mi 20000 mah

Hi, I just bought a mi 20000 mAh power bank. Currently I only have a single charger - my Moto G 2nd gen charger rated at 5 V/550 mAh output, which iobviously is ridiculously slow to charge this power bank. The product manual/specifications suggest - 9 V/2 A or 12 V/1.5 A charger for fast...