New Supplier for 280Ah cells: Shenzen Basen

[Ampster]

I'm assuming sales tax is not charged?

Yes, Alibaba probably does not do business in your State so there is no way your State can follow up. There may be a voluntary way for you to make a donation if you are feeling guilty. LOL

I live in California and already support the government enough that I do not feel guilty. I also have no qualms about providing my own power and only using the grid for backup.

 

[Gazoo]

I plan to use grub screws and nuts but I can't wrap my head around the Loctite. From what I read standard Loctite is not conductive. Are you guys putting the Loctite onto the grub screw?

Yeah I had a senior moment too when I saw it being suggested. As has been said it's the surface area of the terminal that matters. Stainless steel is not a very good conductor anyways compared to aluminum. Some have suggested giving the buss bars and terminals a "cleaning" using emery cloth. I will have to wait until I get my stuff to see if it's necessary.

Now to find some quality buss bars that will let me do the cube configuration without having the 90 degree bar longer.

That is a challenge for some of us sure. I would like to do the square pack but one of the connections between the terminals is too long for these buss bars. If doing the square configuration I will order a premade cable to connect to those two terminals. Not the best solution but it will work. I have no way of making my own buss bars.

 

[The New JC777]

Duh. How did I not think of that. Senior moment

I hate it when that happens. The terminals on these cells are a smaller than the diameter of a dime so the surface area is small but adequate if .5c rate is the max current (140amps) and that leaves you a little head room. Clean, bright, and correctly torqued connections are imperative and are more of a concern to me than the 10mm difference in the length of a single bus bar in series. Having said that, I will use a 3/16" thick bar when it comes to making that one bar. The OP is using aluminum bus material as he has experienced corrosion in military aircraft, as have I but, I have plenty of 1/8 x 1" copper flat bar and will make bars after the pack is fully assembled and clamped. I will use a .25" bit to drill the holes and will not elongate the holes to maximize the contact patch. As much as I hate to do it, I will use a anti corrosion compound between the bar and the terminal then warm it up with the wife's blow dryer so it flows into all the nooks and crannies of the connection.

 

[hammick]

There may be a voluntary way for you to make a donation if you are feeling guilty. LOL

Yeah I had a senior moment too when I saw it being suggested. As has been said it's the surface area of the terminal that matters. Stainless steel is not a very good conductor anyways compared to aluminum. Some have suggested giving the buss bars and terminals a "cleaning" using emery cloth. I will have to wait until I get my stuff to see if it's necessary.

That is a challenge for some of us sure. I would like to do the square pack but one of the connections between the terminals is too long for these buss bars. If doing the square configuration I will order a premade cable to connect to those two terminals. Not the best solution but it will work. I have no way of making my own buss bars.

Any reason I can't use the 4/0 interconnects I currently use with my L16 48v series bank? Obviously I would need to get 8 more of them.

 

[Gazoo]

Why would you need 8? Added length between the cells will add to some voltage drop. And it's a good idea to keep the terminals as stress free as possible. Other than that I suppose it would work and if I am wrong someone can correct me. But it seems a messy nonproductive way to connect the cells. Unless you have some reason for it?

 

[The New JC777]

I think the 4/0 will have minimal resistance provided the lug crimps are good.

 

[nebster]

I wouldn't try to force a 4/0 onto these small studs we're making with our grub screws. Unless they're already exactly the right length by some lucky chance. It's much more of a mechanical concern than an electrical one; I agree with you that properly-crimped lugs would be fine from that standpoint.

 

[Haugen]

6mm isn't much depth and I think I will have a less chance of stripping using bolts.

At 1mm pitch, that is 6 threads which is twice the recommended engagement for a fastener that is used as a rule of thumb for mechanical engineering.

 

[ArthurEld]

I'm using studs and loctite. I want all the thread I can get.

 

[Ampster]

At 1mm pitch, that is 6 threads which is twice the recommended engagement for a fastener that is used as a rule of thumb for mechanical engineering.

I am not a Mechanical Engineer so I don't know if that rule of thumb applies to a connection if dissimilar metals?

There have been reports of the aluminum threads being stripped or distorted. Therefore my risk adverse approach has been to use studs so I can optimize the number of threads that are engaged. Perhaps my philosophy is is also influenced by the fact that most of my experience has been with metal screws into wood drywall or plaster where more than three threads means better pullout strength.

 

[Ampster]

I can't wrap my head around the Loctite.

I use Loctite to keep the grub screws from turning and pushing through the bottom of the aluminum terminal. That way I don't have to hold them with an allen wrench when torquing down the nuts. I use Nordloc washers to keep the nuts from loosening.

 

[Frank in Thailand]

Studs / headless bolts are the "best" as there is no twisting force when you tightening the nut.

For loctite, there is special that is conductive, according to their site.

I have no knowledge of numbers of threads being standard, most nuts are 4mm for M6 thread.
The 6mm in the terminal should normally be sufficient, and using studs the 8Nm torque (see manual)
should not damage the aluminium thread.

The cells should be compressed together with 200kgf on the flat sides, this to prevent delaminating.

My 280Ah look like they are vacuum, dented slightly inward.
My 152Ah never looked like this, and are slightly bloating / delaminating as I did not compress them together...

Lesson learned..
Not to make that mistake again

I read that professional installers (for UPS in telecom houses etc) use silver conductive paste.
I found on Amazon, but too expensive to get to Thailand.

I now use silver paint, the kind you use to repair PCB lines.
It fill all the tiny gaps in the terminal and bus-bars, and acts as some protection against galvanic corrosion.

