Abstract: A system for obtaining a variable voltage output from an assembly of battery banks and switches. The battery banks are composed of a plurality of individual cells that are connected in series so that the first bank is composed of one cell, and each succeeding bank has double the number of cells as the previous bank. A corresponding plurality of mechanical or solid state switches are interconnected with the series of batteries so that output voltage may be varied in increments equal to the voltage of one cell. The output voltage is varied from zero to a maximum corresponding to the sum of the voltages of all the battery-banks in series. The number of steps between the minimum and the maximum is equal to the number of cells in all the battery-banks.