Electric energy storage is among the most significant hurdles to deployment of electric vehicles (EVs). Present storage methods struggle to provide the capacity and the service life demanded by automotive use. Hybrid energy storage systems (HESS) use a combination of storage types, for example, different types of batteries and ultracapacitors, to tailor the characteristics of the storage system to each application. In addition to sizing the system for the intended application, a suitable strategy for the integration of the energy storage system must be adopted. In the present application, a HESS has been designed for the electrification of a 2004 Chrysler Pacifica, through consideration of a combination of high capacity batteries, high power batteries, and capacitors. Hybrid storage systems using batteries alone, batteries and capacitors, and dual batteries have been considered. Each configuration used high capacity batteries as an energy device and a power device such as capacitors or high power batteries. The high power device was sized to accept and deliver the kinetic energy of the vehicle at highway speed. The energy device was used to provide a suitable range. Whole vehicle simulations were performed over a variety of drive histories using MATLAB® and Simulink® to assess range and power performance of the system. Service life, mass, and range were considered in the selection of the final configuration.