The storage elements in an electric vehicle (EV) remain a key challenge to wide-scale, successful deployment of EVs that are appealing to customers and are adequately functional (e.g. in terms of range and drivability). State-of-the-art electric storage systems are lithium-ion batteries, offering approximately 0.5 km driving range per 1 kg of battery pack mass (see Funcke et al [1]). However, these battery packs require high level safety measures to avoid e.g. mechanical damage of the cells, which increases the pack mass again. In order to make a reliable statement about the battery safety at an early stage of development, detailed knowledge of the mechanical behavior of the cells as well as its reproduction in the virtual development process is necessary.

Based on a sample design of a main battery structure, the development process of the cell model is explained. The first steps are the integration of the design in a full vehicle and the determination of the dominant cell deformations, which are transferred to cell load cases. These mechanical abuse tests of cells deliver the input data for generating an adequate finite-element (FE) model, which offers the opportunity to dimension the battery pack and to add safety measures. With this simulation model inflatable structures as well as passive reinforcements for the traction battery are investigated.

To validate the simulation results, component tests on system level, i.e. complete battery packs, are conducted. The test is based on the full vehicle reference design load case, in this case the EuroNCAP pole side impact with a modified pole position and an impact velocity of 50 km/h. An analysis of the impact position is needed since the vulnerabilty to intrusion of the battery pack and the stiffness of the vehicle structure varies along the vehicle longitudinal axis.

These component tests confirm the simulation results and show the potential of inflatable structures and passive protection systems. Furthermore, it is possible to generate a FE model for lithium-ion batteries, which is applicable to full vehicle simulations.

Although it is possible to map the mechanical characteristics to the generated cell model, this model is limited to the investigated load cases, which have been the result of the battery position within the vehicle and the corresponding critical design load case. Since the battery may be placed in another position within the vehicle and the arrangement of the cells may change, the cell model is not universal. However, it is extensible to other load cases.

Overall, the results from the study with the inflatable elements show clearly the benefit of those structures. With low additional mass a high positive effect (e.g. lower intrusion) is achieved, which means the ratio of the incorporated mass to the reached protective effect is lower than with passive protection systems.