Capacity tests of lithium/sulfur dioxide battery cells under flight conditions

There is concern that long term, low drain discharges imposed on aerospace lithium/sulfur dioxide (Li/SO2) batteries would result in degraded battery capacity. Spacecraft now under development will use two configurations of Li/SO2 batteries fabricated from a common cell design. A group of high rate LiSO2 cells that were identical to those in flight batteries were tested according to projected load profiles. Tests were designed to evaluate the effects of drain rate, time, and temperature. Results indicated that cell capacity degradation occurred at elevated temperatures under long term, low rate discharges; periodic high rate pulsing appeared to mitigate the degradation. Depleted cells were observed to lose voltage and swell upon open circuit stand. Results from these tests are used to predict remaining battery capacity during orbital operations.