This paper was produced for the 2019 NAFEMS World Congress in Quebec Canada
The battery pack is one of the core components in an electric vehicle. There are many publications that describe battery pack analysis in various aspects, such as safety and thermal management. However, there are few papers that describe how to model battery cells at the battery pack level and the assembly level. The size of the battery pack model becomes very large when a detailed jelly roll model is used.
In this study, the cylindrical type of battery cell termed a “jelly roll” (so called due to its similarity in appearance to the cross-section to a Swiss roll cake) is used at the module and pack level. The battery cell model consists of the battery skin and core (the jelly roll), while detailed components such as the PTC (Positive Thermal Coefficient) device, disk vent, and CID (Charge Interrupt Device) are ignored. Since a detailed layer model of the jelly roll requires a very large finite element model for structural analysis, a homogenized model is commonly used for the jelly roll model to reduce model size. However, even if a homogenized jelly roll model is used, the assembly level model, such as at pack level, also has a very large size of finite elements, since there may be several thousand battery cells in a battery pack. The goal of this study is to develop a reduced model of a battery cell for structural analysis which also can be used at the assembly level.
Two different reduced cell models - substructure and connector - are considered, but only the connector model is tested at the module and pack level due to better performance. The module models with reference battery cell and reduced battery cell are tested and compared through modal, fatigue, and drop analyses. With the original reference battery cell model, the pack level model is not useful in practice due to the large size of the model. Hence, the pack level model is analyzed with the reduced battery cell model for crash and fatigue analysis. Finally, several structural analyses at the full vehicle level are presented with the developed reduced battery cell model.