We here at Engadget are in favor of hitting the books from time to time, but we can't have lame gadget-less backpacks hurting our true techie rep. That's why we're excited to see Ralph Lauren outing its first solar-equipped knapsack as part of its RLX sports line. Four solar cells around back harness the sun's power to generate 3.45 watts -- completely juicing up an iPhone in a purported two-to-three hours, assuming you've got "proper sun
