NIPPLE slip

ghostwriter66

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So some of my batteries have decided to loose their TOPS it seems ... some of the batteries i got a while back from a supplier I no longer use, is starting to have the tops of the batteries pop off ... looks like they may have used some form of arc-welding or spot welding to zap the terminals in place but they are obviously not holding ...

I would rather not try to drill my own terminals holes so does anyone have an idea of either how I can reattach these tops -- OR do you have a better plan ... I may be wrong but it looks like its aluminum on aluminum .... aaaggghhhh


erd44.jpg
 

digitalsteve

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Was about to report this post, you probably should change the title.
I had a similar situation and could not find anyone that does laser welding who would be willing to weld on my Lifepo4 cells. All were afraid. I ended up drilling into the top, first with a small drill. Only an 1/8" deep at first, then in 1/8 inch increments. In my batteries (different than yours) the aluminum changed to copper about 3/16" deep, then I continued into the copper with the 1/8 steps until I reached about 1/2 inch or so. I did not want to drill into the lithium cell. I then drilled with a larger bit to the diameter for my tap. Tap threaded the hole and used a stainless steel screw. In your case you might drill 3 or 4 small holes, on an angle and use small screws to attach the top. It might be good for 30 or 40 amps. Put a load on it and check for heat.
 

Rednecktek

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Hey now, cover that terminal! This is a FAMILY FRIENDLY forum!! :)

Otherwise, I seem to remember from my PC days that there are some thermal adhesives that are electrically conductive, if you can find some of that you might be able to "glue" the terminal back on.

Otherwise, as @digitalsteve said, drill and tap really, really slowly.
 

jasonhc73

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A - Solder it in place. Probably will work perfectly fine.
B - Find a professional welder. Probably the best option if you can find an experienced aluminum welder.

My guess is that these were friction welded in the first place.
 

DJSmiley

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*following*

I have the same issue on one of my 230Ah cells (from Basen): Welded terminal came off. It was probably a bad weld or so, since it almost came loose instantly when connecting a wire. I think it was only 2nm or so, it was while mounting the cable and intitial locking of it, even before the final torque
(I usually connect it manually and tighten it only a little with a regular spanner, finishing it with a torque wrench)
 

Rednecktek

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Now I remember! Call around to your local jewelers. Many of them do laser welding on very small things and their equipment might be able to laser weld those back together without risking pumping too much heat into the terminals and melting things inside.
 

kenryan

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Welding seems like a bad idea to me (but I will readily admit I know little about battery terminal technology).

The reason it seems like a bad idea is because it looks to me like the entire surface area of the blown top is meant to be in close contact with the battery cap.

If you weld it, there will only be a small ring around the perimeter where the top and the cap are closely connected, and that might not provide sufficient electrical connection.

My vote would be for an appropriate electrically conductive adhesive, provided such a thing exists.

Given the catastrophic results that are documented on Youtube with regards to penetration of LiFePO cells, drilling threads would be my LAST option.

Disclaimer: these are the thoughts of a non-battery expert.
 

AndyRonLI

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So does anyone have access to a construction drawing of one of these?
That should tell you how the internal anode/cathode relate to the terminal. The post from digitalsteve seems to indicate that you could drill and tap, but it would be good to KNOW whats in there.
X-Ray?
 

stienman

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Regarding some suggestions:

Soldering won't work with aluminum. (brazing would, but it would also require a ton of heat over the entire area)
Welding with a TIG machine in very short bursts with a wet rag between should be fine.
Please don't use an adhesive/epoxy/etc even if it's conductive. Not only is the resistance poor, but almost every conductive compound is very brittle, and placed between those two pieces of aluminum you'd eventually crack and detach.
Laser welding would require a good deal of setup, and you might not get any better penetration than the original supplier got. If you had them re-do the entire bank, maybe it would make sense, but having them do one terminal will probably cost more than simply buying a new battery.

If you cannot get a mechanical drawing of the terminals to determine how much drilling they can accept, I suggest drilling four smaller holes - maybe M4 or M3 - to a depth of 6mm and bottom tap them to 5mm. Then modify the bus bar to accept the four screws, using screws that will extend into the holes the full 5mm. That'll handle all the current that you'd need. Taps and drills are cheap, compared to all the other solutions.

But the real issue is that the weld quality is very poor(insufficient penetration), and if they other terminals are like that, you may want to speak with the supplier and indicate they did a lousy job. Send the same pics, and show that the remaining weld marks on the battery clearly show the weld didn't go deep enough. Ask them to pay for a local place to rework them - all of them. This won't be the only cell that this happens to while you're working with them, I bet.
 

GXMnow

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I have a pretty good guess as to what caused it to come off. The top piece appears to have the threaded hole go completely through. So I will bet, the screw turned and pushed out the bottom against the cell terminal and tore the factory laser weld. If you have cells like this, you need to be very careful to not use screws that are too long, and even if using studs and nuts, to be sure the stud does not turn and push out the bottom. This is not a good design. Of course, this does not help the OP on a fix, but hopefully it helps prevent others from suffering this type of failure.

