Mathematical Modeling & Heat Transfer Analysis of Lithium-ion Battery Pack for Electrical Mobility

Thermal runaway is a serious safety concern in lithium-ion batteries, the type commonly used in electric vehicles (EVs). It's a cascading event where a battery's internal temperature increase triggers a chain reaction that can lead to fire and explosion. Due to internal short circuit there can be damage to the separator, a thin membrane separating the positive and negative electrodes, can cause them to come into contact, leading to a current surge and heat generation. This damage can be caused by physical impact, manufacturing defects, or degradation over time. Even there are chances of external short circuit, where in the battery's positive and negative terminals come into unintended contact with a conductive material, a large current can flow externally, causing rapid heating. Due to over usage of batteries, sometimes over charging is done in which pushing a battery beyond its safe charging voltage can cause internal damage and heat generation. A specified battery pack when connected to mechanical load for traction, such as in Electric vehicles will be recommended to operate at rate speed and rated distance, but to reach last mile connectivity sometimes over usage of battery results in over discharge, which means draining a battery below its safe minimum voltage, and it can also stress the battery and increase the risk of thermal runaway. The environmental conditions also affect the battery state and in situations where extreme heat can accelerate chemical reactions within the battery, increases the risk of thermal runaway. In the present work the authors have attempted to model a thermal runaway in a lithium-ion battery pack. A lithium ion pack with relevant energy requirement calculations are performed for electric vehicle of 100 BHP equivalent conventional IC engine and presented. Python code is used through the pybamm library module and electrochemical parameters are modelled for lithium ion cell. Keywords: Mathematical modeling, Heat transfer, Lithium-ion, Battery pack, electrical mobility, thermal runaway