I did have some luck charging the 12v battery today, as the 6 cells raised it from 11v back to 12 in about 4 hours. I'm sure that it would charge a single rechargeable 9, or 6 volt battery just fine. The thing is to not let the battery drain down to far, so that it will charge back up easily.
Hitman mentioned that his 6 solar cells are 3 volts each, and he is charging a 6 volt battery to run all those 10 2watt lights. Mine are mostly 2volts, and 30 mA, but I have one cell that is a 4.3 volts, 30ma, all are in placed in series.
I need to get at least 2 more of those cells, to reach 18 volts, as I can get only 14 volts in full sun, but only 30mAs. I can run my Exciter even on 3/4 volt, but it needs some more amps to work well, a couple more cells placed in parallel would give me enough current, also.
Some of the garden lights are real junk, but the solar cells themselves are nice, and they don't wear out. Since it's all free I can't complain.

For those that have not seen Hitmans video, (he has several), here is the link:
SJT Powering 10 lights and charging a laptop - YouTube

This is my latest video, I'm still working on improving the Exciter circuit.
It is the same 12 volt circuit that the solar cells will run.
Simple Jt Exciter No, 2 - lighting CFL bulbs - YouTube