The capacity testing of lithium-ion batteries in electric vehicles is generally carried out at 25 ℃ using a constant current discharge to the protective voltage. The discharge time and discharge current are multiplied to obtain the battery capacity.
The method for measuring battery capacity is the same as the method for testing the discharge performance of lithium-ion batteries, including the constant current discharge method, constant resistance discharge method, constant voltage discharge method, constant voltage and current discharge method, continuous discharge method, and intermittent discharge method. The capacity of the battery can be calculated based on the discharge time and the magnitude of the current.
1. Test battery capacity with Voltmeter and load
It is difficult to detect the capacity of the lithium-ion battery of electric vehicles accurately by only using the Voltmeter or the voltage gear of the multimeter without load to check whether the battery capacity is sufficient. When measuring voltage alone, the current consumption is minimal, so there will be no significant voltage drop inside the battery. Therefore, the displayed voltage is not low. However, if a considerable load is added, such as turning on the headlights (load current 10-15A) or honing the horn (load current 6-12A), the battery will make the lights dim and the horn hoarse, indicating insufficient battery storage.
2. Test battery capacity with Hydrometer
It is also a commonly used method. Generally, the standard specific gravity of the electrolyte for fully charged lithium-ion batteries at 20 ℃ is 1.25~1.29kg/L; If the electrolyte specific gravity of the battery is less than the above value at 20 ℃ and greater than 1.06kg/L, the battery has insufficient storage capacity and needs to be charged; If the specific gravity of the electrolyte at 20 ℃ is 1.06kg/L or less, it indicates that the battery has been completely discharged or damaged. According to this principle, the capacity of the battery can be known by measuring the specific gravity of the battery electrolyte with a Hydrometer, and the condition of the battery can also be further judged.
3. Check the battery capacity with a battery tester
To truly quickly and accurately detect the battery capacity in daily maintenance and repair, it is still necessary to use a lithium-ion battery tester. When using, connect the lithium-ion battery detector to the battery for 10-15 seconds, and maintain the voltage at 10.5-11.6V, indicating sufficient capacity and no battery malfunction; Maintaining the voltage between 9.6V and 10.5V indicates insufficient capacity and no battery failure; The voltage drops below 9.6V, indicating a serious shortage of capacity or battery failure.
The above are several methods for detecting the capacity of electric vehicle batteries. As long as you carefully follow these methods, you can detect the capacity of lithium-ion batteries in electric vehicles.
How to extend the service life of lithium-ion batteries in electric vehicles?
1. To extend the service life of lithium-ion batteries in electric vehicles, it is necessary to understand the electric vehicle and carefully read the electric vehicle manual before purchasing and using it, and pay attention to relevant matters.
2. Regularly charge lithium-ion batteries. But there is one misconception to prevent: there is no need to charge the battery every day.
3. Use a good charger. Never buy any cheap electric vehicle from a street stall. Generally, lithium-ion battery appliances for electric vehicles equipped by larger production manufacturers are better.
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