Why does the iphone 5 battery drain quickly under the following conditions (more in the table of contents)?

Question

iPhone

Iphone 5 (just 5)
iOS 9.3
In 7 hours and 45 minutes, the phone is discharged from 100% to 83%.
All this time the phone was not used.
This is fine?
All applications in the background are disabled
Wi-fi is disabled
Mobile Internet as well as 3G is disabled
Geolocation is disabled
Parallax is disabled
All auto-updates of applications are disabled
Airdrop is disabled
Screen brightness is set to 50%
Standard mail downloads data only in manual mode
In push notifications, only calls, sms, mail , appstore
The battery is normal. The other iphone 5 does not have such a fast discharge

Answer 1

there are many problems this
1 sat on the charger for a long time
2 the iPhone is not original
3 the iPhone has a weak battery
4 there are many applications of games

Answer 2

maybe you have a bad network signal and the phone is constantly looking for it