How to Charge Car Audio Capacitor

When you use big accessories like an upgraded car stereo, your electrical system can often feel the strain.

So, if you feel like your accessories are fighting for the power they need or if you notice that your headlights are getting much dimmer, it’s time to get a capacitor.

Before we talk about how to charge a car audio capacitor, it’s important to know what it is and how it works.

A car audio capacitor is a device that doesn’t need power but temporarily stores electricity. It has two metal plates that conduct electricity and a material that doesn’t conduct electricity between them.

If a capacitor is connected to the power source, the non-conductor stops the voltage from moving between the conductors. Between the plates, a static electric field is made, which makes the charge build up. When the capacitor is connected to an outside circuit, this current goes away quickly.

There are three types of capacitors for car audio:

  • Electrolytic
  • Carbon
  • Hybrid

Moreover, every capacitor has a particular capacitance (the maximum amount of energy a capacitor can store).

An electrolytic capacitor can be charged quickly, but it doesn’t have a lot of power. A carbon capacitor, on the other hand, holds more power but takes longer to charge. A carbon capacitor and an electrolytic capacitor are put together to make a hybrid capacitor.

Most of the time, a capacitor is put near the amplifier to improve how well it works. This job makes sure that the voltage drop is kept to a minimum so that the whole electrical system works well.

A capacitor constantly charges and drains. For a capacitor to charge, it needs to be in a full circuit, which means it needs a power source, a path, and something to charge. If there is no load, the current will flow through the circuit, but the capacitor will not be charged.

Also, as a general rule, you should connect the positive end of the capacitor to the positive end of the car battery and add a resistor between the two.

A load is added to a circuit by a resistor so that the capacitor can be charged. Next, connect the negative end of the capacitor to the ground chassis, but not where the amplifier is.

A capacitor can also be charged to the maximum voltage level of a battery. For example, a normal 12V battery won’t charge a 1F or 18F capacitor to more than 12V, no matter what size the capacitor is. Most car sound systems will only need capacitors between 2F and 5F.

Having used and tested them, I think the three capacitors below are the best for car audio.

  • 5.0 Farad Digital Power Capacitor
  • Planet Audio PC20F 20 Farad Car Capacitor
  • Belva Professional Grade 1 Farad Capacitor

Why does the stereo in your car need a capacitor?

1.It stabilizes the voltage of the amplifier. Car audio systems with a lot of wattage or a lot of amplifiers need a lot of current from the car’s electrical system. Depending on the songs that are being played, the amplifiers may need short bursts of energy, mostly when transient peaks happen. Voltage sag is the drop in voltage that happens when you try to take this current straight from the electrical system. This sag depends on how hard the wire between the battery and the amp is to move. So, a capacitor is used as a back-up to store energy and release it when the amplifier uses more power than the electrical system can handle.

2.It keeps the amplifier from getting too hot and makes it work better. If a capacitor steps into power, it helps an amplifier that was about to strain for power stay cooler for a long time. Also, the amplifier works better and gives the best sound it can to the sound system.

3.It keeps your headlights on. When your car’s headlights get dim, it means you’re running out of power. Since a capacitor stops the amplifier from drawing a lot of power from the electrical system, you won’t have to worry about your car lights going dim very often. You can play your subwoofers loudly all day and night without worrying about the lights.

It stops your music from getting weaker and flatter when you play heavy bass. Because the amplifier has support to keep putting out power, there is less distortion in the sound. Capacitors are linked to better transient response because of this property. They help the amplifier sound better even when the bass is really low.

How do you get a capacitor to hold a charge?

When connecting and charging a capacitor, there are a few main things that are important:

  • Capacitor
  • A power wire is about the same size as the rest of the audio system’s wires.
  • Wire strippers/ crimpers
  • A way to remember
  • Pliers

How to Charge car audio system capacitor 

  • Charging with a resistor

New capacitors come with a simple plate with a resistor and four wires that can be used to charge them.

Two of the wires you have should be connected to the capacitor’s positive and negative terminals. Connect a second positive wire to the positive terminal of the battery and a second negative wire to the car’s base to ground the wire.

Also, it is very important to remember that you can’t connect the negative terminal to the ground of the audio system.


  • Use the parking brake and park your car on a flat surface.
  • Connect the memory saver.
  • Unplug the battery’s ground wire. Start with the negative wire because if you start with the positive wire and touch the car, you might cause a short.
  • Get the wire that you want to use for the positive connection. Make sure that wire doesn’t have a fuse, or you’ll blow it when you close the circuit.
  • Connect the wires together.
  • Join the capacitor to the sound system. When the capacitor is all hooked up, put it on the vehicle.
  • Connect the capacitor’s negative end to the ground. Make sure that you connect the new amplifier to a different point on the base than the one that is already there.

After you’ve done these things, the capacitor will start to charge, and after a few minutes, it will be ready to power the sound system.

Capacitors can be charged without a resistor

Like we said before, if you don’t have a resistor to complete the charging circuit, you can still charge the capacitor with a lightbulb.

You need these extra things:

  • 12V light bulb
  • Light bulb socket

When you gather all the elements, follow the following steps:

  • Put the capacitor close to where the battery is.
  • Connect the negative end of the capacitor to the car’s base.
  • Putting the test light bulb between the positive end of the battery and the positive end of the capacitor with alligator clips. Then, keep the test light in place for a few minutes.
  • Once the capacitor is full, turn off the light bulb.

How long does it take to charge a capacitor?

A busy car owner would like to know how long it will take for a capacitor to charge.

How long it takes to charge a capacitor depends on how big it is. On average, the capacitor will be fully charged in less than 5 minutes.

When you compare how long it takes to charge a battery to how long it takes to charge a capacitor, you’ll find that a capacitor charges faster.

How do you know if the capacitor is full?

Worried that the capacitor hasn’t been fully charged?

Look at the current value on the voltmeter screen to see if a capacitor is fully charged.

But even if there is no digital display, there are other ways to tell if a capacitor is charged:

  • Use a voltmeter.
  • Use a multimeter for analog.

Also, it is important to remember that the capacitor should have a voltage above 13V when it is fully charged and ready to be put in the car.

Also, if you use an external multimeter or voltmeter to find out how full the capacitor is, you must connect the multimeter’s red positive terminal to the positive capacitor terminal and the negative terminal to the negative capacitor terminal. The exact voltage of the capacitor will be shown on the screen as a number.

How many times can a capacitor be charged?

The parts of capacitors, especially those that store a lot of energy, wear out over time because of mechanical factors caused by discharges.

So, the capacitors have a limit on how many times they can be charged. Electrolytic capacitors, on the other hand, can handle a lot more charging cycles than others.

When the audio capacitor isn’t charging, what happens?

If the circuit is not full, the capacitor might not be able to charge. A circuit like that needs a power source, something to power, and a way for the current to flow.

Remember that a resistor or a test light bulb can be used as a circuit load.

Last but not least, if your capacitor is broken, you should replace it.


To sum up, no one wants to always have to run out and buy a new car part. But if your car’s battery is focused on running the audio system, it could damage some important parts.

For instance, the battery or the alternator could be broken. So, a charged capacitor does the job of the audio system, since the battery powers everything else in the car and the alternator starts the engine.

Still, it’s important to be careful when working with capacitors. When they short out, large capacitors can be dangerous. Also, remember to empty a capacitor before you throw it away, because it could start a fire if you don’t.


Leave a Comment