Hermetically-Sealed Nickel-Cadmium and Silver-Cadmium Storage Batteries

The galvanic battery is the most highly developed means of storing electrical energy today. In satellite and space-vehicle applications where auxiliary electrical power is required for extended periods of time, it has been found that the most feasible power supply currently available consists of silicon solar cells used in conjunction with sealed nickel-cadmium storage batteries. They are capable of thousands of repeated cycles and have an energy output of about 12 watt-hours per pound. Sealed silver-cadmium cells are of interest because of their higher output, 24 watt-hours per pound, but they are not as far developed, nor do they as yet have the cycle life of nickel-cadmium cells. In the development of hermetically-sealed nickel-cadmium batteries, the following areas have received considerable attention: 1) Hermetic seal, 2) Continuous overcharge capability and low internal cell pressure, 3) Separator, and 4) Cycle life. In the development of hermetically-sealed silver-cadmium cells, four technical problems have received considerable attention: 1) Separator, 2) Improved silver electrode capable of delivering energy at the Ag
^+II
potential, 3) Continuous overcharge capability, and 4) Cycle life. Although other direct-energy conversion systems appear to be promising and are being intensively developed, it is expected that the nickel-cadmium and silver-cadmium storage batteries will continue to be of importance for many years to come.