Op-Ed: More All Electric Miles Equal Less Range Extender Need For 2nd Gen Chevrolet Volt


The 2nd Gen Chevrolet Volt Volt Gen 2 Would Benefit From A Smaller, Lighter Pure Series Range Extender.

The 2nd Gen Chevrolet Volt Volt Gen 2 Would Benefit From A Smaller, Lighter Pure Series Range Extender.


With More Electric Range Comes The Need For Less Range Extender

I think we would all agree that, as AER increases, the need for a range extender decreases. This is depicted graphically in figure 1.

If we have an EV with 200-300 miles range, no range extender is required: witness Tesla Model S. If we have an EV with 100 miles range, a small range extender will suffice: witness BMW i3.

How does the Volt fit into this picture? We need to put some numbers to the words. (Engineers love numbers..yes?)

What Does Voltstats Say?

GM pitched the Volt by saying: “We will just make the battery big enough to cover the daily driving distance of the average driver of 40 miles.”

But how many miles does the average fleet driver really drive in a day?


50 Mile Mark Is More The Sweet Spot

Referring to figure 2, we see a high concentration of drivers at the 50 mile mark using the range extender. Also, referring to figure 3 we see an average fleet MPG of 135 miles/gallon.

Figure 3

Figure 3 (click to enlarge)

In figure 4 the AER/ER split is calculated that gets 50 miles total range and 135 MPG. The breakdown of the average fleet driver is: 36 miles on electricity and 14 miles on gas for a total of 50 miles. The 36 mile AER is probably less than 40 because some of the fleet miles are in cold weather.

Fig 4

Not Use Of Sophisticated Technology To Highlight # Miles

Using this average driving cycle, we can now derive partial derivatives (influence coefficients) for the effect of AER and ICE cycle efficiency on fleet fuel consumption.

Figure 5

Just 5 More Miles Of AER Makes A Big Difference

Figure 5 shows that adding only 5 miles of AER has a HUGE effect on fleet fuel consumption equaling a whopping 36% savings in fuel.

How does this compare with a more efficient range extender? Often discussed is a turbo 3 cylinder for Volt Gen 2. It is expected that the turbo 3 would have approximately 10% better cycle efficiency than the current Volt ICE.

The comparison of the influence coefficients is presented in figure6.

Slide 6

Demonstration Of Better Use Of Resources To Provide More AER Than Engine Efficiency

Five more miles of AER decreases fuel consumption by 36% while going to a Turbo 3 cylinder decreases fuel consumption by only 10%. The influence of AER is nearly 4 times as great as the influence of the Turbo 3.

Keep in mind that one of the goals for gen 2 Volt is to reduce costs. GM’s turbo 3 undoubtedly will be a pricy piece of equipment compared to the current 1.4, 4 cylinder. Is this costlier range extender justified? I say no. One would be better off by increasing AER instead.

But you say: “How much does another 5 miles AER cost? Batteries are exensive. Wouldn’t it be cheaper to go with the turbo 3 than with expensive batteries?” Again I say no. The cost of another 5 miles AER is zero. All we do is switch to Spark EV chemistry which is more robust and has a higher cycle life. We increase DOD to achieve the added 5 miles of range. Spark EV DOD is 80% versus 65% for the Volt. That is a 23% increase and it is worth an equivalent percentage increase in AER of 9 miles. Spark EV battery article found here (http://gm-volt.com/2013/08/02/spark-ev-versus-volt-battery/).

A more expensive range extender is not justified.



Volt Gen 2 With Smaller Range Extender/Single Transmission Is The Way To Go

Volt Gen 2 would benefit from a smaller, lighter pure series range extender. Not only do we save money on the range extender, we save money on the transmission. We can eliminate the costly 2 mode transmission we have now.

We could have a Gen 2 Volt that is:

  • Lower cost
  • Lower weight
  • Higher performance
  • More Interior room

It is hard to argue against that combo.

Categories: Chevrolet


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51 Comments on "Op-Ed: More All Electric Miles Equal Less Range Extender Need For 2nd Gen Chevrolet Volt"

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George, nice work -as usual. I would proffer that GM’s only approach to eliminating the transmission would be to adopt the 3 cyl turbo with its lighter weight, higher power output at lower RPM and higher efficiency. GM is simply not going to regress on charge sustaining MPG. But GM will gladly swap the incremental cost increase for the 3cyl for the large cost savings by eliminating the expense of the volt transmission and possibly switching to the Spark EV transaxle.

