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

[gehowi]

@Keith_PDX
It's hard to say, your 150Ah models have a complete other pole layout than my 200Ah and may have another chemistry inside.

The bolts and nuts from yours are the same like my "bad/old" batteries but I prefer this stronger bolts because M4 screws are really not strong enough.

When I bought the second set after 1 month, BLS told me they could not deliver M6 anymore. The new types were all M4 "to protect the poles"...
I guess that they switched to M4 because expanding batteries in series, next to each other, may generate large forces on the link sheets and the poles may break with the strong M6 bolts.

Important: If you setup your 8S bank, make sure there is at least 2mm space between every cell to allow for cooling and expanding.
If you can't because the link sheets are too short then enlarge the holes in the sheet.
Don't put your batteries in a firm box or so. Make sure they can "move" freely.

I would advice you to do a capacity test when they are new and unused. Then you have a reference for later.
Charge individual cells to 3.65V and discharge to 2.55V measuring the AH / Wh.
Make sure you never discharge lower than 2.55V. The voltage may drop rapidly at low SOC and your cell will expand/degrade quickly.
After testing you have to charge it back to the same SOC as the other cells before you operate in 8S.

You can use an electronic load to discharge and measure the Ah /WH. Can buy cheap from ALI.
It's also very useful to test solar panels and other batteries.

If you don't have already, I suggest you buy a good DC Amp clamp meter. You will really need it.
I use Bside ACM91, 100A DC+AC + Ohm+freq and voltmeter (from Ali)

 

[ScoTTyBEEE]

@gehowi
From your experience are these the new or old ETC cells?

For what it's worth my 190ah (which are just substandard 200ah) cells look exactly like yours, just taller. I received mine a few days ago.

 

[Sojourner1]

@Keith_PDX

Important: If you setup your 8S bank, make sure there is at least 2mm space between every cell to allow for cooling and expanding.
If you can't because the link sheets are too short then enlarge the holes in the sheet.
Don't put your batteries in a firm box or so. Make sure they can "move" freely.

It seems having your cells moving freely would be a bad thing even slightly. If your cells are bulging it would seem there's an issue going on.
These are GBS batteries that are strapped together and in a box to stop any movement from traveling. Never had an issue with bulging or heat. It's been 3 1/2 years like this and being used everyday.

 

[gehowi]

@Sojourner1
That' a very neat setup! Great work.
Of course batteries for mobile use have to be fixed very well. But in my setup they never move so I prefer space between cells to allow cooling and some expansion.
If your batteries are end of life and bulging you might not be able to get them out of the box anymore..

 

[electric]

It seems having your cells moving freely would be a bad thing even slightly. If your cells are bulging it would seem there's an issue going on.

I agree, cells should be secured mechanically in a block. Your bus bars should not be the point of tension and swelling should not be planned for, as it is certainly a sign of cell degradation. This is why laminated copper links often have a U shape bend in the middle, to allow for expansion/contraction without stressing the bolted terminal.
4mm thread on cells larger than 100AH seems too small, even 6mm seems marginal to me. Definitely need to use lock washers and be careful not to strip the threads. Also what material are those studs made from? You don't want passing high current thru anything other than copper/nickel/aluminum.
Also, cooling in between cells should not be an issue in solar storage applications where typical C rate is fractional. Only if you have C/2 or higher continuous use, then temperature rise becomes a concern.

 

[gehowi]

@electric
Because we have many clouded days here, I bought overcapacity to have autonomy during 2 -3 cloudy days and charge all I can when there is sun. Now I have peaks of 55A charge but I want more solar panels to go to 70-80 Amps or more. I might reach C/2 one day so that's why I think it's safer to have space for cooling.
I have seen so many larger UPS systems before where the batteries were not only bulged but seriously deformed. Not even replaceable because they got stuck in the frame. Of course that was LA..

My 200A cells have 16mm studs in aluminium with straight laminated copper sheets of 2.5 mm bolted with 4mm. So they do not allow expansion.
I do not have contact problems now otherwise I would drill the hole and tap M6. More than M6 would take too much material away from such small pole.

 

[Sojourner1]

Charging 55a into 200ah battery is 0.27c that's nothing. Heat generated is almost nothing.

I'll give examples from actual readings from my cells that I have recorded over the past years of use, you see how they're assembled.
With my solar it will peak at 80a, 70a +/- is the norm.
8/28/18 (during this entire time there is a 9-14 a draw, so this would be added to the solar charging)
08:10_ 79% soc_ -5.3a_ 64f cell temps
11:34_ 78% soc_ +67.4a charging_ 64f cell temps
11:51_ 81% soc_ +69.7a charging _ 64f cell temps
12:40_ 89% soc_ +67.9a charging _ 64f cell temp
13:00_ 92% soc_ +67.2a charging _ 64f cell temp
13:15_ 94% soc_ +12a charging _ 64f cell temp
13:19_ 95% soc_ +64.2a charging_ 64f cell temp
13:35_ 98% soc_ +51.5a charging _ 64f cell temp
14:15_ 99% soc_ +5.7a charging _ 64f cell temp
17:30_ 100% soc_ +0.3+/- _66f cell temps

That was from solar and there is no rise in cell temps in this fractional C charging.

