The small energy giant Terratec P50 Pocket packs a capacity of 5,000 mAh into a compact case measuring 93.5 x 64 mm. Thanks to high-density technology, the power bank is barely larger than a credit card and only 13 mm thick. It is so discreet that it hardly stands out in a hand or shirt pocket. Through its USB or USB Type-C output, it provides power to smartphones and other devices on the go, while protecting them from excessive charging and discharging.