Now as to adding battery range. With the new cathode materials being produced and such a large reserve in the current volt, I feel that the new volt can easily be accommodate a 50 mile EV range. It will basically involve just GM deciding after testing, that less reserve is needed in the pack.

The ultimate goal the 50 miles EV and 50 mpg charge sustaining could easily be realized and allow another $5k price drop in MSRP in the new Volt. Ultimately, I am confident that GM is working hard on the new platform, and I cannot wait to see if our design guesses are realized.

Unfortunately George work here, no matter how nice, is completely undermined by the flawed reasoning and incorrect math on which it rests.

By George’s erroneous logic, increasing the AER to 50 miles would result in 0 gas used — great, now we can just ditch the range extender! i-MiEV for everyone!

Guesstimating from the histogram, those 5 extra miles might reduce overall gas use by very roughly 10% — so in the same ballpark as ICE efficiency improvements could bring.
(and that’s assuming people don’t change their driving habits as a result, e.g. driving slightly less efficiently or doing without that opportunity charge because they see they have more electric range left).

Oopsie, suddenly we have to revise the conclusion…

Great post George.

I agree that attacking the DOD on the Volt battery is the most cost effective way to bump up the AER. In thinking about the Voltec 2 drivetrain, I would strongly consider that it will be packaged for a VoltUV also.I wonder if the battery and motors will be the same but the range extender will be sized according to vehicle weight?

I like the target for 50 AER and 50 mpg for the Volt as Taser mentioned above. I would also put the target of 30 AER and 30 mpg for the VoltUV.

I agree with this piece as well. I honestly don’t see GM dropping the transaxle they’ve spent so much money developing. However, if they were to be able to achieve 60 miles AER or more, there really is no need for it. They’d be better off using the smallest, cheapest range extender possible. Once you have enough range to get into Leaf territory, the range extender becomes more and more for just emergencies. Thus the fuel economy is not as important. I’d be happy with 30 mpg as long as I had that higher AER so that I’m rarely using it. My only requirement for the range extender is that it enables me to drive at least 75 mph steady speed on the interstate.

I don’t think the transaxle has much incremental cost in the long term. Remember that it not only allows the ICE to directly connect to the wheels at highway speeds, but it also allows the generator to be used as a second motor for better acceleration. If GM got rid of it, for equivalent performance they would need, in its place:
-a bigger drive motor
-a single speed transmission
-possibly a second fixed gearing for the generator
They’d get lower range extended fuel economy as well. Overall, I seriously doubt that they’ll save much, if at all, and it’d be a marketing problem in several ways.

The R&D is a sunk cost. Maybe others don’t want to go through that expense because they’ll have lower volumes and need to catch up, but GM should leverage the suitability of their technology to the short term, where batteries aren’t cheap and consumers care about charge sustaining MPG.

I do not believe they can use both motors for additional acceleration. They can use both motors together to lower the RPM of the main drive motor for additional efficiency, but that is because the second motor is spinning in the opposite direction. I’m pretty sure all acceleration comes from the one main drive motor.

You can only deliver power to the wheels while spinning the second motor if it is also applying a torque. That means power is being transmitted.

That would be true of a Prius, but the Volt has clutches to solve this problem. The main drive motor can spin without the help of the second motor. Its called “one motor EV drive” in volt-speak. The second motor is ONLY used as a generator or as a means to slow the RPM of the primary drive motor, in which case it is called “two motor drive.” This mode actually has LESS acceleration capability than the one-motor drive because the second motor isn’t big enough to completely offset the power of the first motor. So when you floor it on a Volt, it will have to switch back to one-motor drive to give you extra boost of power.

Your post above was talking about the second motor spinning, not when the clutch was engaged. The second motor is indeed putting power to the wheels jointly with the main motor.

Still, I concede that you’re probably right about the generator not being used during heavy acceleration. However, this isn’t a limitation of the technology, and merely due to choices for the Volt alone.

You can add a reduction gear between the engine/generator and the ring gear, or do a swap attaching it to the sun gear and the motor to the ring, change ratios, have a performance version where you make the second motor more powerful instead of the first, etc.

