Recently I tore down a discarded barcode scanner, and found a Maxwell PC10 supercapacitor inside. I wanted to check if it a good part. A 10 farads is way too much to expect a multimeter or LCR meter to test.
In the device, this may have been installed to provide a constant voltage under rapid current draw. Instead of increasing the size of the battery powering the unit to cover peak demands, they use a supercapacitor to provide the burst demand. There are multiple reasons a supercapacitor would be better than an electrolytic capacitor in such a situation, check out Battery University to learn why.
Fortunately, I located a detailed specification sheet for the PC10. Between detailed reading of the pdf and research elsewhere, I determined I would charge up the capacitor and compare the charge curve against the specs.
Evidently most supercapacitors are to be charged to 2.5V, 2.7 at most. Here is the specification for the PC10. For testing, the suggested current is 1A, even though the capacitor can handle up to 14A peak demand.
I did some preliminary calculations based on the following guidelines from a supercapacitor spec sheet. It told me using my setup it would take roughly 2 minutes to charge from zero to 99%.
I hooked USB-C device which logs voltage and current over time at 1 second intervals for upload to PC (It's a TC66C). My load was a 1.5 ohm resistor of appropriate wattage. The total circuit resistance was 1.6 ohms including the internal resistance spec of the supercapacitor. Your equipment might vary. A stopwatch and two multimeters might be OK!
Here is my resultant curves. The time that it takes to charge did match up with the formulas above. It doesn't provide a exact capacitance value, but I suppose you could use the results to make a reverse calculation. I was just happy to confirm it works as designed and achieved something that matches up with the formula.
Note that the initial peak current was not captured, because the current during the first interval is averaged.
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