What kind of alternator do I need for car audio?

Car audio fanatics always ask, “What kind of alternator do I need for car audio?” Car audio systems tend to pull large amounts of current from your car battery, especially if you don’t have the correct alternator. Your car’s alternator is an electric generator that works to produce alternating current.
Unfortunately for you, your vehicle cannot survive without an alternator. This is because it ensures your battery remains charged while your car is running and distributes electrical current to all the electrical components in your vehicle.

So, What Kind of Car Alternator Do I Need for a Car Audio?

Capacitors are materials with two conductors that are designed to store charge. However, installing a capacitor to solve your alternator problem is the wrong move. While it might help give your amplifier the boost it needs to cover the bass in your music, it will not help your headlight problem. As a matter of fact, adding a capacitor to compensate for your lacking electrical system will only increase the load your alternator has to carry. This would mean that your alternator has one more device that requires current to function.

So, suppose you are experiencing electrical problems such as headlight dimming when you install the speakers. In that case, it is probably time you upgraded your charging system to a High output alternator. Your current alternator might be having a hard time keeping up with the electrical demand of your amp.

What Is a High Output Alternator?


Your vehicle’s stock alternator will only provide enough current to meet basic electrical needs such as powering the headlights and sound systems. When upgrading your car’s sound system, you need to consider upgrading your alternator to meet the supply and demand of electrical current.

Investing in a high-output alternator may appear to be an expensive solution, but you’ll soon realize the benefits of modern radio in a classic car. High Output Alternators increase the amperage of your system. They also ensure the rest of your vehicle’s electrical components are working without restrictions.

Your alternator should produce about 120 % to 150 % of your total energy requirements. It is important to note that the rating provided on your alternator is the maximum amount of output it can offer and not the work it provides on a daily basis. When running your car on an incompetent alternator, your battery will have to jump in and give the remaining current needed for those components to work.

This requires energy which compromises the integrity of your battery and, therefore, your electrical components. For efficiency purposes, your alternator should only work to produce 35 % to 50 % of the stated output. This means it will put less strain on your engine in terms of fuel consumption. It will also increase the lifespan of your alternator and battery.

Your second option would be to minimize the volume of your sound system because loud sounds require more current. However, if you prefer your music on high volumes, High Output Alternators provide the current you’ll need for LOUD car audio.

How to Choose a High Output Alternator


Once you have already ascertained that the problem is in your electrical charging unit, then it is probably time you thought of a High-output alternator. The general rule of thumb is that you will need 100 amperes of current for every 1000 watts of power generated.

Calculating the size of the high-output alternator that is required to handle the entire electrical load of your vehicle is actually quite easy using the formula below.

The Alternator’s Minimum Continuous Duty Output in Amperes (At your intended operating speed) = Maximum Electrical Load on a Vehicle (For vehicles, this is typically 40% of the maximum factory alternator output amps.) + 50% of the Total Battery Bank Capacity (in amp-hours) + Average Current Needed to Power Non-Stock Loads.

For example: suppose you want to install an amplifier that requires 100 A in a vehicle that uses a 60A alternator and a 200 ampere per hour battery. The minimum continuous duty needed to operate this stereo is: (40 % of 60A) + (50 % of 200 Amp-hr) + 100 A = 224 A. this means that your alternator needs to continuously produce 224 amperes.

Assuming your alternator produces at least 120 % of your total electrical energy: The size of your high-output alternator (120 % of 224) = 268.8 A. this would mean that you need an electrical charging unit that gives at least 268 A. in this case, the 300 A alternator would be better.

These types of alternators are typically large, and you might have to make room for them in your engine compartment. Unfortunately for you, there isn’t a choice for a one size fits all. Consult with your mechanic before buying an alternator that is not suited for your vehicle.

Do You Really Need a High-Output Alternator?


Reconfiguring the wiring in your vehicle to boost the flow of current could eventually do more damage than good. The Big Three wiring upgrade is an excellent choice under certain circumstances. However, if increasing the current flow in your car made the problem worse, then it’s time you looked into a high-output alternator.

