Performances of Saft Lithium-Ion Cells in LEO Cycling

Abstract

Based on good LEO lifetime tests results, Saft proposes currently VES16 Lithium-ion for 12 years mission in Low Earth Orbit (LEO) up to 30%DoD or more within a temperature range from +10°C to +30°C. The first flight experimentation started at the end of 2015, confirming its ability to withstand the environmental stresses induced by a space launch and the in-flight constraints generated by a LEO mission. The upcoming launches scheduled from 2016 will significantly increase the flight heritage of this cell. From the beginning of VES16 Lithium-ion cell development, a wide lifetime tests program has been implemented in order to evaluate the different degradation modes due to the conditions applied in LEO cycling, as presented in Table 1. This program has allowed assessing the influence of different parameters such as EOCV (End Of Charge Voltage), DoD (Depth of Discharge), charge current and temperature. New MP176065 XTD Lithium-ion cell, developed & qualified by Saft, with an operating range extended from −40°C to +85°C, has already been selected for EXOMARS Rover mission. Promising results in accelerated LEO cycling conditions at 30%DOD has been observed and compared to VES16 lithium-ion cell results. Manufactured on a mass production industrial line, this cell is well suited for low cost missions (eg. Mega Constellations…). The article will thus present the whole LEO cycling results available for the two cells, and will provide afterwards the correlation status of Saft Li-ion Model (SLIM) with all the experimental data acquired.

Keywords

• DOD: Depth of Discharge
• OCV: Open Circuit Voltage
• EOCV: End Of Charge Voltage
• EODV: End Of Discharge Voltage
• GEO: Geosynchronous Orbit
• IR: Internal Resistance
• LEO: Low Earth Orbit
• MEO: Medium Earth Orbit
• SLIM: Saft Li-Ion Model
• SoC: State of Charge