BLS 4x 3.2V 200Ah LiFePO4 - voltage difference between cells

[gehowi]

Also, cooling in between cells should not be an issue in solar storage applications

Hello again,
I started celltests with my datalogger. I also measure temperature at the center of the cell during Charge/Discharge.
The cell lays down flat on a table, a precision digital sensor DS18B20 is taped on the upper center and covered by a 2 cm foam to eliminate ambient temp variations. Room temp is stable at 22° during tests.

I see a rapid temp raise as soon as charging/discharging starts, even I only use 15A. The total raise in temp during an 11h test is 5°C up to 30°C.

In a pack where all cells are fixed together with no space between, this means the cells inside the pack will rise more than cells on the outside.
With much higher currents in 12V packs, the temp may increase higher (to 40°?). Noone measure since all cells are packed together.

So I am still convinced it is better to leave a few mm space between cells since temperature rise affects lifespan (eventually by sticking vertical spacers at the border of the cell, so cells can still be fixed for mobile use).

What is your opinion? Is 30°C ( 5°C raise) normal for a 200Ah cell at a low 15A discharge?
15A X 1.8 mOhm would be 0.4W. Could that make it rise 5°?
What is the max temp a cell should get?


Graph:
Yellow= short cell charging 14A to 3.65V; 5 min Idle; Cell discharging 15A during 11.5h (red line). Temp rise in °C on the right side = purple line
The small decrease in the temp line in the beginning: I took off the foam to see if temp decreased.

 

[Keith_PDX]

Help me understand why you are so insistent that your 200Ah cells are made be ETC even though ETC themselves cannot say they are and, from what I am reading, are stating they are not? I am sure BLS is using multiple factories to source their cells, which is clearly demonstrated by the diversity in their listings.

I see no issues with them drilling and tapping the batteries themselves. Why do you feel this is inferior? The blue wrapping is purely cosmetic and has no impact on performance or structural ability of the cell. I feel like you are using data points to prove to yourself that the cell is inferior rather than being open and objective in your conclusions. The rest of your data is sound.

Here is a picture of my serial number, how would I cross reference this to a factory?

 

[ScoTTyBEEE]

Some places selling these batteries say they're made by CATL

CATL Battery

CATL is always as pioneers of latest lithium technology. the energy density of CATL Battery is as much as 190Wh/kg.CATL Battery, 120AH CATL LiFePO4 Battery, CATL Lithium Battery, Contemporary Amperex Technology Co., Limited

www.evlithium.com

ETS seem to suggest these batteries are fully traceable, so you'd think they'd be on their system regardless.

ETC MES is widely used in advanced IT technology, such as barcode labels, wireless scanning technology, 2D barcode printing and engraved code technology, intelligent integration of automation equipment and in-process initiative foolproof technology and so on. The MES system has both forward and reverse traceability, that is to say the trace from raw material / slurry/ film roll to product SN, or vice versa.

 

[gehowi]

Here is a picture of my serial number, how would I cross reference this to a factory?

Thank you for providing your label/ serial nr. In your label there is no reference to ETC so may be they are manufactured by someone else. Your poles are different from mine too. In that case I can't tell you anything useful about your cells.

My cells all have the name ETC and the type NAH3L0 in the label so I am very sure they should be manufactured by ETC Battery China. Even BLS sent me the datasheets from ETC before I bought. But ETC say they can't trace any of them. They call them fake or not qualified.
Not suspicious??



I did not care the cosmetic of the blue cover before. The first 16 cells had a perfect cover; the next 16 a manual added cover full of bubbles.
Not strange for 2 deliveries in 1.5 month of the same manufacturer and seller?
When ETC told me about the production process where bad cells get out of the process before they get the blue cover and are drilled, then I started thinking.

I do not try to prove myself with my graph. It is the pure result from my tests, very well calibrated. It does not help me to use or publish fake results. I made this logger only to find out why I cannot keep those batteries in balance for more than 10 cycles. The reason is, none of the first 16 have an equal capacity.

