Have some Watt Values for Heated Mattresses

Discussion in 'General Camping Discussion Forum' started by Whatevs, Sep 1, 2017.

  1. Whatevs

    Whatevs Member

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    Some older threads I've seen have given watt numbers for heated mattress pads and blankets, but not much about actual heated mattresses other than to say don't try to use them when boondocking.

    Anyways, I grabbed my Kill-a-watt meter and headed to the popup to test the actual watt values for my heated mattresses on each setting. Then I went onto stack exchange to find a formula for battery drain time.

    <Update 9/11/2017> - The inverter I used to make my estimates was not fit for purpose and was also broken. So I got my hands on a better one and just observed what happened over an 8 hour period at the highest level (6) and the middle level (3). The short answer for level 6 is that I got 5 hours of use, but my battery was drained too far (down to 25%). For level 3 it was slightly more practical. 8 Hours of usage at level 3 reduced the battery to around 70%. Detailed results below.

    *** Conclusion: When connected to a 100ah battery, the mattress heaters aren't impractical if used at mid or low levels. If we were dry camping with the kids and there was an unexpected cold snap (this has happened to us), we would entertain the idea of using the mattress heater for their bed at level 3 for at least a few hours.

    Test 1
    -----
    Level 6 Test (88 Watts drain) = Battery Drained to around 25% in 5 hours. That's less than one night and a battery drained low enough to risk longevity (oops).
    1.5 Hours - 82 watts/12.2 volts
    3.5 hours - 78 watts/12.0 volts
    5 Hours - 77 watts/11.9 volts (jumped a bit after leaving the battery without draw for a few minutes)

    Test 2
    -----
    Level 3 Test (18 Watts drain) = Battery Drained to around 70% in 8 hours. That means 30% a night. 2 Nights would bring the battery down to 40% or so.
    1.5 Hours - 24 watts/12.6 volts
    3.5 hours - 25 watts/12.5 volts
    5 Hours - 27 watts/12.3 volts
    6 Hours - 27 Watts/12.3 volts
    7 Hours - 29 Watts/12.3 volts
    8 Hours - 29 Watts/12.3 volts (jumped to 12.5 after leaving the battery without draw for a minutes)
     
    Last edited: Sep 11, 2017
  2. Douggro

    Douggro Active Member

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    Battery voltage won't be constant and will drop with usage. Amp/Watt drain will increase as voltage drops - I believe it's a logarithmic scale. The StackExchange calculation is OK as a general guide, but don't expect it to be "real-world" equivalent. And I wouldn't recommend running a battery down below 50% of charge capacity regularly as it's hard on the plates and cells.
     
  3. davekkk

    davekkk Active Member

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    Are these 12v mattress heaters?
     
  4. Whatevs

    Whatevs Member

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    Good to know. Does your advice regarding the 50% discharge also apply to AGM batteries?
     
  5. Whatevs

    Whatevs Member

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    They plug into the outlets in the camper with the same 2 prog plugs I use at home. So I don't think so. They're made by Thermosoft.
     
    Last edited: Sep 1, 2017
  6. Douggro

    Douggro Active Member

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    AGM's might tolerate the discharge better. The main problem is heat: discharge loading at lower voltages heats up the battery, which is never good for them.
     
  7. tombiasi

    tombiasi Well-Known Member

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    How are you going to run a 120 VAC device from your battery?
     
  8. Whatevs

    Whatevs Member

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    Not sure. I'm open to suggestions/input.
     
  9. jmkay1

    jmkay1 2004 Fleetwood/Coleman Utah

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    . Not sure if you are aware, but the outlets in the camper do not work when on battery.
     
  10. Whatevs

    Whatevs Member

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    Yup, I'm aware. We boondock most of the time, and I want to see how much time I could get out of the heaters if I managed to get them connected to my batteries. I'm open to suggestions and advice on how that could work... or not ;)
     
  11. Whatevs

    Whatevs Member

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    I've got 2 x 100AH batteries for the camper and a fairly heavy duty inverter sitting in the basement which will probably work here. I think it's probably time just to connect it and test it out. I ran the numbers and used Douggro's suggestion of limiting the discharge to 50% and came up with some times based on each setting. I'll update the original post with my updated guestimates, run the test with the inverter and one battery, and see what happens. When all is said and done I'll update again with the results.

    Btw, I looked again and found this post from 2009. http://www.popupportal.com/threads/amps-used-by-heated-mattress.31020/

    Seems like the OP of that thread resigned himself to just spending 20$ on socks and a sweater ;)
     
  12. f5moab

    f5moab Retired from the Federal Government

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    Connect the trailer battery to an inverter and that change the voltage to 120 AC. Most decent size inverters should handle 55 watts with no problem.
    I have a couple 400 watt and one 800 watt. These are not sine wave inverters so some items don't like them. However, the mattress should be ok (I guess), and they can charge laptop, phone, batteries with no problem. But might not run a computer or some TVs directly cause of the wave. And they do use some of the supplied power for their own electronics, so the batteries will drop from the inverter use as well as the plugged in device. From what I have been told it is between 10-15 percent. (So instead of 55 watts, you might be drawing 60 watts or more.)

