The battery charger is modular and reconfigurable. It includes charging modular power stages that are configured to receive an alternating current (AC) input and provide a direct current (DC) output for charging a battery. These modular power stages include an inverter coupled to a rectifier circuit that outputs a battery charging current. The modular power stages can also each include a current mode controller coupled to the output of the rectifier circuit and configured to provide a current control signal for the modular power stage, a voltage mode controller coupled to the output of the rectifier circuit and configured to provide a voltage control signal for the modular power stage, and a droop sharing control and configured to ensure current sharing between a plurality of modular power stages under constant voltage operation. A system controller is configured to interface with the modular power stages.