Important, use Locking agent for rods!

[Frank in Thailand]

Threaded rods are without doubt the best to use for cells.
The bolts / screws that get delivered with the cells go in the big bucket

I like to share with you the benefits for using locking agent (Loctite)

I have enough cells to test and play.
What I found is that when I use threaded rod in the terminal I can wiggle it slightly.

(Sorry for the simplified "Thaienglish" that's getting a nasty habit..)

This doesn't make me confident to really clamp tight the bus-bar to the terminal.(and i did strip one cell from it's thread)

Result: unstable voltage of the affected cells.
It starts OK but probably oxidation will make the contact worse over time.
Bad contact will make the cells seem to "run" faster to the top and faster to bottom, reduce by this the overall capacity.
(When the affected cell claims 100% full, the rest is at 80%, and when it's bottom the rest is at 20% roughly)

Many posts have been about possible contact loss due locking agent.
Where most of the contact should come from terminal and bus-bar, and the threaded rod play just a small part, it does play a part.

I've tested using the "YR1035+" internal resistance meter for LiFePO4.

No locking agent have 2.08 mili ohms between the terminal and (stainless steel) rod.

At the same hight measured, not yet dry agent give 1.04 and dry 0.8 mili ohms resistance.

I could not measure if the threaded rod without locking agent would reduce resistance when it's been pulled by a nut.

It would probably improve some.

I did kill one cell tighten too strong.
And the ones treated with Locking agent have been clamped more tightly then the one where the thread was pulled out.

It makes the contact strength so much better.

Just make sure your threaded rods are long enough for your mounting plans.
You won't be able to replace them.

 

[DerpsyDoodler]

Threaded rods are without doubt the best to use for cells.
The bolts / screws that get delivered with the cells go in the big bucket

I like to share with you the benefits for using locking agent (Loctite)

I have enough cells to test and play.
What I found is that when I use threaded rod in the terminal I can wiggle it slightly.

(Sorry for the simplified "Thaienglish" that's getting a nasty habit..)

This doesn't make me confident to really clamp tight the bus-bar to the terminal.(and i did strip one cell from it's thread)

Result: unstable voltage of the affected cells.
It starts OK but probably oxidation will make the contact worse over time.
Bad contact will make the cells seem to "run" faster to the top and faster to bottom, reduce by this the overall capacity.
(When the affected cell claims 100% full, the rest is at 80%, and when it's bottom the rest is at 20% roughly)

Many posts have been about possible contact loss due locking agent.
Where most of the contact should come from terminal and bus-bar, and the threaded rod play just a small part, it does play a part.

I've tested using the "YR1035+" internal resistance meter for LiFePO4.

No locking agent have 2.08 mili ohms between the terminal and (stainless steel) rod.

At the same hight measured, not yet dry agent give 1.04 and dry 0.8 mili ohms resistance.

I could not measure if the threaded rod without locking agent would reduce resistance when it's been pulled by a nut.

It would probably improve some.

I did kill one cell tighten too strong.
And the ones treated with Locking agent have been clamped more tightly then the one where the thread was pulled out.

It makes the contact strength so much better.

Just make sure your threaded rods are long enough for your mounting plans.
You won't be able to replace them.

View attachment 37598View attachment 37599View attachment 37600View attachment 37601

If the goal is permanent attachment, why not use something like jbweld?

 

[Frank in Thailand]

Jbweld isn't intended to be used on treads, locking agent is.

Sure, any epoxy will do.
Knock yourself out with strong, stronger and strongest types of glue.

One threaded rod with locking agent takes about 2 minutes to place the agent, screw down the rod, wiggle it, screw little bit further and wipe off the excess locking agent.

Mixing epoxy, and being way more viscose /thick then locking agent, will take a lot more time.

Probably super glue will work great also

(Used in many garages if they run out of Loctite)

That's why

Loctite will give enough additional strength and is intended for this usage.

