First time charging battery, BMS didn't cut off charge properly. Is this cell now dead?

[happy]

I received 4x 280ah eve cells and am using the overkillsolar 120a 4s bms. I have the bms paramaters set to cut off at a per cell voltage of 3.65 and pack voltage of 14.6.

I received all my cells awhile back but had some supply issues getting the bms, so I waited almost 2 months before beginning the initial charge to top balance everything. I hooked everything up in series with the bms and it started charging the battery as a pack. My plan was to charge until the first cell hit 3.65 (cutoff by bms), then rewire in parallel to do the top balance.

Well the cells i had were a lower SOC then I expected so it took a long time to charge it up initially. Last night i was asleep when the bms cutoff, but my partner (who knows next to nothing about batteries, etc) knew to disconnect the charger and did so. Now this morning I looked at the bms info and I see that battery #1 in my pack was charged up to 3.809! And this was after 8 hours of the battery resting without charge!

I unhooked the battery and now have them in parallel. The battery itself was not bulging and looked ok as far as I could tell. Is this battery still safe to use? How do I proceed from here? And why did the overkill bms not prevent this from happening?

 

[John Frum]

I have the bms paramaters set to cut off at a per cell voltage of 3.65 and pack voltage of 14.6.

I always test bms high and low cell cutoffs at safe voltages before I leave the pack unattended.

Do you smell a real harsh chemical smell?
Supposedly the stuff that vents is quite toxic.

Leaking Electrolyte from Bigbattery Powerblock

Just my luck as always. I contacted poison control and they think I will be fine. No symptoms so far. I am pretty sure it is due to cell configuration. 92 pounds of cells stacked in this manner does not seem like a good idea. Second to bottom cell has gas inside and you can hear the...

diysolarforum.com

Is the cell bloated?
If yes that is not a good sign but better than toxic emissions.

I suggest you discharge the cell to within the safe voltage envelope asap.
Then find out why your bms didn't trigger and fix the issue.
Then top balance and run a capacity test to see if you escaped severe consequence.
That cell has now been abused but it may still meet your needs.

 

[happy]

I always test bms high and low cell cutoffs at safe voltages before I leave the pack unattended.

Do you smell a real harsh chemical smell?
Supposedly the stuff that vents is quite toxic.

Leaking Electrolyte from Bigbattery Powerblock

Just my luck as always. I contacted poison control and they think I will be fine. No symptoms so far. I am pretty sure it is due to cell configuration. 92 pounds of cells stacked in this manner does not seem like a good idea. Second to bottom cell has gas inside and you can hear the...

diysolarforum.com

Is the cell bloated?
If yes that is not a good sign but better than toxic emissions.

I suggest you discharge the cell to within the safe voltage envelope asap.
Then find out why your bms didn't trigger and fix the issue.
Then top balance and run a capacity test to see if you escaped severe consequence.
That cell has now been abused but it may still meet your needs.

No bloating (see pic of the cell) but it was in an enclosure while charging. No smell that I can tell, but it had been sitting out for a long time (8+ hours) so it's possible the smell has dissipated. I did hook it up in parallel which reduced the voltage down to around 3.38 pretty quickly, but it had already been sitting at the overvoltage for 8+ hours by that time. I am working on the top balance now and will run a capacity test and report back with my findings.

Not a great thing to wake up to this morning - is it possible to get just a single replacement cell? Don't really want to shell out another $400-$500 if I can get by with just the $100-$150 instead for a single cell if needed

 

[John Frum]

No bloating (see pic of the cell) but it was in an enclosure while charging. No smell that I can tell, but it had been sitting out for a long time (8+ hours) so it's possible the smell has dissipated.

Pretty sure the smell lingers for days or weeks.

That bms is showing a lot of diverse trips.
Usually you would see just one or maybe a couple of the same type.
Yours is all over the place.
I wonder if the BMS is defective.

 

[squowse]

I always test bms high and low cell cutoffs at safe voltages before I leave the pack unattended.

how do you go about this exactly?

 

[happy]

how do you go about this exactly?

My parameters are set to 3.65 over and 2.5 under which is the commonly accepted maximum and minimum and was recommended by the seller of my bms. SmoothJoey is saying you could set it to something like 3.2 over and 3.0 under. Then you can ensure the bms cuts off charging once it is at 3.2v and discharging at 3.0 (both are extremely safe and well within normal range). That way if the bms doesn't cut off properly no harm is done to the cells

I wasn't very smart and just trusted the bms without doing this test and I paid the price unfortunately. Oh well, this is my first build and I'll just have to learn from my mistakes. Still crossing my fingers that the capacity test comes in ok

 

[John Frum]

how do you go about this exactly?

My cells came at 3.29ish volts.
I assembled them into a serial battery with bms and configured the bms high cell cutoff to 3.32 volts.
And charged them until the bms tripped.
I stayed within 5 feet of the disconnect switch until it disconnected.
Did the same for low cell cutoff of 3.3 volt.

