It would depend on the effect of speed on motor efficiency, but primarily on the increase in energy to move through the air. At highway speeds and for the average car, most of the energy goes into moving against aerodynamic drag. This is proportional to the square the of the velocity so the energy use per mile would go up by roughly a factor of 4 for every doubling of speed, except that the efficiency curve for the Volt, I think, is not publically available. As you know, efficiency depends on motor speed.
There is some controversy about how the car will perform at higher speeds actually. Check out the videos at:
http://www.plugincars.com/exclusive-video-want-know-exactly-how-chevy-volt-powertrain-works-95344.html
if you get the chance. Three videos, total time is around 20-30 min. I think. Probably a lot more detail than most people want.
I think the best way to view the Volt is as a battery electric for city driving that switches to a gas vehicle for significant travel at highway speeds. I think the statistic is something like 60% of all trips in the US are taken within 15 miles of the home with a single person behind the wheel. In that case, the Volt will be driven on the batteries alone alot. It is a good compromise for the way most people expect a car to perform. That is, one car to do nearly everything, over the river and through the woods to grandma's and also a short distance daily driver. Can one car do it all? I've heard GM engineers in their fuel cell car division/group speak and market research tells them that a car that won't do at least as much as the current cars will is a non-starter. Nissan is taking a different approach. I am very curious to find out if both solutions will co-exist or if GM is correct. The "battery car" has been tried before and failed. The Leaf roll-out has the best chance for long-term survivability yet but we will see.
The volt is already obsolete.
costs too much and can't swap packs.
Once they redesign it and sell it without a pack, it will be a winner and ~half the cost.
Very exciting to see this play out.
The early battery cars, in 1910, faced really cheap oil and expensive electricity. Now the situation is reversed. And nobody tried the "pack swap" method which is key for success. I won't buy a cordless drill without an extra pack, and i sure won't buy a car without quick swap pack capability.
