I have 2 identical PowerStor Series XB supercaps connected in series. Voltage rating of each is 2.5V. In series their capacitance is cut in half but the voltage drop over both of them should be double. So that's why I connected it to a 5V pin on a computer PSU for charging.
After about a minute I disconnected everything and found that the top cap had a voltage of 2.6V while the bottom cap had 0.8V. How could this happen? and why?