I have seen a similar product which can either be charged with household current or by an optional solar panel.

http://eatonpowerpacks.com/powerpack450.html

I have not tested this product; I'm reading positive things about it.

Jeanette Isabelle
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I'm not sure whose twisted idea it was to put hundreds of adolescents in underfunded schools run by people whose dreams were crushed years ago, but I admire the sadism. -- Wednesday Adams, Wednesday