12v Mattress heating pad woes

[landyacht318]

Last night was kinda chilly.
An hour before climbing into bed I, plug my 'watts up' meter inline with my mattress heating pad, crank it up to 7, check out the amp draw, and see it is only half of normal.

Sure enough, I climb into bed, and only half the mattress pad is heating up.

Drat.

I have a suspicion that perhaps this failure was caused by something I recently did to the product.

What I did was remove about 5 feet of 18 awg wire from between the controller and the Ciggy plug, and the Ciggy plug itself, and replaced it with a 45 amp Anderson Powerpole connector at the end of 10 awg wire. Voltage drop went from over 2 volts, to 0.2 volts just by eliminating 2 ciggy plug receptacles and plugs. I say 2 ciggy plug receptacles as I was plugging the mattress pad's heating plug into an extension cord into which I could easily insert the 'watts up' generic meter inline and see how much Juice I used overnight.


What I also found interesting, is that the Ciggy plug, which I had earlier thought to be of a better design than most others, has no Internal fuse, like most every other ciggy plug I ever opened. I assume the fuse has been moved to inside the controller itself.


When the ciggy plug receptacles warmed up, and the voltage drop increased to over two volts, the amp draw lowered to about 4.2.

After the powerpole swap, the amp draw had increased to 6.8 amps, and the mattress heating pad heated up much faster, and all was good in my microcosm.

Until yesterday, when only half the mattress pad worked.

So was this failure induced by me minimizing the voltage drop, or just co-incidence and the failure is due to 3 winters of sleeping on the pad and breakdown of the wires inside?


I assume there are no serviceable parts inside the blanket itself and that is where the failure lies. Concur?
I'd rather not spend 90$ on a new one, but it has been a nice luxury the last few winters I'd rather not live without.

[glennts]

http://amzn.to/1uHnTzb

[landyacht318]

I've never bothered trying to fix the heating pad, nor bothered to replace it. I've not yet needed it this winter.

My GE Nighthawk H6054 sealed beams have been getting 14.5v+ for about 65 hours total now, thanks to a 12 AWG relayed harness.
These are said to be the best halogen sealed beam in this size factor, but not a terribly long lived bulb.

[MEXICOWANDERER]

I've got a single Biddeford electric blanket that draws 175 watts when it is heating. It's A.C. powered. In February I am going to break my won't-power down and purchase a Thinsulate comforter.

[mena661]

Or you can buy one 120V pad and still have it in use after 4 years like ours.

[MEXICOWANDERER]

Some of the Chinese engineering I see makes my hair stand on end and that ain't no small feat. Like that 84 watt power supply with 26 gauge power input wire. Those 50 smd LED plates have wire smaller than that (30 gauge?).With the flaky power down here, I'm using the Samlex couple to the WFCO and Lifeline to generate UPS to my most precious items including NinerBikes Galaxy II which he loaned to me permanently.

Wanna blow out a set of 9002-9008 headlight bulbs? Increase factory wire size from relay to connector socket from 18 gauge SAE to 12 gauge AWG.

Honorable Chinese Engineering. Touch it, and it'll flame the first windy day.

Just got my hands on a pair of 30 watt LED floodlight fixtures. 120 vac. Plugged them in. One was gulping 42 watts, the second 39. IR'd the chips after 10 minutes. 184F, and 177F. The heatsinks were too warm as well. My review will appear on Amazon soon. Hope the vendor has a pint of Merthiolate and a square yard of bandages. Now I have to start looking for super low dropout converters or start a series connection of silicon diodes. These fools are screaming for US government regulation and we all know what that's going to mean.

[naturist]

For what it is worth, it appears the 12 volt mattress pad warmers in sizes other than tiny are once again available: http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28164671/p/1.cfm

[landyacht318]

Well initially when first turned on the amp draw would be 6.2. After the pad had cycled on for a while and heated up the circuit, the ciggy plug voltage would drop current consumption to the low 4 range. With The powerpoles the amp draw started at 6.8 and stayed at 6.8.

Perhaps this extra 2.6 amps was the straw which broke the camels back. The side of the pad which failed is the one which sees more abuse, and honestly half the pad is still good enough, but it has not been very chilly, as far as chilly goes.

I'll probably dissect my current pad after I decide on a replacement. I might go with the same make and model and just call it 30 dollars per winter and hope it lasts 3 years.

I wonder If I can retask the controller for something else.

[MrWizard]

Power ratings on any consumer device are always the possible max, Not the actual operating use
Your previous use of three yrs was around 4,2
You increased that to 6,8. That might be 10% of max rating, but it was 50% over previous measured actual use
These are the facts
What happen is conjecture

[pnichols]

I'm a great fan of the low-power appliances in RVs being 12V powered, and I consider a ~75 watt heating pad as still being in the low-power category. My preference is especially true for those of us who drycamp - either occasionally or a lot - in our rigs or who when out and about in our rigs and at least want to be ready any time for drycamping in the most efficient way possible.

