My apple watch ultra won't charge passed 80%.
With out the battery optimized battery charger limit. So when is off still don’t charge 100%
Apple Watch Ultra 2, watchOS 10
Did you also disable the Optimized Charge Limit feature?
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To turn off Optimized Charge Limit on Apple Watch Series 9 or Apple Watch Ultra and later:
- Open the Settings app on your watch.
- Scroll down, then tap Battery.
- Tap Battery Health.
- Turn off Optimized Charge Limit.
- Choose Turn Off Until Tomorrow or Turn Off.
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copied from: About Optimized Battery Charging on your Apple Watch - Apple Support
Also force restarting the Apple Watch Ultra 2 after disabling the feature may also help: