A battery pack charger that includes a housing and a plurality of battery receptacles supported by the housing that are configured to receive a battery pack. The charger includes a plurality of charging circuits connected to the battery receptacles and configured to transmit power to the plurality of battery receptacles. The charger includes at least one sensor to sense available power from a power source. The charger includes a controller operable to receive a signal from the at least one sensor indicative of the available power from the power source, receive signals from the plurality of charging circuits indicative of an amount of power needed by the charging circuits to charge the battery packs, and reduce a charging power to at least one of the plurality of charging circuits when the amount of power needed by the charging circuits is greater than the available power from the power source.