Juli Clover, MacRumors:

With the iPhone 15 models that came out last year, Apple added an opt-in battery setting that limits maximum charge to 80 percent. The idea is that never charging the iPhone above 80 percent will increase battery longevity, so I kept my iPhone at that 80 percent limit from September 2023 to now, with no cheating.

My iPhone 15 Pro Max battery level is currently at 94 percent with 299 cycles. For a lot of 2024, my battery level stayed above 97 percent, but it started dropping more rapidly over the last couple of months. I left my iPhone at that 80 percent limit and at no point turned the setting off or tweaked it. [...] You can compare your level battery to mine, but here are a couple other metrics from MacRumors staff that also have an iPhone 15 Pro Max and did not have the battery level limited.

• Current capacity: 87%. Cycles: 329
• Current capacity: 90%. Cycles: 271

My year-old iPhone 15 Pro (not Max) which I simply used every day and charged to 100 percent overnight: max capacity: 89 percent, 344 charge cycles.

I’m so glad Clover ran this test for a year and reported her results, because it backs up my assumption: for most people there’s no practical point to limiting your iPhone’s charging capacity. All you’re doing is preventing yourself from ever enjoying a 100-percent-capacity battery. Let the device manage its own battery. Apple has put a lot of engineering into making that really smart.