Only two months after declaring its intention to electrify the automobile market with the Chevrolet Volt by the end of this decade, General Motors has declared that the futuristic vehicle is almost ready for testing after the successful conclusion of the design stage.

And what's more, the Volt may not be the only electric car from the GM stable in the near future. Enthused by the pace of development, the company has already embarked on the design of additional models, which may even be sold outside the American home market. (See: General Motors to electrify car market in 2010 with the Chevrolet Volt)

GM still has considerable work to do on the Volt's lithium-ion battery and other technology in the two years before the car is scheduled to go on sale, but completing the design is a milestone for what is arguably the most crucial product in decades for the century-old automaker.

Bob Boniface, the director of design for the Volt, showed sketches of the car and photos of its front and rear corners at an industry conference in northern Michigan. He said GM had made the Volt more aerodynamic and attractive since displaying it as a concept car at the Detroit auto show in January 2007.

The changes, including a shorter hood and more rounded front end, have increased the car's battery range by about six or seven miles, Boniface said. By year's end, GM expects to have 50 prototypes for testing, with the first few scheduled to roll out in the next 10 days.

Boniface also disclosed that more than two other models were at the scale-model stage of development. The Volt design studio, which employs close to 50 people, is being expanded to cope with the increased work. One of the follow-up models will be an Opel for sale mainly in Europe.

GM said last week that it would choose the Volt's battery supplier before the end of the year. Two groups led by South Korea's LG Chem and A123Systems of Boston are vying for the contract.

Frank Weber, who heads the Volt project, said the batteries would have enough power. The biggest challenge is maintaining the cells' stability. "Batteries are like human beings, they like room temperature," he said.

GM has yet to disclose the retail price of the Volt but is lobbying for some form of government subsidy to bring the car within reach of the average Chevrolet customer. However, even with the release date and price unannounced, the car has garnered a lot of interest from the general public.

As of Thursday afternoon, 35,750 people from all 50 American states and 63 countries had signed up on an unofficial waiting list for the car at gm-volt.com, a Web site run by a neurologist in New Jersey who is not affiliated with GM. The doctor, Lyle Dennis, started the site as a fan when GM announced the car.

GM has said it will charge $30,000 to $40,000 for the four-door Volt. Frank Weber, GM's vehicle line executive for the Volt, said that the company did not expect to make money in the near term but that the "E-flex" battery technology will ultimately allow GM to sell a profitable line of ultra-fuel-efficient vehicles.