Should I get a solar panel case for my iPhone?

I still have my iPhone 4s, the best iphone in my opinion, and I really love it, just sometimes ill go to bed with 5% of battery left and it's kind of annoying. I'm thinking of getting this one:

http://www.amazon.com/...005HMCNO2/

or should i get a cheapy iphone backup from ebay?

http://www.ebay.com/...0895348492

I'm curious on the solar panel device because i found a old solar panel and was curious if you can charge an iPhone with one, finding this was cool, and plan on going to California for 1 Month and it could be useful if their isn't a power outlet. ( Yes i know it would take 10 hour to charge the battery fully )

Is would say instead of getting the solar panel ( which are poorly made anyway) just charge your phone while you sleep next to your bed. These backs are bad and I don't recommend it!