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Extension cord for 110v outlet charging (long term)

Hi all,

I’ve seen some posts regarding the use of extension cords for a short period of time but haven’t seen a post on long term solution. I’m expecting delivery of MYP sometime in January or early Feb so I’m researching my options before its arrival. Currently living in a condo and next to my indoor parking space, there’s a 110v receptacle outlet with one of those covers on it. It seems like the receptacle was installed upside down as the ground connector is on top. A neighboring car is storing his vintage benz for the winter and has what it seems to be a battery maintainer hooked up to the bottom outlet. Since the receptacle is installed upside down, part of cord which extends from the bottom of the plug (much like the tesla 110v wall charger plug/cord placement) will be in the way if I use the plug on top of his. I mean, I guess I can bend his cord as it’s fairly thin compared to our EV charging cord and shove mine in on top of his but that’s just rude.

Another option would be for me to get a short 12g extension cord where the cord comes out from behind the prongs instead of from the side. I understand there are more fire risks the longer the cord. I’ve seen 12g 20amp extension cords that are 1 foot which I’m considering on purchasing now especially with the supply chain issues. **My big question is—would it be safe for me to use a 1 foot 12g 20amp to charge my YP on a permanent basis?**

Our condo parking garage is limited on how much electricity they are getting in but our board is brainstorming on how to get more in and the cost associated with it. We are getting more and more Tesla owners in our building and this has become a problem with very limited outlets in our garage. We were fortunate to have purchased a spot with an outlet next to it and also fortunate that it’s heated so no worries on battery draining faster than it’s charging on a regular wall outlet :)
 
I also understand that Tesla says extension cords should not be used, but I‘m assuming it’s because most people would probably end up using the wrong type of extension cord.

Two reasons Tesla doesn't want people to use extension cords, the one you stated about people using low current rated extension cords, and the second reason is many outlets are old / cheap and the Tesla mobile connector plugs have a built in temperature protection system in case the outlet is faulty. If you use an extension cord (even properly rated) you are risking that the outlet is of poor quality or too old to handle high current for long periods of time and without the tesla mobile connector being plugged directly into the outlet you loss the thermal protection built into the tesla unit.

If you lived in a house where you could install your own high quality industrial grade outlet and use a high current rated extension cord I would say "go for it" but in your situation using an outlet of unknown quality I can't recommend using an extension cord.

Keith
 

ATPMSD

Active Member
Mar 12, 2021
1,352
1,238
Atlanta, GA
The easiest and best fix is to get the Board to flip the outlet so the ground is at the bottom. If you are comfortable doing this just get their permission. Otherwise, a one-foot 12g extension cord is fine. While you are at it, as suggsted by @Fourdoor, check the quality of the outlet and replace it with a high quality one if you need too.

One more point, if this is a 20A circuit and you use the Tesla 20A adapter you will be pulling 16A, which is the limit for a continuous draw on a 20A circuit (which means the battery maintainer will put you over the limit.) If you use the standard adapter that came with the car, then you will draw 12A, which should leave enough room for the battery maintainer.
 
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I noticed that the Gen 2 mobile adapters have the cord come out from underneath the plug and it looks as though some Gen 1‘s has the cord come straight out behind the plug. Is there anything out there that other Tesla owners in similar predicament have been doing to get past this? Doing all this just to prevent having to bend the cord at the base of plug to get around the stupid outlet cover. Any ideas? Even if I can have whatever connector that’s in the picture, it would solve all of my problems! But it seems like this is the old adapter :(


C029FE22-7E3C-455F-8C62-A27041695238.jpeg
 

jcanoe

Well-Known Member
Oct 2, 2020
5,554
6,106
Maryland
The 120V receptacle you plan to use may be on a circuit with other equipment, lights etc. beside the battery trickle charger. What if another plug-in vehicle is also charging using this circuit? If you charge at 120V and 12A (1.4kW) this can only be done when you know that there is no other equipment connected, running on the same 15A circuit. You may have to limit your charging to 120V and 8A (960W). If on a 20A circuit then there would be additional capacity beyond 12A for charging. Even then two EVs charging would have to be limited to a total of no more than 16A. Post a photo of the 120V receptacle, this should reveal if the 120V circuit is 15A or 20A. What is your plan if the circuit breaker trips?

An issue with all extension cords is that using an extension cord results in an additional electrical interconnect where moisture can get into the connection. I have experienced situations where moisture causes a GFCI to trip and cut off the power, even though the circuit was not overloaded.

Flipping the receptacle so that the ground connection is at the bottom should be possible. (If you inspect other receptacles what is the orientation?) Perhaps the receptacles are all oriented that way due to a local electrical code requirement. The National Electrical Code (NEC) only specifies the orientation of power receptacles in hospital installations, not residential.
 
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ATPMSD

Active Member
Mar 12, 2021
1,352
1,238
Atlanta, GA
Nothing wrong with using an extension cord. Just use a commercial heavy duty one that's able to carry x2 the amount you're looking for. Example if you're using a 110 purchase a cord for 220+ (outdoor use and water proof).

