Check the top of the battery, many have little date codes so the day of purchase can be marked by removing parts if the sticker to include the month and year.
If its getting up in age (5+ years) it could be the battery.
You can also check the fluid levels in the battery and add distiller water should it be low. That could cause issues with charging and holding a charge.
Also, batteries plus may be correct but many campers (most actually) have 3 stage charging. 1) bulk charge - most powerful 2) absorption - moderate and 3) float charging - trickle or maintenance charging.
2011 FR Rockwood Premiere A126 Hard Side
TV=2011 Jeep Wrangler Sahara 2 Dr
Reese 66065 WDH, Curt WDH Shank #17120
Prodigy P2 Brake Controller, Mopar 7-pin Harness
B&M Transmission Cooler (#70268)