Is 90% battery health on iPhone 15 Plus concerning?

Jay_vardhan1 wrote:

My iPhone 15 plus drop battery health to 90% in 11 months is it safe

Yes, it’s “safe”, but for an iPhone 15 it might be a little low because the 15 has been tested by Apple to remain above 80% for 1,000 full charge cycles (it was 500 cycles for older models). But it depends a lot on your usage pattern and how you manage the battery.

For your iPhone 15 you have an even more useful measure: cycle count. So divide your current cycle count by 50 and subtract the result from 100%, and that is what your expected maximum capacity should be.

The absolute best way to get maximum use on a charge, as well as slow the decline of battery capacity long term is to enable Optimized Battery Charging (Settings/Battery/Battery Health) and charge the device overnight, every night. The battery will fast charge to 80%, then pause. During the nighttime pause the phone will use mains power instead of battery power, allowing the battery to “rest”, and thus reducing the need to charge the battery quite as often. The phone will resume charging to reach 100% when you are ready to use your phone; it will “learn” your usage pattern. If you enable iCloud Backup (Settings/[your name]/iCloud - iCloud Backup) the phone will back up overnight also, assuring that you can never lose more than the current day’s updates. Here's more information→About Optimized Battery Charging on your iPhone - Apple Support

Jay_vardhan1 wrote:

My iPhone 15 plus drop battery health to 90% in 11 months is it safe

That sounds normal.

All rechargeable batteries will lose capacity over time. That doesn't make them unsafe.