JB Weld versus Loctite for grubscrews

time2roll

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I've never stripped threads in a cast iron head, but I have in aluminum. I've learned to use a torque wrench.
LOL. Yup, used a tire impact gun more than a few times to torque heads on a cast iron block :cool:

I believe a 6mm bolt with 1mm pitch should have minimum 6mm or 6 full threads to utilize the full strength of the fastener.
With 4 threads we should be at half.
 

Hedges

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I believe a 6mm bolt with 1mm pitch should have minimum 6mm or 6 full threads to utilize the full strength of the fastener.
With 4 threads we should be at half.

And thread engagement varies with busbar thickness, also turns while tightening, which is how this whole "grub screw" and "Loctite" or "JB Weld" thing began. Actually, I think repairing stripped threads with JB Weld came before "Just glue the damn thing in once".
 

Butcher

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But isn't there a conductivity paste that could 'fill' the voids?

Yes, I do get there would be a relationship between clamping pressure vs surface area. I guess, what is the optimum surface area vs force. I suspect a soft surface would be better. Which stainless steel is not.

So keeping everything the same, using a copper stud and a copper top washer would allow more contact area with the same low clamping pressure that we are stuck with.

In the end, I'm working on my first battery and I'm just trying to do what is best for me. I own some metal machines that I can make most anything I want. I'm making the copper studs now and should be making some copper top washers soon [6mm hole large OD]. I'm not made of money but I have enough to pay with stupid ideas that pop up in my head.

I appreciate all the inputs so far.
 
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S Davis

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I red loctighted mine, I will report back when I can pull 250amps and check them with an infrared camera.
 

Hedges

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Paste wouldn't break through native aluminum oxide. Exposed bare aluminum was never meant to be an electrical conductor (except with welded, wire bonded, etc. metallurgical connections.)
There have been filler particles that are sharp, to break through. But I don't think for high current. Things like thin nickel coating on polymer balls.

Tin plated aluminum is normal for UL listed terminals.

Other style terminals allow a robust bolt to be used. Just not found on these repurposed cells.

online-ups-battery-500x500.jpg


Anything properly engineered would work.
 

Butcher

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I've tig welded aluminum and I understand how fast it oxidizes. I certainly would clean and apply paste ASAP. Obviously, this can't be a huge ordeal since I doubt if many have cleaned the area before they build their batteries.
 

Hedges

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Not a huge deal, but something of an ordeal.

Many didn't. Some then burned their fingers on the busbars (or at least saw high cell voltages reported by BMS and found hot busbars.)
After doing as you say, they reported busbars ran cold.

A couple people have had incinerated battery packs, and structures/vehicles. May have been other issues; we did our best at failure analysis and usually blamed it on some other error.
 

fafrd

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You do not happen to arm wrestle?
No, but the thread that stripped was especially shallow (and might have been used/worn).

These were my first cells and I started using the threads to top balance before I understood the importance of inspecting threads before doing anything else…
 

Butcher

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I do not think I want to glue the busbars/lugs to the contact pads. I have no issues with that type of epoxy securing the studs, but that's about it.
 
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