IMHO that is overkill. For a 120V / 20A circuit, 12-gauge is good for 50‘. For say 10’, 14-gauge is fine.

 
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dhrivnak

Active Member
Jan 8, 2011
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NE Tennessee
Hi all,

I’ve seen some posts regarding the use of extension cords for a short period of time but haven’t seen a post on long term solution. I’m expecting delivery of MYP sometime in January or early Feb so I’m researching my options before its arrival. Currently living in a condo and next to my indoor parking space, there’s a 110v receptacle outlet with one of those covers on it. It seems like the receptacle was installed upside down as the ground connector is on top. A neighboring car is storing his vintage benz for the winter and has what it seems to be a battery maintainer hooked up to the bottom outlet. Since the receptacle is installed upside down, part of cord which extends from the bottom of the plug (much like the tesla 110v wall charger plug/cord placement) will be in the way if I use the plug on top of his. I mean, I guess I can bend his cord as it’s fairly thin compared to our EV charging cord and shove mine in on top of his but that’s just rude.

Another option would be for me to get a short 12g extension cord where the cord comes out from behind the prongs instead of from the side. I understand there are more fire risks the longer the cord. I’ve seen 12g 20amp extension cords that are 1 foot which I’m considering on purchasing now especially with the supply chain issues. **My big question is—would it be safe for me to use a 1 foot 12g 20amp to charge my YP on a permanent basis?**

Our condo parking garage is limited on how much electricity they are getting in but our board is brainstorming on how to get more in and the cost associated with it. We are getting more and more Tesla owners in our building and this has become a problem with very limited outlets in our garage. We were fortunate to have purchased a spot with an outlet next to it and also fortunate that it’s heated so no worries on battery draining faster than it’s charging on a regular wall outlet :)
I have done it and as long as it is a quality cord of 12 or 10 gauge and you check monthly for heat and wear I would not worry.
 
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The 120V receptacle you plan to use may be on a circuit with other equipment, lights etc. beside the battery trickle charger. What if another plug-in vehicle is also charging using this circuit? If you charge at 120V and 12A (1.4kW) this can only be done when you know that there is no other equipment connected, running on the same 15A circuit. You may have to limit your charging to 120V and 8A (960W). If on a 20A circuit then there would be additional capacity beyond 12A for charging. Even then two EVs charging would have to be limited to a total of no more than 16A. Post a photo of the 120V receptacle, this should reveal if the 120V circuit is 15A or 20A. What is your plan if the circuit breaker trips?

An issue with all extension cords is that using an extension cord results in an additional electrical interconnect where moisture can get into the connection. I have experienced situations where moisture causes a GFCI to trip and cut off the power, even though the circuit was not overloaded.

Flipping the receptacle so that the ground connection is at the bottom should be possible. (If you inspect other receptacles what is the orientation?) Perhaps the receptacles are all oriented that way due to a local electrical code requirement. The National Electrical Code (NEC) only specifies the orientation of power receptacles in hospital installations, not residential.
Here’s the photo of the receptacle, and also of the neighbor’s plug.

EA33F5C8-D589-4C96-92B7-E4942ABF9147.jpeg
E8159293-23BC-4891-ACAB-CCF23AECC5E0.jpeg
 

jcanoe

Well-Known Member
Oct 2, 2020
5,554
6,106
Maryland
The photo shows that this is a NEMA 5-20 GFCI receptacle (120V/20A). Assuming that the wiring, circuit breaker is correct (no way to tell without inspecting the wire used and the circuit breaker at the panel) you could use either the NEMA 5-15 power plug adapter that comes with the Tesla Gen2 Mobile Connector kit or the NEMA 5-20 power plug adapter ($35 from the Tesla store.) The issue with using the receptacle is, as far as I can tell that you don't know what other equipment is sharing the same circuit. In this case the Tesla Mobile Connector when used with the NEMA 5-20 power plug adapter will default to 16A and would likely overload the circuit if any other device is powered by the same circuit. The trickle charger, if it is like most 12V battery tenders, draws 1.25A.

The cover on the receptacle box serves no purpose (inside a garage) other than having the ability to lock the receptacle. If would be easy to modify/replace the cover to eliminate the cover and gain better access to the receptacle. The receptacle looks to be more than 5 years old and should be replaced. You want a clean tight connection at the receptacle for the power plug or extension cord. An old, worn receptacle should not be used when charging an EV.

Even if you flip the receptacle 180 degrees the design of the trickle charger power plug and the Tesla Mobile Connector power plug adapter will still make it impossible to use both outlets of the receptacle at the same time unless you use an extension cord or a socket extender.

A trickle charger is a low power device (as compared to the Tesla Mobile Connector.) It would be better to plug the Tesla Mobile Connector directly into the receptacle and use a socket extender for the trickle charger. If you use a socket extender then you would not need to use an extension cord with the Tesla Mobile Connector.

