I have a 2000F super capacitor. I don't know how old it is etc, so I slowly charged it to 2.7V (its rating) with 1A current (did 500mA for 0 to 1V).
Using the time formula with 1V I got something along 1950F capacity (32.5 min @ 1A for 1V to 2V). However when I hooked it up to a rapid discharge circuit (spot welder), I am only getting 15A out of it. The rating claims 0.5 mOhm ESR.
I can leave these for a long while connected to a resistor to discharge them, and maybe measure ESR with de5000 (is this appropriate? scared I will fry meter. I should have measured ESR before I charged em up first time.. but it will be slowly decaying on the 10 ohm load for a long time).. but I am wondering for stuff thats been on the shelf for a long time is there any kind of restoration procedure.. like hooking it up to rapid charge or something (not 'trickle' charging it). Would a few cycles help... or am I just wasting my time? Never worked with supercapacitors before. I thought maybe like 50A charge current might 'electrolytically clean' something inside.
I thought to short it out on a clamp meter or something but I need to hook up some wiring (kind of scared its going to explode on me). My wiring is OK I measured it to be around 900mOhms per cable, less then 3mOhm total. Only other thing that comes to mind is terminal corrosion on the cap, its aluminum...
Is it possible to see such a huge ESR increase while measuring capacitance ok? Or is that capacitance measurement method flawed? Thought I was good when I got the high farad number from the charge time test. For that I hooked up a multimeter to a power supply, current limit to 1A and waiting for voltage to rise to 2.5V with a stopwatch.