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Busbar current carrying capacity

NASA at one point required vendors to do everything using the metric system.
Then dropped the requirement, saving $100,000,000

Later they launched a couple probes to Mars (with a multichip module computer I was involved in.)

Unfortunately, orbit was meant to be 50 miles up, but instead they put it in a 50 km high orbit.
As they say, the rest is history.


Once, we were told we would need to learn Japanese. Now, looks like it will be Chinese.
 
There are ONLY 3 COUNTRIES still using feet, inches and Gallons that are not Real Gallons. A Gallon is NOT 3.78 litres it IS 4.54 Litres in REALITY... but when Big Oil Co's came up with that, the Government let it happen and called it a US Gallon.

What's a Yard ? It can be BEER but in measurements, it's based off the length of some long-dead kings arm, from the tip of his finger to his elbow... That sure is a sensible measurement isn't it... And feet, foots ohhhh that's even worse....

Let go back to the Medieval and grab a Firkin of Ale and ponder it while.
 
Hedges said:
"Later they launched a couple probes to Mars (with a multichip module computer I was involved in.)
Unfortunately, orbit was meant to be 50 miles up, but instead they put it in a 50 km high or"

See. You now feel so much better after confessing your part in this FUBR.
Click to expand...
 


No regrets. The stock options got me where I am today. :)

Anyway, bits in a computer don't know units. That was a software problem. I do hardware.

Given a few months before the twin probe following behind reached the Red Planet, NASA made sure they didn't make THAT mistake again.
So they made a different one instead.

As the probe descended toward the surface, a sensor in one leg reported it had just made contact. So the rocket motor shut off. At altitude.
Never rely on a single sensor. Sound familiar? No one would ever make THAT mistake again, would they??
 
Steve_S said:
There are ONLY 3 COUNTRIES still using feet, inches and Gallons that are not Real Gallons. A Gallon is NOT 3.78 litres it IS 4.54 Litres in REALITY... but when Big Oil Co's came up with that, the Government let it happen and called it a US Gallon.

What's a Yard ? It can be BEER but in measurements, it's based off the length of some long-dead kings arm, from the tip of his finger to his elbow... That sure is a sensible measurement isn't it... And feet, foots ohhhh that's even worse....

Let go back to the Medieval and grab a Firkin of Ale and ponder it while.
Click to expand...

We can't even agree on what the sport of "football" should be.
 
On the subject of busbar current carrying capacity... A question for the experts.

Since my two 280Ah batteries will go in my van, I felt it was best to have braided busbars to prevent stress on the cell terminals (studs). So I purchased these large braided busbars, rated for 250A, with M10 holes. I tried them (after filing and fine-sanding the contact surfaces) and they work OK (in a capacity test).

However, I am wondering if I could improve how the bars are attached to the terminals and the contact between the bars and terminals. The M10 holes, aside from being large, have rounded edges (result of the punching I assume) and require a large washer to ensure equal pressure on the busbar.

So I took one the spare busbars that I have (had to purchase ten, but need only six), and drilled holes (see pic) in two corners. I am convinced the contact area is larger this way and that the downward pressure from the nut would be more even.

But... the question: How big an effect do you think these holes (and their position) would have on the current carrying capacity of the busbar?
 

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Fpoet said:
Thank you, but the question remains.
Click to expand...
My guess is that either way will work. You have M10 screws so the busbar is going to be down well.
The rounded edge on the holes won't make much difference.

You could try using spacers to hold the busbar concentric with the hole - https://www.boltdepot.com/Product-Details.aspx?product=13780
You have to cut it to length.
And use large washers like you said.

If you drill the holes it will look a little odd but it should work good.

edit: I've got to stop editing. I reread your post and see you are saying the holes in the original busbars are 10mm. So the new ones must be 6mm.
So, the original holes should work ok.

changed spacer link to 6mm
 
Last edited:
Is the "whole terminal area must be covered" a critical thing here? I've seen folks using wiring with lugs in place of the flat rigid bus bars - and obviously the surface of the lug doesn't cover the entire surface of the terminal.
 
I don't think so.
Cross section of busbar (or cable) carries current along its length. Resistance and loss is proportional to Length / (width x height)
Contact between busbar and terminal area is the (width x height) part of that equation and Length is zero.
At contact, if the area is small, current crowds in to get through. That becomes a 3D problem to analyze thoroughly, but effect is small unless contact patch is really tiny.
If contact patch area is 1/4 of busbar (or cable) cross section, I still wouldn't be worried.
 
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