Note: The latest iOS 11.3 beta 5 is already released.
The second iOS 11.3 beta update, sent to developers, presents a new “Battery Health” feature that is intended to provide iOS users with more data about their batteries.
This feature is inside the battery section of the Settings app. It will tell you about the maximum capacity of your battery and whether or not it is operating at peak capacity.
On devices that are working at full battery capacity like the recently released iPhone X, there is no option to turn off the throttling feature that makes iPhones with damaged batteries slow down.
When iOS 11.3 beta is installed, power management will be disabled on all devices, but if the iPhone experiences an unexpected shutdown, power management will automatically turn on.
“Additionally, users can see if the performance management feature that dynamically manages maximum performance to prevent unexpected shutdowns is on and can choose to turn it off. This feature is enabled only after an unexpected shutdown first occurs on a device with a battery that has diminished ability to deliver maximum instantaneous power. This feature applies to iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone SE, iPhone 7, and iPhone 7 Plus.”
Apple said that if users disable the power management feature after its enabled due to a shutdown, they won’t be able to turn it back on manually. It will turn on automatically and that too if it experiences unexpected shutdowns. So it sounds like users may need to turn off the feature more than once on a device that is encountering issues.
The Battery Health feature is highlighted as a Beta feature and Apple will definitely continue to refine and update it during the beta period.