A battery charger has at least two phases and coupled switches that are controlled using switch mode power supply (SMPS) techniques. One of the phases is part of a buck-boost circuit that includes a high side switch, which is coupled between a near end of the phase and the input, and a low side switch that is coupled between a far end of the phase and ground. The far end of the phase is also coupled to a battery, through a further high side switch. A controller signals the switches into open and closed states so that the buck-boost circuit is operated in buck mode when charging the battery at a low voltage, and in boost mode when charging the battery at a high voltage. Other embodiments are also described and claimed.