Disclosed embodiments include systems, vehicles, and methods for determining a quantity of energy expendable in charging a towed vehicle while it is towed. In an illustrative embodiment, a computing system transportable aboard at least one of a towing vehicle and a towed vehicle includes computer-readable media storing computer-executable instructions configured to identify a quantity of charging energy to be supplied to at least one power cell of the towed vehicle by at least one rotating electromagnetic device of the towed vehicle generating and supplying electrical power to charge the at least one power cell of the towed vehicle while the towed vehicle is towed by the towing vehicle. The computer-executable instructions are also configured to determine a quantity of towing energy expendable by the towing vehicle in towing the towed vehicle to provide the quantity of charging energy to the at least one power cell of the towed vehicle.