Each electrical component in your car requires a minimum amount of current to function. Unless you are planning on making any changes to your electrical components that lead to an increase in the total amount of amperes they require, then your factory alternator will work just fine.

During the manufacturing process, stock alternators are made to fit your car’s power consumption needs almost exactly. This becomes a problem when you want to upgrade to a fancy stereo that will obviously require more current. Therefore, installing aftermarket equipment with a high demand for current electricity will cause a deficit in your car. This will mean that some of the electrical devices in your vehicle will have a shortage of current.

This shortage manifests as flickering dashboard lights or dimming headlights when you open your windows or play your stereo on full blast. Considering your engine runs on an electrical charge from the alternator, it might cease to function while you are driving and in the middle of the road.

Increasing the load on an already exhausted alternator could result in premature failures, such as a dead engine. Wiring it to boost the flow of charge or replacing it with an alternator that has the same qualifications is not going to cut it. For your safety and to ensure your car is working under optimal conditions, you will require an upgrade such as the mechman alternator. Otherwise, you would just be postponing a future problem.

Will a High-Output Alternator Cause Damage to Your Car?

Damage to Your Car

When it comes to alternators, you can never have too much current flow. Whether it’s a 200 A or a 300 A high-output alternator, it will not cause harm to the components of your car that benefit from it. This is because the amount of current your high-output alternator can produce is based on supply and demand.

The total amount of current required when your engine is idle versus when you are driving on the highway is totally different. Even then, this fluctuation would have to be covered when choosing the correct high-output alternator for you.

So, when your components cumulatively require 150 A, the alternator will only supply 150 A – no more, no less. This means that if you have a high-output alternator valued at 300 A, the extra charge will not harm your vehicle’s components because the charge is only released based on the demand.

The most significant downsides to installing a high-output alternator are that if your audio system does indeed require that much current, you’ll need to make a few tweaks and improvements to your engine compartment before installation. The additions are mainly a preventative measure to keep the power and ground cables from short-circuiting by installing better cords. It also helps to shield the delicate electrical components that keep your car running.

The other downside is that improving your alternator by replacing it with a better one or adding an extra stock charging unit might void your warranty. This is because the new charging system is not part of your original car feature. Hence, according to the Magnuson Moss Warranty Act, a manufacturer is not liable for warranty repairs caused by someone else’s parts.

Types of Modifications Required to Install a High-Output Alternator?

Modifications Required to Install a High-Output Alternator

There are a ton of compelling reasons to upgrade to a high-output alternator. However, you must first do your due diligence by conducting some preliminary research. A high-output alternator does not necessarily require any modifications. Some alternator manufacturers, however, recommend replacing both the ground straps and the charge wire. Remember that the factory cables were not designed to handle the power of a high-output alternator and may cause resistance to the flow of current.

Since a high output charging system will produce far more power than the factory alternator, and your power and ground cables were selected with the original equipment manufacturing unit in mind, these cables may be insufficient. When installing a high ampere alternator, consider replacing the ground straps and the power cable that connects the electric generator to the power supply with thicker and heavier gauge cables. The best recommendation would be to install the thickest gauge that is best suited for the assignment.

A few factors to consider when making modifications include:

  • Do you need a method of maintaining your engine when the car is stationary; when parked, or in heavy traffic.
  • If a dual charging system with multiple batteries is a better option. Your car could use a small battery and an alternator for normal operations. For accessory loads such as a new car stereo, an extra high-output alternator can be used to supply the additional amount of current.

An Extra Battery vs A Bigger Alternator: What kind of alternator do I need for car audio?

dual car battery

Whether you need an extra battery or a high-output alternator is dependent on your car. Every case is different, so there is no straight answer for this. A new stereo system that requires a higher electrical pool requires an electrical system that can support its needs. This means choosing an upgrade that puts every aspect of your car’s performance into consideration. This change should not compromise the flow of current to your electrical components. At the same time, your enjoyment of car audio should not be compromised.

