Is my lipo doomed?
- Thread starter bart_dood
- Start date
mwkeefer
1 MW
Personally I would be more concerned with the ding than the white markings...
Seriously if you have cycled them once or twice and they haevn't puffed and the balance worked okay, then I wouldn't worry about it... We have seen some pretty knarley looking LiPos from Hobby King but they worked flawlessly.
If your charger does IR calculation, take a reading.. what is the pack IR?
-Mike
Seriously if you have cycled them once or twice and they haevn't puffed and the balance worked okay, then I wouldn't worry about it... We have seen some pretty knarley looking LiPos from Hobby King but they worked flawlessly.
If your charger does IR calculation, take a reading.. what is the pack IR?
-Mike
liveforphysics
100 TW
Some pack construction uses double sided tape to stick the cells together, others drible some rubber cement on and stack them.
IMO, that is dribbled adhesive that was wiped/rubbed off, leaving a wiggle of extra clean de-oxidized surface on the foil pouch.
IMO, that is dribbled adhesive that was wiped/rubbed off, leaving a wiggle of extra clean de-oxidized surface on the foil pouch.
Thanks, that puts my mind at ease. As well as the lipo's for my ebike I ordered one more smaller Turnigy 2650mAh 11.1v lipo for my electric planes. It is completely dead. The center cell shows zero volts but I can't see any external damage to it at all, I tried in vain to revive it but I think its toast 
At least it was very cheap.
At least it was very cheap.
wasp
10 kW
- Joined
- Apr 3, 2008
- Messages
- 679
bart_dood said:Thanks, that puts my mind at ease. As well as the lipo's for my ebike I ordered one more smaller Turnigy 2650mAh 11.1v lipo for my electric planes. It is completely dead. The center cell shows zero volts but I can't see any external damage to it at all, I tried in vain to revive it but I think its toast
At least it was very cheap.
yes 1 of my 8 5s 5000mah bats came with a dead cell but i was able to revive it chargeing thru balance
i used a blackberry charger and pulsed the ingoing charge
i also picked up a 3s but at 3000mah for like 15 bucks but i use mine for headlight/booster pack
999zip999
100 TW
great I was thinging of going lipo your surport is good I have a 48v2ah ping slim i need more power I like your networking is a great ! It took me 15min. to write plus 5min. comp. warm up.
mwkeefer
1 MW
If you have a pack with a cell reading 0v, what is the total pack voltage? If it's 0 too then it's more than likely a solder tab which has come loose on the little pack...
If you are brave, go outside and carefully remove the shrink wrap... then remove the silicone hitemp end coat where the wires are.. finally inspect each cell in the top mounted PCB for damage to the solder joints... it should be obvious.
I don't think I ever got a 0v actual cell from HK... several where the solder had come undone and a few with dings and dents like yours...
If the cell is really 0v, don't even try to recover that cell, it will be too high of an IR to properly keep the pack in balance.
-Mike
If you are brave, go outside and carefully remove the shrink wrap... then remove the silicone hitemp end coat where the wires are.. finally inspect each cell in the top mounted PCB for damage to the solder joints... it should be obvious.
I don't think I ever got a 0v actual cell from HK... several where the solder had come undone and a few with dings and dents like yours...
If the cell is really 0v, don't even try to recover that cell, it will be too high of an IR to properly keep the pack in balance.
-Mike
Add lipo batteries to the list of leaded childrens toys, sulfur laden drywall and fake baby food...
I finished my bike off good enough to give it a decent ride tonight, I had previously charged the batteries up about 5 miles ago, I got about 7 miles when my voltage was at min so I pedalled the rest of the way (2miles).
When I tried the charge the cells, they didn't seem too flat. When I got to one pack it showed 3-4 volts lower than the rest. I checked the cells in the pack, most are 3.7, one is 0v and one is 2.4 volts....
I boosted the 0v cell up manually via a current controlled PSU and then a little on the 2.4 cell. Now I am balancing and I'll run a full charge and controlled discharge after this.
I suspect one or both of the fault cells will show the fault as soon as a large load is placed on it. Ironically this pack had none of the swirly marks I showed in my pics.
If my battery is dead I'll have to wait weeks for a replacement, how frustrating...
---UPDATE, I've been running through a sequence of balancing the pack and then doing a controlled discharge and the cells seem to be getting better, is there a chance I can rescue this pack? I will keep going and see what happens, if all looks well I'll attempt a longish ride on the set tomorrow evening.
