A power battery cycle testing method

Abstract

The present invention relates to a power battery cycle testing method, comprising the following steps: step S1: standard discharge; step S2: rest; step S3: slow charge; step S4: rest; step S5: discharge; step S6: repeat steps S2 to S5, cycle n times, 10≥n≥1; step S7: fast charge; step S8: rest; step S9: discharge; step S10: repeat steps S2 to S9, cycle m times, m≥100; the number of cycles and the energy of each discharge are recorded, and the electrical performance of the battery pack is calculated based on the number and energy. The testing method provided by the present invention can simulate both fast and slow charging modes, and adds pulse and recharge processes during the discharge process, simulating the acceleration and energy recovery conditions of the entire vehicle during driving, thereby more accurately reflecting the actual state of the battery pack, conforming to the actual operating conditions of the entire vehicle, and greatly improving the accuracy of the test results.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile performance testing, and in particular to a power battery cycle testing method. Background Art

[0002] With the increasing demands for environmental protection and energy conservation in society, new energy vehicles have become a key development direction in the automotive industry. As a key component of electric vehicles, the performance of power batteries will directly affect the development and application prospects of electric vehicles.

[0003] Since the life of power batteries is an important performance indicator of power batteries, in order to study the life of power batteries, the current test methods mostly use a 25°C, 1C charging, 1C discharging cycle test process. This process has a large temperature rise and a long test cycle, which is very different from the actual operating conditions of the power battery when installed in an electric vehicle. It cannot accurately simulate the actual operating conditions of the entire vehicle and cannot obtain accurate battery pack post-cycle electrical performance data. Therefore, the effectiveness of the test is poor.

[0004] Therefore, how to provide a power battery cycle testing method that can simulate the actual working conditions of the power battery during application and save testing time and cost is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The present invention provides a power battery cycle testing method to solve the above technical problems.

[0006] To solve the above technical problems, the present invention provides a power battery cycle testing method, comprising the following steps:

[0007] Step S1: standard discharge, comprising: placing the battery pack in a temperature box, adjusting the temperature in the temperature box to 25°C, and discharging at a current of 1C until the voltage of the battery pack reaches the lower limit of the usable voltage;

[0008] Step S2: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C;

[0009] Step S3: slow charging, comprising: charging the battery pack with a slow charging current until the voltage of the battery pack reaches the lower limit of the available voltage;

[0010] Step S4: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C;

[0011] Step S5: Discharging, including: a pulse process and a recharge process, wherein the discharging refers to:

[0012] Step S51: discharging at 0.5C current for 15 minutes;

[0013] Step S52: let stand for 10 seconds;

[0014] Step S53: discharging at 2C current for 30s;

[0015] Step S54: let stand for 10 seconds;

[0016] Step S55: charging at 0.5C current for 10 seconds;

[0017] Step S56: Repeat steps S51 to S55 until the voltage of the battery pack reaches the lower limit of the available voltage;

[0018] Step S6: repeat steps S2 to S5 for n times, where 10≥n≥1;

[0019] Step S7: fast charging, comprising: charging the battery pack with a fast charging current until the voltage of the battery pack reaches the lower limit of the available voltage;

[0020] Step S8: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C;

[0021] Step S9: discharging;

[0022] Step S10: repeat steps S2 to S9 for m times, where m ≥ 100;

[0023] The number of cycles and the energy of each discharge are recorded, and the electrical performance of the battery pack is estimated based on the number and energy.

[0024] Preferably, the stable state means that within a minute, the change values ​​of the voltage and temperature of each single cell in the battery pack are respectively less than a first threshold value and a second threshold value.

[0025] Preferably, a cooling system is installed on the battery pack, and during the cycle test, the cooling system is turned on and off by a controller.

[0026] Preferably, the controller also controls the initial temperature and flow rate of the coolant in the cooling system.

[0027] Preferably, the controller controls the cooling system to start in steps S3, S5, S7 and S9, and makes the temperature of the battery pack ≤ 35°C.

[0028] Preferably, the controller controls the cooling system to start in steps S2, S4 and S8.

