Initial Charging of a Supercapacitor

Large supercapacitors need a current limiting device in series when they are initially charged, because they store a large amount of energy and have very little internal resistance. Because of these qualities in addition to initial capacitor voltage typically starting from zero volts, the capacitor may act like a short when wiring it in parallel to a battery or power source. Click here for examples of larger capacitors.

It is common to see violent sparks and melting of wires and posts along with damage to power supplies and batteries if there is nothing in line to slow down the initial charge surge current. Although a properly selected current limiting resistor to go in series with the capacitor would work for the initial charge, one may also simply use an incandescent light bulb with an equivalent voltage to the power source. 289-1216-ND is an example bulb for use with 12v sources.

Depending how large your capacitor is and bulb being used, It may take an hour or so to charge the capacitor fully since the current flowing through the capacitor is only that of the bulb current, so make sure you have it wired in a comfortable fashion. You may choose to wire a few bulbs in parallel to increase the capacitor charge current and lower the charging time. The added benefit of charging a capacitor with a light bulb other than simplicity is an indication showing a completed charge by when the light becomes dim or quits illuminating. Once charged, you can unhook the bulb, verify the voltage with a multi-meter and wire the capacitor directly in parallel to the power source.