Yes the gauges are next to worthless especially when it comes to the battery. And even more especially, a deep cycle battery.
The gauge indicates nothing more than static voltage. That voltage can show full bars even on a battery not up to snuff. It has no way of measuring voltage under load which is how a battery has to be tested. A deep cycle battery will show good static voltage throughout at least 2/3 of its discharge.
On of the earlier posters mentioned pushing the battery test button while operating the slides. That was excellent advice. Load the battery by using the slide pump motor and I'll bet the bars don't indicate full.
2016 Flagstaff 8529IKBS Diamond Package 5th Wheel
Ford F-Series SCREW 4x4
TST Tire Monitor - Sinemate 3500w Gen.
2016 Nights Camped = 44