Tesla engineer warns against using extension cords at Superchargers

[COrocket]

I can definitely see Teslas concern here - on my Model 3 charging at a 150kw station the handle gets extremely hot after more than 10 minutes of charging. I can see why it was mandatory for the 250kw stalls to have liquid cooled cables which actually seem to stay a bit cooler.

I couldn’t imagine how hot an uncooled extension cord would get at a 250kw station hooked up to a 250kw vehicle. Unless the extension has some way of regulating power or is the thickness of a fire hose

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[Tony Burgh]

Heat = I^2*R if I remember correctly (ChemE, not a sparky)
If the conductor is too small and excessive heat generated, it must be removed. Hence water cooling.
If conductor is adequately sized to carry current at lower resistance, less (or little) heat will be generated and little need for auxiliary cooling.

Maybe the extension cord has correct gauge copper. Maybe Tesla went cheap on copper. I hope not aluminum (ductility).