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I WARNED YOU ALL! MB31/MB30 huge issue terminal snapping off

That is why I said one little spot at a time. If you hit it with higher than usual current, it will take only a few seconds to fuse a single spot. Then cool it. Repeat until all the way around. Not going to heat up the whole cell that way. If you use low current, it will take too long to fuse and allow heat to escape into the cell. Even aluminum has thermal resistance. This technique worked great on a thin aluminum generator end casting the other day. With lower current I was getting nowhere.
Not so sure...
This from other thread where he drilled and tapped:
From my first mistake/repair attempt I've been able to discern that the lugs are not that thick and there's some sort of rubber mat underneath the lug, separating what ever's under it from the lug. (watched as many videos on the batteries as I could find trying to see if I could see any manufacturing videos - found a couple and yeah there's a protecting layer of rubbery something under the lugs - verified what came out on the drill bit - a thick gooey stuff).I took very careful measurements from the top of the lug to the bottom of the hole I'd drilled and threaded in the dead battery. It's 5mm.


It is only 5mm from the top of the lug to the bottom of it, and it sits on a rubber isolator - that you don't want to melt, because magic smoke will emerge..
 
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yeah it was discussed and like I said even with my miller setup in advance and running a couple of practice tries on some junk cells of the same manufacture it would be dicey. i think laser is the way to go and even then I would still want to practice on a couple of junk ones.
 
Not so sure...
This from other thread where he drilled and tapped:
From my first mistake/repair attempt I've been able to discern that the lugs are not that thick and there's some sort of rubber mat underneath the lug, separating what ever's under it from the lug. (watched as many videos on the batteries as I could find trying to see if I could see any manufacturing videos - found a couple and yeah there's a protecting layer of rubbery something under the lugs - verified what came out on the drill bit - a thick gooey stuff).I took very careful measurements from the top of the lug to the bottom of the hole I'd drilled and threaded in the dead battery. It's 5mm.

It is only 5mm from the top of the lug to the bottom of it, and it sits on a rubber isolator - that you don't want to melt, because magic smoke will emerge..
Yeah, i read that story too. I would still try that if I was in that situation. Carefully. With a milling machine and endmill for drilling out old threads.

yeah it was discussed and like I said even with my miller setup in advance and running a couple of practice tries on some junk cells of the same manufacture it would be dicey. i think laser is the way to go and even then I would still want to practice on a couple of junk ones.
Oh, I know it would be dicey, and I won't encourage anyone else to try it, but that broken terminal sort of makes it a junk cell anyhow. Not a lot to loose unless someone just went nuts with the heat. I would try it if I had a broken one but I hope I never need to.

By the way, anybody know where to buy a suitable terminal welding laser rig for a decent price? Not that I need it, just curious.
 
That is why I said one little spot at a time. If you hit it with higher than usual current, it will take only a few seconds to fuse a single spot. Then cool it. Repeat until all the way around. Not going to heat up the whole cell that way. If you use low current, it will take too long to fuse and allow heat to escape into the cell. Even aluminum has thermal resistance. This technique worked great on a thin aluminum generator end casting the other day. With lower current I was getting nowhere.
If you are lucky with a pulse setting on your (in my cae Jacis) TIG machine you can find the right spot in your settings and then rinse and repeat.
Laser does the same thing but faster with a much higher impulse power and better targeted but hell yess, I would try this when it happened to me.
Fingers crossed: I need to assemble 20 packs of 4 batteries to create 5 battery strings of 16cells.
 
Oh, I know it would be dicey, and I won't encourage anyone else to try it, but that broken terminal sort of makes it a junk cell anyhow. Not a lot to loose unless someone just went nuts with the heat. I would try it if I had a broken one but I hope I never need to.
I have (so far) never snapped a cell terminal - however I have avoided the large EVE terminals with the double bolt set up.
If I had a snapped terminal - rather than tossing the cell, I would do a shallow drill and tap on the MM and be done without heat generated.
 
Yeah, i read that story too. I would still try that if I was in that situation. Carefully. With a milling machine and endmill for drilling out old threads.


Oh, I know it would be dicey, and I won't encourage anyone else to try it, but that broken terminal sort of makes it a junk cell anyhow. Not a lot to loose unless someone just went nuts with the heat. I would try it if I had a broken one but I hope I never need to.

By the way, anybody know where to buy a suitable terminal welding laser rig for a decent price? Not that I need it, just curious.
all the units I have been looking at are multi process units where the cheapest out of china are about 8k USD shipped to japan. I actually flew over their to inspect a couple fo the offerings about 3 months ago. I was looking at it as a tax write off for my company, but too many other items that I could right off this year that i could actually make money with, so maybe next year.
 
If you are lucky with a pulse setting on your (in my cae Jacis) TIG machine you can find the right spot in your settings and then rinse and repeat.
Laser does the same thing but faster with a much higher impulse power and better targeted but hell yess, I would try this when it happened to me.
Fingers crossed: I need to assemble 20 packs of 4 batteries to create 5 battery strings of 16cells.
my miller welder allows for full control from starting powering to steady state and the same for pulse welding. once again i would want to try on a really furbarred cell before trying on one of these. I just think it would be easy to use an end mill to drill and tap with the size of that terminal I would go with an 10 mm stud though in a medium coarse thread and try to bottom tap just deep enough to get a good 4-5 threads and then baby it while torquing it down. just my thoughts. I do not know about the EVE styles cells, but the calbs out of the factory had 8 x 1.25 threads that were about 6mm deep from the factory. they also had stainless steel helicoil inserts to prevent stripping out as easy. the winstons on the other hand had 14mm threaded holes that go down about 12mm so no concerns with them at all.
 
all the units I have been looking at are multi process units where the cheapest out of china are about 8k USD shipped to japan. I actually flew over their to inspect a couple fo the offerings about 3 months ago. I was looking at it as a tax write off for my company, but too many other items that I could right off this year that i could actually make money with, so maybe next year.
Ouch. I would rather invest in 8k worth of new cells. I could use them all the time instead of just once to fix an $80 cell. Drilling for a stud is a great idea.
 
