Catastrophic failure 200ah 12v battery

[12street]

Temp outside was 107*, inside the shed was less than 120*, so I can not see that being the problem.
I had two days prior added "Heltec Whole Group Balancer " to the mix, but can not imagine that overriding the BMS to allow runaway voltage.
The BMS, from aliexpress, was only one week new replacing a Daly which allowed up to 3.7v -Daly stated was OK but I could not get comfortable with.
Also, I am more comfortable topping out at 3.4V/13.6v to extend life of cells (I thought...)
Cell 1 expanded almost uncontrolled. Currently sits at 3.3v SOC after 4 days.
Cells 2,3,4 expanded but much less so. They currently sit at 3.50/51V.
So, a couple of questions:
-I assume the BMS is the cuplrit -any thoughts? I certainly do not want to attach it to my good bank to experiment.
-Is it possible that it was simply a faulty cell? I have had them for just over 1 month, but have certainly less than 10 full cycles of use.
-How could I test the remaining 3 to verify fitness for service, without pulling another cell from my good bank?
-Or is this simply an horrible idea, and just walk away from the $525 worth of cells?
I purchased cells from an amazon seller with no feedback, suspect, but do not want to pursue chargeback without a high degree of certainty.
Thank you in advance for any assistance

 

[MisterSandals]

-I assume the BMS is the cuplrit -any thoughts?

Do you have any idea what was happening when this happened? Charging? If so, with what and was it thru the BMS? Any idea how high the cell's voltage got (thru a bluetooth app for example?).

There's not a lot to go on based on what you wrote. It seems that one of the cells got overcharged for a prolonged period of time. The heat probably didn't help but I suspect may have contributed a little.

That cell is gone. Wrap it in an Amazon box and put it in sight on your porch.

The other 3 cells are not really useful but if not swollen too bad are probably ok. If you can get a similar 4th you may be able to make a useful battery.

I see nothing that points to the cell seller or a problem with the cells. Was there anything unusual about them when you first got them? Very high, low or uneven voltages?

 

[noenegdod]

I apologize for not adding anything to your specific question but seeing this, I am curious what your and anyone else opinion is on how much the box failure contribued. Had the box remained intact, would the batteries have survived?

 

[wholybee]

The BMS would only be at fault insofar that it did not protect the cells from a charger that was not operating correctly. The BMS will not protect from a balancer malfunction. Nor would a failed BMS destroy cells without a charge source that was overcharging them.
I have no experience with them, but I expect that improper connections of a balancer could overcharge a cell. For example, if 2 cells were counted as one due to miswiring, then the balancer might try to charge the remaining cells to the higher voltage of 2 series cells.

 

[wholybee]

I apologize for not adding anything to your specific question but seeing this, I am curious what your and anyone else opinion is on how much the box failure contribued. Had the box remained intact, would the batteries have survived?

Probably not. I expect that the vent would have blown, spilling electrolyte everywhere.

 

[sprint2freedom]

Tell us about your charge termination parameters.

Did you capacity test these cells prior to putting them into service as a pack?

 

[12street]

Tell us about your charge termination parameters.

Did you capacity test these cells prior to putting them into service as a pack?

I did not perform a capacity test, but I did a top balance to 3.6V prior to service last month and let them sit for 3 days (just the days I had available, not by design.
As I had not yet received my bluetooth dongle they were solar charged, with a Renogy wanderer which I have been using for appx a year with no issues, to the factory settings of the BMS "over charge protection voltage 3.65+/-0.05V".

 

[12street]

The BMS would only be at fault insofar that it did not protect the cells from a charger that was not operating correctly. The BMS will not protect from a balancer malfunction. Nor would a failed BMS destroy cells without a charge source that was overcharging them.
I have no experience with them, but I expect that improper connections of a balancer could overcharge a cell. For example, if 2 cells were counted as one due to miswiring, then the balancer might try to charge the remaining cells to the higher voltage of 2 series cells.

