Volt Birth Watch 129: Extended Range Explained. Or Not.

C. Douglas Weir wrote GM about the Chevy plug-in electric – gas hybrid Volt’s extended range feature. GM wrote back. First, Doug…

My confusion is the issue of what, exactly, happens as the range is exhausted for battery-only propulsion. I keep seeing the phrase: “a small engine-generator creates additional electricity to extend the range of the Volt several hundred additional miles” or something to that effect.

So, what exactly does this mean? Is the performance of this small engine-generator adequate for cruising down interstate highways and up long steep grades? Does the Volt become underpowered with this out-of-battery charge scenario? Say you were driving a couple hundred miles to the mother-in-law’s and you own a Volt and a G-6. Would the Volt be left at home because it would be unpleasant to drive in extended range mode? Or would it drive just fine on the small motor-generator with performance similar to a standard small four cylinder midsize car?

Also, the wording implies that the drive train would remain electric, with the motor-generator producing enough current to power the electric motor(s) through or around the battery stack. So is it correct that there is no direct drive from the engine to the wheels…rather it is a serial hybrid like a diesel locomotive when the battery is exhausted?

I hope you can clear this up for me. Any added information would be much appreciated.

Answer after the jump.

Hi Douglas. Thanks for the inquiry. Let me explain in simple terms. For more detail, check out media.gm.com/volt and look in the Technology tab. Lots of info there.

The Volt has two modes of operation – EV and Extended-Range. The engine generator seamlessly operates when the energy level in the battery is “depleted”. Although the driver will see the battery as empty, energy in the battery is really sustained or held in what we call a “buffer zone”. Think of it like a home generator when your power goes out. It starts to create additional electricity to power the car hundreds of miles. The electricity is fed to an electric drive unit, which powers the car. There is no mechanical connection between the engine generator and the wheels. As long as you stop and refuel the generator (like in any conventional car today), you can drive from coast-to-coast until you can stop and plug-in to recharge the battery. As far as performance, there is no compromise when in Extended-Range mode. The battery and engine generator work together when peak performance is needed most, such as driving up inclines.

Hope this helps.

Dave

Dave Darovitz