Some alternators might be able to handle the electrical requirements of your newly installed stereo. If not, here are some common signs that you need an upgrade:

  • A song with a heavy bass comes on, and your lights start to dim
  • Increasing the volume of your audio causes your headlights to dim
  • The performance of other electrical components of your car, such as opening and shutting the windows, is affected when the stereo is in use
  • Your electrical components seem to work better when the volume on your car audio is at an extremely low setting
  • There is visible corrosion buildup on the terminals of your car batteries

If any of these scenarios apply to you, you need to consider an upgrade.

Upgrading the Battery


When using the car stereo for extended periods, a secondary power supply is needed. They are also required for systems with a high power draw and scenarios where the electrical demand exceeds the alternator’s supply. The secondary battery functions as a backup power supply for all your car accessories when your vehicle is turned off.

If you have enough space under the hood to replace your original battery with a relatively larger one, that’s the simplest way to boost your ampere-hours. This will allow you to listen to music on your sound system for a more extended time without having to restart your car to enable the alternator to recharge the battery.

On the other hand, wiring two batteries in parallel will configure them to act like one battery with twice the capacitance. Keep in mind that when you do this, the two batteries need to be of equal strength and age. Wiring together batteries with different charge output and efficiency will make them strain to equalize the voltage difference between them. This constant cycling of charges will lead to a shortened lifespan for both the batteries.

Upgrading the Alternator

This option is best suited for car owners with limited space in their engine compartments for two batteries or a bigger one. Upgrading your alternator with a high output one or adding a second alternator is the best way to ensure your vehicle’s electrical parts receive the total current that they require.

Consider this, upgrading the battery in your car is like adding more water to your cup while boosting the alternator is similar to increasing the force in your straw. Whichever method quenches your thirst best is the option you should go for.

Do You Need a Big Three Wiring Update?


The “Big Three” electrical upgrade is a better and less costly improvement to your electrical unit. It will considerably improve the electrical system of your vehicle by allowing more current to flow to all the electrical components. Think of it as having a wider straw for your cup of water. This upgrade replaces or enhances three critical electrical cables with 1/0 gauge or 4 gauge wires. These wires include:

  • The charging wire from the alternator that is installed to the positive terminal on the battery
  • The chassis ground wire that is installed to the negative terminal on the battery
  • The ground wire that is installed from the engine block to the chassis

It increases the amount of electrical current that can flow through your high-output alternator. The Big Three wiring upgrade works by lowering resistance and increasing current capacity in your charging system to improve more than just the performance of your car stereo system.

However, this has the potential to increase your headlight dimming because it allows your amplifier to pull more current from your alternator. This occurs especially when your charging system is unable to provide the necessary current required by your vehicle’s stereo.

Before making any other changes to your electrical unit, consider installing the Big Three update as a preliminary measure. It helps you rule out possibilities to your voltage drop problem before going in with expensive improvements.

Modern Stereo Solutions for Your Classic Car

Can you install a modern radio in a restomod

A vintage-style car radio is one that greatly resembles the features of the original radio with some added modern features. The centerpiece of your vehicle’s sound system is your car stereo. The source, preamp, and amplifier work together to create a user-friendly acoustic machine.

The only way to obtain optimum sound performance and quality is to revamp this critical component. If your classic car requires a solution for a stereo that does not compromise the retro style it already has, then we have two solutions for you:

  • A Modern Radio Disguised as a Classic Car Radio: This is done by removing the older stereo version and replacing it with an identical piece with better features.
  • A Secret Audio System: It can easily be installed next to your existing audio system and remote-controlled. The central unit can be hidden anywhere in your vehicle.

The benefits of modern radio in a classic car include maintaining your car’s retro style while allowing you to experience music using a current device. They are also easy to install and fit precisely to your compartment.

The Ultimate Guide To Upgrading the Audio System in Your Restomod, by our friends at Restomod Academy, is a great resource for classic car and restomod audio upgrades.


Installing a new stereo system in your car will most likely require upgrading one or more of your electrical compartments. These upgrades require working with devices drawing large amounts of current. While manufacturer instructions come with the installation of these devices, ensure you don’t DIY the process unless you completely understand what you are doing. Contact Music In Motion for an evaluation of your audio system’s electrical needs.

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