Ultra Watch series 1 battery drain
After the latest update 10.1 to the Apple Watch OS my watch battery drains supers fast
Apple Watch Ultra
If the battery drains too fast after an update, see all the replies to:
has anyone had battery issues with the 10… - Apple Community
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.
Also see:
Apple Watch battery drain - the ultimate … - Apple Community