As I stated earlier in my review post, the 10400 mAh capacity Mi Power Bank charges Xiaomi Mi3 approximately 2.5 times, Apple iPhone 4 approximately 5 times, Apple iPhone 5S approximately 4 times, Samsung Galaxy S3 around 3 to 3.5 times, Samsung Galaxy S5 around 3 times, Apple iPad around 1.5 times, Xiaomi Redmi 1S approximately 3.5 to 4 times and so on. For me the rule of the thumb is around 8000 mAh - It do claims to be of 10400 mAh but that doesn't means that you get full power. A lot of power is used for conversion and in form of heat, but still in the end you can charge a good number of devices.
Mi Power Bank 5200 mAh
I haven't used the 5200 mAh variant of Mi Power Bank but according to the company, it can charge Xiaomi Mi3 one time, Apple iPhone 5S two times etc. It takes 3 hours to charge 100 percent when using 2A charger and upto 6 hours when using 1A charger.