Esults Of Deep DoD Life Cycle Tests At High Rates On 12Ah NiCd Cells

Aerospace battery performance can be a key system driver when spacecraft size and weight are critical design constraints. Nickel cadmium (NiCd) battery performance under deep depth of discharge (DOD) at relatively high rates and low earth orbit (LEO) conditions, however, is not well known. The Johns Hopkins University / Applied Physics Laboratory (JHU/APL) has conducted an accelerated lifecycle test to evaluate NiCd performance for a stressful LEO application. Ile test exposed six Gates twelve ampere hour (Ah) NiCd cells with Pellon #2536 nylon separator material to seventy percent DOD LEO cycles. Each ninety-five minute cycle began with a two part discharge apportioned between rates of C/3 and 1.8C,followed with a charge at a IC rate, and ended with a taper charge governed by a voltage - temperature (V-T) limit. The test was run under ambient conditions with the cells varying between twenty and thirty degrees Centigrade. Twenty-four hundred cycles were achieved by increasing the V-T limit as determined by the previous end of discharge (EOD) voltage. An additional six hundred cycles were produced by interspersing the deep DOD cycles with twenty percent DOD cycles.