Abstract: A method of charging a battery system of an electrically powered aircraft that is at a location on the ground. The method moves an Aircraft Charging Unit (ACU) to a position proximate to the location, the ACU having a set of storage batteries, a charge controller, and a connection system. The method further couples the set of storage batteries to the battery system through the connection system of the ACU and causes transfer of energy from the set of storage batteries to the battery system under control of the charge controller. The method then decouples the set of storage batteries from the battery system of the aircraft.