The other week we talked about how a tiny USB hub, when plugged into a computer and matched with the right set of cables, can become a de facto travel power strip.
That works well enough once you've settled into your hotel room. It's less useful when you're on the road, away from outlets, and trying to conserve precious battery power. During those times you want to charge your USB-powered peripherals without draining your laptop. You want a separate battery. ]]>