment, constant current charging is performed by using I1 until the voltage of any one battery monomer in the power battery reaches the voltage upper limit V Limit+ , and then resting for 5min, and then constant current discharge (I2, I3, I4, I5, I6, I7) charging, in which each current is charged to the voltage of the battery monomer reaching the voltage upper limit V Limit+ , and then reduced to the next lower current until the charging cut-off voltage is reached, the standard charging is ended, and fully resting for 30min.

[0052] In the embodiment, the voltage upper limit V Limit+ can be set to 3.65V, which is provided by the cell supplier, and the specific adjustment can be made according to the actual situation, which is not limited in the application.

[0053] In the embodiment, I1>I2>I3>I4>I5>I6>I7, preferably, I1=I1 / 3(A)=1 / 3C, indicating that the charging rate is 1 / 3 rate, that is, the size of the charging current is 1 / 3 of the rated capacity of the battery. Generally, the charging rate <1 / 3C is low rate, 1 / 3C-3C is medium rate, and >3C is high rate. The charging condition of low rate and small current is selected, the polarization of the electrode is small, the active material can be fully utilized, which is beneficial to the complete release of the battery capacity in the discharge process, and is beneficial to the use safety and cycle life of the power battery.

[0054] For example, I1=I1 / 3(A)=1 / 3C, I2=I1 / 6(A)=1 / 6C, I3=I1 / 10=1 / 10C, I4=I1 / 15(A)=1 / 15C, I5=I1 / 20(A)=1 / 20C, I5=I1 / 25(A)=1 / 25C, I7=I1 / 30(A)=1 / 30C. The charging condition of stepwise and low rate and small current is selected, which weakens the polarization of the battery including concentration difference polarization, electrochemical polarization, ohmic polarization, reduces the internal resistance of the battery, ensures that the active material can be fully utilized, ensures that the battery reaches the full charge state, and can prevent overcharging of the battery, balances the charging of the battery monomer in the power battery, and makes each battery monomer in the power battery reach a balanced and consistent state, ensures the consistency of the power battery, and ensures the safety performance and cycle life of the power battery.

[0055] It should be noted that in the standard charging process, the actual situation of the power battery needs to be considered, and too small charging current may not be able to charge the power battery, so the charging rate needs to be reasonably set, and the specific value of the set charging rate is not limited in the present application; in addition, the time cost needs to be considered comprehensively, and the number of stepwise small currents needs to be reasonably selected, for example, I1-I7 are a total of 7, and other numbers can also be set, which are not limited in the present application.

[0056] Step 3, in the environment where the temperature of the variable temperature box is kept at a specific temperature T1, a specific discharge rate C1 is used for constant current discharge until the voltage of any battery monomer in the power battery is lower than V Limit- (For example, 2.5V), then the discharge is stopped, and sufficient standing is performed after the discharge is stopped. The specific discharge rate C1 can be set to 1 / 3C.

[0057] Step 4, the above steps 2 and 3 are repeated multiple times, specifically, 2-3 times, preferably, the number of times of repeating the above steps 2 and 3 is 3.

[0058] Step 5, the temperature of the variable temperature box is maintained at a specific temperature T1, and the power battery is charged in a standard charging manner, and after the power battery is charged, the power battery is sufficiently stood.

[0059] It can be understood that step 5 is consistent with step 2 described above.

[0060] Step 6, in the environment where the temperature of the variable temperature box is maintained at a specific temperature T1, constant current discharge is performed at a specific discharge rate C2 until the voltage of any single cell in the power battery is lower than V Limit- (Exemplarily, 2.5V), then the discharge is stopped, and sufficient standing is performed after the discharge is stopped. The specific discharge rate C2 can be set to 1C.

[0061] Step 7, steps 5 and 6 described above are repeated for multiple times, specifically, 2-3 times, preferably, the number of times of repeating steps 5 and 6 described above is 3.

[0062] It can be understood that, compared with steps 2, 3, 4 and steps 5, 6, 7 described above, only the discharge rate in the discharge process is changed. The discharge rate adopted in steps 2, 3, 4 is a specific discharge rate C1, and the discharge rate adopted in steps 5, 6, 7 is a specific discharge rate C2.

[0063] Step 8, after the power battery is sufficiently stood in the environment where the temperature of the variable temperature box is the specific temperature T1, the power battery is charged according to the charging performance parameter table of the power battery, and the charging is stopped when the voltage of any single cell in the power battery reaches the voltage upper limit V Limit+ , and sufficient standing is performed after the charging is stopped.

[0064] The charging performance parameter table records the corresponding relationship among the state of charge, the temperature and the charge rate, and the charging performance parameter table is provided by the cell manufacturer.

[0065] Step 9, in the environment where the temperature of the variable temperature box is maintained at the specific temperature T1, constant current discharge is performed at a specific discharge rate C2 until the voltage of any single cell in the power battery is lower than V Limit- , then the discharge is stopped, and sufficient standing is performed after the discharge is stopped.

[0066] Step 10, in the environment where the temperature of the variable temperature box is the specific temperature T1, charging is performed at a specific charge rate C3 until the voltage of any single cell in the power battery reaches the voltage upper limit V Limit+ , then the charging is stopped, and sufficient standing is performed after the charging is stopped. The specific charge rate C3 can be set to 1C.

