Thermal State of Charge Estimation in Phase Change Composites for Passively Cooled Lithium-Ion Battery Packs

This paper presents an integrated approach, where a Li-ion battery pack is equipped with a passive thermal management system and an on-board intelligent battery management system. The proposed technique estimates the melt fraction of the phase change composite (PCC) material and its remaining thermal mass, which can be a decisive indicator of how long the battery can maintain safe operation. Furthermore, an on-board temperature and melt fraction map of the battery pack can be generated, which will be valuable in case of asymmetrical designs or modes of operation. The core of this paper is based on monitoring the temperature of the entire test pack to estimate the temperatures on all the cells within the pack. This enables the estimation of thermal state of charge of the PCC in all sections of the pack to accurately monitor and ensure safe operation.