An investigation of hybrid energy storage system in multi-speed electric vehicle

Thanks to the lower overall emission of Electric Vehicles, the promising transportation has attracted numerous attentions from industry and academy. However, as a consequence of lower energy density in widely adopted electrochemical energy source-battery, the driving range per charge presents a major barrier for electric vehicle's large-scale commercialization. Additionally, the limited battery life and extra costs associated with its replacement are other negative factors that hinder the development of electric vehicle. Currently, the one-speed gearbox is dominant in electric vehicles' market though it is only a trade-off between manufacturing cost and vehicle performance. Therefore, multi-speed electrified powertrains have been proposed and investigated in this paper to pursue the improvement of energy efficiency and dynamic performance without increasing battery size. In addition, supercapacitor, as the supplementary to battery, is combined with multi-speed transmissions to improve driving range and battery life. The combination of two advanced technologies are investigated in both B and E-class electric vehicle. Results demonstrate that considerable benefits attained for both small and large passenger vehicles through the application of multi-speed transmissions. The effectiveness of hybrid energy storage system in protecting battery from damage is verified. The relationship of hybrid energy storage system and multi-speed transmission is reported.