The Battery Health status of an iPhone 6 or an iPhone 6 Plus running iOS 11.3 might be unavailable after a battery replacement.
To prevent this from happening, follow the instructions below immediately after performing a battery replacement – do not allow the device to boot up before completing these instructions:
Connect device to a power adapter and hold down home button to boot it to Recovery Mode. Important: The first bootup must be in Recovery Mode.
iPhone 6 should briefly display Apple logo, and then Connect to iTunes screen.
iPhone 6 Plus should briefly display Apple logo, and will then display a blank black screen but the backlight will remain on.
Using a timer, allow the device to remain in Recovery Mode for at least 1 minute while connected to charger.
After 1 minute, restart the device by pressing and holding both home button and sleep/wake buttons until you see the Apple logo, then release the buttons.
Allow the iPhone to start up normally.
With the customer, check 'Battery Health' in Settings to demonstrate it is displaying maximum capacity following the battery replacement.
If the Battery Health status shows an unknown, explain that the new battery is fully functional, even though the Battery Health status shows that the battery health is unable to be determined and nothing is displayed for Maximum Capacity. This occurs sometimes after a battery replacement on an iPhone 6 or iPhone 6 Plus running iOS 11.3. Apple is aware of this issue, and it will be addressed in an upcoming software update.
If the customer wants to reset the Battery Health status immediately, they can use the steps below:
Make sure the customer has a recent backup of their iPhone by checking Settings > iCloud > iCloud Backup > Last Successful Backup.
If the customer uses iTunes to back up the iPhone, they should connect to iTunes and choose 'Back Up Now'.
Once the backup is complete, erase the iPhone by tapping Settings > General > Reset > Erase All Contents and Settings.
Once the device has been erased, restore the iPhone from the backup.
If a customer wants to reset the Battery Health status immediately, but does not want to erase the device and set it up from a backup, then replace the battery again carefully following the replacement instructions above.