[0067] Step 11, in the environment where the temperature of the variable temperature box is the specific temperature T1, constant current discharge is performed at a specific discharge rate C1 until the voltage of any single cell in the power battery is lower than V Limit-When the voltage of any one battery cell in the power battery is lower than V

[0068] Step 12, charge the power battery in the environment where the temperature of the variable temperature box is a specific temperature T1 by using the standard charging mode, and perform sufficient standing after the charging is completed.

[0069] Step 13, adjust the temperature of the variable temperature box to a specific temperature T2, and perform sufficient standing on the power battery, so that the temperature of the power battery is different from the temperature of the variable temperature box by ΔT. Wherein, T2 can be set to 35℃≤T2≤40℃, preferably, T2 is set to 35℃.

[0070] Step 14, in the environment where the temperature of the variable temperature box is a specific temperature T2, constant current discharge to the voltage of any one battery cell in the power battery is lower than V Limit- when the voltage of any one battery cell in the power battery is lower than V

[0071] Step 15, after the power battery is sufficiently stood in the environment where the temperature of the variable temperature box is a specific temperature T1, charge the power battery by using the standard charging mode, and perform standing for 30 minutes after the charging is completed.

[0072] Step 16, adjust the temperature of the variable temperature box to a specific temperature T3, and perform sufficient standing on the power battery, so that the temperature of the power battery is different from the temperature of the variable temperature box by ΔT, preferably, T3 can be set to -5℃≤T3≤0℃, preferably, T3 is set to 0℃.

[0073] Step 17, in the environment where the temperature of the variable temperature box is a specific temperature T3, constant current discharge to the voltage of any one battery cell in the power battery is lower than V Limit- when the voltage of any one battery cell in the power battery is lower than V

[0074] The above is a preferred way of testing the power battery. It can be understood that during the testing process, the power battery charging and discharging equipment and the power battery management system can record and collect the charging current, the discharging current, the cumulative charging capacity, the cumulative discharging capacity, the cumulative charging energy, the cumulative discharging energy, the voltage of the battery cell, and the like in real time.

[0075] It can be understood that the charging rate used in different charging tests is different in the above test process, and the discharging rate used in different discharging tests is different. Specifically, it can be summarized as shown in Table 1.

[0076]

[0077]

[0078] Table 1

[0079] It should be noted that the power battery can be tested according to the order of steps 1 to 17 above to obtain the data required to determine the capacity evaluation parameters of the power battery, or only a plurality of steps in steps 1 to 17 above can be selected to test the power battery to obtain the data required to determine the capacity evaluation parameters of the power battery. Before any one-time charge and discharge test, the test preparation step shown in step 1 needs to be performed. For example, if the capacity evaluation parameters only include the energy efficiency in a specific SOC interval, only steps 1, 8, and 9 above can be selected to test the power battery to obtain the data required to determine the energy efficiency. If the capacity evaluation parameters include the energy efficiency in a specific SOC interval, and include the high-temperature capacity retention rate and the high-temperature energy retention rate, only steps 1, 8, 9, 12, 13, and 14 above can be selected to test the power battery.

[0080] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The following examples and features in the examples can be combined with each other without conflict.

[0081] Referring to Figure 1 , a first flowchart of a method for determining the capacity evaluation parameters of a power battery according to an embodiment of the present application is shown, in which the capacity evaluation parameters include the energy efficiency, and specifically include the following steps 110 to 150:

[0082] Step 110, obtaining first test data of the power battery, the first test data being obtained by sequentially performing a first charge test and a first discharge test on the power battery at a first set temperature, the first test data including the cumulative charge energy of the power battery at each charge time in the first charge test, and the cumulative discharge energy of the power battery at each discharge time in the first discharge test.

[0083] In an embodiment, the first charge test is performed according to the charge performance parameter table of the power battery, and the charge performance parameter table records the correspondence among the state of charge, the temperature, and the charge rate, and the first discharge test is performed according to the first discharge rate.

[0084] In which, the first charge test can be step 8 of the present application, and the specific first charge test method is: in an environment where the temperature of the variable temperature box is a specific temperature T1, the power battery is charged according to the charge performance parameter table of the power battery, and the charging is stopped when the voltage of any one battery cell in the power battery reaches the voltage upper limit V Limit+ , and a sufficient standing is performed after the charging is stopped.

[0085] The first discharge test can be the step 11 of the above application, and the specific first discharge test method is: in the environment of the temperature of the variable temperature box being a specific temperature T1, adopting a specific discharge rate C1 to perform constant current discharge until the voltage of any battery cell in the power battery is lower than V Limit- , stopping the discharge, and performing sufficient standing after stopping the discharge. The specific discharge rate C1 is the second discharge rate, which is 1 / 3C.

[0086] It should be noted that the power battery can be tested according to the above steps 1 to 17 in sequence, so that the data generated in steps 8 and 9 in steps 1 to 17 is taken as the first test data. Alternatively, after obtaining the power battery, the power battery is first tested according to the above step 1, and after the above step 1 is performed, the above steps 8 and 9 are directly performed to obtain the first test data.