Ouch. I would rather invest in 8k worth of new cells. I could use them all the time instead of just once to fix an $80 cell. Drilling for a stud is a great idea.
the units i was looking at were a laser rust removal combined with a tig and a laser welder all in one large unit. i am sure there are cheaper ones out there but a plane ticket was only 180 usd and the hotel and food for two days was about 100 eating like a typical pig tourist, so it was worth the flight over to look.
 
the units i was looking at were a laser rust removal combined with a tig and a laser welder all in one large unit. i am sure there are cheaper ones out there but a plane ticket was only 180 usd and the hotel and food for two days was about 100 eating like a typical pig tourist, so it was worth the flight over to look.
Does the laser welding require precise focusing? Like having to maintain an exact distance from the weld? The battery terminal welding videos look like the laser is inches away.
 
Does the laser welding require precise focusing? Like having to maintain an exact distance from the weld? The battery terminal welding videos look like the laser is inches away.
I think there's some kind of laser scanning step prior to the welding step to know precisely where to weld and where.
 
Does the laser welding require precise focusing? Like having to maintain an exact distance from the weld? The battery terminal welding videos look like the laser is inches away.
the one I was looking at the "torch" itself just like the rust stripper portion has mirrors inside the torch head for precise alignment and you could control the whole shebang with a thumb trigger similar to what is on a tig torch. biggest worry I saw was that my friend who bought one of the laser rust strippers "knocked" the torch head and it messed with the alighnment of the mirrors... 1500 to replace about 1200 to ship back and repair and have sent back.... thats kind of why I said no I am too rough on stuff to play with anything that delicate. especially at that price point.
 
I think there's some kind of laser scanning step prior to the welding step to know precisely where to weld and where.
depends uppon if you are using a computer controlled bed or free handing it. this unit came with a 24 x 30 bed space and had the rails and servos installed already or yu could free hand it as well jsut like a tig torch.
 
for production work you would obviously set the bed up to hold the cell in xx,xy location and then measure everything set the whole thing up and hit start and you could repeat it celll after cell after cell. or you could free hand it. for one cell.... yeah i would try freehanding it. just me though
 
"I WARNED YOU ALL! MB31/MB30 huge issue terminal snapping off"
They always ask and I always say - 6mm single stud - works for me.
Maybe we get carried away - oh "we want the double hole larger contact area terminal" - but why ? are you running 300A and need these large termials - that just connect to the same button under it anyway?
 
I put my first 51.2v pack together today (16kwh of MB31's), and guess what? No snapped terminals. Some suggestions on putting the bus bars on:

1) Hand snug all bus bars on
2) Tighten inner 2 bolts on bar first to moderate tightness, then outer ones
3) Torque to spec on inner
4) Torque to spec on outer

My reasoning here is by having all 4 bolts in before applying much force you are making a rigid structure between 2 terminal to resist rotation more. By doing the inner ones first you lessen the rotation force to the other terminal as it's more to the center.

Is it scientific? No, just my gut feelings. I also don't really crank these down. I torque to 4.5Nm which seems like plenty to me.

BTW: Trim that heat-shrink back on these flexible bus bars, it's often encroaching on the terminal surface.


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Some suggestions on putting the bus bars on:

1) Hand snug all bus bars on
2) Tighten inner 2 bolts on bar first to moderate tightness, then outer ones
3) Torque to spec on inner
4) Torque to spec on outer

I think you're quite right that the bus bars could be used to limit the torque (actually the correct mechanical engineering term is moment since this is a statics problem) you're applying to the terminals.

If the busbars are a tight enough fit across the 2 bolts so the cell you're working on can't rotate without the busbar rotating, then if the busbar is held in place the moment you're applying when you torque it's bolts has been countered by lateral forces from the busbars to the bolts themselves, not by the terminal weld.

The trick is how to get the busbar to be a tight enough fit, or if a loose fit how to rotate it counterclockwise and hold it before tightening to take up the bolt hole slack. Not having my battery kits yet I can't answer that.
 
honestly I think a nylon or FRP spanner under the bussbar would give you enough purchase and strength to torque them down safely. just me though once you get all four in and like above snug then tighten I think that coupled with the aforementioned nylon wrench will be fine.
 
OK, I'm screwed. 12 cells in a 3P4S. Putting my last cable on. All the cells nicely connected with bus bars, no issue. Final cable (a big honking 4/0 only 8" long) put a bit of leverage on the terminals, and broke off not only the one it was screwed to, but the bus bar took the next one with it. I'd post a pic, but it's just "a cell with a broken off terminal."

So, I have 2 brand new 314Ah cells with missing terminals. I have read about drilling and tapping, but then my bus bars are all knackered (I guess -- perhaps you bolt the terminal right back on top of the post?).

Welding. I have about zero welding experience, but I have access to TIG and MIG. I suspect that's a non-starter. Also nearby is a really good machine shop (with prices to match!). It it worth taking it to them for their thoughts? Or do I just call 18650 and get two more delivered next week?
 

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