While the electric Tesla Model S is taking a long, hard road to production, there are a few signs that things are moving in the right direction. A prototype was spied in Michigan, USA, while being taken for testing. Compared to the concept we saw in 2009, the production model has several differences. In front, the main grille opening has been almost totally closed off, perhaps in favour of aerodynamics. The lower grille openings have been redesigned and a pair of intakes have been added at either end of the bumper. The headlights also appear to be toned down from the concept. Due to start production in the middle of 2012, the car will draw its power solely from a lithium-ion battery pack. While the lower-end model should be able to travel about 240km, the more expensive car should have a range closer to 480km.