The mAh (milliampere per hour) capacity rating refers to the available storage capacity for a battery. A higher number means that the battery can store more energy and has a longer battery life when charging a device. So for example, an iPhone 13 Pro Max’s battery is rated at 4,352 mAh. This means that a power bank with 10,000 mAh can fully recharge that phone a little over twice before running out of power.