Charging ahead

With the constant performance improvement and cost reduction of power electronics and motor drives, more efficient vehicles such as electric, hybrid electric, and plug-in hybrid electric vehicles (PHEVs) are becoming a reality. The commonality between all advanced vehicles is the presence of electric propulsion powered by an electric storage system. As a result, the development of adequate energy storage systems is now more important than ever. High energy density, modularity, and affordability have made batteries the technology of choice for vehicular applications. In recent years, battery technology has made great strides in improving the energy and power density. Still, a tradeoff between power and energy must be made to best meet space and weight constraints. In this article, we shed some light on this tradeoff. We also look at how batteries can be represented with equivalent circuits. Finally, we go into some detail on battery management requirements that ensure that the batteries perform as expected. Power electronics has revolutionized motor drives, bringing within the realm of possibility electric drive-trains with extremely high performance. The motors themselves have been improved, offering higher reliability and better performance with a reduced cost. Unfortunately, the weak link in the electric drive-train development chain remains-energy storage. There are some advancements in energy storage device development that offer good promise in terms of energy density and power density but none have the desired combination of all of the following features: fast charging-discharging (high-power density), large-storage capacity (high-energy density), low cost, and long life.