3. A Novel Battery System for Electric Vehicles

Battery electric vehicles are the optimum way of clean transportation without any pollutant emission. The power source needs to have both high power and high energy densities in electric vehicles. Lithium-ion is the most energy- and power-dense battery type, compared with the other types; however, none of the other commercial batteries provide both of these two features together. Therefore, mostly battery-supercapacitor hybrid systems including high-energy batteries and high power supercapacitors are used. Supercapacitors have higher power densities and longer life cycle than batteries; however, they are heavy and have longer charge and discharge times. Besides, following the development in lithium battery technologies, features of lithium batteries are improving while the prices decrease. Thus, a suitable battery can be used rather than a supercapacitor in order to maintain high power. In this study, a new structure named hybrid battery system is proposed. The system includes two different lithium batteries with different energy and power characteristics. One of these batteries has high energy density, while the other has high power density. In this paper, the proposed system is introduced in details, energy management of the system is performed, and the results are validated by real-time experiments by using Kokam SLPB55205130H and Altairnano 13 Ah automotive-grade batteries.