Lithium-ion batteries for geosynchronous satellites. Qualification test results of the STENTOR battery

SAFT has been engaged in the development and qualification of lithium-ion cells and batteries for space applications since 1996. This paper presents the results obtained during qualification tests on the first battery built for the STENTOR Satellite. The STENTOR satellite is powered by lithium-ion cells only, with two 45 V-80 Ah battery packs, made from cylindrical shaped 40 Ah lithium-ion cells, and including the electronics to monitor cells voltages and balance the cell to cell capacities. Each battery pack weights less than 37 kg. The required capacity is achieved by connecting two 40 Ah cells in parallel prior to connecting it in series. Then 11 of these group of two cells are series connected. The battery includes an automatic by-pass system to prevent any type of cell failure. The two electronics are cross strapped to ensure that the two battery packs have no single point failure. The first complete battery, built in 1999, was submitted for qualification test, which comprises: capacity test; hot and cold temperatures; thermal vacuum tests; vibration/shock tests; and EMC tests. The paper gives a summary of the development results, together with details and analysis of the qualification tests performed.