Modeling & Simulation, Testing & Validation (MSTV)


by Venkatesh Babu; Matthew P. Castanier; Yi Ding


Lithium-ion (Li-ion) batteries have become an important energy storage solution for a wide range of applications from consumer electronics to automobiles. In particular, the automotive industry’s push for improved fuel efficiency has led to the development of electric and hybrid-electric vehicles, many of which use Li-ion batteries. In addition to these fuel-saving motivations for Li-ion batteries, the US Army has its own unique mission requirements for onboard energy storage and available power, which could potentially be addressed at least in part, by Li-ion batteries. However, military ground vehicles are also subject to harsh operating conditions and abuse conditions that can cause failures of onboard equipment. Due to complex nature of the batteries, it is numerically challenging to capture the behavior of these batteries under abuse conditions such as a high-energy impact event. Each battery cell is made up of several layers and sub-layers of different materials. If a finite element model is created by meshing each sub-layer with sufficient detail to perform a ballistic simulation, even a single battery cell will have millions of degrees of freedom (DOF). In a hybrid-electric vehicle battery there are typically tens of cells in a module and hundreds of cells in a full pack. Therefore, the computational challenge associated with using finite element analysis (FEA) for ballistic simulations becomes daunting. In this work, a new method is proposed that employs a Thick Shell Composite (TSC) representation of Li-ion batteries using the commercially available FEA software, LS-DYNA. This approach shows promise for modeling the battery at the module or full-pack level with significantly reduced computational cost compared to a more traditional modeling approach. Individual layers are embedded into this TSC in order to reduce the number of finite elements in each cell significantly. Several of these cells are then assembled either in series or parallel to represent the module and the full battery pack. The TSC numerical model is validated by running a simulation of a bullet impact test and comparing the results to the equivalent physical test. The TSC model predictions show good agreement with the experimental results. In addition, three different impact angle scenarios (oblique, vertical, and horizontal) are simulated for one module of a generic Li-ion battery using the new approach. The extent of the predicted battery damage due to these different impact loading conditions are compared both qualitatively and quantitatively.