I partitioned the sdcard in Ubuntu, and then formatted the only partition as LUKS.
Android obviously can't mount it, so it complains about a corrupt sdcard in the system notifications.
Just idling in Android, screen off, wifi off, no SIM card, softwares stopped, consumes about 50% battery power overnight (~8-10 hours).
I you're wondering where your battery is going, best check what your sdcard situation is...