watchOS 9 has a feature called ‘Optimized Battery Charging’ that slows down power consumption via machine learning.
Apple Watch users running watchOS 9 can make the most of their smart watches with the introduction of the feature. The app learns each user’s habit to improve battery health and determines the best time to charge the Apple Watch to full.
‘Optimized Battery Charging’ can be activated by putting the device in a charger overnight. The Apple Watch will have its battery charged up to 80% at the fastest speed, then slow down and ‘float’ when the time the user usually picks up the watch arrives. Then, charging speed ramps up to 100% just before the user picks up their Apple Watch for use throughout the day.
Battery optimization was first seen in the iPhone, and now appears on Apple Watch models via watchOS 9. It can be turned off by going to Settings, then Battery and Battery Health.