What’s the Best Car Audio Capacitor?

A car audio capacitor is an electronic component that can store, and discharge electrical energy very quickly. Car audio capacitors are used to filter or buffer any sudden fluctuations in a circuit's voltage, smoothing the ensuing signal. They store a temporary electrical charge that can be released later to feed your hungry amp during peak demands, which prevents your car's lights from dimming when loud bass notes play.

If you've upgraded your car sound system and you noticed that your vehicle has dimming headlights when your audio system is pounding, then that’s a clue that your electrical system isn’t quite up to snuff, and therefore you need to consider buying a car audio capacitor. Flickering headlights are an obvious sign that your amp is struggling with voltage fluctuations.

You might also need a capacitor when the amount of power that you amp(s) requires exceeds the power-generation capabilities of your car’s electrical system, or when your vehicle is equipped with a relatively weak alternator. That said, if your car's charging system is too under-powered, or your amp is insanely powerful, then installing a cap may not be enough, and you should consider upgrading your electrical system - particularly the alternator.

Some people believe that car audio capacitors can also improve car audio system's low end response and overall sound quality. That's not true. The main purpose of using a car audio capacitor is to support the amplifier by feeding it the power it needs for short bursts.

And thereby, prevents the sound from deteriorating due to under-voltage. So, while a capacitor won't improve your sound quality directly, it does make it easier for the amp to perform at its best.

Best Car Audio Capacitors

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How do I hook up a car audio capacitor?

Whether you've purchased a cap to prevent your headlights from dimming, or just for precautionary measures, you need to install it. You don't need to spend hundreds of dollars for an easy installation that you can do yourself. One should always take caution when handling wires and electrical systems.

Before installing a capacitor, you must charge it (more on that down below). Use a voltmeter along with a resistor to charge your car audio capacitor. Once the voltmeter shows 12 volts, the power capacitor is fully charged. Now you can proceed to wire the capacitor in parallel with your amp.

Installing a car audio capacitor isn't rocket science, although it can be dangerous. Since large capacitors are capable of storing a great deal of wattage, you should be careful when installing yours. For safety purposes, new car audio capacitors are sold completely discharged.

So, before attempting installing your new capacitors, please read the safety and installation instructions before you get started.

New car audio caps usually come with a resistor or a wired light bulb that can be used to discharge the capacitor slowly and safely.

As in all car electronic installations, the very first thing that you should do is to disconnect the ground cable from the car battery. In this installation, also take out the in-line fuse on the amp's power wire next to the battery.

Bear in mind that your capacitor should be mounted close to your amp using the shortest wires possible. Also make sure the cap gets mounted securely.

Car audio capacitors have two terminals : a positive and a negative which should be clearly marked on the capacitor. The positive pole should be hooked directly to the positive amp connection, and the negative pole should be attached to your chassis ground — preferably in the same place as your amp.

How to charge a car audio capacitor?

To charge your capacitor, simply follow the steps listed below:

  1. Remove the fuse that connects your car audio system to the battery. It's usually in-line with the power wire of the amplifier that your capacitor is going to be connected to too.
  2. Now wire up your capacitor following the instructions detailed above.
  3. To begin charging your capacitor you'll need either a resistor or a test light. These are often included with the purchase of a capacitor but can be purchased separately if necessary. Charging a capacitor using a resistor is quite different from charging it using a resistor. We'll detail both methods.
    1. Using a Resistor : You will need a 1 watt, 30 – 1,000 Ohm (1kohm) resistor for charging your capacitor unless otherwise specified. It's highly recommended that you use a higher impedance resistor so that your capacitor is charged slowly. Put the resistor in line with your fuse holder, as though it were the fuse. Place the voltmeter positive(+) lead on the positive terminals of the capacitor and the negative(-) lead on the ground terminal of the capacitor and set the meter to Volts DC. Once the volt meter reads 11 or 12 volts you can remove the voltmeter and replace the resistor with the power fuse.
    2. Using a Test Light : A test light is the simplest and easiest way to charge a car audio capacitor. All you need to do is take the power and ground of the test light and place them in-line where the fuse used to be. To make it easier, use use alligator clips. Hold the test light in place of the fuse until the light bulb turns off which indicates that the voltage went from 12V to 0V and the capacitor is charged.

How to discharge a car audio capacitor?

There are various ways to discharge a car audio capacitor. The most important thing is to discharge it slowly. Here are a few methods you can use to discharge your capacitor :

  • Method 1 : Disconnect and remove the capacitor from your vehicle.  Use a 12V test light or resistor to bridge the positive and negative terminals on the cap together. For safety purposes, wear safety goggles and heavy duty gloves or hold the test light or the resistor with insulated pliers. If you've used the resistor to bridge the terminals of the cap, you'd know that your cap is fully discharged when the resistor becomes cool. If you've used the test light however, you'd know that the cap is discharged when the light goes out.
  • Method 2 : Another easy way to discharge the capacitor is to simply remove the main fuse that's located between the battery of the car, the capacitor, and the amp. This will make your capacitor the main source of power and act as the battery for your entire audio system. Then, turn on your audio system and wait for a few seconds till the amp turns off completely signaling that the cap is fully discharged.
  • Method 3 : Simply remove the capacitor from your car and connect it to any device that uses 12V DC for power. Keep the device running until all the energy stored in the capacitor is consumed. The device will then shut off indicating that your capacitor is discharged.

To make sure your capacitor is fully discharged, use a multi-meter or voltmeter and check the voltage across the terminals of the capacitor. If the meter reads zero volts or very close to it, your car audio capacitor has been successfully discharged. If you want to connect it again, don't forget to recharge it.