Hell hath no fury...

...like Sarah being kept awake in the night by a chirping smoke alarm. There are people who will vouch for this. There are other people who have tried to distract me from a chirping smoke alarm by making other noises in the night. The less said about that night the better.

Luckily for Bryan, the smoke alarm starting chirping last night just before bedtime, and when I told him that the battery would have to be changed before bed, he agreed. He knows what's in his best interests and what's not. We didn't have a spare battery so we just took out the original and although it still chirped for a while, Bryan was more than happy to wrap the offending smoke alarm in a towel and hide it under pillows in the spare room with the door closed. I might point out that we did have another fully-functioning smoke alarm in the house when we chose to remove the battery from the malfunctioning one. I might also point out (because I have been questioned in the past about the stupidity of removing batteries from smoke alarms), that if the alarm is chirping it means it ain't going to work even if there is a fire because the battery is dead.

The question I have is why do smoke alarm batteries always fail in the middle of the night in winter? Why?

Oh here's why:
Batteries produce electricity by means of a chemical reaction. Like almost all chemical reactions it proceeds more slowly in the cold. That’s why even ¾ charged batteries can cease to function in the snow, as many tourists have found out to their dismay.
At night it’s colder than during the day and the charge in the battery falls correspondingly triggering the low battery alarm. It’s very obvious on days when daytime temps are mild and the nights are cold and almost invariably the alarm stops the following morning as the temperature climbs again.