RIN67630:
I bought a couple of 4F 5,5V supercaps.
They had about 2-3V charge.
I wanted to charge them with a 50mA current limited 5V regulated power supply.
I was surprised to find them going immediately to 5V and have only ~20mA running through them.
Is that OK?
T = CV/I = 4F(2.5V)/20mA = 500 seconds
So, it appears something is amiss.
- Could be your "~20mA" measurement -- where did you get that from?
- Are you sure the power supply was in constant current mode? This could happen if the supply allowed a lot more current to flow.
- Did you measure the voltage directly across the supercap?
- Also, if you have a scope, it would be more telling to see a trace, rather than point test with a multimeter.
- What happens if you discharge the cap through a resistor? Use T=RC to predict a discharge time and experiment.
- Then, with the cap fully discharged, how does it behave when you connect the current limited supply?