High Output Alternators and Car Audio Questions

Do you really need a bigger alternator for your sound system?

high output alternator for car audio
Stock alternators usually have enough juice for aftermarket audio, but there are cases where a high output alternator is the only way to go. PieroAnnoni / E+ / Getty

When most people think about great car audio, they think about high-quality speakers, massive subwoofers, and powerful amps. It's true that those are the key components to achieving truly awesome sound in your car, but there's one huge roadblock that very few people consider ahead of time: you just might need a bigger alternator for that sound system.

Car Audio Problems and High Output Alternators

It doesn't matter how well you plan out a car audio upgrade, how perfectly all of the components work together, or how professional the installation is. The fact is that if you want bigger sound, you need an amplifier, and if you want even bigger sound, that amp has to be huge, or you may even need more than one amplifier.

The thing about audio amplifiers is that in order to pump out that big sound, they need power. And the thing about the electrical system in most cars is that they are designed to provide just about as much power as the stock systems require. That means the alternator in your car will typically hum along just fine if you upgrade your head unit, but it may end up struggling to supply enough power to a big amp.

One of the first clues that their alternator isn't up to the task is flickering dash lights and headlights. There are other signs, but that's the most visible, and it's the one that you're most likely to notice. What it means is that the amp is drawing so much power that there isn't enough left over for other systems like the headlights.

Does Your Audio System Really Need a Bigger Alternator?

If you're experiencing a problem like flickering lights, there are a few different ways to approach the situation. The easiest fix is to just keep your volume at a level where the flickering doesn’t occur.

Since the problem is that your alternator can’t meet the demands of your amplifier at high volumes, simply keeping the volume down will allow you to avoid the problem while still enjoying the increased sound quality of your premium car audio installation.

If you have your heart set on cranking up that volume, then there are two other options. The first is to install a stiffening cap, which doesn't always work. The other is to install a high output alternator. This is an expensive option, but it's the only way to make sure that your high-performance audio system actually gets the current that it needs to work properly.

Capacitors vs. a High Output Alternator for Car Audio

If you only experience problems at extremely high volumes, and you really want to play your music that loud, then there's a chance that a car audio capacitor may solve your problem.

Car audio capacitors are also known as stiffening caps, and they essentially act as a reserve tank that can provide a little bit of emergency current during times of especially high demand. That basically just means that when your car audio system tries to draw more amperage than your factory alternator can provide, the capacitor makes up the shortfall.

If a stiffening cap won’t do the trick, make sure that it's installed as close to the amplifier as possible. If that doesn't do the trick, and you can't afford to upgrade your alternator, then you may just want to avoid overtaxing your factory alternator.

If you start to experience flickering lights and drivability problems even at lower volumes, then a high output alternator is probably going to be the solution that you’re looking for.

Some high output alternators are specifically designed for car audio systems simply because that’s where the market demand is. However, high output is high output. Whether a unit is labeled as a car audio high output alternator or not isn’t as important as the actual amperage ratings.

With that in mind, it’s important to know roughly how much extra demand your sound system is adding to the mix, which will allow you to select a high output alternator that won’t leave you wanting more.

High Output Alternator Car Audio Demands

In order to figure out roughly how much capacity your new alternator is going to need, you’ll want to determine how much extra demand your car audio system is adding to the mix.

Although it isn’t perfect, the easiest way to ballpark this is to use the formula of amps * volts = watts.

So if you added a 2,000 watt amp, assuming a nominal voltage of 13.5V, you’d be adding roughly 150A of demand to your electrical system. This obviously isn’t an exact figure, and your amp will draw less than this during most usage, but it is a quick and dirty way to get the ball rolling.

If you wanted to be precise, you would need to find out how much amperage every component in your car draws, add in the needs of your new sound system, and use that to determine the necessary rating of your alternator. Of course, you can always just ballpark this too by checking the rating of the factory amp, adding on the extra demand of your car audio system, and then just use that figure to find a replacement.

Idle Output Vs. Rated Output

The last thing to understand about high output alternators and car audio systems is that the rated output of an alternator typically refers to the amount of current it can produce when you’re cruising down the highway at high engine revolutions per minute (RPM).

When your engine is idling, or really any time it isn’t held at a high RPM, it will only be capable of providing a fraction of that amperage. In some cases, an alternator may only be able to put out half of its rated output.

This is why most people tend to notice problems like flickering lights when the demand is highest like the volume is cranked up, and the production ability of the alternator is lowest, like when idling in traffic or at a stop light. With that in mind, some edge cases can get by just fine if they just turn the volume down whenever the engine RPM is on the lower end, while others require you to choose a higher amperage alternator.