Default Battery Calibration

hello guys. i think that my battery is draining way too fast than it shouldn't be, my phone is now 9 months old. when i charge my phone last night, i saw that the battery percentage is on 92%. i just opened a game, just to check something. when i closed the game, the battery is now 100%. i think the game that i opened does not even exceed to 5mins.

do you think that my battery is not working properly? cause when i watch movies, approximately, 25-30% only of the battery discharges, but now it discharges up to 45-50%.

by the way, im on a locked bootloader running the existenz black version.

is there any way on how can i prolong my battery life? i use greenify (donated version).

how to calibrate the battery?

thanks guys.
I do not fear computers. I fear the lack of them.
- Isaac Asimov -
Xperia SP C5303
Rooted, Locked Bootloader, Stock Kernel