Anyone built a battery cell high watt test rig

If you want a good dummy load, go to the dump and pull the element out of an electric clothes dryer.

It will be a metal pan 2' in diameter with ceramic lifting plates that hold a thick coil of nichrome (like a Slinky) in a circle around the pan with two spade terminals on each end of the wire.

A clothes dryer is 240v and maxes at 7200 watts, almost all of which is the element.

That makes the element around 8 ohms (though it probably is lower when cold and higher when hot).

It's designed to have a fan blowing air over it non-stop to cool it obviously, but then it's also designed to sit in a metal box. Not sure just how hot it would get if you gave it 240v.

You could run a gater clip anywhere down the coil like a variac to tap progressively smaller sections of the total resistance, though note that you'd be heating the wire section increasingly hotter. I'd consider hooking the coil up in parallel pairs or tripples (cut and restitch the coil) if you want more heat or lower voltage.

Alternatively, an oven heating coil (3000 watts, 240v) can be pretty much flatlined without damaging it, ditto for stovetop elements (1000-3000 watts), both of which you can get for cheap/free at the dump if you're kind and polite and mention it's for a science project for school. These make great loads and you can safely sink them into a metal can of water (except for where the ends are exposed through the white insulator). They're insulated and designed to be rapidly chilled because that's what putting a cold pot of water on them does anyway.

Water has massive heat capacity, so, a simple tank will take forever to actually boil itself dry and the element can handle full power in open air without fan cooling regardless.

bodo-ev said:

Heating elements (pulled from an oven, washing machine, dryer...) are doubtless a good option to test a whole pack (100+ volts), but you would need a lot of them if you want to test a single cell.

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Oven and stovetop elements are insulated (the nichrome is inside, then a white insulator, then a soft iron exterior). Those are tricky to partially use.

Clothes dryer elements are just a bare slinky of nichrome. You can use gator clips to select any resistance along its length.

Another thought: What about large electrodes (e.g. 1 sqm steel plates) instead of heating elements dipped into a (salt-)water tank? At power stations they usually feed them with AC, but for short time currents also DC should work. However one should take care of the hydrogen...

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You don't want to use steel and you don't want to use table salt. Table salt will instantly create chlorine gas and rust even stainless steel in moments, turning the water into a thick diarrhea blend of green and brown.

Use stainless plates, and battery acid. TSP in a pinch. Baking soda will work but isn't great.

You'll be splitting H2O into H2 and O2 in a perfectly explosive mixture, but both gasses diffuse almost instantly ("water torches" are safe for use in malls and other enclosed spaces). A fan and an open room would be fine. It just bubbles up to the surface.

There's much better ways to create ghetto resistors.