Many people think that fast charging can drastically affect battery life, but it's actually only a small amount. If an expensive smartphone has been purchased but does not want to take advantage of the attractive features why buy? Based on my observations, this happens frequently among iPhone users again who often worry about the battery health percentage. In the future, you will definitely use fast charging because Apple started warning if the iPhone is charging slowly.
In iOS 18 Developer Beta 1, a Reddit user received a warning in his iPhone battery settings section displaying a “Slow Charger” warning when using a 5W charger on the iPhone 15 Pro Max. There is a special link to the Apple Support page but the article has not yet been published so the exact reason why this warning is displayed is unclear.
Since the iPhone 8, although Apple still provides a 5W charger, all iPhones have started to support Power Delivery fast charging from 18W up to 27W. Fast charging technology now has smarts in managing heat when charging, electricity flow and even the chip stops charging. Even very slow charging can cause the device to heat up and cause unwanted damage.
The best solution is firstly don't use a USB-A to USB-C/Lightning cable instead use USB-C to USB-C/Lightning with a USB-C charger that supports PD/GaN/MFi. Also avoid charging through a laptop unless the laptop has a built-in power bank feature. Let's all look forward to the Apple Support update to find out more about this matter.