I was having a similar problem with my Google Nexus 7 recently. I'd unplug it and leave it overnight sleep/idle and it would be down 20+ % and warm to boot ... it was doing SOMETHING.
I read a lot about disabling various functions etc. but in the end what fixed my issue was clearing the Android Cache Partition. Now when I leave the tablet overnight it is perhaps down 2-3%. I didn't have to disable anything, I didn't have to do a factory reset.
The troubleshooter in me is annoyed that I don't know WHY this solved the problem but it clearly did as my battery life has changed drastically and I'm using the tabled exactly the same way I have been previously.
I have a theory ... but it is just a theory. Right after I cleared the Android Cache Partition two Google apps/services updated (one was calendar the other escapes me). My theory is that there was something Google specific, stored in the cache, that was continually trying to update and failing to do so, and that this is what was chewing the battery.
In my mind this also explains why so many people say that if you do a factory reset your battery life problems will be fixed. When you do a factory reset on of the things that happens is your Android Cache Partition is cleared.
There are lots of places where you can get instructions on how to clear the Android Cache Partition. It doesn't 'cost' you anything as the device still has your apps and menus, and it may help you greatly.
-Cam