The balancer was new, but of such limited current I can not imagine how it could contribute.
My PV is certainly of enough voltage (up to 19v) to blow a cell without the charge controller, but one bank is still fine while one erupted -hence my presumption of the BMS or Cell being the fault.
I guess the real question is whether or not I can test the BMS in any way, short of substituting it in to the battery that survived the weekend, to rule it in or out...

...also, insight into whether or not I could/should buy another 200ah cell to pair with the three that hold voltage still.

 

[sprint2freedom]

During my capacity testing, I found that a poor connection at a terminal can cause heat to be produced at the terminal which is then conducted into the cell warming the whole case. Perhaps this is what occurred in the cell that failed and it then overheated the cell.

It's not possible to determine the quality of a connection by visual appearance alone. One low tech way is to place a large load on the cells while monitoring the terminals for warmth. The test duration must be long enough for such heating to become noticeable (minutes not seconds).

Since you recently disturbed the terminals to add a balancer, this is my guess as to what most likely happened.. and also why only one cell was affected.

Having the cells in a 120 degree shed reduces the amount of (additional) terminal heating that can be tolerated.

 

[12street]

Do you have any idea what was happening when this happened? Charging? If so, with what and was it thru the BMS? Any idea how high the cell's voltage got (thru a bluetooth app for example?).

There's not a lot to go on based on what you wrote. It seems that one of the cells got overcharged for a prolonged period of time. The heat probably didn't help but I suspect may have contributed a little.

That cell is gone. Wrap it in an Amazon box and put it in sight on your porch.

The other 3 cells are not really useful but if not swollen too bad are probably ok. If you can get a similar 4th you may be able to make a useful battery.

I see nothing that points to the cell seller or a problem with the cells. Was there anything unusual about them when you first got them? Very high, low or uneven voltages?

Yes, it was certainly charging at some point during the failure although I had not been to the shed for a couple (very hot) days.
And yes, it was through the BMS which I had only installed less than one week earlier.
"The other 3 cells are not really useful but if not swollen too bad are probably ok." Clarify please, if they hold capacity and cycle are they ok? Or, are they at incereased risk of failure due to the appx 2cm swell?

 

[MisterSandals]

if they hold capacity and cycle are they ok? Or, are they at incereased risk of failure due to the appx 2cm swell?

My understanding is that they are likely mostly fine, just some reduced capacity.
The good news is that LiFePO4 failure is only as bad as you have seen (but some material venting is not “allowed” to expand.
There is limited downside and danger. Probably very useful still if you can match the 3 with a sufficiently equal 4th. That’s the tricky part I suspect. It will need to charge and discharge equally with the other 3.

 

[wholybee]

The balancer was new, but of such limited current I can not imagine how it could contribute.
My PV is certainly of enough voltage (up to 19v) to blow a cell without the charge controller, but one bank is still fine while one erupted -hence my presumption of the BMS or Cell being the fault.
I guess the real question is whether or not I can test the BMS in any way, short of substituting it in to the battery that survived the weekend, to rule it in or out...

...also, insight into whether or not I could/should buy another 200ah cell to pair with the three that hold voltage still.

It does not require high current to overcharge a battery. Only a few tenths of a volt too high voltage and time will do it.
It is very unlikely the BMS is solely at fault. The charge controller or the balancer must share the fault. There just isn't a way the BMS could do that to a battery unless something else was over charging the cells. The BMS _should_ protect from that happening, but won't _cause_ it. One possibility is that the Solar charge controller is not set properly for LifePO4, and the Daly was protecting the cells from damage, and the new BMS failed to.
The best way to test the BMS is to set the low and high voltage cutoffs to very safe levels, (say a low of 3V, and a high of 3.4V) and then cycle the battery and confirm the BMS cuts of charge and Discharge at the programmed points. Yes, you need to connect it to a battery to do that.

