What Happens When an Alarm System Battery Dies? - SafesRight

What Happens When an Alarm System Battery Dies?

House alarm systems are important for your safety, comfort, and peace of mind in your home, as they provide extra protection from people who might want to break into your home. However, like any other battery, the battery of your home alarm system will inevitably run out at some point. What happens in this case?

When an alarm system battery dies, it may still work if your house has power. However, if there is a power outage and the battery is dead, your alarm system will not go off in case of a break-in. The alarm system will notify you if a battery is running low or dying so that you can replace it. 

In the rest of this article, I will answer any additional questions you might have about house alarm system batteries and what you need to do if they run out. Additionally, I will explain how long batteries of different alarm system components last.

How Long Does a Battery Last in a House Alarm? 

There’s not one single answer to this question. Different house alarm systems work in different ways and are made of several components, so I will explain how the most common alarm systems work to find all the possible answers.

Alarm systems can be wired or wireless, but in any case, they will include some sort of connection to electricity supply lines and batteries simultaneously. Most alarm systems are connected to the main power line and have backup batteries in case of power outages. Some components like sounders or motion detectors can only use batteries because they are placed in locations where it’s hard to access AC.

Here’s how long batteries last in the typical components of an alarm system:

  • The control unit is usually hardwired but has a rechargeable backup battery that may last anywhere from three to five years.
  • The wired system external sounder uses a backup that lasts for a long time, even beyond a decade. 
  • The external sounder battery in a wireless system lasts about one or two years, depending on how often it’s triggered.
  • Motion detectors only work with batteries, which may last three to five years.
  • Security cameras may be hardwired with backup batteries or completely wireless; their batteries can last from a month to a year.

Can the Alarm Go Off if the Battery Has Died?

As I explained above, a typical alarm system uses batteries in different ways, so whether the alarm will go off or not depends on what batteries are out. Additionally, it depends on whether there is a power outage in your house or not. Let’s see all the parts that use batteries and if they can work without one.

Control Unit Backup Battery 

The control unit usually uses electric current from the grid and has a backup rechargeable battery. As long as you’ve got electric current in your grid, you’re good without a battery. If the power goes out and the battery works, it will provide protection with no problem for 24 to 48 hours. However, if the power goes out and the battery is dead, your control unit cannot work.

Security Cameras Battery

Some security cameras are hardwired and use backup batteries. For these particular cameras, the situation is similar to the one of the control units that I explained above. For cameras that only use batteries, the problem is different. They will work even if there’s no power, but if the battery is dead, they won’t be able to capture anything, even if there’s power in your house.

External Sounder Battery and Motion Detector Batteries

Wired external sounders can work using AC, so as long as you’ve got power, they will be triggered as planned if their connection to the control unit is interrupted. If there’s no power, the battery will provide electricity to work, but if the battery is dead, the sounder will not be able to alert anyone.

A wireless external sounder will work if there’s a power outage since it relies entirely on batteries. However, if the batteries are dead, it will be useless. The same goes for wireless motion detectors as well.

As you can see, no matter how they receive electricity, alarm system components can’t work if their batteries are dead and there’s a power outage.

How To Tell if the Battery of Your Alarm System Is Dying

To make sure that your home alarm system will be running in every possible scenario, you need to ensure that you replace or recharge the battery before it dies. Not knowing if the battery of the control unit of your alarm system is dead can be dangerous. 

Thankfully, manufacturers have thought about this issue and have ways of letting you know. Every alarm system is different, but generally, you’ll receive a notification on the display of the control unit saying the battery of a particular component is low. The notification might also come in the form of repeated sounds or flashes of light.

For instance, you may hear repeated beeps whenever you deactivate your alarm. However, you should consult the alarm system manual to make sure you know exactly what the sounds or flashes of light mean. Even after changing the batteries, you may still get signals which may indicate other problems.

What To Do if the Alarm System Battery Dies

Ideally, you would read the warning and change the battery before it dies so that you don’t leave your house vulnerable, even for a short amount of time. 

Depending on the system and the particular component, you can change the battery of your home alarm in different ways. If you can, contact professionals to help you so that you know the alarm system will go back to work as soon and smoothly as possible.

Alternatively, you can try to change the battery by yourself. To do so, follow the specific instructions on the manual of your alarm system to make sure the battery replacement is done safely and correctly.


Your alarm system is an excellent way to ensure you’re protected in your home, but it can let you down when you need it most if the battery is dead. Most house alarm systems include a combination of wired electricity and batteries to make sure you are protected even in extraordinary circumstances.

However, if the battery is dead and there is a power outage, your alarm system won’t work in any way. Luckily, your control panel will alert you continuously when the batteries are running low so that you can replace them as soon as possible.

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