I have a single staring battery for the port engine/generator and three deep cycle batteries wired in parallel for the starboard engine which also serve as the house batteries. I have stock alternators, a 60 AMP battery charger and a battery isolator.
The longest I have every gone without starting the generator or engines is about about 30 hours and the voltage had dropped to around 10 volts. The fridge is always on as well as a few hours of TV, DVD and DVR, a few hours of radio, several flushes of the Vacu-Flush, anchor light, various interior lights, coffee pot in the morning, microwave for popcorn (necessity with a movie), water pump (shower, toilet and dishes). I run a 1000 watt (continuous) pure sine wave inverter for the TVs/DVD/DVR & laptop charger which will not operate below 10.5 volts and a 3000 watt (continuous) modified sign wave inverter for the coffee pot, microwave and receptacles.
David & Carol
Charlotte, NC (Lake Norman)
3700 SCR "Comfortably Numb"