Update !!!
Time enough (since June 26) for the epoxies to harden, and even Loctite without primer...
I already gave the "spoiler" with Loctite without primer...
It sure does help a little, absolutely not what it can be, for strong bonding.
I don't feel like pulling +10Nm on a good contact, to pull out the thread/grubscrew with good Loctite contact, but perhaps I have a bad cell that can be sacrificed.
The removed threads that where normally in need for helicoil upsize (M7 thread), that I tried to fix with the several epoxies.
On M6, all failed. :-(
After 3.5 Nm, I can feel them letting go.
I didn't twist the same after releasing, some you can see threads inside, chunks, or total smooth released.(Marine)
JB Weld
JB Marine Weld
Devcon plastic steel epoxy
Loctite thread repair
JB Marine Weld is the strongest bond, the other 2 are the same.
One release at 3.8Nm, one is still in use, @4.3Nm no problems.
For the quick hardening Loctite thread repair, released at 3.8Nm.
Impressive, compared to the other 3, who need +24 hours to harden and this is supposed to be fully hardened in 30 minutes..
For many setups, 3.8Nm is sufficient.
3.5Nm also might be doable, especially with a smaller bus-bar, who will have more pressure on the available surface.
I use Bus-bars that fully cover the the whole terminal, more contact area, also more torque needed to get the same clamping force per mm2.
On M8, Loctite thread repair holds perfect, even @5.0Nm
The threads that where damaged, I've shown several pictures, where some thread is still available, not enough to hold the +4Nm Torque I like to give, as I could feel them slide, and max 3.2Nm..
You will know when you have one...
Don't keep applying torque, and pull out the whole thread!!
(I never did, still had a few totally smooth M6 walls)
With a bit of luck, unscrew the stud.
Remove lost aluminium chunks or spiral.
And apply epoxy!!!
All my 4 available USA epoxies held up great!
Again, I don't feel the urge to keep applying more force to see when they release, 4.2Nm still feels solid.
Perhaps I have a bad cell that can be sacrificed... For now...
Not with M6.
M8 is "different".
Not only is the stud bigger, it has different thread, 1.25mm per turn Vs 1mm for M6.
Where M6 has some "sponge" area, torque builds up more slowly, M8 suddenly "hits bottom" and often is on 5Nm Torque without effort.
I didn't have a Torquemeter when I started.
It might be healthy clean, fresh and quality M6 threads have no "sponge" feeling when tighting.
To long ago, I don't remember.
I can tell that if you mount and re-mount several times, it will get some "sponge" area, about 1, 1.5 turn before you really see/ notice increase in Torque.
Some people might say that M8 is bad, as you lose quite some aluminium and copper contact surface.
Thrust me when I tell you, it's more then enough!
Standard bus-bar from China cover only partly the terminal.
Bus-bar for M8 cover just as much, perhaps more.
Besides this, you can apply more torque, 4.5-5Nm without issues.
I even dare to say that M8 will have better contact then M6.
M6 grubscrew and standard 2mm Bus-bar
My home made M6/M8 bus-bar (4.5mm thick)
(I also use for M6, with 6.5mm hole)
250A is not a problem
Should be able to withstand over 500A, a load I will never get.
I oversized to reduce heat, at extreme high loads.
While Loctite (with primer) doesn't reduce in strength up to +200c,
Most epoxies start to get soft at +60c, 150F
60c isn't a lot
And the epoxy is the trick that keeps many Bus-bars clamped tight with +4Nm torque.
In other words, there is a constant pulling force on the epoxy.
Getting it soft is BAD!!
So..
Why epoxy at all?? Why not all helicoil??
Mostly as the work needed for helicoil, the risk that it goes wrong, upsize to M8.....
If I can avoid, great!!
I have 32 cells doing now all the work, several with cheap Thai epoxy, that for some lucky reason does stick strong enough.
After several months, all contacts are still OK.
They don't get warm
.
(Good contact, large enough Bus-bars)
Thailand (our area) reach 44c on regular basis, 47x is the max I've seen.
That's a small temperature difference to +60c....
Luckily, I have them in a special fire "proof" closet, with automatic human safe fire distinguisher, in our bedroom, and they are cooled with the airconditioning from the bedroom.
Temperatures stay below 40c.
My BMS (DIYBMS V4) has 2 temperature sensors per cell module, one for the module (dumpload) and one for the cell.
I have 2 different versions,
4.2 and 4.4.
1.2 and 1.5A dumpload per cell module
WiFi, database integration and much more goodies.
That all folks.
If I have defective cells to test M6 Loctite with primer, I'll update!!