NEWS FLASH! The Chevy Volt does not use its gas engine to recharge its batteries!
It was commonly assumed that the gas engine component did exactly that, recharge the lithium-ion batteries. Not so, apparently. The confusion stems from some early GM press releases on the concept Volt, and had been subsequently passed on as gospel by the media.
All you will get from the electric batteries is 40-gas free miles. Beyond that the gas engine comes into play, so you're using both gas and electricity, just like a conventional hybrid.
Here's Inside Line's take: No "Revolting" the Volt: Chevy Battery Does Not Recharge While Driving
Update: Here's some additional info that was just sent to me regarding the Volt's powertrain:
Unlike traditional electric cars, Chevy Volt has a revolutionary propulsion system that takes you beyond the power of the battery. It will use a lithium-ion battery with a variety of range-extending onboard power sources, including gas and, in some vehicles, E85 ethanol(3) to recharge the battery while you drive beyond the 40-mile battery range. And when it comes to being plugged in, Chevy Volt will be designed to use a common household plug.
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This seems a little strange. If that's the case, why not get rid of the battery and make a high mpg, electric drive, sedan?
This isn't surprising to anybody who has actually been following the Volt and understands how it works:
http://gm-volt.com/2008/08/25/what-happens-in-the-chevy-volt-past-the-customer-depletion-point/
The gas engine in the Volt, however, is NEVER used to drive the wheels, only to provide enough charge to the battery to continue driving, so it is not "just like a conventional hybrid."
dilettante, thanks for the further clarification. :)
Fantastic link dilettante, short to the point and exactly what we needed. It does make sense to me. Why would I want the gas engine to fully recharge my battery... then why would I plug it in at home?
I wonder what happens if you drive with a heavy foot. If the generator is only half the size of the motor, it will have trouble keeping the battery near 30%. If you run the battery too low, you will only have the power from the small generator which will really cut back performance.
Also while I can see the advantage of the 40 mile electric range, I'm not sold on the rest of the concept.
Using a gas motor to spin a generator which then charges a battery which then drives an electic motor is not inherently efficent. Every time you change energy from one form to another there are loses. Here you are going from gas to electric to chemical to electric.
I'm really curious to see what the performance and mileage are like when driveing in gas mode.
One reason for engine not recharging the batteries is apparently the Volt's design involves repeated deep discharging of the battery pack. As discharging can damage many batteries and reduces their storage capacity, it'll be interesting to see how GM gets over that hurdle.
Locomotives use a diesel > electric motor power train because of electric motor's excellent torque control/start from stop capabilities. But they are not especially fuel efficient.
And what about apartment renters? Few of those have handy electric outlets to recharge their rides every night!
A conventional or refined hybrid with longer range / larger batteries makes more sense than the Volt.
It makes a lot more sense now. The IL article suggests that after 40 miles (give or take), the battery is out of the picture. That doesn't appear to be true. IL, ya wanna fix that?
I suspect they feel that 30% will cover any short term need beyond what the generator can output. This isn't a race car after all.
Firstwagon, here's my theory on your concern: The extra conversion does have some deficiency. However, the motor is likely designed to be highly efficient at a given power output level. Using the motor to directly drive the wheels would require the engine to run at power levels that are much less efficient. I suspect the efficiencies lost in the conversion (motor->battery) are less than those gained by having the motor operate at peak efficiency.
My round-trip commute is 26 miles. I bet most americans would be OK with 40 miles as well.
This news won't stop demand.
If this car were a Toyota or Honda product I highly doubt the media would be trying to pick it apart. Lets see how the media treats the new Prius and Honda Insight for comparison.
I will add however, given the hype and publicity GM has given this car it has no choice but to be a standout because if it fails......well....you all know what will be said.
Im going to wait, let the car hit the market and prove itself before making assumtions as I highly respect GMs effort in producing something different vs your average hybrid. Honda did a similar thing with its excellent FCX Clarity.
I think its good to see car manufacturers take drastically different routes when it comes to energy savings as maybe a combination of them all will be the best solution....who knows.
There are three perfectly good reasons the engineers would choose to not fully charge the battery with the onboard generator
1. It is less expensive to charge the battery at home than with gasoline..?
2. They need to retain the ability to do regenerative braking and you cannot do this with a full battery. (I suppose the Prius must do the same thing).
3. Conservation of the life of the battery (I'm not saying I know this but obviously it is a possibility)
If the petrol engine recharged the battery (at a constant rate), its power output wouldn't need to support prolonged maximum acceleration.
Frankly, I'm more impressed by the Chinese BYD e6 - 300km (186 mile) range, 80% charge in 15 minutes. Warren Buffet seems to be impressed too.
Try again, Lutz. We've all the time in the World.