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recommendation for 5-20 extension cord

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Don't look for extension cords named "safe for EVs" or "heavy duty. You need to know the AWG of the wires inside and make sure it's enough for the current you're putting in it. A 5-20 plug could provide 16A/120V so you need a gauge that supports that over 25ft. I think 12AWG is enough, that's what you should aim for in a 12A/120V situation at least. I will let others tell you with certainty. My point is that it's AWG that you must look at.

EDIT: EVSEAdapters are reputable. If they offer an extension for that plug type, I would trust it won't overheat.
 
Yes, the wire gauge is definitely the most important thing. When I first got my Tesla, I checked the extension cords I had, which both looked "beefy" and "heavy duty", but that just meant they had really thick insulation to prevent scrapes and cuts. They were both 16 gauge! That's way too thin wire for extended EV charging.

I agree that 12 gauge is the minimum you should go. I went ahead and got a 10 gauge one. Narrowing down to searching for only cords with 5-20 plugs specifically reduces your choices too much. 5-15 is much more common, so you can get a small 5-15 to 5-20 converter plug to go with it.

So something like this is a good cord choice:

It's 10 gauge and 25 feet.

And then here is a little plug converter:

Or if you want a little more flexible thing that doesn't stick straight out as far, something like this little 6 inch cord adapter:
 
Don't look for extension cords named "safe for EVs" or "heavy duty. You need to know the AWG of the wires inside and make sure it's enough for the current you're putting in it. A 5-20 plug could provide 16A/120V so you need a gauge that supports that over 25ft. I think 12AWG is enough, that's what you should aim for in a 12A/120V situation at least. I will let others tell you with certainty. My point is that it's AWG that you must look at.

EDIT: EVSEAdapters are reputable. If they offer an extension for that plug type, I would trust it won't overheat.
sorry, for clarity the extension cords on amazon for 5-20 are all 12 gauge but a few reviews showed them as overheating and/or slight burning within the clear plug end. it seems the poor quality comes from the connections of plug pins to wires, not the gauge of the cable
 
Yes, the wire gauge is definitely the most important thing. When I first got my Tesla, I checked the extension cords I had, which both looked "beefy" and "heavy duty", but that just meant they had really thick insulation to prevent scrapes and cuts. They were both 16 gauge! That's way too thin wire for extended EV charging.

I agree that 12 gauge is the minimum you should go. I went ahead and got a 10 gauge one. Narrowing down to searching for only cords with 5-20 plugs specifically reduces your choices too much. 5-15 is much more common, so you can get a small 5-15 to 5-20 converter plug to go with it.

So something like this is a good cord choice:

It's 10 gauge and 25 feet.

And then here is a little plug converter:

Or if you want a little more flexible thing that doesn't stick straight out as far, something like this little 6 inch cord adapter:

thanks for the links! unfortunately both of the adapters you show would limit the charging to 5-15 amperage (12a). i was hoping to charge off of 5-20 to get 16 amps. i suppose i could buy a 10 gauge 5-15 cord, cut the ends and buy 5-20 ends to put in pace but was hoping for a water tight setup thats already assembled.
 
thanks for the links! unfortunately both of the adapters you show would limit the charging to 5-15 amperage (12a).
No, it would not. You are not understanding my suggestion.
i was hoping to charge off of 5-20 to get 16 amps.
Yes, you can do that with the equipment I recommended.
i suppose i could buy a 10 gauge 5-15 cord, cut the ends and buy 5-20 ends to put in pace but was hoping for a water tight setup thats already assembled.
You would not need to do that. Don't cut pieces off and try to hand-wire things. That is probably going to be pretty bad connections and definitely not sealed. Watertight is another issue, but no extension cord setup is going to be watertight, regardless.

Here is how to use the things I was talking about for 5-20 charging at 16A. It is the Tesla UMC plug adapter that has the small computer chip in it to signal the proper amp limit to the car. So you use the Tesla 5-20 plug there to signal 16A. Then you use the tiny adapter piece (my last links) to make that Tesla 5-20 into a 5-15. Then that goes into your 5-15 extension, which goes into the outlet. 5-20 outlets are (almost) always backward compatible to accept either 5-15 or 5-20 plugs.

