Is there any more technical information about the iPad/iPhone charge management feature?
It’s explained right below the option in settings by Apple: “To reduce battery agin, iPhone learns from your daily charging routine so it can wait to finish charging past 80% until you need to use it.”

It works best when you have a set schedule for yourself, as when you are unpredictable, it tends to just charge at 100% all the time.

Charging to 80% prolongs the life of lithium-ion batteries by nearly double as charging to 80% uses 50% of a life-cycle and charging the remains 20% (the slowest part of charging) uses the remaining 50% of the life-cycle.

Apple goes more into depth in their “Batteries: Why Lithium Ion” page