    And DOUGGRO noted Peukert's Law....As the rate of discharge increases, the battery's available capacity decreases.
     
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  13. Whatevs

    Whatevs Member

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    Thanks for this. We use small inverters right now for phones etc. when we camp. Wasn't aware of the 10-15% wattage tax, good to know. I've got a fairly heavy duty inverter lying around unused, so I'll use it but I think it's between 1000w and 3000w which may be overkill. Anyways, will unearth it and try it out. Thanks for all of the advice so far!
     
  14. roybraddy

    roybraddy Well-Known Member

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    I have a 600WATT AIMS PSW Power Inverter always ON in my POPUP trailer with one multi-head extension Cord going to the HDTV area and the second multi-head extension cord going back to the cabinet top close to our tent bed we sleep in. This is where we plug in all of our 120VAC items we want to run off the batteries. This has a minimal battery drain unless you have things plugged into it...
    [​IMG]

    Wife sits in the trailer watching HDTV with one of those 12V heated Lap Blankets. We have moved that to the bed as a bed cover many times with no problem... Think the 12V lap blanket is around 50Watts... Its definitely less drain on my batteries the Propane Heater blower fan uses...

    When we are camping off the batteries I watch the battery DC VOLTAGE like a hawk (actually it alarms) and if it gets down to 12.0VDC (Appx 50% charge state) before morning I shut it all down... All was planned to use all the things we wanted to use when camping off-grid and then run my 2KW Generator the next morning at 8AM when allowed to charge my battery bank back up to its 90% charge state. Takes around three hours of generator run time...

    Roy Ken
    [​IMG]
     
  15. davekkk

    davekkk Active Member

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    I didn't have much luck running a heating blanket off my low end inverter. The blanket controller just blinks and wont heat. Do a google search for heating blanket inverter, I think this was the article I ran into.
    http://www.irv2.com/forums/f59/warning-heating-blanket-with-inverter-44800.html

    I personally would love to find one that was 12v that had good reviews and wasn't too expensive.
     
  16. tombiasi

    tombiasi Well-Known Member

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    Generally it is not a good idea to use battery for heating devices. Figure the current the device takes at 120 V. will be 10 times at 12 V. So to get the same heat that you get at 55 watts at 120 V would take over 5 amps of inverter current. For most batteries that would be 1 or 2 nights depending on cycle rate if that's all you ran. But you can't just supply 12 volts to a 120 volt device. You need the inverter. My sleeping bag can handle what I need.
     
  17. tfischer

    tfischer Well-Known Member

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    Inverters are something like 60-80% efficient. So bump up that wattage by 20-40% when doing battery drain calcs.

    Not a good idea to run resistance heat from a battery, it will drain very fast. You're looking at a rate of something like 6A/hour on high.
     
  18. roybraddy

    roybraddy Well-Known Member

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    My "DUTY" 600WATT PURE SINE WAVE Power Inverter is the AIMS PWRI60012S from AMAZON for $130, I got mine a few years back and it was $159 dollars back then...

    [​IMG]
    Google image

    I don't even look at MSW type Power Inverters anymore... This way i don't ever have to worry about the so called BLUE SMOKE when running motor and Electronic things...

    This runs my Computer/Tablets chargers, small fans, HDTV, Clocks, DVRs, Electric Blanket Controller, Mr Coffee bean coffee grinder, etc...

    I very seldom run more than 300WATTs usually from 4PM to 10PM in the evening which will draw around 25 AMPS from my battery bank... Nice to have an additional 300WATTs if needed...

    This Power Inverter is installed within five feet of my main battery switch and then I run one multi-head extension cords from the Power Inverter to the Home Entertainment area and a second multihead extension cord to a cabinet top close to the tent trailer bed we sleep in... It is always on and I can turn off the multihead extension cord locally when not being used. The parasitic drain of the 600WATT Power Inverter is nil being left on with no drain...

    [​IMG]
    Google image

    Been doing this since early 2009 with no issues...

    Roy Ken
    [​IMG]
     
  19. Whatevs

    Whatevs Member

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    I've got an update here. I plugged the mattress heater into an inverter I had lying around, and re-checked the numbers at different settings. I've added them below. The inverter isn't sinewave, and runs at 1000w per plug with three plugs. So I'm swatting a fly with a sledge hammer, but here's what I got:
    <updated 9/11/2017>
    I found out later that the data I recorded here was done using a broken inverter. Removed these results and ran a real-world test using a 150w inverter and my original battery. Updated the original post with the real-world test data.
     
    Last edited: Sep 11, 2017
  20. Douggro

    Douggro Active Member

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    The real-world test is to check the amperage draw from the battery with an ammeter. Checking wattage past the inverter only gives you info on the device consumption; inverters are not 100%-efficient and you get amperage loss through them to run the inverter itself. As the battery is discharged and the voltage drops, you should see an increase in the amperage draw. Ohm's Law.
     

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