How GM's E-Flex Propulsion System Works

The E-Flex Range Extender

The Chevrolet Volt concept car is the first vehicle to be powered by E-Flex.
The Chevrolet Volt concept car is the first vehicle to be powered by E-Flex.
Photo Courtesy General Motors

Once the battery pack loses its initial charge, it's time for the range extender -- GM's name for the internal combustion engine in the front of the vehicle -- to go to work. On the Chevrolet Volt concept car, it's a 1.0 liter (1,000 cubic centimeters) 3-cylinder engine designed to operate a generator that keeps the battery charged. It runs on a 12-gallon (45-liter) fuel tank.

"On a typical electric vehicle, you've got a battery and an electric motor," said engineer Andrew Farah. "That's everything you need until you run out of your charge… then you have to push it home." With the gas motor on the E-Flex platform, that's no longer a problem, he said.

The purpose behind the gasoline-powered range extender is to have an electric car in which drivers aren't constantly staring at a gauge to see how much juice they have left before they have to turn the car around and head home to recharge.

Despite the effectiveness of the electric motor, drivers must remember keep their gas tanks full. While the car can run up to 40 miles (64 kilometers) on battery power, after that, it needs to have the gas motor running to power the generator.

GM says the average customer should save around 500 gallons (1,892 liters) of fuel each year and almost never need to go to the gas station or maintain typical engine service schedules. The company recommends that the car be plugged in as often and for as long as possible to keep the battery conditioned.

Currently, GM engineers are working to have the range extender be powered by gasoline as well as the E85 ethanol/gasoline mixture. In Europe, they're experimenting with diesel fuel as well. They're also working on a fuel cell variant of E-Flex [source: Farah]. On that vehicle, the range extender and generator would be removed and replaced with hydrogen fuel cells. On a vehicle like that, Farah said, "you'd be running the fuel cell most of the time, and the battery not as much."