Abstract

Driven by the development of electric vehicles, the need for simulation models of batteries on cell, module and pack level has increased tremendously. While models for thermal management during normal use of batteries are already at a very satisfactory level, the misuse cases of batteries as well as the associated thermal runaway remain a challenging field. This presentation will cover the multi physical model building process using LS-DYNA as a solver. Herein, all necessary assumptions and model building techniques will be discussed to setup and calibrate a thermo-mechanically coupled model that is driven by a battery model, which is able to capture normal charge and discharge use cases, short circuiting and thermal runaway. Herein, the focus is not so much on the mechanical model as the application in mind investigates a controlled heating of one cell in a battery pack. Following this, a thermal model will be calibrated using anisotropic thermal conductivity to account for the layered structure in battery cells and isotropic thermal conductivity for the housing of the battery module and pack. Moreover, a thermal contact needs to be defined which accounts for heat transfer via direct contact as well as radiation. The battery model is based on a so-called homogenized Randle circuit approach, where the parameters for the model will be calibrated using several charge and discharge experiments. On top of the battery model sits a short circuit model which can be triggered by either temperature or mechanical deformation. The model for thermal runaway will be included in homogenized fashion using an energy release rate function that is triggered when a critical temperature is reached and calibrated using autoclave tests in a controlled burn environment. Moreover, two CFD approaches will be presented to assess the structural damage in a battery module during thermal runaway as well as the long term heating power of the released gases on neighboring cells.