On 15/01/2021 17:15, Bert Coules wrote:
I have a mains smoke alarm with a 9v battery backup.Â* It started to
beep: regular beeps at roughly ten second intervals for something like a
minute, then a long silence before it started again.

According to the manual this is the battery-low warning, so I took off
the cover, removed the battery - and then discovered that I didn't have
a replacement.

I replaced the body of the unit without the battery - and it's still
beeping.Â* Not regularly this time but seemingly at random:Â* beep... beep
beep beep... beep beep.Â* Again this is for about a minute at a time.
There's nothing in the manual about this and it seems too irregular for
a built-in "no battery present" warning (and if there was one, I imagine
the instructions would mention it).

I don't want to turn the alarm off overnight but I think I might have to.

Has anyone else encountered this or something similar?

Thanks.



The unit checks the voltage of the battery and bleeps when the voltage
is low.

Replacing the unit to mains power without a battery will show as low
voltage and as there is no reference at all to 9V has probably confused
the PCB.

You need a battery.

--
Adam