"Fully Charged" always makes my eyes rise as most folks don't really know.
Unless you have removed the battery from the camper for 24 hours and left it undisturbed (rested); THEN taken a digital voltage or hydrometer reading indicating 100% capacity according to the below chart (brown); you have no idea if the battery is charged to capacity.
If you are using the "idiot lights" to determine this, remember that when you use the "battery" button, the top light only indicates the camper (not necessarily the battery) is seeing charging voltage. If both current limiters between the converter and the battery are closed, the lights indicate the battery should be charging.
If you remove the AC power cord, and let the camper sit for 24 hours with everything you can turn off "off"; the lights should reflect whether the battery is charged above 50% capacity (3 lights) or above 90% capacity (4 lights).
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW