Smoke detectors and rechargeble batteries

[pcm81]

I have a smoke detector question, two actually:
1. The smoke detectors, Kidde Model i12040 in my house have a 3 wire connector on them, I guess that is the power. Also the 9v battery chirps when about dead. Online I see many posts not recommending rechargeable batteries, due to their lower capacity than alkaline. Can the smoke detector actually charge the rechargeable batteries? Seems like a good idea, Battery keeps the smoke detector up during power outage and smoke detector keeps the battery fully charged when power is up. I do occasionally loose power at night, so alkaline batteries only last about 3 months...
3. My house has a built in sprinkler system. Does the smoke detector actually able to communicate to some central unit (a box in my garage) that will control the sprinkler system, or is there some other sensor (not the normal chirping, smoke detectors) that will engage the sprinkler system?

This is 2011 construction home.

Thanks

 

[mindless1]

No, it can't recharge the battery. This would require a charging circuit which would ruin alkalines, the intended battery. Perhaps a sophisticated enough charging circuit could discriminate between different battery chemistries but there isn't one nor would it be cost effective to build one in.

Certainly you can use rechargeable batteries if you want the burden of having to swap in freshly charged replacements every couple months, but many people would get tired of doing it and just leave it unplugged with the battery out to stop chirping which is the worst possible outcome. Additionally the 6 cell type (7.2V nominal) rechargeable might drop too low in voltage soon enough that you don't even get but a fraction of the capacity from it.

You'll have to consult the documentation for your sprinkler system to determine compatibility but generally no, a Kidde smoke detector only communicates with other hardwired Kiddie smoke detectors.

Yes the sprinkler would have its own sensors, typically on every sprinkler head. Well sensor generally means a mechanical breaking, melting, or plate flexure above a certain temperature, not an electro-mechanical valve that a hard wired smoke detector could set off. It could certainly be designed to do that, but you'd have to get all parts of such a kit from the same manufacturer and it wouldnt' tend to be based around the wear-out/disposible smoke detectors, which are cheap enough to throw away every 10 years unlike that kind of custom setup.

Besides, that's more sophisticated than it first seems because you'd not want sprinklers going off house wide for every thing that sets a residential smoke detector off like burning food while cooking, steam from a shower, or sawdust from sawing wood, or a speck of dust that floated the right direction, let alone the phantom false alarms. I have a hardwired set of the Kiddie PI2010 and do have to cover them with the included shower cap type cover they come with, before doing certain tasks esp. in my work shop.

 

[paperfist]

There's new batteries out for smoke detectors rated for 10 years.

I have 1 detector that is hard wired and the battery was always going dead every 6 months. It's right below my room and it drove me nuts with the voice activation about the battery. Installed the 10 year battery and so far so good. It's been about months now.

 

[mindless1]

^ If it's only been months, how can that be taken as evidence the battery is going to last long enough to be cost effective?

On my PI2010 hard wired units, I get at least 3 years out of a standard Duracell alkaline, but power outages here are infrequent and short for the most part.

 

[paperfist]

^ If it's only been months, how can that be taken as evidence the battery is going to last long enough to be cost effective?

On my PI2010 hard wired units, I get at least 3 years out of a standard Duracell alkaline, but power outages here are infrequent and short for the most part.

I see your point, but I'd be hard pressed to believe a battery labeled 10 year isn't going to last at least 5-6.

 

[C1]

Just go to the state fire marshall's website & buy an approved combo CO/Smoke detector that has 7-10 year batteries. These units are sealed & probably have LiON batteries within.

You dispose of the complete unit when the batteries die.

If you actually read your manual, you find that the sensors of ALL these detectors degrade with time & thus the units need to be replaced notwithstanding at 7 to not longer than 10 year intervals.

 

[mindless1]

^ I feel the opposite though, that if I'm getting over 3 yr, out of batteries the OP is getting 3 months out of, then I don't even see getting 10 months out of one rated for 10 years because the premise of a 10 year lifespan depends on it not being used, that it's a lithium cell which does have higher energy density but not that much higher. What it has more than that is longer shelf life, or more technically I mean lower self-discharge, but it's only relevant if there are no events to drain it which there must be if an otherwise good-for-3+ years setup is only good for 3 mos.

Edit: I am assuming the alkaline batteries were new/fresh when installed. If not, all bets are off.

Ultimately there are too few people that have this issue for there to be a ready made, cost effective (per unit sales) solution. At the same time it isn't rocket science but unfortunately ignorant people with their own personal agenda will thwart best efforts.

lol, now I seem paranoid but let me explain. It's a fairly basic circuit to just build a proper battery charger specific to the device and battery chemistry, to alter their device you could, or at least I could or anyone with some tips, wire it in yourself, but the added cost is too much for the manufacturers' anticipated market, so you have to DIY then when you start altering a fire alarm then if some unforeseen thing goes wrong, or even some fire alarm manufacturer defect, and it's discovered that the owner altered the alarm in any way, then insurance companies and courtrooms will have some arguments to weed out.

 

[DrPizza]

Ultimately there are too few people that have this issue for there to be a ready made, cost effective (per unit sales) solution.

The cost effective solution is to use alkaline batteries. The added cost of the circuitry, plus the added cost of a rechargeable battery is more than the cost of the alkaline batteries over the lifespan of a smoke detector. (IIRC, the lifespan of a detector is 10 years, after which they should be replaced.)

 

[natto fire]

There is a non-rechargeable lithium chemistry that is supposed to last ten years idling. That is much longer than alkaline, and especially carbon-zinc. After 10 years, the Americium in an ionizing smoke detector is supposed to be replaced anyways, obviously not user-serviceable. Photo-electric are a lot more common nowadays, especially in multi-family dwellings, because of their longer life, and lower cost.

Sprinkler system is another beast, but as pointed out, the actual release of water is done mechanically, and then the flow or prevention of flow is monitored electronically. This is done through a tamper/flow switch, which ties into the main fire panel, in my experience. Your locality may vary, but every fire alarm system I have installed requires monitoring of the shutoff valves for each zone, as well as flow switches to detect water going through any of the mechanical outlets in that zone.

 

[mindless1]

^ Yet pcm81 has already informed us that it's not going to be idling the whole time or else the lifespan of alkalines would be a few years instead of 3 months.

This suggests the lithium version wouldn't last 10 years in the same scenario. Alkalines have about 84% of the energy density of lithium primary cells, 210 Wh/kg vs 250 Wh/kg, and certain modern alkalines like Duracells are rated for a 10 year shelf life.

Problem is, their cost/Wh is MUCH higher than alkalines, so with all else equal, a smoke detector deployed in a scenario where it drains an alkaline in 3 months, would drain an equivalent lithium primary in 3.6 mos. That's if a person merely buys a lithium replacement battery instead of alkaline.

Perhaps all else isn't equal, possibly the units with the sealed in battery are twice the capacity so it lasts 7 months or even a year, but it's not supposed to be user replaceable, so it's quite a bit more work and expense to replace the entire smoke detector every year due to the sealed battery depletion, than to just swap in a new alkaline.