[0029] Preferably, during the charging process of steps S3 and S7, a step-by-step charging method is used for charging.

[0030] Compared with the prior art, the power battery cycle testing method provided by the present invention has the following advantages:

[0031] 1. The test method provided by the present invention simulates two charging modes, fast charging and slow charging, and adds pulse and recharge processes during the discharge process, simulating the acceleration and energy recovery conditions of the vehicle during driving, thereby more accurately reflecting the actual state of the battery pack, conforming to the actual operating conditions of the vehicle, and greatly improving the accuracy of the test results;

[0032] 2. The present invention adds a cooling system to the battery pack. By controlling the cooling system, rapid cooling can be achieved, ensuring detection safety while shortening detection time and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of a power battery cycle testing method according to a specific embodiment of the present invention;

[0034] Figure 2a This is a graph showing the changes in current and voltage over time during slow charging using a step-by-step current charging process in a specific embodiment of the present invention;

[0035] Figure 2b This is a graph showing the change of current and SOC over time during slow charging using a step-by-step current charging process in a specific embodiment of the present invention;

[0036] Figure 3a This is a graph showing the change of current and voltage over time during the discharge process using a step-by-step current charge in a specific embodiment of the present invention;

[0037] Figure 3b This is a graph showing the change of current and SOC over time during discharge using a step-by-step current charge in a specific embodiment of the present invention;

[0038] Figure 4a This is a graph showing the changes in current and voltage over time during fast charging using a step-by-step current charging process in a specific embodiment of the present invention;

[0039] Figure 4b This is a graph showing how current and SOC change over time during fast charging using a step-by-step current charging process in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to describe the technical solution of the above invention in more detail, specific embodiments are listed below to demonstrate the technical effects; it should be emphasized that these embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0041] The power battery cycle test method provided by the present invention is as follows: Figure 1 As shown, the following steps are included:

[0042] Step S1: standard discharge, including: placing the battery pack in a temperature box, adjusting the temperature in the temperature box to 25°C, and discharging at a current of 1C until the voltage of the battery pack reaches the lower limit of the usable voltage. The "usable voltage" in this application refers to the voltage specified by the manufacturer according to different battery types. For example, in some embodiments, the usable voltage range of a certain model of battery pack is 2.8V to 4.2V, then the lower limit of the usable voltage is 2.8V, and the upper limit of the usable voltage is 4.2V.

[0043] Step S2: Stand still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C. Specifically, the stable state means that within a minute, the change in the voltage and temperature of each single cell in the battery pack is less than the first threshold and the second threshold, respectively. In some embodiments, a can take any time value within 30s to 5min, the first threshold can be 0.1V, and the second threshold can be 0.1°C. It should be noted that in all "standing" steps (including steps S2, S4, and S8), a cooling system can be used to accelerate cooling, thereby saving testing time and cost.

[0044] Please refer to Figure 2a and Figure 2b Step S3: slow charging, including: charging the battery pack with a slow charging current (e.g., 0.3C) until the voltage of the battery pack reaches the lower limit of the available voltage. For the description of "available voltage" and "lower limit", please refer to step S1;

[0045] Step S4: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C. For details, please refer to step S2;

[0046] Please refer to Figure 3a and Figure 3b Step S5: Discharging, including: pulse process and recharge process. The discharging means:

[0047] Step S51: discharging at 0.5C current for 15 minutes, simulating the battery pack usage state when the vehicle is traveling at a constant speed;

[0048] Step S52: let stand for 10 seconds;

[0049] Step S53: discharging at 2C current for 30 seconds. This is a pulse process, used to simulate the battery pack usage status when the vehicle is accelerating.

[0050] Step S54: let stand for 10 seconds;

[0051] Step S55: charging at 0.5C current for 10 seconds. This is the recharging process, which is used to simulate the battery pack usage status during partial current recharging during braking.

[0052] Step S56: Repeat steps S51 to S55 until the voltage of the battery pack reaches the lower limit of the available voltage. The present application adds a pulse process and a recharge process during the discharge process to accurately simulate the acceleration and energy recovery conditions of the vehicle during driving.

