How to install a second battery for car audio

How to install a second battery for car audio

If you are a music lover and think of having a dope car audio system, you might consider installing a second battery for car audio. A high-performance car audio system requires more battery power. Especially when the car engine is turned off, it could be a mess.

Even a high output alternator is no good if the engine is not running. The only solution is adding an extra car battery for car audio. 

Nowadays a car is an essential thing in our daily life. In our busy lives, we love to travel with our friends and family by car when we get the opportunity. It could be boring when we drive over 6 hours in a dumb car without satisfying car audio.

Who needs a second car battery 

When you want some louder music in your car, then you should go for the second battery. The second battery comes in handy while playing music for more extended periods. The default car battery cannot give sufficient power in some circumstances.

Music lovers who listen to music while the car engine is off quickly experience that the factory battery does not last long. At the same time, an additional battery can handle the requirements of extra power.

A high-end car audio system can be a cause for the death of car batteries. If you have a high-performance audio system and like listening to music even when the car engine is off, you need an additional battery. 

The battery on cars is used to serve car purposes, so factory batteries can not be used for all purposes. If we use a single battery for all purposes, then the charge or ampere of the battery will spend more than normal, affecting the battery life. 

Many people also use car electric systems to charge mobile phones, laptops, etc. They also cost a lot of ampere of factory battery which a single battery can not support. It is pretty impossible to use a single battery for multi-purpose work. For those who love louder music in their car, having a second battery is essential.

Why you need matched batteries?

When it comes to upgrading your car audio system and adding a second battery, it’s important to understand the significance of using matched batteries. While it might be tempting to mix and match different batteries, doing so can lead to various complications and potentially hamper the performance of your audio setup. 


Balanced Performance

Using matched batteries ensures that both the primary and secondary batteries have similar performance characteristics. Batteries from the same manufacturer and model are designed to deliver consistent power output, charge acceptance, and discharge capabilities. This balance ensures that your audio system receives the required power without straining either battery excessively.


Equal Charging and Discharging

Matched batteries have similar internal resistance and voltage characteristics, which allows them to charge and discharge evenly. When batteries are mismatched, one battery may receive more charge or discharge faster than the other, leading to imbalances and potential damage. The charging and discharging process with matched batteries is more efficient and reliable.


Extended Battery Life

A second battery is often added to support the increased power demands of a car audio system. By using matched batteries, you can prolong the overall battery life. When batteries are mismatched, the weaker battery may be subject to additional stress as it tries to keep up with the stronger one, leading to premature failure. Matched batteries, on the other hand, distribute the workload evenly, reducing strain and promoting longevity.


Efficient Power Distribution

Matched batteries help maintain stable voltage levels within your car audio system. When batteries are mismatched, voltage fluctuations can occur, affecting the performance of your amplifiers and speakers. A balanced power distribution ensures that your audio equipment receives a consistent power supply, improving sound quality and system performance.


Easier Maintenance and Replacement

Using matched batteries simplifies maintenance and replacement procedures. If one battery fails or requires replacement, having a matched pair allows you to easily find an identical replacement without searching for a different battery with the same specifications. This convenience ensures that your audio system remains operational with minimal downtime.




How to install a second battery for car audio: 

Everyone loves high-end car audio systems along with multiple quality subwoofers, speakers and amplifiers. But most people don’t understand that these high-performance audio systems require a lot of power to run that can drain the battery charge in a short while. Using a second car battery can solve this issue.

You can install the second car battery simply following the steps below –   

Step 1: 

First, turn off the engine. Then open the hood and disconnect the car battery. Using a wrench, remove the negative terminal connection. 

Step 2: 

Place the additional battery in the car trunk (Most people prefer to install it in the car trunk). Installing the second battery around the car audio system makes wiring easier. If the amplifier is inducting in an area other than the trunk, you want to install the battery near the amplifier to make the wiring easier. 

Using a battery box and a drill, install the battery on the floor of the trunk. Tighten the bolts by using a wrench to hold the battery position. 

Step 3: 

Wire the second battery to the positive side. Use a heavy gauge copper wire with two gauges. You have to put a piece of wire from the positive side of the secondary battery to the power log of the nearest amplifier. 

Use a wire stripper, unfasten the cable protective plastic covering just enough to enable you to create an end to each end of the wire. Then connect one end to the positive terminal post on the battery and the other on the amplifier’s power lug and tighten the connection with a wrench.

Step 4:

It’s time to check all the wiring, make sure the positive and negative terminals are well attached. Now grab the tools and clean the trunk. Then close both the hood and trunk. 

You are done!

