9v smoke alarm battery question

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9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 8:01 pm

OK - it ain't the dreamliner, but I have put 3 new alkaline 9v batteries into a hard wired smoke alarm in my basement. The alarm starts chirping in about 10 days. Replace - same thing. The first battery last 5-6 months - but went when it got cold.

Where i live its cold but not arctic - the basement does not freeze hard but could get close. I haven't had any similar experiences with older smoke alarms that were not hard wired in the past. Is this a function of the battery chemistry and cold or maybe a sign of a bad part?
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Re: 9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 8:18 pm

Update - maybe it is like the Dreamliner. Reviews for both several brands of batteries and for several brands of hardwired smoke/CO alarms suggest this happens regularly!!! So maybe the alarms and the batteries have very poor QC. Anybody had up close and personal experiences in the middle of the night?
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Re: 9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 8:57 pm

Hmmm...

I live in Ottawa and the coldest it'll get in my house is 17C at night time (main floor). I don't heat the basement so I figure maybe around 12C? I've never had a problem. Then again, my basement never gets to "near freezing"
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Re: 9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 9:17 pm

Where I live is certainly not as cold and our alarms are not wired, so it's not surprising we haven't had this issue.

My best guess is that there could be a very fine layer of corrosion on the contacts. Try cleaning them with a nylon scouring pad (e.g. Scotch Brite) and return the same battery to see if that stops the chirping.
Also, if you can, test the charge on the 9V cells.
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Re: 9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 9:37 pm

SonicSilicon wrote:Where I live is certainly not as cold and our alarms are not wired, so it's not surprising we haven't had this issue.

My best guess is that there could be a very fine layer of corrosion on the contacts. Try cleaning them with a nylon scouring pad (e.g. Scotch Brite) and return the same battery to see if that stops the chirping.
Also, if you can, test the charge on the 9V cells.

Basic rule of thumb here is to change the batteries when you change the clocks for ST/DT and DT/ST.
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Re: 9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 10:51 pm

Try using a different battery chemistry. Can you get a Lithium based 9v if it takes 9v. You described as a "hard-wired smoke alarm" and yet you are inserting a battery ??? If it's hard-wired then you would have alarm cable running to it which also supplied 12v and could consume 50mA. A purely battery powered device is going to have a reduced power consumption and very low standby current draw.
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Re: 9v smoke alarm battery question

Postposted on Wed Mar 13, 2013 10:53 pm

Right. If its getting rather cold, a standard alkaline is going to lose its charge quickly. Try a lithium battery.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 1:28 am

Just a thought:
What happened to me was the battery was losing contact.
Went thru 3 batteries before I figured it out.
Try removing then re-inserting.
Terminal contacts were putting slight pressure on the batteries that over time forced them off.
I consider it a design flaw.
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Last edited by oldDummy on Thu Mar 14, 2013 1:59 pm, edited 1 time in total.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 6:34 am

How old is the smoke alarm and is it a pure smoke alarm or smoke/CO/flammable combination thing? I've seen some weird failures on smoke and CO alarms, they are meant to last for 10 years, but particularly the plugin CO/flammable type didn't seem to last longer than 2 years. Can you try swapping the alarm with one on another level and see if the battery draining issue moves with the alarm or stays on the basement level?

I've got the Kidde wired with battery backup talking smoke/CO type and don't have any problem with my basement, but like Sargent Duck I'm in Ottawa with a relatively warm basement. Watch out for rechargeable 9V batteries, they are actually around 7.2V and lots of stuff will not work on them. Try the plain lithium 9V and see if that does any better.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 7:53 am

What brand of battery are you using? Off-brand batteries are highly variable; some of them suck quite massively.

Stick with established brands like Energizer, Duracell, Rayovac, Panasonic... and make sure they say "alkaline" on them. Batteries that use old school zinc-carbon chemistry (including the ones marketed as "heavy duty") are not suitable for devices like smoke alarms. (It could be argued that they're not really suitable for *anything*, they're terrible value for the money; I'm not sure why battery makers even still sell them. Quite possibly just another example of artificial product segmentation, so that they can charge a premium for the alkalines.)
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 8:07 am

tygrus wrote:Try using a different battery chemistry. Can you get a Lithium based 9v if it takes 9v. You described as a "hard-wired smoke alarm" and yet you are inserting a battery ??? If it's hard-wired then you would have alarm cable running to it which also supplied 12v and could consume 50mA. A purely battery powered device is going to have a reduced power consumption and very low standby current draw.

