The Volt is a bit more like a conventional hybrid gas-electric car such as Toyota Motor Corp.'s Prius, however, the current Prius cannot be plugged in to recharge. After the batteries are drawn down, the Volt has a gasoline engine that kicks in to power a generator, which creates electricity to keep the car's electric motor turning. The Volt, like other coming electric cars, has a big battery pack that allows it to travel 25 to 50 miles purely on battery power.
Some are trying to make a big out of the regular gasoline engine 'assist,' even though GM has noted that it did not share all the details until now because the information was competitive and they were awaiting patent approvals. GM never before said there was a mechanical link between the gasoline engine and the drive train. (WSJ, 10/13/2010)