Apple Watch Ultra battery draining quickly post installation of new OS

Thanks for posting in the Apple Support Communities Anujkohli41,

If your Apple Watch isn't holding a charge as long as you expect, the following information may provide a solution for you:

Adjust your settings.

There are a few ways you can preserve battery life on your Apple Watch:

* During running and walking workouts, turn on Power Saving Mode to disable the heart rate sensor. To do this, open the Apple Watch app on iPhone, go to My Watch > Workout, and turn on Power Saving Mode. Note that when the heart rate sensor is off, calorie burn calculations may not be as accurate.

* For longer workouts, you can choose to use a Bluetooth chest strap instead of the built-in heart rate sensor. To pair the Bluetooth chest strap with your watch, make sure the strap is in pairing mode, then open Settings on Apple Watch, select Bluetooth, and choose from the list of Health Devices.

* If you’re very active with your hands and your watch display turns on more than you think it should, you can prevent the display from turning on every time you raise your wrist. Open Settings on Apple Watch, select General, select Wake Screen, and turn Wake Screen on Wrist Raise off. When you want to turn on the display, just tap it or press the Digital Crown.

* Disabling Bluetooth on your iPhone increases the battery drain on your Apple Watch. For more power-efficient communication between the devices, keep Bluetooth enabled on iPhone.

Enable Low Power Mode.

Introduced with watchOS 9, Low Power Mode is an easy way to extend the battery life of your Apple Watch when needed, for example if you’re on a long flight or find yourself without your charger for the night. You can enable it by swiping up to Control Center and tapping on the battery percentage, or by going to Settings > Battery. 

Low Power Mode prolongs battery life by turning off always-on display, limiting the cellular and Wi-Fi connections of your Apple Watch, and disabling background sensor readings including heart rate measurements, high and low heart rate notifications, irregular rhythm notifications, and blood oxygen measurements.

When not connected to your iPhone, your Apple Watch will attempt to retrieve notifications approximately once an hour. When your Apple Watch battery reaches 80% charge Low Power Mode automatically switches off.

View Battery Usage information

To view your battery usage and charging history, open the Settings app on your Apple Watch and go to Battery.

Plug in and power on your computer to charge your Apple Watch.

If you want to charge from your computer, make sure it is plugged in and powered on when you’re using it to charge your Apple Watch via USB. If your Apple Watch is connected to a computer that’s turned off or is in sleep or standby mode, the Apple Watch battery may drain.

If your Apple Watch battery needs service, use Apple or an authorized service provider.

Maximizing Battery Life and Lifespan - Tips for Apple Watch

Cheers!

I also had this problem, and saw some advice on a different thread to remove all 3rd party apps. I didn‘t go that far, but I did remove the vast majority, only keeping the ones I use somewhat regularly. That fixed the problem immediately for me. I don‘t know which one(s) were causing the issue, but it makes sense that something like that would be the cause, both because it‘s widespread but not universal and because Apple wouldn‘t necessarily have tested them all pre-release. iOS had a similar issue recently with Instagram and a couple of other apps rapidly draining iPhone batteries.