JB Weld versus Loctite for grubscrews

[fafrd]

So the simple resistivity calculation suggests massive current, but IR drop measurement says a fraction as much.

Contact resistance probably dominates. Not a good thing, because that's where all the energy is deposited. Potentially, one of them goes into runwaway faster than the fuse can blow. Balance of system is supposed to hold together long enough for OCP to clear a fault but these busbars are an unknown quantity and subject to varying assembly techniques.

A UL listed battery would be tested for that. We're crowd-sourcing the test!

Has anyone else measured resistance from busbar to Busbar (through a cell) using deltaV / deltaI method? (ideally on EVE 280Ah cells)

I suspect I did something wrong (light not tightening enough) but it helps to know what others have measured and what you are aiming for (assuming everything was done correctly).

 

[ArthurEld]

So the simple resistivity calculation suggests massive current, but IR drop measurement says a fraction as much.

Contact resistance probably dominates. Not a good thing, because that's where all the energy is deposited. Potentially, one of them goes into runwaway faster than the fuse can blow. Balance of system is supposed to hold together long enough for OCP to clear a fault but these busbars are an unknown quantity and subject to varying assembly techniques.

A UL listed battery would be tested for that. We're crowd-sourcing the test!

And it should be no surprise that the code doesn't allow these batteries unless they are UL listed. But code does allow lead acid batteries that aren't UL listed.

 

[Fpoet]

For what it’s worth, I decided to hook up my 600 inch-lb torque wrench and see how much the JB weld could take. Somewhere between 80 and 100 inch pounds, the screw started unthreading. No JB Weld stuck in the male threads and the female threads look perfect.

I did not clean this bolt with Acetone before glueing it, so it probably came free earlier than it would have if we’ll-cleaned first.

But staying well-attached up past 80 inch pounds means the Allen Head Wrench can probably be skipped when grubscrews have been glued in with JB Weld...

And remember, the Aluminum terminals are only rated for 8Nm / 70 inch-lbs of torque, so I think the overall message is that JB Weld will allow you to ‘export’ the torque rating of the stud to the grubscrew (probably Loctite Red as well, someone needs to perform a similar test using a binding post).

Thanks, that’s good to know! I ordered the small torque wrench you linked, so I will have a more precise idea.

 

[ArthurEld]

The second battery that I used loctite on is causing me trouble.
I put it back together before the loctite was dry and loctite leached out on the terminals. ?

And it doesn't come off with acetone anymore. Scotchbrite either.

I sanded it off. Now that my fingerprints are gone I can rob a bank.

 

[fafrd]

The second battery that I used loctite on is causing me trouble.
I put it back together before the loctite was dry and loctite leached out on the terminals. ?

And it doesn't come off with acetone anymore. Scotchbrite either.

I sanded it off. Now that my fingerprints are gone I can rob a bank.

So the lesson learned is what?

That you need to give Loctite Red it’s full curing period before stressing the threads?

Do you think you may have twisted the grubscrew further into the terminal when assembling the battery?

I’m having trouble understanding how more Loctite leached out if the grubscrew didn’t penetrate more deeply into the terminal from your assembly process...

 

[Pyrofx]

Trapped air pushing out.

 

[fafrd]

Trapped air pushing out.

That doesn’t sound good. The main advantages that attracted me to Loctite Red were that it wicked up into the threads and was easy to clean up.

If it can trap air, pressurize it in the space under the grubscrew and the slowly allow it to expand during the cure time, that pretty much wipes out the attraction (at least for me).

 

[ArthurEld]

So the lesson learned is what?

That you need to give Loctite Red it’s full curing period before stressing the threads?

Do you think you may have twisted the grubscrew further into the terminal when assembling the battery?

I’m having trouble understanding how more Loctite leached out if the grubscrew didn’t penetrate more deeply into the terminal from your assembly process...

On the first battery I didn't tighten the studs until 18hrs after I installed them.
I don't think the loctite was 100 percent cured so hopefully the studs pulled perpendicular without stressing the threads or loctite.
I also wiped off the loctite 3 times hours apart.

The second one I assembled right away. I wiped off the loctite with a rag and assembled it.
The loctite must have wicked out of the hole on the ring connectors and terminals.
I won't do that again. The first method works better.

 

[cinergi]

The second battery that I used loctite on is causing me trouble.
I put it back together before the loctite was dry and loctite leached out on the terminals. ?

And it doesn't come off with acetone anymore. Scotchbrite either.

I sanded it off. Now that my fingerprints are gone I can rob a bank.

