Abstract: A method and system for equalizing the voltage of batteries in a battery string to a desired voltage. An equal string current is drawn from the batteries of the battery string and redistributed as a plurality of secondary currents to each battery depending upon the comparative voltage of the individual batteries. A larger secondary current is provided to batteries having a low voltage and a smaller secondary current is provided to batteries having a high voltage. A transformer is provided electrically connected to the battery string having an input winding connected to the battery string such that it receives an equal string current from each battery. The transformer has a plurality of output windings having an equal turn ratio, each output winding in parallel with a battery of the battery string, to provide a secondary charging current to a battery in the battery string.