There is good reason I did it this way. It gives you one single 25 foot cord with thick wire gauge that you can use for either thing. If you bought only a 5-20 cord, it has the sideways prong that will not fit into 5-15 outlets, so you can't use it on those. You would have to buy two separate 25 foot extension cords! If you just get one 25 foot cord that has 5-15 plugs on it, then it has versatility. And to use it for 5-20, you just use that tiny adapter piece to switch it.
 
No, it would not. You are not understanding my suggestion.

Yes, you can do that with the equipment I recommended.

You would not need to do that. Don't cut pieces off and try to hand-wire things. That is probably going to be pretty bad connections and definitely not sealed. Watertight is another issue, but no extension cord setup is going to be watertight, regardless.

Here is how to use the things I was talking about for 5-20 charging at 16A. It is the Tesla UMC plug adapter that has the small computer chip in it to signal the proper amp limit to the car. So you use the Tesla 5-20 plug there to signal 16A. Then you use the tiny adapter piece (my last links) to make that Tesla 5-20 into a 5-15. Then that goes into your 5-15 extension, which goes into the outlet. 5-20 outlets are (almost) always backward compatible to accept either 5-15 or 5-20 plugs.

There is good reason I did it this way. It gives you one single 25 foot cord with thick wire gauge that you can use for either thing. If you bought only a 5-20 cord, it has the sideways prong that will not fit into 5-15 outlets, so you can't use it on those. You would have to buy two separate 25 foot extension cords! If you just get one 25 foot cord that has 5-15 plugs on it, then it has versatility. And to use it for 5-20, you just use that tiny adapter piece to switch it.


oh i get it now. thank you...my mistake for not understanding. two follow-ups.....

1)are you sure the 5-20 receptacle -if taking a 5-15 plug- can take the 16A? i get that the socket is backwards compatible (every kitchen t slot socket does this) but if there is an additional contactor in the receptacle for the sideways prong on a 5-20plug that is not touching the 5-15plug prong then the connection could over capacity. not sure if thats a thing but makes me want to open up a tslot to see.

2)your one adapters would still be out of spec and potentially a fire hazard (see below). not knocking your idea, the other adapter has 12awg wire and seems able to handle it, just if youre using this smaller adapter you might want to reconsider and get a different adapter.

1647449582556.png
 
1)are you sure the 5-20 receptacle -if taking a 5-15 plug- can take the 16A?
? It's a 5-20 rated receptacle. They are UL certified if they are being publicly sold on the market. It had BETTER be rated to supply 20A peak and 16A continuous. That is the specification it must meet.

2)your one adapters would still be out of spec and potentially a fire hazard (see below). not knocking your idea, the other adapter has 12awg wire and seems able to handle it, just if youre using this smaller adapter you might want to reconsider and get a different adapter.
Ah, good catch. Sure, there would be better ones out there then. I did see this from Amazon too:

It uses 12 gauge wire, so is probably better there.
 
? It's a 5-20 rated receptacle. They are UL certified if they are being publicly sold on the market. It had BETTER be rated to supply 20A peak and 16A continuous. That is the specification it must meet.

thats the specification when using the sideways (horizontal) prong for a 5-20 device. my point was if the prong is vertical (as in the 5-15 plug) its connection is different and may not be rated for 20a device since its supposed to be connecting to a 15a device. the image below shows how a 5-20 (horizontal) plug contacts different points in the receptacle than a 5-15. if the whole thing is for 20a thats great, just wasnt sure.


1647457633897.png




Ah, good catch. Sure, there would be better ones out there then. I did see this from Amazon too:

It uses 12 gauge wire, so is probably better there.
 
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thats the specification when using the sideways (horizontal) prong for a 5-20 device. my point was if the prong is vertical (as in the 5-15 plug) its connection is different and may not be rated for 20a device since its supposed to be connecting to a 15a device. the image below shows how a 5-20 (horizontal) plug contacts different points in the receptacle than a 5-15. if the whole thing is for 20a thats great, just wasnt sure.
Oooh, I see what you mean now. Hmm, that is an interesting one. I hadn't really thought of the prongs being different inside for the different parts of that T slot.