Jbweld.. not.
Besides this, jbweld is more expensive.

 

[Frank in Thailand]

2 more reasons, depending on the type of jbweld, it will go soft at 50c
Like chewing gum fresh from the package.
I know that the clear jbweld goes flexible around 45- 50C

The Chinese knock-off of Loctite red is conductive.
Jbweld, most types, are not.

 

[DerpsyDoodler]

Jbweld isn't intended to be used on treads, locking agent is.

Sure, any epoxy will do.
Knock yourself out with strong, stronger and strongest types of glue.

One threaded rod with locking agent takes about 2 minutes to place the agent, screw down the rod, wiggle it, screw little bit further and wipe off the excess locking agent.

Mixing epoxy, and being way more viscose /thick then locking agent, will take a lot more time.

Probably super glue will work great also

(Used in many garages if they run out of Loctite)

That's why

Loctite will give enough additional strength and is intended for this usage.

Jbweld.. not.
Besides this, jbweld is more expensive.

After following another thread by farfd, I think I would prefer to just use thread locker from the start. The lengths he went through...just seems like a lot of unnecessary time spent. Apparently it was because he didn’t use something from the start (according to his own analysis).

 

[ArthurEld]

Chinese red looks brown

 

[Frank in Thailand]

Lol

Chinese red looks brown

Yes.
On their defence, so does Loctite red.
It's the colour of the bottle, and it's specific properties

 

[DerpsyDoodler]

Chinese red looks brown

just another thing to boink with us colorblind folks...

 

[Luthj]

I am convinced many of these cells are threaded by someone who is drunk or half blind. Likely without any fixture, and using a cheap tap.

 

[BlitzSSS]

How deep are the threads on these? (assuming M6), and are the battery terminals (and therefore the threaded hole) the same for all the sizes of the batteries i.e 100Ah - 280Ah?

 

[ArthurEld]

I am convinced many of these cells are threaded by someone who is drunk or half blind. Likely without any fixture, and using a cheap tap.

The aluminum is very soft and the threads aren't deep enough so they are weak even if done right.
But like you say some aren't done right.

Form threading would help but these terminals were never meant to be used with screws. At least that is my opinion.

 

[Frank in Thailand]

I am convinced many of these cells are threaded by someone who is drunk or half blind. Likely without any fixture, and using a cheap tap.

You could not be more wrong.
The larger sellers have special equipment to first drill the hole
(With just room for 0.5 mm error)

Then the thread is made using 3 or more different taps, to be able to get the thread almost down to the bottom.

I'm not sure if you ever made M6 treads, I have.
With the "cheap one does it all" type,
And pro equipment.

Aluminium is soft, this mix they use for the terminals is extremely soft, even for aluminium.
(There are several thousand of different types / mixes, each with their own weakness and strength)

From the factory, none of the cells have threads, EV uses different system.

There are sometimes bad cells.
Most of them are made with quality equipment and concentrated workers with craftsmanship.

Remember that 0.5mm error margin!
If we penetrate easy with headless bolts, try to imagine what a thread tap would do, one that you use with more force then you would ever use on incerting the headless bolt!!!

No.
Absolutely WRONG.

Skilled workers that I am surprised for the quality they can produce in this difficult setup.

Sure CNC machine that makes the terminals could do it better.

But..
The terminals are made without thread.

That said, I just received my first bad threaded cell.
(In the 88 cells I own)



This is as far as the thread rod could enter the terminal.

I applied slight force, but kept it normal... Not further.

Lucky for me this is bought locally (Thailand) via Lazada, so I can return without any issues or additional costs.
With $100,- not the cheapest EVE 280's I bought, but fast.
2 days.

In this situation worth it.

 

[Frank in Thailand]

How deep are the threads on these? (assuming M6), and are the battery terminals (and therefore the threaded hole) the same for all the sizes of the batteries i.e 100Ah - 280Ah?

6.5mm deep.

