Is it ok to use a rechargeable battery in a smoke alarm?

zoe

I was going to put a rechargeable 9 volt battery in my smoke alarm but someone was telling me that they read somewhere that a rechargeable battery should not be used in a smoke alarm, though they can't remember why this is.

Is this true?

Alun

I use a rechargeable in mine. Can't think why they shouldn't be used tbh.

magicbastarder

possibly because they're more expensive.
rechargables are best suited to high-drain usage, whereas smoke alarms are low drain. someone once told me (can't verify it as fact) that it's cheaper to put cheap single-use batteries in a smoke alarm than use a rechargable. this may have been changed by falling prices for rechargables.

anyway, the issue wasn't a technical one.

Stoner

yeah it will work just fine, but as noted above a normal battery is the way to go,

but better again are the Eterna mains operated ones with battery back up,

typically they can be looped of a lighting circuit and they last for ages

hobie

Whenever you replace a battery .... sellotape a small slip of paper with the date of installation on it ....

you will be amazed just how long good quality regular batteries last compared to cheap ones ............ how much longer re chargeable Ni-MH compares to Ni-Cd

I use re chargeable batteries in clocks and radios but always us the best quality regular batteries in smoke alarms .......

just my way ......

10-10-20

I think that good guidance would be to follow the manufacturers instructions in this matter. Many specify the battery type and I've never seen a reference to a rechargable battery.

I can think of two reasons why they may not be suitable:

1. Unlike standard cells, rechargable batteries maintain their voltage, but not their current, meaning that the usual method of detecting a low battery is invalidated. A rechargable 1.2v AA cell will read 1.2v untill very near the point where it's fully drained. A standard cell will read ~1.6v, dropping down to >1.0v near its end of life.

2. The rechargable cell has a loss factor of approx 1% per day. A standard cell does not.

Oh, and a third:
3. A rechargable cell will have a reduced service life as a result of the infrequent recharge/discharge cycles. Citing a maximum cycle count of 1000 on most batteries (200 is more realistic I suspect), this will be reduced significantly and will be limited by the cell chemistry which will break down before 20 or so recharges (approx 10 years).

So, for safety's sake, use the manufacturers quoted type of cell in the alarm. :-)

arghh

wow took it for granted that they would be the same thanks for the info

CJhaughey

You can get special lithium 10yr longlife smoke alarm batteries.
Not sure but the new energizer lithium may be something similar.

here ya go:
http://www.amazon.co.uk/Ultralife-Lithium-PP3-Battery-pack/dp/B000Q5MQPG/ref=sr_1_6/202-8597352-0239024?ie=UTF8&s=electronics&qid=1183719143&sr=8-6

Alun

Well, all I can say is that I've been using a 9V rechargeable battery in my own smoke alarm for the past 5 years with no problems whatsoever. I test it very couple of weeks, and it even goes off every now and then when someone burns the toast. I'd say, on average, it lasts a year before it needs recharging.

I'm well aware of all the problems associated with rechargeables, including self-discharge, different discharge characteristics etc, but the proof of the pudding is in the eating, as they say, and it works fine for me. Sometimes theory and practice don't always match up.

10-10-20

Alun, I agree, it will work, but you are increasing the risk of a fault by not adhering to the specifications!