There is a fundamental fallacy in this kind of argument. It makes a good point, but draws an incorrect (implied) conclusion as a result of it. The power of the ICE is independent of whether you can drive, 30, 40, 50 or 60 miles on electric. It all depends on how much power you want after those 30 or 60 or whatever miles are over. That doesn’t change whether the electric miles are 30 or 60. If I’m driving to Vegas, do I need a smaller ICE if the electric miles are 50 instead of 40? No. It’s the same. The ICE can and should be made more efficient (less expensive) regardless of whether the electric miles are 30 or 60 miles or anything else.

I agree. The really great selling point of the Volt is that when you run out of charge you can continue to drive on gasoline without any performance loss. I personally don’t know why GM can’t just increase the battery pack a bit and add a simple range extender (ala BMW’s i3 or the Fisker Karma). Didn’t they even supply the genset for the Fisker, which has a 250 mile gasoline range but always stays electrically driven? It seems like they built the Volt drive train to placate somebody’s need to have a transmission.

I think GM just didn’t have a cheap, efficient, reliable low power engine ready. BMW had a refined 2 cyclinder on hand from its motorcycle lineup, and even they are saying that it’s not mean to be used much in the i3. Also, the Karma’s engine wasn’t very efficient, and it took a lot of flak for having low extended range MPG. The Volt continues to take a little heat for being “only” 40 MPG, even though those in the know understand that it’s rather irrelevant when only used for <30% of the miles driven.

I'm hoping that some company offers a cheap REx in the coming years. Tata Motors builds a whole car with a 28kW engine for $2500. Surely they can sell a 25kW REx for <$1500.

But the transmission is far from useless. In addition to solving the marketing issue mentioned above, continued refinement of the technology will let them use power from the main motor, engine, and generator (used as a motor) to deliver power to the wheels for passing acceleration. Once they cost-optimize it, it'll be a solid advantage for them on several fronts.

I think you missed the point. The point is, why spend a ton of money developing a better range extender that gets 5mpg better efficiency than the one you already have? If you can increase the electric range to the point that the only time a person will use the range extender would be on trips like you describe, then the fuel economy becomes less important.

For example, in my Volt I rarely use the range extender at all. I used it this weekend for the first time in a year because I took a trip to another state. I got around 36 mpg (because I was doing 85 mph the whole way there and back) but it wouldn’t have bothered me that much if I had only gotten 26 mpg instead. Because I know that these trips are very rare and thus what is important to me is how the car drives on my daily use pattern.

Respectfully, I think you miss the point that the Opel 3 cylinder turbo is being produced now, so there is no “ton of money” being spent designing one from scratch. The voltec system is modular in nature, allowing it to easily adapt to different range extenders.

Isn’t GM planning on using that 3 cylinder in other cars as well? The Volt-specific developmental cost should be minimal.

In theory I agree with everything you wrote, but if the Volt got 26 mpg in range extending mode, it would have a big image problem. That may be acceptable for an optional extender in an otherwise pure-EV, but not for the Volt.

I completely agree with Anton. This article assumes that people are buying the Volt without the intention of ever using for extended trips well beyond the AER, and thus if the AER were larger, the ‘range extender’ could be smaller to just cover some extra miles in energy. If that’s true, then just get a Leaf. The reason we got a Volt instead of a Leaf is to be able to drive it long distances when we had to: the second week we owned it we drove to a backpacking trip, which required a one-way distance of almost 300 miles with no chance to recharge, AND going over several passes, one of which had inclines of up to 19% grade… and that particular pass was 20 miles to the top. The volt worked great, but it was using that gas engine to the max the entire way up, supplemented by the battery of course as we were in mtn mode, but even then the battery was not keeping up. The point here is that a weaker, degraded range extended likely would NOT have worked in this situation, and an extra 10-20 miles of battery wouldn’t have helped either. A lame… Read more »

I don’t think you’re right about a 200-mile EV not needing a range extender.

There is probably a market right now for such a car in the Volt’s price range, but if you want to get sales up to a million units per year, you need zero-compromise driving freedom, i.e. fast refueling at tens of thousands of locations around the US.

Interesting article George. My impression is that the next gen. Volt will have both more electric range, and a more efficient range extender engine. And Lord willing, in future generations, wean people off of the gas range extender all together. With that said, I’m liking that Tesla patent for a “hybrid battery” powertrain more and more. I think they are really on to something there.

