An external power head is energized by a motor causing movement of an element that produces a varying magnetic field, thereby inducing power in an implanted receiver coil within a patient's body. The external power head includes either one or more moving permanent magnets, or one or more moving elements that vary the magnetic flux coupled to the implanted receiver coil. As a result of the varying magnetic field experienced by the implanted receiver coil, an electric current flows from the implanted receiver coil to energize an implanted medical device.