Hi,
How much current can copper strip handle, DC current, provided the length L, width W, and thickness t?
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The search feature is a wonderful thing
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If you did some experiments and posted your results, it could help the community immensely.
But for what insulation is the copper wire in that table?
Additionally that is for copper wire and not copper strip
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It’s cross section area that determines current carrying capabilities, not geometric shape.
I don’t think so.
If it was obtained experimentally, a wire was simply placed down on a table, and current was sent through it to see how hot it got. Convection occurs. The heat transfer coefficient is a function of the geometry of the object, in which this case would be considered a cylinder. How to calculate the heat transfer coefficient for convection of a cylinder has a known formula.
Also if this is copper insulated wire, NEC 310 could be used, or straight from the manufacturer. Copper ampacity is much more well understood than nickel.
Saying that a copper wire (with insulation) under convection with this particular cross sectional area, than a copper strip with the same cross sectional area, will have a different heat transfer coefficient, because it’s shape would be considered a “flat” plate over a cylinder. Technically it would be considered a rectangular box with four flat plates. The heat transfer coefficient of the four plates is different than that of the cylinder.
Thoughts?
I’m surprised a generic formula hasn’t been developed yet. I’m getting closer, but the formula I’m getting is not producing good results.
Assume that there is no convection within the battery box (or that the thermal resistance of it is essentially zero), so the insulated strips is more or less in surface contact with the box walls and conduction between the cells, the strip, insulation, and the box. We will have to assume that the box is at the same as ambient temperature. We have to because convection of the box cannot be determined, it’s a function of temperature of the box. Regardless when doing this, the formula I get is not producing good values.
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As you can see the results I’m getting are obviously not correct. So if anyone finds anything wrong, please let me know! In fact I actually hope someone finds something wrong.
I even consider if I have a P parallel packs and S series connections. So if I had like 5S3P pack for a power tool battery, I would have 6 series connections and 1 parallel connection in contact with the box wall. If I consider heat transfer from all 7 of these pieces, even then I don’t get good values for the current allowed through a strip.
Some of my analysis in those photos, are when I was trying to go down that path, and may no longer be relevant. But you can see how I get my formula. It’s just some of the values I don’t use.
The chart @b264 graciously bestowed and updates is pretty accurate based on my tests of nickel sheet / copper cable. Not sure its worth trying to re-invent the wheel.
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Can we use PCB trace calculator?
https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-pcb-trace-width
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Oh, I’ve accidentally set length to 35" instead of 35mm, but you get the idea. Seems like copper is very conductive.
That’s a bit closer probably, but does not take into consideration heat transfer from cells underneath it.