I turned off a breaker for about an hour. I then heard a low beeping noise, not the full-blown alarm siren. I turned the breaker back on, but the beeping persisted.

We called the alarm company. They told us the police were never notified and that we can just reset the system by holding a key down on the number pad for 3 seconds.

The beeping started up again last night and again this morning. Each time we have been pressing the reset button to stop it. I was wondering if the security system might have a backup battery, and, if so, if the system is saying the battery needs to be replaced?

4 Answers 4


Most alarm systems have a backup battery.

It would appear likely that yours is indicating failure and need of replacement. I would expect a competent alarm monitoring service to advise you of that (or any other reason for a recurring trouble code), so you may want to shop around for a different service.

  • 20
    Although it feels like a coincidence, turning off the breaker allowed the system to drain what little power left in the backup, and when the power is turned back on, the battery can no longer charge.
    – Nelson
    Commented Mar 21, 2022 at 2:39
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    @Nelson Or, in that same vein, forced the panel to use the battery which triggered a test of the battery that failed.
    – Machavity
    Commented Mar 21, 2022 at 12:41
  • 3
    Key question: how old is the backup battery? Commented Mar 22, 2022 at 5:55

This is typical. The alarm system is normally powered by your home AC power. It may be hardwired, though typically for small alarms use a plug in adapter with low voltage wires routed through the wall to the main alarm unit. There is also a battery backup, possibly rechargeable, but even rechargeable batteries can wear out.

When you turned off the power, the battery discharged enough to indicate the need for replacement. When you turned power back on, that allowed the alarm to work again but did not remove the low/replacement battery condition.

Battery replacement is usually pretty easy - a few screws and then two wires. The batteries can vary from a traditional 6V "lantern battery" to a modern rechargeable battery pack. While the alarm company should be able to tell you exactly what type of battery you have/need, often the easiest way to figure it out is to simply find the battery, remove it and take it to a battery store, or order a replacement online based on the battery specifications.

Many alarm companies will notify you automatically in case of a low battery situation. This is important because if the low battery happens while you are away you may not realize that there is a problem until the battery goes dead and the alarm no longer works. They may also have tried to notify you on an old number - e.g., many people no longer answer their landline except for friends/family - so periodic updating of the alarm company notification information is worthwhile too.

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    Another common battery is a small 12V lead-acid (similar to the ones used in UPSs). They have an expected lifetime of about 10 years
    – Chris H
    Commented Mar 21, 2022 at 10:31
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    @ChrisH I'd say 3-5 years for most general lead-acid batteries. I've replaced dozens of UPS batteries over the years and by five years they hold about as much charge as dog meat.
    – J...
    Commented Mar 21, 2022 at 19:06
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    @J... burglar alarms are less demanding than UPSs, but I've replaced my battery a couple of times in 15 years and it's probably about due again. The stupid house builders put it in the airing cupboard next to the hot water tank and they don;t like getting hot (also an issue in small UPSs, squeezed next to power conversion electronics - I've replaced the batteries in those too)
    – Chris H
    Commented Mar 21, 2022 at 20:50
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    @manassehkatz-Moving2Codidact many of the US telecoms companies do seem to be particularly awful. Although ours aren't great, we haven't yet had to deal with the removal of copper-wired phone lines - I've got fibre to the cabinet in the street and the power to that isn't my problem
    – Chris H
    Commented Mar 21, 2022 at 21:18
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    "his is important because if the low battery happens while you are away ... many people no longer answer their landline" and if you're away, then calling you on the landline isn't going to work very well if the landline is to the house that you are away from. Commented Mar 21, 2022 at 22:43

You need to find your user's manual for your alarm system, and see what it has to say. If you don't have one, then talk to your alarm company.

Yes, it's likely it's complaining about the battery. They need to be replaced every 3 to 5 years. The alarm can sense if it's not getting up to full charge anymore.

Another thing that alarms can complain about are smoke detectors. They will test and check your smoke detectors on the order of once a day. If that detects a failure, they will complain about that. Your user manual should tell you what the different indicators are.


It's worth also mentioning that the siren may also have its own backup battery, so if the problem persists after swapping the backup, this might be the solution.

  • @PeterMortensen Thank you - corrected. You'll have to take my word for it that I normally get that right!
    – Lefty
    Commented Mar 21, 2022 at 11:54
  • There, their, they're, @PeterMortensen, you're not the only one who bristles at that!
    – FreeMan
    Commented Mar 21, 2022 at 12:23

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