Author Topic: Which wires to use?  (Read 451 times)

Offline DaleAP

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Which wires to use?
« on: March 20, 2022, 01:33:50 PM »
In the process of the alternator upgrade, and the one thing that has me stumped is the wire size that should be used for the new sub-harness.

Following a great how-to from the U.S. forums and one guy made his own harness using 10 and 18 guage wires (diagram attached).
Looking through the stores around me though and they all come with mm measurements (both outer and MM2), as well as amp ratings.

Anyone able to tell me what I should be using? Given the alternator is 40 amp, and I have a fuse for 50amp, should the thicker wire be at least 50amp rated? Although that seems thicker than the 10 guage that the U.S. guy used.
Dale Porter
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Offline cravenhaven

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Re: Which wires to use?
« Reply #1 on: March 20, 2022, 02:06:12 PM »
You would get a voltage drop of approx 0.3V at 40A with 10awg wire. I think I would aim to use something like 6mm wire for that, but even then it only reduces the voltage drop by a third.
 
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Offline DaleAP

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Re: Which wires to use?
« Reply #2 on: March 20, 2022, 02:27:19 PM »
You would get a voltage drop of approx 0.3V at 40A with 10awg wire. I think I would aim to use something like 6mm wire for that, but even then it only reduces the voltage drop by a third.

When you say 6mm, is that the internal wire diameter (without the insulation)?
Dale Porter
1995 ST1100 ABS/TCS  :bl11

Past bikes: GPX-250 -> CBR-600F2 -> CBR-954RR -> VTR-1000
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Re: Which wires to use?
« Reply #3 on: March 20, 2022, 10:53:32 PM »
You would get a voltage drop of approx 0.3V at 40A with 10awg wire. I think I would aim to use something like 6mm wire for that, but even then it only reduces the voltage drop by a third.

When you say 6mm, is that the internal wire diameter (without the insulation)?

6 mm^2 wire is the cross-sectional area of the wire.

That means if you cut the wire, and look at the end there is 6 mm squared area of the metal conductor exposed.

https://www.engineeringtoolbox.com/wire-square-mm-diameter-d_1874.html


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Offline cravenhaven

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Re: Which wires to use?
« Reply #4 on: March 21, 2022, 09:13:09 AM »
Yep, you have to be a bit careful about wire sizes. Automotive wire is marketed by what size hole the cable will go through, so is a linear measure that includes the insulation.
I meant 6mm^2 wire as the cross sectional area of the actual conductor.
 

Offline Brock

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Re: Which wires to use?
« Reply #5 on: March 21, 2022, 01:27:12 PM »
6mm^2 wire is about 2.8mm diameter,so 3mm + diameter would be good
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