If using Loctite then yes. Put some on a paper towel...it will never cure. Keep in mind many of us have used Loctite and had no issues. Regarding trapped air I unscrewed my studs about a turn then screwed it in then backed off a bit. I don't know if that helped. When using JB Weld to repair threads, I would just screw the stud in and let it set.
JB Weld versus Loctite for grubscrews
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ArthurEld
Solar Wizard
My concern about the studs perpendicularity is mostly for the studs that are really loose.
The rest of my cells are new so the threads should be good enough
I would be looking for the stuff that has the highest tensile strength. When I was researching, I couldn't find anything that has a higher tensile strength than the Standard JB Weld. But then I didn't spend a lot of time looking at everything that's out there.
ArthurEld
Solar Wizard
I'd use loctite again. I've never used JB weld. Loctite always did as advertised for me.
Except that that’s not possible (or at least, takes intent if incompetence).
JB Weld specifically requires mixing of two compounds and provides detailed instructions on how to do that mixing effectively (as well as providing a visual cue as to the successfullness if the mixing.
You really have to be a nincompoop or go out of your way to apply poorly-mixed JB Weld.
Sounds like with Loctite Red, not mixing it properly before application is far easier than it should be...
Got it - thanks.
All of my threads are slightly worn and looser than I would like, so it sounds like assuring they set perpendicular to the terminal surface is an effort worth making for me...
3+ hours (~60% to cured) so I removed the nut and checked again.
No change (still as clean as I left it).
Possibly ... although expanding air pockets makes a lot of sense, too. I'm assuming even the aluminum itself would have changed shape due to temperature changes.
I've been using this in general: https://www.amazon.com/gp/product/B012P2WA44
and I'm going to drill a hole in it so I can make a nice final pass at the terminals when I put them together for the "last" time.
Are you using the standard or quick cure stuff?
Thanks.
I should stop saying I used loctite (I forgot that until you just mentioned the bad batch idea). I used permatex red - a different vendor and tested better on strength tests but maybe it doesn't work well in this application.
I’m using standard cure.
Don’t see any advantage to rushing things and if/when I decide to glue more than a single grubscrew in a session, that 4 hour set time is going to be a godsend.
It’s 4-6 hour set time and 15-24 hour cure time.
I’m still deciding how much I want to stress this first terminal but will probably torque to at least 35 inch-lbs if not 40 after it has cured for 48 hours...
Very true. Having used Loctite in other applications, I can say that it will not have the same density out of the bottle if you do not shake it well before use.
If I was to start over, I would use JB Weld again.
I installed my 16 grubscrews in one session and waited 48 hours before I reassembled. I do not have a torque wrench to measure (yet), and I am still very careful when tightening, but the studs feel pretty solid.
I re-top balanced at 3.64 V and then assembled one 4S pack with the BMS. I did another capacity test (same cells) at 0.15C (40 A) and got the exact same results as the first one (267 Ah).
ArthurEld
Solar Wizard
267Ah is typical as far as I know. At least from the cells rated at 280Ah. ?
I’m OK with that. I did retest the capacity after the stud glue-down to get some re-assurance that I had not messed up the terminal surface, even if I thought I had done a good job cleaning the excess with acetone at the time.
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I just JB Welded my second grubscrew and it was also loose enough that I felt the need to use my socket-w/M6-nut jig to hold it perpendicular during the cure.
I don’t have any pristine / unused terminals anymore so I can’t say if they are ‘looser’ than when they first arrived, but I did check the tightness and ‘play’ of both stainless and brass M6 nuts on both M6 grubscrews and M6 bolts and there was always play and seemingly similar to the play I’m getting from grubscrews threaded into my terminals.
When I thread a grubscrew into a terminal thread, it has play and I can move it slightly to one side or the other all the way down until it bottoms (at which point you are counting on the bottom being horizontal, the tapped threads being perpendicular, and the grubscrew threads being centered in the tapped aluminum threads to assure the grubscrew is curing ‘perpendicular.’
So whether it’s because my terminal threads are all slightly worn or not, so think I’m going to continue to clamp my grubscrews vertical while they cure...
The first grubscrew I JB Welded-in into a (non-stripped) terminal has now cured for 48 hours (double the recommended cure time).
I went ahead and torqued down a busbar, first to 35 inch-lbs, then all the way to 45-inch pounds and everything seems to have held just fine.
I also realized that a 1/4” lug on an M6 grubscrew really needs an M6 washer on top of it before torquing an M6 nut, so I’m going to be picking up some of those.
That will also allow me to start curing multiple terminals at a time since an M6 washer on a 5/16” nut will make a good clamping jig to hold the grubscrew perpendicular...
I’ve been using my one short 10mm socket inverted with a brass M6 nut in it as a clamping jig. That works great but I have only 1. The inverted socket provides huge clearance around the thread hole is case any JB Weld oozes out after clamping, but so far, I have seen only a small amount of oozing in the 5-10 minutes immediately after initial threading/clamping and once that has been cleaned up, there has been no further oozing at all.
So my ‘speedy’ process will be:
use inverted socket to clamp just-finished grubscrew
spend ~10 minutes JB Welding in a second grubscrew
remove inverted socket from first grubscrew and install on second grubscrew
clean up first grubscrew and clamp with M6 nut on M6 washer on 5/16” nut
spend ~10 minutes JB Welding in a third grubscrew, etc...
JB Weld has a 4-hour set time, so I could probably do 8 cells / 16 terminals in one shot but will instead aim to do 4 terminals from one little batch of JB Weld at a time. That will take a little longer and waste more JB Weld but should deliver better consistency (and less time pressure).
Happy with how this is all working out.
I went ahead and torqued down a busbar, first to 35 inch-lbs, then all the way to 45-inch pounds and everything seems to have held just fine.
I also realized that a 1/4” lug on an M6 grubscrew really needs an M6 washer on top of it before torquing an M6 nut, so I’m going to be picking up some of those.
That will also allow me to start curing multiple terminals at a time since an M6 washer on a 5/16” nut will make a good clamping jig to hold the grubscrew perpendicular...
I’ve been using my one short 10mm socket inverted with a brass M6 nut in it as a clamping jig. That works great but I have only 1. The inverted socket provides huge clearance around the thread hole is case any JB Weld oozes out after clamping, but so far, I have seen only a small amount of oozing in the 5-10 minutes immediately after initial threading/clamping and once that has been cleaned up, there has been no further oozing at all.
So my ‘speedy’ process will be:
use inverted socket to clamp just-finished grubscrew
spend ~10 minutes JB Welding in a second grubscrew
remove inverted socket from first grubscrew and install on second grubscrew
clean up first grubscrew and clamp with M6 nut on M6 washer on 5/16” nut
spend ~10 minutes JB Welding in a third grubscrew, etc...
JB Weld has a 4-hour set time, so I could probably do 8 cells / 16 terminals in one shot but will instead aim to do 4 terminals from one little batch of JB Weld at a time. That will take a little longer and waste more JB Weld but should deliver better consistency (and less time pressure).
Happy with how this is all working out.
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