How long can batteries run furnace?

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PatrioticStabilist

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I am taking off in the morning.  We have moved to Indiana and built a new motorhome garage but we have no electric in it yet and nowhere to plug up a 50 amp plug.  I had the genny running for hours today to warm up the motorhome inside and the bays but I hate running it all night.

I'm thinking of leaving the fridge run on propane tonight, of course the sniffer will draw power and other phantom items plus the furnace fan.  The batteries should be full as the genny has run for hours.  Also to leave one furnace on about 60 and close the garage door also and leave a crack but noone will be in it. I'm not filling the water tank tonight, will in the morning.

My worry is it will run the batteries down as I know they will draw a lot of power.  I have a bank of 6 in it and a separate one for the genny.  I just turned the genny off so it will take awhile for it to cool down inside the building but its to get 24 degrees tonight.

Will I run the battery bank down, this one night and in the morning I will start the genny again.
 
I believe your rig has 4-6volts batteries. If so you will fine running the furnace overnight, problem at all. Actually you would be fine with 2 good 12 volt batteries.
Get ready and head south!

ken
 
It's a crap shoot. You should probably be ok, assuming the batteries are in good condition, but it is near impossible to tell from this distance. The fridge uses very little propane, especially in cold weather. The furnace is anybody's guess.  I would check it as late at night as I could manage and maybe run the genset 30 minutes before going to bed.
 
If battery is in good condition and fully charged one night should be no problem :)
 
Re-read your post. I see you have six batteries. You should have no problem.
Do make sure your inverter is off as it can have a lot of "phantom" loads even when all the 120 volts items are off.

ken
'
 
We were dry camping last month during nights of 28 degrees, and wife likes the furnace set for 70 degrees at night, 2-6volt trojans were enough for the night, but needed a recharge the next day.
 
Our inverter was no good and I didn't want another one.  We wired in for everything off the inverter to run directly from the batteries.

I think I will do like suggested, go out about midnight and run the genny for half an hour.  The garage will keep the wind off it and now its warm inside so should take some time to cool down.

I talked to hubby and said he didn't know on that one.  2 of the batteries are about a year old, I had all the others tested at an AllState battery supplier and they said all the rest are fine but that was at least a year ago.  I don't know what they put in but these batteries are big.
 
A half hour of generator time is a waste of time, you will need longer than that to make any difference.
 
Double posting please delete one.

I checked the batteries and the 2 I can see are Fleet batteries.  Tom told me to buy all the cranking power I could get, think they are 900 amps, I know 2 of them were $300.  And like I said, they were a battery place and said all the rest were good so I figure they are.

I got BJ cleaned up and to my MIL's, she likes the dog but you can see him almost cry when I tell him to stay.  He will be fine and she is so good to him, but he is rotten.  He is fine once you get him in the bathtub no issue.  But he plants his back feet like a mule and its all I can do to get a 70 pound dog in there.  They must not be very good to him where I got him bathed.  But I'm going to have to get it done, he is more then I can lift anymore. But he is now clean and all his stuff is over there.
 
I got lucky, at 1:30AM it was 35 so I went out and turned the furnace off.

The low last night was only 33 so it turned out good, thankfully no 24, yes!  So out to crank up and warm her up and fill her up.
 
I would not have bothered to run the furnace all night just because it was going to get down to 24. Last month I was in Tucson and it got down to 18 degrees three nights in a row. I don't run the furnace at all during the night. I sleep under two comforters, a quilt and an electric blanket. My water system did not freeze.
 
Don't forget, you can get a couple of dogbone adapters to plug into a 20 amp circuit.
 
A comment on batteries. The 6 you mentioned probably include 2 engine and 4 house batteries. For the engine, you want good cranking power, as Tom mentioned. For the coach batteries you look for higher amp hours, deep cycle ones since that is what powers your furnace and other electrical requirements. If the coach batteries are in good shape and have a decent amp hour rating, 400AH or more for the 4 at 12v out, you should make it thru the nite without a problem. For 6v batteries, 4 at 200AH each gives you 400AH at 12v. 4 12v at 80AH only gives you about 320AH, 105AH rating provides 420AH.
 
"They told me to buy all the cranking power i can get"

Bad advice. it's all the AMP HOURS.

Cranking power means it is a starting battery,  Pound for Pound and cubic inch for cubic inch most all batteries have the same number of amp hours. (Optima is the exception, pound for pound they are the same but cubic inch they only weight about 60% of what non-optima batteries weigh so 60% the amp hours).

But starting batteries like to be well fed, they do not like going hungry.. If you run 'em down to 50 %, (or less) their life is seriously shortened.

It is a "knee" tihng.

As you run a battery down,,, The battery is damaged (life shortened) the more your run it down, the more the damage,  but when you hit the "Knee" in the curve, damage happens much much faster.

Deep cycle the knee is farther out and the drop past the knee is not as steep either.

So "All the cranking power you can get" is bad advice, you want all the AMP hours and DEEP CYCLE.  Note that Marine/Deep cycle are starting batteries 1st and only lip service to deep cycle.  Golf Car batteries are Deep Cycle. both the six and 12 volt kinds.
 
I'm pretty sure the 2 I bought were to start the engine.  They said the others were all good.

Tonight when I stopped I noticed they were down quite a bit.  I got to looking around and saw the receiver for the Dish was on pulling power.  Also the TV in the back has a light on.  I turned the dish receiver off and have to get my ladder in the morning and going to unplug the back TV.  The batteries are all up to 3 out of 5 already.  I'm running both furnaces and an electric heater off the genny.

I'm in the parking lot but I went outside and though the genny is kind of loud in here out there with all the traffic not that noticeable.  We have the insulating material to replace all around the cavity  but it will take Tom and I both to do it and he will have to pull out the genny. 

I did put the sound deadening stuff back around the engine cavity under the bed.  Tom said it still needs some replaced up under the frame but that stuff makes a huge difference.  What was here has pretty much degraded away and is crumbly, we cleaned a lot of it off already.  Amazing what a difference it makes.

And I will be sleeping with my electric blanket too!  And my little furry kitty, Sue Anne says that cat is not sleeping with me, no worry she won't sleep with anyone else.
 
The light on the tv is probably just indicating it is standing by, waiting to be turned on. I doubt if it adds significantly to the load on the inverter, but I guess every little bit adds up if you are trying to stretch it out the battery capacity. But if you are minimizing battery draw, why not just turn off the inverter itself? That way no 120v appliance can draw power except from shore or generator.
 
We bypassed the nonworking inverter.  All those receptacles and lights are a part of our regular circuits.

If I want electric I start the generator while moving, all the 12 volt lights work without the inverter.
 
If you're seeing lights on the 120 volt Dish receiver and on the the 120 volt TV, you have to be getting 120 volts from somewhere.

If the generator isn't running, the only other place you could be getting 120 volts from is an operating inverter.
 
As Lou says, you can't be seeing lights on those devices unless you have 120v power somewhere. Either we are misunderstanding your description of the situation or that inverter is still working to power the 120v outlets.
 

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