Most people buy power banks online, so they have be sure about what they purchase. Here are some tips on power banks-
First of all you have to know about some brands which produce great power banks like MI, Ambrane, etc.
Then you have to select the capacity of the bank, like minimum it has to be minimum 10, 000 mAh to as your requirement.
After that compare the price of top brand with that capacity of power bank and buy the power bank with a brand name with lowest price and higher capacity.
Then buy power bank and also check the warranty of it.
After buying it, first read the instructions how to use it i.e. Every power bank has its different way to charge and use it.
And prefer the usage of the same USB wire which is given by the company with power bank.
Thank you.