Inverter draw from battery for residential fridge

My residential fridge draws 1.3 amps, 120 volts, when running which is nowhere close to all the time. My battery monitor says my batteries are down to 55% in 8 hours when not plugged into shore power. However, driving down the road they only drop to 90% so I have to believe that the truck hot wire is supplying 80% of the fridge draw. No DC to DC converter is used, just a straight connection.