Apple Watch battery drain - the ultimate diagnosis.

So you have tried all the restart, unpair, pair again stuff that normally fixes Watch battery drain in Apple Watch uses a LOT of battery - Apple Community but it still discharges.

This suggests it could be an incompatibility in the software on your iPhone and the Watch or it could be a corrupt iOS installation, This will diagnose either

-Unpair and erase the Watch (a) - see resources below.

-Backup the iphone (b)

-Restore iphone to factory settings (c). You should end up with the Hello screen on the iphone.

-Set up the iphone as new without restoring the backup. (d)

-Install only your essential email accounts, no extra software, no social media, nothing else. (aka "vanilla minimal")

-In Settings General, About, rename the phone to “Test iPhone” to avoid corrupting any automatic iCloud Backup

-Pair the Watch to the iphone (e)

-Run them both like that for 24 hours and see how long the battery lasts. Hopefully you will be pleasantly surprised.

Only when that test is over can you repeat the three actions (a) to unpair, (c) to wipe then (d) to set up the phone but restoring the original backup this time. then (e) to pair the Watch again

Scenario 1. If the Watch lasts much longer the first time (vanilla minimal) than the second time with restored software then it proves it is software on the iPhone causing it.

In that case you have two choices.

1.You could export as much data as possible such as un-sync’d photos and documents out of the phone to a place of safety such as iCloud before repeating the restore and set up as new process, (a) (c) (d) (e) then build up the phone again from scratch. Obviously no security or VPN software.

Or

2.You could systematically uninstall software and any profiles until the battery will last a full day,

Scenario 2. If the Watch battery lasts much longer after both setups - ie with minimal software and lasts a lot longer with the restored backup then it suggests it was a corrupt iOS installation. You have fixed it - great news!

Scenario 3. The Apple Watch battery continues to drain abnormally fast after the first (vanilla minimal) configuration. Your watch's battery may be defective. Consider the age and expected service life of the battery, and arrange to get the battery checked by Apple Service.

You can test for self discharge (f)

Resources you need: (Allow a couple of hours for each session)

(a) Unpair and erase your Apple Watch – Apple Support (UK)

(b) How to back up your iPhone, iPad, and iPod touch - Apple Support 

(c) turn off Find My and Stolen Device protection then Restore your iPhone, iPad, or iPod to factory settings - Apple Support

(d) Set up your iPhone or iPad - Apple Support

(e) Set up your Apple Watch – Apple Support (UK)

(f) How to check your Apple Watch battery fo… - Apple Community