What about temperature on EV mileage? In the heat of the Summer, I can get nearly 50 miles of EV range on my 2013 Volt, but in the coldest days in January I can only get 25-28. I use very conservative climate settings (much to my wife’s chagrin). And this is Northern Virginia, where we get good doses of both ends of the temperature spectrum. Of course the climate is different all over North America and the world. To get a reasonable year round range, you probably really need to get into the 70 mile range to no longer need an extender. This way you keep that 50 mile daily usage easily in range in the Winter months in the colder climes without the need for additional charges. This is probably what the manufacturers found in their studies. Hence, the Leaf et al. get real world ranges in the 70s. As charging networks propagate, this will become less of an issue. At my office there is a wall plug in the garage that is usually powered that I can re-up at work. But as I said, it’s usually powered, so I can’t count on it (I’ve bugged property management about… Read more »

I had been assuming that the next range extender was going to be the 1.0L engine, just without the turbo parts, this keeps weight down at the expense of some fuel economy.

I agree though that as you increase the AER, the range extender becomes less important, but as Anton noted above, there is a certain performance floor that you have to meet in order to do long distance OTR driving from city to city. The BMW i3 RE doesn’t meet that IMO, its designed to get you home to charge again, not to get you to your hotel in Vegas.

As for batteries for gen 2, a 17 kWh Spark EV-lite battery pack would seem to do the trick, with 13.5 kWh usable for about 43 miles AER. The only question I have is if that small of a pack can generate enough kW to get up and go. Maybe A123 can get one more iteration of improvement in their cells before they end up in the Gen 2 Volt.

The logic seems incorrect to me? If I understand the reasoning correctly, then a 14 mi. increase of AER would result in 0 fleet gallons used. I would guess that a lot of the gasoline used by the fleet is for trips.

Indeed, this math is only correct for the driver who always drives the average miles, not the average driver 🙂

I’m not sure if his logic necessarily implies that extrapolation, but I agree with you that it doesn’t seem sound. I don’t think his use of derivatives is entirely appropriate.

I think it’s better to look at the “CS-Only Mileage” histogram. An extra X miles of range should, in theory, shift this histogram to the left by X miles (assuming one charge per day). You could then integrate the new histogram (times mileage) to get the new total gas mileage.

You are right. Daily driving levels are pretty level up to about 39 miles and then the fall precipitously. The point is that you could eliminate about 36% of the gas that is used by increasing the AER to the peak of distance (not sure if I mean “mean or mode” here) of where daily range where gas is used at all. If you did the derivative of the area under the curve for this, that would provide the answer that the article suggests.

But, it is predicated on the existing Volt design. If the Volt had a shorter or longer AER, the magic number 50 would move shorter or longer.

I expect that when you provide a longer AER, the result will be longer average drives (actually, the 50 mile number appears to have been selected as a most probable value [or mode], not an average). Anyone have the distribution of drive distances for the Leaf or Model S?

GM’s engineers and PHEV fans might consider that the commitment may remain spitefully low for the Gen 2 Volt. What R&D dollars are justified for a base of around 50,000+ cars, on loyalty? They know profit lies in expanding to new buyers. One’s who can’t be told that 70% electric matters, not when they see higher mpg’s on a “competing”, cheaper hybrid. A hybrid whose margins help the seller.

70-80 mph speed requirements, on engine only (or CS), are simply wrong. As AER grows to 80-100 miles, you need less ICE. Going 250 miles today? Punch up charge-“slowdrain” mode, and forget about sustaining 80-100 miles of range the whole way. That’s crazy when the rate the battery goes down could probably get you 500 miles, at 75mph, if you just leave the engine on. Designing a drive trane for the last hundred of a 500+ mile trip is just dumb. If I’m stuck going 55-65 because I use up so big a battery, pitty me. I’d be the first to call out critics who can’t figure this out. Here, I’d give kudos to the i3.

A smaller ICE that either runs in a “pure” serial mode that charges the battery, or a “pure” parallel mode, that powers the wheels mechanically with one gear, would not only be far more efficient when the ICE is running, it would also have several indirect improvements.

For either mode, the ICE is sized and tuned for a single peak efficiency at one RPM. So, the cooling system for this is only needed periodically, and it can be completely closed off, and this can lower the overall aero drag by as much as 10%. A small ICE warms up faster, and running it at a single RPM means that it can be a simple 2-valve design with fixed timing and precisely tuned intake and exhaust tract.

Obviously, the size and weight of the ICE is important, and the stone-simple 1 gear reduction unit is much smaller and lighter, too. The fuel tank and the cooling system is also smaller and lighter.


