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So I made a stupid mistake tonight. I was charging a few spare headway 38120 cells and inadvertently let two of them reach 3.85v for about 5 minutes. I immediately discharged them back to about 3.45v. Do you guys think they are irreparably damaged and should be tossed?
Thanks in advance for your opinions
 

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Any damage should be minimal. Lithium Iron Phosphate cells are far more resilient to over voltage than Lithium Ion. In fact, in the early days some manufacturers recommended high voltage charging (like as high as 4V IIRC) before they realized that it didn't add any appreciable energy and it reduced cycle life.
 

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Lithium Iron Phosphate cells are far more resilient to over voltage than Lithium Ion.
But just to be clear, LiFePO4 cells are lithium-ion cells; LiFePO4 (or LFP) is just one of the many Li-ion electrode chemistries. I can believe that LFP is more resilient than NMC (Nissan, LG Chem) or NCA (Panasonic); this is just a terminology issue.
 

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So I made a stupid mistake tonight. I was charging a few spare headway 38120 cells and inadvertently let two of them reach 3.85v for about 5 minutes. I immediately discharged them back to about 3.45v. Do you guys think they are irreparably damaged and should be tossed?
Thanks in advance for your opinions
All Lithium Ion cells experience degradation above 3.7 Volts.
Degradation is mainly characterized by irreversible capacity loss (capacity fade) and voltage loss, i.e. increase in cell impedance. Degradation is caused by fatigue during cell operation (charge/discharge cycles) as well as ageing phenomena occurring at rest conditions.

Capacity losses are partially caused by the formation of lithium dendrites.

If you know what the capacity was before then you simply need to do a charge and discharge while measuring current and quantify the capacity loss by the over voltage.


In my opinion it will have done nothing measurable since the charge procedure is just one way to charge a battery and not written in stone. The actual voltage of the cell is 3.38 Volts.
 
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