Do you think it's acceptable and normal to get 4/16 batteries that are expanded 4mm already when you receive them? And 1 self discharging cell that drops from 3.3 V to 2.85V in one night without load?

5 bad cells on 16 that's not just bad luck, that is a cheating seller. I asked them before my order to check all cells on voltage very well but they did not. They dumped their old stock to me, hoping they would never hear about it anymore.
I had no other choice than buying more cells because I could not use the first bank at all. The second delivery they did check the resistance and voltage and these are better; still have to check their real capacity. It will take one month.

My tests prove for myself what is wrong. If you don't believe it, no problem. I just hope to save other people the same trouble.
If your cells are ok, that's very good. I hope everyone's cells are good and it just me who has been cheated.
But we don't believe in Santa Claus anymore, do we?

 

[gehowi]

ETS seem to suggest these batteries are fully traceable, so you'd think they'd be on their system regardless.

I am not sure if we talking about the same ETC. My batteries are produced by https://www.etcbattery.com. I think they do not produce something else.

 

[Keith_PDX]

BLS responded my inquiry. My cells are made by Higee. http://www.ihigee.com/

Higee responded quickly, cells were manufactured August 2019, as advertised by BLS. They also stated most cells are shipping without being drilling as the oem packager prefers to do it to their own specifications.

 

[gehowi]

They also stated most cells are shipping without being drilling as the oem packager prefers to do it to their own specifications.

Thank you to check this and give reliable information. I can believe that some manufacturers produce OEM cells without drilling.

But not in my case because BLS says that M4 is the ETC standard; ETC tells it is M6.
So who is lying here, BLS or the manufacturer?

BLS chat
see marked red text

现在的电池是M4的螺丝，它是工厂制造的标准，没有加大到M6
Now the battery is M4 screw, it is the standard manufactured by the factory, not increased to M6
Alibaba Translation
That's pity because the Hex M6 with nut was perfect
Read
So it is another battery type?
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当然，同一个工厂生产的
Of course, the same factory produced
Alibaba Translation
原厂就是M4，不加工的更好
The original factory is M4, not processed better
Alibaba Translation
M4的是全新工厂的电池，没有加工，没有循环，你买的那些，就是有加工成M6,
M4 is the battery of the new factory, there is no processing, no circulation, the ones you bought are processed into M6,

They put a picture of their drilling machine. That would mean they process an original M4 pole to M6 themselves.
But ETC does not provide M4. Then it must be an OEM undrilled pole where BLS drills M4/M6.
BLS does not buy OEM with undrilled poles from ETC because ETC says BLS is just a trader they don't know.


And again:

m6的电池不是库存电池，你可以记录二维码上的编号，然后和m4的一起发送给ETC工厂，他们可以查询m4和m6是不是同一个批次
The battery of m6 is not in stock. You can record the number on the QR code and send it to ETC factory together with M4. they can check whether m4 and m6 are in the same batch.
Alibaba Translation
M6的是我们拿出来以后二次加工的，因为很多客户都希望得到M6的，我说的足够清楚了吗？
M6 is processed twice after we take it out, because many customers hope to get M6. am I clear enough?
Alibaba Translation
你的M6的电池就是库存电池的说法是不正确的，因为ETC从来就没有生产过M6的电池，也没有M6电池停产的说法。
The statement that your M6 battery is the storage battery is incorrect, because ETC has never produced M6 battery, and there is no statement that M6 battery is discontinued.
Alibaba Translation
22/10/2019 10:13

Answer from ETC:



The offer from ETC directly to me on 23 oct 2019 ; only M6 available:




