A method and system for battery charging. In some aspects, an electrical combination comprises a first battery having a Lithium-based chemistry, the first battery having a first nominal voltage in a nominal voltage range, a second battery having a Lithium-based chemistry, the second battery having a second nominal voltage, the second nominal voltage being different than the first nominal voltage and being outside of the nominal voltage range, and a battery charger operable to charge the first battery and the second battery. In some aspects, a method of charging a battery, a first battery having a Lithium-based chemistry, the first battery having a first nominal voltage in a first nominal voltage range, a second battery having a Lithium-based chemistry, the second battery having a second nominal voltage in a second nominal voltage range, the second nominal voltage being different than the first nominal voltage, the second nominal voltage range being different than the first nominal voltage range, a battery charger being operable to charge the first battery and the second battery, includes the acts of electrically connecting the battery charger and the first battery, charging the first battery, electrically connecting the battery charger and the second battery, and charging the second battery.