[0087] In another embodiment, the first charge test is charging the power battery according to a set charge rate, and the first discharge test is discharging the power battery according to a second discharge rate.

[0088] The first charge test can be the step 10 of the above application, and the specific first charge test method is: in the environment of the temperature of the variable temperature box being a specific temperature T1, adopting a specific charge rate C3 to charge until the voltage of any battery cell in the power battery reaches the voltage upper limit V Limit+ , stopping the charge, and performing sufficient standing after stopping the charge. The specific charge rate C3 is the set charge rate, which is 1C.

[0089] The first discharge test can be the step 11 of the above application, and the specific first discharge test method is: in the environment of the temperature of the variable temperature box being a specific temperature T1, adopting a specific discharge rate C1 to perform constant current discharge until the voltage of any battery cell in the power battery is lower than V Limit- , stopping the discharge, and performing sufficient standing after stopping the discharge. The specific discharge rate C1 is the second discharge rate, which is 1 / 3C.

[0090] It should be noted that the power battery can be tested according to the above steps 1 to 17 in sequence, so that the data generated in steps 10 and 11 in steps 1 to 17 is taken as the first test data. Alternatively, after obtaining the power battery, the power battery is first tested according to the above step 1, and after the above step 1 is performed, the above steps 10 and 11 are directly performed to obtain the first test data.

[0091] Continuing to refer to Figure 2determining, based on the first test data, a first charging time corresponding to the first preset state of charge and a second charging time corresponding to a second preset state of charge in the first charging test, the second preset state of charge being greater than the first state of charge.

[0092] The first preset state of charge can be set as 10%≤SOC≤20%, preferably 12%, and the second preset state of charge can be set as 80%≤SOC≤100%, preferably 100%.

[0093] In some embodiments, the first charging time corresponding to the first preset state of charge and the second charging time corresponding to the second preset state of charge in the first charging test can be determined according to the state of charge of the power battery recorded in the power battery management system.

[0094] In another embodiment, the first charging time can be determined according to the steps shown in Figure 3

[0095] Referring to Figure 3 , a detailed flowchart of determining the first charging time corresponding to the first preset state of charge in the first charging test based on the first test data according to an embodiment of the present application is shown, which specifically includes the following steps 121 to 122.

[0096] Step 121: obtaining the nominal capacity of the power battery.

[0097] Step 122: determining the first charging time based on the nominal capacity and the first test data.

[0098] In the present embodiment, the nominal capacity of the battery is provided by the cell manufacturer.

[0099] In step 122, the specific embodiments of determining the first charging time based on the nominal capacity and the first test data include at least the following two kinds.

[0100] The first embodiment of step 122, in which the first test data further includes the charging current of the power battery at each charging time in the first charging test, the first charging time is calculated by the following formula 1:

[0101]

[0102] wherein SOC1 represents the first preset state of charge, i(t) represents the charging current, t0 represents the charging start time of the first charging test, t1 represents the first charging time, and Q represents the nominal capacity. ​

[0103] It can be understood that the first preset state of charge is known data, the charging current at each charging time in the first charging test is known data, and the nominal capacity is known data, and thus the first charging time t1 corresponding to the state of charge of the power battery being the first preset state of charge in the first charging test can be calculated by the above formula 1.

[0104] In a second implementation of step 122, in the second implementation, the first test data further includes the cumulative charging capacity of the power battery at each charging time in the first charging test, and the first charging time can be obtained according to steps 1221 to 1222 as follows.

[0105] In step 1221, the product of the first preset state of charge and the nominal capacity is calculated as a target cumulative charging capacity.

[0106] In step 1222, the charging time corresponding to the target cumulative charging capacity is determined from the first test data as the first charging time.

[0107] Specifically, the above steps 1221 to 1222 can be represented by the following formula 2:

[0108]

[0109] wherein SOC1 represents the first preset state of charge, Ah cc,1 Q represents the target cumulative charging capacity, and Q represents the nominal capacity.

[0110] It can be understood that after obtaining the target cumulative charging capacity, the cumulative charging capacity recorded in the first test data equal to the target cumulative charging capacity is searched, so that the charging time corresponding to the target cumulative charging capacity can be determined, and thus the first charging time is obtained.

[0111] The above steps 121 to 122 are specific implementations for determining the first charging time. For determining the second charging time, the same implementation can be used, such as the formula 1 or the formula 2.

[0112] In addition, if the second preset state of charge is set to 100%, the second charging time can also be determined by the voltage data of the battery cell. It can be understood that when the second preset state of charge is 100%, the second charging time corresponding to the state of charge of the power battery being the second state of charge in the first charging test is the end of the charging time in the first charging test.

[0113] In this way, the first test data further comprises the maximum voltage of each battery cell of the power battery at each charging time in the first charging test. As known from the method recorded in step 8, in the first charging test, the end time of charging is the time when the voltage of any battery cell of the power battery reaches the voltage upper limit V Limit+ , and thus the charging time corresponding to the maximum voltage equal to the voltage upper limit V Limit+ in the first test data is the second charging time.

[0114] After determining the first charging time and the second charging time, the following steps 130 to 150 need to be continuously executed.

[0115] Continuing to refer to the figure, in step 130, based on the first test data, the accumulated charging coulomb of the power battery in the time period from the first charging time to the second charging time is determined.

