A power battery cycle life test method and test device

Abstract

The application relates to a power battery cycle life test method and a test device. The steps of the power battery cycle life test method are as follows: obtaining an initial discharge capacity of a power battery; performing cycle test on the power battery according to a set working condition, performing discharge capacity test after each cycle, obtaining a current discharge capacity C of the power battery x ; wherein the set working condition comprises an environment working condition, a charging working condition, a standing working condition and a discharging working condition, the discharging working condition is obtained according to an actual vehicle running working condition; the above operation is repeated, the capacity attenuation of the power battery cycle life is obtained through the initial discharge capacity and the current discharge capacity of the power battery, when the capacity attenuation reaches a set target, the test is stopped, and the time of the power battery cycle life is obtained according to the initial test time and the time when the test is stopped. The application can truly simulate the actual use of users, so that the service life of the power battery can be accurately evaluated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power batteries, in particular to a power battery cycle life test method and a test device. BACKGROUND

[0002] The power battery is one of the core components of the power assembly of an electric vehicle, and the service life performance of the power battery directly determines the service life of the electric vehicle.

[0003] At present, the conventional test method for the cycle life of the power battery is to perform standard cycles on the battery at a normal temperature of 25℃±2℃ with 1C, to convert each cycle into the NEDC driving range of the vehicle equipped with the power battery, and to obtain the driving range of the power battery.

[0004] For example, the NEDC driving range of a power battery of a certain vehicle model is 400km, and the standard cycle is 500 times, and thus the equivalent driving range is 200000km. However, according to market research, there is a large difference between the driving range obtained by the current battery cycle life test method and the actual driving range of the user, and the average deviation is as high as about 20%. Thus, the current battery cycle life test method cannot accurately estimate the cycle life of the power battery, and cannot intuitively feedback the service life of the battery vehicle.

[0005] Among them, the user's actual use of the vehicle includes the temperature of all four seasons (including high temperature, low temperature, normal temperature), the road conditions all over the country (urban roads, mountain roads, highways, etc.), and different charging conditions (slow charging, fast charging, the remaining power state of the vehicle before / after charging), and these use scenarios will all affect the cycle life of the power battery. Therefore, it is necessary to provide a new power battery cycle life test method. SUMMARY

[0006] The purpose of the present application is to provide a power battery cycle life test method and a test device to simulate the actual use of the user, and to accurately evaluate the service life of the power battery.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0008] A power battery cycle life test method, comprising the following steps:

[0009] S1, test the discharge capacity of the power battery to obtain the initial discharge capacity C0 of the power battery;

[0010] S2, cycle test the power battery according to the set working condition, return to S1 to test the discharge capacity of the power battery after each working condition cycle, and obtain the current discharge capacity C of the power battery x ; wherein the set working condition includes an environmental condition, a charging condition, a standing condition and a discharging condition, the charging condition can be obtained in real time according to the current battery state of charge and temperature of the power battery, and the discharging condition is obtained according to the actual running condition of the vehicle;

[0011] S3, repeat S1 and S2, obtain the capacity attenuation W of the cycle life of the power battery through the initial discharge capacity C0 and the current discharge capacity C of the power battery x of the power battery, and obtain the time of the cycle life of the power battery according to the initial test time and the time of stopping the test.

[0012] According to the above technical means, the power battery is simulated and tested from three dimensions of the environmental temperature, the road condition and the charging of the actual operation of the electric vehicle based on the working condition of the actual use of the vehicle by the user, so as to truly reflect the actual use of the user, thereby more accurately evaluating the service life of the power battery, providing an accurate performance prediction of the power battery in the whole life cycle of the electric vehicle for the user, and further improving the quality of the product and the recognition degree of the customer.

[0013] Preferably, the vehicle remote monitoring system collects the speed curves of different regions, different users and different times, and the speed curves are converted to obtain the discharging condition.

[0014] A large number of speed curves of different regions, different users and different times are collected by the vehicle remote monitoring system, and the speed curves are converted to obtain the discharging condition, so that the use of the power battery in the actual process can be more truly reflected, and the test result is more accurate.

