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To try it out, I let the Fire battery go down to 69% then plugged the Solio in. After about 20-30 minutes, I checked the power on my Fire again and it was at 63%.
Come to find out, I didn't set the charger correctly and was using the Fire to charge my Solio. Sometimes it's worth the time to read the instructions.
This is what I bought:
Solio® Bolt Solar Charger
Model: S620-AH1RW | Catalog #: 23-1522
Cost: $69.99
You can see it (and order it) here:
http://www.radioshack.com/product/index.jsp?productId=12322646
The Solio folds to half the size shown above.
This could also be used to charge cell phones and other devices using a USB or micro-USB connection..