We illustrate our approach by applying the methodology outlined above to determine the attributes of fuel cell systems for a typical mid-size family sedan with gross vehicle weight, frontal area, drag coefficient and coefficient of rolling friction listed in Table 1. The vehicle has a gross weight of 1900 kg that includes 1030 kg for the glider (body plus chassis), 136 kg for payload (cargo plus driver), 380 kg for the FCS, and 354 kg for the electric drive train. For this vehicle, Fig. 3 shows the power demand on the FCS as a function of vehicle speed and on 6.5% grade at 55 mph with 600 kg payload. In determining the power demand on the FCS, we have used a performance map for the traction inverter motor (TIM) that describes its efficiency as a function of the motor speed and torque. The TIM efficiency derived from the performance map is also presented in Fig. 3 as a function ofvehicle speed and on 6.5% grade. The TIM efficiency peaks at 94% at 75 mph vehicle speed and drops to 84–85% as the speed is raised to 100 mph or lowered to 10 mph.In calculating power demand we have assumed peak efficiencies of 94% for the torque coupler and 97% for the final drive.According to the results in Fig. 3, the traction power requirements for this vehicle are 65kWe at 100 mph top speed and 62kWe at 55 mph on 6.5% grade with 600 kg payload.We have also determined that the vehicle needs a peak power of about 120kWe to be able to accelerate from 0 to 60 mph in 10 s.For this vehicle, the traction power at the top sustained speed (65kWe) rather than at 6.5% grade defines the minimum power rating of the FCS so that systems of 65–120kWe rated power are potential candidates. The 65kWe FCS will need the largest ESS whereas the 120kWe FCS can power the vehicle without an ESS.