• Feb 15, 2008
Fans of hybrid vehicles have been clamoring for carmakers to add plug-in capability to those models so that they can grab some juice off the grid and leave more in the tank. The problem is that making a useful PHEV is actually not as simple as just plopping in a bigger battery pack and some charging circuitry. Current hybrid models are only designed to run on electricity at light loads and relatively low speeds. At higher speeds or rates of acceleration they operate in a blended mode with both the engine and electric motor running. This of course is still beneficial because it means a smaller less powerful engine is required to meet customer performance expectations while saving gas.

In the real world, PHEVs need more electrical power from the motor in order to actually go farther without starting the engine. A new study done by General Motors using real world data recorded from over 600 cars analyzed how standard and plug-in hybrids would perform in the hands of real drivers. What they found was that to get a real benefit the vehicle needs to be designed to perform at all speeds on electrical power alone. With that much electrical power on board, having a full engine to drive becomes redundant. A small engine to charge the battery however makes sense. An extended range EV (like the Volt) would actually eliminate 70-percent of the engine starts at any time during a drive. AutoblogGreen talked to GM's Pete Savagian about the study and the results.

[Source: General Motors, AutoblogGreen]


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  • 29 Comments
      • 6 Years Ago
      This! is a statistic. Much as a drunk uses a lamp-post, statistics are mostly used for support, rather than illumination.
      • 6 Years Ago
      Ignoring the issue, but man, whoever designed that bar chart doesn't understand how to graph.
      Carlos
      • 6 Years Ago
      What I've never understood was why no one has done this before? It's a simple basic concept, run an engine at a constant speed at it's most efficient rpm to charge the batteries when needed and when it's not just run off of electricity.
      • 6 Years Ago
      Because batteries are large, heavy and expensive and the control system is complex. It is only practical with significant advances in battery technology that are just now being realized (we hope).
      • 6 Years Ago
      Large construction vehicles use a diesel generator to power electric motors. I think the approach makes sense for road cars, too, given this data. Hopefully the constant power source would result in a much smaller battery, only to be used as a power reserve during acceleration. That would result in lighter, smaller, and better handling "green" cars, although the two motors would still be a major detriment.
      • 6 Years Ago
      While they might get some close results just evaluating driving behavior, they don't even have the mules out yet so in real life it might not turn out that way. That's the only thing I'm worried about as besides from some buses series hybrids really haven't been tried that much. And most of those only get like 30% improvement in fuel efficiency. The volt is different in that it has the EV mode and here their studies say that they displace much more gasoline than parallel PHEVs. I still say it doesn't amount to much right now until they actually get some real life data on mules. There's nothing to say that a parallel PHEV with highway speed capabilities can't get much nearer to the gasoline displacement numbers of the series PHEV Volt in real life than in this study.
      • 6 Years Ago
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      http://www.quazen.com/Recreation/Autos/Eco-friendly-Cars.83942
      • 6 Years Ago
      Can this really be surprising to anyone? Isn't it just common sense that a series electric hybrid will save more fuel than a parallel system?

      Thank you for the newsflash GM. Just release the stinking thing.
      • 6 Years Ago
      They are small considering the size of diesel you would need to transport thousands of tons of cargo without an electric motor. True, they aren't hybrids, but their system is efficient and time tested. I think its the CSX commercial that says they can move 1 ton of cargo 423 miles on 1 gallon of fuel, that ain't half bad.
        • 6 Years Ago
        Train engines are the size they would have to be in any event... the electric traction motors on the wheel trucks aren't magic, the advantage diesel/electric has is that it doesn't require heavy, expensive, failure-prone transmissions to transfer all that torque to the wheels. I suppose the engines might have to be slightly more powerful to move what would be a heavier assembly if they had some sort of massive transmission. The % difference compared to the huge tonnage they're moving in addition to the locomotive would be small, though... the real advantage is in the transmission of the power from the engine to the wheels.
      • 6 Years Ago
      The way inflation is going $35K might not buy you a gasoline Aveo by the time the Volt ships.
      • 6 Years Ago
      The battery, the battery is why this has never been attempted. Until recently, it never looked like this could be done because the batteries would have been too heavy. Today, it looks like that hurdle will be eliminated.
      • 6 Years Ago
      im sure a loaded prius is in the high 20s...maybe cracking the 30k mark. alot of the prius you see running around are the tarted up ones alos. i dont think they sell to many base-model ones. if they can bring the volt in at 35k, with remote start and HID lights and all the goodies the prius has they will have no problem selling them. its better looking so ppl that want good gas milage but dont want to look like a nerd while they do it will be all over the volt. good luck GM.
        • 6 Years Ago
        Explain to me why the Volt would need remote start... for heating the interior or something? It should be ready to go when you press the on button, unless it has some lengthy "boot-up."
        • 6 Years Ago
        Actually, according to Edmunds, the fully loaded '08 Prius stickers at $26,900 including destination charge. Average sales price is $26,500 and that's fully loaded with the iPod adapter, backup camera, bluetooth, et cetera. Basic models start around $21k.
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