The design phase of the plug-in hybrid Chevy Volt is “essentially finished,” General Motors declared Thursday. The new design is more aerodynamic than the concept Volt unveiled in Jan. 2007, allowing the car to travel solely on battery power for at least 40 miles, according to GM. The automaker hopes to have a few prototypes ready for testing within the next 10 days, and 50 available by the end of the year. But the 37,333 (and counting) people who have signed up to an unofficial waiting list for the Volt will still have to wait two years, as GM continues work on the actual technology that’ll make the car run. A GM exec notes that the company wants to conjure up “battery packs about half the size, twice the robustness, and half the cost” as exist currently. When the Volt does debut, GM says it will be priced between $30,000 and $40,000.