Link: http://blog.testfreaks.com/review/review-of-powerskin-gaming-case-for-nintendo-3ds/

Quote:
" The Nintendo 3DS is truly a marvel and step forward in gaming, it’s a great little portable gaming console but it’s battery life is just horrible. Carrying the power cord with you isn’t always an option and sometime you might not have anywhere to plug it in at. Today for review I’ve  got the PowerSkin Gaming Case for Nintendo 3DS which is an external battery and case that promises to offer more than double the battery life for your 3DS. Does it work? Yes. Is it perfect? Not really. "