As to a way to fix it.... that is a tougher question. How much current do you plan to charge and discharge on this cell? If it was mine... I would probably drill it only 1/4 inch deep with a 7/64th inch bit and tap it for a 6-32 stud. (3 mm for the metric folks). 1/4 inch deep should give a solid 4 threads. That should hold enough tension to clamp a buss bar on for a 50 amp connection. Drilling into the terminal is risky, but a small hole only 1/4 inch in should be safe. I would have two half full 5 gallon buckets of sand nearby. If it starts leaking, gets hot, or anything, drop it on one bucket, and pour the other over it.

I have tried using "Aluma Weld" type products to "solder" aluminum, and I did get it to work to fix the upper blade guide of my bandsaw, but it was tough to work with, and you still need to get the surface heated to 400F (205C) for it to stick. I think that is too risky for the cell.
 

ghostwriter66

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It is a very misleading title, either way. kind of click bait.
Of course its CLICK-BAIT -- but somehow it seemed to have worked and I got my question pretty much answered .... and actually going to say no matter what you call the thing on top (I heard the guys in the shop call them a dozen things yesterday - 11 of them pretty sure wasn't even remotely correct but they all sounded like body parts) -- so not even really sure what to call it technically -- but whatever it is .. IT SLIPPED .... :)
 

fafrd

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*following*

I have the same issue on one of my 230Ah cells (from Basen): Welded terminal came off. It was probably a bad weld or so, since it almost came loose instantly when connecting a wire. I think it was only 2nm or so, it was while mounting the cable and intitial locking of it, even before the final torque
(I usually connect it manually and tighten it only a little with a regular spanner, finishing it with a torque wrench)
I have no experience with these new welded terminals, but if they can come off so easily, I’d be worried about the contact resistance even for those terminals that have stayed in place. I think you have to assume that the aluminum-on-aluminum area in the middle is oxidized and represents poor conductivity per mm^2, so it is only the cross-section of the weld itself that represents a reliable high-conductance path for current - has anyone characterized the conductance of these welded terminals under load? (ie: use probes to measure voltage between terminal surface and battery terminal below when 50 or 100A of current are being driven)

Here is a picture of the weld from a BYD battery which shows how these aluminum terminals were intended to be welded:

D1E8AE0F-ABD1-4791-A6C9-F3966341B4B2.jpeg

263AFDD3-C182-4155-800A-71059B90A637.jpeg
 

fafrd

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I have a pretty good guess as to what caused it to come off. The top piece appears to have the threaded hole go completely through. So I will bet, the screw turned and pushed out the bottom against the cell terminal and tore the factory laser weld. If you have cells like this, you need to be very careful to not use screws that are too long, and even if using studs and nuts, to be sure the stud does not turn and push out the bottom. This is not a good design. Of course, this does not help the OP on a fix, but hopefully it helps prevent others from suffering this type of failure.

As to a way to fix it.... that is a tougher question. How much current do you plan to charge and discharge on this cell? If it was mine... I would probably drill it only 1/4 inch deep with a 7/64th inch bit and tap it for a 6-32 stud. (3 mm for the metric folks). 1/4 inch deep should give a solid 4 threads. That should hold enough tension to clamp a buss bar on for a 50 amp connection. Drilling into the terminal is risky, but a small hole only 1/4 inch in should be safe. I would have two half full 5 gallon buckets of sand nearby. If it starts leaking, gets hot, or anything, drop it on one bucket, and pour the other over it.

I have tried using "Aluma Weld" type products to "solder" aluminum, and I did get it to work to fix the upper blade guide of my bandsaw, but it was tough to work with, and you still need to get the surface heated to 400F (205C) for it to stick. I think that is too risky for the cell.
When these cells with ‘welded’ studs first came out, I was kind of jealous and wished I had held off another 6 months before purchasing my cells.

After these reports, I’m feeling lucky.

The cells with tapped threads are a PITA. They are exceedingly fragile, strip super-easily, and are easily mud-tapped (either tapped too shallow or tapped off-square).

But at least once you get a stainless grubscrew locked into enough aluminum threads, you’ve got the ability to form a reliable connection with a lug or busbar.

And having tapped my own threads into 5 terminals, it’s manageable with the right tools.

I even salvaged a severely stripped terminal by filling the hole with JB Weld, allowing it to fully, fully cure, tapping the cured JB Weld, and then successfully JB Welding a grubscrew into those newly-tapped threads. That terminal takes as much torque as any of my unstripped aluminum terminals.

Again, a huge PITA but at least a reliable connection once you’ve got a grubscrew in place.

These welded connections, if they are not properly done, seem like a much greater reliability concern and potential safety hazard.

