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A pocket-sized charger for all of your mobile devices

(MoneyWatch) Our modern reliance on smartphones and tablets has created a whole new kind of anxiety: Will the battery last until you get back to a charger? Some people have a charging cable in their car; I sometimes carry a backpack with an integrated battery. For convenience and peace of mind, though, nothing really beats carrying a portable charger with you.

Recently, I had the opportunity to try Fatcat's PowerBar 4200, and it has won me over. The PowerBar is about the size of a deck of cards and weighs just 4 ounces -- it's smaller (but a little thicker) than my iPhone 4, and tucks discreetly in a pocket. It's a 4200mAh battery, good for about two complete smartphone charges.

The PowerBar comes ready to charge right out of the box, pre-charged to about 50 percent capacity, and it can be recharged from any USB port. To fully recharge the PowerBar takes about 4 to 6 hours.

There's a single control on the PowerBar: a button that when pressed, indicates the remaining capacity with a ring of lights. There's no need to "turn on" the charger -- it starts working as soon as you plug it into a gadget.

The PowerBar beats a bag with an integrated battery because it's inherently more portable and versatile. I'm traveling in Italy right now, in fact, and I left my PowerBag at home and brought the PowerBar instead.

The charger costs $80, and there are other capacities available as well: the impossibly thin, 2000 mAh ChargeCard, for $50, and the beefy 9600 mAh PowerBar 9600, for $130, which is also capable of charging an iPad.