Uncle Monster wrote:
On Monday, December 14, 2015 at 7:14:18 PM UTC-6, Oren wrote:
On Mon, 14 Dec 2015 13:25:24 -0800 (PST), DerbyDad03
wrote:

On Monday, December 14, 2015 at 8:10:58 AM UTC-5, Stormin Mormon wrote:
On 12/13/2015 10:55 AM, notbob wrote:
Yes. I've seen AC powered (plug into wall socket) smoke detectors.
The horn will blow you right outta yer bed. Sears usta sell 'em. Not
a battery to be found.

nb

I wonder if that's a good idea, to have AC power
smoke detectors. We do power cuts now and again.

OTOH, less often than forgetting to test the unit
every month, and change battery twice a year.

Can't hardly win.

That's why they sell AC units with battery back-up.

That's why they sell units a 10 year lithium battery. Sure, they should
still be tested, but you don't have to change the battery. Who changes
the battery twice a year, anyway?

Most modern detectors will warn you when the battery is dying - but
not yet dead. Most modern detectors make it very hard to remount the
unit if you take the batteries out.

For what the units provide, I think they have made them pretty easy to
maintain.

A few years ago I replaced all my detectors. Bought the unit where
there is no need to remove it from the ceiling for a battery change.
They have an access (door) to replace the battery. Some are
inter-connected to AC power and some are not.

Why do batteries die at 2:00 AM and start chirping ?

At the house, I had a battery go bad in a UPS at 3:00am. The low battery alarm is louder for the UPS than it is for a smoke detector. à°*_à°*

[8~{} Uncle Beeping Monster

Murphy's law at work, LOL!