| General > General Technical Chat |
| Can lithium ion / lithium poly "recover" after getting weak? |
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| SilverSolder:
I have an ancient Lithium Ion power bank here, the USB type you might use to charge a phone. It is optimistically rated at 20,000mAh new. It had been "misplaced" in my cave, for several years. I found it with minimal remaining charge, but not stone dead. When I then recharged it the first time, it would only accept about 1,000mAh. So I thought great, it's almost dead, it might work to power an Arduino or something like that... so that's what I put it to use for. The use case means it gets drained until it shuts down, every time, before getting recharged. Except... it has powered the Arduino longer and longer... every time I recharge it, it seems to accept more and more juice. With the last recharge, it accepted 10,397mAh... which is probably getting close to whatever real capacity it had in the first place... I knew that new Li-Ion batteries have to go through a few cycles to build up to full capacity... but I didn't think this was something the battery could "forget" again? Is it expected that Li-Ion can "recover" some capability after standing around, with a bit of "massage" like this? |
| NiHaoMike:
Most likely the SOC estimation is way off and it's slowly correcting itself each cycle. |
| Siwastaja:
Some management chip doing some random things, nothing to do with the cells. |
| Peabody:
I don't think new lithium batteries need to be cycled to reach full potential. But the algorithm that many lithium chargers follow for a deeply discharged battery is to only apply 1/10 of the full charging current until the cell is back above 3V. That might explain your initial low charge rate. But I don't have an explanation for any gradual increase after that. |
| edpalmer42:
I agree with the other posters that the management chip is relearning the actual capacity of the cells. I'm a bit surprised that it's taking multiple cycles. You should monitor that pack very carefully. AFAIK, this is the scenario that causes Lithium batteries to burst into flames. The battery discharges further than is safe and is damaged in the process. Then a charger that isn't as smart as it should be comes along and tries to recharge the damaged battery. The result is smoke, flames and shattered nerves! |
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