You can use a power bank with more than 20,000mAh capacity to charge various devices multiple times. The maximum size you can bring on an airplane is 27,000mAh, which allows you to fully charge your smartphone 5 times. You can fully charge tablets 2 to 3 times. Want to charge a laptop as well? Your power bank needs a USB-C port with at least 45W power. To be sure how often you can charge, compare the battery capacity of your device to the capacity of your power bank.