Tesla engineer warns against using extension cords at Superchargers

[Zprime29]

I seem to recall reading A2Z responded to that post by the Tesla engineer and said A2Z will claim liability if their cable is shown to be the reason of failure. If the connectors are the same as our free adaptors as built by Tesla, the only concern then is the cable portion over heating. Easily solved with a temp sensor that stops the charge just like the 2 already in the current adaptors. I don't think I'll be buying one, but if gifted one (from A2Z) I would use it without fear.

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[GoodSam]

Just received an email stating “DC | NACS Extension Cord | 6-9 FT (2-3 meters) is available now!”
However, the website still just says coming soon.

https://a2zevshop.com/products/dc-n...gn_EMAIL&Channel=EMAIL&variant=42970429784264

 

[hturnerfamily]

it's amazing how much time we devote to discussing 'extension cables', as, in reality, every cable is an extension cable - there is no 'direct run' to the power plant.

 

[Albern]

Just received an email stating “DC | NACS Extension Cord | 6-9 FT (2-3 meters) is available now!”
However, the website still just says coming soon.

https://a2zevshop.com/products/dc-n...gn_EMAIL&Channel=EMAIL&variant=42970429784264

Yeah I got that e-mail as well. I have an NACS extension cord in my cart but thought I'd wait. The copy on the product page is still showing a variable length of 6' to 9'. I'd hope that I'd be able to back the truck into charging stalls with whatever cord length they have available.

 

[GoodSam]

every cable is an extension cable - there is no 'direct run' to the power plant.

I guess we are just wondering what type of extension cord beyond what Tesla provides could handle the high current required for ~150kW for an extended time.

 

[potato]

it's amazing how much time we devote to discussing 'extension cables', as, in reality, every cable is an extension cable - there is no 'direct run' to the power plant.

True, but when the cable is carrying 100 times more power than a household extension cable, engineering and safety issues become a lot more significant. Probably need to pay attention to what the actual engineers are saying.

 

[hturnerfamily]

what I really mean is that some always cringe at the notion of using any 'extension' cable, just because, well, it's an 'extension' cable. The term does mean by default that it is 'less than' the other cables that already handle the power. My point is that ANY wire, by nature, is AN EXTENSION CABLE.

 

[tls]

My point is that ANY wire, by nature, is AN EXTENSION CABLE.

No, no it's not.

The problem with "extension cords" is that they are not overcurrent protected like the rest of the wiring your home. If an appliance draws only 7A, but plugs into a standard 15A receptacle, there is no reason why that appliance's permanently attached cord can't use 16 gauge wire. However, they make 16 gauge extension cords with 15A connectors on both ends. If you plug an actual 15A load into that and leave it running for any length of time, you're running a serious risk of fire. Sure, you can claim you buy and use only giant thick 12 AWG extension cords. Unfortunately, decades of actuarial data prove that most people don't.

The utility's wire from the power plant to your home is sized to meet their safety standards, which are more permissive than the NEC because it's mostly in free air or buried in the ground (which is a terrific heatsink) and anyway if it overheats it won't burn down anyone's home. The wire in your walls inside your home or business is sized to NEC requirements. Because there were very, very, very few devices that actually plugged into a receptacle and drew the full circuit amperage for any length of time until very recently, extension cords are not. It is characteristic of extension cords (especially those with non-locking plugs) that they use wire that is grossly undersized for the overcurrent protection on the circuit they're plugged in to. Plugging EVSEs in with these cords is a huge risk and I'm frankly surprised it hasn't caused more fires.

All that said, there is a very simple path for A2Z to build a safe extension cord that can handle 250kW. All they have to do is use very large conductors. Expensive and heavy, but entirely safe. If overheating at the connectors is a concern, they can be thermally fused. I have to assume that's what they've done.

But that does not make long term or continuous-load use of other extension cords safe. In the common case, it is not.

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