battery life after upgrade

Hello juli9,

Thank you for reaching out in Apple Support Communities. With your battery concern, we recommend to see if the battery on your Apple Watch needs to be serviced. On the Apple Watch, please go to Settings > Battery > Battery Health. If you see a message that the battery needs to be serviced, then you'll want to contact Apple Support to review your service options.

Now if the Battery Health is in a good state, then we suggest to adjust the settings to help optimize the battery performance. Here's how:

"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."

These steps are outlined in this helpful article for you to reference: Batteries - Maximizing Performance - Apple

Following these steps may help.

Kind regards.