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QUESTION: I have a Sunbeam heating pad. It usually plugs into an AC outlet. I'm trying to find out if there's a way to have it function off of DC using some kind of adapter or set up?

Thanks,
Dan

ANSWER: Dan -
How about using a DC-to-AC inverter.
http://www.amazon.com/BESTEK%C2%AE-Outlets-Inverter-Charging-Smartphones/dp/B004
Good luck -
Bill

---------- FOLLOW-UP ----------

QUESTION: Hi Bill,

An inverter creates AC from a DC source (and I understand why you gave me that answer).  But that is not actually what I'm trying to do.  I'm trying to understand whether this heating pad, even though it normally runs on AC, whether it could run off of DC current, and what electrical components would be necessary, so that it could.
Thanks!
Dan

Answer
I'm not an electrical engineer, Dan, so be cautious with this.
The heating pad is just a length of wire. AC or DC current can flow through the fixed resistance of the wire, heating it. The control on your 120 volt AC pad adjusts the voltage applied to the wire (between 120 volts and some lower voltage), which changes the current flowing through the wire, thus changing the amount of heat produced.

If you eliminate the control and  apply 12 volt DC to the same wire, you will get at most one-tenth of the current flow, and thus no more than one-tenth of the heat you could have had at 120 volt AC.

If you really want a "useful" DC powered heating pad, it  might be necessary to buy one, but then you'd need probably to find a 120 volt DC source to plug in to. That last part might be the hardest part.
Good luck!
Bill
Questioner's Rating
 Rating(1-10) Knowledgeability = 6 Clarity of Response = 10 Politeness = 10 Comment Thanks Bill!

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#### W.A. (Bill) Stevens

##### Expertise

I can explain the technical and economic tradeoffs of making electricity from natural gas, coal, nuclear, wind, solar, and biomass energy sources. I'm familiar with air pollution control technologies, including CO2 capture and sequestration. I have a good understanding of the science on global warming and can explain how energy use inefficiencies and various fuels and technologies contribute to that process. I can tell you why we have to build more new gas, nuclear, wind, and solar power plants, but will still have to keep using coal for a few decades to make elctricity. I can explain energy conversion efficiency and power plant operations. However ... I'm not an electrician, so probably cannot help with questions on motors or wiring. ;-)

##### Experience

Forty years as a registered professional mechanical engineer.

Education/Credentials
Graduate of Purdue University, School of Mechanical Engineering.

Past/Present Clients
EPA, DOE, State Department, USAID, World Bank, Bechtel Power Corporation, U.S. Generating Company, numerous electric utility and independent power companies.

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