If trickle charging is fast enough and the goal is to avoid dragging a battery between your yurt and where you can plug into AC, almost any panel will do. If you want more than a trickle charge, a 120W panel will recharge your battery in a day, or 30W in 4 days, roughly.
Get a cheap solar charge controller to avoid overcharging and don’t drain the battery too much.
If you’d like a better estimate, tell us 1) the number on the battery labeled amp hours or Ah; 2) what you power with the battery (e.g., lights, TV, notebook computer); 3) how long you use each item per day.
(Stop reading here to avoid mental hibernation. 
For solar geeks: Assuming 12V, 100Ah, 50% discharge, 5 hours/day standard insolation, no load during recharge.)
Ana Douglas
