Method and apparatus for increasing the safety in use of battery systems

The invention relates to a method and apparatus for increasing the safety in use of battery systems with a safety device, said safety device for safe operation of the battery system is suitable, depending on the spatial variation of at least one location of the surface (O) of the safety device a wherein the change in at least one location of the surface (O) of the safety device by affecting or interrupting a sample signal that is transmitted from a transmitter (S) to a receiver (e), it is determined signal, in particular a warning signal is generated.