How to fix IPhone 15 Pro battery draining fast?

Those posting on this site might be interested in my experience with Apple support regarding my battery problem. First of all my phone is a plain vanilla iPhone purchased on September 2023 when it first came out. I am in the habit of turning off cellular and wifi and powering down the phone before bed. If I charge the phone to 100%, the following morning when I turn it back on it is still at 100% as are all my other Apple battery powered devices. After a few months though I noticed when I turned the phone back on it had drained by about 15% and  throughout the day the phone was discharging at a faster rate than what I was used to regardless if I was using it or not.  I then called Apple support and was lucky enough to be connected with a motivated and knowledgeable individual who was firmly committed to resolving my issue. She initially performed a remote diagnostic on the phone and battery and said everything checked out OK but when I told her the battery was discharging even when the phone was powered down she admitted that was not normal and immediately escalated my issue to engineering. Over the next several weeks my support advisor performed additional diagnostics sending the data back to engineering. After approximately one month, she told me that engineering identified a hardware defect with the phone and wanted to try to repair it. I was given a choice of sending it to the repair center or bringing it to an Apple store. I was also given $150 to spend on Apple accessories for my incovenience. Living close to an Apple store I elected the latter. Here is where the  fun starts. The “genius” and store manager both performed the same simple diagnostic my support advisor initially did and said there was nothin wrong with the phone and that the behavior I described was normal . When I inquired why their opinion differed from Apple’s engineering department they just blew me off. I went home and again called Apple support and requested to send the phone to the Apple repair center. The box arrived in 2 days. After only one week my phone was returned to me and is now as good as new. No more battery drain when powered down and lasting 2.5 days with my light use. The repair information indicated that they not only had to replace the battery but also the TrueDepth Camera and the Rear System. Bottom line:

1. Don’t go to the Apple store for repairs.

2. Call Apple support and hope that you reach a support advisor that is knowledgable and willing to go the extra mile to resolve your issue. My experience in the past has been mixed.

This may help --> Prolong and Maximise Battery Performance … - Apple Community

Mine keep draining also. I do not think they care if it gets fixed. It just gets worse. This is my first iPhone, and I got a 15 Prox Max. I couldn't be more disappointed. I dislike it, and it's not worth the money, so I am glad it was free. When I can, I am going to offload it. There were too many problems, and I could not do half the things I could and needed to do with my Android. Plus, I didn't have to pay for every app, and there was a vast selection of free widgets. I can't even get a good alarm clock on this phone. The clock that comes with it, and the only one, was so low last night I didn't hear it and the volume was turned up high. Not to my liking at all. I wish I had not bought it.

I agree with you. I chatted w/ support and did all the steps on the article they sent to me. I charged my phone to 100%. All I’ve done is read on the kindle app for 1hour and it’s drained 25%. The battery on my iPhone 11 worked better.

i also has an expectation of a better performing phone. Especially for $1000. So sad.

I upgraded from 12 mini to 15 early June and have been extremely disappointed. Their website says 20 hours of video playback. Testing at best I can get 12.5%. An hour phone call battery drained 10%. I expected poor performance on my 12, it was three years old and at 80%. But I sure wish I had just returned the 15 and put a new battery in my 12.

I've had three calls with techs and they contradict each other. It is sad.

But what did you do for a phone while yours was being repaired?

Purchased a prepaid phone for $29 from Straight Talk