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Not sure if this is the right place to discuss and can't find an exact answer in the other discussions.

My smoke detectors were manufactured in 2009 so its time to replace. They are hardwired and linked together which I am planning on keeping so the battery is just a backup.

My question is around the backup battery, does a normal backup battery last longer in these units since they are not supplying power directly such that I could use a 9V lithium for a few years at a time? I'm aware of the discharge curve of these batteries such that once they reach end of life they need to be replaced immediately but I see the risk as relatively low since it is a backup power source.

I know the recommendation is for replacement yearly in both wired and battery powered units, but these sealed units have a supposed 10 year life without needing replacement which I would assume is similar to a normal 9v lithium. Some people say they fail after only a few years so I was thinking by purchasing the models with battery compartments I could easily swap the batteries if need if they fail early but get the same benefit of extended life with lithiums? Does anyone else do the same and how long are they getting out of the batteries?

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  • Your title and your post don't match very well. You ask about device type in the former and battery type in the latter. Please revise to sync that up and keep in mind that matters of opinion (such as device type preference) are off topic here. – isherwood Dec 16 '20 at 22:02
  • I always choose/recommend the lithium 10 year battery over the standard cell battery just for the 10 year difference. Also smoke alarms should be replaced no more than every 10 years from the date on the back (or as determined by manufacturer). – ojait Dec 16 '20 at 23:46
  • I'm going to sound weird and contrary here -- but if they're working fine, why replace them? ("Canned smoke" for smoke alarm testing is a thing, check the manufacturer's docs for a specific product rec) – ThreePhaseEel Dec 17 '20 at 1:13
  • Its recommended they be replaced after 10 years. It's a new to me house so I figure I should do it now – redlude97 Dec 17 '20 at 5:48
  • My understanding is the sensors in the smoke alarms use a radioactive element - americium-241 - that decays overtime. 10 years is the point where the sensor using that element is no longer accurate enough. I don't know what the measure is could be 1/1000 smoke detections fails or could be 1/100. If you are relying on the device to save your life $20 every 10 years seems like a small price to pay. – Fresh Codemonger Dec 17 '20 at 7:11
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Looking at the amazon reviews for the Kidde i9010, I do see a fair amount that say it didn't last the ten years. I also see a comment from 2015 that says the battery configuration was changed from 3 to a single which is apparently more reliable.

For the $20-30 I'd risk going with the manufactured one. The comments also seem to say that the support is good and free replacements have been sent out where it didn't last the ten years. I'd hope that whatever the problem was that it has been fixed and they do last ten years. Since it sounds like there was a problem with the smoke detectors meeting the ten year design it will likely be a while before the old stock is gone and bad reviews stop appearing. I don't see any reviews newer than 2018 that comment on the battery life.

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