How often should I change the 9V backup battery in my Hard-Wired smoke detector? We have several. The manual says “when it starts chirping” but that’s not very pro-active. At least one online video says every six months. That (or yearly) sounds practical for a battery-operated unit. However for a hard-wired unit (i.e. AC-powered), that is normally not using the backup battery, I would expect it to last longer. Let me emphasize these units do not have the 10-year backup batteries - just the common 9V batteries.
I replace mine every year. If I forget, the chirping battery alert never starts at 5:15 pm. It always starts at 2:45 am.
You could probably change them half as often as your non-hardwired smoke detectors but who wants to keep track?
My suggestion is to swap in some ten year 9V batteries and change them every 9 years or when they start chirping.
We started installing the ten year batteries anytime we installed smoke detectors due to excessive call backs to replace the standard batteries. They were failing before the one year warranty expired.
We change ours every year.
I found my chirping was not related to any battery - there is none - but to a failure of the detector. Apparently some are only good for a decade or so. You may get a false sense of security if it is too old?
Yes, many have a 10 year programmed lifetime after which they will beep until replaced.
The 9V batteries that I get have a “good through date” on them. I have a home information spreadsheet with a tab for batteries. I put the battery date and the location of the detector in the spreadsheet so I know about when to replace them. The batteries can last around 5 years, and the method has been working well for me.
It is suggested, at least we suggest at our firehall, that batteries be replaced every time you change your clock. Sure, 9v can last MUCH longer than that, but better safe than sorry.
You might want to check the life of the smoke detectors as well. Most of them are good for ten years according the the National Fire Protection Association (NFPA). You get a ten year battery in a ten year device and forget about it for a decade.
First, thanks to every one. Next, as a note, you can easily tell if the detector has a 10 year battery or not because if it does then it won’t have a door or slot to change the battery.
As I thought I read the explanation, smoke detectors include a small radioactive granule that the detector across the air gap is detecting. If smoke particles block the air gap.it signals “fire!”. When that radioactive piece loses enough radioactivity the detector no longer sees it and starts beeping. So your detector may or may not last 10 years, but that’s the approximate lifetime…
(Fun fact - google the story of the “radioactive boy scout” who collected among other things, radioactive particles from multiple smoke detectors.)
I’ve heard that, but it strikes me that americium-241 in smoke detectors has a half life of 432.2 years, so that in ten years the radioactivity will decline by just about 1.5%. It seems to me that some other components lifespan may be responsible for the detector wearing out.
As an alternative, You might consider replacing the wired one with a ten year sealed one. Most fire officials are recommending this now and in some places it’s code. Safer and no need to change batteries for a decade. And 10 years of batteries might be a wash money-wise.
ETA: For example: 3 for $49
There are ionizing smoke detectors that use radioactive Am to create a conductive path between two electrodes and gauges how the smoke (which absorbs these ion) affects the electrical current. There are also photodetectors, which gauge how smoke affects the passage of light between a photoemitter and a photodetector. Some smoke detectors use both types of sensor.
Probably a sensible policy for battery-only detectors. It’s much less of a big deal for hard-wired smoke detectors, which derive their primary power from the grid; the battery for these detectors is merely a backup for when grid power fails.
These days it’s trivially easy/convenient to set electronic reminders far in the future using Google, Outlook, or whatever other calendar software you have at hand. I routinely set reminders for myself at work that are 1-3 years down the road for various long-term administrative tasks.
I had A/C w/ battery backup that were interconnected, meaning if one goes off they all go off; this would give you extra notification time if something happens in the basement while I’m upstairs in bed.
That’s a small plus but there has to be a good reason some municipalities are favoring sealed battery units. I’m guessing that reasoning might be that fires can cause electrical failure.
I’m not sure they’re particularly favoring sealed-battery detectors over grid-powered detectors. From this source:
Are 10-year sealed smoke alarms better than hard-wired smoke alarms?
There are advantages to both systems. Hard-wired smoke alarms tie into your home’s wiring and require professional installation, but generally do not require battery changes unless they feature a backup battery. 10-year sealed battery-only alarms are simple to install, and they work during a power failure. All smoke alarms have a lifespan of 10 years, sealed or non-sealed, and should be tested on a regular basis. When the battery wears out in a 10-year sealed alarm, the entire unit must be replaced, which helps prevent outdated units from staying in circulation. Battery back up hard-wired alarms/detectors are not affected by the new code.
The reasoning behind the new rule described at that link:
The purpose of this law is simple: if the batteries are sealed in for 10 years, homeowners can’t borrow them for the remote, or forget to change them on an annual basis. That means less non-functional smoke detectors and more early warnings when a fire breaks out.