BLS:
No answer anymore when I said the plastic cover is manual work
15/08/2019 12:19
蓝色的膜应该是运输过程中，一直变化的温度导致的，我们发货的时候没有明显的气泡
The blue film should be caused by the changing temperature during transportation, and there is no obvious bubble when we ship it.
Alibaba Translation
15/08/2019 15:27
First batteries had no bubbles; second batteries still have now.
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You will see on the next pictures that the blue cover is manual work. Just like cut with a scissor.
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Bank 1
Read
Read
Straight cut, no bubbles
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Bank 2
Read
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zig zag
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But I don't care the plastic
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15/08/2019 15:41

 

[Steve_S]

OK, so bottom line is, BLS is an aftermarket VAR (Value Added Reseller ?) who buy's up seconds and flogs them. ETC is an OEM and BLS flogged their seconds or worse... Odds are that ETC is not the only one they are buying seconds from.

Looked at the ETC Website in English but they do not list products as such.
Is there any way to buy ETC Cells from ETC on DHGate, Aliexpress or ?? Amazon/Ebay ??
I wonder if they would have a listing of "Authorized Resellers" on any of these sites ?

 

[gehowi]

Is there any way to buy ETC Cells from ETC

If BLS sells unqualified batteries they buy all over China then they have only limited series from every brand. That's why they can hardly deliver the same cells. 1 year warranty? How?

I don't know if the original cells from ETC are really good. Mine are not but what happened with these...

I got an offer from a company that is suggested by ETC manufacturer. They seems to work very professional but they are 30% more expensive.
However I think it's better to pay 30% more for a new battery with 5 y warranty and 30% more real capacity. For such a large and risky investment I think an official channel is recommended.

At least it is a company with a real address; contact persons with real names; telephone numbers; registered site names and company email addresses.

ECO Power Group
Tel: +86 (0)25 8773 6807
Phone/Wechat: +86-137 9327 3426
SKype: benson.036
Email: benson@ecopowerpack.com
13793273426@163.com

Eco Power Group│WirelessValley │No.9 East Mozhou Road│China
Nanjing Headquarter │ Wuhu factory │ Switzerland Branch │Australia Branch
Website │
www.ecopowerpack.com
www.etcbattery.com

Wuhu ETC Battery Limited - LITHIUM BATTERY, BATTERY BACK

Wuhu ETC Battery Limited, Experts in Manufacturing and Exporting LITHIUM BATTERY, BATTERY BACK and 451 more Products. A Verified CN Gold Supplier on Alibaba.com.

etcbattery.en.alibaba.com

What do we know about BLS Battery ? No company information; no addresses, nicknames or no name for the contact persons and
email address: "深圳宝力晟" <1056171400@qq.com>

Finally I copy a statement in their product advertisement :



Very professional and customer friendly!
And no, I can tell you they did not "slove" my problem. I did not open a dispute and I 100% regret it .

 

[Keith_PDX]

Here is who I communicated with. Very quick to reply, very friendly and professional.

Deputy Director of Sales
陈峥嵘 Jason Chen
深圳市宝力晟电池有限公司
BLS Battery Industries Limited
Tel: (86) (755) 29498929 FAX:61624107
Mob/WhatAPP:+8613802554918
E-mail:jason@blsbattery.com

 

[SolarRat]

I'm afraid gehowi's experience is going to be very common from a lot of these resellers. Buyer beware. Thanks @gehowi for doing these tests and documenting everything so well.

 

[gehowi]

Here is who I communicated with. Very quick to reply, very friendly and professional.

I appreciate you share the company information. It's important for readers to hear pro and contra.

If BLS would have delivered good batteries to me, I would certainly recommend BLS to everyone, just like you. And I would never have started any investigation.
If they would have replaced the new expanded cells without discussion I would be very forgiving and tell it to nobody.
Everyone knows that expanded cells are always old / degraded but they don't want to accept that.