This sounds and looks good on paper only. Operating at a fixed ideal BFSC island seems to make sense but in actual implantation there is no sound rationale to waste latent ICE torque when power demand is low. So some sort of multi-mode output split solution is still preferred in order to get something for the unneeded fuel being burned.
Those calling for “pure series” are just being silly IMHO.


Yeah, just ask all those diesel locomotives that work that way. Just silly.

Diesel electrics do it that way because it’s basically impossible to make an economical transmission to do the job.

Train diesels pull ~2000 tons with ~4000 hp, or ~2hp/ton. You’d need 20+ gears to start a train with that kind of mass:hp ratio while also hitting 100 mph. Electric motors can be designed to have massive stall torque, so they don’t need any gear at all.

Really great piece as we have come to expect from you George. I also enjoyed the conversation that it is stirring as well. I am inclined to think about the extender as you do but some great points for alternative performance applications have been spotted. I like the BMW i3 approach to less performance in the extender mode but truly some Volt owners like the steady performance all the time. Probably a solid market for both. I look forward to the the gen 2 Volt only second to the gen 3 Tesla.

Another area to increase AER is to enlarge the state-of-charge (SOC) range. The Volt battery has proved to be very reliable and probably will last way over ten years. I personally think that GM over-engineered the battery pack. A SOC increase to 80% from 65% would result in nearly 50 miles of AER (up from 38). Hopefully, improved battery chemistry can also add to this.

On what do you base you claims about the Volt battery’s longevity? Has anyone actually measured degradation rates?

As you point out io, no one knows for sure until we get a few more years under our belt with all EV batteries in the field. Though every manufacturer I’m sure runs their own internal tests. But as Mtn Ranger states, the Volt scores as well if not superior in state-of-charge and management systems as explained below.

Agreed with many others here. Flawed reasoning and flawed statements. The avg driver does not get 300 miles on the Model “S” , and even if he did there are some of us who couldn’t have this as his only car.

The Volt is unrestricted in this aspect. Neither of the trips this summer would have been remotely possible since I didn’t drive anywhere near any superchargers, or even many level 2’s.

50 miles or more range on the volt would be a welcome improvement, as George’s own charts prove. Since many people drive this much per day, and many of us drive this much occassionally, it wouldn’t be a wasted effort.

Oh, My worst mileage during stop and go traffic in February has been 6 miles (full to dead battery), not 25. Using engine heat lessens this bugaboo.

Interesting data George. Of course the larger the data set the more accurate it will be and GM already has a significantly larger source of data than what’s in Voltstats.org.
You can be sure there is a new “target” AER

Also, you’ll have to explain to me how an axial transaxle design can be implemented in an EREV configuration. Do you propose to have the RH axle shaft pass through the range extender ICE somehow??? 😉


Awesome. 5 to 10 more miles of AER and a smaller ICE (like the i3 will use) is exactly where I think the Volt should move to.

But more importantly, I’d love to see GM come out with more body styles with a Voltec drivetrain such as a pick-up, a mini-van, an SUV, etc.

Attention: Saying your Volt is getting 135MPG is inaccurate and misleading.

When I carry around a gallon of gas in my car, I get INFINITY MILES PER GALLON!

Stop neglecting the electric portion of your calculations.

Attention: Your argument is correct if you’re trying to measure energy efficiency. Your argument is incorrect if you are trying to measure gasoline savings.

Yes, there is merit to BOTH measurements.

In the latter case, it only makes (some) sense as an aggregate though.

I don’t think there is otherwise much merit in a number which can vary by an order of magnitude depending on driving patterns and other factors, and is therefore useless to anyone but the driver who measured it.

I think the article misses the point of the range extender. I’d love to have an EV for my daily 100 mile roundtrip commute. I’m in Jersey, a choose-your-power-supplier state, so I’m already on 100% renewable power at home. But with no charging option at work, 35 miles with the Volt doesn’t seem a big advantage over my higher mileage on gas Prius. So I’m personally holding out for ~100 miles. And that’s what I need after many years, in January, in traffic. The problem in the long run isn’t the daily commute, but that other drive. If I want to go out on Friday night, after a day’s commute. Or drive out of range, to my sister’s place, down the shore, etc, A charging infrastructure could certainly help, but it has to be built over time. Requiring a second vehicle on top of an already expensive EV is not the way to expand EV use. Though I would argue that the efficiency of the range extender becomes less important as that shifts from a daily thing to once a week or month. But that might also kill the long term value of the car, as the battery capacity drops… Read more »

