Galileo Probe lithium-sulfur dioxide cell life testing

Several hundred D-sized, Li/SO/sub 2/ battery cells have been in a carefully controlled quiescent storage test for up to 14 years, starting at Honeywell but completing at the NASA Ames Research Center, in support of the Atmospheric Probe portion of the Galileo Mission to the planet Jupiter. This population of cells includes similar samples from 8 different manufacturing lots; the earliest from October 1981, the latest from October 1988. The baseline samples have been divided among several storage chambers, each having its own constant temperature, respectively set between 0/spl deg/C to 40/spl deg/C. Noninvasive measurements have been made repeatedly of open circuit voltage and internal resistance (at 1000 Hz). At intervals, a small portion of the cells has been removed from storage and fully discharged under repetitive conditions, thus assessing any storage related loss of discharge capacity. The results show that for storage up to 20/spl deg/C the cells have excellent stability. Above 20/spl deg/C noticeable degradation occurs.