Battery modeling approaches and management techniques for Plug-in Hybrid Electric Vehicles

Batteries play a critical role in Hybrid Electric Vehicles (HEV) and Plug-In HEV (PHEV) as one of the main energy sources because of their high energy density. Therefore, for designing purposes suitable battery models are necessary. Batteries have very nonlinear behavior and are dependent on many factors such as chemistry, temperature, load profile, charge/discharge algorithm, age, etc. Modeling the behaviors of the batteries can be achieved using different approaches and techniques. The more accurate battery model is, the more reliable results are obtained using simulation softwares. However, increasing the accuracy of the model increases the complexity of the whole system model and also the time of the simulations. In the case of vehicular applications batteries are used as packs of hundreds of cells which adds to the complexity of the model, since some behaviors are exaggerated. Besides, some effects such as the difference in state-of-charge of different cells which leads to the age reductions of the whole battery pack, or for example the temperature difference of the cells in different places of the pack cannot be ignored. For optimal designing purposes there should be a kind of tradeoff between accuracy and complexity. There are various battery models based on various approaches and techniques in the literature which may cause confusion. This paper tries to summarize and categorize different battery models with main focus on vehicular applications.