Electro-thermal modeling of Li-ion batteries

Li-ion batteries play an important role as energy storage systems in automotive applications like hybrid electric vehicles. For an efficient use in such applications high demands are made on batteries regarding their operational conditions. Because of the heat generation due to high charges applied in this field, an active cooling of the cells is required. The objective of this paper is to present a model, which can be used in the design process of battery packs, starting with the simulation of battery bahaviour to the point of model-based energy management controllers and cooling strategies. The model represents the electrical behaviour, i.e. the progression of the terminal voltage and the generated thermal dissipation loss under defined operational conditions, and the thermal bahaviour, i.e. the temperature distribution of the cell. The thermal model includes the flow of the coolant, which is calculated using computational fluid dynamics. Furthermore interactions due to the temperature-dependency of the electric model are taken into account. Parameter estimation for both parts of the model is done separately in a two-stage algorithm by fitting the model output to experimental data.