18650 stored at 4.2

Found a small power bank I forgot I still had and it was stored at 4.2v for a year. Can I still either open it and use tge cell in something else or would it be better to recycle the whole thing.
I tried to Google the bad parts of storing charged cells and didn't find anything other than reduced capacity.

Afkane said:

Found a small power bank I forgot I still had and it was stored at 4.2v for a year. Can I still either open it and use tge cell in something else or would it be better to recycle the whole thing.
I tried to Google the bad parts of storing charged cells and didn't find anything other than reduced capacity.

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Nothing unsafe about that if parasitic drain didn't suck the energy out of those cells inside, down to below ~2.5v.

As you note, there might be some reduced capacity.

I would want to check the voltage somehow, or charge something of known capacity to get an idea of what's left inside.

Chris

Wait... A year later it still stores 4.2V?! I am impressed

vadimax said:

Wait... A year later it still stores 4.2V?! I am impressed

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Whoops, forgot to make it clear that it was put away at 4.2 but I have no idea what its at now. If I open it up and it tests higher than 2.5 I could reuse it or could storing it at full charge is unsafe regardless. it sounds like it's ok to use and capacity might be reduced.

Many of us keep our li-ion cells fully charged when not in use (not much point having your cells at 3.6V in readiness for a blackout). It is likely that lifespan of the cell will be reduced in a similar way that more charging cycles will also reduce lifespan. If you replace your cells every few years I would not be concerned (as long as the cell is used within its parameters).

Like others have said it's fine. All my cells are kept at 4.2v. I have 18650s that are still over 85% rated capacity that I've had for four years which I procured from a tool battery pack. Being they're 1300mah cells is say they're pretty old. And I've put them through hundreds of cycles. And some that don't get used much. Just did a capacity test on an efest 18500. Been dirty at full charge for probably 18 months. Was at resting voltage of 4.14. Discharged at 1A and measured 989mah. Rated capacity 1100mah