OK my panel is rated 5V 130mA.
Let's say you want to charge a battery and you need 4.2V and 130mA, who cares?
I'm not using the solar to charge the 78mm battery but i'm using it to charge the PCC battery instead, it will keep it fully charged at full times.
There is another problem, since the pcc is not lighted directly at all times the panel has a lower output voltage on low lighting conditions, i used a buck boost converter and when the light is low i still get 5V out with a lower amperage off course.
5V is convenient because i'm feeding the usb input on the pcc's internal buck converter which is controlled by a PIC microcontroller. I'm avoiding charging the pcc's battery directly because that will confuse the microcontroller (the battery measurement).
It's a loss of some energy at low lighting conditions but it works. When it's fully sunny it works OK.
I'm surprised at the output of the solar panel for such a small size. It does make me wonder how cost effective it really is, panel versus conventional charging costs. I guess things have come a little further than I thought, although without enough sunlight, you're still out of business. It's been cloudy here for the last two days, so by now I'd be out of batteries, LOL.