How To Charge A Car Audio Capacitor 

Norvan Martin

A capacitor is a crucial part of any car audio system. Essentially, car audio capacitors should be charged, especially when adding a new one to the system. This helps it to work perfectly well over a long period. But how do you charge the capacitor? We have prepared this article to help you answer this question. 

All you need to do is take the power and ground of the test light and stick them in line where your fuse used to be. You can use alligator clips to simplify this process. Hold the test light in place of the fuse until the light bulb turns off meaning the voltage went from 12V to 0V and the capacitor is charged.

how to charge a car audio capacitor

How To Charge A Capacitor With A Multimeter

A capacitor consists of two conductors placed close to one another and separated by an insulating material.

How To Charge A Car Audio Capacitor

It stores electrical charge in a unit called a farad within the ranges of picofarads, nanofarads to microfarads. 

To effectively charge a capacitor, you should wire the capacitor between the battery and the capacitor. You will need a multimeter to measure the voltage of the capacitor in the process – before charging, during, and after charging is complete. 

To charge a capacitor, assemble the materials required such as the capacitor, wires, switch, resistor, and multimeter, and follow the steps below. 

Step 1: Connect The Battery

Wire one end of the battery to the switch. It is recommended that you use a battery holder to make the wiring process easier. Also, ensure that the switch remains open while in the off position. 

Step 2: Connect The Resistor 

Wire the other end of the switch to the resistor. 

Step 3: Connect The Capacitor

Now connect the capacitor to the circuitry. Begin by wiring one end of the capacitor to the resistor and the other end to the free or unoccupied terminal of the battery holder. Ensure the connections are secure and stable. 

Step 4: Connect The Multimeter 

Place one lead across one end of the capacitor and the other lead across the other end of the capacitor.

If more wires are required to secure the connection, add more to ensure the leads are correctly connected. Set up the multimeter to its voltage reading mode. 

The multimeter measures voltage, current, and resistance. It comes with a display section to display the measurement readouts, buttons for selecting functions, a dial or rotary switch for selecting primary measurements, and input jacks where the test leads are inserted. 

Step 5: Insert Batteries Into The Holder

Because the multimeter is now set to read voltages, we can refer to it as a voltmeter. The voltmeter will read the amount of charge stored in the capacitor and display it in voltages. Insert a battery into the battery holder and close the switch. 

Once the switch is closed, observe the readings on display. The charge on the capacitor should be closer to the charge displayed by the voltmeter. This is because the capacitor quickly charges when the switch is closed. 

Step 6: Discharge The Capacitor

You can reverse the charging process by discharging the capacitor. To do this, remove the battery and replace it with a wire.

During this time, the capacitor releases its charge to flow through the circuit, and the amount of charge in it decreases. Consequently, the reading value of the voltmeter reduces to zero when the capacitor is fully discharged. 

How To Charge A Capacitor With A Battery Charger

Charging a capacitor is a straightforward process. As we already described above, charging a capacitor involves a device carrying a charge and connecting to a capacitor with some wires.

A capacitor is a device made of two conductors and an insulator in between—the insulating material stores charge in the capacitor. 

When you use a battery charger, and the C voltage is outputting more than the DC voltage source can charge, the capacitor charges up. Generally, if capacitors are connected to a 12V battery, they will soon begin up to a maximum of 12V regardless of their farad value. Follow the steps below to complete this process. 

Step 1: Pack the car in a safe place and apply brakes. 

Step 2: Plug in the memory saver.

Step 3: Unplug the ground wire from the battery beginning with the negative cable. Please note that unplugging the positive wire first may cause a short when you touch the vehicle. 

Step 4: Take the wire you intend to use for a positive connection and ensure it does not have a fuse. Add connectors to the cables.

Step 5:  Connect the positive terminal on the capacitor to the car audio system. Once connected, mount the capacitor to the vehicle. 

Step 6: Connect the negative terminal of the capacitor to the ground but at a different point than the one used by the existing amplifier. 

Once all this is done, the capacitor will begin to charge and can be used by the vehicle after some time. 

How To Charge A Capacitor Without A Resistor

Step 1: Place the capacitor close to the battery.

Step 2: Connect the negative terminal of the capacitor to the car chassis.

Step 3: Connect and hold a test light using alligator clips between the positive terminal of the battery and the positive terminal of the capacitor for a few minutes. The test light will turn off when the capacitor is charged. 

How To Charge A Capacitor With A Resistor 

Adding a resistor to the capacitor’s charging circuit helps control the charging time as it directly affects the time required to charge a resistor.

To charge a capacitor with a resistor, a resistor is connected across the circuit as we have described in the process of charging capacitors with a multimeter. Please refer to the step-by-step guide above and the diagram to see where to place the resistor. 

Symptoms Of A Bad Car Audio Capacitor 

  • Dimming lights during night drives.
  • Voltage keeps dropping even when the car audio system is not running.
  • Bass reduces on car audio system.
  • The audio system can’t play loud music, or the sound becomes poor. 
  • Smoke 
  • Bulges on the capacitor 
  • The capacitor leaks 
  • Computer malfunctions 

Best Capacitor For Car Audio

Capacitors help the car audio system by storing electric charges and controlling reactance. Although they store a relatively lower amount of energy, they are much more advantageous than batteries because they take less time to charge. 

Since many systems in the car, from the car audio system to the lighting system, demand a lot of energy, a capacitor comes in handy as it helps avoid straining the battery and alternator. 

Using the best capacitor will bring more advantages to your car, such as preventing the dimming of lights while driving at night due to low battery power. The alternator will run all the car activities more effectively with a powerful capacitor. 

Generally, there are three types of car audio capacitors;

The three types mainly vary in terms of the amount of energy they can carry. For instance, an electrolytic capacitor charges very fast but holds relatively lower energy. On the other hand, the carbon capacitor takes much longer to charge but has more power. 

Hybrid capacitors are a blend between carbon and electrolytic capacitors. They, therefore, share the properties of the two capacitor types. Therefore, most people prefer hybrid capacitors to find a striking balance between what carbon and electrolytic capacitors offer. 

Car Audio Capacitor Troubleshooting 

The Traditional Way

Troubleshooting car audio capacitors the traditional way should be done by a professional to avoid accidents.

Begin by disconnecting the capacitor from the power. Remove the safety leads and short the capacitor terminals. If you get a small spark, then the capacitor is in good condition. If the spark is small, then it should be changed.

With An Analog Multimeter

Discharge the capacitor completely and connect it to the multimeter. Now check for the following:

  • Good capacitor – the meter should be moving towards the infinite side, a sign that the capacitor is not bad.
  • Short capacitor – if the resistance is extra low, then the capacitor has a short and should be replaced.
  • Open capacitor – if there is no movement at all in the multimeter, the capacitor is defective and should be replaced.

With A Digital Multimeter

Charge car capacitor With A Digital Multimeter

Step 1: Discharge the capacitor.

Step 2: Connect it to the multimeter and set the multimeter to capacitance mode.

Step 2: If the value that pops up is equal to the one your capacitor has been given, then the capacitor is good. If the value is too low, then the capacitor is dead.


In conclusion, charging a car audio capacitor is important to ensure optimal performance and longevity. In this article. we provided detailed instructions on various methods to charge a capacitor, including using a test light, multimeter, and battery charger, with or without a resistor. 

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Norvan Martin is the founder of He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin