The REIMEI Li-ion Batteries after more than 12 years of Operation

Kurzfassung

The satellite "REIMEI" was launched in August 2005; this satellite is one of the first spacecraft to use Li-ion batteries. The orbit of the satellite is a low earth orbit, over 65000 charge/discharge cycles have been reached and REIMEI is still operating. We are trying to estimate the remaining useful capacity and state of health for the REIMEI Li-ion batteries. However, the estimation of remaining useful life for Li-ion cells is not trivial, since their degradation is caused by many physical and chemical processes which get accelerated depending on the working environment and operating conditions. The satellite uses 2 batteries, each battery consists of 7 cells. The cells use LiMn2O4 and graphite as the positive and negative electro-active materials, respectively. The rated capacity of each cell is 3 Ah. In this work we analyse the performance of the REIMEI batteries based on telemetry data.