the disclosure relates to a method for transferring batteries to a discharged state , a battery system , an inverter , a system for generating an ac voltage , a charging current source and a motor vehicle . the battery system includes a controllable inverter having parallel current branches and having series - connected power switches that are switchable by external control of the controllable inverter . the battery system further includes a controllable charging and disconnecting device having an interrupted current path and having a charging current source between the battery and the controllable inverter .