[0015] Preferably, the environmental condition includes low temperature, medium temperature and high temperature, the temperature range of the low temperature is 5℃ to -10℃, the temperature range of the medium temperature is 15℃ to 25℃, and the temperature range of the high temperature is 35℃ to 40℃.

[0016] The environmental condition is designed as low temperature, medium temperature and high temperature to simulate the environmental temperature scenario of the actual use of the vehicle by the user, that is, to simulate the air temperature of four seasons (including high temperature, low temperature and medium temperature), thereby effectively ensuring the accuracy of the test result.

[0017] The medium temperature in the environmental condition is the so-called normal temperature, and the purpose of expressing it as medium temperature here is to distinguish it from the normal temperature in the standing condition.

[0018] Preferably, the S2, one working condition cycle includes a charging working condition, a standing working condition and a discharging working condition operated under low temperature, medium temperature and high temperature environment conditions respectively.

[0019] By operating the charging working condition, the standing working condition and the discharging working condition under different temperature conditions respectively, the actual situation of the user using the vehicle is fully simulated, and the accuracy of the test result is effectively ensured.

[0020] Preferably, the time ratio or mileage ratio of the discharging working condition operated under the low temperature, medium temperature and high temperature environment conditions is 0.35-0.4:0.3-0.35:0.25-0.3.

[0021] By setting the time ratio or mileage ratio of the discharging working condition operated under the low temperature, medium temperature and high temperature environment conditions as 0.35-0.4:0.3-0.35:0.25-0.3, the running situation of the power battery of the electric vehicle under different air temperatures in different seasons is simulated, and the accuracy of the test result is effectively ensured.

[0022] The power battery is cycled and operated under the low temperature, medium temperature and high temperature conditions without sequence requirement, as long as the time ratio or mileage ratio of the discharging working condition operated under the low temperature, medium temperature and high temperature conditions meets the condition.

[0023] Preferably, the power battery is operated under the charging working condition as follows: the current of the power battery that can be charged is obtained according to the current battery state of charge and temperature of the power battery, and the power battery is charged until the charging current is 0, and the charging is ended; the power battery is operated under the standing working condition as follows: the power battery after the charging is ended is stood for 30-60 minutes; the power battery is operated under the discharging working condition as follows: the power battery is discharged according to the conventional battery discharging power, and the maximum allowable charging and discharging power issued by the battery management system is compared with the power of the discharging working condition in real time, and the absolute minimum value is selected for discharging test.

[0024] By setting the charging working condition in the test process, the charging scenario of the power battery on the electric vehicle is truly restored by simulating the user plugging the gun to charge the power battery of the electric vehicle; the standing working condition is set to simulate the scenario that the user parks for a certain time after the power battery of the electric vehicle is fully charged; the discharging working condition is set to simulate the driving road condition when the user actually uses the electric vehicle, and the accuracy of the test result is effectively ensured.

[0025] Preferably, in the S1, specifically: under normal temperature conditions, the power battery is discharged at 1C to the discharge cut-off voltage U1, and is required to stand still; the power battery is charged at 1C to the charge cut-off voltage U2, and is converted to C / 5 to charge to the charge cut-off voltage U2, and is converted to C / 10 to charge to the charge cut-off voltage U2, and is converted to C / 20 to charge to the charge cut-off voltage U2, and is required to stand still; the power battery is discharged at 1C to the discharge cut-off voltage U1, and the initial discharge capacity C0 of the battery is obtained.

[0026] By adopting the discharge mode to discharge the battery power, and then adopting the step charging mode to charge, the battery charging power is more full, and the maximum discharge capacity of the battery is effectively reflected by adopting the discharge mode, so that the accuracy of the discharge capacity test is ensured.

[0027] Wherein, U1 is the discharge cut-off voltage specified by the manufacturer, and U2 is the charge cut-off voltage specified by the manufacturer. The discharge cut-off voltage and the charge cut-off voltage of each battery are different. And the batteries of each manufacturer are also different.

[0028] Preferably, the temperature of the normal temperature is between 20℃ and 30℃, the first standing requirement is: standing until the temperature of the power battery is stabilized between 20℃ and 30℃, and the second standing requirement is: standing for more than 30min and the temperature of the power battery is stabilized between 20℃ and 30℃.