[0116] In the embodiment, the first test data further comprises the charging current of the power battery at each charging time in the first charging test.

[0117] The accumulated charging coulomb is specifically implemented by taking the sum of the charging current of the power battery at each charging time between the first charging time and the second charging time as the accumulated charging coulomb.

[0118] Specifically, it can be expressed as the following formula 3:

[0119]

[0120] Wherein, C cc represents the accumulated charging coulomb, t1 represents the first charging time, t2 represents the second charging time, and i(t) represents the charging current in the first charging test.

[0121] It can be understood that, since the time interval of the power battery charging and discharging equipment sampling the charging current is 1s, the charging current is equal to the charging coulomb.

[0122] Wherein, coulomb is used to measure the actual transferred charge amount in the charging and discharging process. In the power battery charging and discharging process, because of the existence of the power battery internal resistance and the connection internal resistance, etc., heat will be generated, and there will be heat loss. At the same time, considering that the power supply conversion efficiency of the power battery charging and discharging equipment is less than 100%, part of the energy is lost, and considering the accumulated error of the ampere-hour integral of the power battery charging and discharging equipment, finally, the charging and discharging ampere-hour (charging and discharging capacity) recorded by the power battery charging and discharging equipment and the charging and discharging coulomb have certain differences. It can be seen that the charging and discharging coulomb can more accurately reflect the charging and discharging capacity.

[0123] Continuing to refer to Figure 2, step 140, determining, based on the first test data, a target discharge time point corresponding to a cumulative discharge coulomb of the power battery being equal to a cumulative charge coulomb in the first discharge test.

[0124] Specifically, the target discharge time point can be calculated by the following formula 4 and formula 5:

[0125]

[0126] wherein, C dc represents the cumulative discharge coulomb, t l represents a discharge start time point in the first discharge test, t m represents the target discharge time point, i n represents a discharge current in the first discharge test, t1 represents a first charge time point, t2 represents a second charge time point, and i(t) represents a charge current in the first charge test.

[0127] It should be noted that the charge current and the discharge current are both equal to 0 when the power battery is fully at rest, and thus the discharge start time point t l in the first discharge test can be determined based on a change of the discharge current.

[0128] Continuing to refer to Figure 2 , step 150, dividing the target cumulative discharge energy by a difference between a second cumulative charge energy and a first cumulative charge energy to obtain an energy efficiency, the target cumulative discharge energy being a cumulative discharge energy corresponding to the target discharge time point in the first test data, the first cumulative charge energy being a cumulative charge energy corresponding to the first charge time point in the first test data, and the second cumulative charge energy being a cumulative charge energy corresponding to the second charge time point in the first test data.

[0129] Specifically, the embodiment can be represented as the following formula 6:

[0130]

[0131] wherein, η represents an energy efficiency of the power battery (which can also be described as an energy efficiency of the power battery in a specific SOC interval, the specific SOC interval being an interval composed of the first preset state of charge and the second preset state of charge), Wh dc,m represents the target cumulative discharge energy, i.e., a cumulative discharge energy corresponding to the target discharge time point; Wh cc,2 represents the second cumulative charge energy, i.e., a cumulative charge energy corresponding to the second charge time point; and Wh cc,1 represents the first cumulative charge energy, i.e., a cumulative charge energy corresponding to the first charge time point.

[0132] In some embodiments of the present application, after the energy efficiency is determined, the determined energy efficiency is compared with a preset energy efficiency threshold value, and if the determined energy efficiency is greater than or equal to the energy efficiency threshold value, it is determined that the energy efficiency of the power battery meets the performance requirement.

[0133] For example, if the first cumulative charging energy, the second cumulative charging energy and the target cumulative discharging energy are determined, and the energy efficiency is calculated as shown in Table 2, it can be determined that the power battery meets the performance requirement.

[0134]

[0135] Table 2

[0136] The above is a specific embodiment for determining the energy efficiency. If the capacity evaluation parameter further includes the average discharging capacity and the average discharging energy, the steps shown in FIG. 4 can be further performed. Figure 4

[0137] Referring to FIG. 4, a second flowchart for determining the capacity evaluation parameter of the power battery according to an embodiment of the present application is shown, which specifically includes the following steps 410 to 430. Figure 4

[0138] In step 410, the second test data is obtained, which is obtained by performing multiple charging and discharging tests on the power battery. The charging and discharging test includes a second charging test and a second discharging test performed in sequence, and the second test data includes the first cumulative discharging capacity and the first cumulative discharging energy of the power battery at the end of the second discharging test.

[0139] It can be understood that if the obtained second test data is the data generated in steps 2, 3 and 4 of the present application, the average discharging capacity and the average discharging energy under the condition of 1 / 3C discharging rate can be obtained; if the obtained second test data is the data generated in steps 5, 6 and 7 of the present application, the average discharging capacity and the average discharging energy under the condition of 1C discharging rate can be obtained.

[0140] It can be understood that if the obtained second test data is the data generated in steps 2, 3 and 4 of the present application, the average discharging capacity and the average discharging energy under the condition of 1 / 3C discharging rate can be obtained; if the obtained second test data is the data generated in steps 5, 6 and 7 of the present application, the average discharging capacity and the average discharging energy under the condition of 1C discharging rate can be obtained.

