Long-life smoke alarms versus lithium batteries

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#1261754 18-Mar-2015 15:02

Lithium batteries are probably a complete waste in most smoke detectors. With the notable exception of the ones that come with built in 10-year batteries.

The 9-volt "10 year" batteries typically last for about 5 years (know this for a fact from selling smoke detectors and these batteries for more than a decade).

If you want something that lasts more than a year: Use a good Alkaline battery. If you choose a cheap non-alkaline battery then change every 6 months.

The cheaper "heavy duty" (Typically zinc-carbon these days) batteries do have a longer discharge period than Alkalines so could be better for warning you about low battery if you don't usually pay attention to your smoke alarms.

One thing that I think is more important than the batteries is to choose the correct type of smoke alarms. Too many of the smoke alarms sold are ionization smoke detectors. These smoke detectors are more likely to give you false alarms, and they are also completely useless for smoldering fires. The type you want is the optical/photo electric smoke alarms. They will give you the best warning for all types of fires.

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jonathan18

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#1261764 18-Mar-2015 15:13

jarledb: Lithium batteries are probably a complete waste in most smoke detectors. With the notable exception of the ones that come with built in 10-year batteries.

The 9-volt "10 year" batteries typically last for about 5 years (know this for a fact from selling smoke detectors and these batteries for more than a decade).

If you want something that lasts more than a year: Use a good Alkaline battery. If you choose a cheap non-alkaline battery then change every 6 months.

The cheaper "heavy duty" (Typically zinc-carbon these days) batteries do have a longer discharge period than Alkalines so could be better for warning you about low battery if you don't usually pay attention to your smoke alarms.

One thing that I think is more important than the batteries is to choose the correct type of smoke alarms. Too many of the smoke alarms sold are ionization smoke detectors. These smoke detectors are more likely to give you false alarms, and they are also completely useless for smoldering fires. The type you want is the optical/photo electric smoke alarms. They will give you the best warning for all types of fires.

Thanks for the detailed reply, and good to hear from someone with direct experience in the area. However, I'm not sure how you conclude a lithium battery is a 'complete waste of time' given a battery purchase price of $14 with an assumed life expectancy of 5 years equates to an annual running cost of $2.80.

Would any alternative (a good alkaline, as you recommend) last even five years and/or have a lower annual running cost?

Agree re choice of type of alarm - all ours are photoelectric, and we have seven througout the house, including a seperate home theatre. Though is there no benefit to having a mix of this and the ionisation-type? I vaguely recall reading a suggestion that this was the case.)

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#1261776 18-Mar-2015 15:27

"9V" Lithium rechargeables have about the same mAh capacity as alkaline but the nominal voltage is lower. Depending on how long the volts hold up you may have to be recharging or swapping regularly. Lithium Iron non rechargeable have higher capacity and nominal volts than other types.

jarledb

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#1261777 18-Mar-2015 15:27

jonathan18:
Thanks for the detailed reply, and good to hear from someone with direct experience in the area. However, I'm not sure how you conclude a lithium battery is a 'complete waste of time' given a battery purchase price of $14 with an assumed life expectancy of 5 years equates to an annual running cost of $2.80.

Well, thats a good point. Its a cost/benefit calculation. But make sure you buy good quality batteries and take the cost of them into consideration vs using Alkaline or something cheaper. One benefit of changing batteries more often is that you get a reason to check your smoke detectors more often.

Would any alternative (a good alkaline, as you recommend) last even five years and/or have a lower annual running cost?

A good Alkaline will typically last a couple of years. If we compare the Duracall Alkaline (which I have had good experience with) for $8.99 vs Energizer Lithium for $21.78 the yearly costs are $4.50 (alkaline) vs $4.36 (lithium) per year. So not a big difference.

Agree re choice of type of alarm - all ours are photoelectric, and we have seven througout the house, including a seperate home theatre. Though is there no benefit to having a mix of this and the ionisation-type? I vaguely recall reading a suggestion that this was the case.)

The only place you will have extra benefit from an ionisation smoke alarm will typically be in your living room if you have things there that are highly flammable. And you usually do, sofas, curtains, tablecloths etc. are usually highly flammable.

BUT, I would not have just an ionisation alarm in my living room. To me the difference between an ionisation alarm and a photoelectric alarm in detecting an open fire (Which is what an ionisation alarm can detect) is so small between ionisation and photoelectric that I will always go for the photoelectric - also in the living room.

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#1261789 18-Mar-2015 15:50

I think the decision to use photoelectric alarms everywhere is based on some salient facts about house fires:

smoke inhalation is the majority cause of death
the majority of deaths occur at night or while sleeping
the failure rater for ionization alarms is too high, around 25% in some studies.

We use a combination alarm in the kitchen/dining/living area and photoelectric everywhere else. I've started buying 10 year alarms for two reasons: to remove the hassle having to change batteries and the quality of the alarms is better. Further benefits that I've observed are that the combined alarm is far more effective at warning us about fats approaching their smoke point and the failure rate so far is much lower. They're also much better around electronic devices which typically overheat well before flames are ever produced.

