JB Weld versus Loctite for grubscrews

Butcher

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What do you use under the socket head? The surface area under the head is not large.

I would agree with this being trivial but there is 26 pages of trivial here.
 

kuranaga

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these aluminum terminals suck. They should provide solid brass terminals on EVE that can be really tightened down, not this M6 shit
 

Butcher

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But aluminum conducts better than brass. If you can improve the top conductivity, then maybe you don't need to "really tighten down" the hardware.
 

time2roll

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Gazoo

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I would agree with this being trivial but there is 26 pages of trivial here.
In all fairness there were many that ended up stripping the cells terminal threads due to poor threading in the cells' terminals and/or applying too much torque. I was one of those. And much of this discussion happened before cells came or were offered with laser welded studs.

If I had to do it all over I would buy capacity matched cells with welded studs from a reputable supplier. Live and learn :) But I am still happy with my cells considering what I paid for them.
 

SignatureSolarUS

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Signature Solar is based in the original JB Weld facility in Sulphur Springs TX, totally irrelevant but just saying...
 

fafrd

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In all fairness there were many that ended up stripping the cells terminal threads due to poor threading in the cells' terminals and/or applying too much torque. I was one of those. And much of this discussion happened before cells came or were offered with laser welded studs.

If I had to do it all over I would buy capacity matched cells with welded studs from a reputable supplier. Live and learn :) But I am still happy with my cells considering what I paid for them.
We’re all living through a market in a period of phenomenal transition. It’s a different world today than it was 15 months ago when I bought my cells.

Absolutely nothing to feel remorse about - I knew I was diving into a waterfall and have no regrets.

I paid $1400 for a 16 280Ah cells that I’ve had to struggle through more trials and tribulations with than I can count on all fingers to get properly put together as a 2S8P 24V battery (including the problem than caused me to start this thread ;)), but everything is working well now and I hope this battery outlives me.

I’m not getting the full 560Ah / 14.3kWh I payed for, but even at 2/3 that level, this battery cost me under $0.15/kWh in hard costs - less than I would have paid for Lead-Acid.

Family members are asking me about copying my system but I would never consider a DIY battery for them. Today, you can purchase a finished 5.1kWh battery from Signature Solar for $1500 or under $0.30/kWh (and dropping every year).

And for those wanting to go the DIY route to chase the potential savings of up to 50% to be had, it’s looking increasingly likely that true Automotive-grade 300Ah+ cells with welded aluminum fittings are becoming available for prices of $200-250 (for example: https://diysolarforum.com/threads/c...e-data-sheet-certification.31953/#post-388106)

If you can get true matched cells with welded fittings delivering 300Ah+ for $200, that’s going to translate into a more expensive battery at ~$0.21/Wh, but factoring in the much lower frustration / screwing around factor as well as the greater safety, it’s a no-brainer.

So for those stumbling onto this thread because they’ve started down the path of purchasing cheap after/grey-market cells with tapped terminals before it was clear there is a better / safer alternative, good luck finding fixes to the various issues that result.

But for anyone reading this before they have decided on cells, there are better alternatives available now and you really should think twice before heading down this same path (no longer worth it).
 

fafrd

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Signature Solar is based in the original JB Weld facility in Sulphur Springs TX, totally irrelevant but just saying...
Wow, you literally posted this while I was making a plug for your offerings making the DIY route much less appealing than it was even a year ago. Members are going to think I’m a shill for your company ;).
 

Butcher

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So many people should start with a torque wrench. So many male ego's would be damaged if they did. I do not know since I was there, but I suspect, 99% were stripped because of ignorance, not poor manufacturing.

As I mentioned earlier, I have not read all the pages, just about half.
 

time2roll

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So many people should start with a torque wrench. So many male ego's would be damaged if they did. I do not know since I was there, but I suspect, 99% were stripped because of ignorance, not poor manufacturing.
Yes and most effort has been focused on researching maximum torque rather than minimum torque or correct torque.
Mine are set a bit lower at 27 in/lbs - 3nm. Doing just fine.
 

