Take the battery to a auto parts store and have them load test it. Take it back to the dealer with the results and ask for a new good battery...good luck with that.
No it's not normal...as stated above it sat too long discharged on the dealer's lot. Also, one battery is not enough amps for boondocking...two minimum and four is better so you do not pull them below the 50 percent level. Most use 6V golf cart batteries but they require adding distilled water every couple months.
The CO detector should be called a low voltage audio alarm.