[0029] Wherein, the purpose of the first standing and the second standing is to reduce the temperature of the battery, and also to restore the performance of the battery.

[0030] Preferably, the capacity attenuation W is obtained by formula I;

[0031]

[0032] In formula I, C0 represents the initial discharge capacity of the power battery, C x represents the current discharge capacity of the power battery, and W represents the capacity attenuation of the power battery.

[0033] The application also provides a test device based on the power battery cycle life test method.

[0034] A power battery performance test system for charging and discharging the power battery and collecting the voltage, current and temperature of the power battery;

[0035] A BMS for measuring the voltage, current and temperature of the power battery in real time;

[0036] A low-voltage power supply for providing voltage for the BMS;

[0037] A high-low temperature and humidity chamber for providing the ambient temperature for the power battery;

[0038] computer;

[0039] The battery and the BMS are combined into a power battery assembly (referred to as "power battery" for short), the power battery assembly is located in the high-low temperature and humidity chamber, the BMS is electrically connected with the low-voltage power supply and is in communication connection with the power battery performance test system, the power battery performance test system is electrically connected with the power battery, and the power battery performance test system is in communication connection with the computer.

[0040] The beneficial effects of the present application are:

[0041] The test method for the cycle life of the power battery of the present application can simulate the test of the power battery from the three dimensions of the environmental temperature, the road condition and the charging of the actual operation of the electric vehicle based on the working condition of the actual use of the vehicle, so as to truly reflect the actual use of the user, and compared with the existing test method, the service life of the power battery can be more accurately and intuitively evaluated, a more accurate performance prediction of the power battery in the whole life cycle of the electric vehicle is provided for the user, and the quality of the product and the recognition degree of the customer are improved, and the present application has a popularization and application value in the technical field of the power battery. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of the power battery cycle life test device of the present application.

[0043] Figure 2 It is a flowchart of the power battery cycle life test method of the present application.

[0044] Figure 3 It is a discharge working condition schematic diagram of the power battery cycle life test of the present application. DETAILED DESCRIPTION

[0045] The embodiments of the present application will be described below with reference to the drawings and preferred embodiments, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure in the specification. The present application can also be implemented or applied by means of other different specific embodiments, and various modifications or changes can be made to the details in the specification based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, and are not intended to limit the protection scope of the present application.

[0046] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner, and only the components related to the present application are shown in the diagrams, not the number, shape and size of the components when actually implemented, the actual implementation of each component may be a random change in type, number and proportion, and the component layout pattern may also be more complex.

[0047] In the following description, numerous specific details are discussed in order to provide a thorough understanding of the embodiments of the present application. However, the embodiments of the present application can be practiced without these specific details.

[0048] Embodiment 1

[0049] As shown in Figure 1 , a test device for cycle life of power battery, comprising:

[0050] a power battery performance test system for charging and discharging the power battery and collecting voltage, current and temperature of the power battery;

[0051] a BMS for measuring voltage, current and temperature of the power battery in real time;

[0052] a low-voltage power supply for providing voltage for the BMS (battery management system);

[0053] a high-low temperature and humidity chamber for providing ambient temperature for the power battery;

[0054] a computer;

[0055] a battery and a BMS combined into a power battery assembly (referred to as "power battery"), the power battery assembly is located in the high-low temperature and humidity chamber, the BMS is electrically connected with the low-voltage power supply and is communicatively connected with the power battery performance test system; the power battery performance test system is electrically connected with the power battery, and the power battery performance test system is communicatively connected with the computer.

[0056] Embodiment 2

[0057] As shown in Figure 2 , a method for testing cycle life of power battery by using the test device in embodiment 1, comprising the following steps:

[0058] S1, turn on the power system (i.e. all the power-on needs are turned on), configure the power battery and the computer according to the communication protocol file to realize normal communication;

[0059] S2, power on: send power-on command through the computer, the relay is closed, when the difference between the total voltage collected by the power battery performance test system and the total voltage displayed on the BMS is less than 2V, the power battery is charged and discharged for test; power off: send power-off command through the computer, the relay is opened, when the total voltage collected by the power battery performance test system drops to below 20V, the power battery cannot be charged and discharged for test;

