Thermal design of a battery pack for Hybrid Electric Vehicle application

Electric Vehicles (EVs) offer a promising solution to address the global energy crisis and environmental challenges associated with transportation. Currently, lithium-ion (Li-ion) batteries have gained widespread preference as the primary energy source for EVs due to their numerous advantages, including superior power density. It is imperative to acknowledge that the performance and safety of Li-ion batteries are intricately linked to their operating temperature, emphasizing the need for efficient thermal management systems. From the numerical simulation point of view, the main problem consists in conducting transient thermal analysis in a 3D Computational Fluid Dynamics (CFD) environment, since it is both time and computationally intensive. Specifically, simulating an entire battery pack can take several weeks, even when run on a dedicated server. This thesis undertakes an initial benchmarking analysis, comparing and analysing various aspects of battery packs used in four different actual passenger car vehicles. Subsequently, a design part is considered. Starting by the requirements of an Electrical Machine (EM), a proper battery cell selection and arrangement has been performed to realize a battery pack. Following this, the fluid domain for a cooling plate (indirect cooling) has been designed and simulated, through Computational Fluid Dynamics (CFD) analysis, considering different fluid flow rates. In addition, a thermal analysis through the development of a comprehensive single-cell battery behaviour model using MATLAB/Simulink, has been developed. This model integrates the Equivalent Circuit Model (ECM), which characterizes the electrical behaviour of the battery cell, with the thermal balance equation. The objective of this thesis is to investigate the thermal design of a battery pack for Hybrid Electric Vehicle (HEV) application, by exploring the thermal dynamics of the cells in response to varying fluid flow rates in a cooling plate under two distinct operating conditions: complete discharge at peak C-rate and a charge-discharge cycle.