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heated jacket

R791945

Jun 19, 2015
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I have noticed some electric heating pads for outdoor clothing. I would like to run it off a 12v battery sometimes and a 7.4 li-ion battery pack other times. I propose to cut off the usb connector and put a 3.5mm audio plug in its place. This is a description for one such package:

Type:1 for 5 heating cloth
Voltage:5V-12V
Power:9 watt
Three gear temperature:30—50 degree
https://www.ebay.co.uk/itm/5-Pad-US...m=232962928211&_trksid=p2047675.c100005.m1851

I am a bit surprised at the acceptable voltage range. Should it work equally well at any voltage between 5-12v?
 

dave9

Mar 5, 2017
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lol... " Pull resistance. Cannon be broken. "

Sometimes I am amazed at the amount of components in the build for something cheap-from-China, so I could be wrong, but at this price point I am doubting that it has much in the way of regulated current in that little power button box, and yet it claims 3 heat settings for 30C/40C/50C.

Anyone know the cheapest way to do that with a push-button switch? If it were only two settings then I would have assumed one puts power straight through to the heating elements (switch closed) and the other puts power through a series resistor. I suppose it could be a multi-way switch, but I don't recall seeing anything like that with a push-button activation.

Anyway my point is that I doubt it works "equally well" at the different voltage inputs in a range from 5V to 12V. For example it claims 9W so from purely resistive element(s) design, and assuming the rated 9W is at this upper voltage, you'd have a 16ohm resistance and 0.75A through the elements.

Using the same 16 ohm heating elements, at 5V it would be a little over 0.3A current and a mere 1.6W. Big difference!

On the other hand, maybe they're practically giving it away and it has a current regulated switching supply in that button box and really does operate the same wattage over this 5V-12V range.

I would try to find some youtube video where someone did a teardown to see what's in that button box. However, even at 9W, that is not much heat spread out over 5 elements, yet it's built to run from USB so you can't expect a lot.

Even then, I don't know the power rating of a typical 3.5mm audio plug and would think twice about using one, instead opting for something built and rated for power.
 
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dave9

Mar 5, 2017
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^ Might not be too bad if it was cold outside and in a garment worn over other clothing.

Besides the number is a bit meaningless without knowing the ambient temperature when the temp was taken so it could be seen as a rise over ambient temp, #.

Back in the day people used to use lighter fluid powered hand warmers in a felt pouch and they got at least that hot.

71IhFNafk0L._SX569_.jpg
 
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