Driving the Nation has a video clip from a GM presentation about the different operating modes of the Chevy Volt, explaining how it switches between electric motor, generator, and gas engine. All three components are in-line with each other, and this makes for a number of different power combinations that the vehicle can use. For example, at highway speeds, up to 100 mph (161 kph), the generator can be used as a second electric motor, allowing lower RPMs to drive the car more efficiently in a high-speed, all-battery mode.
But, in certain circumstances, it does appear that the gas engine is directly connected to the generator and, at the same time, is helping provide torque to drive the wheels. This has become a point of controversy in some circles, raising cries that "GM Lied" and that it is just another hybrid, rather than an electric vehicle.
What is more compelling for us, is that the engineering is based on what works most efficiently, rather than trying to achieve some kind of rhetorical purity. As one commentor to the Insideline discussion noted, "I actually see this as an improvement over the 'original design.' Remember when everyone was stating how driving through a generator (once the batteries die or at constant speed) is less efficient than coupling directly to the ICE - here you go. Probelm solved by a simple clutch."
We see the primary issue to be one of making a very efficient vehicle, rather than insisting on making it solely electric drive. The Volt might not be perfect for everyone, but if it makes more engineering sense for the Volt to use gasoline engine torque in rare instances at high speeds, we do not see that as a failure at all. The category matters less than the developments that it offers.
written by Asaf Shalgi, November 23, 2010
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