Abstract: A rechargeable battery having a photovoltaic device and battery charging circuitry integral therewith. A rechargeable battery such as, for example, a Lithium battery, includes a current regulating circuit interposed between a photovoltaic device mounted on an outer surface of the battery and the terminals of the battery. In order to attain maximum power transfer between the photovoltaic device and the battery, the circuit includes a feed-forward feature that regulates the current flow from the photovoltaic cell to the battery in response to changes in the voltage output of the cell. When the voltage output (V) of the photovoltaic cell drops below a predetermined value, the current (I) flowing from the cell to the battery is decreased in accordance with the equation V=aI+b, where the coefficients a and b are constants having a value depending on the type of rechargeable battery employed.