An external processor device is described for a hearing implant system. An external processor housing has a generally planar skin contacting surface and a central axis perpendicular to the skin contacting surface. A signal processor is located within the processor housing for developing an implant data signal. The processor housing also contains a transmitter coil for coupling the implant data signal across the skin to the implantable prosthetic system. A battery container forms an annular compartment around the central axis and contains a battery arrangement to provide electrical power to the signal processor and the transmitter coil.