Hard Wired Smoke Alarm Battery Question

Old 03-10-07, 02:34 PM
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Hard Wired Smoke Alarm Battery Question

Hi Electrical Forum!

This question is born out our curiosity as much as economics. If a smoke alarm is hard wired, how often should one change the batteries? Should they be changed every 6 months (when the clocks are changed for daylight savings time as the fire department and other safety conscious people suggest)? Or if the smoke alarm is primarily powered by the house wiring, does the battery not get used very much and the batteries will last a lot longer?

To error on the safe side I have been replacing the batteries every six months, but each time I am wondering: is this necessary, am I pitching perfectly good batteries?

Also, as long as I am asking, do the smoke alarms draw power all the time when they are lighting the little light and are “smelling” for smoke or only when they are sounding an alarm?

Thanks for any and all insight and help with this,
Andy Frank
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Old 03-10-07, 02:40 PM
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I do not replace smoke alarm batteries more often than once per year. That is overkill. Yes, it helps ensure a fresh battery, but it also wastes perfectly good batteries.

I think the reason people recommend twice per year or even once per year is because some people won't bother, but by telling people those times, they might get them replaced at least every other year.

Yes, replace hardwired smoke alarm batteries on the same schedule.

A smoke alarm draws power all the time.
Old 03-10-07, 02:43 PM
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The official recommendation is still to change them annually. Some say semiannually. But I think that that is ridiculous. I don't change mine until they start chirping. I can get several years or more out of a battery. I don't see any advantage to changing them sooner (except for the fact that I usually have to change them in the middle of the night).
Old 03-10-07, 03:16 PM
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The time was originaly suggested when all smokes or some were battery only.
New York.. The other day.. With out them they don't work.

If Ac powerd with bat. back up.. Go with the chirp. Unless you lose power every week. Vacuume them out once a year, and test them once a month.

Smoke tests, not just a button. Be carefull, light a paper towel and put it out, Let the smoke do it. CO- Can exhaust from your car, then release it at detector.

You can't be too safe.
Old 03-10-07, 03:18 PM
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the reason I see to change them as a preventative action (annually) is if the power is off for whatever reason (power outage; fire in the electrical panel) although the chirping has not begun, there is no guarantee there is enough power in a battery to sound the alarm.

Pretty cheap insurance to me.
Old 03-11-07, 02:22 PM
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Thanks to all for the information and help.
Old 03-12-07, 06:47 AM
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Since they are only drawing from the battery when the power is out, there's no reason to pitch the battery every 6 months or even a year. Check the date on the battery itself, that's the estimated 'shelf life', and without a current draw, the battery is essentially in storage.

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