We all have smart phones now days and you know internet consumes more battery.
Power Banks are very time saving. I am a marketing guy.
I always use to travel here and there. I have no time to charge my mobile phone. I brought a power bank some days before & I am very happy to use this. I have a power bank of 10000 MaH. When I reach hotel I charge my mobile phone as well as power bank. I can easily carry this.