You may have found that after a while your Mi Band won't charge any more. I had this happen with the Mi Band 1S.

Many people have found this easy repair method to work for the Mi Band 1S and for other versions of the Mi Band.

This simple fix might work for other brands of fitness bands as well. 

Watch the video below and you'll see how I fix a Mi Band that won't charge by simply scraping the contacts with the tip of a regular old screwdriver to clean off any light corrosion built up upon the contacts that is preventing the Mi Band from charging. 

A lot of people have fixed their Mi Bands by following the simple tip in this video.