(a) We define the minimum power rating of the fuel cell system to be the higher of the power demand at 100 mph sustained speed and the power needed at 55 mph at 6.5% grade.(b) We further require that the FCS be 50% efficient at the rated power point. This requirement determines the cell voltage at rated power.(c) We require that the FCS be able to operate without overheating at ambient temperatures up to 42 ◦C. This requirement is met by sizing the heat rejection system for duty at the most stringent sustained driving condition on a 42◦C day.(d) We size the water management system so that the FCS is water balanced for all sustained loads at 50% oxidant utilization and ambient temperatures up to 42 ◦C.(e) We meet the 1 s transient time target by overloading the CEMelectric motor for short time periods and, if needed, allowing the maximum oxidant utilization, generally limited to 50%, to rise to 60%.