[0141] ​​It should be noted that the power battery can be tested according to steps 1 to 17 in sequence, so that the data generated in steps 2, 3, and 4 in steps 1 to 17 is taken as the second test data, or the data generated in steps 5, 6, and 7 in steps 1 to 17 is taken as the second test data. Alternatively, after obtaining the power battery, the power battery can be first tested according to step 1, and after step 1 is performed, step 2, 3, or 5, 6, and 7 is directly performed to obtain the second test data.

[0142] It should also be understood that the second charging test can be step 2 described above, that is, the specific method of the second charging test is to maintain the temperature of the variable temperature box at a specific temperature T1, charge the power battery in a standard charging manner, and fully stand the power battery after charging.

[0143] The second discharge test can be step 3 described above, that is, the specific method of the second discharge test is to discharge at a specific discharge rate C1 in a constant current manner until the voltage of any cell in the power battery is lower than V Limit- when the temperature of the variable temperature box is kept at a specific temperature T1, and stop discharging and fully stand after stopping discharging. The specific discharge rate C1 is 1 / 3C.

[0144] The second discharge test can also be step 6 described above, that is, the specific method of the second discharge test is to discharge at a specific discharge rate C2 in a constant current manner until the voltage of any cell in the power battery is lower than V Limit- when the temperature of the variable temperature box is kept at a specific temperature T1, and stop discharging and fully stand after stopping discharging. The specific discharge rate C2 is 1C.

[0145] Referring back to Figure 4 , step 420, the average of the first cumulative discharge capacities corresponding to each charging and discharging test is calculated to obtain the average discharge capacity.

[0146] It should be understood that the first cumulative discharge capacity corresponding to each charging and discharging test is the first cumulative discharge capacity corresponding to the end of the second discharge test in the charging and discharging test, which represents the total discharge capacity released by the power battery in the second charging test. Therefore, the average of the first cumulative discharge capacities corresponding to each charging and discharging test is taken as the average discharge capacity of the power battery.

[0147] Referring back to Figure 4 , step 430, the average of the first cumulative discharge energies corresponding to each charging and discharging test is calculated to obtain the average discharge energy.

[0148] It is understandable that the first cumulative discharge energy corresponding to each charge-discharge test is the first cumulative discharge energy corresponding to the end time of the second discharge test in that charge-discharge test, representing the total discharge energy released by the power battery in that second charge test. Therefore, the average value of each first cumulative discharge energy corresponding to each charge-discharge test is taken as the average discharge energy of the power battery.

[0149] In this application, after determining the average discharge capacity and average discharge energy of the power battery, it is also possible to determine whether the average discharge capacity and average discharge energy of the power battery meet the performance requirements based on the pre-set discharge capacity evaluation threshold and discharge energy evaluation threshold. If the determined average discharge capacity is greater than or equal to the discharge capacity evaluation threshold and the determined average discharge energy is greater than or equal to the discharge energy evaluation threshold, it indicates that the average discharge capacity and average discharge energy of the power battery meet the performance requirements.

[0150] For example, if the determined average discharge energy and average discharge capacity are as shown in Table 3 below, it can be determined that the power battery meets the performance requirements.

[0151]

[0152] Table 3

[0153] The test results in Table 3 are the test data obtained by repeating steps 5 and 6 of this application three times.

[0154] The above describes the specific implementation methods for determining the average discharge capacity and average discharge energy. If the capacity evaluation parameters also include capacity retention rate and energy retention rate, the following methods can also be implemented: Figure 5 The steps are shown.

[0155] Figure 5 The diagram illustrates a third flowchart of a method for determining power battery capacity evaluation parameters according to an embodiment of this application, specifically including the following steps 510 to 540:

[0156] Step 510: Obtain the third test data. The third test data is obtained by sequentially performing a third charging test and a third discharging test on the power battery. The third charging test is performed at a first set temperature, and the third discharging test is performed at a second set temperature. The second set temperature is greater than or less than the first set temperature. The third test data includes the second cumulative discharge capacity and the second cumulative discharge energy of the power battery at the end of the third discharging test.

[0157] In this embodiment, the first set temperature is preferably 25°C.

[0158] The third charging test can be the step 12 or the step 15 of the above application, that is, the test method of the third charging test is that the power battery is charged in a standard charging mode under the environment that the temperature of the variable temperature box is a specific temperature T1, and the power battery is fully rested after the charging is completed. The specific temperature T1 is the first set temperature.

[0159] If it is necessary to determine the high-temperature capacity retention and the high-temperature energy retention of the power battery, the third discharging test can be the step 14 of the above application, that is, the test method of the third discharging test is that the power battery is discharged in a constant current mode at a specific discharge rate C1 under the environment that the temperature of the variable temperature box is a specific temperature T2 (that is, a second set temperature greater than the first set temperature), the discharging is stopped when the voltage of any one battery cell in the power battery is lower than V Limit- , and the power battery is fully rested after the discharging is stopped. The specific discharge rate C1 is 1 / 3C, and T2 is preferably 35℃.

