I've been playing with a difficult to implement but amazing idea for HAHs. The battery's only source of power comes from either inertia or engine power. I think a little energy diversity will do more justice to the term "Hybrid" than it already proclaims.

The Idea: Why not mount solar cells to the top of the vehicle. Simply attach a bicycle mount on the top of the car but nothing more that the square frame that mounts to the roof. Then Macgyver a solar panel to it semi cosmetically running wires to the batt. If there was a way to augment the computer language to recognize another source of energy (if requred) many improvements could spin off from it:

E.g. Engine off sustained A/C, Optimal battery charge from ignition, Better hwy performance by minimizing charges.

I realize that solar doesn't provide that much power but to the very least it could act as a beefed up battery trickler or just extend discharge times.