9v ni-mh 7.2, 8.4, 9.6 ?

Guys,

For a smoke detector which rechargeable ni-mh voltage would be best?

Thanks,

John

Being that the detector "runs" 24 hours a day i'm not sure what voltage would be best. Anyone have any idea?

None. Rechargeables lose their charge WAY too fast for smoke detectors. Use standard lithium 9v's.

john2551,

I would believe 9.6v would work fine for most detectors.

On the other hand, NiMH are poor choice for a smoke detector type application. NiMH have a fairly quick self-discharge rate and are best suited to high current draw devices. Recharging the detector batteries every 2 weeks doesn't seem logical. A smoke detector is best powered by a standard alkaline or lithium 9v.

Just my $.02.

I use these:9.6V in my smoke alarms but sometimes you have to be careful as the plastic holders are a bit tight for these slightly fatter batteries! The detector will chirp if the battery is low. If it worries you, go with a lithium like suggested above.

Okay, I checked both of my smoke alarms. One had a alkaline which measured 8.2V, 60% on a ZTS battery tester and self tests fine. The other alarm had the MAHA PowerEx Ni-MH 9.6V that has easily been installed for a month, reads 10.1V and self tests fine too. I'll make a note of how long this battery lasts.

wptski said:

Okay, I checked both of my smoke alarms. One had a alkaline which measured 8.2V, 60% on a ZTS battery tester and self tests fine. The other alarm had the MAHA PowerEx Ni-MH 9.6V that has easily been installed for a month, reads 10.1V and self tests fine too. I'll make a note of how long this battery lasts.

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Bill,

I was using L522 Energizer lithiums & was surprised at the poor performance of them going dead after several months. The runtime seemed comparable to an alkaline. Being i have the Ansmann Energy-16 i don't mind charging them up every month or so. I have an iPowerUS 9.6v 250mah battery but can't seem to find them for sale any longer.

Thanks,

John

I'm wary of using rechargeables on my fire alarms. It'll be interesting to see if rechargeables can be a reliable alternative in these types of applications.

A rechargeable LiIon seems like a better choice as compared NiMH/NiCD though.

mina said:

I'm wary of using rechargeables on my fire alarms. It'll be interesting to see if rechargeables can be a reliable alternative in these types of applications.

A rechargeable LiIon seems like a better choice as compared NiMH/NiCD though.

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mina:

If there was any danger, I wouldn't be using them either!

john2551:

The PowerEx Ni-MH 9V battery still works with the smoke alarm test button!

wptski said:

john2551:

The PowerEx Ni-MH 9V battery still works with the smoke alarm test button!

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Bill,

I have L522 Energizer Lithiums in my smoke detectors now. When they go dead i'll be switching over to 9.6v Ni-mH cells.

Regards,

John

stay with lithium in your smoke detector.

nimh self discharges too fast

markdi said:

stay with lithium in your smoke detector.

nimh self discharges too fast

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Mark,

No offense, but i spent ~$150 on an Ansmann Energy-16 charger less than a year ago & i WILL get good use out of it. I don't care if i need to charge them up ever 1-2 weeks! I will use this charger often! I've bought other "gadgets" in the past only to sit on a shelf for years. I'm not going to let that happen with this.

Regards,

John

john2551 said:

Mark,

No offense, but i spent ~$150 on an Ansmann Energy-16 charger less than a year ago & i WILL get good use out of it. I don't care if i need to charge them up ever 1-2 weeks! I will use this charger often! I've bought other "gadgets" in the past only to sit on a shelf for years. I'm not going to let that happen with this.

Regards,

John

Click to expand...

John:

I use a MAHA MH-C1090F charger on my PowerEx batteries. I was reading a while back "somewhere" that the self discharge data on Ni-MH cells is a bit dated and the thought was that they have improved. I have no proof either way though!

Time for a battery status update! Test button still works and the PowerEx 9.6V checks at 9.99V.

john2551 said:

Mark,

No offense, but i spent ~$150 on an Ansmann Energy-16 charger less than a year ago & i WILL get good use out of it. I don't care if i need to charge them up ever 1-2 weeks! I will use this charger often! I've bought other "gadgets" in the past only to sit on a shelf for years. I'm not going to let that happen with this.

Regards,

John

Click to expand...

That's a lousy excuse for using NiMH batteries in a smoke detector, which is considered a rather reliability critical device. Smoke detector battery lasts a while and a really long time for an AC powered model with 9V battery backup for power outages.

Handlobraesing said:

That's a lousy excuse for using NiMH batteries in a smoke detector, which is considered a rather reliability critical device. Smoke detector battery lasts a while and a really long time for an AC powered model with 9V battery backup for power outages.

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A flashlight is a "reliability critical device" when used by law enforcement too and I'm sure they use rechargables as they do in their radios also!

Yes, if something is AC powered with a battery backup, the battery would last a long time! That's a no-brainer.

wptski said:

A flashlight is a "reliability critical device" when used by law enforcement too and I'm sure they use rechargables as they do in their radios also!

Yes, if something is AC powered with a battery backup, the battery would last a long time! That's a no-brainer.

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Yes, but they're used and charged daily. NiMH is not a reliable source of power in standby. You don't see an emergency kit with NiMH and instructions saying "please charge once a month" do you? Backup battery on an AC powered smoke detector would not last long at all if the battery has significant self discharge while standby, so for this application, the inherent characteristics of NiMH is detrimental to system reliability.

Handlobraesing said:

Yes, but they're used and charged daily. NiMH is not a reliable source of power in standby. You don't see an emergency kit with NiMH and instructions saying "please charge once a month" do you? Backup battery on an AC powered smoke detector would not last long at all if the battery has significant self discharge while standby, so for this application, the inherent characteristics of NiMH is detrimental to system reliability.

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You always carry spares be it primary or rechargables. Alkalines have been around for a long time, so that's what you get in a emergency kit. Maybe they'll have a car charger for a emergency batteries in the future. As far as Ni-MH not being reliable! This PowerEx 9.6V has been installed since 11/05 at least and I'd call that very reliable. Maybe these small eight cell packs have a much lower self discharge rate than other cells?

I just checked five PowerEx 9.6V cells charged on 3/30/06, all read 10.3V. I don't remember what a battery comes the charger at or after a rest. If this battery in my smoke detector has only dropped to 9.99V from at 11/05! This speaks for itself I'd say!!