An assembly line includes a conveyor belt and an energy charging system. The energy charging system includes (i) a resonator having a TX resonator disposed along the conveyor belt and a RX resonator mounted on and transported by the conveyor belt, (ii) an impedance matching network in communication with the resonator, (iii) and an energy storage device in communication with at least one of the resonator and the impedance matching network. Vmin is a minimum voltage of the energy storage device, and Vcap is a voltage across the energy storage device measured in real time. Energy is transferred from the TX resonator to the RX resonator when the Vcap is less than Vmin of the energy storage device.