I finished my bike off good enough to give it a decent ride tonight, I had previously charged the batteries up about 5 miles ago, I got about 7 miles when my voltage was at min so I pedalled the rest of the way (2miles).
When I tried the charge the cells, they didn't seem too flat. When I got to one pack it showed 3-4 volts lower than the rest. I checked the cells in the pack, most are 3.7, one is 0v and one is 2.4 volts....
I boosted the 0v cell up manually via a current controlled PSU and then a little on the 2.4 cell. Now I am balancing and I'll run a full charge and controlled discharge after this.
I suspect one or both of the fault cells will show the fault as soon as a large load is placed on it. Ironically this pack had none of the swirly marks I showed in my pics.
If my battery is dead I'll have to wait weeks for a replacement, how frustrating...
---UPDATE, I've been running through a sequence of balancing the pack and then doing a controlled discharge and the cells seem to be getting better, is there a chance I can rescue this pack? I will keep going and see what happens, if all looks well I'll attempt a longish ride on the set tomorrow evening.
liveforphysics
100 TW
bart_dood said:Add lipo batteries to the list of leaded childrens toys, sulfur laden drywall and fake baby food...
I finished my bike off good enough to give it a decent ride tonight, I had previously charged the batteries up about 5 miles ago, I got about 7 miles when my voltage was at min so I pedalled the rest of the way (2miles).
When I tried the charge the cells, they didn't seem too flat. When I got to one pack it showed 3-4 volts lower than the rest. I checked the cells in the pack, most are 3.7, one is 0v and one is 2.4 volts....
I boosted the 0v cell up manually via a current controlled PSU and then a little on the 2.4 cell. Now I am balancing and I'll run a full charge and controlled discharge after this.
I suspect one or both of the fault cells will show the fault as soon as a large load is placed on it. Ironically this pack had none of the swirly marks I showed in my pics.
If my battery is dead I'll have to wait weeks for a replacement, how frustrating...
---UPDATE, I've been running through a sequence of balancing the pack and then doing a controlled discharge and the cells seem to be getting better, is there a chance I can rescue this pack? I will keep going and see what happens, if all looks well I'll attempt a longish ride on the set tomorrow evening.
The problem here was what happened above, when you poked current in a dead cell to bring it up to normal voltage. This isn't NiCd. When a cell reaches a <2.0-2.5v SOC (state of charge), it's having irreversable chemical changes happen. The cell is junk. You can poke it up to whatever voltage you want, but it's only going to be a liability that takes out the other good cells in the pack with it.
Cells need to be matched as closely as possible in Ri and capacity to make a pack work. Once a cell has seen very low voltage, you gotta cull it or it will just take out other cells with it.
Hyena
10 GW
Sounds like bad luck irrespective of those white markings!
Incidently I pulled apart a HK pack once (can't remember if it was turnighy or zippy) and the cell that was DOA reading 0 volts had been marked with pen on side large flat side of the pouch. This wasn't visable as it was in the middle of the pack and I only saw it when I cut the cell out, but it looks like that cell was identified as being sick and the bastards went ahead and used it anyway ( I assume it must have died in transit and they didnt assemble/ship a blatently dead cell)
Incidently I pulled apart a HK pack once (can't remember if it was turnighy or zippy) and the cell that was DOA reading 0 volts had been marked with pen on side large flat side of the pouch. This wasn't visable as it was in the middle of the pack and I only saw it when I cut the cell out, but it looks like that cell was identified as being sick and the bastards went ahead and used it anyway ( I assume it must have died in transit and they didnt assemble/ship a blatently dead cell)
"
The problem here was what happened above, when you poked current in a dead cell to bring it up to normal voltage. This isn't NiCd. When a cell reaches a <2.0-2.5v SOC (state of charge), it's having irreversable chemical changes happen. The cell is junk. You can poke it up to whatever voltage you want, but it's only going to be a liability that takes out the other good cells in the pack with it.
Cells need to be matched as closely as possible in Ri and capacity to make a pack work. Once a cell has seen very low voltage, you gotta cull it or it will just take out other cells with it."
Well what I did was charge the cells up to some reasonable point like 3.7-3.9 with balance on, then do a discharge at a rate of 4 amps. I would watch the bad cell voltage which dropped faster than the rest, I let it drop to 2.9-3.0 volts and then I would run through the balance charge again, back up to 3.7-3.9.