 

[mrzed001]

This is the second prismatic cell LiFePO4 battery with Daly BMS that is destroyed in a month. ZERO FIRE !
The BMS main function is to protect the cells. In the other case 90V+ was going to the 24V BMS because of a faulty MPPT. I agree that is 4 times higher, could not handle it.

Here I see other issues:
- PWM charge controller for LiFePO4 ? That's bad. PWM is only a switch that allows the 19V solar to 12V battery, then stops, then starts ... in a 1-200 Hz frequency. Lithium batteries hate it. Even lead acid batteries hate it in a long run (in short de-sulfates them with this hammering).
- BMS will not recognize the V spikes. Visible only on an oscilloscope. So BMS can not protect against it. Can even damage BMS (BMS has MOSFETs and they have a max allowed V).
- Charge to 3,65V? Not needed, too much. You need to use CC(-CV) charger. If you reach 3,5V then battery already 95-98% full. No need even for absorption (see @Off-Grid-Garage videos in this matter)

 

[MisterSandals]

with Daly BMS that is destroyed in a month.

The picture actually looks like an Overkill or JBD. All the Daly's i have are red.

Here I see other issues:
- PWM charge controller for LiFePO4 ? That's bad.

I won't judge PWM SCC's, I've had good luck with them. But the OP has not mentioned what his SCC is which is a bit worrying. Similarly his charge settings are a mystery too.

Can't determine much with any certainly with so many secrets.

 

[mrzed001]

The picture actually looks like an Overkill or JBD. All the Daly's i have are red.

I think it is maybe the "stupid" Daly (not the red smart BMS)

I won't judge PWM SCC's, I've had good luck with them. But the OP has not mentioned what his SCC is which is a bit worrying. Similarly his charge settings are a mystery too.

Can't determine much with any certainly with so many secrets.

Said have "Renogy wanderer" SCC. I can only find PWM versions. Some versions "say" they are lithium "compatible".
OK I believe it when I see it in an oscilloscope :D

Many do not understand the difference between a PWM and an MPPT charge controller.
Here is a good video explaining PWM, then MPPT:

 

[sunshine]

I am curious what your and anyone else opinion is on how much the box failure contribued.

Being one of the outside batteries and not inside increases that probability.

Probably not. I expect that the vent would have blown, spilling electrolyte everywhere.

A blown vent would have excluded the frame.
120f in the shed can only be ruled out if another fault is found.

 

[Gazoo]

The picture actually looks like an Overkill or JBD. All the Daly's i have are red.

I agree and they have the same green QC PASS sticker on them.

 

[Gazoo]

Cells 2,3,4 expanded but much less so. They currently sit at 3.50/51V.

IMO they bloated...at least from what I see in the photos. It appears as though the bloating gets progressively worse looking at the cells from right to left with the one on the left being the most bloated cell and the one on the right is the least bloated?

There are too many unknowns as to what caused this but it appears the cells were overcharged and I don't think the ambient temperature would have caused this. I always recommend testing the HVD and LVD of a BMS before it is put into service.

 

[Hedges]

Active balancer bypasses BMS, correct?
It is new addition, so most likely suspect.

If an active balancer takes its power from after BMS (so BMS can disconnect) and then provides current to each cell, BMS should be able to monitor and protect individual cells.
What are settings of active balancer, specifically max voltage it tries to drive into each cell?

It does not require high current to overcharge a battery. Only a few tenths of a volt too high voltage and time will do it.

What I was thinking.

 

[Gazoo]

The working voltage of the Heltec is rated 2.7V-4.5V. This is so they can be used with different lithium chemistries. The active balancer moves current from the highest cell to the lower cell to balance the voltage. It has no external connection to a power source.

The high voltage disconnect is regulated by the charging source and if a cells voltage goes too high the BMS should disconnect the charging source. This is my understanding of active balancers and I don't understand how a defective active balancer would cause a cell to go over the BMS voltage settings. I could be missing something and I am always open to being educated