The Thermal Management of Li-ion Battery Packs

To address the challenge of cooling multiple battery pouch cells, Fiat's research team does not manufacture the individual lithium-ion battery cells but combines up to 100 of them into battery packs. They use COMSOL Multiphysics to study the surface distribution of heat and prefer convection air cooling. Their model divides each surface of the pouch cell into nine areas, corresponding to thermocouples on the cell itself. This allows them to examine the temperature distribution at various charge/discharge rates and verify the model's consistency with reality using thermocouples and infrared heat cameras. This approach provides invaluable information that cannot be achieved through other means due to the difficulty of embedding thermocouples in battery pouches. With the knowledge gained from the model, Fiat has been able to reduce the physical channels between the cells, cutting down on space and weight. This makes it easier to insert the battery pack into a larger variety of vehicles. Additionally, they determined that a less powerful fan was required, reducing costs. The model also helped cut design time by 70%, from 1,000 hours to roughly 300 hours. Future projects will look at extreme conditions, such as temperatures below freezing, leveraging the Joule heating effect and innovative design to solve charging difficulties in these conditions.