Backup power for when the power goes out. You don't want to die because the alarm lost power do you?
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 9:03 am

I had a problem with these kind of units before and I think they try to charge the battery inside and require rechargeables.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 9:10 am

SuperSpy wrote:I had a problem with these kind of units before and I think they try to charge the battery inside and require rechargeables.
The ones I have don't try to charge the battery.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 9:50 am

So far I see at least two strong possibilities given:

1) Alkalines in a cold location = poor power retention
2) Cheap springy contacts (or moisture incursion) = poor contact performance

..and door #3 is that the alarm unit has somehow lost its AC source, and is running entirely off battery power. I had a friend accidentally buy units that were intended to be AC wired and install them as battery-operated units. They worked, but they blew away another battery every 3-6 months until he finally figured it out.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 10:37 am

notfred wrote:
SuperSpy wrote:I had a problem with these kind of units before and I think they try to charge the battery inside and require rechargeables.
The ones I have don't try to charge the battery.


Neither do mine.
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 12:59 pm

Thanks for the great ideas.

I will check for corrosion and that there is a good physical connection. There was no obvious issue but the battery has been a pain to install so there may be a fit issue. I'll also test the battery.

I already ordered a lithium battery (I use one on the freeze alarm in the house which is kept at 55F when we are not there - but its in the heated space and was never an issue in 4 years).

The alarm is a hard wired CO and smoke detector - Kidde. I assume the battery is backup for times when power might go out but otherwise should not have a big draw on it. It is 6 months old and this is dead battery number 3 - the last going after two week. I use new Duracells but all were alkaline (and claim to be good thru 2019 or so). The other two same-model KIdde's in the heated area don't have this problem.

The basement space is probably 35-45F. It has never frozen but its cool.

Now we should come up with a better Dreamliner response!
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Re: 9v smoke alarm battery question

Postposted on Thu Mar 14, 2013 2:23 pm

notfred wrote:
SuperSpy wrote:I had a problem with these kind of units before and I think they try to charge the battery inside and require rechargeables.
The ones I have don't try to charge the battery.


Perhaps my memory is failing me but I remember swapping the annoying ones with NiCd 9v and they stopped chirping. But it's been years and I don't remember the brand or much of any details.
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Re: 9v smoke alarm battery question

Postposted on Mon Mar 18, 2013 9:31 am

So - after 24 hours the lithium battery is still working. The maybe 10 day old duracell alkaline was totally dead upon ammeter check! It was brand new and good to 2017!

The battery port pivots out - so the connection is not really easy to alter - but the contacts all were fine and clean.

Maybe its a bad part.
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Re: 9v smoke alarm battery question

Postposted on Fri Mar 22, 2013 2:02 pm

Sorry for the late post, but just wanted to mention that any corrosion on the terminals would lead to decreased current levels, not increased current levels. The batteries would be sourcing less current and would, in theory, last longer.

Second, you mentioned that these smoke detectors were "hard-wired", which I assume means that they normally run off the mains and only require the battery when the mains voltage is down? Is that the case? If so, why are the batteries being depleted at all? If the batteries are being depleted that quickly, maybe you have a problem with the mains supply. EDIT: Me no read entire thread. Me dum.

Also, mains-connected devices that have a battery fall-back built in will sometimes provide a "float" voltage to the battery to keep it topped off. Non-rechargeable batteries in general and alkaline batteries in particular do not like this. They will be angry with you. Do not do this. Check to make sure the smoke detector you are using does NOT attempt to float or recharge the batteries unless you want it to, and if you want it to, do NOT use alkaline batteries.

Finally, alkaline batteries have a different discharge profile than lithiums. An alkaline battery's terminal voltage will decline almost linearly as the battery is discharged, starting at around 1.6V and falling to 1.0V before most devices will stop working or will tell you that the battery needs to be replaced. Lithium batteries will maintain their terminal voltage at 1.5V-1.3V until just prior to being completely discharged. So your smoke detector may be discharging your lithiums just as quickly, but the low-voltage beeper has not yet kicked in due to the flatter discharge profile of the lithium battery. That, and the fact that a lithium AA battery starts out with a lot more capacity than an alkaline AA.
Last edited by sluggo on Fri Mar 22, 2013 2:14 pm, edited 2 times in total.
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Re: 9v smoke alarm battery question

Postposted on Fri Mar 22, 2013 2:12 pm

Thanx Sluggo. Your comments about corrosion make sense - but this was never an issue in my situation.

The info on output dropoff profile and warning beeps is also helpful.

I will look for a problem with the main line power. I am thinking bad part but it may be ac input (though it did seem to work OK for a few months after new install in August.
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Re: 9v smoke alarm battery question

Postposted on Fri Mar 22, 2013 3:23 pm

sluggo wrote:Sorry for the late post, but just wanted to mention that any corrosion on the terminals would lead to decreased current levels, not increased current levels. The batteries would be sourcing less current and would, in theory, last longer.

This would only be true for a purely resistive load. Most battery-operated electronic bric-a-brac these days includes some form of a switchmode power converter in order to draw constant power out of the battery and obtain maximum charge depletion.

The other thing to consider is that a device which monitors source voltage would be detecting premature depletion if a poor contact was a problem, although the OP later clarified that the unit is not just complaining about low batteries, it is running them well and truly dead.
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