Solar in the woods is a waste of money. You get zip no matter how many watts you have.
In the situation, IMO just take the 2 batteries back and forth to home/cabin. Same routine at the cabin for partial recharges, but now at home get them to full and leave them on a maintainer charger.
I use this Can Tire one that works great and holds at 13.4v forever, so it is a perfect Float charger. Often on sale at half price. Watch the flyers.
http://www.canadiantire.ca/en/pdp/motomaster-eliminator-intelligent-battery-charger-2a-0111506p.html#.VFAfGGd0xjoBTW don't get any solar anything at Can Tire! They want at least twice what they ask at proper solar places.