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Do Car Audio Capacitors Go Bad?

Installing a powerful aftermarket car sound system with subwoofers, amplifiers, and other components can be challenging for your electrical system to keep up with the increased power demand. But do capacitors go bad in the long run?

Car audio capacitors eventually go bad. They’re available to stabilize voltage and prevent spikes in audio play and resolve infrequent electrical issues, such as headlight dimming. With an electrical problem, it is preferable to upgrade the battery to add more power, rather than install a capacitor.

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In many instances, it’s best to install a capacitor to handle short bursts of extra electricity from your audio system since its purpose is to smoothen bursts of electrical current and add additional power capacity to your vehicle.

In this article, we will take a look at what a capacitor is and its purpose, what to look for in choosing one, and how to install it. Learn what capacitor failure looks like and what the causes are of a capacitor going bad. 

What Is a Capacitor and What Is It Used For?

An automotive system capacitor was once known as a condenser. Currently, in the car audio, capacitors are also called stiffening caps, or just caps, and are used to help the automobile’s charging system keep up with the sound set-up.

can car audio capacitors go bad

A capacitor is a temporary storage tank for electricity, and it will consume, accumulate, and emit electricity at a rapid pace, ultimately leveling spikes in a circuit’s voltage.

The purpose of a capacitor is to smooth an electrical signal. In a stereo system, a capacitor can prevent other components from being affected.

For example, it can prevent lights from dimming when the subwoofer delivers loud bass notes. A capacitor will provide a thrust of power to the audio component to steady the current and prevent the lights from dimming.

Noteworthy is a supercapacitor, or ultracapacitor, a high-powered capacitor. In comparison, the supercapacitor stores more energy, known as capacitance, which is a lower voltage and has a longer life before failure than a capacitor.

What to Look for in Choosing a Capacitor

While there are many capacitors to choose from, the A+Max Ultra Capacitor Car Audio System Current Booster on Amazon has a 5-star rating. It is meant for extreme weather conditions, –40°F to 158°F (–40°C to 70°C) and has a high-power audio system current booster, 15 Volt/90 Farads. It’s small, lightweight, and can be installed quickly.

It is beneficial to define a farad, coulomb, and voltage to understand how to choose a capacitor. A farad (F), named after its inventor, Michael Faraday, is a specific unit of measure as described by the current day metric system, International System of Units (SI).

One farad measures the ability of a system to accumulate an electric charge in a capacitor and describes the division of one coulomb, a unit of electric charge, by one volt of potential electricity. Therefore, a one-farad capacitor will hold one coulomb at a drop of one volt.

How does this work? The farad measurement indicates the level of electricity that a capacitor can store, ready for use. If the bass power from the subwoofer floods the electrical system, your vehicle will need a quick electrical boost.

Otherwise, the lights may dim. After the boost, the capacitor recharges, so it’s ready for the next event. To monitor your vehicle’s charging system, you may choose a capacitor with a digital meter displaying your system’s voltage. 

Additionally, differentiate between a capacitor and a supercapacitor with the help of this 18-minute video:

In the video, you will find a comparison of a 4 F capacitor to a 375 F ultra or supercapacitor with built-in Bluetooth for switching power modes, jumping batteries, and more. As expected, the smaller 4 F capacitor is cheaper but not nearly as powerful. 

How Do I Install a Capacitor?

Whether you’ve purchased a capacitor to correct dimming lights or as a cautionary measure to prevent minor electrical issues, the next step is to install it in your car.

Remember, a capacitor can be dangerous because it can discharge enough power to melt metal together, like tools or jewelry. Straight out of the box, the capacitor will be completely discharged for safety and includes a resistor for charging.  

Over 1 F, large capacitors are installed in parallel to a car audio amplifier system direct current power terminals. Tips for the best installation are:

  • Place the capacitor as far away from passengers as possible to prevent exposure to voltage but as close to the amplifier as possible to reduce wire length, thereby improving sound performance. 
  • Be sure to charge the capacitor before installation or risk blowing a fuse. Use a voltmeter with a resistor until it is at 12 volts. 
  • Use the correct wire gauge (usually 4 to 8 AWG) dependent on the capacitor’s specifications.
  • In contrast to a power cell, the capacitor can be located near the main battery due to an automatic shut-off when the sensor realizes there is no longer a change in voltage.
  • Choose the capacitor brand wisely. A low-quality component will not significantly enhance electrical storage and is thereby undetectable. 
  • Although you can wire in multiple capacitors, it’s best to only install the recommended size according to the sound system’s needs. Determine by checking the owner’s manual for the appropriate number of farads based on amplifier wattage.

Here is a tutorial on how to install a capacitor on a stereo system. It’s only 5 minutes long and indicates how simple it is to perform:

Always follow the user manual of the brand that you choose for exact instructions. Always follow the user manual of the brand that you choose for exact instructions.

What Factors Cause a Capacitor to Fail?

Henry Petroski said, “Successful engineering is all about understanding how things break or fail.”

As with all equipment, a capacitor doesn’t live forever, and its lifespan depends on various factors and conditions. For instance:

  • A ceramic, solid-state component can last many years under typical conditions, including run-of-the-mill car vibration and unremarkable weather. But long term moisture in the air, extreme temperatures, and prolonged use, or mechanical stress will cause failure.
  • If a capacitor exceeds its indicated Working Voltage Direct Current (WVDC) rating, the component will fail. For example, 50 WVDC.

What does failure look like? A capacitor is known to suddenly stop working, leak until failure, or slowly lose its capability, especially low-quality or mismatched components.

A supercapacitor also degrades with time. While the lifespan is much longer, it is still dependent on the very same conditions. According to an article entitled, Supercapacitors vs. Battery on the Arrow website, end-of-life criteria are measured in the number of charge/discharge cycles and range from 100,000 to 1 million cycles.

If the concern is a major electrical power issue, you may need to upgrade the existing battery, or add a second battery instead of installing a capacitor. By upgrading the battery, you will prevent electrical issues and increase the power capability of your vehicle. 


The pros of buying a capacitor is that it smooths out power delivery by maintaining a short-term energy storage system. The component can go bad after a while or suddenly fail, depending on mechanical, operating, and environmental conditions.

If you play loud bass, have an aftermarket subwoofer and an amplifier, it will be a wise choice to install the correct size capacitor to prevent electrical issues. If you have major electrical issues, it is best to upgrade to a battery that can add extra power instead of a capacitor for electrical consistency.