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Old 08-27-2014, 09:24 PM   #1024 (permalink)
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Originally Posted by MPaulHolmes View Post
I can only get 1 loop around the lem with #4 or #6 welding cable, so I guess I have to be happy with a "lem 150". Although 8 gauge would work.
For a short and SUPERVISED test, like your 10 second stall test, you may get away with a smaller wire for the short bit of wire you are stringing through your LEM.

I cannot stress enough that this is ONLY FOR A SHORT AND SUPERVISED TEST!

Here's why I think that ...

I have recently done a bit of my own testing - how much current can a #18 wire (copper stranded wire, tinned) take before it melts? Rated 16 amps for chassis wiring (low voltage) according to the table I used. I believe that is a continuous rating.

The answer was quite shocking to me:
- 80 amps (5X rated current), the insulation burned off after 10 or 20 seconds
- 225 amps (14X rated current), the tin coating on the wires melted at about 60 seconds
- I was not able to melt the copper! My setup only went up to 280 amps (17.5X) for a couple of minutes.

The piece of wire under test was about 6 inches long, strung between 2 insulators, sitting on concrete.

The test was a failure. I wanted the wire to act as a fuse, so that during my battery testing I did not have to put big, expensive fuses for each battery connection.

I ended up using cat6 cable (solid core #24, 6 inch length) as a fuse. I was not able to verify the specific current where the #24 failed ... but it was below 225A and that was OK for my battery testing. It was there in case I shorted something and thankfully I did not
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MPaulHolmes (08-27-2014), mpgmike (01-31-2022)