
Why is it that when a smoke detector battery gets low enough to trigger that "beep" sound..........it's always in the middle of the night.

I've got six of 'em in my house, and damned if they don't always run low on back-up battery power between midnight and five in the morning.
I pulled batteries out of two adjacent to each other (one in bedroom and other just outside in the hall), then also unplugged the damn things and beep was still going.

Went to other end of house and listened to those....still heard the beep, and it was not coming from them either..........checked the bonus room, not that one (good thing, cause need a ladder to reach it).
Finally realized I (also) was the proud owner of a carbon monoxide detector that I bought years ago and plugged in under the front hall table. It seems it has a similar (low battery "beep") that was the culprit. But I spent 20 minutes or so before I found it.