I d k why but from starting this has been a major issue in my phone..the battery doesnt feels to be of 6000mah.it gives performance of 4000mah battery.my phone only give 5 to 6hours sot without any sort of gaming and this is really disappointing as battery was one the major factors that made me purchase this phone..this issues needs to be fix by asus asap otheriwise its an serious issue..so called 6000mah battery then seems to be of name sake only if this continues...