We bought one at the phila airport. Just as AngiTN said, we have a bunch of other chargers, but this one is so tiny and can be swapped when dead. This last trip, between the whole family, we had 4 little fans and 4 phones. That fuel rod was charging something all the time. When ever I passed a swap location, I got a new one. It's small enough we can plug it into one of the fans for the baby strollers and using a velcro strip, hook it on somewhere. We did bring along a longer charging cord to use.
The only issue I had (aside from my own stupidity when I first tried to exchange it), was the location near dumbo, the screen said THANK YOU. No way that I could see to make the screen change so I could swap one.
I do wish there was some indicator on how much power is left in it, which is why I always swapped them when I had the chance.