Best power banks: The top portable chargers for devices

Don't leave home without one.

Anyone who uses a smartphone knows the importance of carrying a backup battery pack. But try searching for one on Amazon, say, and you're likely to feel overwhelmed by the vast number of options. Besides the various charging specs, ports, and even cables you have to consider, there are a ton of competing brands. How are you supposed to know which ones actually live up to their promise?