Apple Watch Stops Charging at 80%

I found this thread started by Rossintheoc asking about the same problem I have.

It charges green however the circle makes… - Apple Community

The thread is locked so posting the answer I found here.

This is a feature called Optimized Battery Charging About Optimized Battery Charging on your Apple Watch - Apple Support

You can make your watch charge to full before it's scheduled to do so:

1. Make sure that your Apple Watch is connected to its charger.
2. Tap your watch to show the charging screen, then tap the circle with the green or yellow charging icon.
3. Tap Charge to Full Now.