To help put things in perspective: A 75 watt heating pad that may take only 6 amps when powered directly though a 12 volt outlet could consume up to 7.5 amps when powered through an inverter, depending upon whether it's a modified sinewave or pure sinewave inverter. This 1.5 amp difference is about the consumption of a good old incandescent RV lamp - which all good drycampers try nowadays to get rid of by switching to LED lighting.

So, if you drycamp I'd recommend staying with a 12 volt heating pad ... just buy a new (top-of-the-line) one to replace your busted one. You might wind up with one that is more rugged and with improved electrical construction. If you don't drycamp and have a small inverter, just pickup a less expensive 120V AC heating pad, IMHO.

[wa8yxm]

You increased current less than 10% over specification, that should not be a problem.. I agree with PNichols.. Likely failure due to use.

I do like anderson power poles. they blow those ciggy style plugs away and then some... Just got done installing a Rig-Runnoer 4005 in my car have a 4012 here in the motor home to run assorted 12 volt stuff I've added, including my Engel Freezer. All work great on the power poles.

For those who do not know about the power poles.. They come in sizes from like 10 amp up to several hundred, though 10-40 mate well. (larger ones only mate with same size). They are asexual, that is there is no male or female, you assemble the two connectors (For 12 volt the "Standard" is tabs up red right looking into the plug) and they mate with each other. so if you have an extension cord (I do, 10GA) both ends are identical and may be swapped.

This means you do not need to ask if the pair you grab when you wire up something is INLET or OUTLET, cause they are identical.

[RoyB]

X2 what MR WIZZARD says. I use PSW Inverter here to power up my 120VAC heating pads. Have one dual pad on the bed and the wife has a smaller version she like to have on her lap sitting around the cool trailer sometimes watching HDTV... No problems after 5 years of use so far...

When I first got my OFF-ROAD Trailer I hit the local truck stops and picked up around $200 of trucker 12VDC appliances... Came away with a couple of arms full of items haha.. The only thing that survived after one year was some handy 12VDC lights. I was flabbergasted the 12VDC coffee pot taking almost 7 hours to make a pot of coffee hehe... The 12VDC portable vacuum units lasted a few times of use and didn't do well either. Everything that was over 5AMPS DC burned up all my 12VDC cigarette light plugs after an hour or so of us... Everything except the clamp on lights and the coffee pot went to King George dump. I use the coffee pot to pour oil with...

my story and I'm sticking with it...
Roy Ken

[landyacht318]

Well the specs claimed a 6.2 amp draw, but due to the increasing voltage drop as the connections heated up, the current dropped along with the voltage.

My powerpole modifications made it a steady 6.8 amps which is not 50% over the baseline 6.2a, but perhaps the engineers expected the voltage drop and the resulting drop in amperage too.

But since they recommend these for truckers and they say to turn on the mattress heating pad a few hours before turning off the engine, they would have to figure in battery charging voltages making it to the ciggy receptacle. Even with 2 volts drop across the ciggy plug from 14.4 that leaves 12.4v which is all my ciggy plug was ever really fed. Could there really be so little overhead engineered into such a device?

I am not accounting for the 5 feet of 18 awg cable I cut off between controller and ciggy plug. Certainly the voltage across that 5 feet between plug and controller, which I did not measure, was also significant.

I hate to be one of those people fishing for what I want to hear and dismissing any opinions that do not do so. What I want to hear is that the failure was likely caused by 3 winters of use and abuse my my 220 lb frame wearing out the wiring. I don't want to hear that I have to artificially limit the current by planned voltage drop into a replacement pad or risk premature failure.

I wonder if I can determine if the failure was wear and tear related, or if it was induced by me reducing the voltage drop through a shorter circuit path and elimination of one of the poorest ubiquitous connectors ever designed.

That extra 5 feet of 18 awg wire was always in the way. I was glad to be rid of it. I'd hate to think its elimination was the cause of the failure.

I wonder what the life expectancy is for such a device.
I'd consider 120v models now that I have a Quiet PSW inverter, but I really liked this 12v unit, while it lasted.

[pnichols]

landyacht318 wrote:
.... and the failure is due to 3 winters of sleeping on the pad and breakdown of the wires inside?

Unless the design of the pad depended upon XXX amount of voltage drop in the wiring - which you changed - then I suspect breakdown of the wiring from use was the cause .... probably the wires in the pad itself.

This can happen in 120V AC heating pads and electric blankets too. It has happened to me many times down through the years as I keep wearing out and periodically replacing electric blankets and heating pads in our home.

[MrWizard]

its possible even probable, you increased current 50%,

the problems you mention
are one of the reasons, i shy away from 12v pads and prefer 120v pads and blankets, yes i loose a little efficiency using the inverter, but i gain reliably
and i don't have to worry about 12v wiring and power plugs and voltage drop
any drop is at the batteries & inverter not the 120v output to the pad/blanket