A Coupled Lattice Boltzmann-Finite Volume Method for the Thermal Transient Modeling of an Air-Cooled Li-Ion Battery Cell for Electric Vehicles

Due to their ability to store higher electrical energy, lithium ion batteries are the most promising candidates for electric and hybrid electric vehicles, whose market share is growing fast. Heat generation during charge and discharge processes, frequently undergone by these batteries, causes temperature increase and thermal management is indispensable to keep temperature in an appropriate level. In this paper, a coupled Lattice Boltzmann-Finite Volume model for the three-dimensional transient thermal analysis of an air-cooled Li-ion battery module is presented. As it has already been successfully used to deal with several fluid-dynamics problems, the Lattice Boltzmann method is selected for its simpler boundary condition implementation and complete parallel computing, which make this approach promising for such applications. The standard Lattice Boltzmann method, here used only for the fluid-dynamic evolution, is coupled with a Finite Volume approach for solving the energy equation and recovering the temperature field throughout the whole domain (air, aluminum and battery). This coupled approach allows having a fully reliable control of the transients in conjugate heat transfer problems without introducing any simplification on thermal capacities, as commonly required by thermal Lattice Boltzmann methods. Prismatic Li-ion cells with a layer of an aluminum heat sink are considered in the battery pack design. Heat generation and voltage variation within each single cell are calculated by using an equivalent circuit model and heat transfer principles. Results are validated against data available in literature ensuring accuracy of the proposed numerical model and showing an excellent agreement with the reference. Finally, a parametric study to evaluate the cooling performance of a battery cell by varying the discharge rate and air velocity through the channels is proposed.