Inductively coupled battery charging systems and methods are provided. Transmit circuitry can include a transmit coil operatively part of a transmit resonant circuit exhibiting resonance at a transmit resonant frequency and an unloaded Q value of at least about 20. Transmit coil can generate a magnetic field at about the transmit resonant frequency. Rechargeable battery assembly can include a receive coil configured to receive inductively coupled current, and circuitry configured to rectify the current and communicate charging power to a storage cell. Receive coil can be part of a receive resonant circuit that exhibits resonance at about the transmit resonant frequency. Transmit circuitry can be configured to regulate alternating current produced in the transmit coil based on current flowing in the transmit resonant circuit and/or maintain the magnetic field at about the transmit resonant frequency by maintaining about a ninety degree phase shift between a square wave input and output.