Furnace/Battery Question

offgrid, you try repeatedly to draw me into these repetitive debates: vehicle brands, WD hitches, trailer wiring, brake controllers, solar power systems, batteries, heating solutions, generators, tires, boondocking methods, preferred camping style and areas, etc etc. What you really need to do is focus on providing answers, and accepting that others will also provide answers, and even if an answer or suggestion is different than yours, unless it is totally wrong or dangerous, then it is a valid answer. Period.

I prefer the cat heater. More quiet certainly, more efficient - I don't know or care in the middle of the night. More condensation - yup - but I don't care in the middle of the night; I do prep for it and accept it. Offgrid can get on your nerves if you let him, but makes some good ponder points, if they are important to you. Others make good points to consider and balance our decisions. That's why I like this forum. Think I'll leave it right here.

BMJ  I can't respond to your inverter question as I have neither generator or solar to supplant my batteries when boondocking but I can state this from 10 years experience with our two 12v group size 24 Interstate batteries that are now 10 years and 9.7 years old:  we get 3 days out of each battery when night temps are in the 40's or less, the furnace runs a lot (yes it is loud but in my book noise Trumps over being cold) and usually the battery will read around 60% S.O.C. or 12.2v after 3 days or going into day 4.  At that point the one battery is unhooked and the other one is attached.  Works for us and we are good for 6+ days without all the fussing of hooking up/taking down solar panels, or carrying around a generator and gas can(s) and don't have to have all the extra room needed to store all this 'stuff' like solar panels, controllers, generators, gas cans.  I like simple and as a result have a fair amount of extra room while traveling (and a lot less weight).

The furnace uses about 2 amps when running it’s fan so if it ran continuously it would consume about 50 amp hours a day, which is about all you’d want to take from a single battery. You also have other electrical loads you will be using so that would shorten the time further.

But the furnace won’t be running continuously unless it’s really cold, a more typical duty cycle would about 50%, for about 25 amp hours a day. So if you have dual batteries (recommended for boon docking) you ought to be able to go two days at least as long as you’re conservative on other electric use.

Consider a second propane cylinder as well. The furnace when running uses 20000 btu per hour, or about 480000 btu over 2 days at 50% duty cycle. A full single 20 lb cylinder contains about 430000 btu so you will probably run through a cylinder operating the furnace before you run through a dual battery setup. Be careful about tongue weight though, dual batteries and cylinders will add well over 100 lbs. You can keep the 2nd propane cylinder in your tow vehicle to reduce tongue weight if necessary, that’s what I do.

Re generators, a 1kw would be plenty for recharging the batteries but if you also want to run either the microwave or the a/c then you will need at least a 2kw plus an Easystart soft starter on the a/c or around a 3kw without the soft starter.

Originally posted by Dirt Sifter I prefer the cat heater. More quiet certainly, more efficient - I don't know or care in the middle of the night. More condensation - yup - but I don't care in the middle of the night; I do prep for it and accept it. Offgrid can get on your nerves if you let him, but makes some good ponder points, if they are important to you. Others make good points to consider and balance our decisions. That's why I like this forum. Think I'll leave it right here.