I think it learns your schedule of when you charge and use your phone. If I routinely go to bed at 11PM and put my phone on the wireless charger, wake up at 6:00AM and start using it, it will adjust the time that it begins charging (and maybe the rate?) so that it is ready and charged slightly before my wakeup time. If I touch my phone in the middle of the night to see what time it is it usually has a notification that optimized charging has delayed charging so you phone will be charged at 6:00AM (or something to that effect...). I think it keeps it from sitting at 100% trickle charging all night. I have also seen if I put it back on the charger with 97% or something close, it will not begin charging again.I never fully understood the optimal charging part other than the phone learns your habits and does it that way to extend battery life. I am a heavy user so I guess my battery being at 71% capacity is normal. In fact I may not get the battery changed just yet. I have to plug in midday to give it a boost then at night it charges while I sleep. But we will see.