This is a neat idea with potential. It works great if you have supplemental 12v power to fully charge the reserve battery. But if you intend to use it to charge an iPhone each day using only sunlight, there is not enough regenerative power available via solar to keep a iPhone alive for more than 2 days. But all in all, a cool idea and works great if you have an additional (Larger) solar panel, or access to 12v supplemental power.
Pros: Fun, cool factor,
Cons: Long charge times
This review was written in the old system and had content requirements that are different than reviews written today.