With the steps below, you can easily set an optimized charging limit for your Apple Watch Ultra to maintain optimal performance and extend battery life of your device.
On your iPhone, find and open the "watch" app. Make sure your apple watch is connected to your iPhone.
In the main interface of the "watch" app, slide the screen to find and tap the "Battery" option.
On the Battery page, scroll to the bottom and click Battery Health.
On the Battery Health page, you'll see a switch called Optimize Charging. Click this switch to enable it.
When Optimized Charging is enabled, you can set a charging cap. This will help you avoid charging the battery to full capacity for long periods of time, thereby extending battery life. After setting the upper limit, your Apple Watch Ultra will automatically stop charging when the set value is reached, and automatically complete the remaining charging process when needed.