1. The looks of the power bank
Since you will be roaming around with this device, it is imperative that it looks good. Till about a year ago, the power banks that we used to get were ugly and bulky but that has changed now. Just look at the wide variety of colours offered by ASUS for it’s power bank. You can get these colours from different manufactures too.
For example, the powerbank by ASUS which is called the ZenPower
2.Convenient To Carry
It is one thing to be compact in size and totally another to be handy to carry around. Make sure you don’t get fooled by size alone.
3. How much is the capacity…and how much times can i charge my phone ??..
The most important thing about the power bank is that how much output can you get from them. There are a host of power banks in the market now, which offer over 10,000mAh and that’s decent. You can fully charge an iPhone 6 for more than 3 times, iPhone 6 Plus for more than 2 times and a Samsung galaxy s6/s6 edge almost 4 times
4. Quality and Durability
Since you trust your phone (or more specifically your phone battery) with the power bank, ensure that it is of good quality. There are some power banks which combine multiple high-capacity batteries. This increases the durability of the power bank and ensures better quality .