A wireless power receiver configured to control an electrical connection between a capture resonator of a wireless power transfer system and an electrical load, such as a battery pack or electric motor. The circuitry of the wireless power receiver is powered directly by the power output from the capture resonator, automatically powering up the wireless power receiver as soon as the capture resonator begins producing power. The wireless power receiver 16 does not require stand-by power provided by an external source, such as a vehicle battery. Since the wireless power receiver does not require power from an external source, it can initiate charging of a vehicle battery even if the state of charge of the battery in the vehicle is too low to operate the controller.