"Oren" wrote in message
wrote:

And. Why do they only go off at 3 AM.....

That's when it's coldest part of the day and dying alkaline batteries are
susceptible to the cold.

It don't get very cool here, inside.

There HAS to be another reason the thing alarms at 3 AM.

I have not found the answer.

Slight temperature drop really IS the answer. It's like the old joke, I
don't have to outrun the bear, I just have to outrun you. I'm an obsessive
about recording temperatures and home automation so I've seen this happen.
It cools down enough at night in the fall to drop the battery voltage just
enough to trigger the beep alarm.

You'll see "early morning beeping" more in the fall than the spring because
the overall outdoor temps drop in the fall and houses cool down. It doesn't
require a profound temperature drop. We're talking about 1 or 2 degrees
being enough to take a tired battery from being at just about threshold
"beep" voltage to just below it. If you've got an LCD thermometer with a
hi lo memory ($4 at the dollar store) and you mount it next to your smoke
alarm you'll see that when it beeps, the thermometer is registering the
coldest temperature of the last few weeks. You'll also be well on your way
to geekhood. (-:

We're coming up on the ideal test period. This is the month that a lot of
so-so batteries will lose enough power from the cool down to cause a
low-voltage alarm, especially on a night when the temperature drops 30 or 40
degrees.

Let's see what people report. Did I say I am also fire, smoke, CO2, Radon
and flood detection obsessed? It's the temperature drop. Really.

We certainly have enough theorists in this group to put this issue to rest.
(-:

--
Bobby G.