Electric Vehicle Lithium-ion Battery Capacity Testing Method
1. Using a voltmeter with a load to test battery capacity.
Testing the capacity of an electric vehicle's lithium-ion battery using only a voltmeter or multimeter in voltage mode without a load is difficult to be accurate. When measuring voltage alone, very little current is consumed, so there isn't a large voltage drop inside the battery, indicating the voltage might not be low. However, if a substantial load is applied, such as turning on the headlights (10-15A load current) or honking the horn (6-12A load current), the battery will dim the lights and muffle the horn, indicating insufficient charge.
2. Use a hydrometer to test the battery capacity.
This is also a commonly used method. Generally, the standard specific gravity of the electrolyte in a fully charged lithium-ion battery at 20°C is 1.25–1.29 kg/L. If the specific gravity of the electrolyte at 20°C is less than this value but greater than 1.06 kg/L, the battery's charge is insufficient and it needs to be recharged. If the specific gravity of the electrolyte at 20°C is 1.06 kg/L or less, it indicates that the battery is completely discharged or damaged. Based on this principle, measuring the specific gravity of the battery electrolyte with a hydrometer can reveal the battery's capacity and further assess its condition.
3. Use a battery tester to check the battery capacity.
For routine maintenance and repair, the most effective way to quickly and accurately determine battery capacity is to use a lithium-ion battery tester. When using the tester, connect it to the battery for 10-15 seconds. If the voltage remains between 10.5-11.6V, the capacity is sufficient and the battery is functioning correctly. If the voltage remains between 9.6V-10.5V, the capacity is insufficient, but the battery is still functioning correctly. If the voltage drops below 9.6V, the capacity is severely insufficient or the battery is faulty.
