Alarm Powercut Issue

Talk Electrician Forum

Help Support Talk Electrician Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

RedArcher68

Member
Joined
Oct 24, 2020
Messages
11
Reaction score
3
Hi - I have a alarm question and wondered if you can help. Embarrassingly we had a powercut in the early hours of this morning sounding the external siren, and with no power there was no way to deactivate the alarm, I then thought about removing the battery from the main-unit but when I disconnected the 12v battery nothing happened!! I’m guessing the siren has its own battery.

Ok I just put a multi-meter on the battery with a reading of 13.2.

If the battery is in the range of ok how do I stop the alarm sounding when we have a powercut (SSE have an issue in the area which could take 6 months to resolve, and we’ve had a few (just not at night)).

I thought it was a dead back-up battery?

Any advice would be welcome 

Rdg RedArcher68

 
There is something wrong. I don't think a mains power cut should trigger alarm. It should just give a local (internal) warning light or tone to let you know its lost power.  

When you open the case there will be a tamper switch and that WILL trigger the alarm.

Yes the siren box will have its own battery but it will only be a small one which will either run down or time out in about twenty minutes.

There are others on here who know a lot more about alarms than I do and someone may be able to advise you how to prevent the initial problem. A likely question will be what make and model you have.

 
The external siren has a built in rechargeable battery that only has one function...

To operate the alarm / strobe...

If the external siren cannot see a charge voltage coming from the panel it will assume the system has been tampered with and sound the alarm.

The siren battery can keep an external bell box operating for a significant length of time....

(otherwise it would be useless as an alarm if it fails quickly due to power-cut).

You cannot test the internal battery with just a multi-meter..

You need to put it under load..

A dead battery can show an apparent good voltage..

But as soon as you put it under load it drops significantly ..

The symptoms you describe suggest the battery is well past its expected lifespan..

( Most makes of sealed 12v alarm battery have manufactures recommendation to replace them around every 5 years. )

If the battery was good.. a power cut would make no difference to the system.

to put into context if you wanted an accurate test of the batteries capacity you need something a bit more expensive..

http://www.actmeters.co.uk/battery-testing/612-6v-12v-battery-tester

A cheaper way to test the battery under load is to measure it connected in circuit inside the alarm panel with the mains turned off..

Few months back had a battery showing 12.7 with no load & a basic multi-meter..

Under load in the panel watched it drop down below 9v within 60 seconds of turning the power off.

I would double check your battery before doing anything else.

Guinness

 
Last edited by a moderator:
Thanks to those that replied, I’ve been out most of the day. 

The alarm was install by a friend of the family who’s not local anymore. 

The date on the battery (hand written) is 02/17 which is roughly the time it was installed. 

I tested the battery disconnected from everything.

 
So you need to test it under load...

No load measurements with a multi-meter proves very little..

Installed Feb 17..  So over three & half years in service..

Could still be duff by now..  unable to hold its charge.

(also most of the sealed alarm type batteries tend to have a manufactures date code on them as well.)

Until the battery has been proved under load conditions..

It is still the prime suspect in my book.

Guinness

 
Not worth messing around with load testing, for what they cost stick a new battery in and pretty much guaranteed to sort it. Most of the batteries are rubbish shipped over from china now and have a very limited lifespan.

Half of our estate is a few years older than the other half, all had the alarms installed from new. Power cuts are common, majority of the slightly older houses the alarms go off, another year or two and it'll be the entire estate doing it. They just need a new battery in but Joe public never use the alarms, so don't want to pay to have them maintained and would rather put up with the sound of 15 houses alarms going off every time there's a power cut rather than paying for new batteries  headbang

They'd be far better disconnecting them and saving the electric of it running on standby. The insurance isn't valid if you claim to have one but then don't maintain it, nobody bothers at the sound of alarms anymore, unless they're dialling out they're pretty much useless.

 
Thank you all

I bought a new battery today, however I didn’t have a chance to install it today. Will do it tomorrow and let you know once I’ve tested it.

ta

RedArcher68

 
Top