There is a secret code in the dialer, *#0228#, that resets the battery callibration completely, killing the phone straight to 0% and asking you to charge to full. I last used it on my S4 and went from 2h SOT to 4.5h SOT, but it also completely screwed up the battery callibration, which meant the phone would go down quickly in charge, but "self charge" and recover in standby. It meant, e.g. used from 75% to 65% in about 15 minutes, which is a discharge rate of 1.5 minute per %, but then recover 5% if I leave it for a while, which would make the discharge rate an actual 3+ minutes per %. Is there any way to get the benefits of battery reset without this?