This is especially true when you are using your phone to play games or watch videos - both of which are considered to be processor-intensive tasks. These types of tasks can increase the strain on your iPhone's battery because it is simultaneously charging and discharging your device,
To avoid this, people are being told to try and charge their phones when they're less likely to need them
This however can also be very damaging as every iPhone contains a lithium-ion battery that degrades by time. This means that over time, the battery will hold less charge as compared to when it was brand new. And in fact, keeping a battery charged and charging at 100% isn't great for the cell, as it can speed up the degrading process.
Thankfully Apple devices have a built-in feature that can be turned on or off to help boost battery health while you're dozing off. Optimized Battery Charging has been created in a bid to extend the lifespan of your iPhone.
This means that you can limit the wear on your battery by reducing the time your iPhone spends fully charged - ultimately meaning your battery will last you longer. So when Optimized Battery Charging is active, your iPhone will delay charging past 80% – but only in specific situations.