Conductor Current Ratings [SRO]

So when we look at these wire ratings, most are done at 1m, 10m or 100m. Those create huge variations in current carrying capacity right?

I’m curious to know what the actual safe continuous and peak current carrying capacity of 10, 12 awg etc at less than 16 inches, which covers most everything we do. I don’t think we can get this data without bench testing and temp measuring

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@mutantbass based on that test, I’ve updated 0.15mm x 12mm to 17A/25.5A/34A and the rest of the sizes of nickel accordingly.

If anyone thinks these could be better still, let me know :slight_smile:

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Ive seen some calculators that approve a 12awg wire for 100 amps at 1 foot distance at 24V.

I dont have anything that I can test on the bench to do constant draw. But I think those values are much more appropriate for the 20mm distance between cells.

Curious, is the amp capacity fairly linear as the nickel grows in width or thickness? Does double or triple the thickness or width have double or triple the amp capacity? I have 10, 15, 25 and 50 mm wide 0.2 nickel for that reason.

With these adjustments to the nickel, applying the same to the copper wire, 60 amps looks much more appropriate for 12 awg wire if not still a bit low if the distance is really short. I don’t think I have a wire on more board longer than 10 inches.

So with short phase leads, I’m thinking the 12 AWG motor wires were used to are more than capable for up to 80 amp motor settings if the wiring isn’t silly long.

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Hey fellas I thought I might submit this chart FYI. I’m planning on using copper bus bars for a couple of upcoming battery builds and came across this when trying to decide on thickness/width for the bars:

Pretty relevant to this thread although I don’t see a whole lot of people using these in their battery builds. Don’t for the life of me understand why tho. PCBs seem to be the preference although they’re immensely more expensive in my estimation. U can get 1/8" x 1/2 (rated at 200 amps continuous) for ~$5 CAD per foot. This and some cell holders and ur golden at a fraction of the cost of PCBs. My $0.02.

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https://www.elektromodellflug.de/oldpage/hochstromst/hochstromstecker.htm

Amp rating of bullet connector
Amp rating of RC connectors
Amp rating of XT60 XT-60 XT90 XT-90
Amp rating of Deans connector
Keywords keywords keywords

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https://dronelab.se/siliconewire.html

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Nice find @mutantbass

Should this test affect the numbers in the chart up top?

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Wow 16awg can take 90 amps for 10 seconds, that’s impressive haha

Chart looks good albeit a tad conservative which is fine for most people. I also had an aha moment the other day when I was thinking about changing the connectors on my unity. Follow my logic:

  • the 3.5mm connectors on the unity fit an xt60 connector perfectly. (xt60 is just plastic surrounding 3.5mm connectors lol )
  • even if we take the minimum 60a rating for the xt60, we can conclude the 3.5mm bullets will do 60a continous
  • but the vesc 3 phase is only active 2 at a time, so really we are talking 100a+ continuous on those 3.5mm bullet connectors on the focboxes so there is no good reason to change those 3.5mm connectors.

I think people are going serious overkill on their wire gauges and connector sizes. Its a little too “blue collar” if you know what I mean. There is something beautiful about consciously picking components that will give you a 20% headroom rather than going as big as you can just for the sake of it.

rant over/ lol

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Do you think we should raise the right column (red) but leave the left (green) column?

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Maybe just add another “10 second burst” column? and take the values from the drone chart

Is it safe to conclude that unless its offroad emtb stuff, 3.5mm/4mm bullet, xt60 connectors and 14/16awg wire is plenty for most boards?

I don’t want to make generalizations about what people want to build, but for my boards, an XT60 for each motor’s ESC and an XT90 on the battery with 12AWG all around is way more than sufficient. With 12AWG and MR60 motor phase wires, which would probably even be fine at 14AWG.

The battery serial connections I would beef up, if anything. Dual 14AWG series connections means those will be cool whenever the 12AWG going to the ESC is heating up, as a safety factor, if you have a failure, it’d be better if it was outside of the battery.

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It’s my opinion that more than 3 columns is too much information to present and makes it more confusing for noobs.

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Two columns is already confusing enough for me. I second that opinion

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@b264

Another interesting video

quick points:

  • at 120a, going from 12awg to 14awg @ 10cm length results in only 5w loss :scream:
  • at 40a, going from 18awg to 20awg @ 10cm results in only 1w loss :scream:

and this is continuous. Really interesting video.

I am going to 28awg on my Trampa.

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That was a good find :ok_hand: 28awg is the future!

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LoL this guy totally does not consider that if your wire is burning up “only a couple watts” then the wire will be getting REALLY hot, especially if it’s inside silicone and inside an enclosure or battery with no way to breathe. After a few seconds, the temperature of the wire will begin to skyrocket, and then all of his testing goes out the window, because of that tiny, but ever-important,

Screenshot from 2020-08-17 01-09-12

Once the wire temperature increases, it increases the resistance, which increases the voltage drop, which increases the amount of power lost to heat, which increases heating, which increases the temperature … which thus increases the resistance, which increases the voltage drop, which increases the amount of power lost to heat, which increases heating, which increases the temperature… which thus increases the resistance, which increases the voltage drop, which increases the amount of power lost to heat, which increases heating, which increases the temperature … and so on

So you have a feedback effect which he has completely disregarded.

If you are only running your skate for 4 seconds at a time, and you let it cool for 5 hours between runs, then you can totally use 28AWG wire for your 4WD offroad emtb.

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@bollen do you know how to relate the cross-section to the width? I’ve always seen copper braid sold by width.

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