Charge Li-Ion to 4.21V and that's that. The rest (over 4.25) is overcharging. If you see the voltages charged - it's clearly outside the spec. Using a voltage -

Charge Li-Ion to 4.21V and that's that. The rest (over 4.25) is overcharging. If you see the voltages charged - it's clearly outside the spec. Using a voltage -> percentage table is just a gimmick that has managed to stick. The entire discussion is littered with percentages that aside being non-scientific, mean absolutely nothing at all as they are not comparable. Most tool batteries, vacuum and mower robots - all charge below 4.2V - yet phones (and some laptops) are special. Morealso charging it to '80%' means little as we have no clue what charge profile: constant voltage [how high]/current is used and when.