iMarc

Apple have recently introduced a new featured called “Optimized Charge Limit” which aims to lengthen the lifespan of the battery embedded within an Apple Watch:

From Apple’s support pages:

With watchOS 10, this feature is available on Apple Watch SE, Apple Watch Series 6 and later, and Apple Watch Ultra and later. Optimized Charge Limit learns from your daily usage to determine when to charge to an optimized limit and when to allow a full charge. Optimized Charge Limit is on by default when you set up your Apple Watch.

Apple support documentation

The feature builds on the existing optimised charging feature found on the Apple Watch and most other Apple devices. Now though, if the watch notices that you typically only use, say 30% of the battery capacity on a daily basis, but still charge it every night, then instead of charging it to 100% it might stop short at say, 70% instead. Lithium iron batteries don’t like to be charged above 80% or below 20%. Doing so frequently will shorten the lifespan of batteries, making a dreaded replacement necessary.

Hopefully the algorithm employed by Apple is smart enough to work out your routine, and so if it notices you usually go for a long run on a Tuesday morning then it will give you a full charge the night before.

This is a much needed new feature as the tiny batteries in Apple Watches are more prone to the effects of aging than larger devices. Their small capacity means a slight decrease in capacity will have a notable effect, and also mean users are likely complete a greater number of charge cycles over a shorter time than on say an iPhone or MacBook.

That said, the feature is it is perhaps not visible enough. Various technical support forms and subreddits have been flooded with people who think their watch is malfunctioning. As is often the case with Apple, you are probably best off simply not looking at the battery meter and just using the watch. If you do notice the battery is not fully charged but think you might need it to be, the support document details how to temporarily disable the feature (note, you need follow the instructions while the watch is connected to power).

Update 19/10/2023: I noticed additional messages that appear when the Apple Watch is first place on its charger and when the battery icon is tapped within control centre shortly after removing it from the charger. I have updated the header image to include these (top left and top right respectively).