Originally Posted by PunishedSnake
Usually I do a factory reset after such an upgrade
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More often than not, a factory reset will take care of battery issues after a major OS upgrade. I'm not sure if it's left-over system files or something about the "upgrading" of existing apps during the process, but I've had to do it with both my Galaxy S3 and Nexus 7 2012. Not every upgrade, mind you, but with one or two.