Apple added a feature called optimized battery charging in the battery settings section on iOS 13. 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 fully charge the device.
The weakness of Lithium-ion Batteries
“iPhone learns your daily charging routine so it can wait to finish charging past 80% until you need to use it.”Apple
And by doing so, iPhone can extend your battery’s lifespan. The Li-ion batteries will be damaged when the battery is overheated for charging for a long time. Apple said that this feature will reduce the charging time of the iPhone.
When using the device, iPhone will learn your habit 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. When the optimization feature is 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 you charge your battery, the more damage on your battery. Charging from 0 to 100% count as one cycle, if 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 keep charging your device to keep it around 100%, it may overheat and reduce battery life. Therefore to prevent this situation, the system will stop charging for a while and then continue charging when needed.
Remember, if you leave the phone charging, the battery is still wasted. For example, if you leave your phone charging overnight though it was full, the battery will be depleted to 98 or 95%.
The Solution: The 40-80 Rule
The solution that experts and battery manufacturers offer is a 40-80 rule. That is not to pin down 40% as little as possible and not exceed 80% charged. 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. The solution Apple offers on iOS 13 can satisfy 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.