How to tell if EVE cells are A or B, and does it really matter?

[apctjb]

If you want a excellent LiFePO4 prysmatic cell buy an 'automotive grade' cell with manufacturers test data sheet that traces back to cell QR code

Very true; but what if you are after the lowest system $/kwhr storage delivered over the useful life of the battery. Is that achieved by purchasing authentic automotive grade A at a premium or something else sold at a discount? Has anyone done the analysis?

 

[apctjb]

Okay, quick comparison of cost of $/kwhr of Grade A vs Grade B.

Assumptions;
Grade A $200/cell, 6000 cycles, 280ah/896whr storage. $/kwhr over lifetime of battery=$.037, call it 4 cents/kwhr.
Grade B $110/cell, unknow cycle life, Unknow capacity.

First lets look at cycles.

You need to get more than 3300 cycles from a 6000 rated cell to achieve a lower $/kwhr cost. If you get that you are money ahead.

Next capacity.

You need to get more than 154 Ahr out of the 280ah cell to achieve a lower $/kwhr.

What is best depends on individual preference and circumstances, draw your own conclusions.

 

[SolaroSsaurius]

My 2 cents...
I think that you are not taking into account that Grade B are more prone to runaway, hence rendering the pack unusable/ less usable / reliable

 

[apctjb]

I think that you are not taking into account that Grade B are more prone to runaway, hence rendering the pack unusable/ less usable / reliable

Yes, this is a simple economic analysis which does not attempt to factor in potential cost impacts of differences in reliability it there are any. Frankly not sure how to quantify these cost as for some a runaway cell has no cost impact, others it will.

 

[RandyP]

I think you have to thnk of a non-automotive grade cell (a failed cell) as a package deal. Too many unknowns to expect much from a battery made of these reject cells.

 

[apctjb]

Too many unknowns to expect much from a battery made of these reject cells.

Unknows like less capacity and cycle life. What other unknows are you referring to?

 

[jimjoe]

Unknows like less capacity and cycle life. What other unknows are you referring to?

For instance, such unknowns:

B cells are the failed to pass certification. Why they failed? There are always some mismanufactured items on production lines. Sometimes you have mismanufactured items, that are still "usable" for some purposes. Like you can see on the video, there is a different reactivity of the cells on current draw and how they recover. In the "storage" use, when you have fairly low cycling (50-150 a year) and low currents, quite much time pass before a mismanufactured B grade cell dies - people rarerly, in this type of use, get to the numbers of cycles and currents the cells are supposed to survive/last - the mismanufactured B grade cells are seen to be fit for purpose of energy storage (especially DIY). Different situation is with electric vehicles - where cycling can be frequent (people driving cars as part of work) and where also stress on the batteries is much higher - high currents going in and out of the cells in the frequent cycles.

The big problem with mismanufactured cells is that there is no one reason why the cells fail pass tests. They simply are not meeting expectation of a final product and are considered waste. The waste is bought by resellers like Docan (who are liers), selected and sold to us as a "A grade" cells. Only after such malpractice manufacturers see damage these resellers make to them and start marking cells - like EVE did with the "B" mark. Hope this marking by manufacturer will be a standard, so it will be harder for Docan and others scam us.

Like this video, because it shows how different the 4, "B grade" cells can be - one of them nicely keeps voltage despite high current draw while the other barely hanging on... You simply do not now what you get and one cell can cause lots of pain in your system. If you are a sole DIY and can manage failure of system - which most of DIYers can in their personal use then you'll likely live. If you are building system for someone or take on yourself risk of guarantee or need a solution you want make and forget about, then use of B cells is a risk to your activity.

