Konion 18650 help needed.

[dutchlincoln]

Hello,
I made a large pack from my brandnew konions, and charged them as a pack.
Unfortunately some were not full, and were drawn emty.
So, i have a 24S pack where 9S is reduced to zero volts...

Are there any "best way's" in how to revive them?
I already disassembled my pack.
It's 14P, so in total i need to revive 14x9=126 cells.
A bit verry pitty if i have to throw them away; they're brand new...

Any tips highly welcome...

Thanks.

 

[SamTexas]

Once a cell gets to 0V, it's unlikely recoverable. But try it anyway using a small 3 to 5V charger like a cell phone charger.

How did those 9 group of cells get there in the first place? Seems so unlikely.

 

[dutchlincoln]

Well, i have a large amount of brandnew makita packs.
I put 7 of these 5S packs together, making 5S/14p.
I made 3 of these.
I used them around a few times, having them charged and balanced with my RC charger.

Then i got a bunch of new packs again.
I made a 4th 5S/14P pack, and a 4S/14P pack to get me a total of 24S/14S for my electric moped.
I just didn't think about charging the 4 and 5s packs first, as i thought they would be full.
So, charging the large pack completely, and wnt for a drive.
Power dissapointed. As i got barely home, i inspected all cells, concluding the 4S and 5S packs were drained, and the other 3x 5S packs were o.k.

So, i disassembled the total 9S/14P, and try hard to revive them...

Any help highly appreciated.

Currently i try to charge them with a laboratory regulated power supply, limiting current at 3 amps.
What i really don't understand, is that i see the voltage gauge go down in voltage?????
Does this mean it's getting more current from the PSU, and thus reviving?

 

[SamTexas]

I made a 4th 5S/14P pack, and a 4S/14P pack to get me a total of 24S/14S for my electric moped.
I just didn't think about charging the 4 and 5s packs first, as i thought they would be full.
So, charging the large pack completely, and wnt for a drive.
Power dissapointed. As i got barely home, i inspected all cells, concluding the 4S and 5S packs were drained, and the other 3x 5S packs were o.k.

Ok, that makes sense. What most likely happened was that the 9s subpack was discharged to 0 and REVERSED voltage. That's a permanent/fatal failure 99% of the time. Those cells are really dead.

On the bright side, you were lucky they weren't RC LiCo. You could have a fire.

 

[dutchlincoln]

Well, that's a very sour bright side... :?

 

[Doctorbass]

Hello Stef,

I would suggest you to charge them individually at 0.1C wich take 10 hours per cells... this is very long as well so it wouold be best to have a RC charger with 6s or 10s to be able to connect some in serie and cahrge more at a time, but you would need to end the cahrge individually to do a correct job to sort the good and bad one. the bad one will have voltage that decrease fast or will just not be able to reach 4.2V without heating .

Once you will have sorted the good clels i wold recomand to tehst their internal rersistance and or capacity, but it all depend on the tooling you have.

The A123 LliFePo4 cells are really tough and can be abused and will recover 98% but the LiMn like the Konion are more sensitive to overcahrge and overdischarge.
Doc

 

[heathyoung]

Yeah and reversing them usually results in permanent death unfortunatly - learnt that one the hard way too

 

[SamTexas]

Well, that's a very sour bright side... :?

You think that now, but I doubt you'd think the same way when your battery bursts into flame with you on it.