Broken welded stud

[neil_99]

So, I used too much torque on one of my welded studs on my Eve batteries. It broke off near the bottom. I've attached a picture. How do I fix this? Do I drill out the stud and tap a new larger thread in the terminal? I don't have much experience tapping threads. Would I be better off just buying another cell?

 

[SparkyJJO]

Wow. I guess we know they did a good job welding that stud on there!

I have no idea how to recover from that. I'd be scared of trying to drill it out. My lick the bit would slip off and punch a hole where things ought not be drilled.

 

[TomC4306]

It looks like you broke the bolt.
Holy Crap!
I think you should replace the cell and before it arrives buy a darn torque wrench!

 

[RCinFLA]

From picture it doesn't look like the weld failed. It almost appears the threaded stud was a separate piece screwed into welded on female threaded bushing which failed. If separate threaded post, maybe it bottomed out causing a high vertical pulling force cracking perimeter of the threaded bushing.

Short of getting a new welding job, which I don't recommend, your only option is to try and drill and tap a hole.

The internal cell pouches are not sealed. They are open at top of pouch. This means you do not want to breach the aluminum outer container, including drilling too far through terminal.

If you do break through at bottom of hole, at least put some sealant at bottom of hole before screwing in threaded post. Don't leave breach open to air too long.

Good luck.

 

[justgary]

I agree that it looks like the stud is not welded. Did you try to back it out? You can use a sharp punch and small hammer to try to get it to move. I have seen plenty of broken studs that will just back out by using pressure and turning with my thumb. Of course, they could have used thread lock compound on it even if it isn't welded.

If it absolutely will not back out, then try to drill.

 

[circus]

If it's a stud a magnet should stick to it. If yes removal shouldn't be difficult, at least for me.

 

[neil_99]

I agree that it looks like the stud is not welded. Did you try to back it out? You can use a sharp punch and small hammer to try to get it to move. I have seen plenty of broken studs that will just back out by using pressure and turning with my thumb. Of course, they could have used thread lock compound on it even if it isn't welded.

If it absolutely will not back out, then try to drill.

Not yet. I'll try that.

 

[brum]

Try to cut a slot or center drill the stud that is in the battery terminal. Then use either a flat screwdriver or bolt extractor. With some luck, the stud will go out.

Check what is the remaining thread depth and if sufficient - try to go with another screw. If the remaining tread depth is 1-2-3mm you most likely would have to change the cell. I would try spot welding to attach a suitable connection, but I'm almost sure this will provide higher resistance than a bolted boot with the proper torque.

 

[LithiumSolar]

Holy crap! I've always been paranoid overtightening these bolts because I was afraid of the stud twisting and messing up the internals. You actually tightened it so much that the bolt snapped off instead of damaging the actual terminal. Personally, I wouldn't try to repair it - not worth the risk unfortunately. (edit: Oh I see the stud looks like it's not welded, hmmm)

 

[time2roll]

Looks like a welded nut on top of the terminal to me. Need a side profile pic.
Possibly a reverse drill would back out the stud while drilling a hole to use an extractor.

When that fails.... time for a new cell.

 

[42OhmsPA]

Looks like a welded nut on top of the terminal to me. Need a side profile pic.
Possibly a reverse drill would back out the stud while drilling a hole to use an extractor.

When that fails.... time for a new cell.

Reverse drill and easy outs / extractors were my first thought as well.
I became great friends with them building a GTI many years ago; learned lots about extreme heat, vibration and proper fasteners...

OP if you attempt to drill make sure you are centered, use a punch, go slow and steady. If you end needing to re tap it or chase the threads you'll want a flat bottom tap.

 

[circus]

Drill & tap is hazardous. If the stud is steel and the aluminum is....aluminum, forget it. If the stud is steel your best bet is to skillfully weld a bolt on off center and turn it out.

 

[XO4001]

I had a similar experience only mine broke by the weld (because of a bad weld that I had to clean up and make it even weaker than it was)
I filed the terminal flat as possible and drilled in the center wit a 5mm bit and 6mm deep and took a tap that I grinded flat so I start with full thread what was very easy because the material is very soft and tapped till the bottom very carefully twice, inserted a stud with Loctite and torqued carefully.
Maybe its an option to take the whole weld down and start fresh in the terminal itself and don't bother to take that broken piece whatever it is out.
Good luck.

 

[neil_99]

Here is a side view. The stud is not loose. I have tried grabbing it with plyers and turning counter clockwise and there was no movement.

 

[circus]

I suspect it's not a stud. Is it ferrous? Magnet sticks to it.

 

[upnorthandpersonal]

Personally, I would drill it out and re-tap or what @circus suggested in #12. That said, don't do it if you don't have experience doing it. Take it as a loss and buy a new cell, and a torque wrench.

 

[neil_99]

I suspect it's not a stud. Is it ferrous? Magnet sticks to it.

Magnet does stick to it.

 

[Bluedog225]

I would, with eye protection and outdoors, take a small diameter dremel cut off wheel and cut a slot in the stud. You will cut the base a bit. Then put a few drops of acetone mixed with automatic transmission fluid in the threads. The absolute best lubricant for this purpose. Let it soak overnight. Then try to turn it out with a flat screwdriver.

You can get a very small diameter cut off wheel by wearing down a regular dremel wheel on a piece of something. Careful, they fragment. Eye protection.

Good luck.

 

[neil_99]

I would, with eye protection and outdoors, take a small diameter dremel cut off wheel and cut a slot in the stud. You will cut the base a bit. Then put a few drops of acetone mixed with automatic transmission fluid in the threads. The absolute best lubricant for this purpose. Let it soak overnight. Then try to turn it out with a flat screwdriver.

You can get a very small diameter cut off wheel by wearing down a regular dremel wheel on a piece of something. Careful, they fragment. Eye protection.

Good luck.

I notice you are in Texas. What area are you in? I'm in the Houston area.

 

[LithiumSolar]

Why not just grab a new cell instead of worrying about drilling, tapping, welding, or otherwise trying to remove it that could result in fire?