According to the battery page posted above. A flooded battery will typically self discharge about 1% per day. Depending on ambient temperature.
So yes, as McDenny said, in 3-4 months a flooded battery would be pretty much discharged. That would very likely be true whether it be a deep cycle or a car battery.
On the other hand, an AGM car battery would
likely behave the same as a deep cycle AGM battery and discharge much slower.
Question is, do they even make AGM car batteries? Realizing there have been maintenance free
car batteries around for years. Such as the Sears "Die Hard". Are they AGM or simply flooded batteries that are somehow sealed?
A cheap-o car battery would work fine in a camper that was plugged into camp power, but would likely have a shorter life than a more expensive one. Also IF camp power went out for several hours, and a fantastic fan and light
were burning, the car battery might not do well.
Construction of car batteries and Deep Cycles are different as they have different jobs.
The more expensive and better quality chargers have buttons or switches for selecting Flooded
. According to my "Battery Minder" charger/desulfinator, the 3 types need to be charged at different rates and/or at different cut off points.
The power supply in my 2003 Casita
doesn't give me those options. I don't know if it is a multi-stage charger or single stage. AGMs were not as plentiful in 2003 as they are now. So could the camper charger do justice to an AGM or even damage it?