Do We Really Need To Change Safety Detector Batteries Twice A Year?

[SgtRock]

Greetings EEVBees:

--As you can see by the below links, here in the US at least, we are inundated with calls to change Smoke, Carbon Monoxide and other safety detector batteries every 6 months. Is this really necessary, so often. Or is it a plot by the battery makers?

http://www.ny1.com/content/top_stories/135420/change-smoke-detector-batteries-at-daylight-saving-time

http://www.coloradoan.com/article/20111104/UPDATES01/111104005/Daylight-Savings-Time-ends-Sunday-Change-your-batteries-when-you-change-your-clocks


"The language of experiment is more authoritative than any reasoning: facts can destroy our ratiocination—not vice versa. "
Alessandro  Volta 1745 1827


Best Regards
Clear Ether

[Balaur]

Well, safety detectors have been proven to be quite effective in case of accidents reducing loss of life and damage.

On the other hand, it seems that a rather high (~25%) percentage of them are not functional because of missing or empty batteries.

Since these devices are used by a large variety of people, more or less aware of the good maintenance practices, it's better to be on the safe side and use the most effective way to communicate on these issues. Thus, the battery replacement awareness programs.

From a technical perspective, the fire detector I have at hand looks to consume around 6 microamps constantly with occasional 150 microamps pulses each 10 seconds or so. Assuming an average of 55 microamps (a rather bold estimation), that makes a 550 mAh 9V battery to go flat in 10000 hours which is more than 1 year.

Cheers,
Dan

[saturation]

I agree with Balaur.  Any eevblog enthusiast would best check the actual power consumption of their safety devices to get a better estimate of the battery life beyond a blanket every 6 month change. 

My smoke and CO detectors do beep when the battery is low too as a backup for an annual change.

I also have water detectors, not really safety, but leaking water creates a lot of damage that can be avoided with a simple alarm.  The battery change cycle is 5 years, but I do it in 4.

 

[metalphreak]

In Western Australia its now a legal requirement to have hard wired smoke alarms fitted (or one with a 10yr battery life if hard wire installation is not possible).

http://www.fesa.wa.gov.au/safetyinformation/fire/fireinthehome/FireintheHomeManualsGuidelines/FESA-SmokeAlarms-NewSmokeAlarmRegulations2011.pdf

I think most of the Australian states have similar rules.


tl;dr I haven't changed a smoke alarm battery in years

[ivan747]

In Western Australia its now a legal requirement to have hard wired smoke alarms fitted (or one with a 10yr battery life if hard wire installation is not possible).

http://www.fesa.wa.gov.au/safetyinformation/fire/fireinthehome/FireintheHomeManualsGuidelines/FESA-SmokeAlarms-NewSmokeAlarmRegulations2011.pdf

I think most of the Australian states have similar rules.


tl;dr I haven't changed a smoke alarm battery in years

What if the electrical system fails? It could be an electrical fire and it could take the entire house's power out. Or perhaps the power goes out due to a storm and something tripped a candle down to a carpet, how can you detect that?
My guess is that there is a lithium coin cell installed as a backup, the kind of coin cell that lasts 15 years inside a computer motherboard. It should be rechargeable, too.

[Zero999]

What if the electrical system fails? It could be an electrical fire and it could take the entire house's power out. Or perhaps the power goes out due to a storm and something tripped a candle down to a carpet, how can you detect that?
My guess is that there is a lithium coin cell installed as a backup, the kind of coin cell that lasts 15 years inside a computer motherboard. It should be rechargeable, too.

If you read it in full, it suggests a rechargeable back-up battery.

[metalphreak]

What if the electrical system fails? It could be an electrical fire and it could take the entire house's power out. Or perhaps the power goes out due to a storm and something tripped a candle down to a carpet, how can you detect that?
My guess is that there is a lithium coin cell installed as a backup, the kind of coin cell that lasts 15 years inside a computer motherboard. It should be rechargeable, too.

Not sure how the normal hardwired ones work, but ours were fitted when we had a monitored alarm system installed. That whole system has a battery backup and automatically dials RAC Security to notify them of a fire (and they call the fire dept if they can't reach you).

[vk6zgo]

The requirement for mains operated smoke alarms in WA are only for when you sell your house,rent it out,or rent out part of it.(Bed & Breakfasts,etc.)

The rest of us can use battery units,& are urged to replace batteries once a year,the suggestion being that we do it on 1st of April each year.

VK6ZGO

[Conrad Hoffman]

I always mark the date on the batteries with a permanent marker. Some batteries are better than others, depending on how long they've been on the shelf and how well they were made. I change 'em once a year, or when they beep.

[metalphreak]

The requirement for mains operated smoke alarms in WA are only for when you sell your house,rent it out,or rent out part of it.(Bed & Breakfasts,etc.)

The rest of us can use battery units,& are urged to replace batteries once a year,the suggestion being that we do it on 1st of April each year.

VK6ZGO

I believe the idea is to slowly transition it into a requirement (for all established houses), but mandating that everyone installs them all at once will just create problems (think insulation scheme). If you consider how many houses are rentals, or change owners, they cover quite a large percentage.

One of ours was faulty and kept tripping randomly until we replaced it, and the alarm siren sure does wake you up in a hurry at night!

[A-sic Enginerd]

I change mine when they start beeping, which turns out to be about once a year.
On the other hand look at it this way.
As mentioned, better safe than sorry. So if a batt on average lasts about a year in these, then you're pretty much guaranteed to have a working unit if you replace the batt on a slightly shorter interval. So thinking as a "marketing" or PSA type (Public Service Announcement), it's easiest to align it with something that EVERYONE will be doing at a regular interval. Sooooo, they line it up with the daylight savings time changes. Yeah, dunno how the handful of states that DON'T do a time change manage it, but anyway....

It's the one thing that regardless of race, religion, creed, sex, political affiliation, etc. that EVERYONE in a state will stop and recognize, so now they're sure to have everyone at least listen to it.

[EEVblog]

Here the fire departments are trying to encourage people to change them when they put their clocks back and forth for daylight saving.
Makes sense, and is the best way to ensure that people do actually change them.
When something can save your life, you don't quibble over maximising the battery capacity.

Dave.