I negotiate 3 months already with this kind of arguing, denying and strange logic:

So pls wait for my testresults. Then we can judge.
Read
如果你说我们的M6的库存电池，我就很难帮你解决，因为我如果帮你解决问题，意味着我们承认M6是库存电池，但实际上他们并不是
If you say our M6 inventory batteries, I can hardly help you solve it, because if I help you solve the problem, it means that we admit that M6 is inventory batteries, but in fact they are not
Alibaba Translation
I just say that the first 16 batteries were not ok. I did not even connect one and 4 were seriously expanded.
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你似乎坚持你自己的判断和ETC给你的回复，但我认为他们轻易的做出判断也是不负责任的
You seem to insist on your own judgment and the reply from ETC, but I think it is irresponsible for them to make a judgment easily.
Alibaba Translation
One had large Self discharge.
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老实说，你反馈太迟了，
Honestly, your feedback is too late,
Alibaba Translation
Why is it too late? I mention those problems already from the first week
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这个过程很长，你也应该站在我们公司的角度思考一下，
This process is very long. You should also think about it from the perspective of our company,
Alibaba Translation


Quick response? Yes, that's ok. Friendly? Yes, if there is no problem. Professional?

 

[gehowi]

From your conversation, BLS did not refuse to solve the problem for you. They have been actively communicating with you. This shows that BLS is more reliable than most Chinese suppliers. The situation in China is more complex. What you see and hear is not necessarily true. Believe me

Compared to many other Chinese sellers, BLS is certainly different and more communicative.

Coincidentally, I even got a spontaneous email yesterday to ask how my test were evolving. If something is good, I tell it as well.

I am double testing every cell and still got no more than 174Ah where it should be 200Ah. But I have a lot more cells to test.
If BLS will finally solve the problem (have cells with equal and sufficient capacity) I will write it here.

 

[Aussiecroc]

I was talking to Jason today on email. He has been answering very quickly. The price of the 190 a/h blueys pack jumped in Australian dollars from $879 to $931 overnight. He asked me to take a photo of the page. Hoping for a quick reply like all the other letters but waited all day. Rightly or wrongly I said a number of his customers are reviewing his practices and the quality of the cells he sends to people. I did not mention this forum.

He keeps writing saying this more than once in the past few days.

The quality is guaranteed. We have sold a lot of batteries. You can use the balancer. You can buy them at ease. Don't worry.

Australia includes taxes and fees. They are delivered to the door. Thank you

I wonder why they need the balancer if they are sending them in lots of four. I wont be jumping in fast at this rate. I will let you know what happens. I checked the Aussie dollar and it hasn't changed much.

 

[Johan]

What is your opinion? Is 30°C ( 5°C raise) normal for a 200Ah cell at a low 15A discharge?
15A X 1.8 mOhm would be 0.4W. Could that make it rise 5°?
What is the max temp a cell should get?

I am glad you asked, I have been kind of waiting for that . An increase of 5°C seems way too high according to this thermal model on this forum. The model, which tries to be conservative, predicts only a 1.7°C increase, assuming:

• perfectly thermally insulated cell (no heat can escape),
• 200Ah capacity,
• 15A (dis)charge,
• 0.5mΩ internal DC resistance (>impedance because of this),
• 4kg cell mass, and
• 800J/kg/K specific heat.

So for the BLS cell, without perfect insulation, with table conduction, natural air convection and radiation heat transfer, I would expect a lower increase, maybe even below 1°C. This could suggest that the cell has a relatively high internal resistance.

 

[gehowi]

An increase of 5°C seems way too high according to this thermal model

Thank you for this information.
I added a full discharge graph from my celltester where you can see temperature related to the current. (Cell V is on the right side of the graph)
The cell capacity test is 184Ah (should be 200A)
The cell lays down on a table and is covered with 1cm foam on top and a small book on it. The sides are still open to air and allow some cooling. With full isolation the celltemp would be even higher. After discharge there is 10min pause and after initial recharge, there is a 15h pause. The ambient room temp raise 2-3 degree during the day.
My YAOREA tester shows me an internal resistance around 10 mOhm after a 50Ah recharge (lowest measure). I am not sure about the reliability of this Chinese tester but the high internal resistance could explain the large temp raise.

