I anticipate having to park often in an overnight tiedown with no access to electrical in the Northeast where preheat is a must. I'd love to use my Reiff system rather than buy another (like the propane powered Dragon). Anyone have experience running an electric preheater using a battery and inverter? With some quick math, my reiff oil sump heater is 200W and the low-end deep cycle marine batteries are 80 amp hours at 12V. Watt=Amp x Volts so 200/12 = 16.7Amp and 80 amp hours / 16.7 amps = 4.8 hours (assuming constantly on). Seems like that would be long enough to give a decent preheat (although overnight would be difficult).
Any thoughts?