The Samsung Galaxy Note 5 is some of the best phablet Samsung had offered, but that does not mean that it is problem free. Some users reported that the Samsung Galaxy Note 5 refuses to go to sleep when they leave it idle and because if that, their battery is getting drained.
Some users reported that the battery would drop about 15% at night when they leave they phone idling. After checking with the battery usage, it would show that the device has been awake and not sleeping like it should which explain why the battery is draining off faster than expected.
Other believe that it might not be the Note 5’s problem but the connection issue stating that the battery will drain faster if the user is connected faster WiFi connection.
Some users suggest installing apps like the GSam Battery Monitor to see which app is the one that is draining the battery while other said that the issue went away when they rooted the device.