Onesam 10000mAh Fast Carging Power Bank

Its rated input is 5V/2A, so if you use a 5V/1A power adapter to charge it, its actual input current is 1A=1,000mAh. 10,000mAh /1,000mAh=10 hours. If you use a 5V/2A power adapter, it takes 5 hours to fully charge the power bank: 10,000mAh / 2A (2,000mAh) = 5 hours. Same for charging the phone.