diy solar

diy solar

EVE-280 cells should these be clamped tight or spaced for expansion?

I received an answer on my qeustion, send directly to EVE.

As you can find from the attached picture, the cells are fastened tightly when assemble from cell into a pack, the fixture is a simulation of the real usage situation and cells are fastened tighly by steel band. The 300kgf= 2940N is a force from outside.
Have you got the attached picture ?
 
I received an answer on my qeustion, send directly to EVE.

As you can find from the attached picture, the cells are fastened tightly when assemble from cell into a pack, the fixture is a simulation of the real usage situation and cells are fastened tighly by steel band. The 300kgf= 2940N is a force from outside.

We will finally have the answered if you post the picture!!!
 
the fixture is a simulation of the real usage situation.
module.jpg

I do not know at which SOC the 300kg force should be applied from the outside..
I also can't imagine how to use steel band with aprox. 300kg force. How do you want to measure it?
I would use a compression spring if I had to build a housing.
 
A lot of good comes out of high jacks. Things that probably wouldn't be said otherwise.
51CbI9BSi6L._AC_SX466_.jpg
 
So a metal plate with a thing for the straps on top of it with screws that can be used to generate pressure, very interesting.

I see myself putting 48 cells in a long line, compressing with straps, then charging and looking to see the total stack length not change
 
You guys solved it they are good as new old stock. For the price I'd give up some capacity.
Being a couple years old seems like a non issue. They know what state of charge to leave them.
I would say that buying 4 at a time is asking for outliers. If they are doing any kind of matching it would be much harder to match the ones that are odd. To match 16 odd ones is probably impossible so they have to sell the odd ones in small orders. And they are likely to be mixed with old ones.
Good as new old ones.
 
You guys solved it they are good as new old stock... Good as new old ones.

While I think this is somewhere between possible and the most likely situation, I would encourage you not to confuse informed speculation and best guesses for fact, and accept it is quite likely we will never have 100% clarity (or anything close to that) about the quality, condition, or reason for discount for these cells or really any other grey market cells.

We do have reason to believe they are old stock (best guess as to how to interpret date codes), that is not evidence for or against them being 'good as new'. In the 6-8 months since they became known and popular, there have been scattered issues, but for the most part people have had good experiences, and have been within spec insofar as we have the ability to verify that (which is very rudimentary). Steve and others have noticed that matching is basic at best (undoubtedly part of the reason they are priced as they are), partially because resellers are not well equipped to do so, and partially because margins are too thin to justify the time and cost. We do have 6 or so months of experiences by forum members and a lot of research to base our speculation on. But we still do not know very much, and probably never will. This uncertainty is in my eyes factored into the price, and a big part of why they are sold at 1/2 to 1/4 the cost of true new, grade-a, matched and tested cells through official channels. Accept this uncertainty, and don't conflate what you hope to be true with what we know to be true and you will probably not be let down.

I say this not to be negative, but because I think that (1) not over-representing things and not being over-confident in what we think we know or want to believe is important for new and potential buyers, and (2) realistic expectations and realistic risk assessment greatly improves the chances of you being a satisfied customer, and hopefully having your expectations exceeded.

I do think the EVE cells are a great deal, and I do think that the collective experience and track record we are building with them and with some of the more popular sellers counts for a lot and makes them a lot more attractive. But I do think its important to stay aware of the trade-offs with grey market cells, and understand as best we can the realities of the market we are operating in.
 
My comment was pure speculation. But I am fairly sure there is no way to match cells without mixing them up It wouldn't be called matching if they didn't mix them up. It would just be called testing.
 
If they are really matching cells it would be some major sorting operation. They'd have matched stock sorted. Any cells that couldn't be matched for a set would sit until something came along that matched them.
And the videos they make with your name on it wouldn't have anything to do with that. I don't know what all the testing they claim to do is. They said it took days to do mine. I did't ask for testing or matching or special boxes. But I did say I found them on this forum. April asked me to post pictures and say nice things about Deligreen. I said send me good product and I will say nice things.
Even if they lied about matching cells they would have to mix old ones with newer ones just so it looks like they are matching them.
 
