Magnetically Coupled Battery Charging System

An inductively coupled battery charging system comprising:

• transmit circuitry comprising a transmit coil, wherein the transmit coil is operatively part of a transmit resonant circuit that exhibits resonance at a transmit resonant frequency, wherein the transmit resonant circuit exhibits an unloaded Q value of at least about 20, and wherein the transmit circuitry is configured to produce alternating current in the transmit coil to generate an alternating magnetic field at about the transmit resonant frequency;
• and
• a rechargeable battery assembly comprising a storage cell and receive circuitry, the receive circuitry comprising a receive coil operatively connected to receive control circuitry, wherein the receive coil is configured to receive inductively coupled current, wherein the receive control circuitry is configured to rectify the current and communicate charging power to the storage cell, wherein the receive coil is operatively part of a receive resonant circuit that exhibits resonance at a receive resonant frequency, wherein the receive resonant circuit exhibits an unloaded Q value of at least about 10, wherein the transmit resonant frequency and the receive resonant frequency are about equal, and wherein the transmit circuitry is configured to detect the rechargeable battery assembly by monitoring a load on the transmit coil.