I’ve designed a battery testing board (the initial version is discharge only) specifically for testing the recycle 18650s for my electric motorcycle conversion project. The aim is to have a “cheap and cheerful” board that is accurate enough to be useful. I’m calling this board the jCharge D8 (d for discharge, and 8 for 8 channels).
You can see all of the stats and even control it from a web and app based interface. You can monitor the state, save the discharge graph/capacity and calculate an approximate internal resistance. This will make testing the 1000+ battery cells much more practical and efficient.