I noticed that my phone will not drop in battery percentage when memory usage shows 2.1 or 2.5GB and phone is unused (e.g. when you sleep) However battery will steadily drop if memory use is 3/3.5 GB or above when you double-tap to switch off the screen.
It seems that broken apps occupy space in memory and continue to run in the background and drains your battery while you're sleeping. So always do a memory clear or click optimise in Device Care.
Otherwise just switch off wifi because Google always-on trackers also drain battery significantly and give a bad name to Samsung.
