I wonder why so many people think the weight distribution isn't perfect already. The only reason I can think to move the battery forward is to reduce the rotational inertia of the vehicle as a whole, but I would also try to move something in the front of the car rearward to keep the balance the same as it is now.
Its situated behind the driver and passengers seats smack bang in the middle. Its covered by a silver box with a Lotus badge on the front that can been seen between the seats. Perfect balance.
You can just see the badge here..