Analysis of the thermal design of a COTS-based modular battery system for satellites by thermal vacuum testing

Abstract The qualification of components for satellite applications is a costly process due to the extreme conditions that must be endured in space. Therefore, space market access of battery technology innovations is often inhibited. However, modern battery technologies offer great advantages for satellite applications. In this work, a commercial off-the-shelf (COTS) based and modular lithium-ion battery system for satellites in Low Earth Orbit (LEO) is presented. A comparative analysis to evaluate system parameters and functionality of the proposed battery system and literature data is performed. A thermal vacuum test campaign is carried out to investigate the behaviour under LEO relevant conditions and to achieve qualification of the system performance according to the ECSS (European Cooperation for Space Standardization) standard. The tested system consists of two modules with 28 V nominal voltage and eight battery cells each. Experiments were conducted inside a vacuum chamber. The battery system was charged and discharged in temperatures from 0 °C to 45 °C in a high-vacuum for three weeks. The influence of the battery management electronics, the behaviour of the cells and the heating were analyzed. The cell temperatures stayed in the operating limit during 3.5 A and 10 A cycling. The battery system, however, exceeded the cell’s upper operating limit with a 40 °C baseplate and 3.5 A charging. Despite the dense system architecture with electronics between the cells the battery system can safely deliver power in a broad temperature range. Further investigations regarding safety and failure modes are necessary, along with advancements on software and state estimation algorithms.