Hi,
I have a E-meter on my motorhome that can detect all power being used. I use about 0.8 amps all the time to run the propane and CO leak detectors. This adds up to about 20 AH per day, and yes can deplete the battery bank in 5 days, if you add in small loads like the radio memory, ect.
The best solution is a pair of 120 watt solar panels. They will generate about 35 AH daily each, and will keep the batteries full.
SunElec.com Look for a 12 volt solar panel, and a PWM controller.
Fred.