Truth About Volt’s Mechanical Linkages Starts to Emerge

By · September 27, 2010

Back in June, we published a story on about how the Chevy Volt is more of a conventional hybrid than previously thought. Trusted sources had been telling us for months about how the Volt might not always act purely as an electric car, but we didn’t post the article until G.M.’s Rob Peterson confirmed that Volt engineers could use the gas engine to power the wheels—a signature of a parallel hybrid system—if it meant greater efficiency. Peterson said, “You could do it. Absolutely.”

We applauded G.M. engineers for putting efficiency first, and letting the marketing department take care of itself. At the end of the day, who cares if there are mechanical linkages between the gasoline engine and the wheels? As long as the Volt delivers on its 40-plus miles of all-electric range, and maximizes the efficiency of the gas-engine when it’s called into service.

When we published the first story, and then argued that exploiting any mechanical linkages could mean better efficiency, the most ardent Volt fans accused us of bad journalism. G.M. executives were quoted as saying that we just didn’t get it.

Mounting Evidence

Well, a G.M. patent application for the Chevy Volt’s transmission was posted today on Lo and behold, the application describes how the Volt’s two motor-generators, clutches and a planetary gearset can indeed be coupled to mechanically drive the wheels from the gasoline engine. Volt engineers might elect not to employ this linked configuration, but the application indicates that—with a software adjustment—it can be done.

G.M. Patent Application

Title sheet of G.M. patent application.

The revelation, if it bears out when the company fully discloses its design, would blur the lines between the Chevy Volt and hybrids like the Toyota Prius that use a parallel-series approach. In other words, it could call for a more common sense approach to describing any vehicle with an electric motor, a rechargeable battery pack, and a gasoline engine simply as what it is: a hybrid.

One Big Happy Family

What does it matter that the Volt is an electric car for the first 40 miles, and then can become a plug-in parallel-series hybrid? Probably not too much, except that the various pro-electric camps should stop bickering. Fans of the Chevy Volt, Toyota Prius, the Ford Escape Plug-in Hybrid, and the Toyota Prius Plug-in Hybrid can live under one tent.

“I cannot discern much of a difference between this and Toyota’s HSD,” responded one visitor to the patent story. “As for the transmission, I’ve thought all along that in the end, the Prius, the Volt, and Ford’s plug-in systems will all be splitting hairs from each other. I guessed a while back that the Volt is using a variation of the two-mode transmission. It just makes sense technically. They are all hybrids, really, by definition anyway."

Another visitor wrote, “Ah! A Toyota-like hybrid. This is the best way to get good efficiency at highway speeds and also to be able to utilize all three motors (ICE, gen, main drive motor) for extra power. You also get the benefit of having more total horsepower.” Exactly!

All major global automakers are expanding their production of electric cars, plug-in hybrids and conventional hybrids. At the end of the day, we all want to displace use of petroleum and reduce vehicle emissions—while enjoying all the benefits and enjoyments of our mobility. Any car that starts to shift us away from the stranglehold of pure internal combustion machines is a step in the right direction.


· George Parrott (not verified) · 7 years ago

Would not bother me at all, as a imminent Volt owner, I don't care if it drives mechanically after the battery to electric motor depletes or if the engine provides current to drive the motor for that extended range.

It would seem to me, as a non-engineer, that a direct drive system, once the engine has to kick in, would be more efficient that the mediated power systems of engine-generator-motor-drive of still using the EV power system AND the gas engine at the same time....Just seems like that would produce combined power losses.

But I am probably missing something, since I am a psychologist and not an engineer.

As a "simple driver" all I am interested in is having this vehicle get extended range of the more typical car (300-400 miles) before having to "repower." I want my shorter range driving to be "clean and gas free" but I am OK with any kind of range extension power train as long as it is still as economical as technically possible and as environmentally clean as possible.

We will have the Nissan Leaf for our daily shorter drives, but still, like many others, need one car for going between cities and on longer travels, so the "extended range" concept represented by the Volt will be virtually necessary for most American families.

· Alan (not verified) · 7 years ago

Good comment George, my one question to you. I too plan on getting a Nissan leaf for my commute, but I can't see why for the life of me I'd not get a Prius over the Volt. There is no cost justification in spending 15 grand more on the volt.

As to the 'clean' aspect of these Li cars - just how much pollution is generated in creating these batteries, what is the cost to our environment, the depletion or rare earth metals and minerals? I'm guessing that answer will be hidden from us for years to come!

· George Parrott (not verified) · 7 years ago

With the Prius, we would still be getting fuel regularly, albeit even with 50+mpg. With the Volt, we probably will not have to get any fuel except perhaps every other month when we might head down to the SF Bay area from Sacramento or up to Tahoe. Close to 99% of our Volt use will be all EV.

The extra cost is a good question and concern, but we are going to LEASE the Volt, and at the current GM lease offer, that cost is at least "not too" bad for the level of technology in the vehicle.

