Rechargeable 9v Batteries in Smoke Detectors

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eracode

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Topic # 90883 2-Oct-2011 10:54

I have DSE home-brand rechargeable batteries in our smoke detectors at home. These "9v" batteries are actually 8.4v and 250mAh.

They only last for a 4-5 months before the detector starts chirping to say the battery needs recharging. With five detectors I'm recharging one battery or another frequently and it has become a bit of a PITA (but it's still worthwhile given the high cost of non-rechargeable 9 volters).

Is this frequency because they are only 8.4v or is it down to the mAh? Googling just now I see that you can get 9.6v rechargeables which the suppliers claim you can use in just about anything that needs 9v i.e. in gear where 8.4v can't be used. I also see you can get rechargeables with, say, 500 mAh.

Would appreciate thoughts.

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Reply # 528192 2-Oct-2011 10:58

I guess it's the voltage, not the capacity. I find standard batteries last a year, and I only have two alarms, so that's fine for me.

You can get good 9V batteries cheap, at least on ebay, maybe you can find something similar in NZ, or that will ship here

http://www.ebay.com/itm/9-Volt-9V-Duracell-ProCell-Batteries-12-Pack-Free-Ship-/270771094104?pt=US_B...

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sbiddle

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Reply # 528196 2-Oct-2011 11:06

I would never use rechageable batteries in a smoke alarm and the instruction manuals for most clearly advise they shouldn't be used.

Rechargeable batteries aren't suitable for many things because of their high self discharge rate. A typical NiMH rechargeable battery could be complete flat from self discharge in ~6 months. If you want long term storage you need to specifically buy low self discharge batteries. Many have an immediate voltage drop off when they near the end of their charge, meaning the chirp to advise of a flat bettery may not occur, or if it does may only occur for a very short period of time.

To be honest anybody buying smoke alarms now should just buy the ones with built in Li-Ion batteries, 10 years battery life for $30 makes them far better value than a standard smoke alarm. Considering smoke alarms have a finite life anyway and "best before date", at 10 years you just throw it out and buy a new one.

Ditch the rechargeables and buy zinc carbon or alkaline 9V batteries (plenty of good deals around in the $2-$3 range if you look) or LI-Ion smoke alarms.

timmmay

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Reply # 528202 2-Oct-2011 11:12

Good point about the self discharge, I forgot about that. I use Eneloop batteries for some of my flash equipment, not sure if they do a 9V version, but I wouldn't use them even if they did.

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freitasm

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Reply # 528208 2-Oct-2011 11:23

Link to these long life smoke alarm with Li-Ion batteries please?

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sbiddle

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Reply # 528210 2-Oct-2011 11:24

Don't have a link online but all major retailers should have them, I know Bunnings do.

Edit: Bunnings have them on their website http://www.bunnings.co.nz/products_product_photoelectric-smoke-alarm_3040.aspx I'm not sure of their price but they are only around the $30 mark.

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Reply # 528211 2-Oct-2011 11:27

Link to another NZ company selling them http://firemaster.co.nz/Online-Store/Product-Range/Product-Details/_cat2_/74/Smoke-Alarms/_prod_/Fla...

timmmay

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Reply # 528212 2-Oct-2011 11:31

Consumer recommend
- Orca SafetyAce OM PE10 LL (OM588H model has one year battery) - and some other Orca models so it's probably a good brand
- First Alert SA710CN (also appears to be a good brand)

And a few others.

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dontpanic42

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Reply # 528222 2-Oct-2011 11:47

If you do feel the need to go with rechargeable 9V batteries in your smoke alarms, these would be the ones to get.

9.6V Low Self Discharge (i.e. 85% capacity after 1 year)

Best thing is that it is a local supplier, and they give quantity discounts.

You would also be best to grab the correct charger if you did decide to stay on the 9V rechargeable route.

eracode

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Reply # 528248 2-Oct-2011 13:01

timmmay: Consumer recommend
- Orca SafetyAce OM PE10 LL (OM588H model has one year battery) - and some other Orca models so it's probably a good brand
- First Alert SA710CN (also appears to be a good brand)

And a few others.

Thanks for all the comments - there's a bit to think about here.

Counting again we have six alarms. Four of those are the photo-electric First Alert SA710CN models mentioned above - they're fairly new and I know they are a good product. I don't want to ditch them but will stop using 8.4v rechargeables in those.

The other two are pretty old and I didn't know about the limited life/best-by thing. Will replace these with new ten-year sealed-battery type.

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Reply # 528249 2-Oct-2011 13:07

The expected useful life of a smoke alarm is 10 years, ie it should be replaced with a new one after 10 years, regardless of whether you're regularly changing the batteries.

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Reply # 528255 2-Oct-2011 13:34

dontpanic42: If you do feel the need to go with rechargeable 9V batteries in your smoke alarms, these would be the ones to get.

9.6V Low Self Discharge (i.e. 85% capacity after 1 year)

Best thing is that it is a local supplier, and they give quantity discounts.

You would also be best to grab the correct charger if you did decide to stay on the 9V rechargeable route.

Imedion are good. At $18/battery and $40 for the charger that'd buy a lot of standard 9V batteries.

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richms

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Reply # 530487 7-Oct-2011 10:10

IMO its as much a false economy to use rechargeable batteries in alarms as it is in cheap remotes that come with TV's etc - and in those things the rechargeable's lower voltage vs alkaline batteries makes them really directional.

I have some nickel zink rechargables on the way from the US to have a play with, wonder how their higher voltage will go with remotes and getting the range and directionality problems sorted ;)

It seems that NiMH cells also die in no time, used or not compared to older lower capacity NiCD ones - I have some 20+ year old 500mAh AA sized ones that still test to just under 400, compared to some 5 year old 2300 AA NiMH's that are now sitting on about 1000 and are dead in 2 weeks off the charger.

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Reply # 530500 7-Oct-2011 10:32

Be really careful with those NiZn cells. Lots of photographers used them in their flashes, got really good recharge times, but many flashes blew up. Some models can handle it, some can't. There were lots of problems with faulty cells too.

If your NiMH cells are dying it probably means they haven't been treated correctly. Every 10th charge you're meant to do a refresh cycle, and if the cells capacity falls significantly you should do a break in cycle. The Maha C9000 charger's excellent, in NZ it's more than $100 but it's worth it. I have a C801 as well, which does charging and the refresh cycle, but no break in. The break in cycle takes 2-3 days per set of 4 cells.

I have 30+ five year old PowerEx 2800mah cells that all still rate at 2600mah or better, because i've used a good charger and treated them well.

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richms

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Reply # 530511 7-Oct-2011 11:06

The problem is nimh are not sold as needing that, most just come with a trickle charger or worse, a timed charger like the energizer ones.

I have tried running them thru a couple of charge/discharge cycles off the hobbycharger but that is just a tempory gain in capacity and they are still dead within weeks. and on the "9v" ones there's no way to do each cell separately which is where most of my failures have been, at least with the AA's I can group them by capacity that they actually give so I have vaugely matched packs.

Im sticking with panasonic from now on for rechargables, the energizer and GP ones are all the ones that are shot, even unknown ebay ones are outperforming them

Richard rich.ms

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Reply # 530512 7-Oct-2011 11:12

Im sticking with panasonic from now on for rechargables, the energizer and GP ones are all the ones that are shot, even unknown ebay ones are outperforming them

That's bad! Shows the sort of cr@p we're getting pushed onto us in the local market! Must start replacing my Energizer ones with Panasonic ones.

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