There is definitely something causing drain on 4.2, I wouldn't say my battery life on my nexus 7 completely sucks, but forget getting 2 days out of a charge now! Before the update my battery life was epic, we're talking maybe a 5% drain and hour during heavy use, and a percent drain a day on standby. Now while in use my battery drains fast, to the point you can just watch the percentage go down while in use, and on standby a percent an hour or more. I always kept auto brightness on, plenty of widgets, and gps on at all times before. Now I've shut all that stuff off for no noticeable gain.
It's not just me either, my friend has a Gnex and he also complains about heavy battery drain. Really I love the update other than this, I really hope they patch it, thus far only thing they've cared about is the December bug
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