[0053] Step S6: repeat steps S2 to S5. This cycle can be defined as the first cycle, which is repeated n times, where 10≥n≥1.

[0054] Please refer to Figure 4a and Figure 4b Step S7: fast charging, including: charging the battery pack with a fast charging current (e.g., 1C) until the voltage of the battery pack reaches the lower limit of the available voltage. For the description of "available voltage" and "lower limit", please refer to step S1;

[0055] Step S8: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C. For details, please refer to step S2;

[0056] Step S9: discharging. The specific steps of discharging are the same as those of step S5.

[0057] Step S10: Repeat steps S2 to S9, which is defined as the second cycle, with m cycles, where m ≥ 100. In this application, the second cycle includes the first cycle, that is, simulating multiple slow charging processes corresponding to one fast charging process, which can be used to correspond to the number and frequency of use of household slow charging devices and public fast charging devices in actual applications. The test method of this application takes into account both fast charging and slow charging modes, further accurately simulates the actual working conditions of the vehicle, and then obtains the electrical performance data of the battery pack after cycling.

[0058] The number of cycles and the energy discharged each time are recorded. Based on the number and energy, the electrical performance of the battery pack is estimated. For example, the discharge energy of the battery pack in the first test is 50 kWh, corresponding to a cruising range of 400 kilometers. After m tests, the remaining discharge energy of the battery pack is 30 kWh, then the corresponding cruising range is 400 kilometers × (30 ÷ 50) = 240 kilometers. Similarly, through simple proportional calculations, the electrical performance of the battery pack after m tests can be obtained.

[0059] The present invention adopts the above-mentioned testing method, which shortens the testing time, and can accurately simulate the working conditions of the entire vehicle, and accurately obtain the electrical performance, safety and reliability data of the battery pack after the entire vehicle has traveled a certain number of kilometers.

[0060] Preferably, the battery pack is equipped with a cooling system, which can be built into the battery pack or dedicated to the test. The structure and control method of the cooling system are not limited in this application, as long as it can cool the battery pack. During the cycle test, the controller controls the opening and closing of the cooling system; the controller also controls the initial temperature and flow rate of the coolant in the cooling system. For example, a cooling pipe wound around the battery pack is used as a cooling device, and coolant flows through the cooling pipe. PID control is used to control the initial temperature and flow rate of the coolant flowing into the cooling pipe. The battery pack is then cooled according to actual needs, ensuring the safety of the test while shortening the test time and saving test costs.

[0061] Preferably, the controller can control the cooling system to start in steps S3, S5, S7 and S9, and make the temperature of the battery pack ≤35°C. The present application cools the battery pack during the charging and discharging process to avoid excessive temperature caused by the heat generated during the charging and discharging process, thereby increasing the cooling waiting time, which can greatly reduce the testing time and cost.

[0062] Preferably, the controller controls the cooling system to start in steps S2, S4 and S8, that is, the present application cools the battery pack when the battery pack is at rest, shortens the rest waiting time, and further saves the time and cost of testing.

[0063] Preferably, during the charging process of steps S3 and S7, a step-by-step charging method is used for charging. Specifically, the step-by-step charging method refers to charging the battery pack with different charging currents according to different charging stages. For example, for the slow charging in step S3, when the charge is 0-95%, it is charged according to a 0.2C current, and when the charge is 95%-100%, it is charged according to a 0.1C current; for the fast charging in step S7, when the charge is 0-80%, it is charged according to a 1C current, when the charge is 80%-90%, it is charged according to a 0.8C current, when the charge is 90%-95%, it is charged according to a 0.5C current, and when the charge is 95%-100%, it is charged according to a 0.3C current. This application adopts a step-by-step charging method, which is closer to the actual charging method used by the whole vehicle, further improving the accuracy of the test.

