Giant battery suck
Just found this forum because of the same problem and thought I'd add my experience.
SGH I777: The last day or so battery drain became enormous (no exaggeration); power was being consumed faster than could be recharged!
Under settings - battery, I found that Gmail was using 60% of the power, and that even when I turned it off, killed it, force-stopped it, whatever I tried! Powering down and removing battery for 20 sec or so didn't change anything either.
I then decided to uninstall Gmail whereupon the system automatically reinstalled what was called the "factory version". After this Gmail's power consumption was very low for a while, but then it edged back up to ~24%, however, better than the 60% I was getting.