It's not clear, what kind of battery you are trying to charge?
There point is, If there is a big difference between solar panel output voltage and maximum
voltage (fully charged) of the battery, you can built more "efficient" charger and get more current.
Circuitry, shown on a link, is "linear" voltage regulator, it's mean doesn't matter what surplus voltage on the input, it will be "lost". I'd suggest to build a switching regulator, DC/DC converter.
or something like that).
Solar panel output = 10 V in broad day light;
Fully charged battery = 5 V.
Input current = 70 mA.
Output current = Power(out) / V(bat.) = Power(in) * K(ef.) / V(bat).
where K(ef) is efficiency of switching regulator, 93.6 % (5 V)
I(Output current) = I(in) * V(in) * K / V(bat.) = 70 * 10 * 0.9 / 5.0 = 130 mA.