Help! 2 Cells of my 16s LIFEPO4 Pack rises voltage above 4V and bloated up extremely without charging

[helkatz]

Hi Guys,
I have a 16s 280A Battery Pack build in a ESS Case with Seplos BMS and EVE LF280K cells.
THere is also an active balancer connected from QCC
The cells are fixed in the case
All where successfully charged to 3,45 V.
The day after i as i tried to built in the pack to my vessel i had to dismount some cells to make the pack lighter.
As i removed the screws from fixture which was quiet hart the 2 of the cells expanded dramatically they get 1,5 cm thicker!
i even could not get them out of the case, because they were so tight.
to get them out without any violence, i reconnected the cells again so that i can make a discharge with my inverter in the hope the swelling goes a bit back.
as i checked voltages in bms i saw that two cells hat 3,9 V. at this moment the discharging was running for about 1-2 mins. so in this case i assume the voltage was before discharging above 4 or maybe 5V.
So how can this happen wihout any charge connected.
Can this be caused by the active balancer?
Or can cell voltage rise due an damaged cell by itself?

 

[meetyg]

Is your active balancer intended for Lifepo4 cells? Is it programmable? Maybe it's intended or setup by default for Lithium-Ion (NMC etc...) cells, and it tried to charge some of the cells up to 4.2v which is maximum for Lithium-Ion ?

Also, how did you charge cells up to 3.45v? Did you charge the while pack or each cell individually?

 

[helkatz]

Is your active balancer intended for Lifepo4 cells? Is it programmable? Maybe it's intended or setup by default for Lithium-Ion (NMC etc...) cells, and it tried to charge some of the cells up to 4.2v which is maximum for Lithium-Ion ?

Also, how did you charge cells up to 3.45v? Did you charge the while pack or each cell individually?

the balancer is not configurable its the "Qucc 4S-24S Li ionen Lifepo4 10A Aktive Balancer"
i charged up the whole pack to 3,45 V after 1st cell reaching 3,45V the BMS disconnectes charging.when cells are blow 3.4 V BMS allowed charing again. and so on. i did this to give the balancer chance to balance which was working fine.

The question is is it possible that a active balancer generate higher voltages from an source with lower voltage

 

[Rocketman]

I believe that cell balancer does transfer power from one cell to another.

We’re any cells lower than the rest?

 

[helkatz]

I believe that cell balancer does transfer power from one cell to another.

We’re any cells lower than the rest?

i know that the balancer transfers power from one to another but normally from an higher volatage to a lower one.
but in my case the two cells where overloaded so where comes this energy from?can it be the chemistry or can it be the balancer.
when it is the balancer then it must generate higher voltages from an lower one

 

[brum]

I believe that cell balancer does transfer power from one cell to another.

If it is capacitive - yes. If it is inductor based - it may raise the voltage. It uses the inductor to store charge and then dump it in the lowest cell. This is how step up converter works. The one here is with inductor, so it might be responsible for the problem.

Though if it was the balancer, it is more likely that there was incorrect balancer wiring than the balancer itself.

To the OP - I don't think cell voltage can rise on its own due to cell damage. At least I see no theoretical way that this can happen.

 

[SeaGal]

Faulty balancer or how it was connected?

 

[houseofancients]

Hi Guys,
I have a 16s 280A Battery Pack build in a ESS Case with Seplos BMS and EVE LF280K cells.
THere is also an active balancer connected from QCC
The cells are fixed in the case
All where successfully charged to 3,45 V.
The day after i as i tried to built in the pack to my vessel i had to dismount some cells to make the pack lighter.
As i removed the screws from fixture which was quiet hart the 2 of the cells expanded dramatically they get 1,5 cm thicker!
i even could not get them out of the case, because they were so tight.
to get them out without any violence, i reconnected the cells again so that i can make a discharge with my inverter in the hope the swelling goes a bit back.
as i checked voltages in bms i saw that two cells hat 3,9 V. at this moment the discharging was running for about 1-2 mins. so in this case i assume the voltage was before discharging above 4 or maybe 5V.
So how can this happen wihout any charge connected.
Can this be caused by the active balancer?
Or can cell voltage rise due an damaged cell by itself?

did you disable the protection switches of the seplos bms ?
if not, the only thing i can think of is indeed a busted balancer, or realy bad cells... the latter being much less probable than the first

 

[helkatz]

If it is capacitive - yes. If it is inductor based - it may raise the voltage. It uses the inductor to store charge and then dump it in the lowest cell. This is how step up converter works. The one here is with inductor, so it might be responsible for the problem.

Though if it was the balancer, it is more likely that there was incorrect balancer wiring than the balancer itself.

To the OP - I don't think cell voltage can rise on its own due to cell damage. At least I see no theoretical way that this can happen.

The pack was assembled many days before and balancer wiring was checked and has been worked. i never had an over voltage detected before.
one day before this issue i tried another balancer because i was not satisfied with the QUCC.
This was the "Daly Smart Equalizer 16S 1A for Lifepo4 Li-ion LTO Battery Groups Capacitor Balancer PCB".
But this i disconnected next day in the morning!
So the pack was from about 7 am morning only with the QUCC balancer connected and nothing else
The overvoltage mesurement was at 5pm so thats 10hours

so I don't think the Daly balancer can have caused the error because it hadn't been connected for 10 hours.
So in summary, if the cell cannot increase the voltage by itself through some chemical process, then it can only be the QUCC balancer, because only that was connected the whole time

 

[mikefitz]

It's very possible the balancer has caused your problems. With quality cells active balance should not be needed .
The question is why did the BMS not Indicate cell overvolts?

