Cell terminal bolt torque - you might be wrong!

[Luthj]

Thread lockers won't really change pull out strength a lot. The highest strength threadlocker will be the strongest adhesive.

If you are concerned with pull out, mix up some jb weld or similar and coat the threads prior to assembly.

If you have a lower viscosity epoxy you can put a drop at the bottom of the hole and slowly thread the stud in. Any excess should gradually push out the top of the threads.

 

[HaldorEE]

Yes, I’ll use Loctite. I want this to be ‘one and done’!

what length grub screws are you all using?

it seems like I’ll need a minimum of 15 or 16mm if I want the freedom to attach 2 busbars and/or lugs leaving space for a nut, washer and lock-washer, but I’m thinking of going with 20mm to have more margin.

I found some aluminum grub screws but they are slotted rather than hex and I don’t yet know the cost.

These yellow-zinc costed hex grub screws only come in 23mm (at least from this outfit) but I’m not overly-concerned about height and the price seems reasonable ($0.51ea w/o shipping): https://www.belmetric.com/m6x10-coa...p-10727.html?zenid=c3gjqt75i3j03cm013igt00u96

Widest availability for stainless but I’m thinking reducing whatever marginal risk I have of galvanic corrosion within the aluminum terminal may be a higher priority to me than lowering post height by a few mm...

Anyone know if there is anything to be concerned about with ‘yellow zinc’ as opposed to the grey/silver type?

I am using 20mm long stainless steel screws. I am using zinc plated carbon steel nuts to avoid galling with stainless steel against stainless steel. I learned my lesson about doing that testing the Belleville Washers.

 

[HaldorEE]

Interesting. How are you thinking this would compare to Loctite and/or JB Weld?

Stronger and more permanent than Loctite but compatible with remaining threads (compared to JB Weld which may not be)?

Do you know if anyone on the Forum has used this on M6 aluminum terminals yet?

Red locktite is the stuff to use. It is what I use when I don't ever want to remove a bolt again. It takes heat to get it to let go.

 

[fafrd]

Thread lockers won't really change pull out strength a lot. The highest strength threadlocker will be the strongest adhesive.

If you are concerned with pull out, mix up some jb weld or similar and coat the threads prior to assembly.

If you have a lower viscosity epoxy you can put a drop at the bottom of the hole and slowly thread the stud in. Any excess should gradually push out the top of the threads.

I think I am concerned about pull-out. If JB weld or low-viscosity epoxy will form a bond between the grub screw and the sidewalls of the aluminum thread which will provide pull-out strength that goes beyond the which the aluminum threads can provide themselves, I think that’s the way I want to go.

I’m not terribly worried about locked threads becoming unlocked and slipping / turning, I’m not thinking of any use case where I’ll ever need to remove a grub screw once attached, and I am concerned about grub screws pulling out under torque, so permanently gluing my grubscrews in in the strongest way possible is my goal.

And if those glued-in grub screws do ever pull out, sounds like an M6 or M8 Helicoil remains a viable fall-back / recovery option...

 

[ArthurEld]

I've been using studs for months without loctite.
The only reason I want to use thread locker is for pull out strength.

I'm going to try JB weld on the stud I pulled out.
If that can handle 40 inch pounds, I'll stop worrying about pulled out studs.
I'm only torqing to 35 inch pounds

 

[ArthurEld]

This seems good for stud welding - https://www.jbweld.com/product/marineweld-twin-tube

JB weld recommends it for aluminum and it is the highest strength

 

[fafrd]

I've been using studs for months without loctite.
The only reason I want to use thread locker is for pull out strength.

I'm going to try JB weld on the stud I pulled out.
If that can handle 40 inch pounds, I'll stop worrying about pulled out studs.
I'm only torqing to 35 inch pounds

I’ll wait to hear your results if you’ll be trying JB Weld relatively soon. I’m not in a rush now that I’ve characterized that my cells perform well (and uniformly) under load so I want to take my time to recover from these hiccups with a burned-out BMS and stripped / worn threads correctly...

 

[ArthurEld]

I know the feeling. The short I had knocked the wind out of my sails for a while.

 

[fafrd]

I know the feeling. The short I had knocked the wind out of my sails for a while.

Yeah, saw those pics. I’ve been lucky so far in avoiding a similar mishap with exposed busbars & bolts, but those pics made an impression on me.

There have been more times than I want to list when assembling or disassembling cells I’ve positioned a tool or started to position a tool, realized that if it slipped it could cause a short like you experienced, and decided I should approach the entire matter from another angle where an unexpected slip would fall harmlessly to the side...

 

[Gazoo]

This seems good for stud welding - https://www.jbweld.com/product/marineweld-twin-tube

JB weld recommends it for aluminum and it is the highest strength

I thought the original JB Weld has the highest tensile strength. There was a reason I passed on the marine weld stuff but I don't remember what it was.

 

[ArthurEld]

The regular JB Weld is the same strength. But when I go to the website and put in aluminum for the material it sends me to the Marine one.

There are a few youtubes of guys trying to make threads with JB Weld. It failed.

 

[HRTKD]

The regular JB Weld is the same strength. But when I go to the website and put in aluminum for the material it sends me to the Marine one.

There are a few youtubes of guys trying to make threads with JB Weld. It failed.

Might as well try some hot glue down the terminal hole.

 

[Gazoo]

The regular JB Weld is the same strength. But when I go to the website and put in aluminum for the material it sends me to the Marine one.

There are a few youtubes of guys trying to make threads with JB Weld. It failed.

I saw those videos. All I can tell you is using the standard JB Weld I have been able to apply 3nm torque. And my situation is the same as yours with the threads, otherwise known as beautiful memorabilia, that came out of the hole. Wasn't that a wonderful sight to behold....not!

 

[BiduleOhm]

Yeah, saw those pics. I’ve been lucky so far in avoiding a similar mishap with exposed busbars & bolts, but those pics made an impression on me.

There have been more times than I want to list when assembling or disassembling cells I’ve positioned a tool or started to position a tool, realized that if it slipped it could cause a short like you experienced, and decided I should approach the entire matter from another angle where an unexpected slip would fall harmlessly to the side...

Take some cardboard and cut a hole big enough for your socket or whatever, that way you can cover everything who isn't the nut you're working on; cheap, easy and foolproof

 

[ArthurEld]

Take some cardboard and cut a hole big enough for your socket or whatever, that way you can cover everything who isn't the nut you're working on; cheap, easy and foolproof

That is an great idea. You're a battery surgeon

I've been holding on to a bunch of different sizes of cardboard to keep things covered.

Something else that is probably much safer is to take off the busbars.
If you don't need them for a long time of if you plan to take them of, get them off.

 

[ArthurEld]

I've been thinking a lot about about these damn terminal threads.
I want my busbars held down tight.
It is hard for me to believe people are using these wimpy threads to hold down .25 think busbars and running a lot of amps through them.

 

[BiduleOhm]

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.

 

[Hedges]

People have been spot welding nickel plated fuse strips on the small cylindrical lithium cells with DIY spot welders.
Do we need a DIY laser to do aluminum welding without cooking the cell, or is another method used?

 

[BiduleOhm]

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.

 

[ArthurEld]

I think helicoils would work but I don't know if I want to put in 132 of them.