Abstract: A method is described wherein DC power is converted into battery charging power by means of an inductor carrying a current which is controlled by a power controller during an adjustable part of a pulse width period. The pulse width period is made adjustable in order to influence the power consumption of the controller which consumes a substantial amount of the total power consumed for controlled DC-DC conversion. Several additional features are provided to improve the efficiency and to further reduce the power consumed by both the converter and the power controller, which provides new uses for a variety of products and appliances having solar cells, such as road studs.