I don't use my generator hardly at all but when I do it will charge at 100ah +/- for 2-3 hours and that might raise the cell temps 10f from start to finish.
This is how I can see what's happening with the system.

 

[gehowi]

Thank you for the data. It's right, I applied a sensor (DS18B20) on each cell and they hardly raise temp in all conditions.
But since I got Chinese problem cells I thought it would be safer to monitor the temperature. May be with aging and higher internal resistance there could be a significant temperature rise, like small end of life cells?

What is the max allowed charge/discharge current for a 200A cell without hurting it? I can see the specs of the manufacturer but I don't trust any of them.

 

[Sojourner1]

You look at enough of specs from different manufacturers of prismatic cells, they actually look the same. Here is the GBS specs which are the same for different AH cells they offer.

 

[electric]

Back in the day a lot of LFP datasheets claimed 3C continuous, but their lab tests were done at room temperature, essentially providing good cooling. They also extrapolated a lot of life cycle data because there was no time to really cycle cells for years prior to marketing. Recently most prismatics pulled back their datasheets to 1C max continuous and 0.5C recommended for long cycle life. So, with healthy 200AH cells, you are safe up to 100A, but if cells are already degraded, you should watch for temp rise at 100A and maybe stay below that level if possible.

 

[TJ Tom]

@gehowi
From your experience are these the new or old ETC cells?

I've contacted etc. they don't have the 150Ah model, so the 150Ah cell should be another factory.

 

[gehowi]

Your test is very professional，Haven't you tested the batteries since you received them? I also bought the M6 battery and contacted the factory. The factory told me that it was produced in 2018, not OLD stock.

When I unpacked the first 16 batteries and put them all in one row, I noticed 4 bulged cells (more than 3mm). In the first week, another cell discharged in one night from 3.2 to 2.8V without load. BLS battery replaced this cell in warranty. But I still cannot keep the M6 batteries in balance.
I bought a second set of 16 cells and 4 spare cells to replace the expanded cells. The blue plastic cover from the new M4 cells was cut manual with scissors! Looks like it has been done in a kindergarten, zig zag and full of air bubbles.. Not one cell the same.

ETC replied my questions (with pictures of the labels) and told me my M6 batteries were "un-qualified", whatever that means. I asked for the production date but until now, ETC does not reply anymore. Typical Chinese, nothing to sell, no reply.
Must say that BLS battery still answers my questions but getting those degraded cells replaced is something else.. Now I just made a single cell capacity tester with datalogger for a full charge/discharge cycle. They will get the graphs for every cell soon.

 

[Altide8]

For what it's worth my 190ah (which are just substandard 200ah) cells look exactly like yours, just taller. I received mine a few days ago.

How are you liking yours? Any tests?

 

[ScoTTyBEEE]

How are you liking yours? Any tests?

Close to 200ah from totally flat to completely full. They go out of balance at the top of the charge but give 190ah useable with only 42mv difference in cells @ 14v

 

[gehowi]

Close to 200ah from totally flat to completely full. They go out of balance at the top of the charge but give 190ah useable with only 42mv difference in cells @ 14v

How did you measure this capacity?
I just made an accurate celltester with datalogger and I tested 2 200Ah cells with 15A CC (CH/Disch(LD)) ; 2800 datapoints in 11,5 h.
I don't get more than 174Ah / 570Wh from full charged 3.65V to full discharge to 2.6V. They should deliver 200Ah / 635Wh.
(Vbat -blue- is on the right side). First 6h I logged every 10 sec, later every 30sec; that's why the LD lines are not straight (does not affect capacity because it is measured every second)

 

[ScoTTyBEEE]

I used the same battery monitor Will recommended, bottom balanced at 2.9-3.0v then charged at 20A, the battery monitor hit 193.something amps before 1 cell hit 3.65v. Your testing looks far more comprehensive, perhaps my way isn't as accurate? I don't have any other way to test.

 

[gehowi]

I used the same battery monitor Will recommended,

Ok, Thank you.
I made this tester to analyze a lot of problems with such 200A BLS cells (36!)
Now I am testing every cell to see the real capacity but it is certainly not 200AH/635Wh.

I have enough evidence already that BLS battery is selling degraded /crap cells as new, cheating everyone.

