Mains powered smoke detector fault

[Pallion]

I have 3 deta 3225918 mains powered smoke detectors fitted. All 3 are giving a high pitched beep (not at the same time) about every 30 to 60 secs.
Batteries are recent and mains led is lit. Does anyone know the reason for the Beep before I go looking for a hammer!

 

[breezer]

still change the batteries

 

[Pallion]

still change the batteries

Ok I'll give it a go. thanks.

 

[sparkydude]

Make sure the batteries are alkaline batteries as some normal 9V batteries do not provide enough current to run them correctly.

Nick

 

[Steve]

Zinc carbide batteries are carp - use alkaline.