And probably, Yes.
I know fist hand that the terminal for the 152 and 280Ah have same surface area, and same tap.

You lose 0.5 mm at the top due to the slope.

You lose 1mm at the bottom as you can't tread all the way down without going thru the material.

That leaves with 5 mm thread M6.
Where each thread is 1mm spaced.

Normal nuts have 4mm, 4 windings.
The 5th winding is absolutely necessary to get the strength needed in this soft aluminium.

And here is one of the reason they should not provide bolts, at all.
(Usually 8mm)

One bus-bar and you penetrate the terminal, 2 bus-bar and you don't use the 5 threads...

 

[Gazoo]

You could not be more wrong.

Hello fhorst, hope all is well with you..

Lately there have been reports of very sloppy tapping with some of the holes not being tapped vertical to the terminal. Some of the reputable suppliers have been sending out crap. Reports of dented cells has gone up and it appears the suppliers have been sending them out that way. This wasn't happening as often a few months ago and it seems to be getting worse. Basen has been one of them.

When I received my 8 cells from Basen back in October, some of the grub screws (you call the threaded rods and that's fine), screwed in loosely. I used Red Loctite with no primer and the studs are holding well except one I stripped. I have attempted to repair it with JB Weld and have the nut on that stud torqued to 3nm. Been a long and slow process for me and I will be reassembling my pack, hopefully for the last time, and will try to add a little more torque to the nut on that stud.

BTW, Have you tried adding a little oil to the one you are having trouble with? It might help.

 

[Luthj]

Lets just say I know my way around a tap, and how to specify holes in aluminum, even blind ones only 3-4 threads deep.

 

[Frank in Thailand]

My previous order was in August last year.
And the last order of 4 cells, a few days ago.

I was surprised about that one bad thread as it was something I had never seen.

Basen, I never dealt with.
Haomi, Xuba, donguang where my suppliers in the past.
And those where good.
Donguang sold a less good batch to a friend of mine, they stay Chinese..
(Not discriminating, but many Chinese companies do good for a while, build up a good name / thrust relationship and then cash in (in their eyes) or stab in the back (our eyes)

I don't know.
Perhaps there was a company that drilled and tapped all the holes for them, and that's no longer in favour.

Absolutely not that all the cells are badly threaded.
Lately, yes, I see I have one
And it ain't pretty.

I hope for you guys it's just as easily to return as it is for me!

* Oil won't make threads.
It's hard to see in the picture bit the threads don't go deep enough.
The hole is, and there used to be small aluminium chunks on the bottom...

Probably they didn't clean between each tread tap.

The cell I killed (removed the thread) I also used jdweld (local brand) to make the rod stick.

I have the opertunity to place it between other cells and press the bus-bar down on it.
(1 cm thick) so that force alone should provide enough good contact.
Due to my setup, that bar goes over 6 cells. And is a little curved.



Right now, balancing and waiting for the replacement cell


I hope it arrives soon.
Our inverters can do battery less operation, but we still are dark at night.
Off grid have its down side.

The yellow sticker with numbers?
That's the internal resistance 30 = 0.3 Mili ohms.
The 152"s are on average 0.28

The 280's are on average 0.17 with 0.15 as low and 0.185 as top.

 

[Frank in Thailand]

If anyone is interested in knowing more about threads:

What’s On Tap: Hand Taps for Beginners

Rookie Year: The Engineering Intern’s Toolbox (Part 5) A Series of Technical Blogs for Engineering Interns & Entry-Level Engineers Taps are tools that most engineers will come across at some point in their careers. Taps bridge multiple industries and are used practically everywhere. It doesn’t...

www.disher.com

Thanks to @Luthj and this article I now know what a blind tap is
(Well.. that it's called a blind tap)

Tapping thread (true hole) is is fun to do, especially in softer materials like aluminium or copper.
Steel is a task that takes time, focus and patience. (And lots of oil)

Blind taps need higher skill set.