New iPhone battery drains when turned off
I just got a brand new iPhone 13 mini. I only use it for texts, calls and the camera. I charged it to 100% yesterday. When I turned it off last night it was at 94%. When I turned it on this morning it had gone down to 89%. I checked the battery activity for the night and there was none. So why has the battery drained by 5% overnight when the phone had been turned off?
I have done all the battery life hacks to try and help. Which I did last night. The only thing I haven't done is updated the firmware or done a factory reset.
I set up the phone by transferring from my old iPhone 7. Not a fresh setup.
The phone is currently on iOS 15.0.
Any ideas would be great.
Thanks.
iPhone 13 mini, iOS 15