[danielnaab]

Years ago, my impression was that the goal of the Volt was to be fully-electric with a range-extending flex-fuel generator that recharges the batteries (rather than a hybrid approach with a separate internal combustion engine to extend range).

Is this idea just totally dead for some kind of innate technical challenge? It seems that mechanically, the cost of a generator and one drive train would be preferable, if it were feasible performance-wise.

[dsfyu404ed]

Unless you scale it up (diesel electric locomotive) you loose too much energy going from gen-set to motor. It makes more sense to just send the mechanical energy from the engine straight to the wheels. Generating power requires a close to static engine speed and optimizing for that is very much in conflict for optimizing the typical emissions/fuel economy/power/reliability/price criteria by which cars are assessed.

It would also almost certainly be diesel.

[ams6110]

You're talking about a series hybrid design? I.e combustion engine powers a generator which in turn powers electric drive motor(s), usually with a battery system to allow for buffering generator output and to capture power from regenerative braking.

For long distance highway driving, this is less efficient since you have losses between the generator and the electric motors. It can work well for mostly stop-and-go driving and is used in hybrid buses I believe.

[ScottBurson]

I had always thought the Volt was a series hybrid, but I just checked [0] and it turns out there's a mechanical bypass mechanism that can connect the gasoline motor to the drivetrain, under control of the engine computer. Sounds like at low speeds it operates as a series hybrid, but at highway speeds, once the batteries are drained, it turns into a parallel hybrid. Clever!

EDITED to add: dwhall posted a link with much more detail [1] -- very interesting!

[0] https://en.wikipedia.org/wiki/Chevrolet_Volt#Drivetrain

[1] http://gm-volt.com/2015/02/20/gen-2-volt-transmission-operat...

[crabasa]

That idea is alive and well. Just look at the BMW i3:

http://m.bmwusa.com/#overview_styleid91_16IB

[ams6110]

However the combustion engine in the i3 is insufficient to power the car. It extends range only (up to 150 miles). So it's not a car you can take on a long road trip.