[0064] In summary, the power battery cycle test method provided by the present invention includes the following steps: Step S1: standard discharge, including: placing the battery pack in a temperature box, adjusting the temperature in the temperature box to 25°C, and discharging at a current of 1C until the voltage of the battery pack reaches the lower limit of the usable voltage; Step S2: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C; Step S3: slow charging, including: charging the battery pack with a slow charging current until the voltage of the battery pack reaches the lower limit of the usable voltage; Step S4: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤

[0065] 30°C; Step S5: Discharging, wherein the discharging includes: Step S51: discharging at 0.5C current for 15 minutes; Step S52: standing for 10 seconds; Step S53: discharging at 2C current for 30 seconds; Step S54: standing for 10 seconds; Step S55: charging at 0.5C current for 10 seconds; Step S56: repeating Steps S51 to S55 until the voltage of the battery pack reaches the lower limit of the usable voltage; Step S6: repeating Steps S2 to S5, for n times, 10≥n≥1; Step S7: Fast charging includes: charging the battery pack with a fast charging current until the voltage of the battery pack reaches the lower limit of the available voltage; step S8: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C; step S9: discharging; step S10: repeating steps S2 to S9 for m cycles, m≥100; recording the number of cycles and the energy of each discharge, and calculating the electrical performance of the battery pack based on the number and energy. The test method provided by the present invention simulates two charging modes, fast charging and slow charging, and adds a pulse process and a recharge process during the discharge process. The pulse process uses a large current to simulate the acceleration of the whole vehicle, and the recharge process simulates the energy recovery process of the whole vehicle, thereby simulating the acceleration and energy recovery conditions of the whole vehicle when driving, thereby more accurately reflecting the actual state of the battery pack, conforming to the actual operating conditions of the whole vehicle, and greatly improving the accuracy of the test results.

[0066] Obviously, those skilled in the art may make various changes and modifications to the invention without departing from the spirit and scope of the invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A power battery cycle test method, characterized in that: The steps include: Step S1: standard discharge, comprising: placing the battery pack in a temperature box, adjusting the temperature in the temperature box to 25°C, and discharging at a current of 1C until the voltage of the battery pack reaches the lower limit of the usable voltage; Step S2: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C; Step S3: slow charging, comprising: charging the battery pack with a slow charging current until the voltage of the battery pack reaches the lower limit of the available voltage; Step S4: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C; Step S5: Discharging, including: a pulse process and a recharge process, wherein the discharging refers to: Step S51: discharging at 0.5C current for 15 minutes; Step S52: let stand for 10 seconds; Step S53: discharging at 2C current for 30s; Step S54: let stand for 10 seconds; Step S55: charging at 0.5C current for 10 seconds; Step S56: Repeat steps S51 to S55 until the voltage of the battery pack reaches the lower limit of the available voltage; Step S6: repeat steps S2 to S5 for n times, where 10≥n≥1; Step S7: fast charging, comprising: charging the battery pack with a fast charging current until the voltage of the battery pack reaches the lower limit of the available voltage; Step S8: standing still until the voltage and temperature of each single cell in the battery pack reach a stable state, and the maximum temperature of the battery pack is ≤30°C; Step S9: discharging; Step S10: repeat steps S2 to S9 for m times, where m ≥ 100; The number of cycles and the energy of each discharge are recorded, and the electrical performance of the battery pack is estimated based on the number and energy.

2. The power battery cycle testing method according to claim 1, characterized in that: The stable state means that within a minute, the change values ​​of the voltage and temperature of each single cell in the battery pack are respectively less than the first threshold and the second threshold.

3. The power battery cycle testing method according to claim 1, wherein: The battery pack is equipped with a cooling system, which is turned on and off by a controller during the cycle test.

4. The power battery cycle testing method according to claim 3, characterized in that: The controller also controls the initial temperature and flow rate of the coolant in the cooling system.

5. The power battery cycle testing method according to claim 4, characterized in that: The controller controls the cooling system to start in steps S3, S5, S7 and S9, and makes the temperature of the battery pack ≤35°C.

6. The power battery cycle testing method according to claim 3 or 5, characterized in that: The controller controls the cooling system to start in steps S2 , S4 and S8 .

7. The power battery cycle testing method according to claim 1, wherein: During the charging process of steps S3 and S7, a step-by-step charging method is used for charging.

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