Advice on rethreading a welded stud

[InMyImage]

Looks like the bad experiences with welded studs has bit again… My Lishen 270ah’s came with welded studs from the “group buy” organized by “he whose name cannot be spoken”… they were supposed to be M8 but only ended up being M6 and I’ve seen some comments indicating that they aren’t even quite M6.

Anyhow, these studs threads suck, several came out in nice spirals as I was taking a pack apart and every single stud has some amount of damage so I’m going to have to rethread them all of them. Any advice on whether I should try M6 or just drop to M5.5 or even M5. It’s a mobile install in a fifth wheel trailer so I’d prefer to leave them as big as possible.

Before anyone asks, they were torqued, just hand tightened with a ratchet enough to be snug because I still haven’t actually finished the system and figured out the final system organization. Was working on trying to parallel balance the pack again and this happened when disassembling the pack. Afraid to disassemble the other pack until I have the die in hand and know it works with the studs on the other pack or if I need to cut these damned terminal studs off and get back to the original terminal.

Thanks

 

[Hedges]

Studs ... threads came out in spirals? You mean the threads stripped off a male stud?

I doubt you can apply sufficient torque to thread a stud without either shearing it off the terminal, or worse rotating terminal in the case. Maybe if you can restrain the stud with thin vice-grips while threading the rest of it.

As best I can tell, these cells were designed to have busbars laser-welded to them.

 

[InMyImage]

Studs ... threads came out in spirals? You mean the threads stripped off a male stud?

I doubt you can apply sufficient torque to thread a stud without either shearing it off the terminal, or worse rotating terminal in the case. Maybe if you can restrain the stud with thin vice-grips while threading the rest of it.

As best I can tell, these cells were designed to have busbars laser-welded to them.

Nope, the threads of the laser welded on studs are stripped right off. They obviously are a very poor grade stainless steel if they actually are stainless steel…

 

[rodrick]

The terminals will only take about 7 nm safely I had a cell that wasn’t threaded for the stud and trying to thread it wasn’t a good option to much torque on the terminal can you make a small clamp on cable like a auto battery cable just smaller or a block that would clamp down with a threaded hole

 

[HRTKD]

Cut off the stud, drill it out and tap to fit 8mm threads? That would be my last resort. Rethreading for 5.5mm would be my first option. As stated above, you'll have to do something to secure the base of the welded-on part of the stud to ensure it doesn't apply any rotational force to the cell terminal.

 

[InMyImage]

Another solution occurred to me to use a die to make sure the top threads are clean and then use a coupling nut, with their longer length they shouldn’t have any problems putting enough torque on the on the busbars even with no threads available on the bottom portion of the welded stud.

 

[Hedges]

But busbars must bear on the cell terminals. Don't have current conduct through stud or nut, which are quite high in resistance.
(If I'm correct in thinking you're up to some funny structure.)

 

[time2roll]

Yes run a 6mm die down by hand. Trick is getting it set in correct at the start as damaged threads can lead the die on a bad path.

 

[rodrick]

Something like this cut in 2 hole pieces replace the screws with Allen head set screws for more clamping force

 

[rodrick]

If they are welded they will have conductivity not as good as the face connection but may still work on lighter loads I would test them and make sure no heating at terminal due to high resistance but on a lighter load it may work,better than trashing them if the metal is that soft that it is pealing threads rethreading most likely will not work well either

 

[Hedges]

Something like this cut in 2 hole pieces replace the screws with Allen head set screws for more clamping force

Good for joining two copper or aluminum conductors.
Use that to connect anything to stainless stud, and the stud will make a nice heating element at high current.

 

[rodrick]

Agreed it will only work on low c rates their will be some contact on the face when installed so not all of the current will go through the stud use some antiox press it down tight on face and test it

 

[InMyImage]

But busbars must bear on the cell terminals. Don't have current conduct through stud or nut, which are quite high in resistance.
(If I'm correct in thinking you're up to some funny structure.)

Sorry not sure what you are referring to?

My goal is to end up with a usable welded stud and attach the busbars some as you normally would, although I am leaning towards using a coupling nut instead of a standard nut that way it uses all available threads vs just a couple above the bus bar and balance leads.

 

[InMyImage]

Something like this cut in 2 hole pieces replace the screws with Allen head set screws for more clamping force

based on the follow-up discussion regarding this, I doubt it’s something I’d consider given that when the battery power does kick in, it will generally be sucking 100-150 amps per battery pack.

 

[InMyImage]

And based on comments found in other threads it also sounds like I’ll be better off with standard zinc plated nuts vs stainless steel nuts right?

 

[HRTKD]

And based on comments found in other threads it also sounds like I’ll be better off with standard zinc plated nuts vs stainless steel nuts right?

What was the reasoning in those other threads?

 

[73powerstroke]

Looks like the bad experiences with welded studs has bit again… My Lishen 270ah’s came with welded studs from the “group buy” organized by “he whose name cannot be spoken”… they were supposed to be M8 but only ended up being M6 and I’ve seen some comments indicating that they aren’t even quite M6.

Anyhow, these studs threads suck, several came out in nice spirals as I was taking a pack apart and every single stud has some amount of damage so I’m going to have to rethread them all of them. Any advice on whether I should try M6 or just drop to M5.5 or even M5. It’s a mobile install in a fifth wheel trailer so I’d prefer to leave them as big as possible.

Before anyone asks, they were torqued, just hand tightened with a ratchet enough to be snug because I still haven’t actually finished the system and figured out the final system organization. Was working on trying to parallel balance the pack again and this happened when disassembling the pack. Afraid to disassemble the other pack until I have the die in hand and know it works with the studs on the other pack or if I need to cut these damned terminal studs off and get back to the original terminal.

Thanks

I would get those lug stud clamp lugs that home depot sells. And clamp every single one. Only safe option. Cut your losses and don't make a bad deal worse.
Try and tap it and twist or make things worse. Sorry to hear about all this.

 

[InMyImage]

What was the reasoning in those other threads?

That stainless steel nuts on stainless steel screws/bolts has a higher chance of damaging threads.

 

[InMyImage]

I would get those lug stud clamp lugs that home depot sells. And clamp every single one. Only safe option. Cut your losses and don't make a bad deal worse.
Try and tap it and twist or make things worse. Sorry to hear about all this. View attachment 103996View attachment 103997View attachment 103998View attachment 103999

Thanks, am familiar with lugs like that and actually did consider using them after seeing EVE’s new welded terminals but because these clamps down on cable I wasn’t sure about the connection. For this particular issue it could still be interesting just to eliminate or at least cut down on the wear and tear of the studs.

 

[73powerstroke]

Thanks, am familiar with lugs like that and actually did consider using them after seeing EVE’s new welded terminals but because these clamps down on cable I wasn’t sure about the connection. For this particular issue it could still be interesting just to eliminate or at least cut down on the wear and tear of the studs.

Be really careful and use quality dies and cutting oil then.