How bad is charging CV voltage overshoot to 4.233Vpc for NMC/INR cells?

[cj0]

Having Samsung 18650-35E INR/NMC I noticed that the charger sometimes overshoot the voltage level to 4.22 Vpc for more then 1 second every 30 minutes while charging.

For 13s the Uac=30mV and Upp=0.3V. Factoring that into the equation there will be per cell: (0.33*0.5=0.165)/13 = 0.013 + 4.22 = 4.233 volts peaks on the poles of these cells.

The datasheet specifies 4.2 ± 0.05V.

How bad are these frequent voltage overshoots near the 4.25 volts for INR/NMC chemistry (knowing that 4.1 Vpc and even 4.05 Vpc is better for cycle life but sometime I need maximum range)?

Something to worry about? Or a total non-issue of zero concern?

 

[sunshine_eggo]

Not many NMC users here.

I have premium Panasonic NMC harvested from plug-in hybrid vehicles, and I would take steps to avoid over-shooting 4.20V ever. In fact, when I go to 100%, I don't exceed 4.18V.

 

[offgridandy]

I have NMC cells from a Peugot 205 battery, made by CATL but I only charge (from the genny) to 4V. My PV can charge up to 4.1V . I would have thought that the time the event lasts is the critical point. For literally a second may not be harmful. If the battery is nearly fully charged how many Amps are actually flowing at that point?

I would approach the manufacturer for advice on such a specific situation.