Rechargeable 9V for Smoke Detector

[moldyoldy]

ref detector current draw: An ionization detector draws very little current. A smoke detector uses a small "light" to detect hazing of the atmosphere inside the chamber - which draws more current. Then the CO detectors which lately use AA cells draw still more current. Finally the gas detectors draw the highest current of all.

What are some actual currents? no real idea except by observation of battery life and some calculated guesses. I no longer have a 'scope and my fast Fluke DMM failed years ago so I am not able to measure the pulse of current when the detection is turned on.

Edit: I eliminated nearly all of my ionization-only detectors in favor of the combo systems. There is considerable evidence concerning slow smoldering fires and the slowness of ionization-only detectors to sense the "fire".

 

[HarryN]

My (very limited) experience with house fires is that even a fairly small one will pretty much ruin the house and most of the contents. It is not so much the fire, as the smoke - its just insidious and tenacious.

We use smoke alarms as a way to warn us to get out, not to save the house / contents. The fire depts. in CA operate this way as well, pretty much just contain a fire to keep it from spreading to other homes, rather than really focus on trying to save anything.

 

[45/70]

Lithium cells are more sensitive to low temperatures? really? In my experience it is not true at all - alkalines and Ni-mh don't work at low tempteratures but lithium cells work just fine.

As far as I know you're correct. Without looking it up, as I remember, alkaline cells begin to drop in performance when their simply "cool", not even "cold". NiMH cells do pretty well down to freezing temps, or maybe a bit lower, NiCds do a bit better. Lithium primary cells on the other hand, hold up well at temps well below freezing.

Lithium-Ion cells on the other hand fall into about the same category as nickel based cells. As the technology advances though, they're getting better, at low temps.

One question though, I thought I was the only one that had rooms in their house with Winter temps below freezing! I wouldn't think temperature in the location of most folk's smoke alarms would really be much of a concern, as far as battery type anyway.

Dave

 

[WDG]

There has been some discussion a few years back on this topic here: 9V NiMH only 7.2V?
And here:Are there any NIMH low discharge 9 volt batteries?

The short answer: Use Alkalines, changed twice a year, unless you're willing to go to a good deal more trouble and/or expense. They're relatively inexpensive, compared to rechargeables, and will still have plenty of reserve to power the alarm when you change them every six months.

In general, alkalines give the best cost/safety value in this use.

The lithiums are great, but expensive and have a steep end of life curve that could cause you to miss a low battery alert. I have used them in the past, and concluded they were not worth the expense for this use. I would probably change these annually, if I were still using them.

Rechargeables should only be trusted if you're willing to religiously recharge them monthly, else they might not have enough juice left to power the alarm in an emergency. Also, not all "9v" rechargeable batteries are actually 9 volts. This may or may not be a factor, depending upon the design of the alarm.

That said, I use iPower 9v li-poly rechargeable batteries (about 500mAh) in ours. I recharge these monthly, so they've got plenty of reserve to power the alarm when called upon. This is probably the single most expensive way to power a smoke/CO2 alarm, so I would never have purchased them for this application. These are extra batteries I happened to already have for powering wireless mics & radios.

 

[jruser]

I don't know anything about it, but my detectors are wired into what I assume is AC power and maybe networked with the other detectors.

When I moved in, all of the detectors were running some "Super Heavy Duty" generic 9v batteries. 2 of them have since died, which I replaced with Duracell. In another 1 of them, I replaced the battery with one of the Maha LSD 9.6v batteries as a test around 18 months ago. It still hasn't started giving me the low beep.

 

[901-Memphis]

I don't know anything about it, but my detectors are wired into what I assume is AC power and maybe networked with the other detectors.

When I moved in, all of the detectors were running some "Super Heavy Duty" generic 9v batteries. 2 of them have since died, which I replaced with Duracell. In another 1 of them, I replaced the battery with one of the Maha LSD 9.6v batteries as a test around 18 months ago. It still hasn't started giving me the low beep.

LSD 9v rechargeable might be good if you have AC power and the battery is only for backup, but its something i would still keep an eye on to check your cell and make sure they are healthy. Using a rechargeable in a dc only detector is a whole nother story.


Even if you have a/c power detectors and you have frequent power outages you may find yourself draining the cell often. I guess one could say it varies by application. Persoannly i use Rayovac 9v alkaline since they are one of the better price to performance out there.

 

[Sub_Umbra]

If a rechargeable is chosen, insure that it is of a standard form factor and will, in fact, fit in the alarm. Non-standard form factors seems to be a recurring issue with 9V rechargeables.