 

[houseofancients]

For instance, such unknowns:

B cells are the failed to pass certification. Why they failed? There are always some mismanufactured items on production lines. Sometimes you have mismanufactured items, that are still "usable" for some purposes. Like you can see on the video, there is a different reactivity of the cells on current draw and how they recover. In the "storage" use, when you have fairly low cycling (50-150 a year) and low currents, quite much time pass before a mismanufactured B grade cell dies - people rarerly, in this type of use, get to the numbers of cycles and currents the cells are supposed to survive/last - the mismanufactured B grade cells are seen to be fit for purpose of energy storage (especially DIY). Different situation is with electric vehicles - where cycling can be frequent (people driving cars as part of work) and where also stress on the batteries is much higher - high currents going in and out of the cells in the frequent cycles.

The big problem with mismanufactured cells is that there is no one reason why the cells fail pass tests. They simply are not meeting expectation of a final product and are considered waste. The waste is bought by resellers like Docan (who are liers), selected and sold to us as a "A grade" cells. Only after such malpractice manufacturers see damage these resellers make to them and start marking cells - like EVE did with the "B" mark. Hope this marking by manufacturer will be a standard, so it will be harder for Docan and others scam us.

Like this video, because it shows how different the 4, "B grade" cells can be - one of them nicely keeps voltage despite high current draw while the other barely hanging on... You simply do not now what you get and one cell can cause lots of pain in your system. If you are a sole DIY and can manage failure of system - which most of DIYers can in their personal use then you'll likely live. If you are building system for someone or take on yourself risk of guarantee or need a solution you want make and forget about, then use of B cells is a risk to your activity.

before using , believing or using anything touched by skf, i would do a little forum search...

they are not know for being anywhere ethical, pleasant or well versed in testing
This series was made as a response to a forum members show and tell of their product

 

[Theo74]

The market of LifePO4 cells is overloaded and chaotic at the moment, so there is a chance that some 'cowboys' in the battery market want to use this situation for their own profit. Al lot of Chinese middle men presenting their self as manufacturer or EVE preferred supplier, only selling A quality.

On top of (EVE) grade A of grade B cells, is see more Chinese 'suppliers' use the term "grade A-" (A minus). This is explained as grade A cells which are stored for a longer time, and there fore can not be sold as grade A cells. Often with the added explanation that those cells have no QR code.

EVE does not sell any cell without QR code, regardless their grade. And only grade A or grade B, with a B in the QR code then. grade A- is a hoax.

 

[jimjoe]

before using , believing or using anything touched by skf, i would do a little forum search...

they are not know for being anywhere ethical, pleasant or well versed in testing
This series was made as a response to a forum members show and tell of their product

I have no opinion about SKF. The video they made is quite good in that it shows different physical behaviour of different cells in a set. What they SFK presented is quite similar to the following method of measuring health of a LiFePo4 cells - https://www.sciencedirect.com/science/article/pii/S0026271418305687 (If you look for a credible material on the subject)

 

[apctjb]

For what its worth (not much) I tested some of B cells I recently purchased. In terms of capacity I got what I paid for. Time will tell regarding cycles.

Capacity Test; Charge to 3.65; discharge 40A CC to 2.5V (25% sample; 4 cells out of 16 tested)

	Ahrs	Whrs
Cell 1	285.8	922.31
Cell 2	279.5	899.88
Cell 3	284.2	914.94
Cell 4	281.1	907.55

Voltage Slump; 40A-2 minutes. (50% sample; 8 cells out of 16 tested)

	Cell 1	Cell 2	Cell 3	Cell 4	Cell 5	Cell 6	Cell 7	Cell 8
Total Sag (V)	0.059	0.065	0.059	0.058	0.067	0.058	0.058	0.058
1 sec Sag (V)	0.021	0.025	0.021	0.021	0.024	0.021	0.021	0.02
1 Sec mV/A	0.525	0.625	0.525	0.525	0.6	0.525	0.525	0.5

 

[Alkaline]

For what its worth (not much) I tested some of B cells I recently purchased. In terms of capacity I got what I paid for. Time will tell regarding cycles.

