What is the best practice when it comes to charging the iPhone so as to maintain the battery health for as long as possible? Is there any specific % to which the iPhone must be charged to keep the battery healthy for long?
iPhone 12
Apple provides some support documents on battery use you will find useful:
Batteries - Maximizing Performance
In the last of these documents Apple recommends that you keep your device up to date: Apple software updates often include advanced energy-saving technologies
There are all these little things that **might** help at the margins, but there really is nothing that's easy. If there were some automatic setting to limit the maximum charge level, then I'd say go for it, but there isn't. Other than that, keep it cool (cases trap in heat) and never let it get into a "deep discharge" state, which will be well below 0%. You would have to leave it there for a long time after it refuses to turn on for that to happen.
iPhone Battery charging
