Rough rule of thumb for stuff like group 24 batteries, which can be a PIA to get top charged... Set your unit at 14.8V when charging while camping, and I'd set it at 13.4V when you completely disconnect the battery from the camper, but leave just the solar panel connected while in storage.
14.8V camping
13.4V storage
The Chinese are banking on you being cheap, and running thin gauge copper wire from the charge controller to the battery, which will create DC voltage losses, depending on the length of the copper wire run and how close the controller is or isn't to the battery.
Don't be cheap, run fat wire, your battery will last a lot longer running the fat wire and staying top charged like it should