Step 1: Materials needed
1. Battery cases; any battery that is normally 1.5 volts (NiMH cells tend to be 1.2, which is close enough) should charge off this array. Do whatever is most practical for your needs; AAA cells, AA cells, C cells, or D cells, to name a few that would work.
2. Batteries; I used NiMH cells because they're the lowest maintenance. They don't have to be discharged completely, like NiCd (Nickel Cadmium) cells, and they're widely available. You would probably need to modify the circuit if you wanted to charge another type of cell.
3. Solar array; I used three one volt crystalline cells fastened together into one big three volt array. I'm not sure if the three volt amorphous cells from portable calculators would work; You could try.
4. fasteners; I had a problem with the solar array falling apart, as it was made from three separate cells; I used two metal rails and some epoxy to keep them together. I also used foam tape later.