If you are just wanting to keep your battery charge maintained between camping trips, you shouldn't need much amperage. A trickle charger should suffice. However, if you are looking to provide boondock power and recharge batteries your batteries during the day, you'll need much more than a trickle charge. I picked up a Shumaker SP-200 solar trickle charger (2.4A) from Amazon recently (under $28 shipped) and am hoping this will satisfy my needs since I don't plan on doing the hardcore boondocking that many members here are experts on. Here's the info on mine..
http://www.200wattsolarpanel.info/sc...ner-deals.html
http://www.amazon.com/Schumacher-SP-...9581687&sr=8-3