(a) FCS alone must be capable of meeting the vehicle power demands under all sustained driving conditions. These include a specified top sustained speed, taken as 100 miles h−1 (mph) in this study, and ability to maintain the vehicle at 55 mph speed at 6.5% grade for 20 min.(b) With the assistance of ESS, the FCS must have the response time to allow the vehicle to accelerate from 0 to 60 mph in a specified time, taken as 10 s in this study.(c) FCS must have 1 s transient response time for 10–90% power.(d) FCS must reach maximum power in 15 s for cold start from 20 ◦C ambient temperature.(e) FCS must reach maximum power in 30 s for cold start from −20 ◦C ambient temperature.