How to Recharge a Capacitor

Capacitors are like rechargeable batteries--both are designed to store energy and can be charged and discharged many times. The primary difference between a capacitor and a battery, however, is that charging and discharging a rechargeable battery can take hours, whereas a capacitor is designed to accept and release charge instantaneously. Recharging a capacitor involves sending a current of electricity to the capacitor where internal plates collect and store electrons. You can recharge a capacitor using a simple circuit that will allow you to observe the capacitor being charged and indicate when the charging cycle is complete.

Things You'll Need

  • 9-volt battery
  • 9-volt battery holder
  • 500-ohm resistor
  • Capacitor that has a voltage value of 9 volts or greater
  • Single pole single throw (SPST) switch
  • 5 mm red LED (light emitting diode)
  • 20-gauge hookup wire
  • Resin core solder
  • 15-watt soldering iron
  • 2 alligator clips
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Instructions

    • 1

      Solder one end of a 5-inch length of hookup wire to the positive terminal of the battery holder. Solder the remaining end of the wire to one lead of a 500-ohm resistor.

    • 2

      Solder the remaining lead of the resistor to a 5-inch length of wire. Solder the remaining end of the wire to the anode end (the longer of the two leads) of a red LED. Solder the cathode end (the shorter of the two leads) of the LED to one lead of a SPST switch.

    • 3

      Solder one end of a 5-inch length of wire to the remaining lead of the SPST switch and the other end to an alligator clip.

    • 4

      Solder one end of a 5-inch length of wire to the negative terminal of the battery holder and the other end to a second alligator clip.

    • 5

      Open the switch. Clip the two alligator leads to the two leads of the capacitor. Insert the 9-volt battery into the battery holder.

    • 6

      Close the switch and watch the red LED. The LED will light briefly and then dim before going out completely. The capacitor is now charged to a value of 9 volts and is no longer charging. The LED will only be lit when current is flowing and the capacitor is charging.

    • 7

      Open the SPST switch. Grasp the capacitor by its body with one hand and unclasp the alligator clips with the other hand. Do not touch both leads at the same time. The capacitor is now ready to use.

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