Those AA alkaline- and lithium-powered phone chargers are a totally handy (and relatively inexpensive) thing to throw into a bag and carry around in the event -- the incredibly likely event -- that you end up running your set dry at one time or another, but there's a small problem: those AAs don't go very far. Generally speaking, you'll get a couple charges out of a set of batteries, which makes them environmentally dubious at best and less convenient than you'd like them to be. That's where KFE Japan's new solution comes in: same concept, but the batteries are zinc-air instead of alkaline or lithium -- the same tried and true chemistry used by hearing aid batteries -- whereby you pop a lid open on the charger to expose the batteries to air, which starts the juice flowing. The advantage is that you're looking at about 20 charges before the thing's depleted, and when you're there, you'll be able to send it back into KFE to be recharged. The chargers will run 3,000 yen (about $31) when they launch in March. [Warning: subscription required]