I saw this mentioned elsewhere and it has some interesting implications. Let's start with what we know: - Tesla uses "coolant" running through a ribbon between the individual cells, as described in these patent drawings As can be inferred from the drawings this limits the surface area that's in contact with the temperature controlling substance. We also know that extended periods of high current draw cause thermal limit protections to kick in, i.e. the battery cells are not cooled fast enough to dissipate the heat they generate. News from yesterday - The 100 kWh battery pack uses the same cells, but a new module and pack architecture - It's using a new cooling system and electronics, which JB Straubel described the upgrade as a “significant change”. - Elon said the pack architecture is now "quite close to theoretical limit" - Elon Musk described the new P100D pack as “complex” and limited to a quantity of 200 per week. What this may imply A significant change to the cooling system, plus a cell arrangement that's close to the theoretical limit. To get a cell arrangement close to the theoretical limit, the space between the cells needs to be shrunk to a minimum. It logically follows that the tubing between the cells would be the limiting factor in reaching that theoretical packing limit. Thus, the tubing would need to be removed. This leads to the possibility is that for the new 100kWh pack Tesla has switched over to immersion cooling with an electrically inert substance. In home brew PC builds this is done, for example, by submersing all the electronics in a fish tank filled with mineral oil. At an industrial scale its accomplished with better chemicals, such as the 3M Novec product. Immersion cooling/heating should bring two advantages -- increased pack density and increased cooling capacity. The second point might alleviate one of the long-standing criticisms from the performance crowd about "track capability", aka running at high speeds for extended periods of time. It would also bode well for the Model 3. Thoughts?