Yes, I reported this same problem ... it even leached out after curing (although I didn't use primer) while busbars were connected but only after cycling the battery -- and it found its way between the terminals and busbars! I abandoned loctite for that reason. I was hoping that a proper loctite installation (e.g. using primer) would fix this. I used a metal putty knife to get it off (relatively easy) and refinished the surfaces.

 

[ArthurEld]

Yes, I reported this same problem ... it even leached out after curing (although I didn't use primer) while busbars were connected but only after cycling the battery -- and it found its way between the terminals and busbars! I abandoned loctite for that reason. I was hoping that a proper loctite installation (e.g. using primer) would fix this. I used a metal putty knife to get it off (relatively easy) and refinished the surfaces.

Are you using anything to hold your studs in?

I have 16 cells that I left the studs to cure for 18 hours before adding busbars. The loctite didn't get on anything.
I did have to wipe off any that came out of the hole before it cured though.

edit: I went back and checked my posts and it was 36 hours of cure before I added busbars. My memory can't be trusted.

 

[cinergi]

Are you using anything to hold your studs in?

I have 16 cells that I left the studs to cure for 18 hours before adding busbars. The loctite didn't get on anything.
I did have to wipe off any that came out of the hole before it cured though.

Not anymore. Some of my cells have loctite, some don't. I had some ooze out after first assembly and then AGAIN after cycling the pack to 0 and back. But, that all may be due to 1) using too much and/or 2) not using primer. I'm tempted to try again.

 

[ArthurEld]

I plan to loctite the other 33 cells I have.
The primer isn't expensive but the one they recommend is spray on. I am afraid to get acetone all over.
I used Goof off to get tape off terminals and that stuff melts plastic.

Acetone spray would get on the glue that holds the plastic cover on the cell. I don't know what that would do.
The liquid primer is harder to get and more expensive and the product # doesn't match the # loctite recommends.

 

[Hedges]

Spray in a glass, dab with Q-tip (cotton and wood, if acetone wants to dissolve synthetic and plastic)

Was going to say mask with an aluminum pie pan or foil, but that would short and throw sparks.
Mask with wood or other non-conductive, non-plastic material having a hole, and spray through that.

Does spray can support a tube? or accept a nozzle that does?

 

[fafrd]

OK, I just took the plunge and glued in my first grubscrew with JB Weld.

Approach and impressions (so far):

1/ Used Allen wrench to measure/calibrate how many turns to bottom (5-3/8 turns in this case).

2/ used Q-tip to clean aluminum threads and stainless threads with Acetone and let dry.

3/ mixed 2 ~1/4” dabs (black and white) of JB Weld and attempted to get a dab into the bottom of the terminal thread using a matchstick with mixed success (a bit on top and some down the threads).

4/ filled the ‘cup’ on the bottom of my grubscrew and left a pyramid of JB Weld sticking up (in all, I used over 75% of the JB Weld I mixed).

5/ inserted the grubscrew and started counting turns - it went easily to ~3-1/2 turns before for increased.

6/ every minute or so it became easy to turn another 1/8th turn with the Allen Head wrench, so I continued in this way all the way to 5-3/8 turns (bottomed).

7/ JB Weld oozed out around the entire grubscrew but primarily from one spot at the top. When the gob got large enough, I would remove using the bent end of a paper clip. Pretty easy to keep clean but some JB Weld got on the terminal surface.

8/ Used paper towel to wipe JB Weld off of terminal surface several times and after tightening was complete I used a Q-tip and acetone to wipe down the entire terminal surface.

8/ Placed a brass M6 nut into an M6 socket and threaded onto grubscrew (socket facing up, 1/4” drive hole facing down).

9/ Inserted Allen Head wrench into grubscrew to prevent any further turning and tightened socket with nut down to terminal finger-tight.

10/ Again using Allen Head wrench to prevent any further turning, I removed socket and nut to inspect - no additional JB Weld has oozed out and the terminal surface appears clean. Replaced socket and nut and retightened to let set.

Observations:

A/ JB Weld is fluid enough to ooze out through thread space. Because I got some JB Weld oozing out around the entire circumference of the grubscrew, I’m pretty confident it has filled the entire threadspace. The key is to apply pressure slowly so that it has time to flow.

B/ It’s difficult to control placing JB Weld only in the bottom of the hole. I may try less at once next time but it’s difficult to avoid getting some on aluminum threads as well as terminal surface.

C/ it’s pretty easy to get a nice ‘pyramid-shaped’ gob on the bottom of the grubscrew. This prevents against the possibility of an air bubble being trapped there, but I’m worried that quantity alone may not be enough to ooze out of the top (hence the reason I attempted to add more into the bottom of the hole using a matchstick).

