Innovative Vehicle Battery Pack Design Approach through Multiphysics Cells Simulation

This paper presents the design procedure of a vehicle battery pack, in terms of electrical and mechanical requirements with an innovative methodology to model Li-ion cells' thermo-electro-mechanical behavior. A toroidal battery pack was developed for a widespread A-segment vehicle and designed to be placed in the spare wheel compartment. A novel FEM modelling approach is studied to predict if short circuits happen in case of vehicle crash, avoiding battery pack structure over-engineering. Thus, the classical approach in which cells were treated as a rigid and non-deformable block is overcome. At the beginning, the toroidal battery pack was sized considering a mild hybrid vehicle conversion. Then, the internal modules layout was defined including also electric connection and cooling system. Subsequently, a benchmarking activity on existing FEM modelling methodologies of single cells was conducted and two approaches were identified and compared: the layer resolved approach, in which every layer composing the cell is modelled and the homogeneous approach, in which all the layers that made up the cells are modelled as an equivalent component. Considering the literature approaches, three common experimental tests on a single cell were chosen and replicated in LS-DYNA (using the two previous mentioned models) to evaluate the correlation accuracy and the computational costs. Moreover, the calibration of thermo-electro-mechanical coupling was done by defining the short circuit occurrence with an equivalent Von Mises stress threshold. Finally, the battery pack was validated according to two international standard mechanical tests through a complete full-scale simulation. Pros and cons of this novel modelling approach and its potential application on full-vehicle simulations are presented and discussed.