To upgrade your car's stereo quality, many consider adding an amplifier. But, do you know how many amp fuse for a car stereo is needed to protect your internal gear and wiring? The easiest way to determine the size of the ampere fuse is to calculate the car stereo ampere draw by dividing the maximum watts or power rating of the amplifier by the alternator's voltage rating.
For example, if you're installing a 300-watt amplifier, and the alternator of your car produces 14.4 volts, you'll need a 300/14.4= 20.8~21A draw. So, you should go for a 30A class D fuse. You can also check the ampere rating on the amplifier and choose a fuse accordingly.
However, many different factors come into play here, so we'll guide you to the right way of figuring out the amp fuse rating for your stereo. Let's dive in.
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Your In-Built Amplifier Fuse Won't Protect the Wiring - Beware!
As you might know, most amplifiers come with an in-built fuse to protect the device. That's why many people tend to think they won't need any extra fuse for further protection.
But that's not practical at all as the in-built amp fuse is only going to protect its internal part, but not the wiring of your car.
Your car amp will draw a huge amount of power through the car cables. So, if you don't install an inline fuse to protect those cables, the extra power might burn them and even cause a fire in some cases. Therefore, adding an amp fuse is a must before you install an amplifier on your car stereo.
Calculate Amp Fuse Rating for Your Car Stereo
Now, you should understand that the process we have described before is for ideal conditions where the amplifier uses maximum power. However, no device is 100% efficient and your amp will surely lose a considerable amount of power. So, if you want a more precise amperage rating, follow the methods given below.
Method One: Determine by Easy Math
Let's say your amplifier is rated to draw up to 100 watts. Typically, the system running voltage of your car ranges between 13.8 to 14.4 volts.
We would need these two units to measure the fuse amperage rating. Here, the required equation is-
Ampere rating= Current or power in watts/system voltage in volts
- As most class D amps are only 80% efficient, the required power output for a 100-watt amp will be: 100/0.8= 125 watts
- System voltage= 13.8 volts
Hence, The Amperage Rating = 125/13.8 = 9.05 A
Since there are no 9.05A size fuses available, you can either step up or down to choose the size. In this case, you can choose a 7A or 10A amp fuse for your 100-watt amplifier.
What If You Want to Install Multiple Amplifiers?
Follow the same math for each amplifier and add the ampere ratings to determine the final required amp fuse size for your car stereo.
Method Two - Check the Amplifier's In-Built Fuse
If your amplifier has a built-in fuse, check out the sides of the device to get the fuse rating mark. Also, you can look at the user manual for this information. Usually, you'll need a larger inline fuse than the in-built amp fuse.
Therefore, if your amp is rated at 25A, you'll need a 30A inline amp fuse to protect the gear and car wiring. Although it's the easy way, you should always do the math to determine the fuse size for more accurate results.
So, how many amp fuse for car stereo? Now you know the answer. As there is no easy way to determine how much power output your amplifier actually delivers, we can't be sure if our estimations are 100% accurate.
However, the methods we described are very useful and pretty close to the actual results. So, don't hesitate to follow them before you choose an inline amp fuse.