I am used to charge my watch every 2 days. Just noticed it says “3%” after I charged and updated it 6 hours ago.
I have no clue about Watch, but on iPhones it’s not uncommon that after the update a lot of load still occurs on the device as various apps and services do their housekeeping. I’ve seen rather significant power draw (usually accompanied by a rather warm iPhone) well after updating and unplugging from power.
A simple way to tell might just be to recharge and wait to see if this behavior persists in the following days.
Update: It usually takes less than 2 hours for a 100% charge. Now it is about 80% after 2 hours.
I would restart the watch if you haven’t already. If this doesn’t seem to help, the pretty standard advice if you notice heavy battery drain that doesn’t go away is to un-pair the watch and pair it again.
I did see one other potential solution that seems pretty involved, but this would only be the case if you have Catalina installed on a Mac, have noticed that the process TrustedPeersHelper is consuming a lot of CPU, and also have battery drain in other iOS devices. I’ll link the blog post just so you can see it, but I wouldn’t necessarily follow the 12 step procedure at the bottom of the post until you’ve exhausted everything else.
95% after about 4 hours. I’ll let it go to 100%, restart it and see what happens.
99% after 10 hours. I restarted it and will let you know what is happening.
Not directly relevant, but this Apple Support page recommends restarting the paired iPhone if there are watch update issues:
(might be less traumatic than the 12 steps!)
Also I use the Battery Grapher app to monitor battery performance. I have just updated my watch to 6.2.1 so will look for differences via that app.
Keep in mind that most lithium-ion charging solutions (including Apple’s) slow down as the battery approaches full. They use a “constant-current/constant-voltage (CC/CV) controlled” system.
The way this works is that charging starts in “constant current” mode where the input voltage is selected such that the current flow into the battery is fixed at some amount that is specified by the battery manufacturer and hard-coded into the battery’s controller chip. In order to maintain constant current, the voltage will increase as the battery charges.
When the charging voltage reaches some maximum (again, determined by battery chemistry and coded into its controller chip), the charger will switch to “constant voltage” mode, where the voltage remains fixed at that maximum. During this time, the current flow into the battery will go down over time, approaching zero when the battery is fully charged.
Looks like we are heading back to normal: down to 54% after 24 hours. (It was a plain restart)