Cell terminal bolt torque - you might be wrong!

Luthj

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Assuming they test good, I would just pay to have the vendor laser weld studs to the cells.

I am getting a few hundred pounds of compression from my m6 studs. Of course the holes were properly tapped, which makes a difference.

1/4" bus bars need to be polished flat unless you have a 5/8" stud you can torque to the max.
 

Hedges

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I highly doubt you can spot weld aluminium (especially in that form factor), especially with DIY means only.

Each time I saw those kind of welds it was either TIG or laser.

Does TIG do the job fast enough that cell terminal doesn't get too hot and damage the cell?
My amateur buzz-box stick welding gets the work piece too hot to touch.

I'm always looking for excuses to buy more tools.

 

BiduleOhm

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I don't know. I'm pretty sure you can do it if you have a lot of experience and you let the terminal cool down between each part of the weld but that would require a loooot of time if it's even possible...
 

Luthj

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Its pretty hard to weld aluminum terminals as they are so thermally conductive. The laser welding works as its a high power process with a small weld affected zone, so time and thus heat input is minimized (strangely enough reducing welding power increases total heat input).
 

HRTKD

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I think I could spot TIG weld it, but the problem would be that the bus bar would have to shrink in width and length to allow enough access to the top of the terminal. I don't know that I would be willing to give up covering the entire terminal plate.

I have very little experience with my TIG welder. As in none! It just arrived a couple weeks ago and I've been assembling supplies. Welding gas last week. 3/4" steel plates for the welding table today.
 

Hedges

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So laser it is.


TIG? Unlike that laser welder, don't see where to connect the gas bottle here


Or maybe just a brief short between positive and negative, 20,000A is about 100x what my buzz box can do?
 

fafrd

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Well, since Amy explanation we now know those terminal werent designed to be drilled and threaded but to be welded; that explains a lot...

Now, I can think of one solution if you want more clamping but it would be cumbersome: clamp the busbars with some kind of fixture between the top of the busbar and the bottom of the cell.
Wouldn’t that just deform the cell from below?

Strikes me as a really bad idea (we’re all having enough problems with cell deformation / expansion as it is...).
 

Gazoo

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Well, since Amy explanation we now know those terminal werent designed to be drilled and threaded but to be welded; that explains a lot...

Now, I can think of one solution if you want more clamping but it would be cumbersome: clamp the busbars with some kind of fixture between the top of the busbar and the bottom of the cell.
Actually that was one of the first thoughts that came to my mind when I stripped the stud in my cell. But then I thought how much force would the terminal be able to take and I envisioned the terminal going down into the cell.
 

Luthj

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So laser it is.
Yeah, thats not a laser welder. Its a pulsed tig with very high current.

That being said, pulsed high current tig (called "cold" welding), would probably work just fine. You do a pulse ever 2 seconds, and gradually work your way around.
 

fafrd

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These EVE 280Ah cells are being primarily used in other industrial applications (EVs? PV Farm Storage?) - does anyone know what connection solution to the aluminum terminals is typically used in those other use-cases?
 

Luthj

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On EV applications they appear to weld a bus bar directly to the terminal.
 

HRTKD

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So laser it is.


TIG? Unlike that laser welder, don't see where to connect the gas bottle here


Or maybe just a brief short between positive and negative, 20,000A is about 100x what my buzz box can do?

The second welder you linked to won't work. Probably. Most TIG welding with aluminum is AC TIG not DC TIG. That machine only does DC.
 

Hedges

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Yeah, thats not a laser welder. Its a pulsed tig with very high current.

That being said, pulsed high current tig (called "cold" welding), would probably work just fine. You do a pulse ever 2 seconds, and gradually work your way around.

Oops, "Laser Cold"?

Here we go. Now just have to see what turns up at the local auction for a better price.


This posting for 300W suggests a 400W unit needed for aluminum.
I think the application they show is metal shape of neon signs. That would be thin sheetmetal compared to cell terminals.


Or, buy some flash lamps, quartz tube, bottle of CO2, half-mirrored glass ...
 

Luthj

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DC Electrode positive works for AL, but you need a big electrode to prevent them from burning out in a few seconds. If the machine is high current pulse type, then AC vs DC EP may not matter.
 

BiduleOhm

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Wouldn’t that just deform the cell from below?

Strikes me as a really bad idea (we’re all having enough problems with cell deformation / expansion as it is...).
Actually that was one of the first thoughts that came to my mind when I stripped the stud in my cell. But then I thought how much force would the terminal be able to take and I envisioned the terminal going down into the cell.

Never said it was a great idea... 😄
 

Luthj

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No wonder they need to pay-up for well-matched cells...
Well, taking apart the pack is pretty labor intensive. There aren't many components buried that deep that don't get high level quality assurance.

Besides running at 1-2C rates is not forgiving.
 

Honuz

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I do not quite follow what's happening with terminals, by the Eve description, it's clear (for me) that 8 N.m is the internal resistance to torsion of the terminal.
Just using between 3 and 4 N.m should be sufficient and with a comfortable distance of the "not to be used" 8 N.m., is there a need to go higher...?
3 N.m should be like 300gr on a one meter stick.
 
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