Sizing ultracapacitors for hybrid electric vehicles

An efficient energy storage medium is essential in all hybrid electric vehicles. The advances in double layer electrolytic capacitor technology have opened new areas to complement batteries as a storage medium. In this paper we will review some of the present applications of ultracapacitors as well as to provide guidelines for sizing ultracapacitors for minimal mass in hybrid electric vehicles. Equations for both constant current as well as constant power discharge are discussed. An iterative method for determining the minimum number of ultracapacitor cells is introduced. The effects of ultracapacitor sizing on the rating of interface power electronics are examined.