overdischarged wina LiFePO4 50ah cell

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ltosolini   100 mW

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overdischarged wina LiFePO4 50ah cell

Post by ltosolini » Oct 21 2018 3:45pm

Today I badly screwed up.... No BMS and overestimated my pack charge!
On the way home I was noticing lack of thrust in my scooter powered by 20s LiFePO4.
As soon as I reached home, I measured that one cell was 0 Volt, this is a cell I knew it was the weakest link.
Immediately I put the pack on charge and noticed that this cell was slowly picking up, now after roughly 2hours at 5A charge it is at 3.15Volt.

Do you think I killed this poor cell or there is a chance I can still use it even if at reduced capacity?

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dogman dan   100 GW

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Re: overdischarged wina LiFePO4 50ah cell

Post by dogman dan » Oct 24 2018 7:59am

I would think its been hurt for sure. But it might come back with diminished capacity, and less ability to stand a 1c discharge.


All you can do is charge it and see. if it self discharges too much though, its done. I mean eventual self discharge to 0v. It would be somewhat usable if it can still hold a charge a half a volt off the others overnight discharge.

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fechter   100 GW

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Re: overdischarged wina LiFePO4 50ah cell

Post by fechter » Oct 24 2018 10:44am

I've heard that permanent damage starts when a cell gets down to 2.0v. Overdischarge to the point of reversing will kill almost any cell chemistry.

But I guess it won't hurt to try charging it and see what happens. The cell may behave like it has a resistor across it and have a hard time reaching normal voltage. Keep the charge current low and stop if anything starts getting warm. If you can reach 3.65v, then let it rest for a while and measure the voltage later. If it drops a lot, it's a bad sign.
"One test is worth a thousand opinions"

999zip999   100 GW

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Re: overdischarged wina LiFePO4 50ah cell

Post by 999zip999 » Oct 24 2018 2:12pm

Never let any cell over charge 3.7v is the max. And after 3.45v- 3.5v it will race to a high voltage very fast. Meaning when charging becarefull of all cells. 50ah cell will take a long time. How old is the battery ?

ltosolini   100 mW

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Re: overdischarged wina LiFePO4 50ah cell

Post by ltosolini » Nov 04 2018 5:04pm

So I removed immediately the cell that went down to 0 Volt; it is a wina lifepo4 50ah. It is also swelling.
I managed to resuscitate it and so I charged it 10ah which is 20% of capacity and it held the charge for 1 week then it went down to 2.7Volt. Then I tried a full charge and I could push 28ah which is not bad, almost 60% capacity! Let’s see now if it can hold the charge.... Anyway I dont want to put it back in my scooter especially for the swelling.

ltosolini   100 mW

100 mW
Posts: 41
Joined: Apr 17 2016 3:07pm

Re: overdischarged wina LiFePO4 50ah cell

Post by ltosolini » Nov 04 2018 5:13pm

Anyway even after this bad experience I am still convinced that it is better without BMS.
Lets say that I destryed this cell, this is 60 Euro but I managed to get home safe and fast with my scooter even with this single cell at 0 Volt.
If I had the BMS, the scooter would had stopped in the middle of a busy road, I would have had to call a taxi to go home and probably an emergency vehicle to bring the scooter home: that is sure more than 60 Euro!

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