Why Is My Phone Battery Discharging So Quickly. You can choose whether to start this mode manually or have the phone do it automatically. Delete unused accounts and apps.

Open the Settings app. Thanks for the details provided in your post Ill be glad to help you. The other 20 percent of the time its the storage on your phone which can drain battery power.
So before you decide to replace the battery of your iPhone try to update all the apps on your iPhone.
For example imagine your battery is fully charged and you use Safari to browse the news for an hour. So youve carried out the tests and come to the conclusion that your iPhone suffers from a battery drain issue. After that hour has passed you shouldnt have put a significant dent in your battery percentage. If you do not have an answer to your why is my phone battery draining so fast question the above guide should it for you and provide you with the fixes you need to resolve the issue on your Android based.