On the first cycle the bad cell would drop quite quick, but after a couple of cycles it got better and better with each cycle. I did a balance charge on the pack to about 4-4.1 volts last night before I went to bed and today I will try a 5 amp discharge, again I'll keep an eye on the bad cell voltage to make sure I don't go under 3.0 volts, I'll time the discharge and measure how long it takes, this will give me an idea of how much capacity is in the faulty cell.
Another indicator is how close the cells are voltage wise as they discharge, I'll watch this too.
The problem here was what happened above, when you poked current in a dead cell to bring it up to normal voltage. This isn't NiCd. When a cell reaches a <2.0-2.5v SOC (state of charge), it's having irreversable chemical changes happen. The cell is junk. You can poke it up to whatever voltage you want, but it's only going to be a liability that takes out the other good cells in the pack with it.
Cells need to be matched as closely as possible in Ri and capacity to make a pack work. Once a cell has seen very low voltage, you gotta cull it or it will just take out other cells with it."
Well what I did was charge the cells up to some reasonable point like 3.7-3.9 with balance on, then do a discharge at a rate of 4 amps. I would watch the bad cell voltage which dropped faster than the rest, I let it drop to 2.9-3.0 volts and then I would run through the balance charge again, back up to 3.7-3.9.
On the first cycle the bad cell would drop quite quick, but after a couple of cycles it got better and better with each cycle. I did a balance charge on the pack to about 4-4.1 volts last night before I went to bed and today I will try a 5 amp discharge, again I'll keep an eye on the bad cell voltage to make sure I don't go under 3.0 volts, I'll time the discharge and measure how long it takes, this will give me an idea of how much capacity is in the faulty cell.
Another indicator is how close the cells are voltage wise as they discharge, I'll watch this too.
Have an emergency exit plan when working with cells like this.. this ain't no joke, when they go.. they really GO!!!!!... .. fun to experiment with.. not to be left unsupervised at any point now or in the future..
.. fun to experiment with.. not to be left unsupervised at any point now or in the future..
liveforphysics
100 TW
bart_dood said:
You're begging for more pack failure my friend. It's damaged. You can always wake a cell back up a bit, but it's damaged. It's not going to match it's buddies, and that means it's going to be taking them down with it in the pack.
Hyena
10 GW
Haven't you seen Lukes destructive lipo videos, I chew on old cells when I run out of chewing gum now :lol:Ypedal said:
Ok so I ran the risk and charged up all the packs in my office at work today under the desk!
The pack with the bad cell in it I did a controlled discharge down to about 3.6 volts each cell and then I charged it back up to 4.2 and it seemed to match the rest, at least voltage wise.
I put them on the bike and strapped on a multimeter connected to the cell directly through the BMS, I didn't want to run the suspect cell less than 3.0 volts.
I ended up riding 14 miles in total, hills and some headwind, these are the voltages of the pack with the questionable cells:
C1 3.79
C2 3.77
C3 3.79
C4 3.67
C5 3.78
C6 3.79
According to my watts up my average power consumption was 305 watt hours, so I'm quite frugal with the juice. Peak amps were around 23-24 amps, my setup is not designed for speed.
The bad cell is C4 and its still off from the rest but not terrible, I am doing another controlled discharge and re-balance again and I'll try it again tomorrow or the day after.
Oh yeah, I ran across a lycra coming the opposite direction, I went another 0.5 miles and then turned around, I caught him up and blew past him, I stopped a mile and a half up the road where I turned around again. His expression was somewhere between anger and confusion!!
The pack with the bad cell in it I did a controlled discharge down to about 3.6 volts each cell and then I charged it back up to 4.2 and it seemed to match the rest, at least voltage wise.
I put them on the bike and strapped on a multimeter connected to the cell directly through the BMS, I didn't want to run the suspect cell less than 3.0 volts.
I ended up riding 14 miles in total, hills and some headwind, these are the voltages of the pack with the questionable cells:
C1 3.79
C2 3.77
C3 3.79
C4 3.67
C5 3.78
C6 3.79
According to my watts up my average power consumption was 305 watt hours, so I'm quite frugal with the juice. Peak amps were around 23-24 amps, my setup is not designed for speed.
The bad cell is C4 and its still off from the rest but not terrible, I am doing another controlled discharge and re-balance again and I'll try it again tomorrow or the day after.
Oh yeah, I ran across a lycra coming the opposite direction, I went another 0.5 miles and then turned around, I caught him up and blew past him, I stopped a mile and a half up the road where I turned around again. His expression was somewhere between anger and confusion!!
liveforphysics
100 TW
Hyena said:
LOL!!! LiPo chewing gum! I love it!
8)
