The recent iPhone Pro Max models released by Apple have seen significant improvements in battery performance. Indeed, it’s hard to find anyone who owns an iPhone 12 Pro Max or 13 Pro Max complaining about battery life, and even the iPhone 11 Pro Max can last all day on a single charge. However, currently, some iPhone users seem to be noticing a decline in battery quality since updating to iOS 16.

Specifically, tweets reflecting the declining battery usage, such as: “The reason I bought Pro Max was for the battery life, but everything changed after updating to iOS 16!”; “From having enough battery to last 3 days to needing to recharge after using the phone for 5 to 7 hours!” are increasingly appearing.
Users on another social media platform, Reddit, have also started sharing their less-than-favorable experiences after installing iOS 16: “My battery drain is higher than normal! I work in an office and don’t need my iPhone 13 Pro Max much. On iOS 15, I usually come home with 85%-90% left, but with iOS 16, it’s around 65%-75%. I don’t think I use my phone that much. I only use it to scroll through news and send emails or browse Instagram during breaks. But all of this is within about an hour. I probably wouldn’t notice the change if there was only a 5% difference, but from what I’ve experienced, it’s nearly a 20% drop despite not changing my phone usage habits.”
Another Reddit user stated: “The battery of my iPhone 13 Pro Max is draining alarmingly, from 11-12 hours down to just 7 hours and extremely slow when using FaceTime or PiP. I plan to revert on July 15, but first, I need some advice.”
Moreover, the iOS 16.0.2 update seemingly does not affect battery performance on iPhone 13 and later models.

To be fair, battery life is always expected to decrease slightly during the first update to a new operating system version, as the device is running in the background to ensure it operates smoothly with the newly installed OS. This even happens after major updates, such as the previously problematic update with iOS 16. However, the reality is that two weeks have passed, and any adjustments made in the background should have been completed.
Additionally, some suspect that Apple is intentionally increasing battery drain to encourage more iPhone users to upgrade to the new iPhone 14 line.
Users should note that the iOS 16.0.2 update does not include any fixes for battery issues on iPhones. But if this problem continues, the pressure on Apple to address whatever is causing battery drain on iPhones will be significant./.
According to Phone Aerena