Capacity Test; Charge to 3.65; discharge 40A CC to 2.5V (25% sample; 4 cells out of 16 tested)

	Ahrs	Whrs
Cell 1	285.8	922.31
Cell 2	279.5	899.88
Cell 3	284.2	914.94
Cell 4	281.1	907.55

Voltage Slump; 40A-2 minutes. (50% sample; 8 cells out of 16 tested)

	Cell 1	Cell 2	Cell 3	Cell 4	Cell 5	Cell 6	Cell 7	Cell 8
Total Sag (V)	0.059	0.065	0.059	0.058	0.067	0.058	0.058	0.058
1 sec Sag (V)	0.021	0.025	0.021	0.021	0.024	0.021	0.021	0.02
1 Sec mV/A	0.525	0.625	0.525	0.525	0.6	0.525	0.525	0.5

These actually look very good you got a good deal I would say.

 

[perryfranz]

like Docan (who are liers)

those are hard words to say, did you had some issue with them? Just curiosity because I have to place an order for 8 EVE280 from EU and I tried Docan and Dongguan Lightning... so I'm quite interested on this and reading this is quite shocking after tons of good review of them here.

 

[jimjoe]

those are hard words to say, did you had some issue with them? Just curiosity because I have to place an order for 8 EVE280 from EU and I tried Docan and Dongguan Lightning... so I'm quite interested on this and reading this is quite shocking after tons of good review of them here.

Yes, unfortunately. In March, I made a purchase of 16 grade "A" cells, these cells were to come from EVE and be the famous now LF280K-280Ah. Before I made decision to buy, I asked many questions. I received pristine report of capacity test, showing cells with excellent parameters - all tested cells got about 290 Ah, 0.15mOhm internal resistance etc. (like a grade A, never or once/two times cycled you could expect). I got a picture of perfectly aligned cells that do not have distances between (my shipment). Everything excellent - like a grade A cells should have. When shipment finally arrived... cells were swollen with 5+ mm distance between them - no way to replicate presented picture of cells I received from Docan's representative. None of received cells had internal resistance that was on the report - all higher (but within specification of EVE LF280K range (so ok-ish)). The test report I was presented was from summer 2021 but the cells I received were manufactured in December 2021/January 2022 - no way the report was about the batch I received. In short, I was lied by Docan and received worse grade product, like many of us - I did not anticipate buy. If I did not ask questions and was answered in accordance to advertisement, clearly being shown that the cells I am buying are A grade cells - I could not say I was lied by Docan. To me it is a bunch of scumbags and I do not want have business with them. Honesty is key in business, especially when there's no warranty or the warranty is not possible to execute (cost of return to China may be close or exceed cost of cells).

Only today we know what was the situation with "grade A" LF280K-280Ah cells from EVE . It is known now that only EVE was selling grade A cells , for 2.5 times higher price than Docan and other sellers. The cells that were failing grade A certification, were sold to the other sellers that were re-selling the cells as grade A cells. Obviously, EVE in the situation was loosing face with poor quality, "grade A", cells flooding markets so just in the middle of the year started print "B" on QR code, on the second grade cells. Now the same cells are available on the market, in the price Docan was selling them in March, but have explicitly printed "B" on QR code - as they should have.

My personal experience with Docan is awful - in that sense that they are liers. You'll have a good connection, customer service, responsiveness but you will be presented reality of your purchase that won't exist. I also read good about Docan and was keen pay more to buy with them - that was mistake I won't make again (to me Docan is not worth making business with).

If you'll decide buy with Docan, ask for QR codes of the EVE280 cells. If they won't have B on them but you can decode them and see they were manufactured somewhere in December 2021/January 2022 (not sure about earlier/later manufacturing dates) - likely you'll get grade B cells from the pack I got, which weren't yet marked as B by EVE - EVE started marking the B somewhere at the end of spring this year.


