Mac Mini M1 uses 12v PSU and 10x2 2.0mm pitch connector. 

Layout can be found here: https://www.ifixit.com/Document/qMotFqYMafDIeWWb/MacMini2018_DC_Connector.pdf

I used a regular PCB connector and thick enough wire in silicone insulation

Mac Mini M2 uses a different 2 pole screw terminal. Much better for DIY, unexpected from Apple!