negative voltage on 18650

CBlack

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May 14, 2018
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Start off with, i am not going to be using these....

I have a few 18650 that i finished salvaging today but are showing a negative voltage. Has anyone made these type work again?

Just wondering, not going to use them.

just restating....i am not going to be using them.

CB
 
have the sides switched positive becoming the negative ,negative becoming the positive?

have heard of this happening, never seen it, have tested voltages on batteries usually when tired and have swapped the multi meter probes and gotten negative voltage.

Later floyd
 
Well, if you are certain to have measured using the correct polarity then the cell has probably reversed its polarity by reverse charging. This can happen on batteries that are completely out of balance and should be impossible during normal operation of most devices. Anyway, that basically destroys the cell or renders it useless, so it can go to the bin. No one should try to use it again.
 
Some 18650 format LiFe batteries are reverse polarity. So the button end is the negative.
 
lol at the can you use a meter. i laughed at that one. Yes, I know how, you put it on DC and plug it in the wall, duh! (kidding) they are shot and they got taped up to show they are useless and put in the recycle box.
 
Oooo!!! Experiment time! Connect them up in series and see what you get that way. What kind of a load could you draw from them being reversed. Would you be able to do a capacity test on them in a safe manner (meaning if something explosive happens, everything is contained)

Videos are nice ;)
 
Korishan said:
Oooo!!! Experiment time! Connect them up in series and see what you get that way. What kind of a load could you draw from them being reversed. Would you be able to do a capacity test on them in a safe manner (meaning if something explosive happens, everything is contained)

Videos are nice ;)

well, i guess i can do something as you ask and have helped a lot.
 
I have come across some that are between -0.05 and -0.01V. I put them on a tp4056 charger. They took almost a full day to charge. Then i tested them on an Opus. They always tested okay, but were about half their rated capacity. I saved most of them in a box that I labeled as abused cells....but still might be usefull. I haven't done anything with these cells, but I just tested the voltage of about 1/4 of them and they are above 4.10 V. I am not sure what the hell I am going to do with these cells. I might just leave them, or I might discharge them to below 3.3v per cell and try to figure out a use for them in the future.

-
Ryan
 
CBlack said:
Korishan said:
Oooo!!! Experiment time! Connect them up in series and see what you get that way. What kind of a load could you draw from them being reversed. Would you be able to do a capacity test on them in a safe manner (meaning if something explosive happens, everything is contained)

Videos are nice ;)

well, i guess i can do something as you ask and have helped a lot.

Curiosity would get the better of me and I would have to try. However, I think I would discharge them, and then charge them the right way round. Defiantly in a safe place, probably outside, inside something to contain any possible fire or explosion.

I don't think I would use them after.
 
Geek said:
CBlack said:
Korishan said:
Oooo!!! Experiment time! Connect them up in series and see what you get that way. What kind of a load could you draw from them being reversed. Would you be able to do a capacity test on them in a safe manner (meaning if something explosive happens, everything is contained)

Videos are nice ;)

well, i guess i can do something as you ask and have helped a lot.

Curiosity would get the better of me and I would have to try. However, I think I would discharge them, and then charge them the right way round. Defiantly in a safe place, probably outside, inside something to contain any possible fire or explosion.

I don't think I would use them after.

they will not go into anything that i leave unattended. I am not full on board with playing with them but i did put them to the side for when i find a time to do something. =P
 
I just came across one of these from a Dell 9-cell pack containing Samsung ICR18650-28A which are usually pretty good cells. Six cells came out of the pack @ 3.0-3.7V, two cells at 0V, and this one at -0.63V. I'd guess a bad BMS or a low current short somewhere. I'm gonna play around with it.
 
I've gotten some of those, usually touch in parallel with a good cell a few times and see if the voltage straightens out. If it does, test as normal. They usually don't have more than half their capacity, but seem ok. I have yet to use any of them though.
 
hazSolar said:
I've gotten some of those, usually touch in parallel with a good cell a few times and see if the voltage straightens out. If it does, test as normal. They usually don't have more than half their capacity, but seem ok. I have yet to use any of them though.

I wouldn't use them. Not even for a torch battery. Who knows what is going on inside them. By all means I would experiment with them. But no way would I trust them.
 
I order to have negative voltage cells two things have to happen.
1. A battery is discharged to near 0V (or contains a shorted/0V cell)
2. The cells have uneven capacities/voltages
End result, some cells remain above 0V, some go below (negative voltage).
 
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