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Old Jul 20, 2004, 08:05 PM
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Wire gauge amps

Hey guys... i was wondering if anyone knew about what various gauges of wire could handle as far as amps. Ive noticed one website show 16 gauge wiring handling 25 amps but then again some li-poly packs having 20 gauge wiring and saying they could discharge at 20-24 amps... so what am i missing
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Old Jul 20, 2004, 09:39 PM
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How about a wire manufacturer's data? Here ya go:
Current carrying capacity
The varying capacities you are seeing on different websites might be due to the ability of the wires insulation not to melt beleive it or not!!!
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Old Jul 20, 2004, 09:57 PM
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hm so why are these li-polys rated at 20-24 amps but have 20 gauge wire on them?
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Old Jul 20, 2004, 10:10 PM
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I can only speculate as to why...

They probably assume that you won't be dumping the battery at its maximum rate for the entire time. That chart is just a guideline. It doesn't say how LONG it takes to heat up the wire to the point the insulation melts, mainly because they don't know what sort of forced cooling (or not) there is around the wires.

I'm new to electric R/C aircraft, but not electronics. I can only speculate that people wouldn't want the extra weight of 12AWG wire on their battery packs. If you think you might be dumping these packs at their maximum rate for long periods of time, definitely stay away from them!

If you can, write the li-poly manufacturer and ask them why they use 20AWG in their packs while saying 24 amps will be just fine and see what their answer is. I'd be curious to hear their response.
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Old Jul 20, 2004, 10:25 PM
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lol now im kinda scared to go onto a corsair project with brushless motors and some 2400mah li-polys.... i wonder how many amps brushless motors take...
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Old Jul 20, 2004, 10:34 PM
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That web page shows data for single conductor of given size.
Since we use high strand count wires they can carry more current than single piece of copper.
Do a search, there were some data here about our RC wire amp capabilities.
For a quick look see go here : http://www.castlecreations.com look under products, accesories, wire.
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Old Jul 20, 2004, 10:44 PM
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Hey check it out... what kinda amps do brushless motors pull... i wanna build a brushless/li-poly corsair Also... what exactly makes brushless motors better? are they faster or more powerful or what?
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Old Jul 21, 2004, 08:24 AM
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Quote:
Originally Posted by Hovertime
Since we use high strand count wires they can carry more current than single piece of copper.
The electrical behavior of DC currents or low frequency AC currents will be the same in an equal cross sectional area, i.e the same wire guage no matter if it is solid or stranded. The advantage of stranded wire is that it more flexible. In any case, the insulation is the limiting factor in current carrying capacity. All of the flexible wire insulation that I am aware of will melt (or burn) before the copper or aluminum will!

I know that sounds odd, but think of it this way: thicker wire = less resistance = less power dissipation = less heating up.
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Old Jul 21, 2004, 11:40 AM
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And what about surface current carrying capacity?
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Old Jul 21, 2004, 03:45 PM
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My understanding is that the lower the frequency, the deeper into the conductor (from the surface, a.k.a skin depth) the current is carried. At higher frequency, you wind up with most of the current carring capacity at the surface, but multi-stranded and solid wire will behave the same at D.C. or low frequencies because their cross sectional areas will be about the same for the same wire gauge.
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Old Jul 21, 2004, 03:58 PM
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So do we have overrating of wires in RC?
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Old Jul 21, 2004, 04:12 PM
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Remember current is conducted on the outside surface of the wire. I know what you mean about the rating. I think the cover melting will occur if the ESC goes into a dead short. If it is something you are worried about, stick a fuse between output of ESC and the motor.
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Old Jul 21, 2004, 04:16 PM
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Castlecreations, http://www.castlecreations.com ,
carries size 16 that can handle up to 40 amps, Go figure it out
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Old Jul 21, 2004, 04:22 PM
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Quote:
Originally Posted by PenguinWaddle
hm so why are these li-polys rated at 20-24 amps but have 20 gauge wire on them?
Over the last 20 months I have found that the claims by LiPo manufactures should be taken with a grain of salt. Castle creations say that their 20 gauge wire is good for 15 amps so this is probably what the Li Po can safely deliver and still have a long life.

Ken
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Old Jul 21, 2004, 09:08 PM
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Oh! I finally see the source of confusion about this surface carrying thing! Ignoring skin depth, frequency and all that techie stuff...

The reason why the stranded wire of the same gauge doesn't carry more current is because from the point of view of the electrons, the stranded and solid wire is the same! More electrons are carrying charge at the surface of a solid wire, basically because they are trying to get away from each other. Since all the little strands are touching each other (conducting) the electrons in stranded wire want to escape to the surface of the outer most strands, therefore behaving like the same gauge of solid wire. Errr... hope that cleared it up...

As for R/C wire being overated, can't say. But as with anything... buyer beware!
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