Experimental Investigation on Phase Change Materials for Thermal Management of Lithium-ion Battery Packs

Most batteries generate a significant amount of heat during charge or discharge, which has to be dissipated by adequate cooling, as the temperature of the battery is a crucial parameter for the battery performance. An ideal battery thermal management system (BTMS) should be able to maintain a uniform temperature among all battery cells within the entire battery pack. A passive BTMS can compensate for the temperature deviations and maintain temperature uniformity in the battery pack without the use of active cooling components. The aim of this work is to investigate thermal management by a phase change material (PCM) for their feasibility and effectiveness for electric vehicle (EV) battery modules. In this type of latent heat storage, a PCM is melted by internally generated heat, which is released again during solidification on cooling. This novel form of a thermal management system could achieve the advantages of a compact, lightweight and energy-efficient system. Therefore, this work focuses on the implementation of such materials in a battery pack. After comprehensive market research, suitable PCMs that meet the requirements were identified and we studied experimentally these PCMs in a dedicated set-up. Detailed solidification and melting processes were examined and new measured PCM data is reported. During the experiments, specially developed test setups were used to check datasheets and to clarify open questions. A system of single battery cells was designed to provide the PCM with the best possible geometric spaces within the battery module. In order to certifying the thermal behaviour of battery systems with passive PCM cooling, Computational Fluid Dynamic (CFD) models of batteries and surrounding thermal mass have been developed and could confirm the previous assumptions and calculations.