What is the battery capacity

Battery capacity

The battery capacity is the energy that a rechargeable battery can absorb and release again when needed. The battery capacity is a characteristic value for electric vehicles, for smartphones and other battery-operated mobile devices.

In the case of electric vehicles, the battery capacity determines the distance that can be covered and is specified in kilowatt hours (kWh). For smartphones and other mobile devices, the battery capacity represents the operating time and is specified in ampere-hours (Ah).

With regard to electric vehicles, the battery capacity can be used to infer the performance of the vehicle. A Tesla with a battery capacity of 100 kWh is assumed as an example. 100 kW correspond to 136 hp. So this vehicle could get 136 hp for an hour, or 68 hp over two hours, or 34 hp over four hours.

The battery capacities indicated on the batteries are the nominal capacity, which expresses the current capacity. The specified value in ampere-hours (Ah) indicates how much discharge current can be drawn over a certain period of time until the end-of-discharge voltage is reached. The discharge time is the time between the start of the discharge and the reaching of the discharge voltage. When the discharge limit is reached, no further discharge current can be drawn from the battery. For example, if a battery has a nominal capacity of 5 kAh, it can supply a current of 5 kA for one hour or a current of 10 A for 500 hours.

The usable battery capacity, the operating capacity, differs from the nominal capacity because this decreases with the number of charging cycles. The battery capacity is temperature-dependent and increases with higher temperatures, since the charge carriers diffuse faster. The operating capacity is the battery capacity that is available to the user for operation. It is always less than the nominal capacity because it is reduced by aging processes.