Here’s Apple’s explanation of what you can expect if you enable the setting:

When you choose 80% Limit, your iPhone will charge up to about 80 percent and then stop charging. If the battery charge level gets down to 75 percent, charging will resume until your battery charge level reaches about 80 percent again.

As we’ve been testing the setting on our review devices, we noticed that our phones have been charging past 80 percent anyway. That’s apparently something you can expect to see happen occasionally, according to Apple.

With 80% Limit enabled, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates.

This new option joins the existing Optimized Battery Charging setting that has been on Apple devices for a few years. That setting will hold the battery charge at 80 percent before bringing it up to full before it thinks you’ll need to use the phone, based on your usage patterns. Apple also just released iOS 17.0.2 for the iPhone 15 series, and we’re installing it now to see if charging actually starts to hover around 80 percent with the new setting enabled.