How to Discharge a Capacitor

Car audio capacitors add stability to any audio system by keeping a small reserve of power available for the amplifiers when they need it for quick musical peaks. If you need to remove your capacitor or move it into another vehicle, it is always a good idea to discharge it. Capacitors store energy and can take a long time to dissipate that energy, sometimes a year or more, leaving a disconnected capacitor a disaster waiting to happen. Larger capacitors can store more energy than smaller ones so it takes longer to discharge and they are more dangerous to handle as a result. Always use caution when working with these devices. There are many different ways to discharge a capacitor and it is important that it discharges slowly. Here are a few methods you can use to discharge your capacitor:

Method 1: Remove the capacitor from your vehicle and make sure to handle with care. Take a 12V test light or resistor and touch the positive and negative terminals on the capacitor bridging them together. Make sure to wear safety goggles and heavy duty gloves or hold the light/resistor with insulated pliers. The resistor or light will get very hot and could pop. Once the light goes out the capacitor is discharged. When the resistor becomes cool the capacitor is discharged.

Method 2: Remove the main fuse located on the power wire near the battery of the car that connects to the amplifier and capacitor. This will then make the capacitor act as the battery for your audio system. Turn on your audio system and wait for the amplifier(s) to turn off completely signaling that the capacitor is completely discharged.

Method 3: Remove the capacitor from your vehicle and hook it up to any device that uses 12V DC for power. Connect the positive and negative wires of the device to the positive and negative terminals of the capacitor. The capacitor is essentially the battery and once the device shuts off your capacitor is discharged.

Method 4: Disconnect the negative terminal on your vehicles battery and activate the dome light. Once the light goes out, your capacitor is discharged. Be mindful of other batteries in your electrical system. If the light does not go out within a few minutes your vehicle could be receiving power from add-on batteries.

Once the capacitor has been discharged, check the voltage across the terminals of the capacitor using a multi-meter or voltmeter. If the meter reads zero volts or very close to it, the capacitor has been successfully discharged. Make sure to properly recharge the capacitor before connecting it again, please view our article titled “How to Charge a Capacitor” for assistance.

WARNING: Do NOT connect the positive and negative terminals of the capacitor together with standard wire, screwdrivers or wrenches as this will damage the capacitor and could cause bodily harm to the user.

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Written By: Kyle Duffy