Power supply device with battery monitoring and battery monitoring method

The device (100') has a modulator that is electrically connected to a power line connection and comprises a signal modulating unit such that a signal to the power line connection is modulated. The determined information in the signal is coded by an electronic measuring system (107,107',107",107"',107-IV,107-V), and transmitted above the power line connection. A demodulator has a receiver (105,105') that receives the modulated signal over the energy lines (115,115') and decodes the derived information of the electronic measuring system. An independent claim is included for a method for operating a battery control device.