Lifepo4 cells in a fixture, but no insulation in between. Would you buy?

[meetyg]

Hi all.
Recently a guy on FB posted that he's selling new 8s LFP packs, 200Ah.
From a short call with him, I understand that these are new in box, surplus from an energy storage project that didn't go through.

I asked for the datasheet of the cells, but it doesn't mention exactly who the manufacturer is (looks like a reseller datasheet). Anyways, they are very similar to GFB cells found online.

One thing that caught my eye, is that it doesn't seem to have insulation between the cells. When I asked the guy, he said that these are in a solid fixture, and he hasn't heard of a need for insulation in between (he isn't the manufacturer anyways). That's not to say that there isn't, it may be very thin, looking at the pictures he sent:


So let's just say there isn't any... But the fixture/compression is solid (looks like aluminum housing, probably not removable).
Around the cells you can clearly see there is the yellow fiberboard.

Is this a problem? We all know that cells can expand and contract, possibly even under compression/fixture. I'm worried that with time, the blue shrink wrap could wear out between the cells and cause a short (usually the aluminum housing of these cells is somewhat negative).

I'd like to hear your thoughts.
He's selling them for a good price (compared to local options available, not like in the U.S.) and I might be able to bring him down a bit more.

 

[Q-Dog]

I'll take 4.

 

[S Davis]

I wouldn’t, but mostly because of the welded terminals. If you have a bad cell it is difficult to replace.

 

[meetyg]

I wouldn’t, but mostly because of the welded terminals. If you have a bad cell it is difficult to replace.

Yeah, I also don't like welded, but of course I will do some testing initially. Might as well get some spare packs, but yeah, that's another downside.

 

[Q-Dog]

Are you really going to replace a failed cell? Those metal cases look like they may be welded together too.

I assume my sealed up plastic case batteries have welded terminals.

 

[meetyg]

Are you really going to replace a failed cell? Those metal cases look like they may be welded together too.

I assume my sealed up plastic case batteries have welded terminals.

No, I probably won't replace a cell if underperformed, I will replace the whole pack.
But welded cells are pretty common in most off-the-shelf batteries. I agree that it's a downside for a DIY build, but I'm less concerned with it.
I'm concerned with the possibility that these cells don't have separation between them.

I might be able to see these packs in person in a about a week.

 

[wpns]

I'm concerned with the possibility that these cells don't have separation between them.

I might be able to see these packs in person in a about a week.

Yeah, that’s really disconcerting, if you see them in person and they don’t have any separators between the cells I’d regretfully walk away no matter how good the price is. That’s a non-repairable bomb waiting to go off some random time in the future, maybe years from now when you’ve gotten complacent. Which greatly complicates the disposal aspect.

Looks nice except for that, wonder why the project failed?

 

[meetyg]

Yeah, that’s really disconcerting, if you see them in person and they don’t have any separators between the cells I’d regretfully walk away no matter how good the price is. That’s a non-repairable bomb waiting to go off some random time in the future, maybe years from now when you’ve gotten complacent. Which greatly complicates the disposal aspect.

Looks nice except for that, wonder why the project failed?

Thanks for your input.

I'm not really sure why the project failed. From what I understand, this guy is somewhat of an investor. He has a battery expert as an associate, but he mentioned that they are both too busy to do the manual labor involved in the project.
This expert is one-of-a-kind in our country: he repairs EV/Hybrid battery packs. He actually repaired a Tesla Roadster that was imported (after alot of bureaucracy and paperwork) as an inheritance. But as mentioned, he's too busy...

Since you asked, this is what I understood:
The project is to build energy storage racks for EV charging. I suppose for places where the grid infrastructure is lacking, and/or to use solar to charge the racks up.



When I contacted the guy, he asked if I'm a professional. I said that it's more of a hobby than a profession. I also mentioned that these types of racks are usually high-voltage, so he needs people with adequate knowledge and experience (not to mention certification) to work with such packs.
In my country the laws and regulations pretty much kill anything DIY, especially when it come to solar and electricity. So we don't have many people that actually know how to build a battery pack. We have plenty of solar installers, from large to small, but they only know how to "plug and play" things.
So I suppose he is now understanding that this project is more complicated than he thought, and trying to get some return on investment by selling the components (mainly these 8s packs and the huge storage racks). Without knowledgeable people to do the work, this project is stuck.

Anyways, one of the reasons I am reluctant to mention where I'm from in the world (let's just say somewhere in the Middle-East), is because even my little backup solar setup could be considered illegal, even though I'm not exporting to the grid.

It's a shame, but that's what it is...
I believe that if the regulations where more DIY friendly, we would have more people with knowledge to do more.

 

[yabert]

They look like EV battery module (VDA form format).
Automotive grade battery module sound good to me.

