A123 Pouch Cell Failure?

[BlackburnPete]

I just noticed my battery charger was going on and off every couple of seconds. I have a 16S1P A123 LiFePO4 pouch battery pack that has been working flawlessly since of 2013. I have a Kingpan 5A charger that always charges my pack to 58V. After shutting down the charger, I checked the overall total pack voltage at 55V. I naturally assumed one of my cells was non-responsive. I opened up the pack and checked the voltage across all the cells with the BMS still attached. Each cell was at 3.35V equally. I plugged the charger back in and checked each cell as they were charging. One cell was charging much faster than the others. I immediately shut off the charger and all cells were once again at 3.35V except the suspect cell that was up at 3.51V but it was falling rapidly as I held the voltmeter on that cell. Eventually, I expect that cell will return to 3.35 like rest of them. I think the BMS must be recognizing a high voltage in that cell and shutting down the charger, but as the cell self-discharges, the charger thinks the pack is OK and starts charging again. This repeats every couple of seconds.
Does this sound like a reasonable explanation?
Next, I will try to unplug the BMS overnight and see where the cell voltages end up by morning. I suspect the problem cell will be more obvious by then.

 

[BlackburnPete]

Today, all cells are sitting at 3.35 still except that one cell is now sitting at 3.2V. Do you think I should I should replace that cell? How can I test it to see if it is faulty?

 

[999zip999]

Houses pack put together is it bolted or. ? Where did you get it ?

 

[john61ct]

Today, all cells are sitting at 3.35 still except that one cell is now sitting at 3.2V. Do you think I should I should replace that cell? How can I test it to see if it is faulty?

Isolate and CC load test it

 

[BlackburnPete]

The pack was from OSN Power (2013) and it is 16 pouch packs with bolt on connectors. The foil connectors are folded under the metal strips.

 

[fechter]

Sounds like a bad cell. You could try charging and discharging just that cell via a pair of jumper wires and try to measure capacity.

But just the fact that the voltage dropped by itself that fast is a pretty good indication of a bad cell unless it's being drained by a bad BMS.

 

[agniusm]

I have 2 cells from those days. Shoot me pm and i can probably ship it cheap. my tabs are cut short (8-9mm) and was intended for my kit back in the day

 

[BlackburnPete]

Thanks Agnuism for the kind offer.I have a new cell coming already. Please PM me with your offer including shipping to Ottawa, Canada. I will probably need to start replacing cells on this pack now that one is showing signs of trouble. I have had some temporary success by replacing cells in a Ping pack, but eventually, another one goes bad.

 

[BlackburnPete]

Sounds like a bad cell. You could try charging and discharging just that cell via a pair of jumper wires and try to measure capacity.

But just the fact that the voltage dropped by itself that fast is a pretty good indication of a bad cell unless it's being drained by a bad BMS.

Thanks fechter, I have disconnected the BMS and I have a single cell charger. I am still trying to figure out a suitable load for a single cell discharge without buying a CBA IV from westcoastmountain.com.
Any ideas? Something safe

 

[999zip999]

6 years how many charge cycles ? How is the performance up to now and you getting 17 ah or more out of your. Pack?. It seemed you either got a good cell back in 2013 or you got a shity cell what you found out in a month or two. Osn was still a gamble as was victpower which mine came from. The JRHolmes buy. I think we all learned a lot from Li Ping.

 

[Hillhater]

. I am still trying to figure out a suitable load for a single cell discharge without buying a CBA IV from westcoastmountain.com.
Any ideas? Something safe

Depending on how sophisticated you want to be...
A simple 12 v,50W auto light globe will drain 1 amp @ 3.2 volts. ( i use spare domestic 50W halogen downlighter units...pigtail connectors are readily available)
Parallel several to increase the amps to suit
OR.. some of those LED flashlights can draw quite a few amps on a 3-4volt cell ??

 

[Gregb]

If you have an iCharger u can use it to charge and test single cells.

 

[john61ct]

https://endless-sphere.com/forums/viewtopic.php?t=98407

Plenty of hobby chargers have a controlled-current discharge testing function.

Also, dedicated testers can be cheap, e.g SkyRC BD200 discharger, 200W and 30A

also http://www.myrcmart.com/rcx-3in1-battery-balancer-discharger-voltage-indicator-150w-discharging-p-4767.html


Better units by ZKE, see their EBD and EBC lines.

https://www.rcgroups.com/forums/showthread.php?p=41567843

 

[BlackburnPete]

Happy to report that OSN Power sent me a new A123 pouch cell (20Ah) and I opened up the pack. I immediately saw a leaking corner on the third cell in from the positive end of the pack. I suspect some kind of physical failure, but the pack was very well protected in a padded plastic ammo box. Anyway, I was able to disassemble the first three cells by simply unscrewing the flat bars across the pouch tabs. There was no solder, or spot welds inside the pack. I removed the third cell and moved the remaining two into position 2 and 3. Then I put the newest cell on the end of the pack and replaced all the flat bars and BMS wires. I topped off each of the 16 cells to 3.65V with single cell (1 Amp) chargers. All the old cells were topped off in an hour each, but the new cell took a very long time to reach 3.65V. It must have been very nearly empty when shipped. After I put all the foam back around the cells and the BMS, I re-taped the panels back around the pack and put it back into the padded ammo box. I took it for a demanding ride that used 7.6 Ah over 27kms. (About 14 wh/km) and then took it home for a charge cycle. The battery charged back up to 57.6V and the charger finished successfully with no pulsing on and off. The pack is back to working fine for me and now I still need to run the pack out to the LVC to see how much capacity is still available in that pack. I might be more than 60km from home by then...

 

[john61ct]

Any other long-term members have experience with OSN?

https://osn.m.en.alibaba.com/productlist.html?type=search&SearchText=a123&spm=a277m.main.0.0

 

[999zip999]

One member brought a 16s pack and had lots of trouble with it. It's a gamble buying used cells from rip open packs. Osn is a gamble like victpower. Maybe not that bad. I got lucky with the jrholmes group buy 6 yrs ago from victpower and it was a gamble. And some guy back east did a group buy and tried to run off with the money 40,000 usd. But somebody contacted his sister and then he returned all the money. And a lot of cells with rewelded taps . Not good.

 

[john61ct]

I was under the impression those are all new cells?

 

[amberwolf]

Any other long-term members have experience with OSN?

There's a few threads, and many posts, about them. Couldnt' say offhand which are longterm members.

https://endless-sphere.com/forums/search.php?keywords=OSN*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=OSN*&terms=all&author=&sc=1&sf=firstpost&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=OSN*&terms=all&author=&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search



Specific to A123

https://endless-sphere.com/forums/search.php?keywords=OSN*+a123&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=OSN*+a123&terms=all&author=&sc=1&sf=firstpost&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=OSN*+a123&terms=all&author=&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search