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).

 

[BeeKind]

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).

Water cooled aluminum alloy, ever wonder why they're so thick?

Copper has the problem of walking away in the night.

 

[Tony Burgh]

Water cooled aluminum alloy, ever wonder why they're so thick?

Copper has the problem of walking away in the night.

If I get a properly sized extension cord, you can bet it will walk away with me. Every time.

 

[Maquis]

Water cooled aluminum alloy, ever wonder why they're so thick?

Copper has the problem of walking away in the night.

Meth heads wont know it isn’t copper until it’s too late.

 

[BeeKind]

Meth heads wont know it isn’t copper until it’s too late.

Actual thefts have been low. Vandalism on the other hand has been on and off, high in various regions.

 

[RickKeen]

The correct gauge copper can handle the current. Its just expensive.
Nobody going to buy a $1000 extension cord.

 

[husky10101]

Their extension chord is 16 feet, you don't need a 16 foot chord to adapt to a Tesla supercharger. Only a few feet will do.

 

[Heliian]

Extension cords create heat, losses and multiple points of failure.

Literally any extension cord.

This is not rocket appliance.

 

[BeeKind]

Their extension chord is 16 feet, you don't need a 16 foot chord to adapt to a Tesla supercharger. Only a few feet will do.

NEC doesn't rate extension cords for 500A and isn't feasible. You're talking 500 MCM wiring or larger if aluminum.

I really don't think people are appreciating the wattages they're talking about here. There's nothing out there in consumer world built to do this, nothing certified, nothing that will be certified.

You know why your EVSE is limited to 19'? It's not a technical limitation, it's code being extra cautious. You really think they're going to let you run around plugging in 16' 750 MCM? How is that being cooled? What is it rated to run at? You're going to have 170F cables?

What is possible in theory and what is practical are often planets apart. Extensions are feasible and are in Europe for L2 AC charging. Here our standards is different, but we're not talking L2 now either. Extension cables to carry DCFC loads will probably always be a nonstarter.

 

[TheBigBezo]

I'd be curious if state of charge would hook one of these up, I think they own their own DC chargers. Would be a very interesting test to evaluate heat over a half hour. I wouldn't want to plug it into a vehicle though, for risk reasons, but the equipment to bench test is also probably expensive. A possible solution is instead of making it thicker, use some form of air cooling heat sinks like rings along the cord with an insulated grab handle.

 

[Kev12345]

sounds like a Tesla problem. hopefully they start replacing all the V3's with longer cord V4's so this doesn't become an issue.

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