9v ni-mh 7.2, 8.4, 9.6 ?

[Lynx_Arc]

If the smoke detector chirps when low like most due I don't see too much wrong with using nimh if it is in a high traffic area and you check it once or twice a month.
If the battery has 8 cells when it is nearly dead is probably will still put out around 8v so you may want to be careful not to overdischarge it. I often wonder why not make a smoke detector that uses 4AAA or AA instead.... would probably run for a long time I think I saw one that used 3AAA once but after getting a caller ID box that uses 3AAAs an having it blink change battery after 3 months I wonder if they used 5v parts.

 

[john2551]

Bill,

Mine are also going strong after 3 months with the iPowerUS 9.6v cells.

John

 

[wptski]

Bill,

Mine are also going strong after 3 months with the iPowerUS 9.6v cells.

John

John:

Yes, these batteries seem to work perfectly in this application. So much for the self discharge with Ni-MH cells at least with these batteries!

 

[wptski]

Here we go, at least seven months, maybe eight months! PowerEx Ni-MH 9V, smoke alarm self test still works and battery reads 9.876V. Did somebody say something about having to charge every couple of weeks because of self discharge? :laughing:

 

[john2551]

Bill,


I guess the PowerEx 9.6v are better than the iPowerUS 9.6v because my detector started to chirp after ~6 months. But i charged it right up & put it back in a while ago & still going strong. So charging it twice a year is no big deal for me.

John

 

[Handlobraesing]

I would say don't use NiMH in smoke detector. How long does a new alkaline last? How much does that cost a month? 10 cents?

 

[wptski]

Bill,


I guess the PowerEx 9.6v are better than the iPowerUS 9.6v because my detector started to chirp after ~6 months. But i charged it right up & put it back in a while ago & still going strong. So charging it twice a year is no big deal for me.

John

John:

I had a bunch of IPower 9V too! Pure junk!!

 

[Norm]

There is no way I would be trusting my life to a rechargeable battery there are some applications where rechargeable are not the best choice. For things with very low current draw smoke detectors etc. Things that are standby devices such as a torch stored with the tool kit in your car or a torch in your emergency kit. These applications require a battery with a long shelf life. The self discharge of a rechargeable used in a smoke detector would probably mean it wouldn't last the year out.

 

[wptski]

I would say don't use NiMH in smoke detector. How long does a new alkaline last? How much does that cost a month? 10 cents?

Why would you say that? That's the point of this long term real life test. Others above stated the self discharge would make the batteries useless. These batteries appear to be better.

No point in getting Ni-MH just for this application but if you use them elsewhere, they work just fine.

Don't give me the alkaline crapola, you use rechargables, right?

 

[wptski]

There is no way I would be trusting my life to a rechargeable battery there are some applications where rechargeable are not the best choice. For things with very low current draw smoke detectors etc. Things that are standby devices such as a torch stored with the tool kit in your car or a torch in your emergency kit. These applications require a battery with a long shelf life. The self discharge of a rechargeable used in a smoke detector would probably mean it wouldn't last the year out.

The point is, "can" you use the batteries. Some people, their life depends on a two way radio. Do they use rechargables, of course!

 

[Norm]

The point is, "can" you use the batteries. Some people, their life depends on a two way radio. Do they use rechargables, of course!

Sure you can use them but a two way radio doesn't have to run continuously for twelve months on one battery charge. You could use ni-mh in your car but it's not really suitable for the application. Just becase something may work is not a reason for choosing to do it. The different characteristics of diferent types of batteries makes them better suited to certain applications. Please feel free to use whatever batteries you wish.

 

[wptski]

Before anymore anti-Ni-MH replies, here is the first post.

>>>>
Guys,

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

Thanks,

John
>>>>

It doesn't ask, which battery but which rechargable!

 

[wptski]

Sure you can use them but a two way radio doesn't have to run continuously for twelve months on one battery charge. You could use ni-mh in your car but it's not really suitable for the application. Just becase something may work is not a reason for choosing to do it. The different characteristics of diferent types of batteries makes them better suited to certain applications. Please feel free to use whatever batteries you wish.

The question wasn't "what kind of battery should I use?" The type was already selected. This wasn't a battery application question.

 

[bob_ninja]

I have a 9V NiMH in mine and it doesn't last long, about a month or so.
The low power beep is loud enough plus the test button can be used to check it, so no problems there.

I was wondering about using the older NiMH AAs, say 7 x 1.25V = 8.75V (2 x 4AA holders) instead. A typical degraded 2Ah NiMH AA will still have say 1.5Ah which is well above the 9V NiMH capacity. This would be a graveyard for AAs. I assume a low poer draw from detector, hence older AAs will still work fine.

Regarding voltage, not sure if 9.6V would be safe, so I'd stick to the 8.4V range.

 

[wptski]

I have a 9V NiMH in mine and it doesn't last long, about a month or so.
The low power beep is loud enough plus the test button can be used to check it, so no problems there.

I was wondering about using the older NiMH AAs, say 7 x 1.25V = 8.75V (2 x 4AA holders) instead. A typical degraded 2Ah NiMH AA will still have say 1.5Ah which is well above the 9V NiMH capacity. This would be a graveyard for AAs. I assume a low poer draw from detector, hence older AAs will still work fine.

Regarding voltage, not sure if 9.6V would be safe, so I'd stick to the 8.4V range.

The 9.6V is nominal at 1.2V per cell. Off my MAHA charger, the MAHA PowerEx check around 10.4V resting. Hot off the charger, they are higher. No problem using them. I think that I have them in both of my alarms. Use them in clamp amp probes, etc., whatever they fit into as they are a bit fatter than a standard alkaline!

 

[Norm]

The question wasn't "what kind of battery should I use?" The type was already selected. This wasn't a battery application question.

Agreed

 

[eluminator]

All I know is I have an 8.4 volt in my multimeter. It works fine and gives a longer life between charges than I expected.

The higher the voltage, the more cells it must have. That means the cells must be smaller. The cells are absurdly small anyway, so I figure the 8.4 might be better than the 9.6.

 

[Handlobraesing]

Why would you say that? That's the point of this long term real life test. Others above stated the self discharge would make the batteries useless. These batteries appear to be better.

No point in getting Ni-MH just for this application but if you use them elsewhere, they work just fine.

Don't give me the alkaline crapola, you use rechargables, right?

It would be fine for your experiment prototype, but certain not for a smoke detector in service. Another problem with NiMH is the lack of end of life signal. Alkaline slopes off gradually and gives you enough time to respond to the chirping, but NiMH drops so quickly in voltage that you might lose the chirping after a day or two while you're away for the weekend and the such.

 

[wptski]

It would be fine for your experiment prototype, but certain not for a smoke detector in service. Another problem with NiMH is the lack of end of life signal. Alkaline slopes off gradually and gives you enough time to respond to the chirping, but NiMH drops so quickly in voltage that you might lose the chirping after a day or two while you're away for the weekend and the such.

Gee, what if you went on a two week vacation and were using alkalines??

 

[john2551]

Before anymore anti-Ni-MH replies, here is the first post.

>>>>
Guys,

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

Thanks,

John
>>>>

It doesn't ask, which battery but which rechargable!

EXACTLY! Thanks Bill!