Californian startup Tesla Motors [NSDQ:TSLA] is nearing the final phase of development for its groundbreaking Roadster electric sports car. Several second-generation prototypes were displayed recently at a press presentation in the automaker's home state, and the next step will see ten more prototypes constructed in the U.K. by Lotus (the British firm provides the basic chassis for the cars) that will include the final specifications for the car. These vehicles will then undergo final testing before production starts in the following months.

The only major difference between these latest prototypes and earlier versions is the addition of Tesla’s latest series of lithium-ion batteries. In the Roadster, the batteries alone will weigh up to 900 pounds and the car’s curb weight is expected to total 2,600 pounds, 600 pounds more than the Lotus Elise on which it is based. With an estimated 248 horsepower on tap, the new Roadster is claimed to accelerate to 60 mph from in rest in around 4 seconds.

In preparation for the new model, Tesla has expanded its operations in the United States and is now in the process of promoting the vehicle in key cities including Chicago, Los Angeles, New York and San Francisco. But if you’re interested in purchasing one, you might have to wait a while. Tesla has already pre-sold 375 Roadsters at $92,000 apiece, and the first deliveries won’t start until the middle of the year.

Soon, focus will shift to Tesla’s upcoming sedan model, codenamed WhiteStar. The vehicle, which is rumored to be similar in size to BMW’s 3-Series could be produced at a new plant in New Mexico but it’s still some years away.

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