Butcher

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But if you are striving for maximum conductivity, wouldn't more surface area be better?

Coming from the automotive field, I know VW had a small clutch with a lot of effort. They eventually found that having a larger clutch with a pressure plate with less clamping pressure, allowed for less effort for the driver ,and still providing enough clamping pressure to get the job done. Solved a lot of problems.

As I mentioned, I'm new but what I've found, the standard train of thought is that the connection on the bottom is where it's at. Spending any effort on top is a waste of time. I do get that if you do not have a large draw system, that it's a waste of time and effort. I get that but I would think maximum contact area is better than a higher torque. Especially when it comes to aluminum threads.
 

fafrd

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So many people should start with a torque wrench. So many male ego's would be damaged if they did. I do not know since I was there, but I suspect, 99% were stripped because of ignorance, not poor manufacturing.

As I mentioned earlier, I have not read all the pages, just about half.
Absolutely.

I stripped my first (and only) thread by tightening by hand (finger right)…
 

Bob B

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So many people should start with a torque wrench. So many male ego's would be damaged if they did. I do not know since I was there, but I suspect, 99% were stripped because of ignorance, not poor manufacturing.

As I mentioned earlier, I have not read all the pages, just about half.

I am SO glad someone has finally showed up who will save us all from our stupidity.
 

Butcher

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I am SO glad someone has finally showed up who will save us all from our stupidity.
I'm so glad you recognized that. But I really don't believe you should think that everyone is stupid.

I've been wrenching for year and most of them I was some type of Foreman. Once the ego is put aside, people flourish. We all screw up but so often, we blame it on everyone else. 99.9% of stripped bolts happen because they are caused by the person behind the wrench. I swear, 99.9% of the time, the newbie said "It came from the factory that way" or "It's just cheap Chinese junk". Yes, those could be the reasons, but once you accept the fact you screwed up, then you can join the rest of us losers that fail regularly every day.

Once you understand your the cause, then you can understand that you can fix the problem. If you keep blaming everyone else, then you can't fix the root cause. I found the best mechanics accept their failures and at some point have less, as they get more OJT.

But let's get this thread back on track. Enough of this shenanigans.
 

Hedges

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I've never stripped threads in a cast iron head, but I have in aluminum. I've learned to use a torque wrench.

These cell terminals weren't engineered to be bolted, rather welded.
The threads were 6 mm deep (only 4 full threads) and M6-1 thread in very soft aluminum. Fabricated with hand tools by some back-alley "craftsman" so they could be marketed to DIY and other hack users.
Cause for stripped threads is primarily because the joint was cheap crap. How common are stripped threads on circuit breakers and other UL listed components?

I don't believe electrical contact is much a function of area, rather pressure. Actual contact area is far less than dimensions of contact.
 

Butcher

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That may be true. I'm no electrical engineer. Just some butcher that works on German cars. To me, it makes sense that if there is more surface area, the there are more paths for the electrons to flow. Clamping pressure is important but if it's limited [like you mention with these type of batteries] then I would think focusing on surface area would be the next best step.

That is why I'm questioning why this seems to put put off by so many.
 

Hedges

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I found and linked pages showing the vanishing small contact area of a bolted connection. It is just high spots being pressed together. There was a graph showing resistance vs. clamping force. A curve, but that is resistance. Take the inverse (conductivity) it is more of a straight line. In the case of aluminum you have to get through oxide some how. Too much area for a given force, and pressure is insufficient to make good contact. Sometimes smaller is better, especially if you can only apply 3 nm.

People were concerned about getting contact area as large as cross-section of ampacity charts. But I said those only apply for long runs. Heat from smaller contact area escapes in three dimensions. Look at a relay, how small the contact area is for a given current.

Dealing with oxide and preventing the connection from loosening would be my primary concern. But I'm not using these cells; I have AGM with copper & brass bolted cable connections.

There are now cells available with properly welded terminals that have 2-bolt lugs. (vs. earlier welded studs that popped off when someone looked at them cross-eyed). You pay a premium, but avoid all sorts of trouble.
 
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