Mains-powered smoke alarm give low battery warning for 1/2 hour at same time every morning

[Jimk]

My mains alarms have non-rechargeable 9v "pp3"s for backup....

[Jimk]

:-D:-D

[Jimk]

or attempt to proceed to make a "small snack" with tomorrow's lunch/tea food in a hot frying pan? ;-)

[Jimk]

Ah yes... the Politburo...

[NY]

Here's a weird one...

We got mains-powered smoke alarms around the house. I presume they have rechargeable batteries so they keep sounding if the mains goes off.

One of them has started chirping at 1-minute intervals at the same time every morning and does this for about half an hour before going silent. I presume that's a low-battery warning. The battery may well be losing its ability to hold its charge - I'll investigate.

But what intrigues me is why it always happens at the same time (from about

6:00 to 6:30) every morning.

[Clive Arthur]

That's when the house is coldest and the battery voltage lowest?

Maybe.

[Theo]

You sure they're rechargeable, rather than a sealed-for-life lithium primary cell with a 10 year life?

It's possible it has this 'gentle reminder' function every 24 hours, and it just happens to come at that time? I was reading the manual for a smoke alarm recently and it had an 8 hour postpone function for the low battery alert so you could stop it waking you up. Maybe yours has that too?

Theo

[R D S]

Same, reckoned to last about 7 years IIRC but will need replacing at some point.

[Brian Gaff (Sofa 2)]

If its rechargeable what sort of battery is it? Often if there is more than one it could just be oxidised connections. Brian

[ARW]

I am with the house is coldest and the voltage drops theory. It was in our wiki long before I did my Aico installers course who told us the same thing.

[Harry Bloomfield, Esq.]

NY formulated on Tuesday :

The coldest time of the day in a house, so probably when the battery voltage is lowest. Some mains alarms don't have rechargeable or replaceable batteries - when the battery fails, they are intended for the entire unit to be replaced.

[ARW]

Nah, that's 11.30pm when you try your luck after promising you would be home for 10:-)

[ARW]

And if you do not want an empty wine bottle smashing over your head best not be to be clever and say " Absence makes the heart grow fonder" as you stagger in.

[ARW]

The list of what you could do wrong is endless.

You are not allowed to see that list. Her Mother has had a bloody good look at it and added extra things whilst sat around the coven.

[tabbypurr]

Batteries produce electricity by chemical reaction. Chemical reactions double in speed for every 10C rise in temp. That's why smoke alarms always complain at the coldest time of the night.

NT

[alan_m]

Often they start chirping during the coldest part of the day - early morning before the sun comes out or your central heating cuts in.