Replacing backup battery in a house alarm - advice needed!

14 Mar 2007
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United Kingdom
Whenever there is a powercut at my mother's house, her alarm goes off as soon as power is restored. A neighbour thinks this is due to the rechargeable battery inside the system having run down.

The alarm was installed about 10 years ago through a local Police Inspector who was connected with the Neighbourhood Watch Scheme. He has long since retired and my mother has very little paperwork concerned with which company fitted the alarm or advice on troubleshooting (though she is adamant this was all she was given by the Police Inspector!!) I think it is an ADT alarm, but cannot remember which model, and what little instructions there are simply say that the alarm comes with a 12v rechargable battery, but no details on how to replace it or why the alarm goes off when there is a general powercut.

Is it just a simple case of turning off all power to the house, unscrewing the control panel in the kitchen, replacing the 12v rechargeable battery (are they easy to buy?) then screwing the cover back on and restoring the electricity? I did suggest to her that she should maybe get the system overhauled by a professional company considering it is about 10 years old and that they could answer why the system goes off after a powercut, but she is in her late 70's, on a pension with no spare cash. Whilst I am more than happy to paint walls, cut the hedge, saw branches off trees for her, and do other odd jobs when I vist, I have no experince of dealing with electrics or alarm systems.

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check to see if there is a wee glass fuse, if this has blown it will not let the battery charge. That happened in my alarm when i thought it was the battery
You could relace the battery by turning off power to the alarm no problem but you could then find that the new battery isnt charging up due to a fault somewhere in the panel.
Im sure BnQ, wickes etc do the batterys, just take a note of what one you need from your old one ( not sure if they are all the same rating ) but its probably a 12v one
Failure of the battery in the control panel is the most common but not the only cause of this.

Batteries are almost always a lead acid gell battery and easy to buy and simple to replace. Maplins or a good electrical wholesaler will supply.

There is a fuse that may have blown, and the charging ciruit may have failed but first thing is afte 10 years change the battery.

Type of battery and method to change will depend on the type of alarm.
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When you open the panel to change the battery. It is likely that it will contain a tamper switch that will set the alarm off immediately, even if the system is disarmed. (unless it's a key only operated panel where setting the key to test can prevent this)

You can quickly remove the old battery whilst the alarm is sounding as they have push on /pull off connectors. Close the panel and disarm the alarm in the usual way and the alarm will stop.

You can now take the original battery with you when you go looking for a replacement. The alarm will still work without it.

Keypad operated systems have the facility to enter an engineers code to allow the panel cover to be opened without this happening. However this code is set by the installer and it is unlikely it was left for the user.

There as also likely to be a smaller battery in the bell box outside the house. As you say the alarm goes off when power is restored, this suggests that this outside battery too has failed, as it should make the alarm sound when there is a failure of the mains supply and the battery in the panel. This is there incase a burglar gets to the panel turns of the electricity and removes the back up battery, or cuts the wires to the bell. This battery is not so crucial though except for the reason stated above.
Only ADT install ADT alarms - we have one!

If you can see which is the 24 hour circuit putting a link across the two connections will allow you to stop the tamper circuit operating the alarm. Should be marked on the board, then take the link out as the last job before you close the box up.
IJWS15 said:
Only ADT install ADT alarms - we have one!

If you can see which is the 24 hour circuit putting a link across the two connections will allow you to stop the tamper circuit operating the alarm. Should be marked on the board, then take the link out as the last job before you close the box up.

Guess again.

ADT also operate dealership. XYZ alarm company find the customer, xyz alarm company install it ADT look after it.

as for your comments, waste of time, just turn it off, either by key or code
Get some ear defenders....

With mine...
Find the tamper circuit loop in the main panel and as said previously... short it out with a short length of wire..... but, my main panel has a tamper button too! So its ear defenders on and go for it! Short it out and reset.

Batteres are easlly sourced from maplins or cheaper on the net.

Google the make and model of the alarm and you should be able to find the battery size / model you require.

Change mine every 6 years as per manual and its never been a prob ... so far!. 10 years means its due if not overdue replacement. Check the battery voltage before disconnecting it. It should be 13 ish with the charger on and working ok.
beefster - what makes you think that after more than 4 years the OP has still done nothing about the problem, and is still waiting for advice on what to do?

Good point..... was surfing for info on another Alarm issue and saw the post... didnt check the date.

Would say tho, I use the site as a search engine to look up issues people have posted that mirror mine rather than post new ones and get the same answer. Have i dug myself out of the hole.... :oops: ;)

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