The pros of using an additional battery in your car audio system

When it comes to maximizing the performance of your car audio system, having a reliable and robust power supply is crucial. Incorporating an additional battery into your setup is a popular solution to ensure ample power. 


Increased Power Capacity

One of the significant benefits of adding an extra battery is the increased power capacity it provides. Car audio systems, particularly those with high-powered amplifiers and subwoofers, demand significant power. By introducing an additional battery, you effectively expand the available power reserve, ensuring that your audio system has a stable and sufficient power supply even during demanding soundscapes and bass-heavy tracks.


Improved Sound Quality

Insufficient power can result in distortion and reduced sound quality in your car audio system. Using an extra battery enhances the overall power delivery, minimizing voltage drops and providing cleaner, distortion-free power to your amplifiers. This leads to improved sound clarity, increased dynamic range, and enhanced audio detail, allowing you to appreciate your music’s nuances and impact fully.


Prevention of Battery Drain

High-powered audio systems can strain your vehicle’s primary battery, especially during extended periods of high-volume usage or when the engine is not running. Adding a separate battery dedicated to the audio system ensures that you can enjoy your music without the risk of draining the primary battery. This separation also helps maintain the primary battery’s charge, allowing for reliable vehicle starting and operation.


System Stability and Reliability

With a dedicated battery for your car audio system, you create a more stable and reliable power supply. The additional battery acts as a buffer, providing a consistent voltage level independent of fluctuations caused by other electrical components in the vehicle. This stability minimizes the chances of sudden audio system shutdowns or voltage-related issues, ensuring a consistent and uninterrupted listening experience.


Flexibility and Expandability

Installing an additional battery opens up opportunities for future expansions and upgrades to your car audio system. The increased power capacity allows for the integration of more powerful amplifiers, larger subwoofers, or additional components without straining the electrical system. This flexibility ensures your system can evolve and grow alongside your audio preferences, providing room for customization and improvement.


Extended Battery Life

Utilizing a dedicated battery for your audio system reduces the load on the primary battery, effectively extending its lifespan. The primary battery is primarily responsible for starting the vehicle. With the audio system drawing power from a separate battery, it experiences less strain and has a higher chance of maintaining its optimal performance for longer.


What are the problems with batteries in parallel?

While connecting batteries in parallel can have certain benefits, such as increased capacity and extended runtime, it’s important to be aware of the potential problems when using batteries in this configuration. Here are some common issues associated with batteries connected in parallel:

Batteries connected in parallel may have different levels of charge or voltage. When batteries with varying states of charge are connected, they equalize their charge levels. However, this can result in imbalances, with one battery discharging into the other until its voltages are balanced. These voltage imbalances can lead to inefficient power distribution and reduced overall performance.

Even if the batteries have the same voltage, they may have different capacities. Batteries with additional capabilities will not discharge and charge at the same rate, which can result in one battery reaching its full capacity before the other. This means that the system will not fully utilize the larger-capacity battery, reducing the overall power and runtime of the battery bank.

When batteries are connected in parallel, they can influence each other’s self-discharge rate. If one battery has a higher self-discharge rate than the others, it will discharge into the other batteries, leading to an overall increase in self-discharge. This can result in shorter shelf life and reduced performance when the batteries are not actively used or charged regularly.

If one battery in a parallel configuration becomes faulty or weak, it can negatively affect the performance of the entire battery bank. A weak or defective battery can experience higher internal resistance, which can cause it to discharge faster and reduce the overall capacity and runtime of the system.

When using batteries in parallel, it is important to ensure that each battery’s charging and discharging characteristics are well-matched. If one battery has a different charging or discharging profile, it can lead to imbalances in the system. Overcharging or over-discharging can damage the batteries and shorten their lifespan.


To mitigate these problems, it is crucial to:

  • Use batteries of the same type, age, and capacity.
  • Ensure the batteries are well-matched in terms of voltage and internal resistance.
  • Regularly monitor and balance the batteries to maintain voltage and capacity equality.
  • Employ a proper charging and monitoring system compatible with parallel battery configurations.
  • Consult battery manufacturers’ guidelines and recommendations for parallel connections.


Adding a second car battery is an objective worthy investment if you are a car audio enthusiast. The additional battery allows you to enjoy music at high volume for more extended periods without worrying about losing the charge of your default battery. It means you can have a fantastic road trip and enjoy your favourite playlist.

You can also read about How to tell if a subwoofer is blown? 

About Brenda Smith

Brenda Smith is an Audio consultant and part-time automotive content writer. She has an Audio engineering degree from a reputed university of Tampa, Florida. Being a great audio enthusiast, she works with her audio consultation startup and writing automotive content as a part-time writer.

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