I charged then to 4.20 then probably didn’t check them for weeks. When I did they were all bang on 4.16 volts. I’m wondering if it’s just better on the cells to just stop charging at 4.16 volts since by the time I get around to using them they will already have dropped to 4.16 probably anyway. I keep a set in my lights and I always have 1 backup set for each light that I keep charged incase I am going to need to take an extra set with me.