Our approach was different, I fit the panel to the space available on our large teardrop trailer and it is a 185W 66 cell high voltage panel. This dictated a MPPT controller. This combination produces usable current from sun up to sun down in shaded camp sites where a nominal 12V panel is impacted much more heavily by shade or bad weather. Our trailer however was designed with boondocking in mind, LED lights, computer case fans in place of a fantastic fan, small LED TV, Waeco 120V AC/12V DC refrigerator...
One rule of thumb is 150W of solar for 100AH of battery.