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Don't keep fully charged Li-Ion in long term storage, they tend to bulge

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SiliconWizard:

--- Quote from: james_s on January 13, 2023, 06:32:16 pm ---
--- Quote from: RoGeorge on January 13, 2023, 10:03:54 am ---Next question would be if anybody experimented with puncturing the skin of the battery with a small hole (without touching the internals) in order to deflate it, then covering the small hole with some adhesive tape to seal it against air.

--- End quote ---

Yes people have tried this. There is not really any point, when the battery has puffed up it has been damaged, poking a hole in it certainly isn't going to improve safety. These batteries are known for catching fire if abused, do you really want to risk burning your house down?

--- End quote ---

Yeah, this is one of those horrible suggestions that should come with a mention in large and bold: DON'T TRY THIS AT HOME.

NiHaoMike:
Could reuse the cell in some outdoor application where it won't be much of a big deal if it catches fire.

Miti:

--- Quote from: RoGeorge on January 13, 2023, 10:03:54 am ---I've never seen or heard of igniting Li-Ion in the circle of known people, yet everybody I know uses phones, tablets, laptops, cameras and so on.  :-//

I would like to keep using the bulged batteries for small current circuits, weather station, hallway LED lights with moving sensors, things like that where the low self discharge rate of Li-Ion will make them last much longer than the NiMH cells.

Anybody tried to deflate the Li-Ion then keep using them?

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You don’t want to be the first one to experience this in your circle of people.
Besides the toxic gases, which I understand are quite nasty, metallic lithium and oxygen don’t go well together. In a new battery there shouldn’t be any lithium in metallic form but in an old used and abused battery, you could have some deposited on the electrodes. Letting oxygen inside the pouch is not the best thing you can do. Depending on the size of the batteries that could be a problem.
I have multiple RC fliers and I had puffed up batteries of various sizes over time and I never tried to puncture one intentionally, I just continued to use the least puffy for some light testing and disposed of them when  they were too puffy.

Edit: You may ask what’s too puffy? When the pouch is flapping in the wind when the battery is at room temperature, it is not too puffy for me. When it becomes a balloon all the time, it’s time to retire that battery.
Another thing, all the RC Li chargers have a storage mode that brings the batteries to about 3.8V.

Miti:

--- Quote from: Siwastaja on January 13, 2023, 11:15:41 am ---Only if the cells are faulty / total crap. Normally, self discharge is nearly zero already at 50%SoC and just gets lower. Case in point, when I measured self-discharge in dozens of cells, I deliberately discharged cells to tad below 0% SoC but they did not lose any more charge during 1.5 year test period.

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I just found some old Varta Li-Po batteries in a pile of junk at work after an inventory cleanup. Brand new, never used but made in 2009. They all measure zero volts at the output of the protection board, the battery itself between 2.2 and 2.3V. They are small 300mAh. I fully changed one and checked its capacity down to 3V at 50mA and at 100mA. The result in both cases was around 350mAh. Not bad for a 14yo battery.
I wouldn’t normally recharge a big battery that discharged this low, but at this size I don’t think there’s any risk.

RoGeorge:
Maybe I should just let them be without puncturing the bulged ones.  The reason to deflate them is mostly to make them fit back into whatever device they use to power.  DIY circuits can be made with enough space for any battery, so no need to deflate them.

Another question, I've noticed these days a case where a 15+ years 1750mAh Li-Ion accumulated about 30% more charge when charged at a very slow peace, at 0.01C than when charged normally.  Charging them that slow won't heat the battery, and would simplify the electronics a lot for a multi channel CC-CV charger I want to build.

Would it be a bad idea to charge a Li-Ion very slow, for 3-5 days non-stop using CC-CV?

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