[AC Question]

I did a system update on my HTC One, and battery is draining. When i looked battery history, Cell Standby is responsible for 93% of usage with the screen off. This new. Any advice?

[Rukbat]

1) Restart into recovery and wipe the system cache. (DO NOT do a factory reset - that resets the phone to the way it was when it came out of the box - no downloaded apps, no data, no files.) Clearing system cache just deletes the temporary files the last version was using - they're useless after the update.

2) Tap the graph to get to the next page. What does your Mobile signal line look like? If it's all broken, you have a bad mobile signal and the phone is going to keep trying to find it - eating tons of battery. Bring it to your carrier for assistance if that happens. (The modem may not have updated properly, they may be experiencing tower failures in your area, the phone might have chosen just this time to have some hardware failure - it not possible to tell from here.