An energy storage unit for a motor vehicle battery is provided, having an energy store, particularly configured as a battery cell module, for storing and delivering electric power. A measuring device measures electrical properties of the energy store. An evaluation unit, connected to the measuring device, ascertains the operational status of the energy store from the measurement results of the measuring device. An indicator unit is connected to the evaluation unit for depicting the operational status of the energy store. By ascertaining and depicting the operational status and not just the state of charge of the energy store, it is possible to dispense with separate complex measurements when fitting the energy store, so that an energy storage unit can be checked quickly and efficiently when fitted into a motor vehicle.