Recenty, I saw Gobel Power describing little of this on their webpage with EVE LF280K cells -> https://www.gobelpower.com/eve-32v-280ah-rechargeable-lifepo4-battery-cell_p6.html . They also present how the "B" is printed on QR code by EVE now.

 

[apctjb]

The whole Grade A & B doesn't make much sense from a marketing perspective. So much better if EVE would create different SKU's /models depending on test results. Those suitable for EV are labeled as such with the test standard they meet, those suitable for storage with a different label and different standard. A lot less drama and customers can choose the price/test standard that meets their requirements.

Just because a cell does not pass the EV standard does not mean it is not suitable for a different application and certainly much better to have the product have a useful life than go to a landfill.

In the PV industry we started doing this decades ago. If a cell did not pass its flash test for one standard, it was binned accordingly and sold for a different (lower) standard. That's why you see modules from the same manufacturer with the same dimensions available as different models; for example 350W, 325W, 300W, 275W. They are not using different cells, just the rejects from the highest standard. I don't hear people call those cells manufacturing defects, yet they failed to meet the most rigorous test standard.

 

[jimjoe]

The whole Grade A & B doesn't make much sense from a marketing perspective. So much better if EVE would create different SKU's /models depending on test results. Those suitable for EV are labeled as such with the test standard they meet, those suitable for storage with a different label and different standard. A lot less drama and customers can choose the price/test standard that meets their requirements.

Just because a cell does not pass the EV standard does not mean it is not suitable for a different application and certainly much better to have the product have a useful life than go to a landfill.

In the PV industry we started doing this decades ago. If a cell did not pass its flash test for one standard, it was binned accordingly and sold for a different (lower) standard. That's why you see modules from the same manufacturer with the same dimensions available as different models; for example 350W, 325W, 300W, 275W. There not using different cells, just the rejects from the highest standard. I don't hear people call those cells manufacturing defects, yet they failed to meet the most rigorous test standard.

Yes, I think this is what starts happen. Grade A/B are being presented by some re-sellers, like the Globe Power, as ESS or EV grades. It would be perfect if manufacturer was deciding on the purpose a cell can serve - they do the research on products they build and know best what types of failures the mismanufactured items have so they are best to properly group the not meeting EV standards cells. Why they do not do this? It may be that there is such a variation in parameters of mismanufactured cells that is is not worth doing and maybe it is linked to fairly low of failures when compared to scale of production. If there isn't such a variation, it could be a good business as they might create a variation of cells for different purposes, with different specifications. Right now all we have is specification of an A grade cell the manufacturers make but being sold items that do not meet the specifications we got something else - unspecified by manufacturer. I am not referring to EV grade certification but the official specifications manufacturers prepare for their cells. Receiving swollen batteries - they do not meet specified dimensions, often capacity is lower, impedance is higher and number of cycles such cells can survive is known to be lower.

 

[Steve_S]

Grade B or Bulk Cells.
You buy 16 cells which all work and are close in IR (Internal Resistance) "generally" @ 3.000, 3.100, 3.200 & 3.400. They test out and there is no more than 5AH capacity difference YOUR GOOD !

Buy another 16 and two have a higher IR and say 10AH differential, that pack will be limited by the lowest common denominator which will be a runner that triggers either HVD or LVD by the BMS.

To make Grade-A the cells MUST match IR at all voltage test points under Charge & Discharge within the acceptable "Working Voltage Range" which is 3.000-3.400. (this is where the "real" AmpHours comes from) Most companies will actually do extended tests to 2.900-3.500. They do not test the "Allowable Voltage Range" which is 2.500-3.650 which is the safe margins for the cells without causing harm.

As for Battery Cell Reports, some stores do their own with whatever gear they have, is it done properly or not is unknown. Some only use handheld device like a YR1035+ https://www.aliexpress.com/item/32991434414.html? I happen to have one of these and it's fine for verifying the cells for IR. FACTORY Reports will ALWAYS Show the QR Data / Serial Number along with the test results.

