This article presents a high gain (24:1 V) high current (500A) dc-dc converter. One major advantage is the high efficiency measured, higher than 90% for 500A, higher than 95% for 200A, with a peak efficiency of 97.1%. Another major advantage is that the transformer is built using standard 3oz PCB, which facilitates manufacturability and repeatability at a reduced cost. The prototype is built stacking two 12:1V modules, connecting primary sides in series and output sides in parallel with intrinsic voltage balance in the primary stack and intrinsic current sharing in the output capacitors. Stacking four modules to implement 48:1V is straight forward, maintaining the same efficiency.