How to discharge a capacitor

Do you know how to discharge a capacitor? If not, don’t worry!

This is the ultimate guide to discharging capacitors. We will explain the different methods that you can use to discharge a capacitor safely step-by-step.

How to discharge a capacitor

What is a capacitor and what does it do?

A capacitor is a device used to store electrical energy. It does this by creating an electric field between two plates. When voltage is applied, it charges the capacitor.

The capacitance of a capacitor is a measure of the amount of charge it can store, and is usually specified in farads.

Capacitors act like the rechargeable batteries of AC circuits. They perform their function of storing electrical energy and transferring it to other parts of the circuit.


Why do capacitors need to be discharged?

As we said, capacitors store electricity and can give you a nasty shock if you touch them while they’re still charged. That’s why it’s important to discharge them before touching them.

They can keep the current in themselves for up to a few minutes after the current stops flowing through the circuit. That’s why we always have to discharge them before working.

Why do capacitors need to be discharged

Which capacitors are considered safe?

There is no answer to this question. Any capacitor can hurt you more or less. But capacitors up to 50 volts cannot cause current to flow through the body and cause death.

Capacitors that are smaller than 50V usually cause stinging, weak electrical shock, and slight tingling of the fingers. We consider them relatively safe.

Remember, only empty capacitors are 100% safe.

Safety steps before discharge a capacitor

  1. Disconnect the capacitor from the electrical source

Before we can explain how to discharge a capacitor, you must first cut off the power supply to it.

-A device located in the house simply unplugs from the wall outlet.

-If it is in the car, then you have to disconnect the cables from the car battery that are connected to the + and – terminals.

-A device that is connected to its external battery or has its own power source should be turned off and the power line should be disabled.

electrical source
  1. Wear protective gear

There are a few reasons why it’s important to have protective gears when discharging capacitors.

One reason is that capacitors can store a lot of energy, and when they start discharging, they can eject sparks.

Another reason is that capacitors can make electric shocks when their metal contacts come in contact with the skin.

Most people find it funny to have protective gears, but when they get injured by electric shock or sparks they change their minds.

Protective gear, such as goggles and gloves, can help protect you from these risks.

Protective gear
  1. Safe environment

Make sure there are no flammable materials or devices around you when you empty the capacitor.

Discharging with a Screwdriver

  1. Turn off the power supply

When working with capacitors, it is important to always turn off the power supply before discharging them. This will help prevent injuries and accidents. Capacitors can store a large amount of energy.

Turn off the power supply
  1. Locate the capacitor on the electronic device

Generally, capacitors are located near the power supply, as they are responsible for storing energy and regulating current flow. If you have difficulty finding the capacitor, consult a schematic diagram or your device’s owner’s manual.

Locate the capacitor
  1. Take a capacitor and find the positive and negative terminals

Grab the condenser for the body without touching the feet (terminals) using gloves. The metal contacts represent the positive  and negative connectors for the electrical circuit.

capacitor positive and negative terminals
  1. Use an insulated screwdriver to connect terminals together

When discharging a capacitor, it’s important to use an insulated screwdriver to avoid contact with the live contacts.

First, identify the positive and negative terminals of the capacitor. Then, connect the positive and negative terminal using an insulated screwdriver. Hold the screwdriver in place for a few seconds until the capacitor discharges.

Capacitor discharge can cause a spark or a small sound flash. This is normal and should not scare you.

Discharging capacitor with a screwdriver
  1.  Remove the screwdriver from the capacitor terminals

You can repeat the previous step to make sure it is empty. Then, just detach the screwdriver from the terminals.

Remove the screwdriver
  1. Connect multimeter to measure voltage

Use a multimeter to measure capacitor voltage. Connect the probes and metal contacts. The order of connection (polarity) is not important.

If you get a value higher than zero, the capacitor is not completely discharged and the procedure should be repeated several times to ensure that the capacitor is fully discharged.

Connect multimeter to measure voltage

Discharging with a pen tool

To discharge a capacitor, you can use a pen tool to short out the two plates. This will create a spark that will quickly dissipate the charge. Be sure to use caution when discharging capacitors, as they can store a significant amount of energy.

This is the easiest and fastest way. The discharging tool contains a high-value resistor that allows the current to be discharged quickly.

Discharging tool

Discharging With Light Bulb

The third way is to use a light bulb. If you don’t have a discharge tool or a screwdriver at home, you can certainly use a light bulb.

  1. You need to take one light bulb that is connected to a bulb socket with wires.
  2. Connect one wire to the positive terminal and the other wire to the negative terminal. The bulb will start to light up and when it goes out it means that the capacitor is empty.

The advantage of the bulb over other tools is that it has a light pointer that shows when the capacitor is full empty.

Discharge the capacitor with the light bulb

Discharging with Resistor

  1. Make sure the capacitor is unplugged and has no power running to it.
  2. Connect the high-value resistor across the terminals of the capacitor.
  3. Touch the ends of the resistor to the metal contacts of the capacitor.
  4. Wait until the capacitor is discharged.
  5. Disconnect the resistor from the capacitor.
  6. Plugin the capacitor and turn it on.

The resistor prevents a large current surge from flowing through the capacitor, which could damage it. By slowly discharging the capacitor using a resistor, you can avoid any potential problems.

Discharge capacitor using resistor


In this video, we have explained methods of how to discharge a capacitor.


How do you discharge a capacitor using a multimeter?

The multimeter is not used to discharge the capacitor but is used to check that the capacitor has discharged. 

Will a capacitor discharge on its own?

Yes, it’s possible. The capacitor is theoretically discharged gradually over time. For a long time, a non-used capacitor should be empty. Depending on the size and capacity, the larger capacitor will take longer to discharge.

We can’t know for sure if it’s empty until we check with a multimeter.

How dangerous is a capacitor?

A capacitor is a device used to store an electric charge. While they are not typically dangerous, they can be if they are mishandled or if they malfunction.

If a capacitor malfunctions, it can release a large amount of voltage very quickly, which can cause burns or even explosions. For this reason, it is important to always handle capacitors with care and to only use them as directed.

Is it safe to discharge a capacitor with a screwdriver?

If you follow these steps, you will safely discharge the capacitor.

Does discharging a capacitor damage or ruin it?

When you use a suitable tool correctly, you will not damage the capacitor.

What is the fastest way to discharge a capacitor?

There are a few different ways that you can do it. One way is to use a resistor, which will discharge the capacitor more slowly. Another way is to use a discharge pen tool, which will discharge the capacitor more quickly. 

What tool is used to discharge a capacitor?

There are various tools, but the best ones are insulated screwdrivers, discharge pen tools, light bulbs, and resistors.

Can a capacitor kill you?

No, the capacitor is not deadly, but it can hurt you if you unsafely try to empty it.

Tips for avoiding accidents while working with capacitors 

Capacitors can be dangerous if not handled properly. Here are a few tips to help avoid accidents:

  1. Always wear gloves when handling capacitors. This will help protect your hands from any electrical shocks.
  2. Make sure the capacitor is discharged before working with it. You can do this by shorting the two metal contacts of the capacitor together.
  3. Be careful when transporting capacitors. They can be very heavy and can easily fall off of a table or bench.
  4. Never exceed the maximum voltage rating of a capacitor. Doing so can result in an electrical explosion.


We hope you have successfully learned how to discharge a capacitor. And always remember to unplug the device before working on it!