Being totally honest, I like cars as "boy toys," and keeping our current Prius 5 years and the Camry Hybrid 4+ years has been a recent "personal record" for longevity in our household. So, I suspect both the Leaf and the Volt are likely to be replaced 3 years or so down the road for the second generation of this emerging technology.

· · 7 years ago

@ Alan -

Good news. The answer about the Li batteries you seek is NOT hidden, and is available right now, right here. The summary: Not as bad as everybody used to think.

· St (not verified) · 7 years ago

I would like to thank you George Parrott for your comment. I am a college student at Georgia Tech and i real car enthusiast. My parents got me a 2010 Mazda 3 s sport sedan about 2 months ago but this Volt has been on my mind for months. I have looked up every youtube review about it and am astonished by its interior beauty and structural features. I would really like to get my hands on this car, even though it is rather expensive. But as a college student, in the long run i think it really is worth it. What would you advice for me to do in order to get the cash...Thank You

· St (not verified) · 7 years ago

I would also like to thank Brad Berman for the review too

· George Parrott (not verified) · 7 years ago


You are so far ahead of where I was at your time/age in terms of vehicle ownership. My Dad died when I was a freshman in college and from that point on there was ZERO safety net and parental support for my education, to say nothing about owning any car.

So, my advice is to be patient and work hard in school for now. When you are finished with your education, THEN you can be more independent and assertive about your car purchases...when you are spending your own earned $$$. On the other hand, it is often the case that getting your "first home" might have a higher logical/rational priority than ANY car purchase.

We can "afford" these toys now, only because we both stayed in school and went on to solid careers. My wife is a research biochemist at the Univ. of Calif., Davis and I a a professor of psychology at Cal. State. Univ., Sacramento. It took us 30 years of career work to get to this point of car choice and home choice, so...

Patience, and planning come first. Make the important decisions about career, significant other, and property/house purchases, THEN...a wide range of transport options become available.

· DG (not verified) · 7 years ago

Don't worry @ST - your parent will get you the VOLT when you graduate - no problem. Don't listen to George - he means well but he is so OLD SCHOOL and doesn't understand your generation.

· Alan (not verified) · 7 years ago

@George - Thank you for your candid reply, yes a lease may be the only way to go to justify the cost. You sound like a perfect candidate for the Honda Clarity.

I know its old news but I just stumbled across the info on the VW golf twin drive - not quite a plug in hybrid, but an interesting Hybrid nonetheless.

@ST, you may be lucky enough to be able to buy the 2nd or 3rd gen volt when your times comes. You are going to have a lot more options available to you then. Maybe a compressed air car eh ?

To add to the article above - The Volt sounds more like a hybrid more so now than ever before - a plug in EV hybrid - which makes the EV Prius plug in hybrid look even better.

I still think ultimately, the EV car I want down the line is a Hydrogen Fuel Cell car. It may use hydrogen but it essentially is an electric vehicle, the converted and compressed hydrogen being the battery. It is a plug-in, only instead of electricity going to a LI battery you store Hydrogen. The end game being that you never need a lithium ion battery (or thousands of them) to do the job. - and you will get hundreds of miles with a full 'charge'!

· Alan (not verified) · 7 years ago


hmmm, not exactly a glowing report, and is open to interpretation "15 per cent of the total burden can be ascribed to the battery (including its manufacture, maintenance and disposal). Half of this figure, that is about 7.5 per cent of the total environmental burden, occurs during the refining and manufacture of the battery's raw materials, copper and aluminium. The production of the lithium, in the other hand, is responsible for only 2.3 per cent of the total. "Lithium-ion rechargeable batteries are not as bad as previously assumed," according to Dominic Notter, coauthor of the study which has just been published in the scientific journal "Environmental Science & Technology."

"Not as bad as previously assumed" is not really a glowing endorsement and does not mitigate the environmental effect/damage cause by their (Li battery) production.

"The conclusion drawn by the Empa team: a petrol-engined car must consume between three and four liters per 100 kilometers (or about 70 mpg) in order to be as environmentally friendly as the e-car studied, powered with Li-ion batteries and charged with a typical European electricity mix". - not what I'd call earth shattering figures. That last figure almost stopped me dead in my tracks !!!

· · 7 years ago

@ Alan -

I didn't offer it as a "glowing" report. Just a current, and seemingly accurate one. A response to your guess that this information would be hidden for many years. I'm not sure what you were expecting? That EVs would be perfect and free from environmental damage? There is no perfect, non-damaging transportation solution. Our task is to find the best one. And EVs are it (I'm leaving out bicycles for the sake of argument here). They may not be as "better" as you'd like them to be. But if we don't go with better, what are our choices? Stick with worse and forever hope that FCV's will be perfect?

If we compare EVs on some randomly-chosen current grid mix, we get a snap-shot of the pollution they create today in one region. Grids everywhere are getting cleaner, however. And my personal EV is fueled with sunshine. I dare say that it would take a gasoline car that gets WAY better than 70 mpg to emit the same pollution that my solar-powered EV offers up.

