Dry camping with furnace on

pnichols wrote:
I'm a bit confused by the short battery life with furnace use comments here.

In high 30's temps at night our furnace cycles nicely when set at 60 degrees - about 5 minutes ON every 15 minutes or so. It's blower draws round 7 amps when it's running ... so cycling such that it's ON 5 minutes around 4 times every 60 minutes means it runs about 4 times X 5 minutes = 20 minutes every 60 minutes. This means that it consumes about 1/3 of 7 amp-hours = 2.33 amp-hours every hour on a high 30's temperatures night.

For a 10 hour night run this means that it consumes only about 23 amp-hours of our 230 amp-hour 12V AGM deep cycle battery bank's capacity.

We also run a couple of CPAP machines at night (room temp air only - no heat). Our batteries easily go 2-3 days this way before needing charging after dropping them down to around a 40 per cent state of charge (60 per cent of capacity used). We have a small 24 foot Class C that we block off the cab area on and our furnace is a 26,000 BTU one. We keep all shades drawn to better trap a layer of insulating air between the shades and the window glass. We also wedge a sheet of insulating material between the the shade and the window glass on one window by the bed. We do not have any solar on board.

I wonder why some of you are experiencing such short battery life with furnace use? Our propane furnace has worked well so far without seeming to be a battery hog at all - but we have not yet tried to drycamp in 20 degree weather!

Our experience is similar in our current 30' Class-A as well as in our prior 31' Class-C. We have a 30,000 btu furnace and two Interstate GC2-XHD 6v batteries in series with 232 amp hours of capacity.

After a night of heavy furnace use at remote dark sky sites in the mountains or desert, with nighttime temperatures regularly dipping into the low 30's, 20's (F)or even high teens depending on season, I can easily run the furnace on 68* without making a dent in battery power. This is also done with frequent trips in and out of the door since our astronomy club tends to use our RV as the "warming hut" and snack and coffee stop at astronomy events.

We also run a BiPAP for my wife. Her old ResMed ran off 12v and I used to run it all night on a 28 ah Duracell 600 pack. Unfortunately, her new ResMed BiPAP (with a humidifier) runs off 24v and it quickly drains the previous pack. Since I already use a similar setup to run our telescope mounts and imaging gear, we run her new BiPAP off of a 60ah AGM battery in a trolling motor case with the ResMed adapter that kicks it up to 24V.

Everything we have, from coach batteries, to telescope batteries, to BiPAP batteries are recharged via solar during the day. I just hate to run a generator when we're boondocking.