If they are really matching cells it would be some major sorting operation. They'd have matched stock sorted. Any cells that couldn't be matched for a set would sit until something came along that matched them.

I suspect this is further than they go. But I hope that I am wrong. All I have seen is voltage check + IR check, I do hope they do more, but I haven't seen evidence, or seen any supplier explicitly and directly state that they match beyond this. Maybe some test and match capacity, it seems that this is what Deligreen is implying. I believe Deligreen is a larger reseller than those we often deal with, its possible they have greater capabilities or more efficient processes, but I wouldn't assume it without some evidence or at least assurances.

My comment was pure speculation. But I am fairly sure there is no way to match cells without mixing them up It wouldn't be called matching if they didn't mix them up. It would just be called testing.

Possibly yes, though in theory cells from the same factory, batch, and date stand the best chance of being well matched.

But since the resellers are not getting and matching batches of new cells off the line, I'm sure mixing and matching is the norm.

And the videos they make with your name on it wouldn't have anything to do with that. I don't know what all the testing they claim to do is. They said it took days to do mine.

It would be interesting to know what testing Deligreen does, or claims to do. It sounds like they may capacity test the cells if the testing really takes days. On the other hand, maybe it just takes them a few days to get around to making a video with the multimeter and IR readings. Did they spell out what/how they test in any of your correspondence.

Of course, you would think if they were going to capacity test, they would do this as they receive the cells, this would be much more efficient for them (if they are capacity testing all cells) and allow binning and faster shipping.

Even if they lied about matching cells they would have to mix old ones with newer ones just so it looks like they are matching them.

I hope they would not do this (lie, but also mix and match to make it look like they are matching), the extreme best practice for applications where matching is very important is tightly matched cells from same factory, batch, date and if possible in cronological order (serial number). At least this is what I learned from Nordkyn and Marinehowto. This is overkill for most of our applications, and can't be done by the resellers we buy from or at the price we pay. But point being, they would be shooting themselves in the foot if they mixed cells around to pretend they are matching.
 
I doubt people are mixing them up so it looks like they are matched. Somebody has to test them and record the results.
Then somebody has to take that data and sort the cells. Somebody probably matches them at some point.
Maybe the testing Deligreen does is just to be sure they are matched. But if they find one that doesn't match then they have to replace it. There's no way to make that one match.
 
I doubt people are mixing them up so it looks like they are matched.

I must have misinterpreted what you were saying in your previous comment

Somebody has to test them and record the results.
Then somebody has to take that data and sort the cells. Somebody probably matches them at some point.

I think that you may be over-estimating the amount of testing, sorting, and matching that the grey market resellers are doing. Maybe some of the better or larger ones are doing more testing than I think. All I have seen for sure is a voltage + IR test at time of sale. I wonder if anyone else has seen evidence of further testing or matching. Or has any more insight into the selection, testing, and matching process of these resellers.

Maybe the testing Deligreen does is just to be sure they are matched. But if they find one that doesn't match then they have to replace it. There's no way to make that one match.

I was thinking the same thing, which is why I suspect they are not actually capacity testing at point of sale, because as you stated, if they capacity test your cells and some are mismatched, they have to start again with more cells. It would be much more logical to do this as cells come in and record or bin them at that point, but I think it is more likely that they do not capacity test at all, and sell at the cheap prices they do to compensate for this. As you can tell I am very skeptical of the Chinese resellers doing anything beyond what they explicitly show or provide evidence of or at least explicitly promise to do.
 
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Craig goes through an extensive process to match cells.
Since I will have four sixteen cell batteries I wonder if it is worth while to sort the cells into matched sets of 16. I'll have 2 spare cells too.
 
Craig goes through an extensive process to match cells.

