A charging circuit comprises a power node electrically connectable to a power supply unit, a battery node electrically connectable to a battery, a device node electrically connected to a device load, a reversible buck-boost converter operatively intermediate the power node and the battery node, a first switch operatively intermediate the power node and the device node, a second switch operatively intermediate the battery node and the device node; and logic operatively connected to the first switch, the second switch, and the reversible buck-boost converter. The logic is configured to operate the first switch, the second switch, and the reversible buck-boost converter based on a plurality of different conditions.