Improved charging methods for nickel-cadmium batteries used in satellites

Satellite power system designers have known for several years that charging methods need to be improved to increase life and reduce weight of nickel-cadmium batteries. Although considerable work has been done on battery designs and charging methods to improve performance, in present long-life systems only about 25-percent of the battery energy can be used during a satellite orbit. The Chrysler Corporation Space Division (CCSD) has evolved two improved charging methods that will improve life and/or energy capability per orbit. These benefits result from limiting cell state-of-charge to less than 100-percent, and from cell electrolyte quantity increase made possible by limiting the charge level. This paper describes the state-of-the-art and pertinent prior work on batteries and charging methods, concepts evolved by CCSD that will provide improved performance, benefits to be derived from the improved methods, systems required for implementation of the methods, and the development and test program planned by CCSD.