I've studied these cars and it's a great idea. I was wondering why these companies don't have two batteries and trickle charge when one battery is being used. All you would have to do is set alternators on each wheel. The momentum of the wheels moving would be able to charge the secondary battery. The on-board computer would shift from one battery to the other when they drop to a certain %. It wouldn't be a perpetual self charging system; but you would get increased mileage and more efficiency for your charges.
Does the Tesla not use that energy in some form? For some reason I thought it did, but I could be mixing that up with something else. What do you mean about 2 batteries? Doesn't the Tesla have a ton of small batteries already?
Yes Tesla does that, but its in one large battery. You would need 2 of these batteries to work like this. Tesla is the closest thing to optimal performance for the battery. I just think adding more alternators to generate a larger amp would make things work more efficiently. Also, the power drain makes charging that battery much less efficient. If you have a battery that isn't being used, it can charge much easier.
by using the alternator to charge the battery, you probably would create drag in your car. But I only know the general physics, not the real world physics involved in a car. Hybrid vehicles do this though when breaking and slowing down.