CO/Smoke monitors will drain the battery. Mine didn't come with an isolator switch, so I installed one. Pretty easy, but yes your rig will drain out without disconnecting the battery.
After three ruined batteries, an inept RV service and $400 in labor with the problem not corrected, I finally traced down a blown fuse in the coach battery disconnect at the solenoid. Even though that corrected the problem, I installed a manual knife disconnect on the coach battery and use it every time I store the coach.
]
__________________
Stan, Shirley & two Schnauzers, 2014 Itasca SunStar 35F
Last winter my battery was drained by the "mirror heater". Which I never used while traveling but some how got turned on at the dash. Once I figured out it was in the on position, it made sense the battery would be drained over night.
After freezing All RV batterie including engine battery I bring a 100 watt solar panel and clip alligator clips to a positive terminal and ground on any metal part on chassis or frame no more concerns obout dead batteries. Just clip on and point it towards the sun. I also use them on all my vehicle if they are sitting for
Over a week without being used. I have a smaller on not sure on watts but about 1 square foot . I just plug it into a live cigarette plug in and it feeds back to the batteries. So much electronic and most vehicles have draws.
Best Regards
Joepeas