I recently moved from a Nexus 4 to a Nexus 5X

Can anyone explain to me why a battery would drain on a phone that is turned off - on a recent work trip to Auckland I took both phones with me, and the Nexus 4 was in my bag turned off (was at 100% battery when it was turned off). When I arrived, I turned on the N4 and was greeted with 32% battery. I fully charged it and left it on for 3 days (did not use) and during that time (with no WiFi/network activity) the battery went down to 91%. For the flight home, the phone was turned off and when I got home I turned the phone on and had 24% battery.

At home connected to WiFi, it will drop about 10% per day when not being used.

/confused