Aliexpress BLS LiFePo4 cells problem

[Carlos Carrapiço]

This is my first post although I have been registered and following for a while.

I have acquired the 16 prismatic aluminium cell pack from BLS following the review and advise by Will in his website. Additionally, I have acquired also 4 common port BMS rated for 100A. https://www.aliexpress.com/snapshot...rderId=3002348202856063&productId=33054219276

My idea was to create a 24V 100A bank for my boat's trolling motor with the possibility of later upgrading to 36V. The remaining 8 cells would be to create a 12V 100A bank to run the electronics on the boat and to have a separe 12V 100A for starting the outboard.

Until now I have been testing the cells and have encountered the following problems:

Charging each 12V bank with a Victron Blue Smart IP67 12V 25A I was unable to charge each module higher than 3,403 in average because one will go to high and the BMS will open the circuit. The target voltage was 3,55 per cell making 14,2V per bank.

The other problem is that I received two different BMS models. One (1-102-13940-J05A) is a 120A discharge 60A charge which seems to work just fine.
The second (1-102-10000-24A) is a 120A charge/discharge but the voltage protection features for the cells seems to only kick in too late both at high and low levels.

I have also balanced all cell to 3,403V by charging them and connecting them in parallel for a couple of days. Then I start seeing a voltage drop every day between 10 and 20mV except for one module.

Please advise.

 

[Banana_Luke]

I would measure the voltage on the whole setup. This sounds like to thin cables for me. Which will result in voltage drop over the cables, thus wrong reading. Measure with a good multimeter to get reliable results.

Regards Luke

 

[Supervstech]

This is my first post although I have been registered and following for a while.

I have acquired the 16 prismatic aluminium cell pack from BLS following the review and advise by Will in his website. Additionally, I have acquired also 4 common port BMS rated for 100A. https://www.aliexpress.com/snapshot...rderId=3002348202856063&productId=33054219276

My idea was to create a 24V 100A bank for my boat's trolling motor with the possibility of later upgrading to 36V. The remaining 8 cells would be to create a 12V 100A bank to run the electronics on the boat and to have a separe 12V 100A for starting the outboard.

Until now I have been testing the cells and have encountered the following problems:

Charging each 12V bank with a Victron Blue Smart IP67 12V 25A I was unable to charge each module higher than 3,403 in average because one will go to high and the BMS will open the circuit. The target voltage was 3,55 per cell making 14,2V per bank.

The other problem is that I received two different BMS models. One (1-102-13940-J05A) is a 120A discharge 60A charge which seems to work just fine.
The second (1-102-10000-24A) is a 120A charge/discharge but the voltage protection features for the cells seems to only kick in too late both at high and low levels.

I have also balanced all cell to 3,403V by charging them and connecting them in parallel for a couple of days. Then I start seeing a voltage drop every day between 10 and 20mV except for one module.

Please advise.

Oh my... “balancing” and 3.403V do not belong in the same sentence...

either they get balanced at 3.65v per cell, or at 2.5v per cell... anything in between will just confuse you.

 

[Banana_Luke]

Isn't there the balancing mode where it balances during charge and discharge continuously? ?

 

[Supervstech]

Yes, but when you start out with a knee charge across all the cells, you don’t know how close to full each one is, so some could be nearly empty, and some could be totally full at 3.4xx so, pumping constant current into an unbalanced set will exceed most BMS ability to manage...

 

[Carlos Carrapiço]

I would measure the voltage on the whole setup. This sounds like to thin cables for me. Which will result in voltage drop over the cables, thus wrong reading. Measure with a good multimeter to get reliable results.

Regards Luke

I did all measurements directly on the cell poles or as close as possible to the source. The only length of cable is the one from the multimeter.

 

[Carlos Carrapiço]

Oh my... “balancing” and 3.403V do not belong in the same sentence...

either they get balanced at 3.65v per cell, or at 2.5v per cell... anything in between will just confuse you.

I know but because one cell goes too high and the BMS kicks in stopping the charge process, this was the highest I managed to achieve.
I did this by charging all 1P4S banks with a 14,2V Victron charger and then parallel all cells in a 16P1S configuration for a couple of days.

 

[Supervstech]

I know but because one cell goes too high and the BMS kicks in stopping the charge process, this was the highest I managed to achieve.
I did this by charging all 1P4S banks with a 14,2V Victron charger and then parallel all cells in a 16P1S configuration for a couple of days.

I don’t think a charger can balance cells well if they are out to begin with...
You need to either deplete them to bottom balance individual or massively in parallel, or top balance.
Once tied in series, they can drift in voltage beyond what a BMS can handle.

 

[Carlos Carrapiço]

Yes, but when you start out with a knee charge across all the cells, you don’t know how close to full each one is, so some could be nearly empty, and some could be totally full at 3.4xx so, pumping constant current into an unbalanced set will exceed most BMS ability to manage...

I guess that is exactly where I stand
What would you advise?