The current Volt was designed to compete with the Prius. The Spark EV is designed to compete with the Nissan Leaf. It will be interesting to see how well the Volt competes against the Prius given the recent price reduction. The next generation Volt will need to compete with the Tesla Model S since, essentially the Volt is upscale to most EVs with shorter ranges. The Volt needs to be phenomenal like the Model S. It needs to be roomier, have impressive range, impressive MPGE and gasoline mode MPG. The statistics mentioned are intersting, however; they are based on buyers who bought the Volt, understanding the limitations of the Volt. Clearly GM needs to expand that market, ie….more range and better mpg….I do like the article though.

I dont’ think that is the case. The Spark competes with the Fiat 500e, Honda Fit, Smart ED, Mitsubishi I-MiEV The Ford C-Max competes with the Prius The Ford Focus tries to compete with the Leaf The Ford Fusion and Honda Accord go together as low mile sedans and want to compete wit someone The Volt really is in a category by itself. There are some Volt/Leaf shoppers and you can add the BMW i3 to the list but Volt and Leaf fit two different needs and the i3 is also quite different it has double the range of the Volt and cost about $10,000 more. Both factors make for a significant different market. The Model S competes with no one. There are over 200 ICEs in the US market and currently 14 EVs. Even the 14 have not addressed all of the niches like trucks and SUVs BUT they are working feverishly toward those as well. Still my point is just because it is an EV does not mean they compete. Comparing the Volt and Prius are wildly different beast. The Prius gets great long distance MPG and if long distance is your need that is the car for… Read more »

If the new Volt was as beautiful as the concept on Slide7, it would be an instant success regardless of powertrain configuration.

Most of the changes you have discussed are desirable however, I think you are missing the main point that most buyers will consider. “Do I want to spend this much money for a car that I cannot travel across the country in for a vacation if I want”? I would say NO! Most of my trips are 40 miles or less however, occasionally, I get in my car and take some trips of more than 500 miles per day. I would not pay the high cost for an electric car that would would limit me in this regard. If this were a 2nd car for commuter transport only, perhaps, but as my main vehicle – NO. Please do not get me wrong – I love the looks and performance of the Volt and would really like to have one but only with the full range extender versatility as this would be my only vehicle.

I bought the volt specifically because it DOES have ER, I can’t use any fully EV because of my driving needs. Mostly < 30miles during the week, but I take long trips 200-300+ for the weekend in the hills, and don't have the option of charging.

I like the idea of longer EV miles, but I need the gas motor for some time.


AER does help daily commute. But Volt is designed so it can go coast to coast (unlike the i3 with REx which is NOT designed to go coast. You can, it will just be annoying).

So, the engine needs to be powerful enough to climb the Sierra or Rocky….

I can use a 60 miles EV range with the Volt. I wish GM would allow the user to set the % of charge used. That would at least get the Volt up to 50 miles range easily….

The article indicate 50 miles AER but actually you can see that it is a 75 miles AER that would incorporate the 50% surface behind the top of the bell curve. So, the optimum for a new Volt 2 would be 75 miles not 50 miles. On the range extender side, not a 4 cylinder or a 3 cylinder but really a next generation generator. Something like the DLR Direct Free Piston Generator would be far more appropriate because you get more KWh/gallon, it is more compact and light weight. http://www.gizmag.com/dlr-free-piston-linear-generator-range-extender/27736/ You also don’t have the crank and shaft loses. Best of all you don’t have a circular motion anymore so you don’t need a clutch and gearbox. The DFPG is so much more efficient that even as a pure gasoline vehicle it would give better mpg when making electricity in it from the gasoline and transfer that electricity to a motor connected to the wheels, then when burning the same gasoline into a conventional engine with crank and shaft losses and transmission losses directly to the wheels. The ultimate proof that serial is the way of the future. Parallel is just outdated. BMW knows it and chose serial in… Read more »

Good point on choice of battery options…GM would learn exactly what people want….as did Tesla when they dropped the lesser kilowatt battery….Also, I agree on the free piston generators being developed….its a big change…getting rid of crankshafts and things that go in circles but, its been proven and with fewer things moving, you would think less could go wrong….also, lighter, more efficient, and can run multiple fuels….