Archive labelled for the Xiaomi Mi 1S, 505 KB in 7z format; the name does not state what kind of documents it holds. Given its size and the neighbouring files in this collection, it most likely contains service material such as schematics, but open it to confirm. Extract with 7-Zip or WinRAR. If it contains circuit diagrams, use them to trace power rails, charging paths and connector pinouts. The Mi 1S is a refreshed Mi 1, so verify the model and board revision before relying on it.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @esquematicosdecelulares. Enginerys does not host this file.
How to open a .7z file
High-ratio compressed archive, often used for large BIOS collections.