dennis_arduinouser:
What i am trying to do is connect 3 solar panels (5V 250mAh) together to create at max 15V 750mAh.
mAh is a measure of charge used for battery capacity.
I think you mean 5V 0.25A panels.
You can't generate 9 times the power from 3 times the panel.
Either you put them in series and get 15V 0.25A, or in parallel and get 5V 0.75A.
For series you need a diode across each panel capable of 0.25A continuous.
For either setup you need a single diode on the output to prevent back-driving, and that will
need to be 0.75A rated for the parallel case.
Schottky diodes are preferred due to the much lower forward voltages and power dissipation.
[ Those 1N5819's should do ]