I sell iPhones, and the first iPhone 18 Pro Max sold at my store was a 256GB black model with a physical SIM. The customer was initially happy, but after a few days said the battery lasted only about 19 hours—roughly the same as their iPhone 15 Pro Max. Apple lists up to 43 hours under its testing conditions, so even allowing for real-world differences, I expected closer to 30 hours or more. Besides reducing screen brightness or enabling Low Power Mode, could setup activity or an iOS issue be causing unusually high battery drain?
4 Answers
The phone is probably still doing a lot of work in the background. Restoring the backup, downloading apps, indexing photos and messages, setting up Siri, and signing back into services can all use extra power. It may take about a week, and sometimes longer for search and Siri indexing, before battery life becomes representative. A new phone also tends to get heavier-than-usual use while the owner explores it.
Have the customer check the Battery settings page after the phone has settled down and compare which apps or activities are using the most power. A weak 5G signal, frequent 5G use, high outdoor brightness, navigation, video, and background syncing can all make a major difference. The newer display may also run brighter at the same percentage setting, so comparing brightness by percentage alone is misleading.
I would avoid judging the battery after only a few days. Let setup and indexing finish, then restart the phone and monitor it for another day or two. If the drain remains unusually high after that, check for a software update and look for an app or cellular connection that is constantly active in the battery statistics.
The advertised 43-hour figure is a controlled test result, not a normal mixed-use estimate. It generally assumes things like offline video playback and ideal conditions. In everyday use, getting through a full day is a more realistic expectation, while 19 hours could still be reasonable depending on screen time, cellular signal, gaming, video, and background activity.
I understand that the number comes from testing, but the difference between 43 hours and roughly 19 hours still seems larger than expected. I was hoping for at least around 30 hours in ordinary use.