This is probably true (though I don't know the specifics of his process), but when I refer to Chinese Resellers, I am definitely not referring to Craig. Did you purchase from Craig? Do you know what his process entails?

Since I will have four sixteen cell batteries I wonder if it is worth while to sort the cells into matched sets of 16. I'll have 2 spare cells too.

Probably yes. And good call on the spare cells (y)
 
This is probably true (though I don't know the specifics of his process), but when I refer to Chinese Resellers, I am definitely not referring to Craig. Did you purchase from Craig? Do you know what his process entails?
There is a thread around where Craig talks about running through an automatic testing process that records capacity every 15 seconds while discharging. I assume he uses that data to sort them. The costliest part of that process isn't the time it takes to test them. It is not being able to sell the ones that don't match. Or having to sell the unmatchable ones at a lower price. Or letting them sit around until some come along that match.

If I get my order and the cells are in sequence I will know they are either unmatched or that they already matched and no sorting was necessary.
I will try to verify whether they are matched if it is worth the effort. You seem to think it's not worth the effort. That goes against what a lot of people are saying around here. But I would prefer that you are right. I don't want to waste my time doing something unnecessary.
 
the extreme best practice for applications where matching is very important is tightly matched cells from same factory, batch, date and if possible in cronological order (serial number). At least this is what I learned from Nordkyn and Marinehowto. This is overkill for most of our applications

That sounds like matching is unnecessary for us.
 
There is a thread around where Craig talks about running through an automatic testing process that records capacity every 15 seconds while discharging. I assume he uses that data to sort them. The costliest part of that process isn't the time it takes to test them. It is not being able to sell the ones that don't match. Or having to sell the unmatchable ones at a lower price. Or letting them sit around until some come along that match.

I'll keep an eye out for that thread, thanks.

If I get my order and the cells are in sequence I will know they are either unmatched or that they already matched and no sorting was necessary.
I will try to verify whether they are matched if it is worth the effort. You seem to think it's not worth the effort. That goes against what a lot of people are saying around here. But I would prefer that you are right. I don't want to waste my time doing something unnecessary.

I don't understand what you are saying here.
I think you have misunderstood something I said if you have the impression that I don't find testing or attempts at verification of quality worth the effort, I definitely think testing to the best of your ability is worthwhile, and I definitely think its worthwhile to do your due diligence in choosing a supplier and pushing them to have some process of matching. I definitely would not discourage anyone from testing and doing their due diligence.
What specifically do you believe I'm saying is not worth the effort?

That sounds like matching is unnecessary for us.

That level of matching may be unnecessary for us (going as far as same batch and chronological serial numbers), and I don't think that opinion goes against the majority here, if it did, none of us would be buying from the grey market where getting anywhere near that level of matching is impossible. But well matched cells are worthwhile for any application, and is one of the primary reason I still consider buying full price cells through official channels.

If I were to buy cells through official channels, at retail prices, I would definitely still pursue the highest level of matching possible, but for our application this is less crucial than in some others (like EVs).
 
If I were to buy cells through official channels, at retail prices, I would definitely still pursue the highest level of matching possible,
From the talk about batches and sequential order, it sounds like they must be well matched coming off of the production line.
I bought direct from Deligreen and didn't push for the absolute cheapest price. Everyone has their ways of getting the quality they want.
I am not disappointed often and I buy a lot of stuff.

That level of matching may be unnecessary for us (going as far as same batch and chronological serial numbers), and I don't think that opinion goes against the majority here, if it did, none of us would be buying from the grey market where getting anywhere near that level of matching is impossible. But well matched cells are worthwhile for any application, and is one of the primary reason I still consider buying full price cells through official channels.
It doesn't make sense to use batteries if I pay full price. It is hard to justify cheap cells even if I have no problems.
Do you know of instructions for DIY cell testing for matching capacity? It would be nice if I could use this capacity tester - https://www.aliexpress.com/item/32822564230.html
I don't know if that is enough information to use for matching. I would like to avoid recording every 15 seconds.
 
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