Windows Phone users, especially Lumia 920 and 925 users are facing a problem where they experience sudden battery drain for no apparent reason. It is due to stuck process where a process is stuck in the background and continues to use CPU cycles. Using Visual studio to do analysis we see that the phone OS is stuck at 50% and you get a warning of high CPU cycles.

Symptoms of the problem.

Overheating

Hot back plate

Left metal banding gets unbearably hot

Cannot charge phone as fast

To produce the problem again, follow these steps.

Put phone in airplane mode

Shutdown phone

wait 2 mins. and start up phone

once phone starts up you will realize phone is no longer heating up.

Put on a radio that establishes a data connection.

Os then gets stuck in a loop.

Phone begins to heat up.

Putting phone back in airplane mode does not help as the phone is now stuck. Following the steps above again will reliably reproduce the problem.

I have had my 920 replaced twice by AT&T and all three phones had/have the same problem – overheating and rapid battery drain. Needless to say, I’ve been following the issue closely. There are thousands of posts across multiple threads discussing this issue. Unfortunately, the problem is convoluted by the many possible variables; 3d party apps, core apps, settings, antennas, signal strength, GPS, background tasks, etc., etc. Yes it’s true that some apps may increase battery drain and yes, turning off some background tasks or location services may increase battery life, but this is not the battery drain problem plaguing the Nokia 920 and Lumia 925.

The 920 / 925 suffer from some sort of firmware/software loop which causes the CPU to overheat and rapidly drain the battery (10 – 20% per hour). The trigger seems to be any data connection. Third party apps may trigger the problem, but they are NOT the root cause. A factory reset unit (with only the base apps installed) will still suffer from the problem. The problem can occur while the phone is totally idle. Battery saver mode does not resolve the problem. Airplane mode does not resolve the problem. The only way to stop the loop/overheating/battery drain is to turn off the phone, let it cool down, then reboot.

Nokia and Microsoft refuse to acknowledge there is any problem.