How To Install A Second Battery For Car Audio

by Matthew David | Updated: 09/14/2023

How To Install A Second Battery For Car Audio

Have you ever wanted to really crank up the volume in your car, but found the music starts distorting or the lights dim whenever the bass hits? It’s frustrating when you can’t enjoy your expensive sound system to its full potential.

The problem is your stock electrical system and battery simply can’t provide enough steady power for today’s high-powered amps and subwoofers. But don’t worry, you can fix this by installing a second battery dedicated to your car audio system.

In this guide, I’ll walk you through everything you need to know to safely add that second battery. With some simple tools and basic mechanical skills, you’ll have your system pounding out the jams at full volume in no time. Let’s get started!

Why Add A Second Battery?

Before we jump into the installation, you might be wondering why add a second battery in the first place?

Well, there are several excellent reasons:

So in short – more power, longer playtime, prevent electrical gremlins, and improved sound. That’s what a second battery brings to the table!

Choosing The Right Second Battery

When selecting a secondary battery, there are several important factors to consider:

Battery Type

You’ll want the second battery to be the same type as your current battery. For most modern vehicles, that’s a lead-acid battery. Using the same battery chemistry avoids compatibility issues.


Look for a battery with greater reserve capacity and cranking amps than your stock unit. More capacity means more power for your system. Aim for at least 20-30% higher ratings.

Physical Size

Make sure the battery will physically fit the space you have available. Measure twice to ensure it fits before purchasing.

Brand and Age

For best performance, use two new matching batteries from the same manufacturer, ideally purchased at the same time. This prevents an imbalance.


Avoid using an old weak battery for your secondary. Check that it can still hold a proper charge and voltage first.


Install the battery close to your amps to minimize power loss over the wiring distance. The trunk is ideal.

Follow this criteria, and you’ll have a top-notch second battery ready to install!

How To Wire The Batteries

Once you’ve got your new battery, how do you wire it up? You’ve got two options:

Series Wiring

In a series connection, the batteries connect end-to-end, with the positive from one to the negative of the next. This provides additive voltage but identical capacity. Rarely ideal for audio applications.

Parallel Wiring

For car audio, you’ll usually want to wire your batteries in parallel. This means connecting the positive terminals to each other, and likewise with the negative terminals.

Parallel wiring combines the capacities of each battery for more total power. It also evens out the workload so one battery doesn’t get over-stressed. Just what you need for your amps!

Step-By-Step Installation Guide

You’ve got your new high-capacity battery and know how to wire it. Now let’s get into the nitty gritty of the install process! I’ll cover this in six key steps:

Step 1 – Select The Install Location

Find a good spot to mount your second battery. The trunk or rear cargo area usually works well. If installing up front, use a sealed battery box for safety.

Step 2 – Disconnect The Existing Battery

Always disconnect your current battery first! This prevents dangerous sparks during installation.

Step 3 – Mount The Second Battery

Securely mount the second battery in place using the appropriate tray or hold-down. Ensure it won’t shake loose.

Step 4 – Connect The Positive Cables

Run a cable from the + terminal on each battery and connect them. Add an ANL fuse within 18″ of the batteries.

Step 5 – Connect The Negative Cables

Likewise, connect the two negative terminals to each other. No fuse is needed for the ground connection.

Step 6 – Connect The Ground Cables

Finally, attach a ground cable from each battery to a metal chassis grounding point.

Once wired, keep the batteries close together so the cables aren’t stretched. Now you can connect your amps to the new battery and get rockin’!

Additional Tips

To squeeze every last bit of power from your new dual-battery setup, keep these bonus tips in mind:

Troubleshooting Problems

Despite best efforts, problems can occasionally crop up when running dual batteries. Here are some common issues and potential solutions:

Most dual battery problems can be prevented by proper installation and maintenance. But if issues arise, systematically check each part of the system to isolate the culprit.

Closing Thoughts

Adding a second battery is one of the best ways to get the absolute most out of your car audio system. The extra capacity prevents strain on your car’s electrical system while providing consistent, noise-free power.

While the installation requires some effort, the work is absolutely worth it. With a robust dual-battery setup powering your amplifiers, you’ll finally be able to crank up the volume and feel that bass without distortion or dimming lights.

So don’t settle for lackluster performance from your expensive audio gear. Follow this guide and install that second battery for the ultimate listening experience!