Auxiliary battery charger for no break power supply - is for charging individual sections to gassing point to maintain battery performance

The application is to uninterruptable power supplies for dc loads which have to operate within close limits of maximum and minimum voltage. The main rectifier and regulator (1) feeds the load (2), and also charges the battery (3). As the battery delivers no current under normal conditions, its output performance may deteriorate, for example due to high local acid concentration in a lead acid cell. To avoid this condition each battery section (3.1, 3.2,3.3) in turn is charged to the gassing point in order to give good mixing of the electrolyte. By charging one section at a time the output voltage is maintained within the limits defined for the load. The auxiliary charger (4) is typically an unregulated dc supply. It is switched (5) in turn to each battery section. Switching may be determined by a timer, by evolution of gas, or some similar means.