[0160] If it is necessary to determine the low-temperature capacity retention and the low-temperature energy retention of the power battery, the third discharging test can be the step 17 of the above application, that is, the test method of the third discharging test is that the power battery is discharged in a constant current mode at a specific discharge rate C1 under the environment that the temperature of the variable temperature box is a specific temperature T3 (that is, a second set temperature less than the first set temperature), the discharging is stopped when the voltage of any one battery cell in the power battery is lower than V Limit- , and the power battery is fully rested after the discharging is stopped. The specific discharge rate C1 is 1 / 3C, and T3 is preferably 0℃.

[0161] It should be noted that the power battery can be tested in sequence according to the above steps 1 to 17, so that the data generated in the steps 12, 13 and 14 of the steps 1 to 17 is taken as the third test data, or the data generated in the steps 15, 16 and 17 of the steps 1 to 17 is taken as the third test data. Alternatively, after the power battery is obtained, the power battery is first tested according to the above step 1, and after the above step 1 is completed, the above steps 12, 13 and 14 are directly performed, or the above steps 15, 16 and 17 are directly performed, so as to obtain the third test data.

[0162] Referring back to Figure 5 , the fourth test data is obtained in the step 520, the fourth test data is obtained by sequentially performing a fourth charging test and a fourth discharging test on the power battery at the first set temperature, and the fourth test data includes a third cumulative discharging capacity and a third cumulative discharging energy of the power battery at the end of the discharging of the fourth discharging test.

[0163] The fourth charging test can be the test method of step 3 of the above application, that is, the test method of the fourth charging test is that the temperature of the variable temperature box is maintained at a specific temperature T1, and the power battery is charged in a standard charging mode. After the power battery is charged, the power battery is fully rested.

[0164] The fourth discharge test can be the test method of step 4 of the above application, that is, the test method of the fourth discharge test is that in the environment where the temperature of the variable temperature box is kept at a specific temperature T1, a specific rate C1 is used to discharge to the voltage of any one battery cell in the power battery is lower than V Limit- , stop discharging, and fully rest after stopping charging.

[0165] It should be noted that the power battery can be tested in sequence according to the above steps 1 to 17, so that the data generated in steps 3 and 4 in steps 1 to 17 are taken as the fourth test data. Alternatively, after obtaining the power battery, the power battery is first tested according to the above step 1, and after the above step 1 is performed, the above steps 3 and 4 are directly performed to obtain the fourth test data.

[0166] Continue to participate Figure 5 , step 530, calculate the ratio of the second cumulative discharge capacity and the third cumulative discharge capacity to obtain the capacity retention rate.

[0167] Continue to participate Figure 5 , step 540, calculate the ratio of the second cumulative discharge energy and the third cumulative discharge energy to obtain the energy retention rate.

[0168] For example, the obtained energy retention rate is shown in Table 4 as follows:

[0169]

[0170] Table 4

[0171] In some embodiments provided by the application, the technical scheme of the application can determine different types of capacity evaluation parameters of the power battery from different dimensions. The application calculates the energy efficiency of the specific SOC interval by the equal coulomb method, avoids the energy loss and cumulative error of the traditional ampere-hour integral method, and makes the evaluation result closer to the actual electrochemical behavior of the power battery. Further, combining the discharge capacity average and the discharge energy average, the capacity retention rate and the energy retention rate as the capacity evaluation parameters, a multi-dimensional capacity evaluation system can be formed, which significantly improves the performance evaluation reliability of the power battery under complex working conditions, and provides accurate data support for BMS strategy optimization and vehicle performance guarantee.

[0172] Based on the same inventive concept, the embodiment of the application provides a device for determining a power battery capacity evaluation parameter, which can be used to execute the method for determining the power battery capacity evaluation parameter in the above-mentioned embodiment of the application. For details not disclosed in the embodiment of the application, refer to the above-mentioned embodiment of the method for determining the power battery capacity evaluation parameter.

[0173] Referring to Figure 6 , a block diagram of a device for determining a power battery capacity evaluation parameter according to an embodiment of the application is shown.

[0174] As Figure 6 shown, the device 600 for determining a power battery capacity evaluation parameter according to an embodiment of the application, the capacity evaluation parameter includes energy efficiency, and the device 600 comprises an acquisition unit 610, a first determination unit 620, a second determination unit 630, a third determination unit 640, and a fourth determination unit 650.

[0175] The acquisition unit 610 is configured to acquire first test data of the power battery, the first test data being obtained by sequentially performing a first charging test and a first discharging test on the power battery at a first set temperature, and the first test data comprising accumulated charging energy of the power battery at each charging time in the first charging test and accumulated discharging energy of the power battery at each discharging time in the first discharging test; the first determination unit 620 is configured to determine, based on the first test data, a first charging time corresponding to a first preset state of charge of the power battery in the first charging test and a second charging time corresponding to a second preset state of charge of the power battery, the second preset state of charge being greater than the first state of charge; the second determination unit 630 is configured to determine, based on the first test data, accumulated charging coulombs of the power battery in a time period from the first charging time to the second charging time; the third determination unit 640 is configured to determine, based on the first test data, a target discharging time corresponding to a case that the accumulated discharging coulombs of the power battery is equal to the accumulated charging coulombs in the first discharging test; and the fourth determination unit 650 is configured to divide a target accumulated discharging energy by a difference between a second accumulated charging energy and a first accumulated charging energy, to obtain the energy efficiency, the target accumulated discharging energy being the accumulated discharging energy corresponding to the target discharging time in the first test data, the first accumulated charging energy being the accumulated charging energy corresponding to the first charging time in the first test data, and the second accumulated charging energy being the accumulated charging energy corresponding to the second charging time in the first test data.

