mAh stands for milliampere hours, which is a measure of electrical charge that affects the output and performance of your portable device and charger. It is a unit of measurement used to describe the amount of battery capacity required to provide the flow of one milliampere of electrical current for one hour. The more mAh a power bank has, the more power it has to keep charging your mobile devices. When deciding how much mAh you need in a power bank, you should consider your usage and time. A power bank with a capacity of about 7,000 mAh can be used to charge multiple small gadgets, including headphones, as well as your phone. A 10,000 mAh power bank should be able to charge a smartphone up to three times, and a 20,000 mAh power bank more than six times.