What is your conclusion about this cell and it's temperature (light green line)?

 

[Johan]

The cell capacity test is 184Ah (should be 200A)
I am not sure about the reliability of this Chinese tester but the high internal resistance could explain the large temp raise.

What is your conclusion about this cell and it's temperature (light green line)?

That internal resistance is an order of magnitude (factor 10) higher than expected according of specsheets of similar cells. No wonder that the temperature rises like it does. I would expect an even higher rise in the center of the cell. Coarsely using 10mΩ (I assume this is the 1 kHz AC impedance) as an estimation of the DC internal resistance, the theoretical heat loss after 10.5h discharge is 7.4Ah. But it could theoretically easily be double that (double the resistance: 20mΩ, so double the loss: 14.8Ah), decreasing capacity from 200Ah to 185Ah. Or more. Or less. Also in the middle of the discharge the temperature is almost constant, so based on that near-equilibrium, an estimation can be made of the rate of heat loss from cell to environment: approx. 5 Watt at 20mΩ. if you would put this cell in a battery, (what I say now is highly speculative: ) it would overheat and have a very short cycle life, and it would heat up the cells next to it too, not good.

So why is the internal resistance high? Jeff Dahn sais (link) that it can be caused (amongst others) by parasitic reactions and that it gets worse at 50-60°C for LFP cells.

 

[erik.calco]

My first thought when I read the OP was internal resist. Then I noticed there are 3 pages, but looks like that is the conclusion on page 3.

@cyanogenic For people dropping in, if you reached a conclusion can you update OP with an EDIT and note how you reached conclusion and any tools that can be used to diagnose?

The first thing I do with a pack of 18650s is test their capacity and internal resistance, and log in spreadsheet. The higher internal resistances will not end up in a pack. I just bought a Jehu recommended charger that does all that. But, I haven't tried on larger cells. I'm suspect there is a Drok that does all that.

 

[Rui Ponte]

So... I was all in on buying 64 of these 150Ah 3.2v cells from BLS.
$5776,6 (Black Friday deal) for a brand new 30,7kWh 48V LiFePo4 battery (without BMS) sounded like a very sweet deal.

But after having reading this topic and gehowi's evidence (thanks for the investigation!!).... I would be insane to follow through with the purchase, right?
BLS informed me that these batteries have the (infamous?!) M6 bolts.

I'm making my math at €/kWh. Therefore, cycle life is key and if by any chance these are cells that didn't qualify for OEM manufacturers..... it's impossible to factor in a good estimate for the cycle life.

What's interesting is that the guys at BLS receive REALLY good feedback at Aliexpress.
They also have a super interesting shipping method where, transport and all customs taxes and duties are included in the price. That way, you know exactly what your final price will be. Not that usual when buying from Aliexpress.

 

[erik.calco]

Now that I read this post on B cells that has a really good must watch video for anyone buying cells online or from China, with an internal short increasing the risk of explosion, and it being detectable by measuring self-discharge, you may want to do a self-discharge test on all your sells, @cyanogenic .

To do that, you'd want to charge them up to the same voltage. Then just let them sit not connected to each other or anything for 28 days. Then measure again. If this cell is lower, then it has a higher rate of self-discharge, indicating a possible internal short.

I don't know how much of a difference is significant, though. I just derived it from the video in that post, and it didn't tell you how to run the test. But, at least you can compare it to the other 3 cells.

As we go forward, we need to define our specifications up-front and testing processes for ordering cells from China, especially if we begin to do group buys. Not sure how, yet. But, w/o validating that they sent the specs we were expecting (and ideally asked for up-front if that is an option in the ordering process), we're going to get bad eggs in a batch. Obviously, we have limited means, and testing will add time. This is our only hope if we want to buy cells directly from China, though, rather than go through a branded seller who presumably would do this testing before selling on our markets.