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Old 11-19-2018, 09:20 PM   #1
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Join Date: Nov 2018
Posts: 19
Propane furnace battery draw

Hey all,

After many years of dreaming I sold my Syncro and saved up and just finally took possession of my new MB sprinter 4x4 from Brian and company. I am beyond happy. The Syncro was awesome but felt beat up after driving for more than 4 hours, now I can go x country no problem.

I do have a questions that I have been unable to find answers for, I did search the forum but no luck. Sorry if this has been answered and I missed it.

Was hoping I could get some advice.

Q: How long can I run my Suburban NT-16sq? propane furnace for when running on the house battery? So I live in Portland Oregon where the sun dont shine in the winter . I plan on doing some winter excursions, I have solar but no sun most of the winter. I will not be able to hook up to shore power. If I run my propane heater all day and all night about how long will it run safely before damaging the house battery? According to the propane heater manual the draw is 2.8A

I am using this calculator

Battery Life Calculator

200ah battery I have UB4D

So according to the calculator running a 2.8a draw on a 200ah battery it would yield a 71.4 hours. Providing nothing else is running. In other words can I expect to run the propane heater safely for about 2 days conservatively considering it will be going on and off considering I will set the thermostat to low. Does that sound right?

I suppose I could run the engine to charge up a bit or go for a drive.



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Old 11-19-2018, 10:12 PM   #2
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Location: Oregon Ciry Oregon
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A 200 amp hour battery bank only has 100 ah that is usable without damaging the batteries. If the van is well insulated and it is really cold the furnace will probably run 70 to 80% of the time. Less if you can close off the drivers/passenger area. We use a blanket as a divider.

If you are driving every day you should not have a problem draining the batteries. If not the solar will give you some power even on cloudy days.

Are you going to be on the east or west side of the Cascades?

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Old 11-20-2018, 10:02 AM   #3
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Join Date: Nov 2018
Posts: 19
Hey Larrie,

Thanks for the info, this helps. This immediate trip I dont think will be a problem since we are just going out to the coast for a fist full of days and as you know the coast is fairly mild. Also I can alway monitor the panel and see when its time to start the van or go for a charging drive. Also its good to know the panels work in low light, I was unaware of this as I have solar on my house and they do nothing when its cloudy.

My first camp in the van was down near Klamath Falls and it got down to 19 F, the heater was running pretty constant but surprisingly even up top it was not all that bad.

Thanks again,

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Old 11-20-2018, 12:00 PM   #4
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Location: TN
Posts: 9,225
Solar panel technology has come a long way. Modern panels will soak up power with practically no light.

As for your furnace I would just monitor the panel. If you get down to 12.2 or less with the furnace and/or other things running then just idle for an hour and you'll put a good bit of juice back in your batteries. The 4d is quite a battery and i'd think you could go a couple days easily before this is necessary.


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Old 11-29-2018, 11:19 AM   #5
Join Date: Jun 2015
Location: SF Bay Area
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Not only do you not want to go less than 50% (as noted above), your battery capacity drops significantly once it gets below freezing.

If you do get a solar panel, you won't have to worry at all if that's the only item drawing off the battery. I had a single panel on my Four Wheel Camper and the propane furnace drew about the same as yours and I never had any battery issues. With a quality panel and charger, not only will you charge when it's overcast, you can even get a charge with some snow covering the panel. Just brush it off in the morning and evening and you should be fine.
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