Try Fresh Install
I was having major battery drain with 4.2.1
I read a suggestion on another forum to wipe and reinstall the software from scratch.
It did take nearly an hour with a nearly full 64GB (back-up, erase, reinstall, refill with music and data etc...) but NOW my battery is WAY better, back to how it was when I first bought the phone running 4.0 or 4.1.
Definitely worth a a try if you just 'upgraded' from 4.2 without wiping.
I was having major battery drain with 4.2.1
I read a suggestion on another forum to wipe and reinstall the software from scratch.
It did take nearly an hour with a nearly full 64GB (back-up, erase, reinstall, refill with music and data etc...) but NOW my battery is WAY better, back to how it was when I first bought the phone running 4.0 or 4.1.
Definitely worth a a try if you just 'upgraded' from 4.2 without wiping.