Parameterization and Validation of a Distributed Coupled Electro-Thermal Model for Prismatic Cells

Abstract

The temperature distribution in a prismatic Li-ion battery cell can be described using a spatially distributed equivalent circuit electrical model coupled to a 3D thermal model. The model represents a middle ground between simple one or two state models (generally used for cylindrical cells) and complex finite element models. A lumped parameter approach for the thermal properties of the lithium-ion jelly roll is used. The battery is divided into (m × n) nodes in 2-dimensions, and each node is represented by an equivalent circuit and 3 temperatures in the through plane direction to capture the electrical and thermal dynamics respectively. The thermal model is coupled to the electrical through heat generation. The parameters of the equivalent circuit electrical model are temperature and state of charge dependent. Parameterization of the distributed resistances in the equivalent circuit model is demonstrated using lumped parameter measurements, and are a function of local temperature. The model is parameterized and validated with data collected from a 3-cell fixture which replicates pack cooling conditions. Pulsing current experiments are used for validation over a wide range of operating conditions (ambient temperature, state of charge, current amplitude and pulse width). The model is shown to match experimental results with good accuracy.