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Three questions about the basic knowledge of lithium batteries

Posted on 2022-08-02

1. What is the capacity of the battery?

    The capacity of the battery is divided into the rated capacity and the actual capacity. The rated capacity of the battery refers to the design and manufacture of the battery that stipulates or guarantees that the battery should discharge the minimum amount of electricity under certain discharge conditions. Li-ion stipulates that the battery should be charged for 3 hours under the charging conditions controlled by normal temperature, constant current (1C) and constant voltage (4.2V). And the influence of temperature (so strictly speaking, the battery capacity should specify the charging and discharging conditions). Common units of capacity are: mAh, Ah=1000mAh).

2. What is the internal resistance of the battery?

    Refers to the resistance of the current flowing through the battery when the battery is working. It consists of ohmic internal resistance and polarization internal resistance. The large internal resistance of the battery will cause the battery discharge working voltage to decrease and the discharge time to be shortened. The internal resistance is mainly affected by factors such as battery material, manufacturing process, and battery structure. It is an important parameter to measure battery performance. Note: Generally, the internal resistance in the charging state is used as the standard. The internal resistance of the battery needs to be measured with a special internal resistance meter, not with the ohm gear of a multimeter.

3. What is open circuit voltage?

    It refers to the potential difference between the positive and negative electrodes of the battery when the battery is in a non-working state, that is, when there is no current flowing through the circuit. Under normal circumstances, the open circuit voltage of Li-ion is about 4.1-4.2V when fully charged, and about 3.0V after discharge. The open circuit voltage of the battery can be used to determine the state of charge of the battery.