How to Test Lithium Battery’s Capacity

Capacity is the core parameter of lithium battery. Lithium battery manufacturers generally have battery cell capacity testing equipment for battery testing to ensure the quality of shipped products.

Here take 1000mah lithium battery as an example.

First of all, we should understand several voltage values of lithium battery theoretically:

1. Charging termination voltage: it is also the no-load voltage, that is, the highest voltage when it is not working, which is generally 4.2V.

2. Working / nominal voltage: it is also the load voltage, and the voltage during normal operation is generally 3.7V.

3. Discharge termination voltage: that is, the voltage at which the battery cannot work. There are different designs of 3V and 2.75V.

Start the test, first charging the battery with a battery cell grading machine, and the full charged voltage is 4.2V, and then use the multimeter as the constant current load, with 0.2C (i.e. 1000 × 0.2=200ma) discharge, set the discharge voltage of the multimeter to 3V. If the discharge time reaches 5 hours, it means that the battery is qualified. The current lithium battery can generally be discharged to 2.75V, and the discharge depth is 80% as before, when 3V is the termination voltage, but it can be put into 8 hours, indicating that the power of lithium battery has been improved.

The above so-called qualified and unqualified are relative to the nominal capacity. And nominal capacity = discharge current × discharge time. If the above discharge time is not enough, it means that the capacity marked on the lithium battery is not enough 1000mah.

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