10 year smoke detector battery

[Phlack]

Or are they 7 year?

Anyway, from various places (like realgoods and ratshack) one can obtain long lasting 9v smoke detector batteries.

I have already bought some. I replaced two already (but I think they were still good, and that it was just dust in the detector). What are everyone's opinions about these? Do they actually last close to what they claim?

And why wouldn't these batteries be good for other uses as well?

(I really know nothing about them other than what the packaging says)

Thanks
-Mike

 

[Darell]

I assume that they're lithium 9Vs? Yes, they'll certainly last longer than the Alks, how much longer, I don't know. For hard to reach places, they're the ticket for sure.

 

[sunspot]

What's the price on those bad boys? That'll tell you in a heartbeat if they are alks or lits.

 

[James S]

The price is high /ubbthreads/images/graemlins/smile.gif

I've seen the lithium ones sold as expensive smoke dectector batts, and they do last a long time. I left a 2 year old one in the smoke detector in the last house and it was still testing fine at the end of that time.

I think that they get their best output life at very low power levels though. If you run a 5watt LS from them they won't give you nearly the output as if you ran a 5mm from them. Some testing is probably in order, who wants to donate the cash to test some? /ubbthreads/images/graemlins/smile.gif

edited to fix silly typo

 

[GJW]

A typical residential smoke detector only draws about 300-500 micro-amps.

 

[mattheww50]

It is a whole lot LESS than 300-500 microamps. At 500 microamps, it would take 12 Mah per day, and if you were lucky, you might get 6 weeks life out of a 9V battery. The fact that it lasts a year or two puts the maximum draw more in the 30 microamp range. Using CMOS circuitry and an ionization detector, that is not very hard to do.

 

[GJW]

You are correct.
I was looking at a 24VDC spec sheet.
/ubbthreads/images/graemlins/ohgeez.gif

 

[Phlack]

I'd like to say they are about $13 each.

So I guess if they have a big draw on them, that isn't good, which is why they are good for smoke detectors?

 

[PsycoBob[Q2]]

There are several (ok, a few more than 'several') kinds of Lithium cells. I think a few are optimized for very low-current applications, like remembering settings in a computer with its power off.

Does the battery look like the one over
Here?

 

[Tweek]

I really like these for low draw applications, they seem to last forever. I put one in my Fluke 87 probably two years ago now, and haven't replaced it since. And I use that meter a lot, at least every other day! And putting them in smoke / CO detectors is definately worth the price, when you don't have to worry about changing them out. Especially those impossibly located units that are on the ceiling above the bottom end of the basement stairs... /ubbthreads/images/graemlins/smile.gif


Chris

 

[SilverFox]

I would just like to add a word of caution.

Just because you install a long lasting battery in your smoke detector does not mean that you can forget about it.

Remember to test it periodically. It could save your life.

We test ours every time my wife cooks chicken. She found this method where you heat the oven to 500 F and cook for 10 minutes per pound. The high heat sears the outside and the results are a very juicy and very tasty chicken. The down side is that the grease splatters inside the oven and at 500 F tends to smoke up the kitchen. Sometimes we are a little late in turning on the kitchen fan and off goes the smoke alarm. I end up with a very nice meal and a good nights sleep knowing my smoke alarms are working.

Tom

 

[Mednanu]

[ QUOTE ]
SilverFox said - I end up with a very nice meal and a good nights sleep knowing my smoke alarms are working.

[/ QUOTE ]
Sounds like a good name for that meal would be "5-Alarm Chircken" !

 

[Phlack]

[ QUOTE ]
PsycoBob[Q2] said:
Does the battery look like the one over
Here?

[/ QUOTE ]

I believe that is the one, yes. Can't say for sure, as I'd have to get out my 12' ladder, but that looks pretty close to it.

 

[Saaby]

Where's ChrisM when you need him...he installs fire alarm systems for a living you know...

 

[Steelwolf]

I've got one of those. They sell them in the local **** Smith's Electronics store for about AU$18 IIRC. The claim is that because it is a lithium based battery, the shelf life is about 10 years or so. And since the current draw on them is so low when used in a smoke detector, run time is thus determine by shelf life. At 30 uA draw, the self-discharge would actually be higher than the power required.

I just had an idea. NiCad + Solar panel (small) + diode. If it is set up right, you would never have to change the battery. Whaddaya think? /ubbthreads/images/graemlins/grin.gif

 

[Phlack]

Would have to be a long cord to the solar panel, assuming you mount it on the roof. Or are you thinking it could work off the ambient light?

(I'll assume you're not trying to charge the lithium batter with the panel)

[aside]
These detectors that I'm putting them in are also powered by the house current (and I assume work off battery only when power goes out). I wonder why there is any drain at all.

-Mike

 

[Steelwolf]

Phlack: Yep, thinking about working off ambient light and of course not charging lithium with it. I thought about it because I realised that I have several emergency solar-charged items lying around the house at strategic spots so that they get enough sunlight to maintain their charge. ie, I'm merely battling against the self-discharge rate of the cells. Since smoke detectors use so little power, I'm sure the amount of light required would not be very much more than that required by my emergency gear.

 

[Hemingray]

A home smoke detector (ion type, the most common) draws around 10 micro amps, a photo-electric unit draws around 30 uA. The photo electric units typically use an IR LED pulsed on every 4 to 5 seconds, for about 50-100 us, at up to 1A instantaneous current, a photo diode picks up any light inside the detector chamber that may be scattered by smoke (or dust). These are more efficient for larger smoke particles (like burning foam rubber), and the ion detectors are more efficient for small particles, such as paper or wood smoke, when the broiled steak is about ready, or when the steam from a hot shower escapes the bathroom. The last two are not the intended purpose, they just work very well with most cheap ion detectors, as I have experienced for years and years.

I used to work as an engineer at Simplex, they made commercial grade fire detection systems, I learned a lot about how these things work. They did not make "home" cheap detectors. Just look around the work place, school, hospital, etc, you are very likely to see Simplex (now Tyco/Grinnell) sensors, annunciators, alarm stations, and master clocks around you.

/ed B in NH