Systems and methods for modular charging of vehicles are described. For example, a method may include connecting a vehicle to a charger using a charging plug interface that includes a first pair of conductors connected to alternating current terminals of an on-board alternating current-to-direct current converter of the vehicle and a second pair of conductors connected to terminals of a battery of the vehicle; and charging the battery of the vehicle via direct current flowing through the second pair of conductors concurrent with charging of the battery via alternating current flowing through the first pair of conductors to power the on-board alternating current to direct current converter.