Mod #50: Electric Mattress Warming Pad

Mod #50: Electric Mattress Warming Pad

Submitted on: 07/27/08

     Category: heating, interior
Mod Rating: 12345

(32 ratings)

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Mod Description:

Turn down the heater. You’re roasting me out of here! Turn up the heater. It’s so cold in here I can see my breath! Give me more blankets. Fine! Take all you want. He’s hot and she’s cold. Sound familiar? One thing that can be agreed on though is that an RV heater can dry your nose and throat out faster than a desert sandstorm. How can you sleep in your own relative comfort and at the same time save the peace? Do the electric mattress warming pad mod!

Mod Difficulty:

An electric mattress warming pad is different than an electric blanket. You sleep on top of the mattress pad rather than the blanket being on top of you. This has the effect of heating the mattress rather than having most of the heat generated by an electric blanket go to waste as it radiates in to the air. And you can start warming up the mattress before you get in to bed so you’re not trying to warm up the mattress with your body.

Mattress pad warmers come in two types: 115-volt AC and 12-volt DC. The AC models are fitted sheets that stretch over the mattress while the DC type is pinned to the top of the mattress. For RVs, either type can be used but if you dry camp and don’t have AC power, the 12-volt model will serve you well. It can be plugged in to the typical RV 12-volt receptacle. The 12-volt warmer does draw a bit of current, around 200 watts at the max setting. But chances are you won’t be at that setting for long. Average consumption is about 100 watts so ensure your battery is topped up before hitting the sack.

And there are even warmers that have two separate controllers so you can dial in your own comfort level. A his-and-hers arrangement that sure to keep both camping happy!

TipIf you are powering an AC mattress warmer from an inverter, be sure it is not a modified sine wave (or MSW) type inverter. The digital controllers found on most AC mattress warmers don’t like the MSW power and will refuse to work. A true sine wave inverter must be used instead.

ModMyRV recommends these parts for this mod:
Patented Products T-36 12-Volt 60 x 36 Twin Size Bunk Warmer Pad
Roadpro 58″ x 42.5″ 12-Volt Heated Premium Fleece Travel Blanket with Built-In Thermostat - Blue
Wagan 12V Heated Seat Cushion

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15 Comments For This Mod

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  1. jmt

    Great idea..never thought to toss my electric blanket and just get a mattress heater. Dah…In the tip above I’m a little confused at how I would know what type of inverter I have? I have a 2009 TT.

  2. ModMyRV

    Usually less expensive inverters are the MSW type. For example, if you have a 400 watt inverter you paid $50 for, then it is very likely a MSW type. There are 2 other ways to tell: hook up the inverter to an oscilloscope and look at the AC output wave form, or just look at the user manual that came with the inverter. Pure sine wave inverters are costly because they provide very clean AC power. But bargains can be found.

    What brand/model is your TT? And what brand and power rating is the inverter?

  3. jmt

    I have a 2009 KZ Spree. I’ll have to take a look at what brand and power rating I have.

  4. jmt

    Inverter is a World Friendship Company 70VF. Output 55 Amps (charging and load) Input 950 watts. Now what in the world does all that mean?

  5. ModMyRV

    Those sound like your CONVERTER specs rather than those of an inverter. A converter converts AC voltage to DC voltage. An inverter does just the opposite: converts DC voltage to AC voltage. Every RV has a converter. Very few, except for the more expensive ones, have an inverter.

    BTW, the converter you have is a good one as it has a smart 3-stage charger that is much more friendly to your batteries than the cheaper single stage chargers.

  6. jmt

    Great I’m learning here. (Keep in mind I picked up my first TT Jan 16th of this year) Ok so glad to hear that I have a converter and not an inverter. When would I want to convert AC to DC? I’d need to have stuff the runs on DC right?

  7. ModMyRV

    Your converter will automatically do this for you. All of your TTs lights, water pump, fans, etc., all run on 12 volts. Your converter provides this DC power when plugged in to shore power. When you are not plugged in, your battery provides the DC power.

    An inverter is used when you have no shore power. It uses your battery to invert DC power to AC power, so you can run appliances or a TV. Check out Mod #10. There is a good explanation on inverters in that mod.

