This print helps explain the light / solar cell ratio to get these puppies going on their own. My recommendation is 2/3 of rated output in volts vs. power consumed by the light saver circuit. The solar cells will supply their total current output even if their voltage is low see graph below.
As you see the current output of a standard solar cell remains constant regardless of voltage. What I have learned by tuning the supply current to the light saver circuit at C1 you can get about 80-90 % rated voltage with full current output so if you have a 2 X 9 volt @ 85ma you will get 1.1 watts out – our supply current 35ma a .7 watt gain to the good and a .5 watt power consumption to drive the circuit. Hence we achieve over unity of the circuit that is easily replicated by all. As a side note I have hooked up 200 20000mcd 5mm white LEDs to this circuit and saw no degradation on the output in brightness so I can see a world that has, wait for it……. power cells to operate everything.