How can I improve battery life on my iPhone 15 Pro?

I recently had my Iphone 15 pro replaced. In the last 2 weeks I have been to an apple store or have been on with support 5 times. All due to battery life that goes 100% to 20% in a few hours. My old Iphone 15 pro did not have this issue but as I read through the community it seems many of us are having the same problem. Apple tells me my battery is fine, but a battery on a new phone the last only 6 hours while idle is not fine. It seems to me Apple has the problem and needs to address this.

[Re-Titled by Moderator]