Abstract: A battery charger for a nickel-cadmium cell, or the like, uses a large battery, such as an acid-lead automobile battery. Electrodes depend from the fill caps and into the electrolyte to make a plurality of potential points. Each of the cells in the large battery includes two sets of plates, with the individual plates in each set being joined at one end by a common bus bar. A terminal extends from each of these bus bars through the case of the acid-lead battery, to provide another plurality of potential points. A small battery, such as at least one nickel-cadmium cell is coupled to selected ones of the potential points so that the potential across the selected potential points equalizes with the potential of the small battery.