How to Wire a Second Battery for Car Audio: Everything You Need to Know!

Listening to music on a long drive brings rhythm to each moment of driving. And, driving a car without listening to music seems impossible for those who are music lovers like me. Approximately 88% of people love listening to music during long drives. But, making your trip more pleasant with music requires a second battery to support the power of your car audio system. 

Because the car battery might face certain issues like fast battery charge draining when you want to use your car audio for hours or some other accessories on a constant basis. And, this is where you’ve to think about a second battery for your car stereo system. So, knowing how to wire a second battery for car audio is a must-do if you want constant music for your entire trip.

No worries if you’re not familiar with the process of wiring a second battery to your car. Because in this article, we will discuss just how you can do it all by yourself.

So stay tuned!

Table of Contents

Why Do You Need a Second Battery for Car Audio

You need to add an extra battery for several reasons, for instance, higher cranking amps. A higher cranking amp is required if you want a fast start. Here are a few more reasons why you need a second battery for car audio.

  • Longer Car Stereo Runtime

Using a second battery will allow the car battery to reserve more power which ensures a longer car stereo runtime.  However, if you want your car stereo to perform high-quality sound you can add a  subwoofer box to the car audio system.

  • Better Sound Quality

Having a second battery for your upgraded car audio system will ensure a quality sound at higher volumes. As a result, you can listen to music at whatever volume level you want.  

Besides, a secondary battery will allow you to enjoy music for an entire trip without any interruption. And, it will increase the amplifier’s life span

  • Less Strain on the Vehicle’s Electrical System

The higher the battery power, the less the vehicle’s electrical system’s damaged. A second battery can save the car’s electrical system from any subsequent system damage or overload.

  • Extra Reserve Power

The remaining battery of your car isn’t covering the standard amount of power if you see the headlights are dimming. In this case, you must add a second battery for extra reserve power.

If you install your second battery faultlessly, it will function accurately and optimize the engine’s reserve power.  So, you can easily overcome the hassle of the battery’s power running out.

2 Types of Car Batteries to Choose From

You’ll get two different types of car batteries available depending on power, performance, and cost. One is a Lead-Acid car battery and another is a Lithium-Ion car battery. Let’s know about them in brief:

1. Lead-Acid Car Batteries

The lead-acid battery comes in handy when you need high power density.  It is well capable to deliver the maximum amount of power in a short while. The lead-acid battery has many types:

  • AGM Lead-Acid Batteries
  • Gel Lead-Acid Batteries
  • Wet Flooded Lead-Acid Batteries

And, all its types will deliver specific advantages for your car, for example- 

  • The AGM battery is vibration resistant in terms of its sandwich construction.
  • The wet flooded battery will get you a quick recovery from deep discharge. 

2. Lithium-Ion Car Batteries

The fundamental exertions of the lithium-ion battery began in the 1980s and it was launched on the market commercially in 1991. You’re welcome to decide on the lithium-ion car battery if your car is a high-performance vehicle. 

The battery management system of the Lithium-ion battery is ready to save your battery from overcharge or under-charge risk. But, it’s a gentle reminder for you to charge the battery properly, or else it will fail in delivering proper service.

5 Factors to Consider before Wiring a Secondary Battery for Car Audio

You must go through some of the most significant and crucial factors before you wire a secondary battery for your car audio. Also, you should know about the cost and installation timing. Because not all the battery takes the same amount of time and costs to install.  

Here are five essential factors to consider that will save your vehicle from unwanted damage.

  1. You must research the battery precautions before deciding on a secondary battery. If you research all the possible precautions about the battery, it will help you prevent accidents.
  2. The main function of the battery is its sustaining capacity. So, check out the battery capacity before you start wiring.
  3. Using a battery isolator to fix the second battery is one of the safest ways. A battery isolator will easily allow your vehicle to ignite with stable power. 
  4. The battery never can distribute the power equally unless you connect it in a parallel way. The parallel connection will get you an equal power distribution trouble-free. Besides, it will hold the additional power of the battery as backup. 
  5. The installation timing can vary from 20 minutes to 120 minutes. So, reserve enough time before starting this second battery wiring job.

How to Wire A Second Battery for Car Audio

Wiring a second battery for the audio car isn’t that difficult if you can go in the right direction. So, following the 6 recommended steps below, you can easily wire a secondary battery for car audio. Let’s see how.

Step 1: Determine the Type of Battery You’ll Need

The fundamental step to wiring a second battery for car audio is to determine the right type of battery. But, how can you recognize the right type of battery for your car audio? 

Well, find out the several cranking amps of your battery with its outright watts. For example, if your car stereo system goes through 2200 watts, it means the battery is fairly sizable. So, it can supplement your extra wattage requirements. 

At this point, we recommend you choose the Lithium ION battery for your car audio system. Because the Lithium-ION battery can deliver more assistance than Lead Acid battery, for instance, stable output voltage. 

Step 2: Acquire the Necessary Tools for Installation

No installation can be done unless you have accurate tools. Here’s a list of all the necessary tools that you must have before you start installing the secondary battery in your car:

  • Drill Bit
  • Wrench
  • Battery Isolator

Having these tools ready will take your job a step ahead of your installation task. 

Step 3: Connect the Primary and Secondary Batteries

You require a battery isolator to connect the primary and secondary batteries. The battery isolator will help you disconnect each of their circuits. 

Now, connect the battery to the front side beside the vehicle engine rather than on the backside. Because connecting the primary battery to the back side will require you an extra partition to keep the primary and secondary battery separate. 

Now, use a wrench to connect the battery to the positive nodes of the car alternator and take a parallel connection to the secondary battery from the primary battery. And, also you’ve to position the negative nodes. 

Step 4: Connect the Secondary Battery with the Car Amplifier

Once you’re done connecting the primary and secondary battery, you need to close the positive sides end with a cover or cap. Closing the positive ends with a cap is a safety precaution. After completing all the above steps, you have to connect the second battery with the car amplifier. 

To get the connection perfectly between the second battery and the car amplifier, connect a 4-gauge red wire to the secondary battery’s positive end and route the wire to a fuse. 

Step 5: Ground the Negative Sides of Both the Batteries

You’ve connected the secondary battery with the car amplifier means it’s now the perfect time to ground the negative sides of both the primary and secondary battery. Remember, grounding the negative sides of the batteries is crucial.

Step 6: Check all Connections

Whether or not, all the connections are done accurately, it’s a good idea to double-check because a wrong connection will lead your car to stop starting the engine. We recommend you tighten all the connections one more time using a wrench. It will prevent the battery from moving while driving your car.

So, tune your car stereo and get the high-quality sound with ease.


Once you decide for making your trip more enjoyable with upbeat music, you’ve no option but to decide on an auxiliary battery. 

So, recognizing how to wire a second battery and wire it perfectly is indispensable to the betterment of your car audio system. Thanks for Reading!


1. Can One Alternator Run Two Car Batteries?

Well, an alternator is highly capable to run two batteries at a time. But, you must be careful while connecting the batteries.

2. Is an Isolator Necessary For a Second Car Battery?

Yes, the isolator is necessary for a second car battery.

3. When to Add a Second Battery to a Car?

If you intend to use the car stereo for an extended time and also want to use accessories when the car engine isn’t running, you should add a second battery.

  1. How Much Power Does a Car Battery Hold?

Usually, a car battery can hold approximately 12.6 volts which stands at 1,323 watts/hour.

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