Most batteries require 14.8 volts (Trojan batteries require) to fully charge your batteries. Most controllers will only get them to 14.4 or 80%full charge. Its not the panels its the preset controllers besides other things like wrong Gauge wire to batteries that waste the volts getting to batteries or charger.
If you are really interested in adding solar there is a lot to read and understand to buy a system that really will do all you need. A lot of cheap and expensive kits are available through dealers and on the net that wont do enough to charge the batteries full.
Buyer be aware. I started reading and learning all you need to install or have installed the right components to get the most out of you money. I asked like you on a site like this and someone sent me this mans address and now I understand it all. He is not selling anything at all, just a great guy trying to help educate us out here through his discovery with solar. link
http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
He has written so much about the subject and their is a lot of reading on his site, but like me you will become fully educated on how to live off the grid with 2 panels (320 watts) 2 batteries ( 6 volt) and never run out on power. Don't get ripped off by dealers selling you short on what you need. Be an educated buyer.