Launched at the North American International Auto Show in January, the Cadillac Converj concept shows off GM's Voltec electric propulsion technology, which enables up to 40 miles of gas- and emissions-free electric driving. The electric propulsion system in the Converj is made up of a 16-kWh, T-shaped battery, an electric drive unit, and a four-cylinder engine-generator. It uses electricity as its primary source to drive the car.