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Hi, I just purchased a 2022 SE MINI Cooper, and the car comes with a charging cable with a built-in surge protector. The closest socket from my parking space is 50 feet away, and is a "Nema 5-20" (20 amps, 120 V, 1-phase). When I plug the charging cable directly into this socket, the surge protector "Power" led turns on, indicating all is well. But, when I plug in a 50-ft extension cord (12-gauge wire) into the socket then the charging cable into this extension cord, then the surge protector reads "Fault". This fault happens before I've even plugged the charging cable into the car.

So, is my extension cord simply not beefy enough, do I need a 10-gauge extension cord, with the special Nema 5-20 plug, rated for 20 amps?
Or, should I not use an extension cord at all?

Thank you for your insights and help.
 

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Hi, I just purchased a 2022 SE MINI Cooper, and the car comes with a charging cable with a built-in surge protector. The closest socket from my parking space is 50 feet away, and is a "Nema 5-20" (20 amps, 120 V, 1-phase). When I plug the charging cable directly into this socket, the surge protector "Power" led turns on, indicating all is well. But, when I plug in a 50-ft extension cord (12-gauge wire) into the socket then the charging cable into this extension cord, then the surge protector reads "Fault". This fault happens before I've even plugged the charging cable into the car.

So, is my extension cord simply not beefy enough, do I need a 10-gauge extension cord, with the special Nema 5-20 plug, rated for 20 amps?
Or, should I not use an extension cord at all?

Thank you for your insights and help.
First, check with an electrician. Technically, you should not use an extension cord. Most Level 1 "chargers" documentation advise against it. But if you must, try a "generator cord" that should match both your connector and the gauge expected for the device. You want to avoid overheating the cable or connectors involved and/or popping your circuit breaker.
 

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I guess it's the GFCI within the NEMA 5-20 outlet, see this:

Can an extension cord cause GFCI to trip?
Excessive lengths of temporary wiring or long extension cords can cause ground fault leakage current to flow by captive and inductive coupling. The combined leakage current can exceed 5 ma, causing the GFCI to trip.
Nuisance Tripping | Central Montana Electric Power Cooperative (cmepc.org)

and BTW, 12AWG wire is enough for 20A
 

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I guess it's the GFCI within the NEMA 5-20 outlet, see this:

Can an extension cord cause GFCI to trip?
Excessive lengths of temporary wiring or long extension cords can cause ground fault leakage current to flow by captive and inductive coupling. The combined leakage current can exceed 5 ma, causing the GFCI to trip.
Nuisance Tripping | Central Montana Electric Power Cooperative (cmepc.org)

and BTW, 12AWG wire is enough for 20A
True, but I think they meant to say "capacitive coupling" instead of "captive". Proofreading is in short supply these days.
 
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