Discharge while in airplane mode (with image) Something weird happened today morning. I charged my phone yesterday night and gone to sleep after 2 hours or so. When I woke up, my phone was at %30 charge and I was pretty confused. Because before going to sleep, I just opened my morning alarm, closed wi-fi and set the phone to airplane mode.

After checking the battery info, I got something like this, 

http://i.imgur.com/7FEn7cF.png

Clearly, my phone discharged linearly while I sleep. I am using a samsung s4.
What is the reason behind this? Is this problem related to the phone or android ?
Download wakelock detector from the google play store, if it happens again open wakelock detector and it will show you cpu and partial wakelocks (will only show partial wakelocks if you enable advanced mode), if the largest cpu wakelcok is "PowerManagerServiceWakelock" this means the largest wakelock is the combination of all the items listed in partial wakelcocks.
I would suggest (if it happens again) looking for anything over 7% and doing a web search for the wakelock name, and seeing what you can find.

If it doesn't happen again, problem solved.

I would also recommend you don't kill background processes, instead install greenify (play store) which blocks the processes you select from starting.

Other than this we can't tell you the reason due to androids default battery diagnostics not being very good.

It is most probably the software, if you download Nova battery tester and run it, it will tell you your battery capacity, and you can then compare this to what it should be to verify it isn't a hardware fault.