An internal power source, an accessory and an external power source is disclosed. The internal power source is adapted to be implanted in a mammal body for supplying power to an implanted medical device in the mammal body, and comprises a receiver for wirelessly receiving power from a power source external to the mammal body, the receiver comprising a coil, and a backup override system. The accessory is adapted to provide signals to the backup override system, wherein reception of said signals makes said backup override system trigger a backup function or a backup system to override one or more other functions for controlling and/or powering the medical device. The external power source is adapted to be arranged external to the mammal body and to supply power to the implanted medical device.
