I found 2.4V zener diodes. 2.4 and 2.7 seems to be common. Is this a solution?
EDIT: I am confused. I thought about this and I think this doesn't make any sense, I did not come up with a good idea. I mean when you substitute the volt detector with a 2.4V zener diode there will always be a constant voltage through the zener diode. I think we need some kind of detector that will sense the volatage change when more than 2.4V is on the caps.
EDIT: I guess using this volt detector (2.5V) solves the problem.
So I think I will do it this way:
The first resistor (at the caps) is necessary to load the caps with 4A at 2.5V (ohm's law: 2.5V = 4A * 0.625 ohm), the second one is for discharging. You think this will be ok?