A Lithium-Ion Battery Electro-Thermal Model of Parallellized Cells

Abstract

Often groups of cells in parallel are assumed to behave as one single larger unit, with homogeneous properties. Although this assumption may seem correct , it is partly false because it neglects the impact of cell to cell current variations and the self balancing currents on pack characteristics. Modeling small cells into one larger unit hinders the possibility of studying the effects of internal resistance or state-of- charge variations between cells, on current distribution and heat generation. A better understanding of the subtle interactions that usually goes unwhitnessed inside a pack is necessary to design better battery systems. This article presents a simple electro-thermal battery model based on experimental data of electrical and thermal properties of single cells., useful for design purposes or reliability assesment. The model integrates state-of -the-art cell submodels, linked together via thermal and electrical networks. Model parameters such as the entropic coefficient, internal resistance correction and open circuit voltage are interpolated using experimental lookup tables. Simulation results of a full discharge, a full recharge and an interrupted discharge are presented, as examples.