General Motors briefly showed off the next-generation Chevrolet Volt plug-in car at the Consumer Electronics Show in Las Vegas. GM had said it would reveal the car at the Detroit Auto Show later this month.

What GM gave reporters on Sunday night in Vegas, however, was just a brief glimpse of skin. Journalists only got a short look at the outside of the car. No details about the car were revealed beyond what GM has said previously.

Since the car's introduction in late 2010 GM has sold almost 70,000 Volts making it the best-selling plug-in vehicle in America. In recent years, Toyota's Prius Plug-in Hybrid has come close but has not surpassed the Volt in annual sales, according to market analysts at J.D. Power and Associates. GM is expected to sell about 20,000 Volts this year.

The new Volt will be upgraded in three key areas, GM has said. The battery pack, the gasoline engine and the electric drive system will all be improved.

The battery pack will use fewer batteries so that it can be smaller and about 30 pounds lighter. It will also be able to store more energy than today's Chevrolet Volt battery.

GM (GM) has still not revealed the estimated all-electric driving range for the new Volt. That is expected to be discussed in Detroit. Today's Volt can go about 35 miles on a full charge, according to EPA estimates, before the gasoline engine has to come on to generate electricity.

The car's electric-drive system uses two electric motors, as does the current Volt, but in the new car the two motors will operate together more of the time for improved performance. The new Volt will accelerate roughly 20% better, GM has said. The electric drive system is also more compact. Altogether, the electric drive system, which includes electric motors and gears, will weigh about 100 pounds less than the system in today's Volt.

The gasoline engine, which generates electricity to drive car after the initial battery charge runs out, will also be changed. The new Volt's four cylinder engine will be better engineered for its role as a power generator in an electric car. It will also run on regular unleaded fuel. GM recommends premium fuel for today's Volt.