The power Bank is the absolute necessary , if you are a frequent traveler, it is the main source of charging of electronic gagits like Smartphones and laptop etc on travelling , other main thing is the capacity of Bower Bank .
When you buy a portable power bank , make sure that it can charge the battery a specific device .
Most current power bank have built in USB charge capability , they have a separate cable which one had to carry along with the device .
The other main reason to buy a power bank is the portability factor because you can simply take a charger with you , is a huge plus .