 

[helkatz]

It's very possible the balancer has caused your problems. With quality cells active balance should not be needed .
The question is why did the BMS not Indicate cell overvolts?

The cells are not the best thats why i added an balancer!
The BMS could not disconnect anything maybe it recognized it.
ok question is, as i started discharging should this be prevented by the bms?? maybe it blocks just charging on an overload and blocks only discharging on low voltage!

 

[littleharbor2]

The day after i as i tried to built in the pack to my vessel i had to dismount some cells to make the pack lighter.

Is it possible you have incorrectly rewired the balancer and/or the BMS and this is where your overcharging is coming from?

 

[helkatz]

Is it possible you have incorrectly rewired the balancer and/or the BMS and this is where your overcharging is coming from?

as i disassembled the cells were already damaged the are extremly bloated
and as i assembled for discharge i only connected the bms and this shows me that exactly these 2 bloaded cells with overvoltage

 

[helkatz]

For me is just important to know if the cell chemistry can cause such an issue ( but i dont think so)
and when it was not the cell itself then it only can be the balancer

 

[littleharbor2]

as i disassembled the cells were already damaged the are extremly bloated
and as i assembled for discharge i only connected the bms and this shows me that exactly these 2 bloaded cells with overvoltage

Well I feel for you. I bloated 8, 280 ah cells while top balancing them. I hadn't even got to use them when 1,400 dollars worth of lifepo4 sat there like fat little blue loaves of bread. Hope you can track down the cause.

These cells are extremely sensitive to overcharging and they bloat up real fast when you over volt them.

 

[DIYrich]

Did you turn off the BMS, and disconnect the wire harness before taking apart the battery bank? If not, you may have shorted something to cause the BMS to charge the two cells. But, the charge rate of an active bMS is really low, and you would have to keep it miswired for a long time.

Did the cells expand as you removed the screws, or were the cells expanded prior to you touching them?

 

[helkatz]

Did you turn off the BMS, and disconnect the wire harness before taking apart the battery bank? If not, you may have shorted something to cause the BMS to charge the two cells. But, the charge rate of an active bMS is really low, and you would have to keep it miswired for a long time.

Did the cells expand as you removed the screws, or were the cells expanded prior to you touching them?

Yes, of course i disconnected all wires!
it expanded as i removed the fixture plate immediate and it was a lot of pressure on the plate!
after removing the screws the pack gets 2 cm longer due this two cells all other cells are well!

again i explain the flow

1. day before cells was fully charged to 3.45 cutoff
2. QUCC balancer was connected
3. and for testing Daly smart balancer 1A was connected as well
   charging was switched off
4. next day morning i dis wired the Daly balancer because of not worth
5. i took the pack and transported it to my vessel where i tried to install
   but due this high weight i decided to disassemble and assemble it again at mounting place
6. during disassembling i realized that there is something wrong because i could not remove the fixture screws
   because of the high pressure on it.
7. after get out the screws the pack expanded immediately and the cells wedged themselves together so i couldn't get them out without using force. i rewired the cells with bms but without balancer and connected a load. hoping the swelling will go down. but without success. during first minute of discharge i realized this high voltage on these cells which was 3.9V so before starting discharge the voltage must have much higher

 

[Rocketman]

I just noticed this thread… evidently someone had a defective active balancer that threw two cells too high.

SOLVED: High diff. voltage of 2 adjacent cells at absorption -> defective active balancer

Hi Folks, Guess when i've connected my shiny new balancer... ? Case closed imho ? Thanks again to everyone who assisted me in this case! Have a sunny weekend, Juergen P.S.: Updated thread topic to be hopefully more helpful for the future

diysolarforum.com

 

[helkatz]

I just noticed this thread… evidently someone had a defective active balancer that threw two cells too high.

SOLVED: High diff. voltage of 2 adjacent cells at absorption -> defective active balancer

Hi Folks, Guess when i've connected my shiny new balancer... ? Case closed imho ? Thanks again to everyone who assisted me in this case! Have a sunny weekend, Juergen P.S.: Updated thread topic to be hopefully more helpful for the future

diysolarforum.com

mhh this is not really comparable afaics, because the thread writer has always connected an charger in absorption mode. and then of course 1 cell can rise.

in my caseno charger was connected! Only the balancer was active!!

 

[brum]

I second that. The mentioned thread is for a non-working active balancer and two cells out of balance.

In the current thread, nothing can be pointed out as a definite reason for the issue without historical cell voltage data.

Now when reading once again I see something new - both inductive and active balancers were working at the same time. So this is another suspect. If it was me and I wanted to find out the root cause I would try again with this combination. Of course without leaving the setup overnight and closely monitoring to avoid accidents.

One more question. You are saying:

next day morning i dis wired the Daly balancer because of not worth

How did you decide that it was of no worth? Did you measure cell voltages at this point?