Apple watch ultra stop charge at 80%

It's possible that there could be a problem with the battery or with the OS on your Apple Watch Ultra. Here are some steps you can take to troubleshoot the issue:

1. Restart your Apple Watch: Try restarting your watch by pressing and holding the side button until the Power Off slider appears. Then, drag the slider to turn off your device. Press and hold the side button again until the Apple logo appears to turn your watch back on.
2. Update your Apple Watch: Check if there is any available software update for your watch. Go to the Watch app on your iPhone, tap on General > Software Update. If there is an update available, follow the on-screen instructions to download and install it.
3. Check the charging cable and power source: Make sure that the charging cable is properly plugged into both your Apple Watch and the power source. Try using a different power source, such as a different USB port on your computer or a different wall adapter.
4. Reset your Apple Watch: If the issue persists, you may need to reset your Apple Watch to its factory settings. This will erase all data and settings from your device, so make sure to backup your watch before doing this. Go to the Watch app on your iPhone, tap on General > Reset > Erase All Content and Settings. Follow the on-screen instructions to complete the reset process.