Simulation Based Approach to Optimize Electric Vehicle Battery Thermal System

The performance and longevity of Li-ion batteries in electric vehicles are significantly influenced by the cell temperature. Hence, efficient thermal management techniques are essential for battery packs. Simulation based optimization approaches can enhance these techniques during early product development and life cycle. In this work, a method to optimize the battery thermal system comprising of cooling plate and external insulation is described. The first part is to optimize the cell heat extraction by the cooling plate. The heat transfer coefficient of the coolant is a parameter which can indicate the thermal efficiency of a cooling plate. At the same time, it's important to keep the coolant pressure drop within a reasonable limit. A 1D simulation methodology is described to optimize the cooling channel height based on pressure drop and heat transfer coefficient targets. This methodology is based on empirical correlations and multi-objective pareto optimization. The advantage of this approach is the ability to simulate hundreds of design experiments quickly to optimize the design without performing CAD iteration loops. The next part is to optimize the heat loss to ambient. Excess heat loss, especially in cold conditions, lowers system efficiency due to increased pre-heating needs. The solution for this is the addition of right insulation materials at optimum thickness on minimum surfaces. Here, battery packs are modelled as 1D lumped thermal mass model with insulation material, whose dimensions and properties are parametrized. First, the sensitivity of insulation on each surface to heat transfer has been evaluated to choose the number of insulation surfaces. In the second stage insulation thermal conductivity & thickness is optimized. This approach enables designers to select the right material with the right thickness for each location.