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Can lithium ion / lithium poly "recover" after getting weak?
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Siwastaja:

--- Quote from: SilverSolder on May 24, 2020, 12:44:06 pm ---I attached the research article found by Big Clive for reference.

--- End quote ---

It's a very interesting paper but I really can't see how it supports a view that overdischarging only causes damage below 0V. I can see how someone who does not normally read scientific papers can make this wrong conclusion, though. (Didn't watch the Big Clive video, maybe he's not claiming that, but it seems he was being understood that way.)

SEI destruction and release of gases alone is a huge issue.
ConKbot:
Sounds like the behavior of a severely imbalanced series pack that is slowly balancing itself at the top of charge. One cell is grossly over-discharged, the rest are ok. You charge it, it takes a little bit of charge, the full cells hit 4.2v, charge terminates.  As it discharges, the low cell hits cutoff and it stops running.  Balancing as maintenance only needs a few mA of current, so there isn't a point in a built-in balancer that can correct a severe imbalance in a few hours, so as it spends more and more hours at top of charge, the more time the balancers have to get everything in order.
ConKbot:

--- Quote from: Siwastaja on May 24, 2020, 04:37:03 pm ---
--- Quote from: SilverSolder on May 24, 2020, 12:44:06 pm ---I attached the research article found by Big Clive for reference.

--- End quote ---

It's a very interesting paper but I really can't see how it supports a view that overdischarging only causes damage below 0V. I can see how someone who does not normally read scientific papers can make this wrong conclusion, though. (Didn't watch the Big Clive video, maybe he's not claiming that, but it seems he was being understood that way.)

SEI destruction and release of gases alone is a huge issue.

--- End quote ---

People after cheap garbage love to hand-wave all sorts of danger. I've seen videos showing people how to reset the CID on the top of 18650s, or how to trick chargers into recharging 0V cells by paralleling them with a good cell in a cradle, just slam a 0V cell with a few amps to charge, sure, sounds like a fantastic idea. Stuff like this is why LG is flat out like 'don't use bare cells, its too dangerous for you smooth brains'  there is danger associated with lithium ion batteries, but buried away in a pack its protected, but some people love to just forcibly align holes in the swiss-cheese model.  Reset a CID on a cell that has experienced some serious overstress, put it in a cradle to charge at a few A from dead, solder on leads so they can put it in a pack of mismatched cells.

Ok now here comes the anecdotes.
SilverSolder:

--- Quote from: Siwastaja on May 24, 2020, 04:37:03 pm ---
--- Quote from: SilverSolder on May 24, 2020, 12:44:06 pm ---I attached the research article found by Big Clive for reference.

--- End quote ---

It's a very interesting paper but I really can't see how it supports a view that overdischarging only causes damage below 0V. I can see how someone who does not normally read scientific papers can make this wrong conclusion, though. (Didn't watch the Big Clive video, maybe he's not claiming that, but it seems he was being understood that way.)

SEI destruction and release of gases alone is a huge issue.

--- End quote ---

Is this what causes some lithium ion batteries to swell up?
edpalmer42:

--- Quote from: SilverSolder on May 24, 2020, 11:46:14 am ---
So the management chip actually "learns" the size of the battery - it doesn't just stop at some preset voltage (and other criteria)?


--- End quote ---

AFAIK, the charging circuit always includes a low-value shunt resistor.  Measure the voltage across that and you've got the current, both charge and discharge.  Measuring the voltage is easy.  The chip has some kind of clock signal so that gives it time.  Now it can measure energy, both charging and discharging.  It does have voltage limits that it limits the battery to.  But it likely doesn't know how big the battery is.  That's why you run through a few charge/discharge cycles so it can learn the battery size.  By measuring the number of AH in from the charger and out to the load, it gains an approximation of the battery's SOC (State of Charge).

Over time, the battery degrades so it's important to occasionally run the battery down so the chip can learn the battery's current (  ;) ) condition.
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