A hearing aid system according to some examples includes a hearing aid which includes a microphone, amplifier, speaker, and a telecoil. In some examples, the hearing aid may include a battery or a capacitor for storing power wirelessly received from a distance separated wireless power transfer unit. The telecoil may be configured to receive audio signals and couple the audio signals to audio processing circuitry of the hearing aid. The telecoil may be further configured to receive power signals from the base unit and couple the power signals to power supply circuitry of the hearing aid, for example for charging the battery of the hearing aid. Examples of transmitter and receiver coils, and of distance and orientation optimization are described. Examples of wireless charging systems that may be used with hearing aids or other medical assistance devices are described.