[0060] S3, under the condition that the temperature is 23-27°C (i.e. the battery temperature collected by the BMS), the power battery is discharged at 1C to the discharge cut-off voltage U1, and is left to stabilize the temperature of the power battery at 23-27°C;

[0061] Charging according to the following step current: the power battery is charged at 1C to the charge cut-off voltage U2, at C / 5 to the charge cut-off voltage U2, at C / 10 to the charge cut-off voltage U2, and at C / 20 to the charge cut-off voltage U2;

[0062] After being left for more than 30 min and the temperature of the battery assembly stabilizes at 23-27°C, the power battery is discharged at 1C to the discharge cut-off voltage U1, and the power battery performance test system 1 collects the initial discharge capacity C0 of the power battery;

[0063] S4, power battery cycle life test:

[0064] S41, running the charging condition, specifically: sending a fast charging command through the computer, after the BMS receives the fast charging command requirement, the BMS calculates the current charging current of the power battery (the current corresponding to the battery state of charge and temperature, as shown in Table 1) according to the current state of the power battery (specifically including the battery state of charge, temperature, etc.), and sends a charging request to the power battery performance test system, the power battery performance test system charges the power battery according to the requested current until the requested charging current is 0, then the charging is completed. The charging condition is used to simulate the user charging the battery of the electric vehicle, to truly restore the charging scene of the power battery on the electric vehicle;

[0065] S42, running the standing condition, specifically: after the power battery is fully charged, sending a power-off command through the computer, the relay is opened, and left for 30-60 min. The standing condition is used to simulate that the user will park for a certain period of time after the electric vehicle is fully charged;

[0066] S43, running the discharging condition, specifically: sending a power-on command through the computer, and closing the relay; running the discharging condition, comparing the actual maximum allowed charging and discharging power of the BMS with the power of the discharging condition in real time, and selecting the absolute minimum value to discharge. When running according to the discharging condition to the lowest SOC allowed by the vehicle, the charging condition is entered, the power battery is left after being fully charged, and the test is continued from the last discharging condition breakpoint, for example: the discharging condition has a power of 1000 points, the battery runs the discharging condition to discharge to 200 points, and the battery runs out of power at this time, then the battery is charged, after being fully charged, the battery continues to discharge according to the discharging condition;

[0067] The discharge condition includes running X (0.25-0.3) under low-temperature condition of 5-10℃, running X (0.35-0.4) under medium-temperature condition of 15-25℃, and running X (0.3-0.35) under high-temperature condition of 35-40℃, wherein X represents total time or total mileage of running the discharge condition, for example, the total time of the discharge condition is 10000 hours, the discharge condition under the low-temperature condition of 5-10℃ is 10000 (0.25-0.3) hours, the discharge condition under the medium-temperature condition of 15-25℃ is 10000 (0.35-0.4) hours, and the discharge condition under the high-temperature condition of 35-40℃ is 10000 (0.3-0.35) hours.

[0068] The discharge condition is obtained by collecting a large number of vehicle speed curves of different regions, different users and different times through a vehicle remote monitoring system, and converting and processing to obtain a discharge condition reflecting the battery bench test cycle life of the real use of the user. Figure 3

[0069] Table 1 SOC, temperature limit maximum charging current table

[0070]

[0071] S5, the power battery runs the charging condition, the discharge condition and returns to S3 after running the discharge condition under different temperature conditions, and the discharge capacity test of the power battery is carried out once to obtain the current discharge capacity C of the power battery. x The capacity attenuation rate w of the power battery cycle life is calculated by formula I.

[0072]

[0073] In formula I, C0 represents the initial discharge capacity of the power battery, C represents the current discharge capacity of the power battery, and W represents the capacity attenuation of the power battery. x

[0074] When the capacity attenuation rate w of the power battery reaches the set target value, the test is stopped.

[0075] The time from the performance test time of the power battery to the time when the power battery stops the test is the cycle life time of the power battery.

[0076] ​​In summary, the test method for cycle life of the power battery, by simulating the test of the power battery from the three dimensions of the environment temperature, road condition and charging of the actual operation of the electric vehicle based on the working condition of the actual use of the vehicle, can truly reflect the actual use condition, so as to more accurately evaluate the service life of the power battery, provide an accurate performance prediction of the power battery in the whole life cycle of the electric vehicle for the user, and further improve the product quality and the recognition degree of the customer, and has the popularization and application value in the technical field of the power battery.

