On iOS 13, Apple added a feature they called optimized battery charging (Optimized Battery Charging) in the battery settings section. Basically, it will help extend your iPhone battery life by not fully charging the battery regularly. The algorithm will learn the process used to identify the time to use the device to fully charge.
As described by Apple, the system will charge up to 80% of the battery and wait until the user needs to use the device to charge it fully. The nature of Li-ion batteries will be prone to aging when the battery is overheated and always keep a full charge for a long time. Apple said that this feature will reduce the time that the iPhone uses to fully charge the battery.
Through the process of using the device, iPhone will learn the habit of using your computer to optimize. For example, you usually charge overnight, before plugging in a charger or putting on a wireless charging dock, the iPhone will charge until it is full. In iOS 13, when the optimization feature is turned on, the device will only charge up to 80% and wait for users to use the device to charge 100%.
The problem with Li-ion batteries lies in the so-called charge cycle. The more charging cycles are, the easier it will be for batteries and for bottles and capacity loss. Not only does charging from 0 to 100% count as one cycle when you charge from 80 to 100% in 5 times, it is also counted as 1 cycle. A cycle is counted as a full battery discharge (100%).
In addition, if you regularly charge the device is not good, you just plug the charger to always stay around 100%, it can be overheating and reduce battery life. Therefore to prevent this situation, the system will stop charging for a while and then continue charging.
Remember, if you leave the phone charging and not using it, the battery is still wasted, not kept at 100%. For example, if you leave overnight and the device fully charged, then the battery will be depleted to 98 or 95%, then the device will continue charging 100%, the process goes on all night. So you've lost the charging cycle overnight, for example, charging from 95% to 100% is 5% of 1 cycle, 20 times is 1 cycle.
The solution that experts and battery manufacturers offer is a 40-80 rule. Ie do not use the battery to below 40% as little as possible and do not charge more than 80%. But the problem is that users always want to fill the battery 100% after unplugging it, so they can use it for as long as possible, or use it all day. The solution Apple offers on iOS 13 is to please both.
The device will charge 80% and stop waiting, the algorithm will recognize the habit of waking up and picking up the device to estimate the time to start charging again to 100%. That means the iPhone will not charge and recharge all night, leading to overheating, affecting battery life and waking up, we still have 100% battery to use.