Development of power management system for electric vehicle “i-MiEV”

Mitsubishi Motors Corporation succeeded in mass-production of the new generation electric vehicle “i-MiEV” which was released into the Japanese market in July 2009. This vehicle features leading-edge technologies epitomized by lithium-ion battery. In this paper the power management systems are focused on. Following an introduction of some features of this EV, requirements for the control systems are explained with regards to protection of the lithium-ion traction battery. Finally the power management techniques implemented for compliance with the requirements for battery protection while charging and driving are described, and the validity of which is shown through some test data.

I. Introduction

Electric Vehicle (EV) is now regarded as an ultimate eco-friendly car and is highly expected to be popularized in the very near future because it emits no exhaust gas while driving and is powered by electricity which can be generated from a variety of energy sources including renewable ones. EV is propelled only by the electric energy stored in the traction battery, so its cruising range is determined by the performance of the battery. Therefore conventional EVs with low-energy-density batteries have not been able to sustain a viable consumer market because of their short cruising range and low acceleration performance. However the appearance of high-energy-density lithiumion battery has dramatically extended the cruising range of EV. Mitsubishi Motors Corporation succeeded in mass-production of the new generation electric vehicle “i-MiEV” (Mitsubishi innovative Electric Vehicle) (Fig. 1) and released it into the Japanese market in July 2009. This vehicle features leading-edge technologies epitomized by lithiumion battery. The cruising range is long enough for use in urban areas, and at the same time the driving performance is competitive with internal combustion engine vehicles. Fig. 1. Exterior of i-MiEV