Advise needed: How to verify a 2.7v "500F" Capacitor


I got a 2.7v 500F super capacitor from Ebay.
Is there a method to test/verify if it is indeed 500F?

Thank you for reading and thanks in advance!!! :slight_smile:

Maybe you could time how fast the capacitor takes to charge to 1.7 volts (63.3% of 2.7 volts) using a small series resistor and use the formula tau(seconds) = R * C

"It is the time required to charge the capacitor, through the resistor, by ? 63.2 percent of the difference between the initial value and final value" (sic)

Yes, charge it through a ~1 ohm resistor to 2.7V, it should take many minutes to get to
2V or more.

If you have a bench power supply with current limit, just see how quickly the voltage rises
at a given current level to measure the capacitance directly C = I / (dV/dt)

These "dual-layer" or ultra-capacitors are almost magic :slight_smile:

But be aware that you should stay well below 2.7 volts which is the absolute max rating for the capacitor,

That's likely the working voltage, not an absolute maximum. (Check any datasheet
carefully though)

The working voltage is the voltage the capacitor should be able to stand in normal
operation. Absolute maximums are stresses that start to cause permanent damage.

You'd never want to take a component upto its abs max if you can help it, you'd
be happy to run a capacitor at or very near its working voltage (except for tantalums).

Since dual-layer caps are designed expressly for energy storage it makes sense
to take them to their design voltage to make most use of your investment.

Using them at rather lower voltages will reduce the leakage current, IIRC.

BTW a 500F 2.7V cap will be storing 1.8kJ, which is a lot of energy, don't leave it
charged up with bare terminals, its easily enough to start a fire if accidentally shorted.