 

[squowse]

My parameters are set to 3.65 over and 2.5 under which is the commonly accepted maximum and minimum and was recommended by the seller of my bms. SmoothJoey is saying you could set it to something like 3.2 over and 3.0 under. Then you can ensure the bms cuts off charging once it is at 3.2v and discharging at 3.0 (both are extremely safe and well within normal range). That way if the bms doesn't cut off properly no harm is done to the cells

I wasn't very smart and just trusted the bms without doing this test and I paid the price unfortunately. Oh well, this is my first build and I'll just have to learn from my mistakes. Still crossing my fingers that the capacity test comes in ok

ah i see. of course

 

[squowse]

My parameters are set to 3.65 over and 2.5 under which is the commonly accepted maximum and minimum and was recommended by the seller of my bms. SmoothJoey is saying you could set it to something like 3.2 over and 3.0 under. Then you can ensure the bms cuts off charging once it is at 3.2v and discharging at 3.0 (both are extremely safe and well within normal range). That way if the bms doesn't cut off properly no harm is done to the cells

I wasn't very smart and just trusted the bms without doing this test and I paid the price unfortunately. Oh well, this is my first build and I'll just have to learn from my mistakes. Still crossing my fingers that the capacity test comes in ok

are you going to try that to test your BMS?

 

[happy]

are you going to try that to test your BMS?

Yes although I already wired in parallel so I'm top-balancing first. I'll test the low cell cutoff while i'm doing the capacity test, then do a high cell cutoff test when i'm charging back up afterwards

 

[DerpsyDoodler]

Yes although I already wired in parallel so I'm top-balancing first. I'll test the low cell cutoff while i'm doing the capacity test, then do a high cell cutoff test when i'm charging back up afterwards

the key is to remember not to rely on the BMS until you’ve tested that it works properly.

 

[mikefitz]

And why did the overkill bms not prevent this from happening?

On the parameters setting page there is a value called 'Hardware Overvoltage Protection'.
The default setting is 3.9 volts.
Since the BMS did shut off charging perhaps it did so at this value?
The value seems to in agreement with the 3.8v measured.
I suspect the cell has escaped damage singe the energy input from 3.65 to 3.9 will have been small and the compression feature you have must have helped.

Mike

 

[happy]

Update after capacity test:

The cell that was overcharged was definitely damaged with what appears to be increased internal resistance since it gets a semi-significant voltage drop when under load (compared to the other 3 cells). It's voltage drifted lower than the rest of the cells starting early in the 3.2v range. However, it somehow wasn't the worst cell left in the group! A different cell in the pack actually tripped the LVD on the BMS at 2.5v because once it hit 3.1v it started dropping extremely quick. So although i did damage the one cell, it still wasn't the worst one of the group!

Total amp hours measured with a constant 150w drain = 269.9ah. Voltage levels at the 2.5v cutoff were 2.500, 2.937 (the one i overcharged), 3.023, 3.105

This result really surprised me. I am a little disappointed that one of the nondamaged cells was a decent amount below the rated 280ah capacity, but am also happy that I didn't completely ruin the cell I overcharged. I will likely cycle everything once or twice more to make sure everything is still working ok, but it appears as though I've somehow made it out without needing to buy a replacement cell since 269ah should be plenty of capactity for my needs

 

[OnTheRoadAgain]

Sorry you had an incident with your new batteries. That has to be frustrating.
But sharing your experience may save others the same fate. Including myself.

I have just (today) ordered a set of batteries.
I have just learned that whatever BMS I end up buying to closely monitor it the first few times using it to ensure it works properly and as expected.

So thank you for the lesson.

I do believe you can buy individual cells, but the shipping costs may be the problem.

 

[DerpsyDoodler]

Update after capacity test:

The cell that was overcharged was definitely damaged with what appears to be increased internal resistance since it gets a semi-significant voltage drop when under load (compared to the other 3 cells). It's voltage drifted lower than the rest of the cells starting early in the 3.2v range. However, it somehow wasn't the worst cell left in the group! A different cell in the pack actually tripped the LVD on the BMS at 2.5v because once it hit 3.1v it started dropping extremely quick. So although i did damage the one cell, it still wasn't the worst one of the group!

Total amp hours measured with a constant 150w drain = 269.9ah. Voltage levels at the 2.5v cutoff were 2.500, 2.937 (the one i overcharged), 3.023, 3.105

This result really surprised me. I am a little disappointed that one of the nondamaged cells was a decent amount below the rated 280ah capacity, but am also happy that I didn't completely ruin the cell I overcharged. I will likely cycle everything once or twice more to make sure everything is still working ok, but it appears as though I've somehow made it out without needing to buy a replacement cell since 269ah should be plenty of capactity for my needs

Did you clean the cell terminals? Voltage drop can be caused by poor crimps or poor connections at the terminals.

 

[Smokin]

If you set the cutout at 3.65 then you will never be able to charge to 3.65 so what's the point. What is you line of thinking. 3.8 if fine on the cell no damage.