[NeilBlanchard]

The eVaro has about 120 mile range on the battery alone, so you would be silly not to plug it in. And, this is the most efficient way to use the gasoline -- think of the generator --> electric motor as the transmission. The reason we need a clutch and transmission is because it is hard to match the torque available with the speed you need to travel. In an ICE --> transmission, you almost never can use it at the optimum RPM; only when you get it up to the ideal highway speed.

As one of the FVT guys has said: internal combustion engines love to be run at a constant speed -- they love it!

The serial hybrid allows you to run the gasoline engine at it's most efficient RPM all the time, into a constant load. You use what you need to power the electric motor(s) and you collect the excess power in the battery, until it is fully charged, and then you can drive another 120 miles on the battery only.

So here's the scenario: you plug in the vehicle and charge it during the night. You drive up to 120 miles on that charge. If you need to drive farther, say a long all-day trip, the engine then runs for 1 hour, recharging the battery and letting you drive at highway speeds. You then can drive another 120 miles on electric only.

So, you charge it up before you start, and drive 2 hours at 60mph. Then the genset runs for 1 hour while you drive another 60 miles. Then you drive 2 more hours at 60mph on electricity. You have traveled 300 miles in 5 hours and the engine has only run for 1 hour.

If you need to drive farther, the engine runs for 1 more hour, and then you can drive 2 more after that on electric only; bringing the total to 480 miles in 8 hours with the genset engine running for just 2 hours.

Sounds pretty darn efficient to me!

The DC motors on the eVaro are custom made, and they are very efficient -- like 40% better than the AC55 used in the previous prototype, partly because they do not need any reduction gears. The eVaro is very fast" 0-60mph in ~5s. The genset engine is 1100cc -- there is no way that it could achieve that much speed all on it's own, because it is the peak power of the ICE that is used -- when you use a transmission, you cannot hit that peak very often.

Oh -- I almost forgot: in this serial hybrid setup (or in a pure EV), you get to have regenerative braking. The folks at FVT have worked very hard on this, and they are able to get all of the braking down to 5mph from the regen -- below 5mph, the friction brakes are also used to fully stop. So, in city driving, you lose only some energy to rolling friction, aero drag, and the last 5mph. By having the battery and the really efficient electric motors, you can regain a lot of the energy you used to accelerate the vehicle.

This is impossible to do in and ICE-only car, obviously.