Can Heater run off battery in the old Popup?

Discussion in 'Heating / Cooling Systems' started by Kasey Redrum, Nov 7, 2021.

  1. Kasey Redrum

    Kasey Redrum Member

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    I have 2005 Rockwood, it has the original heater in it. I am going camping next weekend and will not have shore power. I understand that all my outlets are AC, and so they won't work if I have no shore power. However, will the Heater run? And will the battery get drained if I let the heater run a few hours each night ( 3 nights gonna be cold)??
     
  2. kitphantom

    kitphantom Well-Known Member Platinum Supporting Member

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    As a general rule, popup furnaces are 12v, so it should run off battery. However, the furnace fan is one of the energy hogs, although intermittent. Trying to keep it at tropical temps rather than cool ones will, of course, use more power. Having heat retention measures in place will help (Popup Gizmos, rugs on the floor, fleece clipped up around the bunk ends of PUGs bunk end liners). Depending on the state of the battery, what else you're running, and how cold it is (the colder it is the less base battery reserve there is). You don't want to run your battery down below about 50% state of charge, if you have a standard group 24 or 27 battery.
    Even though we have a solar panel to top off the battery each day, we tend to set the thermostat at 55* at night, always did when we had the popup. I once did 3 or 4 nights, taking the chill off morning and evening, before we had a solar panel for the popup, but the battery was brand new and in good shape - I think I ran close to the edge of stressing the battery. (Also did not yet have a meter for the battery at that point.) Once we got solar panels for the popup, and now for the travel trailer, we don't camp for more than overnight without the solar panels out, so it's been a long while since we tried to push running a furnace more than overnight without shore power or solar panels (they work well where we do the majority of our camping)
     
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  3. Grandpa Don

    Grandpa Don Well-Known Member

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    Yes, the camper heater will run off of the 12 Volt system. How long it will run without a way to keep the battery charged is a good question. You really won't know for sure until you try it. There are so many variables to consider.
     
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  4. Kasey Redrum

    Kasey Redrum Member

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    Wanted to update: So we did 3 nights in Silverwood Lake. Got into the low 50s. The heater kicked on through out the night every 20 minutes and ran for about 5 minutes, sometimes 10 minutes at a time. All night. All 3 nights. My battery started out at 12.6, by the time we left it was at 12.1. Can that be possible? We also ran water pump several times. And we also had our lights on in the evening. We also charged our phones a few times. Do I have a super battery?? I assumed it would drop down to 7 or 8? Also it seemed like a magical battery, at night it would dip down into 11.8, but then next day it would rise to 12.4 or so??? We were not connected to shore, completely off grid. Thoughts>?
     
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  5. kitphantom

    kitphantom Well-Known Member Platinum Supporting Member

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    There is less battery capacity as the ambient temperature drops, hence the lower voltage reading at night.12.1 is skating close to that 50% state of charge limit. If you haven't seen it, there's a chart (and lots of info) here: http://marxrv.com/12volt/12volt.htm
     
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  6. Anthony Hitchings

    Anthony Hitchings Well-Known Member

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    Kasey - thanks for the follow up. Your battery behavior was normal.

    Our battery gets charged by solar during the day, unless we are under tree canpy.
     
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  7. Sjm9911

    Sjm9911 Well-Known Member

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    You did good. Just remember, if its colder out or you set the temp higher it will drain quicker. Swap out the light bulbs to leds for a bit more power if that wasnt done allready.
     
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  8. Chris McAfee

    Chris McAfee New Member

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  9. davido

    davido Well-Known Member

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    At 12.6V you're fully charged. At 12.1, you're around 50% charged. You don't really want to run your battery lower than 50% charge, so you ended up in decent condition. Assuming a 75AH Group 24 battery, you used about 37.5AH of your battery's total capacity, and just about ALL of the capacity that is safe to use without causing the battery to age prematurely.

    Keep in mind a dead battery is about 10.5V to 11V. If you see your battery drop to 7 or 8v, it's not only dead, it's ready for the recycler.

    You don't have a super battery, you have a pretty typical battery, probably. Let's say the furnace consumes 3A while running, and it ran for 10 minutes every 30, or 20 minutes every hour. You ran it from 6:00pm until 8:30am, so 14.5 hours each day. Based on 20-minutes per hour of use, the furnace blower was running for 290 minutes, or 4.8 hours total. In 4.8 hours, you consumed 14.5 amp hours from your battery. Since all your loads together must have consumed around 37.5AH, the furnace was almost half your total power drain. Lights, water pump, cell chargers would account for the rest. Plus, I'll bet you ran it more than 20 minutes every 60.

    Also, in response to your observation that the battery would dip to 11.8 and then later test out at 12.4, that's a natural and totally expected behavior since the battery's current is produced by a chemical reaction. The chemical reaction takes a little time to happen, so it's possible to draw down just a little faster than the reaction can replenish. You observed a rebound effect, and it's totally normal. It's also possible that when you tested in the morning there were other loads that were consuming some power, causing some voltage drop.

    Really, you're right at that tipping point where you would probably want to add either a larger battery or a second battery. I have two Group 24 batteries, and that buys me 4-7 nights of furnace use instead of 2-4.
     
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