Without extended testing most buyers will never know the real capacity and when you find out later they will tell you that you abused them or BLS does not exist anymore.
All they need is those 5 stars on ALI and we all gave them because the price is "good" and they delivered fast without paying tax.

I will soon write a full report of BLS battery with all detailed evidence here on this forum to protect other people from being cheated on Aliexpress/BLS.

If you would feel sad about your investment now, keep in mind there is someone who has 36 of them...
Anyway, for 4S you may not have too much problems if you can live with 150-190Ah and half of the lifetime. For 16S it's a disaster, not possible to keep them balanced and losing a lot of capacity.

 

[Keith_PDX]

You are the only one I've seen have problems with these cells. I visit a few forums and a few FB groups and you're the only one complaining. I wouldn't bash them and claim everyone is getting crap cells. Not saying that your experience isn't shitty, it is.

I have tested my 150Ah cells from BLS both individually and as a whole pack twice. I've wasted two weeks of my spare time with this! My numbers suggest that the rated capacity is accurate and then some. Here is my final charge as a pack. Started at 2.9v per cell and charged the while bank at 25A with a Victron 120VAC charger set to lithium. You can see how much energy went into the cells, measured with a Victron BMV-712. I'll post up an AH discharge later.

I use a Deligreen active cell balancer (6A).

 

[Keith_PDX]

Mid build and testing. Tested with and without the Balancer. The cells stayed within .05v of each other without the Balancer and within .01v with it. The stickers from BLS indicate they were matched cells. The cell resistance readings from two different chargers and cell testers agree.

 

[gehowi]

You are the only one I've seen have problems with these cells.

I certainly believe you did your tests well and your cells may have the right capacity.

You and me tested their batteries but most people don't have accurate tools, install them and never know the real capacity , gave 5 stars and write positive comments as everything looks fine in the first month.

BLS does not sell new, qualified batteries. If they did then we would have original ETC cell test reports and 5 year ETC warranty.
That's why my first 16 batteries were bad and bulged (4) already before I even connected them. After long discussions with BLS I bought a second set under strict conditions.
They selected 20 "new" batteries out of 100 to get a good match (they said). These were better but why they have to select from so much batteries if they were new and original?

ETC guarantees very narrow specifications on their test reports, including cell thickness, no need to select them out of many.



M4 and Blue cell cover:
One month after my first purchase of M6 cells (pole screws) BLS could not deliver M6 anymore; they delivered M4.

In a discussion with BLS about the very bad applied blue cell cover with lots of airbubbles/dust and the silly M4 screws they send me a picture that they drilled the poles themselves!



So they also buy cells with undrilled poles. According to ETC manufacturer that means that these cells have been tested during production but did not qualify.
They are removed from production before the plastic cover is applied, poles are drilled or labels applied. ETC says such cells should have been destroyed and never been sold to market. It's however possible that they sell them very cheap as industrial waste to traders.

As the blue cover is randomly cut with a scissor and applied so unprofessional this is probably done by BLS. Not one cell was the same, it cannot be done automated by ETC.




Cells bought from ETC or official distributors are 30% more expensive than BLS.
My battery types are NAH3L 200*174*54mm.
ETC could only offer me 206Ah in this type a week ago (oct/2019).
5 years written warranty; at least 206Ah guaranteed + test report per cell + 24 bit serial nr. No bargain possible below 100cells, only 1 price.

ETC offer:


Serial nrs not valid on BLS batteries:
Not one of my serial nrs could be verified by ETC. They replied that this can have only 2 reasons: they are fake (not ETC cells) or they were disqualified for market. Every ETC cell must have a traceable 24 bit serial.

No ETC 150 / 190Ah capacities
ETC does not produce 150 and 190 Ah cells in NAH3L , only 206 and 277Ah. In case your cells are not ETC or another type, I can't say something.

I suspect BLS re-labels such rejected cells after testing remaining cell capacity and sells them according to that capacity.
So you may have the right capacity but not the right quality.

Lifespan; MTBF:
If a cell is certified for 206Ah but deliver only 170Ah, it is degraded or defective. The lifespan may be very short. I doubt very much they will last 10 years/4000 cycles as I see the rapid degrading of my cells in only 4 months.
When they die in 3 years, BLS will not replace them and very likely BLS will not exist anymore.


ETC made NAH3L 176Ah cells in 2017; 206Ah cells in 2018 and the end of 2018 they planned to have reached 228Ah; all in the same size and package. but in 2019 they only offer 206Ah...
Since my first tested cells deliver max 174Ah, they may be 2y old cells from 2017 which I got in july 2019. In that case, it may explain some of them were bulged.. Who knows how long they were completely discharged.


So the quality and capacity you get from BLS is just gambling and your warranty is zero once you agreed in Aliexpress.
If anyone want to buy there, no problem. At least you know the risks now.