Does a Car Alarm Drain the Battery? (Complete Guide)

These days, every car comes equipped with a car alarm, which helps to ensure that your car isn’t stolen, though it’s effectiveness does vary in this day and age.

Of course, your car alarm runs on battery. However, does it actually drain your batteries if left on? If you’d like to find out, keep reading!

Does a Car Alarm Drain the Battery?

When installed correctly, car alarms draw such a small amount of power that it would take a very long time for them to drain your car’s battery. However, incorrectly uninstalled batteries and aftermarket batteries may have far more power and therefore drain your battery in some situations.

For all the information you need about your car alarm and the battery, keep reading below for more useful facts and tips!

What Can Drain a Car Battery When the Car is Off? 

There are several things that can drain a car’s battery when the car is off. Technically, anything that can remain on by itself for an extended period and uses electricity can drain your car’s battery.

Some of these are quite apparent, such as your interior lights or door lights. If a door isn’t closed all the way or the lights are set to the on position, they can quickly drain your battery.

Furthermore, your headlights can also quickly drain the battery if you leave them on accidentally. If your car’s battery only died once, it is likely that you accidentally left a light on.

Loose battery connections can also cause the battery to drain, even if anything isn’t actually on. If the terminals become corroded, then your battery will have a hard time transmitting charge and charging back up.

While the battery may not actually die in this instance, it won’t transmit the energy that it has correctly, rendering it useless.

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Furthermore, extreme temperatures can cause a drain on the battery. If it’s very hot or cold in your area, your battery may die completely or weaken (older batteries tend to have these problems more often).

In some cases, the alternator may be to blame. If your battery isn’t charging while you’re driving, then the battery may die sometime later.

Another tricky thing that can drain the battery is broken taillights. Generally, your car’s tail lights turn on when the brake hits a small button underneath it. If this button malfunctions, your brake lights could be on all the time. Therefore, your battery could die more often.

How Long Can a Car Alarm Sound Before the Battery Dies?

For the most part, each type of car alarm has its own battery. Some have larger batteries than others, which means that they will last longer.

With that said, most of their batteries last a very long time before they die. For instance, some car alarms could theoretically sound for weeks before shutting off.

Of course, there is no telling how your specific alarm will last unless you look up the manufacturer guidelines or test it out. While the former is quite easy to do, it’s not recommended that you test it out, as the sound could disturb your neighbors.

Is the Car Alarm Connected to the Battery?

Is the Car Alarm Connected to the Battery?

In many cases, the car alarm is hooked directly up to the battery. If the battery dies or is disabled, then the car alarm will not sound.

However, this has become an easy way for thieves to disable the car alarm. Therefore, companies have started coming up with ways to get around this.

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For instance, some car alarms have their own battery that is hidden and hard to get to. Therefore, even if your car’s battery is disabled, the alarm will continue to sound. For the most part, it depends on how your car’s alarm is set up.

Will Disconnecting a Car Battery Stop the Alarm? 

Once upon a time, this would have worked to stop the car battery. However, in today’s world, companies have figured out that thieves commonly disconnect the battery to stop the alarm.

As you might imagine, it completely defeats the purpose of an alarm if it can be disabled that easily. Therefore, the companies sought to fix that problem.

Usually, these companies did this by giving the aftermarket alarm its own small battery. The car alarm will draw from the normal car battery when it’s available. However, even if it becomes disconnected, then the alarm will still sound by drawing from its personal battery.

Of course, if you disconnect this personal battery, the alarm will stop. However, these batteries are purposefully put in hard-to-reach places and hidden from view.

For the most part, you just have to know where they’re located, which would take knowing that model of vehicle like the back of your hand. As well, you’d have to actually locate the battery, which can be easier said than done.

With this in mind, car alarms are much harder to disconnect today. After decades of car theft, car security companies have figured out how to get around the most common tactics.

How Do I Permanently Turn off My Car Alarm?

How Do I Permanently Turn off My Car Alarm? 

Today, most cars come with car alarms, despite the fact that they are horribly ineffective. When they first came out, car alarms might have been affected. However, as time went on, people became desensitized to the alarm.

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For the most part, most people are not going to rush towards a car alarm today, thinking that something is being stolen. Instead, they’re more likely to think that it’s a false alarm.

Understandably, many car alarms today are more annoying than they are helpful. Therefore, you may consider disarming it all together, which can be done by disconnecting the car alarm from the rest of the car or simply removing it completely.

With that said, most car alarms are not designed to be removed. Therefore, they can be hard to get to and difficult to find, and are difficult to remove overall. Instead, you’ll likely want to get a professional to do it.

Keep in mind, your insurance company may not want you to remove the car alarm, because if it becomes apparent that it was disabled, it may null and void your plan. However, it does depend on your policy.

As well, if the car is wrecked (and not stolen), then the odds of the security system being checked may be quite low.

To know more about car alarms, you can also check our posts on whether or not car alarms deter thieves, what triggers a car alarm, and how to disconnect a car alarm fuse.


Usually, you don’t have to worry about your car alarm draining your batteries. However, there are some cases where this might occur, such as with an incorrectly installed battery.

Furthermore, car alarms usually aren’t made to only draw from your car’s primary battery. Instead, they often have a backup battery to prevent them from being disconnected. Therefore, disconnecting the battery won’t necessarily turn off the battery.

1 thought on “Does a Car Alarm Drain the Battery? (Complete Guide)”

  1. Walter Mercedes Benz, Riverside, CA is stating that the sirene alarm in my wife’s Mercedes Benz C 240 is draining power off the battery and that’s why I have to give it a charge each morning to get it started It’s a 2004 car which
    is parked in front of the house and is only moved when it’s street sweeper week or to get gas due to me starting up the engine for about 30 minutes to charge up the battery. This was ok for the past years but within the past month I’ve started charging each time I had to start the car, so now its been in the shop for two weeks trying to find the problem and they came up with the sirene alarm is draining the power, I’m really questioning if that’s the cause. I’m going to tell them to disconnect the alarm from the battery (which is about a year or two old) and put a new battery in, any comments on my thinking????
    Thank you
    Frank Gallegos


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