Be sure to clean the aluminium terminals and bus-bars till they are as free of corrosion as you can get them.

Aluminium oxide fast, you have enough time after cleaning to mount.

Just don't clean 32 cells and start installing afterwards..
Better small portion of 4, install, next set.

 

[ArthurEld]

For loctite, there is special that is conductive, according to their site.

Thanks for that. I was worried about mistakes.
I will be careful but I imagine even a thin amount of regular loctite could effect the connection.
And it will be harder to clean up once the studs are in.

 

[Haugen]

I am not a Mechanical Engineer so I don't know if that rule of thumb applies to a connection if dissimilar metals?

There have been reports of the aluminum threads being stripped or distorted. Therefore my risk adverse approach has been to use studs so I can optimize the number of threads that are engaged. Perhaps my philosophy is is also influenced by the fact that most of my experience has been with metal screws into wood drywall or plaster where more than three threads means better pullout strength.

I'm not a mechanical engineer either, but I work with a lot of different disciplines, so as we all work to our strengths, bits of the others are learned.
It's the same concept whether you are talking wood screws or machine screws. To reach the recommended torque for the clamping force desired, you should always engage at least 3 threads to have the surface area to pull against.

 

[Haugen]

I read that professional installers (for UPS in telecom houses etc) use silver conductive paste.
I found on Amazon, but too expensive to get to Thailand.

I now use silver paint, the kind you use to repair PCB lines.
It fill all the tiny gaps in the terminal and bus-bars, and acts as some protection against galvanic corrosion.

Silver is a very noble metal in comparison to aluminum. Even a nickel/silver is higher up than copper. That might work well on copper, but I wouldn't recommend that approach on aluminum.

 

[Ampster]

It's the same concept whether you are talking wood screws or machine screws. To reach the recommended torque for the clamping force desired, you should always engage at least 3 threads to have the surface area to pull against.

That is not how the uplift calculator that UniRac used to determine how deep I had to embed lag screws. If I recall it was considerably more than three screw lengths. They were very specific as to the diameter and the depth of the screw into the wood. I don't remember if there was a torque requirement also.

 

[hammick]

Why would you need 8? Added length between the cells will add to some voltage drop. And it's a good idea to keep the terminals as stress free as possible. Other than that I suppose it would work and if I am wrong someone can correct me. But it seems a messy nonproductive way to connect the cells. Unless you have some reason for it?

No reason other than I already own them. You only need 7 interconnects for a 48v bank of 6v batteries. So I would need 8 more for my 16s bank. They are 10" long to keep the temps down between the lead acid batteries. Probably makes more sense to sell them with the batteries and start over with bar type interconnects.

 

[Frank in Thailand]

Silver is a very noble metal in comparison to aluminum. Even a nickel/silver is higher up than copper. That might work well on copper, but I wouldn't recommend that approach on aluminum.

It's being "painted" on the aluminium, with it there is no oxygen , no galvanic corrosion.

The next layer, copper bus-bar have the same result, no oxygen, no corrosion.

Sure one could use anti oxidation paste like vaseline or oxi-guard, but they are non - conductive.

I would not advise to place a paper thin sheet of silver between aluminium terminal and copper bus-bar..

"Sealing" the aluminium terminal with silver conductive paste is something professionals do at critical installations.

I am not this professional, I can't get into discussion the how and why.
I'm sure they have absolute good reasons to use the expensive material.
They would not use it if vaseline would work just as good.

 

[Haugen]

It's being "painted" on the aluminium, with it there is no oxygen , no galvanic corrosion.

The next layer, copper bus-bar have the same result, no oxygen, no corrosion.

Sure one could use anti oxidation paste like vaseline or oxi-guard, but they are non - conductive.

I would not advise to place a paper thin sheet of silver between aluminium terminal and copper bus-bar..

"Sealing" the aluminium terminal with silver conductive paste is something professionals do at critical installations.

I am not this professional, I can't get into discussion the how and why.
I'm sure they have absolute good reasons to use the expensive material.
They would not use it if vaseline would work just as good.

You need to read my links about galvanic corrosion. I have posted them several times.
I don't care how "sealed" your connections are, oxygen and moisture will intrude. If you can preserve the integrity of a seal better than a connector designed by teams of engineers and refined over decades, well, then you should be making an impressive salary.

 

[Frank in Thailand]

You need to read my links about galvanic corrosion. I have posted them several times.
I don't care how "sealed" your connections are, oxygen and moisture will intrude. If you can preserve the integrity of a seal better than a connector designed by teams of engineers and refined over decades, well, then you should be making an impressive salary.

Excuse me...???

We are still talking about LiFePO4 cells with aluminium terminals and copper bus-bar?

Especially the 280Ah type who is not around for decades.

If you talk about the rubbish lead acid terminal connections refined for ages each new and improved and all give the nice white / green / blue powder over time....
The people who get paid for that invention should live in a carton boxes after 100 years it's still a problem.

LiFePO4, especially the type we use for our DIY power walls is around a few years.

Our DIY connection is not the way it's been built into electric busses.
The 6mm threaded holes are drilled for our convenience by the sellers and not the factory.

So please, enlighten me.
What connection you know of that has been designed by teams of engineers and refined over decades, for this "new" terminal contact??

Pictures please!!!

I am genuinely interested to know what you know.

It can't be treated rod/headless bolts and bus-bars...
You don't need a team of engineers for that.

I really like to know.