Joe J wrote:
Bought a house 6 months ago with all electric powered smoke detectors
that have a battery back-up. Sure enough, 3 AM, one starts chirping
every 30 seconds. Really ****ed off the dog!

Seven detectors, so I changed the batteries in all of them, because
the dog said she didn't want another 3 AM wakeup call.

No manual, just wondering how long they last when they are AC wired? I
know battery only, they recommend once or twice a year, but what
about AC powered? I would think several years, no?

Thanks,

Dunno. The rule of thumb is to replace them twice a year (when the Daylight
Savings Time switches). Inasmuch as modern smoke detectors usually fuss at
you when they begin to deteriorate, I suspect the replacement interval can
be extended past the standard six months.

Someday there will be a mains-powered smoke detector with a battery that
gets charged during normal operation, much like the button battery in a
computer.


Save the batteries you remove in a specially-marked container. Use these
used batteries in non-critical applications (radio, toys*, etc.). Batteries
in smoke detectors draw a miniscule amount of current and smoke detector
batteries typically approach their shelf-life even when installed
(shelf-life is measured in years).

I put a sticker on my alarm batteries with the date of installation.

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*You can make a friend: Got a grandkid or a neighbor's child that could use
them?