[0176] In some embodiments of the application, based on the foregoing scheme, the first determination unit 620 is further configured to acquire a nominal capacity of the power battery; and determine the first charging time based on the nominal capacity and the first test data.

[0177] In some embodiments of the present application, based on the foregoing scheme, the first test data further include the charging current of the power battery at each charging time in the first charging test, and the first determination unit 620 is further configured to: calculate the first charging time according to the following formula:

[0178]

[0179] wherein SOC1 represents the first preset state of charge, i(t) represents the charging current, t0 represents the charging start time of the first charging test, t1 represents the first charging time, and Q represents the nominal capacity.

[0180] In some embodiments of the present application, based on the foregoing scheme, the first test data further include the accumulated charging capacity of the power battery at each charging time in the first charging test, and the first determination unit 620 is further configured to: calculate the product of the first preset state of charge and the nominal capacity as the target accumulated charging capacity; and determine the charging time corresponding to the target accumulated charging capacity from the first test data as the first charging time.

[0181] In some embodiments of the present application, based on the foregoing scheme, the first test data further include the charging current of the power battery at each charging time in the first charging test, and the second determination unit 630 is further configured to: sum the charging current of the power battery at each charging time between the first charging time and the second charging time as the accumulated charging coulomb.

[0182] In some embodiments of the present application, based on the foregoing scheme, the first charging test is to charge the power battery according to the charging performance parameter table of the power battery, the charging performance parameter table records the correspondence among the state of charge, the temperature and the charging rate, and the first discharging test is to discharge the power battery according to the first discharging rate.

[0183] In some embodiments of the present application, based on the foregoing scheme, the first charging test is to charge the power battery according to the set charging rate, and the first discharging test is to discharge the power battery according to the second discharging rate.

[0184] In some embodiments of the present application, based on the foregoing scheme, the capacity evaluation parameter further includes a discharge capacity average value and a discharge energy average value, and the fourth determination unit 640 is further configured to: obtain second test data, the second test data being obtained by performing multiple charge-discharge tests on the power battery, the charge-discharge test including a second charge test and a second discharge test performed in sequence, and the second test data including a first cumulative discharge capacity and a first cumulative discharge energy of the power battery at an end time of the second discharge test; calculate an average value of each first cumulative discharge capacity corresponding to each charge-discharge test to obtain the discharge capacity average value; and calculate an average value of each first cumulative discharge energy corresponding to each charge-discharge test to obtain the discharge energy average value.

[0185] In some embodiments of the present application, based on the foregoing scheme, the capacity evaluation parameter further includes a capacity retention rate and an energy retention rate, and the fourth determination unit 640 is further configured to: obtain third test data, the third test data being obtained by performing a third charge test and a third discharge test on the power battery in sequence; the third charge test being performed at a first set temperature, and the third discharge test being performed at a second set temperature, the second set temperature being greater than or less than the first set temperature, and the third test data including a second cumulative discharge capacity and a second cumulative discharge energy of the power battery at an end time of the third discharge test; obtain fourth test data, the fourth test data being obtained by performing a fourth charge test and a fourth discharge test on the power battery in sequence at the first set temperature, and the fourth test data including a third cumulative discharge capacity and a third cumulative discharge energy of the power battery at an end time of the fourth discharge test; calculate a ratio of the second cumulative discharge capacity to the third cumulative discharge capacity to obtain the capacity retention rate; and calculate a ratio of the second cumulative discharge energy to the third cumulative discharge energy to obtain the energy retention rate.

[0186] Based on the same inventive concept, the embodiments of the present application provide a computer readable storage medium, the computer readable storage medium storing at least one computer program instruction, the at least one computer program instruction being loaded and executed by a processor to implement the operations performed by the method as described above.

[0187] The above only describes the embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of claims of the present application.

Claims

1. A method for determining the evaluation parameters of power battery capacity, characterized in that, Capacity evaluation parameters include energy efficiency, and the method includes: The first test data of the power battery is obtained by performing a first charging test and a first discharging test on the power battery in sequence at a first set temperature. The first test data includes the cumulative charging energy of the power battery at each charging moment in the first charging test and the cumulative discharging energy at each discharging moment in the first discharging test. Based on the first test data, the first charging time corresponding to the power battery's state of charge being the first preset state of charge, and the second charging time corresponding to the power battery's state of charge being the second preset state of charge, are determined in the first charging test, where the second preset state of charge is greater than the first state of charge. Based on the first test data, the cumulative charging coulombs of the power battery during the time period from the first charging moment to the second charging moment are determined. Based on the first test data, determine the target discharge time in the first discharge test when the cumulative discharge coulomb of the power battery is equal to the cumulative charging coulomb; The energy efficiency is obtained by dividing the target cumulative discharge energy by the difference between the second cumulative charging energy and the first cumulative charging energy. The target cumulative discharge energy is the cumulative discharge energy corresponding to the target discharge time in the first test data. The first cumulative charging energy is the cumulative charging energy corresponding to the first charging time in the first test data. The second cumulative charging energy is the cumulative charging energy corresponding to the second charging time in the first test data.

