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Ever since the debut of the Chevrolet Volt concept in January 2007, the arguments have come fast and furious abut whether it is a hybrid or an electric vehicle. Technically, its actually both. There are those who insist on calling the Volt and similar vehicles from Chrysler, series or serial hybrids. This argument seems to come mostly from those who believe an electric vehicle should have nothing but a battery (or other electrical device) on board for energy storage. Certain proponents of parallel hybrid technology also prefer the series hybrid moniker, since it implies that the system is not that much more advanced than current production systems.

The counter argument from General Motors and others is that this drive architecture is more accurately referred to as a range extended electric vehicle. The premise here is that even there is an engine in the vehicle, it is not connected to the wheels and only the electric motor(s) provides actual propulsion. Let's take a look (after the jump) beyond the semantic argument at the actual technology that moves cars like the Volt.

Let's step back for a moment and consider parallel vs series. By definition, parallel lines are always the same distance apart and moving in the same direction. In a parallel hybrid, two (or conceivably more) power-plants can each provide a torque flow path to the drive wheels. Either power-plant can provide torque to the wheels independent of the other (read more on parallel hybrids).

In a series architecture, multiple systems feed into each other in sequence with only one connection to the end point, namely the drive wheels. For example an internal combustion engine would drive a generator that produces electricity. That electricity could feed into a battery which would then drive an electric motor to propel the vehicle. The engine doesn't directly drive the wheels through a transmission the way it can in a parallel hybrid.

Series hybrids are nothing new and, in fact, the very first hybrid used this configuration back at the beginning of the twentieth century with the Lohner-Porsche. Since the 1920s, the most common series hybrid application has been railroad locomotives. These machines use a diesel driving a generator which feeds the motors that drive the wheels. Automotive applications add a battery to the mix.



Depending on the size of the battery, the vehicle may or may not have any zero emissions range. A series hybrid with a small battery could run the engine at constant speed in its most efficient range. The battery could then be used to store extra energy from the engine at light load conditions or from regenerative braking. When extra power is needed for acceleration, the battery can provide this.

Going to a larger battery with plug-in capability can allow the vehicle to operate in zero emissions road for some period of time dependent on the capacity of the battery. A compact car like the Volt with a 16 kWh battery can operate for up to 40 miles without running the engine. In no case does the engine ever send drive torque directly to the wheels. This particular configuration is what GM and others are referring to as ER-EVs.



There are downsides to the series hybrid layout. Having a vehicle operate with an engine running at constant speed can get the best efficiency out of that engine. However, a series hybrid has multiple energy transformations. Every energy transformation involves some losses. A conventional mechanical geared transmission, is generally about 95 percent efficient transferring energy.

Going from an engine's mechanical energy to electrical energy will produce some loss depending on the efficiency of the generator. Similarly, there are losses in a battery as it heats up when being charged. There are also losses going from the battery back to the drive motor. Of course, some of this is offset by recapturing kinetic energy through regenerative braking and the previously mentioned engine efficiencies.



The real benefit comes from having that larger battery that gets charged off the grid. If an ER-EV is operated without plugging it in, it will likely not get any better fuel economy than a conventional similar vehicle. If however, the vehicle is operated largely within its electric range and then plugged in, the reduction in fuel consumption, even when the grid energy is factored in, can be huge.

So,is the Volt an ER-EV or a plug-in series hybrid? Both, really, but who cares? It doesn't matter as long as it works.



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  • 29 Comments
      • 6 Years Ago
      I think I would prefer a Genset Trailer (assuming I had a place to plug in and recharge).

      http://www.zoomilife.com/2009/01/22/genset-trailers-an-answer-to-electric-vehicle-range-issues/

      I figure with a BEV with a 60 mile range. I could cover 98% of my usage, only really needing more when I leave town. At which point you rent a genset trailer from your local dealer. Or I guess you could just rent a normal ICE car for longer trips.

      If I go electric. I really like the idea of dumping ICE maintenance entirely. Rent the range extender or renting a gas burner would probably be a preferable option. Especially if it brought down the price significantly.
      • 6 Years Ago
      Well, it seems like everybody is fooled by scientists who doesn't understand how market works and businessmen who have no clue in science.
      Tesla, Fisker, Volt... all will fail. Because they were fooled. A battery is not advancing that fast as Ellon Musk assumed. Bob Lutz didn't know that Ellon Musk's assumptions were so far from reality. Fisker draws beautiful cars, but doesn't mean he will invent something better than Volt and Tesla.
      harlanx6
      • 6 Years Ago
      By the time this thing hits the Market it should be wearing the Cadillac badge. That way people who can afford it won't be ashamed to be seen in it.
      • 6 Years Ago
      "Ever since the debut of the Chevrolet Volt concept in January 2007, the arguments have come fast and furious abut whether it is a hybrid or an electric vehicle. Technically, its actually both."

