Hello friends! If you are willing to buy powerbank then I will suggest sony power bank. I have been using sony powerbank for 3 years. And to be honest, I haven’t faced any problem. Sony has been the most trusted brand because it’s products hasn’t been a failure till date. The powerbank that I have is amazingly good. First of all, the power back up is amazingly good. Moreover, the charging is fast too. It take approximately 6 to 7 hous for full charge. It gives you warranty too. I forgot the warranty period. But I must say, go for sony. It maybe a bit expensive. But, it is worth the money you pay.
Thank you!