D/ I’m frankly surprised by how much JB Weld remained in the hole after threading/bottoming. I’d guess ~1/2 of what I managed to insert into the hole before threading ooozed out of the top, so I’m probably try putting in only ~half as much into the hole next time (with an equal amount on the grubscrew).

E/ Overall, I’m pretty happy with how smoothly this went and the greatest potential issue I see is whether I really cleaned all of the epoxy off of the terminal surface or not. It looks clean but impossible to know if there is an ultra-thin layer still there or not? Since I will be lightly sanding with Emory paper prior to final assembly, I’m not overly concerned (since any remaining material must be atoms thick and should sand off with the oxide).

F/ also very happy with the ‘inverted socket’ solution to assuring a vertical grubscrew, but it is slow (one terminal every 24 hours) so I’ll either need to get a few more M6 sockets or find another approach...

Will report back in 24 or 48 hours but this seems to be working well enough that I am planning on using JB Weld to secure all of my terminals and may next attempt to fix my partially-stripped thread...

 

[Hedges]

B/ It’s difficult to control placing JB Weld only in the bottom of the hole. I may try less at once next time but it’s difficult to avoid getting some on aluminum threads as well as terminal surface.

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[Gazoo]

Replaced socket and nut and retightened to let set.

I would be careful. I think it's possible for some of the JB to ooze up even though you took precautionary steps.. Not saying it will happen and I don't know. Personally I would not recommend putting a nut on until it is fully cured.

 

[fafrd]

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Nice idea if your plan is to mix up a big batch of JB Weld and secure all of your terminals in one session, but too much overhead if doing one or two terminals at a time as I am...

I think there are another couple options to explore including using something small than a toothpick such as a paper-clip to apply less at a time as well as seeing whether you can apply a large enough volume to the bottom of the grubscrew to fill the threadspace and ooze out of the top (which will be easy-peazy, if possible).

 

[fafrd]

I would be careful. I think it's possible for some of the JB to ooze up even though you took precautionary steps.. Not saying it will happen and I don't know. Personally I would not recommend putting a nut on until it is fully cured.

Well first, I want a nut on the grubscrew to assure it is oriented vertically.

And second, since I can easily remove and inspect on whatever schedule I deem necessary, I’m not overly-concerned about additional material oozing out before it has set - the socket is well back from the thread hole and any additional material that oozes out before the 6-hour set time will easily be removed and cleaned up.

And lastly, being careful to avoid bubbles as I have should mean there is little reason for additional material to ooze out. If trapped gas is under pressure, that can result in additional material oozing out over time, but I was pretty careful to apply the JB Weld from the bottom-up, which should mean that once the grubscrew has been threaded to the bottom and the last dose of pressure allowed to equalize (which takes less than a minute), there is no remaining force to cause additional material to ooze out over time...

It’s now been over 90 minutes and because of your post, I just removed the nut and checked again - no change (we’re now 1/3rd of the way to the set time).

 

[cinergi]

My loctite oozed as a result of charge/discharge ... and it may not have been trapped air pushing it around. Anyway, I would do a complete discharge and then a charge, and then disassemble and make sure no more has oozed out (all of this after curing of course). Cuz I had a lot of loctite UNDER my busbars after a discharge & charge (and I waited 24 hours for it to cure; albeit without proper primer)

 

[fafrd]

My loctite oozed as a result of charge/discharge ... and it may not have been trapped air pushing it around. Anyway, I would do a complete discharge and then a charge, and then disassemble and make sure no more has oozed out (all of this after curing of course). Cuz I had a lot of loctite UNDER my busbars after a discharge & charge (and I waited 24 hours for it to cure; albeit without proper primer)

Well that’s certainly a cautionary tale - do you think expanding cells put enough pressure against the thin bottom of the terminal to reduce volume of the thread cavity?

At this point, I already glued my grubscrew in and it was bottomed (so pressing against the bottom of the M6 hole). So I’m going to let it cure a full 24 hours before stressing and at that point I’ll probably charge that first cell to 3.65V in my little jig to make sure nothing breaks (don’t see how I can get any more oozing at that point because the JB Weld should be rock-solid after 24 hours).

Loctite is a bit more of a mystery than epoxy as far as hardening - the fact you still had oozing after 24 hours means it obviously had not fully hardened (crystalized?) by that point...

Of course, before I can charge that cell I’ll need to glue a grubscrew into the other terminal...

Did any of you end up purchasing those hollow dowels with sandpaper glued onto the end? That seems like the best way to clean off the terminal surface after all the messy work is done and before final assembly...