Abstract: Heat exchanger that are also outer turns of secondary windings of a transformer for use in a charge port of battery charging apparatus. The outer turns may have any shape or thickness, may be air or liquid cooled, or may be vapor changers (heat pipes). Other turns of the secondary windings cannot be used in this manner because they cause excessive energy dissipation, due to proximity losses. When used to a liquid cooled turn, the present invention comprises porting liquid coolant from a cooling system including a pump, a compact heat exchanger, and a fan through the outer windings. Heat dissipation from the secondary windings of the transformer is efficiently removed by providing an internal coolant flow passage or passages formed or integrated at the center of the outer windings comprising the heat exchangers. The internal passages may be configured in several ways. One approach is to construct thin, flat, self-contained flexible coolant bladders made of metal, such as copper.