Stu

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#1261850 18-Mar-2015 17:15

jarledb: The 9-volt "10 year" batteries typically last for about 5 years (know this for a fact from selling smoke detectors and these batteries for more than a decade).

I bought six smoke alarms with '10 year' batteries in 2010. One almost made it to 5 years, and the rest between 2 and 4. They're obviously not all created equal!

People often mistake me for an adult because of my age.

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#1261856 18-Mar-2015 17:29

"Heavy duty" or "Super heavy duty" batteries have about 1/3 the capacity of alkaline, and they work by corroding an electrode away and eventually can corrode through the case (or a bad seal) causing acid leak. Alkaline on the other hand does not leak as easily and has a much longer shelf life. I would not buy batteries off eBay unless it is from a reputable company. LiPo rechargeable batteries have a nominal terminal voltage of 7.4V, and can cause a fire when they fail. LiFePO4 rechargeable batteries have a lower capacity than LiPo, but the terminal voltage is 9.6V dropping to 9V towards the end and then 6-7V when discharged. LiFePO4 is the safest Li battery out there, but unfortunately categorised with LiPo.

The fire service recommends 6 months because they are cautious, and knows customers don't know the difference between batteries even though many smoke mention you should use alkaline batteries.

I buy 9V alkaline batteries from my employer for much less than you can imagine, so I'll stick with Alkaline. But in general they are a good choice anyway. Have a look at Bunnings Varta multi packs.

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#1261857 18-Mar-2015 17:29

I think it is a no brainer to buy a 10 yr alarm with an inbuilt battery. No having to worry about changing the battery, no additional expenses in purchaing a battery, and installing it, which takes time. Also by the time the battery in the 10 year alarm runs out, you will need to change the alarm to a new one, as they wear out. I think firefighters recommend replacing batteries very 6 months, because many people buy cheap ones which don't last much longer than 6 months. But good ones may last 2 years. But you know when they are low, as they beep. So firefighters need to cover themselves for the lowest capacity/crappy batteries.

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#1261902 18-Mar-2015 19:05

mattwnz: I think it is a no brainer to buy a 10 yr alarm with an inbuilt battery. No having to worry about changing the battery, no additional expenses in purchaing a battery, and installing it, which takes time. Also by the time the battery in the 10 year alarm runs out, you will need to change the alarm to a new one, as they wear out.

Yep, but my original question started with my preference to be able to reuse my existing alarms, hence asking about using lithium batteries in them. Throwing out these alarms would just be a waste!

I think I'll give those Varta ones from Bunnings a go...

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#1261913 18-Mar-2015 19:28

jonathan18:
mattwnz: I think it is a no brainer to buy a 10 yr alarm with an inbuilt battery. No having to worry about changing the battery, no additional expenses in purchaing a battery, and installing it, which takes time. Also by the time the battery in the 10 year alarm runs out, you will need to change the alarm to a new one, as they wear out.

Yep, but my original question started with my preference to be able to reuse my existing alarms, hence asking about using lithium batteries in them. Throwing out these alarms would just be a waste!

I think I'll give those Varta ones from Bunnings a go...

Depends on how old the alarms are though. Often it can be difficult to tell, and their effectiveness may go down over time. At some stage they will end up in the land fill anyway, and we live in a disposable society, as they are not recycled. But my point was that you may not be saving anything by keeping them.

richms

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#1261914 18-Mar-2015 19:31

Seems quite easy to tell. They start off white and end up yellow. When they are too ugly, replace them.

Richard rich.ms

MadEngineer

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#1261941 18-Mar-2015 20:28

http://www.cavius.co.nz/products/

You're not on Atlantis anymore, Duncan Idaho.

Bung

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#1261975 18-Mar-2015 21:13

AFAIK the first of the Cavius were 5 yr batt. I've seen 5 and 10yr versions in different shops.

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#1262014 18-Mar-2015 22:34

regarding ionising vs photoelectric, here's a good video on the subject: https://www.youtube.com/watch?v=zrOLxh8GuCU (ignore , if you can, the dramatization)

TLDR version: don't only have ionising.

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#1262090 19-Mar-2015 07:20

Since no one has even mentioned it yet, I will.

If you have an alarm system (many people do have a security system) why not simply get smoke detectors added onto your alarm?

This means no battery changes, ever! (unless you count your alarm system)

As long as you have your alarm serviced regularly, you don't need to worry about batteries.

And for the miss informed out there, by regulation all smoke detectors connected to security systems MUST activate the siren/s if tripped regardless of the arm status of the alarm.
This means if the smoke detector detects smoke it will set off the siren, even if not armed.

It should be simple for any alarm installer to do this, and if they say they can't, then you should get another company to look after your alarm.

My two cents.

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