And way back in 2015 the business boasted that its 10,400 mAh power bank (that launched in December of 2013) was its best-selling device globally with 10 million systems sold.

In India the 2 power banks are offering at a discount at the minute, down to INR 800 (20% off) for the 10,000 mAh model and INR 1,400 (30% off) for the 20,000 mAh one. The larger model outputs 18W, the smaller one is restricted to 10W.

The 1 million sales are just for the Redmi-branded systems mind you, in 2015 Xiaomi announced that it has actually sold 10 million Mi power banks that were manufactured in India.

Source

In February in 2015 Xiaomi presented two Redmi-branded power banks, one with 10,000 mAh capability and one with 20,000 mAh. Now the business revealed that it has actually sold 1 million systems in overall of these 2.