Battery Simulation Tool for Worst Case Analysis and Mission Evaluations

Abstract

Saft recently designed, developed and qualified in the frame of Research and Development contract (GSTP-5) with the European Space Agency (ESA) three new VES16 batteries: 8S4P (4 parallel strings of 8 cells in series), 10S5P, 10S16P [ 1 ]. In order to guarantee the cells balancing (to avoid cell overcharge or over discharge during battery charge/discharge cycles), Saft introduced in parallel of each cell a simple electronic circuit called the Simplified Balancing System (SBS), which absorbs some current when a cell is close to its end of charge voltage.The complete batteries (cells and SBS) were analysed with a proper Worst Case Analysis (WCA) to demonstrate the battery performance at the EOL of the targeted missions, including all possible effects that can influence its behaviour (cells and SBS components initial tolerances, radiation degradations, ageing and temperature effects).Saft performed this analysis in PSpice and developed VES16 cell model and SBS models to run Monte Carlo Analysis (MCA).The first part of this paper presents the PSpice models including their respective variable parameters at SBS and cell level. Then the second part of the paper introduces to the reader the model parameters that were chosen and identified to perform Monte Carlo Analysis simulations. The third part reflects some MCA results for a VES16 battery module. Finally the reader will see some other simulations that were performed by re-using the battery model for an another Saft battery cell type (MP XTD) for a specific space application, at high temperature.