Abstract
Building practical plug–in electric vehicles is under way at many car companies around the world, though it is expected that they will not be widely available in the USA for quite some time. The ultimate vehicle cost is controlled substantially by the battery storage capacity required and this, in turn, is governed by the vehicle size and performance expected by consumers. The present paper examines the specific situation where existing hybrid vehicles might be converted to plug–in functionality by adding a supplementary battery pack to extend the driving range while keeping the electric/gasoline hybrid drive–train intact. We examine fuel efficiency from the standpoint of vehicle weight to extract system parameters that quantify the extra fuel consumption associated with driving a slightly heavier vehicle after plug–in conversion has been effected. We show that only modest additional battery capacity is required to meet most commuter needs in a cost–effective manner.