    And congrats on the new TT. You’ll find the more mods you do, the more you want to do more mods. Hey that sounds like a slogan…

  8. jmt

    Great thanks for the wisdom.

  9. Rolling Condo

    I bought 2 of the last 3 30″X60″ Electro Warmth 12V heated mattress pads from that they had, as I have twin beds. Electo Warmth now only makes the 36″X60″ in 12V. I had previously wired in extra 12V outlets when I upgraded my converter to a PD-9145 model.
    I tried it out last weekend in the backyard. I can definitely say that having the heat below is alot better than above (ie. electric blanket). Slept very warm and cozy, outside temps at 34F and using just a ceramic heater held the temp at 64F inside.

  10. Lencactustwo

    Bought the 120v model at Wally although I am usually plugged into the ground and own a genset too. I am sure that all models of this mod work great as I find that I need it on for only the first few SHOCKing moments I get into bed. We as people generate heat as we sleep and with an additional blanket during the cold season, a perfect mod for all that can plug one in

  11. kmac

    Have used the electric warming mattress pad for years - so comfortable to warm up bed about 30 minutes beforehand on those cold nights, and turn down the heater to (your) minimum overnight setting. Much warmer than electric warming blanket. More comfortable and lighter on propane use.

  12. nbounder

    I think the newbies are being confused. If you have shore power, by all means plug your mattress heater into the 120V outlet. If you have a 12V heater, you need to be careful - those cigarette lighter sockets are rarely rated for 8 Amp draw that a 100 watt heater requires. If the 12V socket you plug into is the common, cheapie cheerful type, it just might heat up enough to cause bad problems. If you are boon docking and choose to use inverter power, then the inverter needs to be a Full Sine Wave model. A Modified Sine Wave unit will likely get the heater’s controller mad, and it will get even. It just might fry itself to death. That’ll fix ya. If you do not know which type inverter you have, you very likely have a MSW unit, as they are noticeably less expensive and much more common.

  13. Barbara Mann

    I’m blessing nbounder right now - I was about to return the mattress pad I’d bought because I was indeed confused! Thanks - it didn’t make sense that it would be a problem on shore power, but I’m still learning and cautious! :)

  14. djfrown

    Has anyone used a 12v to 19v DC/DC converter with a SoftHeat mattress pad? My queen pad works fine through my inverter or when hooked up. The pad takes 120v AC and provides 16.5v +/- 10% @ 3.5A DC power through a “brick”. This wastes a lot of power (heat and inverter overhead). I’m considering bypassing the brick by using a 10A DC/DC converter. Any comments?

  15. krbjmpr

    Most mattress pads and electric blankets regulate heat via cycling on and off, either using a switch (on/off) or using a pulse width modulation duty cycle waveform. The latter switches on/off very quickly, more even heating. I do not know what the SoftHeat pad uses, so lets look at worst case.

    16.5vdc @ 3.5A = 57.75 Watts
    A 3.5A current flow at 16.5vdc = 4.7 ohms of resistance.
    At 12volts, this resistance will limit current flow to: 2.55 amps
    At 13.8volts, current is limited to (13.8/4.7): 2.93 amps
    At 12.8volts, battery fully charged (no converter): 2.72 Amps

    If you were to apply battery voltage directly to the mattress pad, then you will have (using middle of range battery) V*A: 34.8 watts, or about 75% of original heat being generated. The bed will take a bit longer to warm up, approx 25% or so, but it will get warm. Applying power to the mattress pad all the time may cause it to overheat, depending on amount of blankets that you have on top.

    There are a slew of PWM light dimmers on amazon for controlling 12vdc lighting. As long as you stay above 5Amps (safety factor), then you can use the controller to keep a constant power level to the pad. And of course, use a fuse (here I Would do a 3 or 5A).

    You are also able to use a mechanical switch type of thermostat, have the probe extend down the middle of the bed. You will likely have same issues that I did, the relay switching in and out will drive you nuts.

    If you are uncomfortable with modifying, take a look at the heated blankets and such found at Loves, Pilot, Flying J, etc. All 12volt. No Tstat.

    Oh and just 1 more calculation, 2.7A current * 8 hours (assumed) sleep = 21.6 Amp Hours used off of batteries, requiring (for lead acid) approx 26AH to replace energy used.

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