Hardwired Smoke Detector w/ Battery Backup

Discussion in 'Off Topic [BG]' started by Bob Clayton, Jan 1, 2018.

  1. Bob Clayton

    Bob Clayton My P doesn’t have flats or tort Staff Member Supporting Member

    Aug 14, 2001
    Philly Suburbs
    So our current smoke detectors are going bad. They're hardwired w/o a battery backup. Replacing them with hardwired w/ battery backup.

    Theoretically speaking, if no power is lost, the batteries should last as long as the shelf life is, correct? Will the detector do any kind of self-check periodically to make sure the batteries are still good, and chirp if not?

    How long will the batteries last w/o power? The same as a 9v battery in a detector that was never hardwired?
  2. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, ChopShopAmps
    The common theme if you live where daylight saving time is observed is to change your batteries whenever you change your clock. For hardwired ones I'd imagine once a year instead of twice would be perfectly safe.

    What I wonder about is why 9v? The photo type (123?) Batteries in my rental property's wireless motion detector last for about 5 years... Seems that something as important as smoke detectors should be standardized to use a longer life battery than a regular ol' 9v.
  3. Bob Clayton

    Bob Clayton My P doesn’t have flats or tort Staff Member Supporting Member

    Aug 14, 2001
    Philly Suburbs
    Right, I get all that. But I mean if the detector remains hardwire and no power is lost, is replacing yearly really necessary? I believe the shelf life on a 9v is about 6 years?

    I'm asking more of theoretical type of situation rather than practical. I'll probably replace yearly.
  4. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    Ditto on chirping when the battery is low, but whether they ALL do this I do not know.
  5. With the Daylight Savings clock switch you choose one as a reminder to change, I change in the fall once a year, do not need twice. Though you should use the second clock change as a reminder to check that it is working, because most people forget all about them until they start chirping from a low battery, this is a guideline. You should check once a month as they do flash a little light once in a while so the battery is being used. Once a year change is good.

    Do not wait until they chirp, you are lazy @StereoPlayer. :smug:

    They do make some with a 10 year sealed battery. You should toss all testers after 10 years anyway so this is a convenient pack for high ceilings, or lazy people. :thumbsup: I mark the date I installed and battery changes on all of mine.

    From the U.S. Fire Administration:
    What powers a smoke alarm?
    Smoke alarms are powered by battery or by your home's electrical system. If the smoke alarm is powered by battery, it runs on either a disposable nine-volt battery or a non-replaceable 10-year lithium (“long-life”) battery. Alarms that get power from your home's electrical system, or “hardwired,” usually have a back-up battery that will need to be replaced once a year.

    I am with you Bob on your logic of them getting power from another source so should not need changed as often, but they want you to be safe than sorry.
  6. Lex P.

    Lex P. You've got it awful loud -Kathy P. Supporting Member

    Mar 19, 2003
    How timely of a thread! Just yesterday I replaced my 30 year old hard wired nonbattery smoke detector’s. I had no idea they needed to be replaced after 10 years. Fires with deaths in the area brought it to my attention. They have two AA batteries and are connected so if one goes off they both do. The literature recommends replacing the batteries every year. I feel like I dodged a bullet.
  7. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    01-January is a good day to do these things.

    I also put $1 in my savings account so it doesn't get closed down.
  8. -Asdfgh-


    Apr 13, 2010
    The ten year replacement issue is why I'd rather have battery-only detectors as it's much easier to replace them
  9. steve_ss

    steve_ss Shiny, let's be bad guys. Supporting Member

    Dec 6, 2016
    Southern NJ, USA
    Two years ago we lost power in our house for 5 days and all the batteries got replaced as soon as power was restored.

    As for changing the batteries yearly or whenever... I'm lazy and only change the battery when it starts to beep as the battery gets older. When I install a new battery, I write the install date on the battery with a sharpie marker. I have found that every time a battery gets old and beeps to be replaced, the beeping starts at about 2 o'clock in the morning. No matter how much you try to bury your head under a pillow, you can still hear the beep every two minutes. And removing the old battery doesn't help. The detector just thinks the battery has failed and needs to be replaced. I always have an extra battery in the house, just in case. And yes, the whole smoke detector needs to be replaced every 10 years. For my house, that ends up being 8 detectors. Not cheap, but worth the peace of mind.
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