Date:         Fri, 13 Nov 2009 21:06:55 -0800
Reply-To:     Steve Williams <sbw@SBW.ORG>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Steve Williams <sbw@SBW.ORG>
Subject:      Re: A Current Question
In-Reply-To:  <d81c42190911131810p11f32e7cw89a39b25e413732c@mail.gmail.co m>
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At 06:10 PM 11/13/2009, John Meeks wrote:
>... the wire is good for 37 amps. Will the connectors and the wire
>do the trick or will I have a meltdown or worse?

Don't know about the connectors, but the wire shouldn't be a problem.

Keep in mind that the current rating for wires is based on heat
dissipation.  If you draw 100 amps through 6 gauge wire for 5
seconds, the wire will barely warm up.  This calculator suggests 100
amps through 2 feet of 6 gauge wire would generate about 8 watts of heat:

http://www.stealth316.com/2-wire-resistance.htm

You'd have to crank the engine for awhile before the heat would build
up enough to permanently damage the insulation.  Of course, if the
wire is in the center of a bundle, it'll heat up that much more
quickly, because the heat can't dissipate as well.

It's important to consider the voltage drop due to the resistance of
the wire.  The voltage drop is small for a short run of 6 gauge
wire.  About 0.08 volts across 2 feet of 6 gauge at 100 amps,
according to the above calculator.

In short, while it's not exactly a best practice, I wouldn't worry
about running a lot of current through a short length of 6 gauge wire
briefly, and the voltage drop probably won't be a problem, either.

Of course, wire with really high-quality insulation, like Tefzel,
will tolerate this sort of abuse better:

http://www.bandc.biz/electrical-wire.aspx
http://en.wikipedia.org/wiki/Tefzel