Robert Bruninga via EV wrote:
Note about Electric Blanket Thermostats. The Electric Blankets I have taken apart have no sensor in the blanket itself. Only the controller.
That's true of older (and cheaper?) ones. The heating element is just a long piece of resistance wire that draws about the same current regardless of temperature. I also find this type in heating pads, and even "battery heating blankets".
Using this type of blanket in a battery box can lead to overheated batteries. If a section of that wire is laid on itself, or is in a well-insulated location, its temperature can get very high! There *may* be an emergency thermal fuse or two somewhere in the blanket to prevent a fire in case it is turned on when all folded up; but that only works if that sensor itself happens to be in the "hot spot".
But many of the newer ones are using a special 2-conductor wire that has a conductive rubber insulation between them. This insulation's resistance goes UP as its temperature rises; so it is self-limiting. This wire is noticeably thicker and stiffer than the old simple resistance wire.
You can also find this type of wire in pipe heating tape, ice-melting wire for roofs and gutters, and garden warming strips.
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