Three separator materials; nylon (NY), polypropylene (PP) and polyphenylenesulfide (PPS), were evaluated by accelerated cycle test of 35AH aerospace NiCd cells. The failure mode of cells with the NY separator is different from the other. The result of these test suggest that the NY separator will satisfy with required mission life of 1000 cycles in geosynchronous earth orbit (GEO) and 20000 cycles in low earth orbit (LEO) under the condition of controlled cell temperature at 20°C.Also, the washed NY separator was compared with the unwashed NY separator by semi-real GEO cycle. During early cycles, the washed separator cells showed a slight degradation of cell capacity as compared with the unwashed separator cells. After 1000 cycles, the washed separator cells show greater capacity degradation than the washed cells.