Opteka BP-SC4000 Solar Powered 4000mAh Backup Battery Charger + 10 Charging Tips for $19.99 shipped.  Here is a screenshot for your reference.  It can fully charge mobile devices using solor or USB power.  It also has a high capacity 4000mAh built-in lithium-polymer battery, and includes 10 charging tips to work with a variety of devices [...]