· George Parrott (not verified) · 7 years ago

The California Fuel Cell Partnership headquarters is only about 1.5 miles from our house in West Sacramento and one of their staff live on our street. This is where virtually all the prototype Fuel Cell vehicles from every major player are in daily use testing and the last Friday of every month there is an "open house" for people to be briefed on these cars and the fuel cell technology that they represent. After the general intro talk, visitors get taken to the back lot and staff drive them around in each of the cars they want to personally experience.

I agree fuel cell technology holds GREAT promise, but the infrastructure for hydrogen is simply 5-10 years "away." while battery technology is "here now."

And I tried to get on the early Honda Clarity lease program, but those are only in SoCal, as there are no trained dealer service settings here in the North part of the state.....

· · 7 years ago

Living in Davis as I do... I'm also by the CAFCP quite often as you can imagine. Sure seems like there are more crickets than major OEMs occupying the spaces there lately.

· John Bailo (not verified) · 7 years ago

So it sounds more like a standard Prius with a bigger and heavier battery that will cost a lot to charge and run out of juice fast so that the gas engine ends up driving it. The fuel efficiency, like the Prius, will mainly come from it being such a teeny-tiny car.

· · 7 years ago

Don't take this as defense of the Volt... only the defese of reality.

The big difference between a Prius and the Volt is that the Prius can't run on battery power for any meaningful distance. The idea, of course, is that the Volt can be used on battery power alone for *most* trips that most people make most days. The Prius burns gas on every trip (yes there are edge cases that I'm ignoring).

Charging a car with a battery the size of the Volts will cost very little. Especially when compared to the gasoline it will displace.

Running out of juice "fast" is subjective, I guess. In general, the battery range of the Volt will cover most trips made by car in the US.

The Volt is by no means "teeny-tiny" though that is subjective as well. Certainly there are many, many cars on the road that are smaller than it is.

· Jmcgrane (not verified) · 7 years ago

In everything I've read about the Volt just how far you can drive has not been clear. I understand the 300 or so mile range but what is that dependent on. Nothing has been said about the size of the gas tank, how many miles electrically per gallon and can you just fill up the tank again and drive another three hundred miles without recharging which essentially mean you could drive across the country . Understandably using for the 40 miles electrically you would have to recharge on a daily basis but do you have to recharge after the 300 miles in order to keep going.

· · 7 years ago

Jmcgrane -

The battery of the Volt never *needs* to be charged in order to operate. It will drive as long as it has gasoline in it, similar to a current model Prius. I'm not sure what the tank size is either, but we've assumed about 8 gallons for a while now - based on several factors. So yes, the car can easily be driven across the country as long as you stop every five hours or so for gasoline. This "feature" is the big deal that GM is hanging their hat on. They've managed to build the world's first EV that uses gasoline! ;)

· · 7 years ago

It isn't that complicated. Here's a simple view of the Volt
- after you've plugged in, it's an Electric Vehicle, up to about 40 miles
- beyond that 40 miles or if you haven't plugged in, it's a normal gasoline fueled vehicle. If you run low on gas, you go to your gas station and fill up, just like all old gas cars.
Nobody really cares how far a gas car can go on at tank of gas and I can't understand why everyone's getting wrapped around the axle about how far the Volt will go on a tank of gas. I have one gasser that goes 600 miles on a tank (it's a hybrid) and my gas guzzling SUV only goes about 275.
The direct answer to your question is that while driving across the country (or if your wife's car is blocking the charger in the garage), you can just keep adding gas and keep going.
The only think you might consider doing is to hit the "Mountain Mode" button if you think you'll be climbing a steep mountain but you're gas mileage will suffer very slightly.

· · 7 years ago

There are rumors about the tank being 9 or even 9.3 gallons. Everyone is doing the same math, dividing 300 by the number of gallons to guess about mpg in charge sustaining mode. The bigger the tank, the lower the post-40-mile mpg--and frankly the worse the Volt looks for long-distance drivers compared to a conventional hybrid like the Prius.

Again, it's guesswork at this stage. But it underscores that the best electric-drive car for you depends on your driving patterns. Of course, most people will buy based on what feels and looks cool--not a super-rational argument.

· · 7 years ago

The Volt's achilles hill is being considerably worse than a HV Prius in CS mode, and considerably less than a LEAF in EV mode, while being much more expensive than either competitor. Off hand the only rational buyer I can imagine is one who demands, and is willing to accept less EV to gain petrol capability *in a single car.*

GM will spin the car as the answer for 'range anxiety,' but personally I think it would cause me 'EV anxiety' and 'CS heartache.'

· · 7 years ago

You don't even know how a Volt works in CS mode yet since that hasn't been announced or tested. Where do you get off condemning it already.
If one only drives 40 miles at a time most of the time, the Volt will work just as well in CD mode as a Leaf.
Where do you dig up "EV anxiety"? What's to be anxious about?
There's a large market for both the Leaf and the Volt, just as there's a market and need for a minivan and a compact bodystyle.

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