So, I had one megadrain (going to bed with 50% of battery and waking up with an empty phone) on day 2 of owning my Nokia Lumia 920 and I didn't know what it was. The next day I changed some things (brightness to low, deinstalled apps like Gmaps and some other things I wouldn't be using dailly) and I never had a drain anymore. Then 2 weeks later I installed Battery Meter and Gmaps (again) and I could litterally see the percentages of my battery getting lower every 5 minutes. I had the Gmaps background task blocked and Latitude disabled. I deinstalled Gmaps again and the battery drain stopped. Yesterday I thought..... I might need Google Maps to find places, because Nokia Maps doesnt find everything and guess what happened after I installed Gmaps....... massive battery drain!! I don't know if other people have this problem too, but Gmaps is definitely a no go on my phone.
I bought Gmaps Pro and immediately my battery started draining again. But what I always saw was that it mentioned a problem with the compass and that it had to be recalibrated. I disabled the compass and the battery drain stopped! It's bizar that this did the trick as I have the background process blocked, live tiles and latitude disabled. But I'm happy that I have Google Maps on my phone without the battery drain 
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