Stripped threads on aluminum cell

[FilterGuy]

HELP!!!
My brother-in-law striped the threads on the terminal of an aluminum case cell. I have heard others say they had the same problem and used Helicoil inserts to fix the problem. However, even with a bottoming tap he was not able to do the oversized thread deep enough for the helicoil because of the taper on the end of the tap.

How have others dealt with this?

 

[Ped]

Grind the tap down

 

[FilterGuy]

On a grinding stone wheel?

 

[Craig]

this is so funny I had the same problem with a different situation though yesterday. I just found a shorter bolt which in my situation worked fine. How far in the old hole can you get with the tap?

 

[ghostwriter66]

How far in the old hole can you get with the tap?

No matter how many times I read this - it just sounds WRONG ...

 

[Craig]

No matter how many times I read this - it just sounds WRONG ...

When I wrote it I was trying to figure out how to put it differently but couldnt.

 

[FilterGuy]

this is so funny I had the same problem with a different situation though yesterday. I just found a shorter bolt which in my situation worked fine. How far in the old hole can you get with the tap?

Unfortunately, he is in WA and I am in CA.... He said he almost got deep enough with the bottoming tap... But I am not sure what that means to him.
I found an STI tap that has a very short taper and will try that. If it does not work I will grind it down some and try again.

The problem is that there are very few threads in those Cell terminal holes to start with. :-(

 

[onemorebattery]

For stripped posts an alternative to tap/helicoil is get the next size up set screw and a self tapping screw to cut the threads.

https://www.amazon.com/4-20-Floorboard-Thread-Cutting-Screws/dp/B07D3P3QK8/

http://www.amazon.com/Stainless-Screw-Screws-Bolt-Dropper/dp/B07D1L6RRD/

For batteries that haven't been stripped out yet these M6 screws will get you maximum threads and you can use an allen wrench when tightening to avoid stripping.

M6 Stainless Steel Set Screws with Cup Point, Socket (Allen key) Drive, DIN 916 | eBay

Specifications:DIN 916 / ISO 4029. Matching Nut & Washers: M6 - Available here. M6-1.0 Socket Set / Grub Screws with a Cup Point. These are made from A2 / 18-8 Stainless Steel. Thread Size:1.0 - UNC / Coarse (Standard) Thread.

www.ebay.com

 

[Ped]

On a grinding stone wheel?

Sure. Or a cutoff wheel. Take the tapper off.

Shouldnt have tried a helicoil though. Just go a size up with same thread pitch. Often just cutting a new thread of same diameter will fix it. I did with mine. Always try that first especially with battery posts. Can always dab loctite if its questionable. And or use a stud and nut.

 

[keepsake]

On my 280ah they use M6 threading. The first gen of cells came with threaded holes. This second gen came with welded in studs. I find tightening a nut onto a stud to be 10 times better than tightening a bolt into the threaded hole. Anyone else done anything else. Is there enough aluminum to make it a M7 threaded hole ? Or will that weaken the terminal ?

 

[FilterGuy]

I have rethreaded terminal pads to M8.... but would not do it again if I had to.

How to drill and tap aluminum cell terminal to modify from M6 to M8 threads

To get this paper, click on the orange button at the top of the page I stripped out the M6 threads in the terminal hole of an Aluminum Case LiFePO4 Cell. This deck shows what I did to drill out the hole and tap for an M8 hole. Revision 2...

diysolarforum.com

Every time you screw the stainless steel stud in or out, it damages the soft aluminum threads. My advice to people with threaded terminals is to put studs in with some red locktite and primer and never take them out again. (use a minimum length of 20mm on the stud. 25mm is better.

 

[keepsake]

As I said elsewhere docan power is welding studs in many of the 280ah they ship. That is the ticket. Get it.

 

[SparkyJJO]

I'm nervous now, my 230s came with threaded holes and I have a habit of cranking on things....

 

[time2roll]

I'm nervous now, my 230s came with threaded holes and I have a habit of cranking on things....

Need a small torque wrench. Mine are at 3nm or 25in-lbs and holding fine.

I use this:
Presa 1/4-in Drive Beam Torque Wrench

 

[keepsake]

I had the threads sized M6 stripped in my 280ah Eve cell bought Jan 2021. I got a tap for M7. Wouldn't you know it I don't have an M7 bolt.
So after placing busbar on terminal, I carefully threaded in a double-nutted 1/4" bolt. It took and I have no intention of removing ever again. Rather tight now. Just using one of the double nuts to tighten down the busbar. Viola! Back up and good to go.

 

[SparkyJJO]

M7 strikes me as a weird size. Seems most things commonly go even numbers after m6.

 

[time2roll]

Local Ace Hardware had some M7 last I looked. limited selection. Same 1mm pitch.

 

[FilterGuy]

M7 strikes me as a weird size.

M7 is unusual (at least here in the states), but it is certainly available.

 

[timselectric]

M7, seems to be popular for cells.

 

[FilterGuy]

M7, seems to be popular for cells.

Interesting..... I have not purchased individual cells in almost a year, but way back then they were almost all M6. I would have appreciated having M7.

 

[timselectric]

I suspect, that it will progress to m8.
Everything improves over time.

 

[FilterGuy]

Actually, the new 'norm' is welded M6 Studs.

 

[timselectric]

True

 

[Warpspeed]

Threaded holes in aluminium seem to cause grief sooner or later.

The "correct" engineering solution is to fit some threaded studs, the very first thing you do.
Put them in finger tight + 1/4 turn, and if you use proper thread locking compound, they are in there pretty firmly, but are still removable.

Then use a plain nut with a washer, and you can heave down on that nut, screw and unscrew it a thousand times, and you will never have any trouble. The chances of cross threading a nut are just about zero. And if you do wreck the stud, a new one is a quick simple fix.

 

[time2roll]

Threaded holes in aluminium seem to cause grief sooner or later.

The "correct" engineering solution is to fit some threaded studs, the very first thing you do.
Put them in finger tight + 1/4 turn, and if you use proper thread locking compound, they are in there pretty firmly, but are still removable.

Then use a plain nut with a washer, and you can heave down on that nut, screw and unscrew it a thousand times, and you will never have any trouble. The chances of cross threading a nut are just about zero. And if you do wreck the stud, a new one is a quick simple fix.

I read this as a stud threaded into the aluminum threads and 'heave down' on the nut. I see the aluminum treads pulling right out.

I would stick to 3nm or 25 in-lbs for that heave.