I been very interested in solar stuff lately. I have setup a big solar panel at my balcony since balcony is on the south side in my new home I am still tweaking with it. Right now I have one too small 12v battery. I plan to upgrade ASAP. I will use it for charging my laptop, mobile, and hopefully also lighting(leds only) in my home in winter. Will be interesting to see how well this work in winter since I live in north european :/ Anyway back to topic:

Do you have any plan to add a tiny NIMH/Litium battery to your solar in next iteration of your project?

I think it could be an idea. Why? Because when you phone is fully charged you can use sun to charge the extra battery. Also it make charging of the phone more stable if there is a "backup battery"?

I don't know how much extra electric needed to make that work. I realize the costs will get higher and the solar heavier but....