Thermal Management of Batteries in Advanced Vehicles Using Phase-Change Materials

Hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs) are promising technologies to help reduce the amount of petroleum consumed for transportation. In both HEVs and PHEVs, the battery pack is a key component to enabling their fuel savings potential. The battery is also one of the most expensive components in the vehicle. One of the most signifcant factors impacting both the performance and life of a battery is temperature. In particular, operating a battery at elevated temperatures reduces its life. It is therefore important to design and implement effective battery thermal management systems. This paper analyzes the suitability of phase-change material (PCM) for battery thermal management in HEV and PHEV systems. A prototype PCM/graphite matrix module (that was not fully optimized for HEV applications) was evaluated experimentally under geometric and vehicle-simulation-based drive cycles. The results were used to validate a thermal model. The model was then used to explore the benefts and limitations of PCM thermal management. This study suggests that PCM can provide a peak-temperature-limiting beneft in vehicle applications, but the overall battery thermal management solution must rely on active cooling or on limiting the battery's power output (or both) to avoid high temperatures during continuous cycling. Ultimately, vehicle designers will need to weigh the potential increase in mass and cost associated with adding PCM to the thermal management system against the anticipated benefts: a smaller active cooling system, less need to limit battery power output in high-temperature conditions, and/or potentially reduced exposure to momentary or localized high cell temperatures.