Your google Pixel phone has a smart charging feature built into it that hopes to extend the lifespan of your battery. It's called “Adaptive Charging” and when enabled, it will charge your phone slower at times to try and hit the 100% mark closer to when you might unplug.
Up until the past week or so, your Pixel phone would trigger Adaptive Charging when you set an alarm for the following day between 3AM and 10AM. So when you plugged your phone in at night (between 9PM and 4AM) to charge, it would then charge “steadily overnight.” The idea here is to optimize how your battery charges, because lithium-ion batteries can decline in performance based on temperature, usage patterns, and age.
At the end of last week, 9to5Google noticed that Adaptive Charging had been triggered on a Pixel 7 without an alarm being set. The notification for Adaptive Charging mentioned that the phone would make sure the battery was full (100%) by 7AM, again, without an alarm.
That's a noteworthy event as it could mean that Google has adjusted how Adaptive Charging works. And they may have, as the description for the setting has apparently changed from mentioning an alarm being necessary to what you are seeing below, which simply references it being “Activated based on your usage cycle.”
In other words, your phone is now learning your usage patterns and then adjusting charging around those to help keep your battery healthy. If it recognizes that you are charging each night at 11PM and pulling it off the charger at 7AM, it could utilize Adaptive Charging without an alarm set.
Google has not yet confirmed the change or made an announcement to my knowledge, and their support docs for the feature still mention the alarm. But since we are also seeing the change on a Pixel 7 Pro running android 13 QPR3 Beta 1, this could be something that's rolling out.
For those not familiar with this idea, I'll refer you back to 2020 when oneplus introduced just this. They called it Optimized Charging” and explained that it would learn your charging patterns and try to optimize overnight charging without an alarm. Good to see others adopting the idea.