      ...er, if something is "both", isn't it then, by definition, a hybrid?
      • 6 Years Ago
      I am sorry but until there is a real need for this development we are wasting money and generating a huge carbon cradle to grave issue with all these products (Recycling generates a carbon foot print also). I am sure they will not last as long as the 1971 vw beetle convertible (33mpg) that I own along with my Old Firebird (10mpg at the drage strip)and a F250 crew cab turbo diesel (17mpg). All my vehicles are tuned to perfection and ulitmately do not require much in the way of natural resources. You see I am for new development to get us to the next level but it better without the biased and I might add twisted moral/ethical code that many of the hybrid / full electric guys are pushing down our throats. If we make ignorant laws that do not allow people to have a dark colored car because they take more energy to keep cool then the next step is no a/c at all. Then it is logical that we ration use or do away with personal transportation at all for the masses. Please understand that the makers of the laws and the people pushing these agendas will still need their planes, and automobiles but you should just be quite for we are the only people smart enough to protect you from yourselves. I don't don't buy it for a second, I use my cars wisely and when they have truely good and cost effective alternatives I will then weight the issues and maybe they will meet my needs.
      Sorry for the rant but the lunatics who bitch about my work truck just do not understand that the technology is just not there yet and to act as though noone should have a need for a large vehicle is just ignorant.
      • 6 Years Ago
      Stop ! already with cars that you half to be a contortionists to get in . The American population is getting older and bending is the pits. And who in the hell chanded the door hindges on all the doors and called kid safe! Nothings safe if you are a clutz !
      Good car design was the 1934 Ford two door as all the modern cars look like beer cans with different lables.
      Capt. Billy~ Sailor~
      • 6 Years Ago
      it's a hybrid because it uses two different forms of fuel , although different from a prius. you can deisgn simpler like the apple ipod then it'll be cheaper so get rid of the volt and get the ev1 back on the road
      • 6 Years Ago
      We used to think the same until we heard people at Dodge stands looking at the Dodge EV, now the Circuit asking where the gas engine was. The Dodge folks kindly reminded them it was an EV. But people would answer that GM's Volt is also an EV but has an gas engine. They were confused by the fact GM called its hybrid an EV since it used a series plug-in hybrid layout.

      We feel it is stretching the definition calling it an electric vehicle with an extended range. It's like those detergent commercials that wash whiter than white. What is the color for whiter than white? It's a plug-in hybrid, why not call it an S-PHEV, where S stands for series and the marketing department could turn it into Super! Super PHEV, now that has a ring.

      We feel it confuses the acronyms already in use and apparently people are getting confused. Plus, it seems that GM is spending some of that government tax payer money by lobbying governments to make sure ER-EV is a recognized acronym. Indeed, who cares? Bring out the car instead.
      • 6 Years Ago
      For the Volt, the engine is present primarily to compensate for the limited range a practical sized battery currently has.

      On a hybrid, the not only is the system restricted by battery size but by the operating range where the engine must run.


      Battery limits aside, the amount time the engine must run on a Volt for most driving conditions will be tiny compared to its hybrid competitors.
        • 6 Years Ago
        LaughingMan: That's an argument for ditching the electric-only capability altogether and running the engine constantly. That way it's not dead weight. Should lower the overall cost too, as those batteries are absurdly expensive.
        • 6 Years Ago
        Yes, but the fact that the engine is run so little, yet still weighs as much as as a 1.4L engine in a small car is troubling. That means that the engine will be little utilized, but will weight down the car even though it's hardly ever used.
      • 6 Years Ago
      An inefficient engineering idea?
        • 6 Years Ago
        The automotive world isn't really about efficiency or ecological superiority. It's about pleasing the public.
        • 6 Years Ago
        It's actually about making money. Sometimes that means convincing the public that what they want is your highest profit margin product (ie trucks and SUVs).

        I don't think there are a lot of people begging to increase their risk of dying by cancer, but the cigarette companies have done a great job of product placement and making a horrible product that few people would otherwise want seem cool. Most consumers don't know what they want, they're told what they want.
      • 6 Years Ago
      The profit contribution per car of the series hybrid has to be greater than a parallel hybrid.
      When will an auto maker sell a series hybrid without its range extender battery charger? If we dont need it for 80% of our trips how about a plug-in one? I should be able to go to Wall Mart and but one for $600 if and when I need one!
      • 6 Years Ago
      It seems like the weight and cost of the ICE in the ER-EV is critical. Volt1 can be a success with a 1.4L engine, but if they are going to get this to work as efficiently as possible, the Volt2 will probably have a high performance engine that is significantly smaller than 1.4L. But even so, until battery prices and sizes drop significantly, the ER-EV will be the better idea. But if LiIon batteries drop to less than $250 kWh installed with a pack management system, then it will make more sense to go with a BEV. On the 10% of the days you use more than the AER, you will still have fast charging to fall back on. The problem with assuming battery prices will continue to drop rapidly is that the low hanging fruit have already been plucked, and further drastic improvements are going to be increasingly difficult to achieve.
      If GM survives long enough to build the Volt, it will be a huge success for the first few years, giving Chevy 2 nameplate cars, the Volt and the Corvette. The tough part will be getting enough economies of scale to allow the car to be built cheap enough that the Volt2, the Orlando and the Cruze will be able to sell ER-EV versions without too great an increase in cost over traditional ICE cars, especially if the government allows the federal tax credit to run out. Eventually the Silverado will probably have an ER-EV version, even ranchers & builders will need to cut gas useage when it gets up to $4 or $5 a gallon.
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