Hardcase 4s 5Ah Turnigy LiPo cell popped. No fire.

[parabellum]

Have opened one of my duct tape packs, because 1 of the cells was self discharging from the moment I received from HK. It is loosing less then 0.5V per months but was performing well and capacity was similar to others. Just did it out of curiosity and look what I found.


Hole in the cell is about 1mmx0.5mm. (small hole in the middle of big one)

And there was something wrong from start on. Peace of copper tab (soldered on the board) is welded to aluminum tab of the cell.

[neptronix]

I had this happen too, but my cells were not compressed in a hard case. It was obvious the second i got it. I left the pack outside, and it puffed up and let it's gas out in a few weeks.

That is an interesting diagnosis though, i did not consider a construction error to be the cause of something like that!

[parabellum]

Yes David I remember Your tread. In my case I did all charge-discharge procedure, observed voltage droop at higher discharge rate then stored for few weeks. Only irregularity was minor voltage droop after storage. Since I got no extra pack ( or those 4 were my extra packs ) I used this one for few months in reserve configuration of 16s1p. Now 15s1p left!

[dnmun]

the vpower pack i was given had been damaged while being contructed. by analysis i could tell they had dropped it on the corner very early in the assembly when the ribbons had been spot welded, like it had been tossed on a bench or fell on the floor onto the corner and shorted out the ribbon.

which ended up shorting out an entire row of cells, but they never knew it and shipped the battery with the one row essentially ready to short out at any moment. with the burned connector ribbon still right next to the steel sleeve of the 16650.

from looking at the videos i have seen of the chinese factories, there is very little mid level mid process quality control. or even end of line testing it seems.

the headway charger i worked on had come dead from the factory, the trace for the power mosfet was torn because someone had jammed the heat sink inside when assembled, and they never tested it, broken at assembly.

[parabellum]

dnmun,
I have received multiple damaged items from china, in 1 case complete batch of BMSs that where changed in design to previous batch and apparently nobody checked if they work properly (I wonder how many they produced before I comunicated about failure ) but have been lucky with this particular cheap 4s 5A hard case pack. Have purchased over 60 of those, only 3 came with issues in 1 cell each. So now I have 3x 3s 5A hard case packs as well.

[miuan]

I've had a new cell from 4S hardcase develop a very similar puffing and hole recently. No fire, no smoke. Cell got to 0V on its own. I had another cell die its death last week, taking down another parallel cell that I was able to recover. Definitely we need to keep an eye on these for swelling, and not get lazy about checking balance.

[dogman]

It seems that the typical result is a popped cell and venting, but no fire. But John did have some heat with his defect 4s pack. It wouldn't take much of a spark to ignite what vents when a cell pops.

I just store anything less than a good pack outside. I'm a cheap bastard and perpetually broke, but I won't keep a shit pack in use, or bring it inside. You guys gotta buy an extra pack or two so you can do that.

Even the good stuff is stored in metal boxes that isolate 8 packs max per box, and I keep it in a fire resistant place, a tiled fireplace hearth.