Guys nowadays there have been a LAHAR among people to buy a power bank.definitely in smart phone world we need a power bank.but guys before you buy a power bank think once what you need .
I mean calculate your requirement.suppose you own two smart phones which battery is of 2800 mah each.it means you need 5600 mah holder and supplier power bank.
Now search the costing according to mah ratio price.you please visit at least five online shopping website.now check your budget and choose one.i strongly recommend go for mi power bank.