These resellers are just looking for ways to provide terminal threads without any guidance or specifications from the cell manufacturer.

BYD clearly knows what they are doing because they use these cells in EVs and battery packs but their welded connections are very different from the welds being delivered by resellers:

D208ACA4-C054-4B61-919C-AF9FEB729255.jpeg

40F08C63-101D-436E-A9E7-2E38562B7109.jpeg

I’d have no concern with welded connections that completely surrounded the outer 1-2mm circumference of the terminal but it sounds like the welds you guys are getting are well below this.

EVE has apparently started supplying cells with welded terminals, but they look very different than the welded studs that many resellers are offering:

D1A1358F-C8EE-45B1-BDC8-D5B27CBC32DE.png

Those appear to be thick aluminum ‘posts’ with a large ‘doughnut’ where the post is welded onto the aluminum terminal surface.

That looks like a design ready for prime time and any new cells I purchase will be of that type (regardless of price premium).

So my advice is that if you are going to attempt to get your own welded connections: stick to aluminum-on-aluminum with a thick-enough doughnut weld (either around the outside edge of the cell terminal or a suitably large circumference within the terminal surface) to both provide sufficient mechanical strength as well as to provide sufficiently-large weld-area-only conductance.

This is what both EVE and BYD are doing and these are the manufacturers that know what connections these cells were designed to support.

The welded stainless studs on aluminum terminals design was arrived at by resellers who have little to no idea what they are doing and I now view them as even more dangerous than the lousy threaded terminals (possibility of low-conductance connections and/or failing connections during use).

As far as ways to salvage cells that have poorly-welded studs or no tapped threads, either a proper aluminum-on-aluminum weld job as I’ve outlined above or a properly-tapped M6 thread would be my suggestion (followed by a properly Loctited stainless grubscrew).
 
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Short_Shot

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You were you going to report it , then read the thread ?
Why are people so quick to be tattle tale PC . We are getting so soft and squishy it's not funny.
"Someone on the internet hurt my feelings!"
 

fafrd

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I have a pretty good guess as to what caused it to come off. The top piece appears to have the threaded hole go completely through. So I will bet, the screw turned and pushed out the bottom against the cell terminal and tore the factory laser weld.
I think this is correct. If the weld appears to be well-done and conductance is good, I’d suggest to get grubscrews locked into these welded terminals ASAP.

Can’t tell whether the threaded terminal material is stainless or aluminum, but either way, getting a grubscrew locked into it (without applying too much torque, as you suggest) seems like the best way to avoid forcing the welded terminal to pop off (or rather, forcing the welded nipple to slip ;))…

If you have cells like this, you need to be very careful to not use screws that are too long, and even if using studs and nuts, to be sure the stud does not turn and push out the bottom. This is not a good design. Of course, this does not help the OP on a fix, but hopefully it helps prevent others from suffering this type of failure.
Again, my suggestion would be to secure a stainless grubscrew into the threads…
As to a way to fix it.... that is a tougher question. How much current do you plan to charge and discharge on this cell? If it was mine... I would probably drill it only 1/4 inch deep with a 7/64th inch bit and tap it for a 6-32 stud. (3 mm for the metric folks). 1/4 inch deep should give a solid 4 threads. That should hold enough tension to clamp a buss bar on for a 50 amp connection. Drilling into the terminal is risky, but a small hole only 1/4 inch in should be safe. I would have two half full 5 gallon buckets of sand nearby. If it starts leaking, gets hot, or anything, drop it on one bucket, and pour the other over it.
I’ve drilled a total of 7mm down without issue (by hand, slowly, carefully).

One of the two terminals is copper. Start with that one and you will see a very small dot of copper form in the center once you have bottomed (if you go past 7mm).

Do the copper terminal first so you have a reference for the all-aluminum terminal (and to be safe, back off ~1/2mm).

Drilling straight is a big part of the challenge but with a properly-sized jig and using a tap handle, you can get it done 1/4 turn at a time.
I have tried using "Aluma Weld" type products to "solder" aluminum, and I did get it to work to fix the upper blade guide of my bandsaw, but it was tough to work with, and you still need to get the surface heated to 400F (205C) for it to stick. I think that is too risky for the cell.
I think the risk of a failing connection is far too catastrophic to experiment with unproven materials / techniques.

Complete circular aluminum-on-aluminum welding is the proven connection technique for these cells (and the connection technique for which they have been designed).

Tapped threads is honestly pretty Mickey Mouse but at this stage, is relatively proven if approached in the right manner (locking in stainless grubscrews with Loctite Red and using a calibrated torque wrench to tighten nuts with sufficient but not too much torque).
 

time2roll

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Did it really just pop off on its own? Seem like with the threads going through the nut it would be easy to bottom out and lift the nut off.
My only thought would be to use conductive epoxy.
 
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