Your vehicle’s alternator is the main source of power when your vehicle is running. Some individuals think that all of your accessories just run on the battery, but in actuality, your battery is only really designed to start the vehicle. After started, the alternator takes over providing the electrical power for the vehicle’s accessories. In this post, we’ll look at why your stock alternator is not up to the task and why upgrading to a high-output alternator is so important when installing car audio components.

Your Stock Alternator

Did you know the stock alternator only supplies about 50% of its current output to non-factory accessories like an aftermarket amplifier? Most automotive manufacturers install alternators that range anywhere from 70 to 130 amps. These alternators are designed to provide the bare minimum in terms of amperage to power the vehicle’s accessories in its stock form. 

Now, enter that 1500 watt RMS amplifier you just installed. In order for that amp to produce its full 1500 watts, it will take somewhere around 200 amps of current. That’s a lot! Now, on a daily basis listening to your favorite music, the amp will not be producing that full 1500 watts all the time, but it will still be drawing a lot of current from the stock alternator, thus putting a lot of strain on it, your electrical system, and audio system.

It Takes Power to Make Power







So, you’ve heard it before. And, you’ll hear it a lot from the people who know and have the experience in-car audio, “It takes power to make power.” This statement is so true. Sure, you can add extra batteries as reserve power, but where do you think those batteries will get their power from when they begin to feed your amplifier? Is it that 80 amp alternator under your hood? I don’t think so! This is not good for your stock alternator, and it’s definitely not good for your audio components. 

In my opinion, if you are going to add a car audio system to your ride, you first should consider building a strong electrical foundation to support that system. This will allow you to reap the full potential from your equipment and BASS it out for years to come. But here it comes, I can hear you now. “But a high-output alternator is like $500 or more!” You know what? You’re completely right. But think about this. You want to spend around $1300 for that brand new SALT-4, right? What is going to power that behemoth, and what do you think will happen to that amp running it with a stock alternator? Only feeding it about 65 amps, on a good day, will definitely not end well. Is that smoke I smell? 

Listen, I get it. $500 seems like a lot of money for something you won’t see more than 95% of the time when you’re banging that new system, but in the long run, that $500 now will save you a lot of grief and money in the long run. 

So What Size Alternator Should I Get?

Good question, I’m glad you asked. The simple answer, in my opinion, as big as you can afford. This is especially important if you plan on upgrading, and growing your system in the future. With that said, it all depends on what is going to be included in your system. For a basic subwoofer and amplifier install, I’d recommend a good 250 – 300 amp alternator. This should provide all the power you need to keep your system healthy. If you truly are unsure of what you may need, contact one of the high-output alternator builders. They are extremely helpful and will recommend exactly what you need for your vehicle based on your vision or your current build setup. 

Once you get that shiny new H.O. alternator, there’s one thing I would highly recommend, especially if you are unsure about it. Have your alternator installed by a professional. Do your research here. High-output alternators are usually not just swapping out the stock and installing the new. Sometimes things like your serpentine belt will have to be changed to a different size in order for the alternator to work properly. The alternator builder will instruct you if this needs to be done. This is determined by the pulley size on the alternator. 

Another step to take, before purchasing or installing a new alternator, is to research the charging system of your vehicle. Many vehicles today have the voltage controlled by the ECU. This is a fuel economy feature, but it can really affect your car audio system even with a high-output alternator. In some cases, this “feature” can be bypassed, but in others, it cannot be bypassed without causing another issue like a check-engine light or throwing the vehicle into “limp mode.” So, make sure you look into this. There are other ways to control the voltage output of these alternators such as external voltage regulators, but I’m not going to explain that here. The alternator builder can recommend and explain that if needed.


So, there you have it. The reasons you should consider installing a high-output alternator, and why it is a crucial part of planning and implementation of your car audio system. I hope I gave you some insight in regard to H.O. alternators and it is my hope that this post will encourage you to get one for your build. 

NOTE: Please be aware that installing a high-output alternator will require your vehicle’s charging system wiring to be upgraded. You can learn more about this upgrade called the BIG 3 in my previous post “WHY BIG 3 UPGRADE?

How to Choose a High-Amp Alternator

About The Author Brandon L

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