2. The method according to claim 1, characterized in that, The step of determining the first charging moment corresponding to the state of charge of the power battery being at a first preset state of charge during the first charging test, based on the first test data, includes: Obtain the nominal capacity of the power battery; The first charging time is determined based on the nominal capacity and the first test data.

3. The method according to claim 2, characterized in that, The first test data also includes the charging current of the power battery at each charging moment in the first charging test. Determining the first charging moment based on the nominal capacity and the first test data includes: The first charging time is calculated using the following formula: Wherein, SOC1 represents the first preset state of charge, i(t) represents the charging current, t0 represents the charging start time of the first charging test, t1 represents the first charging time, and Q represents the nominal capacity.

4. The method according to claim 1, characterized in that, The first test data also includes the cumulative charging capacity of the power battery at each charging moment in the first charging test. Determining the first charging moment based on the nominal capacity and the first test data includes: Calculate the product of the first preset state of charge and the nominal capacity, and use it as the target cumulative charging capacity; The charging time corresponding to the target cumulative charging capacity is determined from the first test data and is taken as the first charging time.

5. The method according to claim 1, characterized in that, The first test data also includes the charging current of the power battery at each charging moment in the first charging test. The step of determining the cumulative charging coulombs of the power battery during the time period from the first charging moment to the second charging moment based on the first test data includes: The sum of the charging currents of the power battery at each charging moment between the first charging moment and the second charging moment is taken as the cumulative charging coulomb.

6. The method according to claim 1, characterized in that, The first charging test involves charging the power battery according to the charging performance parameter table, which records the correspondence between state of charge, temperature, and charging rate. The first discharging test involves discharging the power battery according to a first discharging rate, or... The first charging test involves charging the power battery at a set charging rate, and the first discharging test involves discharging the power battery at a second discharging rate.

7. The method according to claim 1, characterized in that, The capacity evaluation parameters also include the average discharge capacity and the average discharge energy, and the method further includes: The second test data is obtained by performing multiple charge and discharge tests on the power battery. The charge and discharge tests include a second charge test and a second discharge test performed sequentially. The second test data includes the first cumulative discharge capacity and the first cumulative discharge energy of the power battery at the end of the discharge test in the second discharge test. Calculate the average value of each first cumulative discharge capacity corresponding to each charge and discharge test to obtain the average discharge capacity; The average value of the first cumulative discharge energy corresponding to each charge and discharge test is calculated to obtain the average discharge energy.

8. The method according to claim 1, characterized in that, The capacity evaluation parameters also include capacity retention and energy retention, and the method further includes: The third test data is obtained by sequentially performing a third charging test and a third discharging test on the power battery; the third charging test is performed at a first set temperature, and the third discharging test is performed at a second set temperature, wherein the second set temperature is greater than or less than the first set temperature; the third test data includes the second cumulative discharge capacity and the second cumulative discharge energy of the power battery at the end of the discharge of the third discharging test. The fourth test data is obtained by sequentially performing a fourth charging test and a fourth discharging test on the power battery at the first set temperature. The fourth test data includes the third cumulative discharge capacity and the third cumulative discharge energy of the power battery at the end of the discharge test in the fourth discharge test. The ratio of the second cumulative discharge capacity to the third cumulative discharge capacity is calculated to obtain the capacity retention rate; The energy retention rate is obtained by calculating the ratio of the second accumulated discharge energy to the third accumulated discharge energy.

9. A device for determining the evaluation parameters of power battery capacity, characterized in that, Capacity evaluation parameters include energy efficiency, and the device includes: The acquisition unit is used to acquire the first test data of the power battery. The first test data is obtained by performing a first charging test and a first discharging test on the power battery in sequence at a first set temperature. The first test data includes the cumulative charging energy of the power battery at each charging moment in the first charging test and the cumulative discharging energy at each discharging moment in the first discharging test. The first determining unit is used to determine, based on the first test data, the first charging time corresponding to when the state of charge of the power battery is a first preset state of charge, and the second charging time corresponding to when it is a second preset state of charge, wherein the second preset state of charge is greater than the first state of charge. The second determining unit is used to determine the cumulative charging coulombs of the power battery during the time period from the first charging moment to the second charging moment, based on the first test data. The third determining unit is used to determine, based on the first test data, the target discharge time corresponding to when the cumulative discharge coulomb of the power battery is equal to the cumulative charging coulomb in the first discharge test. The fourth determining unit is used to divide the target cumulative discharge energy by the difference between the second cumulative charging energy and the first cumulative charging energy to obtain the energy efficiency. The target cumulative discharge energy is the cumulative discharge energy corresponding to the target discharge time in the first test data, the first cumulative charging energy is the cumulative charging energy corresponding to the first charging time in the first test data, and the second cumulative charging energy is the cumulative charging energy corresponding to the second charging time in the first test data.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one piece of program code, which is loaded and executed by a processor to perform the operations performed by the method as described in any one of claims 1 to 8.

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