There is some very good info on batteries located HERE
. One thing I would add up front is make sure that your battery isn't leaking, or has any "moisture" on the outside. This could complete the circuit between the positive and negative allowing a slow discharge.
It sounds to me like you might have something on that your not aware is draining the battery.An example of this, we left our camper alone for a few days last summer, and found the battery near dead. When we hooked up to shore power to recharge, we found that the furnace
had been switched on by accident. The furnace
fan would run at night and try to light
but the propane
was off. When the sun came up, the camper warmed up enough to not "trip" the thermostat.
A "parasitic draw" test should show if you have something draining the system.
With your battery charged, and the system disconnected from shore power, install a test light
in line between the negative of the battery and your ground wire. If the test light lights
, there is something on, or you have a short to ground.