What Size of Fuse do I Need for My Car Amp?

The fuse size you need for your car amplifier will depend on its maximum power output.

For example, if your amp has a max power output of 1250W, the fuse size you need will be:

1250/14.4 (car voltage) = 86.4A

Since there’s no 86.4A fuse, we’ll go with the one having a slightly higher amperage. i.e., a 100A fuse.

What Fuse Size Should I Put In My Car Amp?

In this post, we’ll discuss this formula and car amp fuses’ importance in detail.

What is a Fuse?

The fuse is a small electric component that protects our car’s audio components against overload.

The fuse blows and breaks the circuit when the current exceeds a specific limit. This, in turn, cause the current flow to stop – preventing damage to the components.

And it’s not just related to the car audio. Every vehicle has various fuses dedicated to components like HVAC, 4WD, interior lighting, the power liftgate, ABS/traction control systems, etc.

You can find these fuses in the fuse box – usually located in the engine compartment or under the dashboard.

As for the car amplifiers, you get two fuse locations. One is their built-in fuses that are usually plugged at their rear side.

The other location is the power wire from the battery to the amplifier.

Why Should I Use An In-Line Fuse?

There is a common argument people make against the in-line fuse on the power wires.

According to them, what’s the point of these fuses when the amplifier already has a built-in fuse.

What they don’t realize is that the built-in amp fuse is there to protect the amp, not the whole circuit.

A short circuit can damage the power wire even if the amp has built-in fuses – as there’s no fuse to protect the wire. It can also damage your vehicle as the power wire runs through the engine compartment.

This is where the in-line fuse comes in. This fuse should be installed closer to the battery so that a minimal amount of power wire gets damaged in case of electrical overload.

Types of Amp Fuses

In car audio systems, three main types of fuses are commonly used: blade, glass tube, and ANL.

Blade Fuses

These are simple fuses with two metal prongs in a plastic body. These are usually used as built-in fuses for the car amplifier.

Glass Tube Fuses

These fuses consist of a glass tube containing a metal strip. They’re usually used as the in-line fuse on the power wire.

I am not a huge fan of these fuses, to be honest, as they get loose after some time and are not as tightly connected as the other fuse types.

ANL fuses

These are the most commonly-used fuses for power wires. They come with a flat, rectangular shape and look similar to blade fuses – despite being larger.

What Size of Fuse do I Need for My Car Amp?

The correct fuse size for a car amplifier is essential for the latter’s proper functionality.

That’s because a smaller-sized fuse will frequently blow – causing your amp to go into protect mode. And a bigger-sized fuse will fail to protect the amplifier as it’ll have a higher current handling capacity than the amp.

To find the fuse size for your amp, check its specifications or calculate it using this formula: I= P/V.

This ‘I’ is the amplifier’s current draw that can be determined by dividing the power output (P) by the voltage (V).

Let’s say you have a 1000W Class-D amplifier. In such a case, we’ll divide 1000W by 0.8 (as they’re 80% efficient) to get the power output. If you have a Class AB amp, you’ll have to get the value by 0.5 (as they’re 50% efficient).

Therfeore, P=1000/0.8=1250.

And we already know that V (voltage) = 14.4V for car audio systems.

By putting both values in the I=P/V equation, we have

I=1250/14.4 = 86.8A

It means we need a fuse with 86.8A amperage. But in reality, there’s no such fuse. You either get an 80A fuse or a 100A fuse.

It’s better a get a fuse with a slightly higher amperage, as amps can handle marginally more power than listed in the specs. Also, if you put a lower-value fuse, it’ll blow frequently.

Therefore, we’ll go with a 100A fuse for our car amplifier.

As for the in-line power wire fuse, its amperage will be the sum of all amp fuses. For example, if we have two amplifiers in our car audio system, with 60A and 80A fuses, we’ll need a 140A fuse on the distribution block for the power wire.

Conclusion

Installing a larger or smaller fuse size can harm your car’s audio system and the vehicle.

That’s why no matter what fuse you use, have the correct size for your amplifier.

Fortunately, it’s a simple task. All you need to do is put value in a simple formula, as discussed above.

It will hardly take 5-10 minutes and is one-time work. In return, you’ll be safe knowing that the fuse will protect your car’s audio system if things go wrong.

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