I am concerned about an ultracapacitor (2.7v, 3000F) that I received today. I set my power supply to 2.5v with a current limit of 1A, then connected a diode to the positive lead such that current would only flow to charge the capacitor. I then connected the end of the diode to the positive terminal of the capacitor and ground from my PSU to the negative terminal of the capacitor.
However, only about 2mA was drawn. The diode I am using has a low diode drop (~0.3v), so I figured it should still charge the capacitor to around 2.2v. I then adjusted the voltage such that there would be 2.7v across the capacitor (~3.0v from the PSU), and it slightly increased the current drawn, but the change is negligible.
I can't see anything wrong with this charging setup, so is it likely that the capacitor is bad? Perhaps the polarity indicated on the capacitor is incorrect? Is reverse voltage harmful to ultracapacitors, meaning that I shouldn't check? Thanks.