Can you give us a bit more background as to what you actually want to accomplish? Is this to power your RV, or do you want to keep the lights on and the refrigerator cold when the power goes off? Different needs means different applications.
There are two general groups of charge controllers, PMW, and MPPT. PMW is dirt-cheap but only acts as a fancy on/off switch. Panel voltage must be carefully matched to battery voltage to prevent losses, and actual battery damage.
More expensive MPPT controllers act like a transformer, bringing raw high-voltage solar to exactly the voltage the battery wants to charge at.
Now, getting back to the first question, the smallest systems, maybe running no more than 200-300W, might be most economically supplied with a system with a PWM controller, using relatively expensive 12V panels. Above ~300W you actually save money going with a more expensive MPPT controller but with cheaper-per-watt high-voltage residential panels. Telling us about your application will help us steer you towards the best solution.
