Why does my battery drain a little faster at some point?

[AC Question]

My battery drains a little faster at some point

When I charge my Android device to a 100% it's good until it reaches 85% it drains a little faster than the normal and the drain continue until it reaches 50% and it's normal from 49% to 0% I don't know why the battery drain from 85% to 50% faster than normal
BTW I wasn't using my cell phone much I was using it and then turn it off for a week or something and then use it again because I have another phone and I was charging it turned off. I'm not rooted and some people say I should calibrate my battery but I don't know how, so please tell what's causing this problem and how to fix it?
I'm running Android KitKat 4.4.2
My device is Alcatel Idol x+

 

[B. Diddy]

Re: My battery drains a little faster at some point

Welcome to Android Central! Charge up to 100%, then let it drain to 20-30% with normal usage, without charging in between. Then show us:

1. The main Settings>Battery screen.
2. The fullscreen battery graph screen (which shows Awake time and Cell Signal Strength).
3. The Screen category (to see total Screen On time).
4. The Cell Standby category, if present (to see Time Without Signal).

http://forums.androidcentral.com/am...ide-how-post-screenshots-android-central.html