There's this
video where Gruber opens up a pack, puts some of the modules on a bench and snips one of the fuse wires to "repair" the module by disconnecting a bad cell.
I imagine there's a corner in Fremont or sparks or a subcontracted shop down the street where they break down returned packs and classify modules by chemistry and wear levels.
The workflow would be:
1) standardize on a pack (or two?) that satisfy as many repair cases as possible; refurbished modules will go into these packs
2) identify which cells / chemistry / modules *never* get repaired vs those that can be put back into service
3) build a disassembly line where returned packs get broken down and their components recycled or put into the testing / refurbishing chain
4) for every part that's a candidate to refurbish, build tooling for testing / evaluating / validating the modules
5) modules get sorted by remaining capacity and chemistry (presumably the BMS expects all the cells in all the modules to be roughly comparable, and has settings to tune distinct profiles for a given chemistry)
6) evaluate incoming demand for refurbished packs and match up requested capacity with available module supplies to make packs that are roughly the same capacity as the one that's being replaced.