Simple solution, doesn't cost anything. Turn on all the house lights that run on 12 volt DC power. Then simply unplug your camper from shore power. If the brightness of the lights drops or dims, your batteries are not charging fully. Leave them on a few minutes. If they noticeably continue to dim over the next 10 minutes, your battery is failing. Plug in shore power again, if lights all brighten up immediately, you'll know your batteries are not charging fully. Where the problem is, is another topic for discussion. But this is an easy, easy way to determine if your battery is charging fully without the aid of any devices.
2019 Montana High Country 375FL Fifth Wheel
2014 Chevy Duramax HD 6.6 - 3500 Diesel Dully Long bed Crew Cab