This power bank battery backup is so good. But the main problem comes with the data cable provided with it.
Although it looks funny that how a data cable can ruin the performance of whole of power bank but its true because different data cables have different rate of data and charging speed and I would say the data cable provided with this power bank is so slow that the power bank charger so slowly and the phone also charge so slow.
I would recommend that if you are buying this product then you may also want a custom usb cable to charge power bank and phone.
But very unsatisfied with the provided data cable with it.