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post #7 of (permalink) Old 06-24-2007, 03:03 PM
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Originally Posted by Junk Yard Genius View Post
On your alternator problem,
Use at least a 10 gauge wire, ...
Originally Posted by Junk Yard Genius View Post
For battery cables, use at least a 4 gauge fine strand wire, or 2 gauge 'battery cable'...
Not near big enough on either.

Originally Posted by Junk Yard Genius View Post
Welding cable is fine strand, carries more current ...
Welding cable is usually virgin copper, no alloys, so it will carry more current for the size of wire ...
I’m gonna need a reference on this one. I’ve been doing electrical for a lot of years and I’ve never heard of this. I think its more likely some bad conclusion jumping.

Comparing the ampacity for copper wire to the ampacity chart for welder cable, it would seem that welder cable is indeed higher than copper wire. The problem lies in using the wrong table for the copper wire, another table for wire in free air and comparing at the 90 temperature as in the chart for the welder cable, the ampacity increases. The welder cable chart has length limits, the copper wire chart does not.

To the side in the welder cable chart, there is another table given for 600V applications, the same voltage as the copper wire rating. Note that the ratings for welder cable are now lower than for wire in free air, but also note that the ratings for the welder cable are given at 40 ambient temperature. The NEC Table 310.17 wire ratings were as stated, “Based on Ambient Air Temperature of 30C." Below the table is a correction factor table for the higher temperature.

Now, we could make it difficult try to determine the temperature where the wire is or just use the enclosed conductor chart. 6 AWG will get you up to 140 amps or better for your alternator. If it’s only 85 amps, you COULD get by with 8 AWG. If you drop down to 10 AWG figuring that the alternator bracket, through the engine to ground will carry most of the load, you might want to read the Fire Extinguisher Mounting Options thread. For battery cable, I like at least 1/0 (one aught), 2/0 if I can get it.

The wire or welding cable is up to you. My jumper cables are welder lead mostly because they were free (cut out of an old cable with insulation cuts) but they also easy to handle and roll into a nice small loop for storage. Welder cable is easier to form but also doesn’t hold its shape so it has to be supported every few inches.

There are 10 kinds of people in the world.
Those who understand binary and those who don't.
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