No, never heard of that. When I test lights, I like using 4.19V to 4.21V at a starting point. Never heard anyone say that off the charger, 4.15V is the same as 4.20V - just doesn't ring a bell. Guess there's still a lot I don't know, though I sure would like some tech ref info on this, again, because I've never seen that written here on BLF, least I can recall, and I'd think that would be something important to me.