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How to Fix a Car Stereo Draining Battery: Causes & Solutions

Writen by Edwin Jones

Fact checked by Andrew Wright

how to fix a car stereo draining battery

The car stereo is an essential part of any modern car. However, it can consume a large amount of power from the battery. As a result, it can even harm your vehicle’s power supply. If this problem persists, you might be stuck somewhere with a dead battery.

Fortunately, you can learn how to fix a car stereo draining battery yourself. In the following parts, we will suggest some common causes and fixes, which are: replacing the radio, connecting it to switched fuses, and upgrading the battery.

Can a Car Radio Drain Your Battery?


Many devices can cause a “parasitic draw” on your car’s battery. Your stereo is one of the most common devices that can do this.

Your stereo can slowly drain the battery. Unfortunately, you may not realize how much it drains your battery. Your battery may be unusable if this condition persists.

Sometimes, battery drain can happen very quickly.

Some signs that the battery is draining quickly:

  • It is difficult to start the car even if you have just changed the battery
  • When you turn off the engine, some devices still work
  • The engine cranks a lot when starting the car
  • Dashboard battery light is enabled consistently
  • And more

3 Main Cause and Steps to Fix a Car Stereo Draining Battery


1. The Cause Lies in the Stereo Itself

If the process of draining your battery suddenly occurs, even though you installed the car stereo long ago, the stereo could be the cause.

In this situation, you need to focus on the stereo system. Before going to the solution, you need to understand how the stereo system works.

Your stereo relies on a complex series of relays that are transmitted in their internal circuit boards. The circuit board is an essential part of a stereo system.

Over time, the stereo system will age. Some relay pathways may wear out and stop working. As a result, the stereo system may not go to sleep when necessary. That means the stereo system can waste energy, which is what drains your battery.

Even if the stereo system is in top condition, it can still malfunction in some way that you can hardly detect during use.


Unfortunately, if one of the relays fails, you should replace your old stereo with a new one. You can repair damaged relays, but the process is complicated, and it can take you plenty of time and effort.

In particular, pinpointing a faulty relay can be very difficult. Sometimes that is not possible. Even if you find it, you will have a hard time fixing it.

In general, in this situation, it is best to replace your stereo. That is the simplest way to solve the problem. Then, you just need to make sure that the installation process is correct.

2. The Cause Lies in the Wiring System

In this situation, the stereo system you recently installed on your vehicle may cause the battery to drain.

If you set up the wiring system yourself, chances are you did it wrong at some stage. Incorrect wiring setup can cause the stereo to drain the battery quickly.

Any new stereo will come with installation instructions. Users need to install the car stereo system precisely according to the instructions to avoid draining the battery. Unfortunately, sometimes the instructions are not transparent or complete, which causes users to make mistakes.

Every car comes with a fuse box. In most cases, it includes fuse ports. Some fuse ports are constant, while the rest are switched. Specifically, switched fuses are only powered when the car is running. The constant fuse consumes power even when the car is off.

Hence, connecting the car stereo to constant fuses can cause the radio draining car battery when off. You need to keep in mind that you have to connect the car stereo to switch fuses.


The way the fuse box is installed is different for each model of vehicle. Thus, to distinguish between switched fuses and constant fuses, you need to check manually.

You need to get a voltage and continuity tester. Fortunately, these tools are affordable, and you can easily find them at any electronics store.

Once you have the right tools, you need to stick to the following steps:

  • Step 1: Turn off the car engine and locate the fuse box.
  • Step 2: On the vehicle, identify the unpainted metal surface. Then ground your tester to that point. You should remember that this step is essential.
  • Step 3: Use your device to probe the fuses.
  • Step 4: The constant fuses will light up your device while the car is shut down. You must not connect your car stereo to them.

Switched fuses are fuses that do not light when you do this process. You need to connect your stereo to any of these fuses.

3. Your Battery Is Not Compatible With Your Stereo

The final reason why a car stereo drains the battery is that your battery isn’t powerful enough to handle the stereo system. In other words, your stereo may require more amperage than the battery can supply.

Maybe you will face this situation when you install an aftermarket stereo in your vehicle. Then the stereo system can demand excessive power from the alternator. As a result, the alternator may have difficulty recharging the battery while your car is running. People often use the term “outrunning” to refer to this problem.


In this situation, it is best to use a large battery or add an extra battery.

  • Use a large battery

Replacing an old battery with a larger one can be very complicated. Sometimes that is impossible because the car’s battery may not fit your car’s tray. In addition, you may need to do many things to finish the installation.

However, if the process of inserting a larger battery into the car’s tray goes smoothly, you should use this method.

  • Add an extra battery

If the stereo system requires a more robust power source, it is best to add an extra battery.

You can use the extra battery continuously while the car has not been started. You should install additional batteries in vehicles that have heavy electrical parts.

By applying this method, you can power up the stereo. As a result, the stereo system will get the needed power while your main battery stays untouched.

If you choose this way, you need to make sure the extra battery and the old battery are connected in parallel.

It’s wise to purchase a new pair of batteries for the best performance. Although buying a new pair of batteries is not required, it can make a difference. Connecting an additional battery to the old one is not the optimal solution.

If you are inexperienced, it is best to take your car to a car audio center and get help.

Frequently Asked Questions


Why is an aftermarket stereo draining battery?

Battery drain will occur when your battery isn’t powerful enough to handle your aftermarket stereo. Hence, you need to buy an aftermarket stereo that matches your current battery. If your battery is old, consider replacing it with a larger battery.

What if the battery drain persists?

If this condition persists, your vehicle will not operate at its best performance. One day, you might be stuck somewhere with a dead battery.

Can the stereo drain battery while the car is running?

The short answer is no.

When your car is running, the stereo uses power from the alternator. Therefore, it cannot drain the car battery.

Can a lousy radio fuse adversely affect the battery?

No. The fuse cannot directly cause battery drain.

Can a lousy ground cause battery drain?

The short answer is no.

Why does my new battery keep draining?

The most common reason is that the stereo system is too powerful for your car battery. In addition, a short circuit also leads to battery drain even though you may have just replaced the battery.

How often should I change my car battery?

It would be best if you replaced your car’s battery every 2-3 years to keep it working at its best. As a result, your car can avoid many breakdowns.

Can a dead battery be recharged?

A vehicle’s alternator is designed to keep a healthy car battery in good working order. However, it can never recharge a dead battery.

Is it hard to replace a car stereo?

This job requires you to have in-depth electrical knowledge. Thus, if you are inexperienced, it is best to seek the help of professionals.

Final Verdict

In general, there could be a lot of factors that result in car radio draining battery. We covered the most common causes and solutions in this article. We will be glad if they are helpful to you.

Hopefully, you had a good read. Feel free to share your tips on how to fix a car stereo draining battery as well. See you in other posts!

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