Since solars is becoming cheaper, smaller and more flexible. So Pichaya Puttorngul a designer from San Francisco had the idea to use solar panel to recharge, batteries. Just pull the panel out wait for the sun to do its job, roll it back inside the batterie. Great idea great concept. which make me think of the USBcell, but of course with solarcell you get your energy free from the sun.
solarcell the future evolution of USBcell?