What capacitor size do you need for a car amplifier?

You may have various reasons behind wanting a new capacitor for your car’s amplifier, such as when the existing one you have starts to show signs of poor audio quality or has run past its course. You can know a bad capacitor by seeing signs of swelling on it, as well as seeing if it is struggling to hold on to voltage – if it cannot, then it is useless at its job.

When choosing a car capacitor size, the general rule is to put 1 Farad capacitance for every 1000 watts of total power the sound system produces.

However, you will not damage the system if you use a slightly larger-value capacitor, as the larger types are more adaptable to the amplifier’s big hits.

What is a capacitor and how does it work?

This is a component that can keep and release electrical energy at a quick rate. This allows it to work as a buffer or filtration system for sudden changes in the voltage of a circuit, and smoothen the output signal. In a car audio system, a capacitor can work to reduce the chances of the lights dimming when the audio system plays bass-heavy notes at high volumes because they will give the amplifier a quick burst of power.

Do you need a car capacitor?

You may not always require a capacitor, and it is important to determine this before settling on a specific size. There are certain factors that will increase your need for the component, and they are:

  • If your car battery is a low-capacity one
  • If the alternator is underpowered
  • If the amplifier in your sound system is very powerful
  • If you are using a low-gauge and/or long power wire

These issues will appear in your car in form of sluggish windscreen wipers or dimming headlights when you turn up the bass or your car’s stereo system. However, it is also important to keep in mind that installing a capacitor will not help the system if the amp is too powerful or the entire setup is severely underpowered – you must ensure all the components in the audio system have even power handling abilities.

If you rectify issues with the audio system components and still experience declining performance in the wipers or headlights, then a car capacitor is best.

Features to look for in a car capacitor

Value rates

Measured in Farads, this is the most essential feature to look for, as it is a measure of the amount of charge the capacitor can hold. You will need more farads if you have a more powerful amplifier, and less farads if your amplifier is less powerful.

Surge value

This is the second most important component, and you will need to ensure the capacitor has a higher DC rating than your battery and alternator. With that in mind, ensure you choose the correct voltage rate carefully because a voltage that is too high or low will damage the capacitor beyond repair.

Terminals

If the capacitor has more terminals, it will accommodate more components. A smaller capacitor will usually have two terminals, while a larger one can have more. If you get one with additional terminals, it can prove useful if you want to use it as a distributor and install other hardware in your sound system.

Types of capacitors in a vehicle audio system

Capacitor typeFunctionality
ElectrolyticHave a faster recharging rate, but they hold less power. They are usually in a round canister design, and they use one farad for 1,000 watts of power.
CarbonThese are the opposite of the electrolytic capacitors, as they hold more power but are not fast rechargers. They use the same farads as electrolytic capacitors.
HybridThese are a mix of carbon and electrolytic types, but can be larger and pricier. As a rule, they will use 5 farads for every 1,000 watts, so they will work best if you want a backup battery.

What capacitor sizes are best for my car’s audio?

Regardless of these suggestions, always note that the electrical system your car uses may be unique in its requirements and specifications, so choosing the appropriate size should be a careful process. These suggestions are more of general guidelines to use.

The total wattage in your car systemCapacitor Farad rating to go for
Below 500 wattsLess than 1 Farad
Between 500 and 999 wattsBetween 1 and 1.9 Farad
Between 1000 and 1499 wattsBetween 2 and 2.9 Farad
Between 1500 and 2499 wattsBetween 3 and 4.9 Farad
2500 watts and higher5 Farad and higher

What may happen if I use a capacitor that is too small or too big?

While there exists a common notion that bigger capacitors are better than smaller ones, there is a limit you should not cross – choosing a cap that is too large or too small will actually affect the entire vehicle’s electrical system.

Choosing a capacitor that is too small will still rely on some of the system’s power for its electrical charge, but will ultimately be ineffective when you need to provide the amplifier with some additional voltage. The problem with using a capacitor that is too big is that it will destabilize the whole power supply, and possibly damaging the sensitive components in the car’s engine due to a large flow on incoming electrical currents.

Additionally, the capacitor can also generate large deviations in voltage, which can lead to overheating through its non-zero parasitic resistance (also known as ESR). Over time, this reduces the capacitance and leads to internal burning and breakdown. This is a particularly common issue with aluminum capacitors, which is the reason behind their limited lifespans.

Conclusion

Choosing a bass-heavy and loud audio system for your car is a good thing, but it can, unfortunately, hinder other car components like your engine’s alternator, the car lights, or the battery. Therefore, choosing a high-quality capacitor is important to alleviate issues with the car’s operation, as it will store enough energy for other activities.

Andrew Gibbons

According to Andrew Gibbons, playing the guitar is fun but it will take a few months before you can come up with a creative expression. Gibbons is a guitar instructor and has been teaching University music programs for over a decade, when it comes to playing the guitar a lot of factors come into play that determines the type of sounds produced. The guitarist must consider the guitar's neck and body shape, weight, and string type, the amp is also a primary determinant of the sounds produced and that is why Gibbons has created extensive excerpts detailing on the delicate topic. Guitarists must also pick a pose, be it the pro, wizard, hipster, or the old master.