I have a marine battery. 500 amps reg temp; 400 amps cold temp. I have been charging it but notice that if I reconnect the charger even after a day off the charger it shows as only 75% charged (even though I charged it to 100%). Is this a sign the battery life is down or could it be the accuracy of the charger? In any case, I guess we'd be running lights occassionally, a night light for the DD at night and maybe the furnace at night. Should a battery last 3 days with that usage? And potentially in the stupid question category...if I run the fridge off propane it will only use the battery for the initial spark, right? If the battery dies and I reconnect the pup to the TV and run the engine, how long would I need to run the tv to recharge the battery?