My #1 Vendor is Luyuan and everyone who deals with Amy get's exactly what they order and with the EVE Factory Test Report
This RPT is from my last batch of 105AH Grade-A (sorry it's truncated)

Luyuan Tech :
Matched & Batched A Cells are FACTORY tested @ EVE as runs through the batches produced.
This is the TEST Report received From EVE with the full data, Translated to English where necessary for your convenience.

"OCV1" refers to the voltage of the cell (unit: V), which is the initial voltage of the cell tested by the OCV tester after eliminating the "polarization" of the finished cell;

"R1" refers to the resistance of the cell (unit: mΩ), which is the internal resistance (AC internal resistance) tested by the OCV tester after eliminating the "polarization" of the finished cell;

OCV3" refers to the voltage of the cell (unit: V), which is the initial voltage of the cell tested by the OCV tester after the finished cell sits some time at room temperature;

"R3" refers to the resistance of the cell (unit: mΩ), which is the internal resistance (AC internal resistance) tested by the OCV tester after the finished cell sits some time at room temperature

 

[toms]

Very true; but what if you are after the lowest system $/kwhr storage delivered over the useful life of the battery. Is that achieved by purchasing authentic automotive grade A at a premium or something else sold at a discount? Has anyone done the analysis?

I’m in the process of doing this analysis - i feel it will take at least another decade to complete.

Anyone that tells you otherwise is demonstrably guessing.

 

[perryfranz]

with the EVE Factory Test Report

So, one of the things that we can do to find out if (for any interest) we ant a GradeA cell is ask the test report, good to know.

In my case i'm building a small 8s of LF280k but i'm not gonna cry out as a baby if i do not get out exactly 7.168kWh because it's my first battery DIY and I want to make in practise all the theory I learned in the past two years of reading/watching everithing possible about batteries and solar. But unfortunatly I have to buy from EU warehouse and only a few shops have that, so Grade A or Grade B I have to deal with the famous 3 shops if I want to save some € instead of buing server rack batteries.
Maybe for my second battery and after have gained experience on this one I can become demanding on grade A cell, but based on review probably I can trust Dongguan Lightning or Docan, knowing that probably they are grade B... but for 8pcs circa 1200$ with duties and door to door from Germany... maybe they are not.

 

[jimjoe]

So, one of the things that we can do to find out if (for any interest) we ant a GradeA cell is ask the test report, good to know.

In my case i'm building a small 8s of LF280k but i'm not gonna cry out as a baby if i do not get out exactly 7.168kWh because it's my first battery DIY and I want to make in practise all the theory I learned in the past two years of reading/watching everithing possible about batteries and solar. But unfortunatly I have to buy from EU warehouse and only a few shops have that, so Grade A or Grade B I have to deal with the famous 3 shops if I want to save some € instead of buing server rack batteries.
Maybe for my second battery and after have gained experience on this one I can become demanding on grade A cell, but based on review probably I can trust Dongguan Lightning or Docan, knowing that probably they are grade B... but for 8pcs circa 1200$ with duties and door to door from Germany... maybe they are not.

It is very important to be aware what you can expect and good to see you are aware of the situation on the market and do not expect grade A LF280K for 150 USD a piece from an EU warehouse! Whichever seller you choose, I would advice you to get from the seller as much information and assurance as you can - picture of QR codes, report of capacity, get guarantee of capacity or be told the capacity is not guaranteed etc. The more you get assurance and information upfront, the better. Once you'll have your deal done - let us know your experience.

It is very important to understand what is purpose of building the battery - if you're building a battery bank for yourself, for a set of PV solar panels then the B grade batteries may not be bad (unless you'll have some really bad experience getting the worst waste). Situation is different if you want use such battery as a part of project related to conversion of a gasoline car to an EV car (for instance). You should consider what you need in context of the project you have - if you foresee to stress the battery and looking for reliability, the better quality you want. If you're building battery bank for yourself and to use in a summer house - don't see need buy A grade, B from an honest reseller (who'll make basic assurance checks) should do fine. If you plan open EV conversion garage and offer modification of gasoline cars for other... no B can be accepted.

