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Wire Size And Current Capacity

10215 Views 7 Replies 4 Participants Last post by  shoz123
I figured I can add this table to help people pick the right size power supply wire for their amps. This is from one of my textbooks.


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These are for continuous use power ratings. You will notice the 6 ga is not rated for the 150A or 450A peak current draw the start will pull.
also notice that the first chart is for a 1000 ft run... those numbers are highly conservative... the second graph is good, but i would recomend bigger wires than some of the ones they reccomend.

and it is always better if you use bigger wire than you are required.

good stuff though
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Actually the 1000' is the resistance rating, the amp ratings are for the standard 50'.
that is still rediculously conservative... 4/0 can hold WAY more than 230 amps, i think that 230 amps might even be able to go through 1/0.

but like i said before, those are petty much just suggestions, and it is always better to se bigger than required... if you want to see something really interesting i can dig up the chart of how much resistance the actual wire itself induces. its pretty interesting, alot more than you expect
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Yes the chart I posted is definitely conservative. I guess the key word in it is Safe and yes its for constant current.
Voltage drop is the key and has a definite proportional relationship to wire size. FWIW my '97 will momentarily draw +450A when starting. This is through 2ga wire and to a battery in the trunk. It is also routed through a 250A fuse. The amp draw will quickly drop to 150A and maintain that as long as I crank the engine.

There is no way the 130A alternator will put out that amperage on a continuous basis through the 6 ga wire that is OEM.

Probably one of the best things you can do to your car is increase the alternator to fuse box wire to 4 ga and increase the battery to starter wire to 2 ga, Negative cables should be increase to 2 ga also.
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