Apple Watch Battery Life
After update IOS 16.3, my Apple Watch battery Drain out … before update can use at least 20 hours , after update just can last for 6 hours . Any solution for this?
Apple Watch Series 8, watchOS 9
Force restart your watch i.e. press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when you see the Apple logo.
Then make sure to turn off background app refresh and check walkie talkie is not accidentally turned on.
Test the watch for a day.
Then if still no better
Unpair the watch and then pair it again.
Unpair and erase your Apple Watch – Apple Support (UK)
Set up your Apple Watch – Apple Support (UK)
If it still discharges unpair it and pair it again without restoring the backup.
Check that the iPhone is not using any security apps or VPN that can affect apps on the Watch. You don't need any of them and they can be incompatible with iOS16 on the phone.
see also
Apple Watch - Battery - Apple (UK)
Batteries - Maximising Performance - Apple (UK)
How to check your Apple Watch battery fo… - Apple Community