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Broken welded stud

Search for “easy out” basically reverse threaded drill bit and a grabber bit.

My fear is that of the stud is “locked”, damage may have already been done to the cell terminal threads.
 
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?
I presume you will buy and use a torque gauge from now on?
 
@neil_99 - Sorry, but I take back everything I said about backing that stud out. I was reading another thread on terminals and studs and found out that the welded studs are stainless bolts clad in aluminum at the base and welded onto the battery terminal. I don't think that stud is going to come out without a fight.

I would take it to a machinist to center drill and then drill to size and tap. I would not drill any deeper than the wide aluminum face of the terminal below the weld. Here is a photo I found in the other thread showing a stainless stud and its welded aluminum wrap.

If you are near Northwest Florida, I'll drill it for you.

lishen-272ah-with-m6-stud-jpg.60158
 
I haven’t ever had to extract a broken stud on a battery before but I have done my share of broken studs into aluminum of many sorts. If you want to try removing the stud find a socket that will allow you to guide and hold the drill bit at the center of the broken stud. You must drill only into the std material. Make sure that the bit is short enough or has spacers on it so that you can’t drill to deep. They sell square shaped easy outs that have some effectiveness in a shallow hole.
Use proper safety equipment goggles gloves ect. There is a risk involved so protect yourself same reason you should wear your seatbelt if you go into town to get another cell.
 
@neil_99 - Sorry, but I take back everything I said about backing that stud out. I was reading another thread on terminals and studs and found out that the welded studs are stainless bolts clad in aluminum at the base and welded onto the battery terminal. I don't think that stud is going to come out without a fight.

I would take it to a machinist to center drill and then drill to size and tap. I would not drill any deeper than the wide aluminum face of the terminal below the weld. Here is a photo I found in the other thread showing a stainless stud and its welded aluminum wrap.

If you are near Northwest Florida, I'll drill it for you.

lishen-272ah-with-m6-stud-jpg.60158
Thanks for the offer, but I'm in the Houston area.
 
Too short for a welded nut. Do as you like and be safe about it. In the mean time I would get a new cell on its way.

And by golly get a torque wrench. https://www.lowes.com/pd/Presa-1-4-in-Drive-Beam-Torque-Wrench

About 3 Nm or 25 in-lbs
I actually have a torque wrench, I was just ignoring what it was telling me because it didn't feel like the nut was near the bottom of the post. I didn't really feel like I was putting much force on it when it broke, but it had clicked. Expensive learning opportunity.
 
If you go to Docan, I’d be interested if they have these in stock. They are saying 2 months for male terminal EVE 280k
 
I actually have a torque wrench, I was just ignoring what it was telling me because it didn't feel like the nut was near the bottom of the post. I didn't really feel like I was putting much force on it when it broke, but it had clicked. Expensive learning opportunity.
Stainless bolts with stainless nut don’t get along well, then throw in China QC and well you have a problem. I never use stainless with out a drop of oil. I have had them get a little snug and reversed and broke while backing up.
 
I took it to a local machine shop. They got the threaded rod out and retapped a few threads inside the hole. I've attached a few pictures for reference.
 

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I took it to a local machine shop. They got the threaded rod out and retapped a few threads inside the hole. I've attached a few pictures for reference.
Be careful when trying to torque that. There's fewer threads than they normally come with and what they normally come with is easy to strip already.
 
Stainless bolts with stainless nut don’t get along well, then throw in China QC and well you have a problem. I never use stainless with out a drop of oil. I have had them get a little snug and reversed and broke while backing up.
This is literally the worst, I have broken spanners, and ended up having to cut several stainless bolts that did this to me (not on batteries), they seize insanely easily without some lubricant.
 
Out of curiosity - why the nut should be stainless steel? There is no contact between the nut and the aluminum terminal. So there should be no impact on the cell terminal related to the nut.

Regarding the seizing - do oxidized stainless steel nuts seize too?

Regarding the retapped cell terminal - what is the insertion depth of the stud? From the pictures, I can see 2 and a half turns and this would be 2.5mm if I'm correct. This won't hold sufficient torque. Especially with the quality of the retapped thread.

If it was me I would redrill for M8 stud and use fine pitch M8 stud. Proper thread locking glue (permanent) would also add some strength there. Or check what suitable welding options (spot, laser) you have around you.

And why not contact Eve directly for advice regarding the max drill depth? I know some folks here got information regarding the cell compression they recommended directly from their engineers. So it should be possible.
 
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