Apple watch series 9 battery drain
My apple watch series 9 has some serious battery problems that my watch last for only 6-7 hours after fully charged and apple claims 18 hours of battery life
Apple Watch Series 9, watchOS 10
Did you try to force restart your watch?
Restart Apple Watch - Apple Support
If this does not help, unpairing and pairing the Apple Watch again seemed to solve the issue for other users.
Unpair and erase your Apple Watch - Apple Support
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