I always turn on the airplane mode on my phone running Android 5.0.2 before I go to bed. It's working great as there is at most 10% drop in battery percentage(usually around 6%). I have noticed a problem with my phone and I think it shouldn't happen(this is my first phone). When there is no cellular reception, my phone will try hard to find one and the battery starts draining(which is normal), but it still tries to search for reception even I enable airplane mode, which is the odd part. It is okay since my phone is able to receive reception after a few minutes.
Few weeks ago, my phone completely died overnight with airplane mode enabled. I am sure I have closed all running apps, and I didn't have GPS and Bluetooth on. I tried to search online but I found no clue.
This happened again today. I could feel that my phone was warmer than usual and I knew something must have went wrong.
Is there a way to prevent my phone from searching for cellular reception on airplane mode? Or is my phone faulty? I already have
Always allow scanning - Let Google Location Service and other applications scan for Wi-Fi networks, even when Wi-Fi is off disabled long time ago but I don't think it has anything to do with my problem.