Apple Watch Ultra battery drains rapidly

To understand Apple Watch performance and its relation to your battery, see:

Apple Watch - Battery - Apple

Apple Watch Battery and Performance - Apple Support

“Battery life” is the amount of time your device runs before it needs to be recharged. “Battery lifespan” is the amount of time your battery lasts until it needs to be replaced. Maximize both and you’ll get the most out of your Apple devices, no matter which ones you own. See the "Tips for Apple Watch" section in:

Batteries - Maximizing Performance - Apple

If the battery drains too fast after an update, see all the replies to:

Battery Drain since watchos 7.4 - Apple Community

WatchOS 7.5 battery drain - Apple Community

FWIW, in some cases, unpairing the watch, completely erasing it, then pairing and restoring the backup will resolve the battery draining issue after an update. (Simply unpairing and pairing again may not work.)

Unpair and erase your Apple Watch - Apple Support

Also, some people have found that simply waiting a few days after an update resolves the battery draining problem.

Were you able to figure out what was causing your battery drain? I am having the same issue. Usually get 2 days of use. Yesterday went from 100 percent to 0 in 12 hours.

I have a similar issue in the last couple of days. My Ultra2 is brand new. Initially use barely touched 20%. I go to the gym regularly, some running but not heavy. By contrast today at 10.30am the Ultra2 watch is already at 62%. No gym or running today, I am at my desk working. Longer battery life was one of the key draws for this watch.

I have reset and cleared APPS on both phone and Watch. Have not done the un-paring. I will see how the next day goes before trying the erase and pairing.

Not with certainty. But two things (1) the walkie talkie function had been activated. And (2) In the end I did a factory reset to be safe and has been fine since

update seems to be loosing around 2% an hour.