Hi GordonThree,
The duty cycle on the Dometic in my RV is 2:3 with the door never opened. The Norcold may be similar. That brings daily usage by just the fridge to around 40 amp-hours per day. Other folks have reported 36 amp-hours per day.
The real answer depends on the particular fridge make and model. One fellow on facebook claims 12 amp-hours per day.
GordonThree wrote:
The instaneous draw for the propane solenoid + control board on my norcold is 2.4 amps. I've never tracked the usage over an hour or day, which would vary on how much food is in there, door openings, ambient temperature, battery voltage, etc.