The charging current is a characteristic value for charging batteries. It applies equally to chargers used to charge rechargeable batteries of mobile devices and to charging stations for electric vehicles. In general, the charging current, the charging time and the nominal capacity are directly related. The amount of charging current cannot be set arbitrarily; it depends on the charging equipment and the type of battery and is taken into account accordingly in the charging procedures.
The charging current can be used to charge batteries until they are fully charged. The charging time required for this depends on the nominal capacity of the battery. If a battery has a nominal capacity of 1,200 mAh, then a completely discharged battery could theoretically be charged with a charge current of 1.2 A in one hour or with 600 mA charge current in 2 hours. The charging current is often set in relation to the nominal capacity in coulombs (C), for example, 0.5C or C/2 is specified as the charging current. This means that the charging current for the battery is equal to half the nominal capacity. If this is 1,500 mAh, for example, then the charging current is 750 mA and the charging time is 2 hours. If the charging current is 2C, the charging current would be 3 A, and the charging time would drop to 0.5 hours.
Batteries are charged with charge current. Their state of charge is the State of Charge( SoC). When the battery is fully charged, the state of charge is 100%. If energy is removed, then the State of Charge decreases by the portion of the discharge energy shown in the Depth of Discharge( DoD). If a battery is fully charged, then the SoC value is 100%, and the DoD value is 0%, because no charge has yet been removed. If the battery is discharged, the SoC value is 0 % and the DoD value 100 %.
Depending on the battery type, they are charged with constant current, constant voltage, constant current constant voltage( CCCV) according to the IU charging method or with a pulsed charging current.