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diy solar

Are we all getting GRADE B cells??

Don B. Cilly said:
Chat on Alibaba is probably the best option.
Try https://szluyuan.en.alibaba.com and use Chat Now.
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Click to expand...

Grade A lifepo4 battery, Grade A lifepo4 battery direct from Shenzhen Luyuan Technology Co., Ltd. in CN

Grade A lifepo4 battery from Shenzhen Luyuan Technology Co., Ltd.. Search High Quality Grade A lifepo4 battery Manufacturing and Exporting supplier on Alibaba.com.
szluyuan.en.alibaba.com szluyuan.en.alibaba.com

amy wan ? is this the correct seller to try ? others had good results ? any input on this seller - thanks
 
justgary said:
You paid for testing and providing a spreadsheet to prove that you bought good cells. You call that Grade A.

You didn't pay for testing and a spreadsheet and took your chances on whether they were good. You call that Grade B.

Nothing there says that the cells are any different. Why expect them to test differently?
Click to expand...
I didn't pay for testing. It's what comes with grade A cells directly from Eve
 
koobs said:
I didn't pay for testing. It's what comes with grade A cells directly from Eve
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If the cells came from Eve with a test report then you likely paid for testing.
That is one of the reasons that automotive grade cells cost more.
 
John Frum said:
If the cells came from Eve with a test report then you likely paid for testing.
That is one of the reasons that automotive grade cells cost more.
Click to expand...
Eve tests all its cells. Those that fail testing go into the grade B pile and get auctioned off to resellers. Now thankfully they have a nice big B stamped onto their qr codes to solve the mystery.
 
The other thing that probably happens is they may disqualify whole batchs if the failure rate on the first $n% exceeds some target.
Speculation on my part though.
@koobs do you have evidence that they invest the QA resources on product that has already been disqualified?
 
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John Frum said:
I don't think they completely test the cells that fail.
My guess is they do the cheap and quick tests first and leave the expensive time consuming tests for the ones that have not been previously disqualified.
Click to expand...

When I watched his video where they were applying labels to cells (speaking of SunFunKits) I noticed the test results he was getting and printing labels with contained approximately 1/3 of the measurements I get from EVE (through Amy). I suspect he got sold a lot of grade B cells with the test results, or else it was a defective batch. I don't know, that's just from watching the video, I've never bought any cells from SFK. These are the results that Amy sends (they actually get pulled from EVE who will delete the results after 30-90 days).

304_tests.jpg
 
That is the same exact type of report I got with my supposed grade A 280K matched and batched from Amy Wan. At this point I think EVE is the culprit, I looked very closely at all 3 people that were selling 280K grade A with reports, and they all are testing in the 278ish range. Go look on 18650batterystore, SFK 280K review section, you'll see people saying the same, and this actually matches my own test 278 with the same ZKE style tester...

I also think this is primarily for cells made in November 2021 - January 2022, it also correlates with the on and off again rumor about some big car / bus company who cancelled a big order from EVE after they were not happy with the results. Perhaps these should have all been grade B but was too big of a hit from EVE so they said F it sell as grade A and just lie about it...

Regardless, I have dealt with Amy Wan twice once in 2020 when she was with Xuba and again when she ran her own company. I don't think I will be dealing with her or any other overseas company. I don't care what grade or what a report a vendor has at this point as I don't even believe EVE themselves, its China after all, the corruption goes up to the top.

I would have accepted a discount per cell, but I am now back listed on her Alibaba chat and its been over 6 months, I should have bought this tester back in February (but who knows, maybe back then they would have passed, 2 AH loss after 8 months is possible???) Actually you know, these should have tested to 284, that really would have put my mind at ease...:cautious:

My final advise for anyone is that you should only buy in your local country and make sure you can do a return if un happy. Don't believe any grade A or grade B or whatever else, do you own tests and hold the vendor over a barrel. These youtube reviews and cheerleading forum posts have cost me ?(n)

I will have my basen 280 results on the ZKE ready by the morning.
 
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John Frum said:
@koobs do you have evidence that they invest the QA resources on product that has already been disqualified?
Click to expand...
Nope just speculation from what I've read and seen on videos.
Alkaline said:
My final advice for anyone is that you should only buy in your local country and make sure you can do a return if un happy. Don't believe any grade A or grade B or whatever else, do you own tests and hold the vendor over a barrel.
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Everyone to their own. But from my perspective I'm very happy with both my grade A and grade B cells that I bought from Amy.
A few Ah this way or that doesn't really matter given the size of these banks.
These cells are performing very well and calendar ageing will kill them before cycling.
 
Koobs, My cost per cell was $193 delivered all shipping ali fees, sales tax, I suspect you paid less I bought 8 cells?
 
Yep. Last lot of 16 I bought was $142 usd per cell delivered with duty paid too.
I usually buy 16 or 32 at once. Have assembled 6 banks so far.
 
hrm... well it is what it is I suppose. Other than the AH the luyuan cells are fine. I think in the future I will try 18650batterystore its cheaper than luyuan and they are in the us if I decide to fool with diy again.
 
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koobs said:
These cells are performing very well and calendar ageing will kill them before cycling.
Click to expand...

No - typically dendrite growth puncturing the separator will kill them before 2000cycles.
 
I think puncturing the separator occurs at very high-current EV like levels or so I've been told.

However in sub-c lower-current applications, the dendrites aren't so spiky. BUT, as the cell ages in time, what was once considered "sub-c", gets closer to being EV levels, know what I mean? :)

I found this recent publication to kinda back this up but note that it does not specifically address LFP - all these research studies are usually always done on non-lfp, where the amplitude of the problem might be different:

www.designnews.com

Three Ways That Lithium Dendrites Grow

New research shows that lithium metal crystals grow in three different ways in lithium batteries, depending upon the current level at which charging takes place.
www.designnews.com www.designnews.com

Consider too that Maine Sail, an op and engineer over on the marine forum, has gotten over 10 years of life, and surpassing 2300 cycles with full capacity on his 400ah Winston bank. BUT, that is in a sub-c lower-current application, NOT a motive-power bow-thruster type thing.

So there's hope! I only got about 8 years from my GBS LFP, but I didn't treat it perfectly.
 
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@Substrate thanks for elaborating a bit further. Was a bit scary suddenly to hear an opinion that is someone so convinced that dendrites will destroy lfp cells in 2k cycles.
I've not heard of this before in lfp cells, only the lithium ion type chemistries.

Without more evidence to suggest lfp will have significant dendrite formation and die an early life, I'm happy to stay under a rock and believe my banks will last a crazy long time.

I've already seen how hardy these cells can be and the punishment they can take and still come back to life.
 
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