A generalized methodology for lithium-ion cells characterization and lumped electro-thermal modelling

Abstract

[EN] This paper deals with the experimental characterization and electro-thermal modeling of lithium-ion batteries. This aspect is of considerable importance to be able to have an understanding of the phenomena of heat generation and thermal behavior of a lithium-ion battery. Electrical parameters need to be characterized to properly estimate the electrical losses inside the battery and, thus, of the total heat generation. The testing methodology employed to do this is fully described. It highlights the dependency of each parameter on state of charge, current and temperature. Thermal parameters are calculated knowing the internal characteristics and composition of the cell and using available data from literature. A first order equivalent circuit model is used to simulate the electric behavior of the cell. Extrapolation models are used to accurately estimate capacity and resistive parameters for points outside the considered test matrix. The thermal behavior of the cell is modeled using a nodal network, assigning volume, heat capacity and heat generation to the nodes. The whole methodology shown can be adapted to any other chemistry, format, or capacity; furthermore, this methodology can be applied also in case of limited test matrix points, due to the implementation of extrapolation models for electrical parameters. Finally, a case study for the fast charging of a battery module is presented, to highlight the great potential of the model, not only for on-line estimation, but also for offline studies, being the charging operation one of the most critical from the thermal management point of view