About the thin wrap around the cells, I've dismantle CATL prismatic cells last year. They was highly glue to a aluminum plate and I tear the thin wrap of a cell. Then I remarqued there is multiple layer of warp.
Bottom line, those modules look nice to me.

 

[wpns]

So we don't have many people that actually know how to build a battery pack

Right, so who designed those packs, and who built them? If they were designed and built without proper separators (electrical insulators) between each cell, then run away.

 

[LakeHouse]

Hi all.
Recently a guy on FB posted that he's selling new 8s LFP packs, 200Ah.
From a short call with him, I understand that these are new in box, surplus from an energy storage project that didn't go through.

I asked for the datasheet of the cells, but it doesn't mention exactly who the manufacturer is (looks like a reseller datasheet). Anyways, they are very similar to GFB cells found online.

One thing that caught my eye, is that it doesn't seem to have insulation between the cells. When I asked the guy, he said that these are in a solid fixture, and he hasn't heard of a need for insulation in between (he isn't the manufacturer anyways). That's not to say that there isn't, it may be very thin, looking at the pictures he sent:
View attachment 285614View attachment 285615View attachment 285616

So let's just say there isn't any... But the fixture/compression is solid (looks like aluminum housing, probably not removable).
Around the cells you can clearly see there is the yellow fiberboard.

Is this a problem? We all know that cells can expand and contract, possibly even under compression/fixture. I'm worried that with time, the blue shrink wrap could wear out between the cells and cause a short (usually the aluminum housing of these cells is somewhat negative).

I'd like to hear your thoughts.
He's selling them for a good price (compared to local options available, not like in the U.S.) and I might be able to bring him down a bit more.

I would guess that there is insulating material between the cells. They knew enough to insulate between the cells and the case and they had it handy (see the yellow material visible on the ends and sides). I think they probably slipped some between the cells too.

On the other hand, if they didn't, I would not buy these. The blue shrink-wrap isn't enough insurance against mayhem that would ensue if two of those cell cases shorted.

 

[yabert]

without proper separators between each cell, then run away

Well, no separator in my battery from the biggest battery supplier in the world (CATL).
I bet they know a thing or two about building battery module.

Thread 'What 282 kWh CATL LFP look like'

Nov 5, 2023

I was really lucky and was able to bought new old stock of four 70.5 kWh CATL batteries built to be use on electric truck (class 6-7... you know, big truck, but not semi).
I didn't really know what was inside at the time of purchase except they are 70.5 kWh, 96S (309V nominal) and 228Ah cells build in 2020. My main goal was to have one 24V or 48V 70.5 kWh battery in our house and sell the other 211 kWh.
I received the 4 batteries few days ago and I uncrated one to see how it build.
I measure the voltage between one terminal and the disconnected MSD, 315V, good.
I removed the lid and fu*k...

• yabert
• Replies: 60
• Forum: DIY LiFePO4 Battery Banks

• 
• 
• 

 

[LakeHouse]

Well, no separator in my battery from the biggest battery supplier in the world (CATL).
I bet they know a thing or two about building battery module.

Hard to argue with the logic.
And yet I still wouldn't be happy if there was nothing other than the shrink wrap.

 

[meetyg]

Well, no separator in my battery from the biggest battery supplier in the world (CATL).
I bet they know a thing or two about building battery module.

Thread 'What 282 kWh CATL LFP look like'

Nov 5, 2023

I was really lucky and was able to bought new old stock of four 70.5 kWh CATL batteries built to be use on electric truck (class 6-7... you know, big truck, but not semi).
I didn't really know what was inside at the time of purchase except they are 70.5 kWh, 96S (309V nominal) and 228Ah cells build in 2020. My main goal was to have one 24V or 48V 70.5 kWh battery in our house and sell the other 211 kWh.
I received the 4 batteries few days ago and I uncrated one to see how it build.
I measure the voltage between one terminal and the disconnected MSD, 315V, good.
I removed the lid and fu*k...

• yabert
• Replies: 60
• Forum: DIY LiFePO4 Battery Banks

• 
• 
• 

Yeah, kinda odd, isn't it?
I mean all the DIY server rack batteries (and possibly most of the pre-made) give you/have insulators for putting between the cells.
We have seem some catastrophes here on the forum from DIY packs that didn't have cell separation.
Maybe with the proper compression and solid fixture, we really don't need it?
I'm stumped...

Your post reminds me of a BYD blade (mini?) battery teardown from Monroe on YT.
I say mini because this was from a BYD Shark (hybrid truck), and the cells were half the length of the standard BYD blade cells.

They separated the cells, and I couldn't see any special separation between them, other than the blue wrap. I think I saw in another video that these cells are actually double wrapped, but still, this wrap is too thin in my opinion.

In that video the cells were also glued at the bottom, like you mentioned in your post.

Even with the best fixture and adequate compression, I still don't understand how they allow themselves to build such packs for harsh mobile applications (EV cars, trucks and busses).