Selecting a power bank depends on your requirements and needs. There is a whole general criterion to consider when choosing to buy a suitable power bank:
a) Capacity
For example, if your phone’s capacity is 1500 mAh, a power bank with a capacity of 2200 mAh can charge your phone fully once. But if your phone battery’s capacity is 3000 mAh, then the same power bank won’t charge your phone fully because the phone’s capacity is higher. So, if you are looking for a power bank that can charge your phone several times a day, then look for the power banks with high capacities.
b) Output ports on the power bank
Each power output will charge one device, so if you need to charge more than one device together, you will need to get a power bank with two or more outputs.
c) Output specification for your devices
1A-1.5A output is for smartphones, whereas the 1.5A-2.0A output is for tablets.