i'm going full OCD on this and i need to know why this is happening.. i have a 6S+ since November, and the battery was kept perfect when on standby. perfect meaning i charge it over night, and could be on 100% if the phone is unused. well, it's now started draining even when i don't touch the phone at all. i lost 4% in a few hours. it's only on WIFI, and i have no background services or anything. what happened? is this has something to do with the IOS (9.2.1)? did i change something by mistake? please help me solve this. thanks.