Abstract

Thermal performance of lithium-ion cells plays a crucial role in terms of efficiency, safety, and residual lifetime management of many electrical devices. In this paper, a thermal management strategy for cooling-down 26650 LiCoO2 lithium-ion battery cells based on modular packaging is analyzed. Battery modules with different number of cells were arranged and experimentally discharged under natural convection followed by a cooling-down process by air forced convection until cells reached the ambient temperature. Surface temperature of each cell and ambient temperature were recorded and analyzed using a fractal time thermal model. Results show that modular packaging improves the thermal behavior of cells. As the modules became larger, the thermal time constant of the system significantly increased, i.e., heat transfer coefficient of module decreased and the furthest cells from the fans interchanged less heat to surrounding air. In addition, modular packaging improves the energy efficiency of the cooling system since it is more efficient to cool several small modules than cooling a larger one.