Why do smoke alarm batteries always die and start chirping in the middle of the night? Mine started at 3:04 (or at least that’s when it woke me up). the middle of the night on a weekend is really not the time when I can do much about it other than unwire it (it’s a combined wired/battery backup Carbon Monoxide / smoke alarm) and pull it down and remove the battery. My landlord replaced the batteries a little under 4 months ago in the 2 detectors that needed them (the others have a nifty 10 year sealed lithium battery) so I’m not sure why this one was chirping every 30-40 seconds and saying what I believe was “Low Battery / French equivalent” in a muffled electronic voice. Did I mention that this alarm was installed (by the landlord not by me!) in a spot where you have to put a small stepladder on a stair to get at it? yeah…great design there. So today I will go get new batteries and hopefully tonight I will actually get to sleep through the night.