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Backup batteries in house alarm external bell?

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Buk

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What kind of power source is my 23 y/o house alarms external ringer likely to contain, such that it still operates having had no maintanence in those 23 years?

Background: I had the alarm fitted when the house was built because I was working overseas and my wife was home alone. It had two annual inspections before the company that fitted it shut up shop due the the owner retiring. He sold his list of mainanence contracts to some other outfit and when the guy came to 'renew' the contract, he was one of those licked and suited high pressure sales people trying to up the ante every which way and demanding that I sign on the dotted line before he would leave. I had to get right up in his face and walk him out before he would shut up and leave. Needoless to say, I didn't sign.

I never took another mainanence contract; so the only thing that has been done beyond occasionally cleaning the sensors is replacing the SLA backup battery about every 6 or 7 years.

It has now started to become unreliable. Triggering randomly on a fairly regurlar basis and indicating one of the sensors was resposible when most time it is easy to prove that they could not have been. eg. It blames "front door open" when it obviously isn't -- my office is right next to the front door.

Upshot: we never use it and I'm fed up with being woken in teh middle of the night, so I want to disconnect it. The only thing stopping me is the external bell triggering when the mains power and battery are disconnected.

Hence the question above, and particularly, how long will the thing continue to ring for?
 
The sounder will last at least an hour.

It will have some NiCd or NiMh batteries, most likely. The charging will probably be a simple trickle charge, and that will be at a very low current as there is no need to charge quickly, so the batteries will probably have quite a lot of their original capacity.

If the system isn't armed, you can take the lid off the external sounder. That will break the tamper circuit, but that won't operate the alarm if it's not armed. With the lid off, you can see the battery to disconnect the connector or to cut the wires to it. Once you've done that, disconnect the SLA battery and the mains, and it's dead.
 
Depending upon the bell and the condition of the battery, it could be a very long time. Can you snip the wires to the bell? Another, less destructive idea is to place a low ohm resistor across the SLA, or disconnect it entirely.

Apparently there is a charger involved, so you would want to disconnect power to that first.
 
Depending upon the bell and the condition of the battery, it could be a very long time. Can you snip the wires to the bell?

You're rather missing the point of the battery - cutting the wires to the alarm will instantly trigger the bell, that's why there's a battery inside the bell. It wouldn't be much of an alarm if you could simply cut the wires to it.

It's quite simple - you turn the alarm OFF by entering service mode (as he's previously replaced the batteries he must have service access), then remove (or disconnect) the batteries from the bell, and from the alarm panel. Then disconnect the mains power to the alarm panel.

Or if he doesn't have access (which sounds unlikely) go up to the bell with a screwdriver and a pair of cutters (and be prepared for a few seconds noise) - there's usually one screw to remove to take the cover off, and there's an anti-tamper switch - so it will start ringing as soon as you remove the cover. Then simply unplug the battery, or cut the wires to the bell or the battery (that's why you take the cutters, just in case).
 
Take the battery out first - then there's no problem.

I should have mentioned: The external box is mount very high up (~7M) on an end wall between the eves. That end wall is about 1 meter from the boundary fence, making the angle 8° or 7:1 which is way beyond any safety limit.

Whilst I have a 5M double extender ladder that I am quite happy to use each year clearing my gutters, its too steep for my nerves.
 
As Diver300 says, it could sound from anything between 10-15 minutes and an hour once external power is disconnected.
(A combination of battery state an local regulations - some limit such sounder actuation to eg. 20 mins).

I'd just warn your neighbours that someone will be working on the alarm and it will be sounding, then cut the wire mid morning on a weekday when it's least likely to upset people...

Some types have some means of disabling the power fail and tamper systems, but you need to know what make and model of sounder system it is, to be able to use that...

If by chance it is a Texecom unit with separate wires for the bell/sounder and a strobe light: Briefly trigger the strobe by connecting that wire to negative, three times within 30 seconds. That disables the tamper and power fail.
 
I should have mentioned: The external box is mount very high up (~7M) on an end wall between the eves. That end wall is about 1 meter from the boundary fence, making the angle 8° or 7:1 which is way beyond any safety limit.

Whilst I have a 5M double extender ladder that I am quite happy to use each year clearing my gutters, its too steep for my nerves.

That makes life rather difficult then - I presume (as I've previously assumed) you've got the service code to access the alarm box? - first job would be to shut it down, that will stop the spurious alarms.
 
I presume (as I've previously assumed) you've got the service code to access the alarm box? -

Actually, you don't need it to replace the SLA. The user code shuts the alarm off, and the display then tells you what the fault is and requires the user code again to reset the fault. So, remove the lid, shut the alarm off, but don't clear the tamper fault, and you have something 30 minutes before it times out and sounds the alarm again. Plenty of time in which to change the battery and get the lid back on.

first job would be to shut it down, that will stop the spurious alarms.

Depends what you mean by "shut it down"?

The alarm does not have to be enabled -- it never is -- for it to trigger, if it thinks something is being tampered with; even when it obviously isn't.

There does not appear to be a 'disable everything' command, even on the engineers menu. There is a "engineer on site" command, but that doesn't appear to work for my system. I have the install manual to a slightly different model to mine,. Most stuff works, some doesn't.

I do have an engineers code. At least it is hand written on the installation paperwork as that; but it does not work.

I also have the default engineer and user codes, and a procedure to reset the NVM. Trouble is, the diagram showing where that is located does not marry up to a removeable chip on the board I have. I suspect it may be in the keypad controller rather than on the main board; but I haven't worked out how to open the keypad cover. And each attempt triggers the alarm.
 
Actually, you don't need it to replace the SLA. The user code shuts the alarm off, and the display then tells you what the fault is and requires the user code again to reset the fault. So, remove the lid, shut the alarm off, but don't clear the tamper fault, and you have something 30 minutes before it times out and sounds the alarm again. Plenty of time in which to change the battery and get the lid back on.



Depends what you mean by "shut it down"?

The alarm does not have to be enabled -- it never is -- for it to trigger, if it thinks something is being tampered with; even when it obviously isn't.

You need to shut it down on the engineers menu - while it might not be enabled the anti-tamper side still obviously is, not much use if the anti-tamper is disabled by the customer.

However, if you don't have the right instructions or codes, then you're a bit stuffed.

Might be easier to repair the fault - presumably on the anti-tamper wires?. You could always bypass the anti-tamper circuit inside the box.
 
If by chance it is a Texecom unit

Its a scantronic, and having taken a picture of the very faded installation table on the inside of the control box lid and tweaked the contrast and stuff, I can now read it says that the alarm duration is programmed to 20 minutes. Which isn't so long that the neighbours would get upset if I time it right.

1628866404373.png
Thinking of waiting till my immediate nextdoor neighbours go out and doing it then.
 
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There is normally only one tamper circuit for the whole system. You could short that out at the panel, and then open the bell without the alarm going off.

Notice on the faded installation table, there's a space for 'tamper resistance' - it's a common practice to have resistors in the tamper circuit so you can't just short it out, as an obvious safety precaution.

So he would probably need to fit a resistor rather than a shorting wire?.
 
then open the bell without the alarm going off.

As I described in #6, the problem is getting up to the bell.
I can easily just turn the power off which stops the everything; except for the self activating bell.
Now I know how long that is likely to persist, I'll just choose my moment when it is least likely to annoy anyone.
As I will be cutting the power to everything, the SAB batteries will not be recharged and that'll be the end of that.
 
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