Doing power resistor with simple stuff


While playing with the 2nd battery tester idea, i ran into the need for custom ballast resistors.
They are resistors with a low value that will take the heat, so that the FET will not have all the power to dissipate.

I have a few of them bought on ebay, but of course i needed a custom value, much lower than usual.

Why not do them ourself ?

What  we need  :

  • Kanthal wires, good i'm a vaper. They heat a lot when current is passed through them, and they can stand the heat. We'll twist two 0.3 mm brand together
  • Plaster (paris plaster actually)
The wire is wrapped to be a coil
 (this example is without a twisted wire, much better to twist it)
You will have problem soldering the kanthal, wrap  it around the red/black wire and put a generous amount of solder around it.



Let's 3D print a custom mold, you can use whatever you have available (cardboard...)


Put the coild inside it, pour plaster in the mold, wait a couple of hours and :



So we have now our 1.5 Ohm ballats resistor.
It heats up a lot, but it can take it, we aim at < 2 w dissipated there, absolutely no problem.


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