An example receiver device to be wirelessly charged in motion includes a power receiver to receive a power beam to charge a power supply and a modulating reflector. The modulating reflector is to reflect a portion of the power beam as a reflected signal, modulate the reflected signal, and vary a direction of the reflected signal to scan an area for an example power beam transmitter device. The power beam transmitter device is to track motion of the receiver device based on modulation of the reflected signal and to cooperate with other power beam transmitter devices to prioritize distribution of power among a plurality of receiver devices. An example system for wireless charging of devices in motion includes a plurality of power beam transmitter devices to coordinate transmission of power beams to a receiver device based on the motion of the receiver device.