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| Don't keep fully charged Li-Ion in long term storage, they tend to bulge |
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| JDubU:
RoGeorge: Do not puncture a lithium ion battery pouch under any circumstances!!! :palm: The liquid electrolyte is a lithium fluoride compound that will convert to hydrofluoric acid in the presence of moisture. Hydrofluoric acid is a very dangerous contact poison. It also stops being a battery if any moisture is present in the electrolyte. |
| RoGeorge:
Thanks for the warning. Did that outdoors. Poked a pinhole in the swollen layer only, let the gasses inside escape and squeeze/flatten the battery case, then covered the pinhole with self adhesive Scotch-like tape. The pressure inside was bigger, so I hope not much air entered the battery. Also it's winter here, so even if some air entered the battery, humidity was low. I knew abut nasty HF and avoid inhaling, thought it smelled sweet for a short moment. The sweet smell reminded a little about vintage electronics and tube radios, that smell very close to the sweet smell of very old paper books with yellowish pages. Not the same smell, but close. The battery is a small 300mAh Li-Ion that was so bulged (about 3-4 times its nominal thickness) that I had to remove it from a TEAC mp3 player years ago. It sat bulged like that and unused on a shelf for about 10 years. Charged discharged it before and after deflating. Still working, just that it lost about 1/3 of its capacity over the years. For now I don't plan to reuse that battery. As for the other Li-Ion batteries leftovers from mobile phones, if I will ever reuse them, will let them bulged as they are. No need to deflate since the DIY enclosures can be made big enough. |
| tooki:
--- Quote from: RoGeorge on January 18, 2023, 09:50:56 am ---As for the other Li-Ion batteries leftovers from mobile phones, if I will ever reuse them, will let them bulged as they are. No need to deflate since the DIY enclosures can be made big enough. --- End quote --- Are you insane?!? A swollen lipo pouch belongs in exactly one place: the recycling bin. Continuing to use it is asking for trouble. And when I say trouble, here’s some context: every Apple Store has a battery fire box and basic firefighting equipment in their repair room — and this despite the fact that if a device comes in with a swollen battery, they won’t touch the battery in-store, and instead replace the device and then refurbish the swollen device in a repair depot. (Battery swaps are done in-store if the battery isn’t swollen.) |
| Siwastaja:
--- Quote from: tom66 on January 17, 2023, 11:19:10 pm ---0.1-0.2C charging rate would be about normal for an EV battery (~60kWh pack, 7kW AC charger) --- End quote --- Or even just 2-2.5kW, so 0.05C is perfectly normal. Never heard about the low current SEI thing, either. Have read quite a few papers. |
| james_s:
--- Quote from: SiliconWizard on January 17, 2023, 08:37:26 pm --- --- Quote from: MadScientist on January 17, 2023, 05:38:37 pm ---Very low charge rates should be avoided , ie below 0.2 C as very low charging rates encourages SEI layer growth and hence leads to battery degradation. Chargers at 0.5c then stop charging once full no float etc needed. Track SOC band restart charging at a point --- End quote --- In my experience mentioned earlier, a combination of a 0.1C charge current and automatically recharging the battery, keeping it at 100% most of the time, was a sure recipe for dangerous bulging and killing the batteries. Thus, any UPS system based on Li-ion batteries should definitely be designed appropriately, and there's little surprise lead-acid batteries are still popular in UPSs. --- End quote --- Regular Li-ion is a poor choice for UPS duty. LiFePO4 is a much better choice, they are way more robust and tolerate fully charged storage well. They're a lot harder to make catch fire too.The energy density is lower which limits their use in portable electronics and flying toys but they do get used in power tools. |
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