voltage suddenly dropping on AW IMR 18490s

[cracoucax]

It's now the third time that I witness a very strange behaviour from my IMR 18500s:

- I'm vaping, seems like the voltage is getting a little low but no less than 3.5v for sure (I can always tell when the battery is between 3.7 and 3.6, always change at 3.6 max)
- Next drag, suddenly there is almost no vapor coming out
- I measure the voltage, it comes at 2.5 or a little more
- While i'm measuring and keeping the prongs on the battery, the DMM shows that the voltage is going up, slowly by .1v increments. Maybe .1v every two seconds. The battery is not hot or anything.

Happened to me a few days ago, i had left the battery alone cause i feared recharging it. I just checked it again, it's now at 3.5v.

I'm kinda baffled by this, is this a known possible behaviour of IMR cells under certain circumstances ?
Maybe they're simply dead ? They've certainly been put though some use.

Thank you

 

[cracoucax]

Forgot to add: if I do recharge the battery, it will charge normally.
I'm not sure yet if it will have the same symptom directly after the charge cause i've got 3 of them and don't use them all that much most of the time.
I guess i should mark them and keep testing.

 

[Ryedan]

Once these cells get to 3.5V with no load they are almost fully discharged. The drop from there to 2.5V will not take long specially with a 18490 and even quicker with a 18350, but it should not happen after one drag.

The change back to 3.5 I have never seen, but if I discharge to 2.5V by mistake I immediately put the battery on charge. Leaving them discharged damages them. I have the feeling it's a worn out battery. How many charge cycles are on this cell and what resistance attys are you using when this happens?

 

[cracoucax]

Thank you, forgot to come back to this.

Yes i suppose they're just worn out.
Hard to say how many cycles it went through, i'd say 150 cycles as a rough estimate.
They've been used between 0.6 and 0.8 ohms mostly.