Adventures in Lipo Recovery

Ok so I volunteered to do some lipo recovery for someone. Cell #6 was pretty flat on every pack. One pack being at 0v. The others 1.5v ish. I found 1 pack had damage on the corner of it and the sweet smell of the electrolyte when i sniffed it. I threw it in a lipo bag and gave it a go anyway. It wasnt puffy. Got my alligator clips out and took a JST Balance cable and took the two pins for that offending cell out. Clipped on the alligator clips and check the voltage. 0v. I went through the menu and selected Nicad setting at 0.05. I opened up Log View. I started the charger up and the voltage rose. After each 0.5 volt increase i bump the current up a little bit. The thing I was noticing is the voltage would plateau and barely move so that why i bumped up the current. I finally got it above 3.0v and I stop the charge and there was a rapid decay in the voltage. It drop to about 1.3v and then it slowly dropped back down to 0. I believe the damage to the corner of the cell was causing an internal short. But anyway I did an operation and removed that cell from the pack it disposed of it.

The second pack was at 1.58v on #6 cell. It was squishy/puffed I had a little hope for this one. I did the same procedure as above. The cell was holding a charge a little bit better. There was a decay in voltage after i stop the charger but it didnt drop to far. This second time around I charged the cell up to about 3.5v a cell took it off the charger and there was a decay in the voltage but it stay up long enough for me to switch over to the BC168 charger which charges on each individual channel. After about 20-30 minutes of charging it balanced the pack supposedly but I noticed it would display a weird glitch on cell 6. It would say 4.2v and glitch down to 4.06 and say 4.2 again. Im like just great. It did close the gap but the cell still wasnt completely charged. During the charge cycle the cell was quite warm I moved it back over to the I charger and put the custom JST charge cable up to it and clipped on my alligator clips. I checked the cell IR and it was at 105Mohm. Im lay DAYUM!. That would explain the heating. So damage has been done to this pack whether it puts out full AH or not its gonna sag like a MOFO. I put it on 2A charger and the voltage shot up from 4.06 up to 4.2 good thing the charger doesn shut off until its like C/10 current. It was holding at a steady 1.6A slowly decaying down to 1.1A charge current as of right now.

High cell IR == LOOOOONG CHARGING TIMES... Amps have dropped to .57 since last check in. 1 1/2 hours.

Yee haw,
Your playing with fire there. I have successfully revived two of my lipos from zero voltage back to 4.15. I call the pack my "zombie pack" and use it with trepidation. I have a good 60 cycles or so on it so far without issue.

Based on the IR of these packs they arent going to be put back into comission. Im removing the cells and building a new pack. Im mainly doing this thread to show you how damaged a cell gets from super over discharge.

Still charging... going on 5 hours. Current has dropped to .37A. Its put in quite a bit of AH. I can calculate it just yet because im stopping it to checking to see if the cell is holding voltage or if the charger is fight the cell IR

Ok the sag on the cell is so bad. I started the discharge with the cell at 4.12v. I put a 2A load on it the voltage drops to 3.82v under a 2A load. This pack is unusable.

I was thinking the same thing, I wouldn't be wasting any time on that myself, except to scavenge out any still good cells. Money is tight, but having a fire gets really expensive. A few uses might be ok still, if the pack did revive. But it would have to be stored/charged outdoors, and used on something were a fire could be dealt with easily, like my lawnmower. Just flip the mower, dump out the flaming packs and let em burn on my lawn.

Or switch over to a backup pack and mulch the flames out.

I have 4- 6s packs that I left hooked up in series to a lyen controller on my back-up bike for several weeks after a ride. They got down to less than 1v per cell. I had to bulk charge them above 2.5v at first because the HK eco 6 showed a low voltage error and wouldn't charge them. I have at least 100 cycles on them since and all perform normally.
I was nervous about them for awhile, but I feel safe now. Maybe its because of the very slow discharge that they weren't damaged?

Well, they were damaged, just not completely ruined. No you aren't "safe". Charging them will always be a risk, so I hope you aren't doing it inside.

Chances are, you will see a lot less cycles, and have a lower c rate now than you did before.

The slow rate of the discharge is why they could be revived, but there is a good reason your charger refused to charge them.

I tried to save a pack today.. managed to get all cells back up to 3.8v and they've held their charge. They were down to voltages ranging from 2.5v to 3.6v. Two of the packs were visibly puffed and gave 0v.. didn't try to save them obviously. Lipo isn't as fragile as people make it out to be, you just need to know what you're doing and not do anything stupid.

Not to go against what dogman said.. surely any recovered cells shouldn't be pushing limits anymore but could most definitely be used for aux packs or low powered setups

Im kinda bummed out. Not my lipos personally but to have a pack puff on you and sit at 0V. Or have a pack puff and s it at 1.5v and you can recover it but the IR is off the chart. Its a hard lesson to learn and if you know you are going to take a lipo to the grave those cell alarms are 2.50 and its the cheapest insurance/monitoring device one could own. Friends dont let friends kill lipo. If you know someone thats an abuser call Maury and tell us your story.

i left my cell monitor on my 6s for 2 weeks the highest voltage was .067 and .050 and the rest were zero,but the ir was bout 25 for the pack dead and is 37 now after charged. it was a spyder pack but have bout 50 plus runs in a 18s2p pack with the rest bein hk . the rest of the batterys are bout 70 to 95 ir and dont take the beatin like thay use to.i left that battery for another 2 week dead before revive in her and no puffed cells you get what you pay for and the 150 was def worth it and will buy another 5 for sure

All an all i have about 9 bloated dud cells in a buck of water taking a chill pill. The Ir from the good cells and the bad cells were so bad. They were average about 100-120mohm while the good cells measured between 0 and 2. after being revived to a working voltage. They sagged like a mofo under an small load and they were all puffy. I removed all the cells that were bad. I plan to cut floor tile in about the same size as the cell.. sandwich them together to fill in the empty cell space. I then will take a small piece of wire and solder a bridge to cross over where the cell should be so I can bypass it. The balance taps can remain left intact. I removed the wire for the last cell which was cells 6. It appears as 5s on the charger. Putting a fresh coat of gorilla tape on it. Doing two break in cycles plotting the cell charge and discharge write down the capacity of the refurbished pack and send it back to the owner.

Got some photos of what I said i was going to do with the floor tile. I have a picture of the short/bridge I have on the pack to bypass the missing cell.. I clipped off the balance lead for that cell and removed it from the JST plug. Put a nice layer of Gorilla Tape on it. I threw it on the I charger and got 30A charge graph and a 8-10A discharge graph and printed them out for the customer. Everything looks good. Ready to throw back in the lipo gaurd sack and package it up and send it back to the customer.