Yes, better. You can compare the thread is to see if it's big enough. I don't think there is enough for full thread.
Cell terminal bolt torque - you might be wrong!
- Thread starter cinergi
- Start date
So the Helicoil has a finer thread pitch than M8? More threads of Helicoil into the aluminum than an M8?
What about forcing in a 1/4” grub screw or using JB Weld?
Hadn’t thought about the increased pull-out strength...
How would you rate an M7 stud?
If repairing a stripped thread with Helicoil, would you replace all terminal threads with Helicoil or only the stripped one(s)?
Thanks for your advice.
Just the pulled one. The helicoil is probably as strong as an m8 or m7 thread
OK, so the overall plan is to use M6 grub screws in the Aluminum threads at 35inch-lbs until you get a stripped thread, at which point you replace with Helicoil to continue using the same M6 grub screw (with stronger retention from the Helicoil).
You’re convincing me..,
Yeah, I think you are right about being unlucky.
Can I assume you are using grub screws? Stainless or plated?
I was originally considering aluminum grub screws for better metals matching, but not after this - I fear I’d end up stripping the threads off of the grub screws and needing to replace them repeatedly... Leaning towards plated grub screws unless someone can point out a drawback versus stainless...
And can I assume the first thing you do with new cells is out grub screws into the terminals? Do you use loctite or some other grease / electrical connection protector?
I’ve got another 8 cells that I have not yet torqued and I’m wondering if fhere is any easy way to check the threads short of torquing a bolt into them at 35inch-lbs.
If that’s really the only practical way to test the strength of the threads, I’m thinking it would be best to go ahead and get the grub screws and whatever treatment is recommended and just install the grub screws ti 35 inch-lbs permanently. If it holds to 35inch-lbs, I’m done and can start using the threaded post from here on out.
And if I have any more weak threads and strip another terminal or two at 35inch-lbs, I’ll just repair them with Helicoil along with the first bit of bad luck.
Really appreciate your advice - I had th out Yahtzee that stripped threads was one risk of DIY LiFePO4 builds that I’d managed to skip, but apparently not...
Don't, if they bottom bad things will happen. You must have a washer or something to keep them from bottoming.
Stainless or plated carbon steel doesn't really matter unless you are in a marine or wet application. I suggest using low strength Loctite and hand threading all of the studs into the terminals. I am using studs which are also known as grub screws or headless bolts. Once The thread locker cures, you can assemble the terminals with your preferred dielectric grease.
Aluminum may also work as well, remember any aluminum fastener you are using will be heat-treated and much stronger than the almost pure low strength aluminum which is used in the terminals.
This one might be the winner. It is a click and skip (no overtorquing). Range is 0.5 Nm to 4.5 Nm. You have
I wouldn't trust that bicycle torque wrench. I got a huge difference from 1/4" click torque wrench. I don't trust either of them, but the bicycle wrench way under-reported the torque compared to the click torque wrench.
Yes, I always thread bolts into terminals with a busbar in place... (I’m a newbie but not thst
Perfect, thanks. Low-strength Loctite and dielectric grease it is (the latter of which I have never used - what is your preferred brand/product?).
I may end up sealing my cells in a temperature controlled box, but otherwise they will be exposed to the air in my unfinished basement area with dirt floor which gets moist over winter. Not a marine environment but enough moister than indoors or the finished basement that the extra precaution of going with zinc panting seems prudent, especially if there are no downsides.
I did not realize that (have never used aluminum threaded fasteners). So perhaps I’ll go that route. I know zinc-plated M4 grub screws are easily available and relatively low-cost, so I’ll check what I can find in aluminum...
Meaning that when my new torque wrench reported 35inch-lbs, I may have actually been over that...
The variability from pass to pass is difficult to objectively assess but I guess I should apply a calibrated 35inch-lbs and see what it reads (wish it had occurred to me to do that calibration before I built my 8S battery...).
I like heavy body greases, almost a paste at room temp. This stuff is good. Really any product will work fine here.
Thanks. And what are you using to calibrate the torque you are applying?
On a related note, how does one measure torque when tightening a nut onto a set screw that has to be held with an Allen head wrench?
All of my torque wrenches are socket-type...
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,535
"Prime Preset Torque Screwdrivers"
Meaning tell the factory what torque value you want?
I didn't see mention of adjustment (at first).
I'd want something for a variety of circuit breaker setscrews.
I found this on setting them, takes a fancy torque gauge:
I am going into work tomorrow with all of my torque wrenches and testing them against standards.
One thing is to let you learn what the right torque feels like.
I thing a screw driver with the right bit might be best. Something that requires you to work hard to apply a lot of torque.
Oddly enough, I was thinking about that very problem this morning. The simple answer is that there is no way to verify the torque in that situation unless you're using a crowfoot adapter on the torque wrench. The issue with that is you have to adjust the torque setting to take into account the offset length of the crowfoot adapter.
For those not familiar with a crowfoot adapter, here is a picture. The adapters I have are much shorter that in the picture, but I don't have any metric size ones.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,535
Oddly enough, I was thinking about that very problem this morning. The simple answer is that there is no way to verify the torque in that situation unless you're using a crowfoot adapter on the torque wrench. The issue with that is you have to adjust the torque setting to take into account the offset length of the crowfoot adapter.
For those not familiar with a crowfoot adapter, here is a picture. The adapters I have are much shorter that in the picture, but I don't have any metric size ones.
What if you attach the (short) crowsfoot at right angles to the torque wrench?
Similar threads
