Let your battery die 100% and stay dead for 5-10 min, then recharge 100% and sit for 5-10 min.
It will allow your phone to read it as a full batt. as opposed to only 50-100% or where ever you began your charge.
I do it once a week and my batt lasts 1 1/2 days on AP mode, but then again I mainly only listen to music at work.
TY for your advice and hopefully mine can help you as well.