Cooling Simulation of an EV Battery Pack to Support a Retrofit Project from Lead-Acid to Li-Ion Cells

Abstract

A niche of the electric vehicle market is the electric retrofit of existing vehicles. These updates replace internal combustion engines with high efficiency electric motors and high capacity Li-ion batteries. This market is dominated by mostly small and medium size enterprises that provide tailored solutions to customers. These companies seek to reduce their costs and lead times by using virtual prototyping tools and methods in the main design processes. In this context, our work defines a design methodology to support designers in the definition of cooling systems. As a test case, we analyzed the electric retrofit of a small electric car with a lead-acid battery that was updated to Li-ion technology. We focused on a simulation of the cooling of the battery using a thermal analysis based on the physical parameters of the cell and test bench results. The issue is the evaluation of the heat generated by the electrochemical reactions of lithium ion battery cells. A representative battery module was simulated following the methodological approach. The virtual prototyping analysis was divided into two levels: the thermal simulation of a single cell, and the computational fluid dynamics (CFD) analysis of a battery module composed of LiFePO4 prismatic cells. The geometric and fluid dynamic parameters were investigated with a CFD solver to study the cooling performance. A cooling system configuration was proposed and analyzed using the virtual prototyping tools.