 

[Steve_S]

So, one of the things that we can do to find out if (for any interest) we ant a GradeA cell is ask the test report, good to know.

In my case i'm building a small 8s of LF280k but i'm not gonna cry out as a baby if i do not get out exactly 7.168kWh because it's my first battery DIY and I want to make in practise all the theory I learned in the past two years of reading/watching everithing possible about batteries and solar. But unfortunatly I have to buy from EU warehouse and only a few shops have that, so Grade A or Grade B I have to deal with the famous 3 shops if I want to save some € instead of buing server rack batteries.
Maybe for my second battery and after have gained experience on this one I can become demanding on grade A cell, but based on review probably I can trust Dongguan Lightning or Docan, knowing that probably they are grade B... but for 8pcs circa 1200$ with duties and door to door from Germany... maybe they are not.

I very highly recommend Luyuan Tech, they are a Known Good Reputable vendor and they buy ONLY from Manufacturer and provide the Manufacturer's Test Report. Yes the Grade A cost a bit more but you get exactly what you are paying for,

Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery

Shenzhen Luyuan Technology Co., Ltd., Experts in Manufacturing and Exporting Lifepo4 battery, LTO battery and 148 more Products.

szluyuan.en.alibaba.com

Also download THIS Resource about assembly & much more... Lot of info that will help you on your journey. It is also included with the batteries shipped by them.

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

diysolarforum.com

 

[jimjoe]

I very highly recommend Luyuan Tech, they are a Known Good Reputable vendor and they buy ONLY from Manufacturer and provide the Manufacturer's Test Report. Yes the Grade A cost a bit more but you get exactly what you are paying for,

Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery

Shenzhen Luyuan Technology Co., Ltd., Experts in Manufacturing and Exporting Lifepo4 battery, LTO battery and 148 more Products.

szluyuan.en.alibaba.com

Also download THIS Resource about assembly & much more... Lot of info that will help you on your journey. It is also included with the batteries shipped by them.

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

diysolarforum.com

Does Luyuan have warehouse in the EU? Perryfranz pointed he must buy from a vendor who has a warehouse in the EU.

 

[jimjoe]

To cut bullshit, EVE sells LF280K for $ 250 a piece. Whatever offers you'll see about grade A batteries bought from EVE and being sold for $ 150 - think twice about how they make money selling "the same", manufacturers, cells for 60% of manufacturer's price?

 

[apctjb]

Yup, no free lunch. If you are not paying +$200 USD per cell then regardless of the marketing claims you are unlikely getting EVE automotive grade cells. I just received 16 non automotive cells which I tested and have +280AH capacity and low resistance. Time will tell if I get the same cycle life but doing the math for my application if I get more than 4000 cycles I will be happy not to have spent $200/cell. Everyone needs to do the math based on their own situation.

 

[jimjoe]

I very highly recommend Luyuan Tech, they are a Known Good Reputable vendor and they buy ONLY from Manufacturer and provide the Manufacturer's Test Report. Yes the Grade A cost a bit more but you get exactly what you are paying for,

Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery

Shenzhen Luyuan Technology Co., Ltd., Experts in Manufacturing and Exporting Lifepo4 battery, LTO battery and 148 more Products.

szluyuan.en.alibaba.com

Also download THIS Resource about assembly & much more... Lot of info that will help you on your journey. It is also included with the batteries shipped by them.

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

diysolarforum.com

I find it rude by Luyuan to take your work and brand it with their company name on every page but give you bare "Prepared by Steve_S..." on the bottom of first page - it looks like you work for them. Do you have some form of commercial connection with Luyuan?