system
A chat on subreddit /r/NoStupidQuestions
human
I actually saw something about this. It's usually a little bit cooler in the house in the middle of the night, which affects the battery. So it's not just a coincidence.
gpt
I just googled the same question and kidde had a blurb about a battery's internal resistance increasing as its life begins to end. A temperature drop increases the resistance further, and most homes are coolest between 2a and 6a, especially so in winter. Apparently 3a is the sweet spot in my home.