Luxury carmaker Rolls-Royce Motor Cars, a unit of German auto giant BMW, said over the weekend that it had developed a fully electric-powered car, but did not say when the model would enter production.

Rolls-Royce said the prototype, dubbed the 102EX and based on its top-end "Phantom" model, will be put through various tests during 2011.

The normal Phantom is powered by a 6.75 liter 12-cylinder engine, at least three to four times the size of the engine on a typical family sedan, and gets about 14 mpg.

Rolls-Royce said it will display the prototype at the Geneva Motor Show on March 1, but said there are no immediate plans to develop a production version.

Rolls-Royce says that the 102EX is &34'a one-off, fully electric powered Phantom,&34' which it plans to show off at the Geneva Motor Show next week.

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