You might want to be a bit more clear about your objectives for your system.
If you hope to provide full of supplemental power for moving your car, then this is probably a pipe-dream; such systems are huge, use thousands of lithium-ion batteries, and cost millions.
If you hope to recharge the batteries on a Prius -- you could experiment with that but the results will probably be nil while the car is moving. Stationary charging stations have been done by a couple of e-car experimenters here.
If you want to recharge a car's starting battery, that's easy enough to do. Take a look at a Harbor Freight catalog.
If you want to install a seperate battery and some panels to run a seperate piece of equipment (radio, inverter, whatever), then you'll need to tell us what you intend to do and how much power you want to draw.
