Is 91% battery health normal for iPhone 15 Pro?

My opinion.....

Charge Limits are more of a gimmick than anything else. The battery will still charge to 100% "occasionally" even when you use Charge Limits. When I tried Charge Limits, I found that "occasionally" was sometimes 3 times a month. Other users report similar results while other users report less. So, no real advantage there since the battery would charge to 100% anyway multiple times a month.

When you use Charge Limits, you have to charge the battery more often as well, so more wear and tear on the ports and connectors.

Somehow, users got by just fine for 15+ years without Charge Limits. I think Apple added the option for Charge Limits to give users the impression that they were actually doing something to control battery performance when it really was not necessary.

After trying Charge Limits for a few months, I now ignore those settings and use Optimized Battery Charging. I start each day with the battery at 100% so it will now make it all the way through the day without additional charging needed.

But, what's "best" for me may not be "best" for you. At a little over 350 Charge Cycles, the Maximum Capacity of the battery on my iPhone 15 is at 94%.....a bit above "average".

At 300 Cycles, the Battery Health should be at about 94%, so the battery is doing OK, but declining a bit faster than normal.

Normal use and wear are causing your “non-issue “. Batteries are hardware and have components that deteriorate over time. Nothing lasts forever.