[0077] The above embodiments are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical thought of the present application should be covered by the claims of the present application.

Claims

1. A power battery cycle life test method, characterized in that, Comprise the following steps: S1, test the discharge capacity of the power battery to obtain the initial discharge capacity of the power battery ; S2, according to the set working condition, the power battery is cycled, after each working condition cycle, return to S1 to test the discharge capacity of the power battery, and obtain the current discharge capacity of the power battery The working condition cycle includes a charging working condition, a standing working condition and a discharging working condition running under low-temperature, medium-temperature and high-temperature environment conditions respectively; the time ratio or mileage ratio of the discharging working conditions running under the low-temperature, medium-temperature and high-temperature environment conditions is 0.35-0.4:0.3-0.35:0.25-0.3; Wherein, set the working condition includes environmental conditions, charging conditions, static conditions and discharge conditions, the charging conditions are obtained according to the current battery state of charge and temperature of power battery, the discharge conditions are obtained according to the actual operation conditions of vehicle, specifically through the vehicle remote monitoring system to collect the speed curve of different regions, different users and different time, the speed curve is obtained after conversion processing the discharge conditions;The environmental conditions include low temperature, medium temperature and high temperature, the temperature range of low temperature is 5℃~-10℃, the temperature range of medium temperature is 15℃~25℃, the temperature range of high temperature is 35℃~40℃; S3, repeating S1 and S2, obtaining the initial discharge capacity of the power battery and the current discharge capacity obtaining the capacity attenuation W of the cycle life of the power battery, stopping the test when the capacity attenuation W reaches a set target, and obtaining the time of the cycle life of the power battery according to the initial test time and the time of stopping the test. In the S1, the power battery is discharged at 1C to a discharge cut-off voltage U1 under normal temperature condition, and is required to stand still; the power battery is charged at 1C to a charge cut-off voltage U2, and is charged at C / 5 to the charge cut-off voltage U2, at C / 10 to the charge cut-off voltage U2, at C / 20 to the charge cut-off voltage U2, and is required to stand still; the power battery is discharged at 1C to the discharge cut-off voltage U1, and the initial discharge capacity of the battery is obtained .

2. The power battery cycle life test method according to claim 1, characterized in that, The power battery running charging condition is specifically: according to the current battery state of charge and temperature of power battery, the current power battery current that can be charged is obtained by table lookup, and the power battery is charged until the charging current is 0, and the charging is finished;The power battery running static condition is specifically: the power battery after charging is static for 30min~60min;The power battery running discharge condition is specifically: the power battery is discharged according to the conventional battery discharge power, and the maximum allowable charge-discharge power issued by the battery management system is compared with the power of the discharge condition in real time, and the absolute minimum value is selected to discharge test.

3. The power battery cycle life test method of claim 1, wherein, The temperature of the normal temperature is between 23℃~27℃, the first static requirement is: static until the temperature of power battery is stabilized at 20℃~30℃, the second static requirement is: static for more than 30min and the temperature of power battery is stabilized at 20℃~30℃.

4. The power battery cycle life test method of claim 1, wherein, The capacity attenuation W is obtained by formula I; （Ⅰ） in formula I, represents the initial discharge capacity of the power battery, represents the current discharge capacity of the power battery, represents the capacity attenuation of the power battery.

5. A test device based on the test method of the cycle life of a power battery according to any one of claims 1 to 4, characterized in that, Comprise: The power battery performance test system for charging and discharging power battery and collecting voltage, current and temperature of power battery; BMS for real-time measurement of voltage, current and temperature of power battery; Low-voltage power supply for providing voltage for BMS; High-low temperature and humidity chamber for providing environmental temperature for power battery; Computer; The battery and BMS are combined into power battery assembly, the power battery assembly is located in the high-low temperature and humidity chamber, the BMS is electrically connected with the low-voltage power supply, and is communicatively connected with the power battery performance test system;The power battery performance test system is electrically connected with the power battery, and the power battery performance test system is communicatively connected with the computer.

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