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The Volt's gasoline capacity is being cut back

The Chevy Volt plug-in electric car from GM is one of the most desired new cars coming to the market.  Everyone is talking about the car's stylish design and relatively affordable price tag of around $40,000; not bad compared to past electric cars totaling over $100,000 like the Tesla Roadster.  With sales planned to commence in 2010 and with a production model possibly being unveiled later this year, the buzz surrounding the new vehicle is intense.

One fact many people didn't know is that while the Volt is an electric car, relying first on charge, it also sports hybrid capabilities.  It features a 12 gallon gas tank, which will only kick in after the lithium-ion battery charge is depleted.  This could take the car 600 miles, thanks to an impressive 50 MPG projected fuel economy.

However, recent reports have revealed that GM, in a surprising development, has decided to cut down the fuel tank for the Volt.  They won't say what the new capacity will be, with the source only saying, "We're working on that." 

The original goal for the Volt was to equip it to drive 40 miles on a charge, without using any gas.  This goal remains, and appears to be within GM's reach.  Additionally, since 40 miles isn't long enough for road trips or longer business travels, GM planned on adding the gas tank.  The gas does not power a traditional engine, but rather a generator, which provides enough charge to keep going, and actually performs more efficiently than most gas-engines.

GM has revised the target range to 360 miles, which would seem to indicate a fuel tank of 7.2 gallons.  The reasoning behind the cut is research that cars, on average, travel less than 40 miles a day.  While GM wants to provide a comfortable extension to this range, it decided that 600 miles was a bit excessive.  Many older sedans don't get much more than 300 miles on a 12 gallon tank, so the new range seems relatively reasonable.

Jim Hossack, vice president of AutoPacific, an automotive research and consulting firm states, "Most cars today have a range of more than 300 miles and less than 400 miles before refueling.  GM didn't need a longer range because most bladders can't go 600 miles.  By going with a smaller tank it means GM can take weight and price out and make Volt a little lighter and a little cheaper, and that's what you call making an improvement."

While GM's move should help it cut costs and cut down slightly on the weight of the vehicle, it may come as a disappointment for fans of ultra-long treks across the country.  Still, it is dubious that such minor gripes will be able to do anything to quell the PR frenzy surrounding the Volt.

At its price tag, even with possible subsidies, the Volt will likely fall into the luxury car class.  However, with its wild popularity and sleek looks, it seems likely to thrive in this class, or whatever class it may enter as prices drop.



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RE: Hybrid
By randomly on 7/9/2008 5:26:10 PM , Rating: 2
Yes in the series hybrid the ICE drives a generator which drives the electric motor which drives the car.

Yes there are additional steps of energy conversion. However they are highly efficient steps, in the +90% range.

NO the loss in efficiency from the added steps does not use up all the gains made up by the increase in efficiency of the ICE. The increases in ICE engine efficiency are very large.

In fact serial hybrids have long been in use in large cargo ships where they can attain efficiencies as high as 56%.

Don't forget than in the parallel hybrid you have to go through a transmission which is a similar +90% energy conversion stage.

The serial hybrid engine can be made smaller than a parallel hybrid because
1) it does not need to supply the peak power requirements needed by a parallel hybrid system.
2) the increased efficiency gains from running the engine at a constant load/RPM also increases the power density of the engine allowing you to get the same power out of a significantly smaller engine.

Your statement about only 1/3 of the cars power being available to drive the car is incorrect. There is no requirement to recharge the batteries once they are depleted enough to trigger the use of the ICE. All the power of the ICE can be used to drive the car. Batteries can be recharged or not charged at any rate you desire.

The motor being used as a generator, is just that. a generator. It's not another motor available to do work. Electric motors and generators are compact efficient pieces of gear. I wouldn't be surprised if the motor and generator combo in the volt is smaller than the engine in a prius.

If you feel your are so right about your analysis you should contact all those GM engineers and tell them they are wasting their time and hundreds of millions of dollars.


RE: Hybrid
By pauldovi on 7/9/2008 9:35:00 PM , Rating: 1
No ICE can obtain an efficiency of 56%. Have you ever studied the Carnot cycle? The most efficient engine in the world was a large steam power plant that achieved efficiency in the low 40's.

The ICE is not connected to the powertrain in the Volt! How can it drive the car?

If you have a 100HP electric motor that drives the car, a 100HP gasoline motor that powers the generator that charges the batteries, and a 100HP generator to charge the batteries you have 300HP total onboard but only 100HP actually drives the car. This is a huge waist!

A electric motor and a generator are the same thing. That is my point that it isn't another motor available to do work. That is why you are wasting available power on the vehicle.

We all know that every vehicle GM has ever made has been perfect! I guess that is why they lost $35 billion this past year.


RE: Hybrid
By randomly on 7/9/2008 10:11:51 PM , Rating: 3
Yes I'm fully aware of the Carnot cycle limitations on heat engines.

Do a little research on Serial hybrid systems for cargo ships. They are low speed diesel combine cycle systems and efficiencies do reach %56. These are not theoretical systems either but systems currently in use. Not really surprising considering fixed combine cycle power plants have efficiencies up to 60%.

I would never suggest that GM vehicles were even remotely perfect. But GM engineers are not stupid and serial hybrid technology has some significant advantages. This is why many other car companies are pursuing it including BMW, Mercedes Benz, Toyota, etc. Maybe they know something you don't?

Your reasoning that a 100hp gasoline engine driving a 100hp generator driving a 100hp electric motor means you have 300hp worth of power available is goofy. You obviously aren't an engineer. If it upsets you so much just put the generator and the electric motor in a black box and rename it TRANSMISSION and be happy.


RE: Hybrid
By pauldovi on 7/10/2008 11:30:21 AM , Rating: 2
Just because a company does something does not mean it is the best way to go about it. Having an vehicle that is an "electric" vehicle may have implications beyond the mechanical advantages, such as tax advantages and appealing to the "green" side of people.

I never said 300HP was available. But 300HP worth of engines is onboard. Meaning you are paying for 300HP worth of engines, carrying around 300HP worth of engines, but only driving the car's wheels with 100HP. That seems pretty silly to me.

I do not rebuttle personal comments so I will not respond to that.


RE: Hybrid
By Jim28 on 7/10/2008 10:59:58 PM , Rating: 2
You still don't get it.
The drive engine is 120Kw, the ICE/generator combo outputs 53Kw.

Obviously the drive engine can't deliver peak power on the ICE/gen alone but it is more than enough to drive the car BY Itself as peak power is only needed when you put your foot to the floor.
When that happens the motor pulls additional current from the battery pack. The car does not wait for the battery to be completely depleted to start the ICE/gen so that it has a little punch left.
In normal driving the drive engine may need say 40Kw to run the car, the extra 13Kw the ICE/gennie outputs is used to charge the battery and overcome the 10-12% conversion losses.(guessing here but it should be in the ballpark.). See! Energy is conserved, the Thermo gods are happy!
In engineering terms this type of power plant is called a turboelectric drive. (At least on ships and ships don't use batteries.)


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