I was originally looking for something allowing me to make a power supply for my USB-C only laptop to build a (large and cheap) power bank from some 18650 cells

I was originally looking for something allowing me to make a power supply for my USB-C only laptop to build a (large and cheap) power bank from some 18650 cells I had lying around. I understand that communication with the voltage converter would likely be so complicated they should be integrated with each other, then integrating all the other battery management stuff wouldn't be so far either. Admittedly it has been a few years ago, but the last time I looked nothing like this was available.