I have to decide if I open a dispute or not until Saturday evening

 

[Supervstech]

I would tie all cells in parallel, and attach a load to them until they drop to 2.5V, then set them in series and charge them back up.

 

[Carlos Carrapiço]

I would like to say how appreciated your help is.
I jumped on this adventure hopping not only to save some cash but also to have a fully functional and customised system to my needs.
Ended up with more problems than solutions.

Thank you all for your help.

 

[Carlos Carrapiço]

I would tie all cells in parallel, and attach a load to them until they drop to 2.5V, then set them in series and charge them back up.

I'll try this. Thanks

One additional question:
The cells have been dropping in tension when at rest. Is this normal? Table with details bellow

 

[Supervstech]

Of that I do not know, sorry.
Perhaps others with more specific battery knowledge will chime in here?

 

[Carlos Carrapiço]

I have also measured the DC resistance of the cells and got something between 3 and 8 mOhm. Have no clue if this is good or bad. The AC impedance stated by the seller is one order of magnitude lower...

 

[MisterSandals]

One additional question:
The cells have been dropping in tension when at rest. Is this normal? Table with details bellow

From my experience with 206AH cells, this has been my exact experience. They tend to settle down to 3.2v and then stay there for days on end.

But first you need to do either a top balance or a bottom balance. My understanding is that you should balance nearest where your batteries will mostly operate: are you running the batteries down most of the way everyday or will you have the batteries mostly topped (fully charged).
I intend to be mostly fully charged or as much as possible so i top balanced (3.65v).
Hooked them all in parallel overnight then charged to 3.65v (from roughly 3.2v).

At this point, my cell difference REALLY tightened up to 10-20mV all the time.

So choose your balance point (top or bottom) and get that taken care of first.

Regarding testing internal resistance, i think its a waste of time. I tried many different tools and methods. My results showed that the position of the cell in the battery made the most difference in how my tools (ISDT, Tenergy, HobbyMade Duo Pro...) calculated IR. Maddening i say.

<EDIT/> I meant to say/type:
They tend to settle down to around 3.32v...

 

[Bhupinder]

Regarding testing internal resistance, i think its a waste of time. I tried many different tools and methods. My results showed that the position of the cell in the battery made the most difference in how my tools (ISDT, Tenergy, HobbyMade Duo Pro...) calculated IR. Maddening i say.

Absolutely. Am observing the same phenomenon where Cell positioning within the Pack is making it act differently.
@ MisterSandals, do you have any more observations as to how best to place cells to make a uniform recharge?

One of the Middle Cells in my 100A 4S pack was getting charged up too quickly and I placed it at far +ive terminal,
it got dormant. However one on the Far -ive side charged upto 3.9V, I'm Not using a BMS as of now.

After a 14V charge cycle on the pack with external charger, here were the Voltages in the morning:
3.362=>+ive end
3.339
3.338
3.967=>-ive end

Does it look normal or could there be some Issue with the Cells?

 

[MisterSandals]

Yow, 3.957v. Thats too high from what i’ve heard. Damage supposed to happen over 3.65v. You are an explorer, keep us posted.

Have you tried top balancing?
Put them in parallel overnight. Then discharge down to around 2.8v. Then charge to 3.6-3.65v.
Assemble as battery and see if the behave better (similarly).

Depending on how that goes, you may need to have your SCC limit charging to around 13.8v or so to keep ANY cell from getting over 3.6v. (It runs away fast at this point). And you may need a BMS with a lot of balance current.

I too am BMS-free until i find one that i like.
Fortunately my cells are behaving enough after top balancing and limiting charge voltage. I will eventually get a much needed BMS for unattended installation.

Hope this helps.

 

[Bhupinder]

Yow, 3.957v. Thats too high from what i’ve heard. Damage supposed to happen over 3.65v. You are an explorer, keep us posted.

Discharged it with a small load to 3.4v, it came back pretty fast I would say.
May be not much charge is stored over the 3.4v mark it seems.
However, most journals state that LiFePo4 can withstand 4.2v on the higher Side, hope the cell is safe @3.9

Have you tried top balancing?

I am thinking of Top balancing individual cells till 3.5v any of these days and call it a day.

Depending on how that goes, you may need to have your SCC limit charging to around 13.8v or so to keep ANY cell from getting over 3.6v. (It runs away fast at this point). And you may need a BMS with a lot of balance current.

Yes, BMS may be the route to go stress free in the long haul.
But the one which could reliably take care of all systems at work are selling at hefty prices.
Not much interested in putting such "Bling" to DIY projects, If not for safety reasons. They are supposed to serve the basic DIY purpose first

Cheers!

 

[JoeHam]

However, most journals state that LiFePo4 can withstand 4.2v on the higher Side

Reference please!

I highly doubt anyone on this forum would agree with that and I stand ready to be corrected.

 

[Dhowman]

This is an excellent step-by-step on how to top balance that I intend to use when my 16 150Ah cells from BLS arrive (oh this week, pretty pls!!). It ought to be a sticky.