A battery charging apparatus having a plurality of charging units connected in series. A charging unit has a series switch connected in series with a rechargeable battery, and a parallel switch connected in parallel with the series connected rechargeable battery and series switch. A charging control section controls charging of a rechargeable battery by switching the series switch and parallel switch ON and OFF. The charging control section changes the duty factor for switching series switches and parallel switches ON and OFF, switches a charging unit between a charging mode and a cut-off mode at a prescribed duty factor, and controls rechargeable battery charging currents to charge a plurality of batteries.