You could use an outlet extender such as this one for the trickle charger: https://www.amazon.com/GE-Adapter-Splitter-Grounded-54541/dp/B001UE85VG/
 
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The photo shows that this is a NEMA 5-20 GFCI receptacle (120V/20A). Assuming that the wiring, circuit breaker is correct (no way to tell without inspecting the wire used and the circuit breaker at the panel) you could use either the NEMA 5-15 power plug adapter that comes with the Tesla Gen2 Mobile Connector kit or the NEMA 5-20 power plug adapter ($35 from the Tesla store.) The issue with using the receptacle is, as far as I can tell that you don't know what other equipment is sharing the same circuit. In this case the Tesla Mobile Connector when used with the NEMA 5-20 power plug adapter will default to 16A and would likely overload the circuit if any other device is powered by the same circuit. The trickle charger, if it is like most 12V battery tenders, draws 1.25A.

The cover on the receptacle box serves no purpose (inside a garage) other than having the ability to lock the receptacle. If would be easy to modify/replace the cover to eliminate the cover and gain better access to the receptacle. The receptacle looks to be more than 5 years old and should be replaced. You want a clean tight connection at the receptacle for the power plug or extension cord. An old, worn receptacle should not be used when charging an EV.

Even if you flip the receptacle 180 degrees the design of the trickle charger power plug and the Tesla Mobile Connector power plug adapter will still make it impossible to use both outlets of the receptacle at the same time unless you use an extension cord or a socket extender.

A trickle charger is a low power device (as compared to the Tesla Mobile Connector.) It would be better to plug the Tesla Mobile Connector directly into the receptacle and use a socket extender for the trickle charger. If you use a socket extender then you would not need to use an extension cord with the Tesla Mobile Connector.

You could use an outlet extender such as this one for the trickle charger: https://www.amazon.com/GE-Adapter-Splitter-Grounded-54541/dp/B001UE85VG/
jcanoe,
Thank you so much!! This makes sense and agree that this is an ideal solution. I’m going to reach out to my condo and ask for them to replace the receptacle with a new one while making sure to install with ground pointing down. Happy Holidays!
 
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ATPMSD

Active Member
Mar 12, 2021
1,352
1,238
Atlanta, GA
The plug for the battery maintainer looks MASSIVE! There is also no room to install your plug, in fact it will be hard to install an extension cord. What you need to do is to work with your neighbor and put in a bus bar that will accommodate both plugs. Also check the draw of that battery maintainer. For example:



 
If you think about it, the wiring from your service panel to the receptacle is essentially an extension cord. The difference is the wire gauge and connections are (hopefully) up to code and designed for the installation. Outside the wall you get people using whatever they can find at the dollar store and daisy-chaining 3 of them together. Like @jcanoe said, you also have additional connections which are subject to corrosion, etc. as well as the total circuit draw considerations.
 
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Rocky_H

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Feb 19, 2015
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Boise, ID
Interesting thread. A few thoughts:

1. Yeah, that little 1 foot 12 gauge extension would be really good for getting things to fit for one or the other of those two plugs.

2. You mentioned getting them to replace that with ground pin down--excellent. And then using that little extension, this should work well.

3. My main concern would be with amps as @jcanoe mentioned, since this is sharing with other things. I would probably keep this turned down to about 8 amps from the car screen. Most of the early cheapy electric cars came with amps set to 8 by default, because they were expecting people would be using whatever shared outlets were available, and you had to specifically turn it up to 12A if you knew you had a good dedicated one.
 
I have a 50ft commercial grade extension cord in my Y. Use it off and on when I'm at my weekend home (1.5 hours away). I rarely use it, but it's nice to have. Can charge my Y overnight and get 70+ miles. Worth keeping in the car. Never had issues. Just don't purchase a cheap cord :D
 
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Rocky_H

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Feb 19, 2015
7,977
10,105
Boise, ID
I have a 50ft commercial grade extension cord in my Y. Use it off and on when I'm at my weekend home (1.5 hours away). I rarely use it, but it's nice to have. Can charge my Y overnight and get 70+ miles. Worth keeping in the car. Never had issues. Just don't purchase a cheap cord :D
I notice you made no mention at all of what thickness of wire gauge you are using. That makes FAR more difference than any warnings of "Don't purchase a cheap cord". A lot of extension cords focus more on being "tough" and "heavy duty" but they are talking about the thickness and toughness and scrape resistance of the outer sheath and not about the wire gauge at all. I had two very sturdy looking extension cords at home when I got my Tesla that looked very thick and well made, but when I read the imprinting on them, they were both just 16 gauge wire!! So I will always recommend at least 12 gauge wire thickness, and within that, get whatever length or deal works for you.
 
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I notice you made no mention at all of what thickness of wire gauge you are using. That makes FAR more difference than any warnings of "Don't purchase a cheap cord". A lot of extension cords focus more on being "tough" and "heavy duty" but they are talking about the thickness and toughness and scrape resistance of the outer sheath and not about the wire gauge at all. I had two very sturdy looking extension cords at home when I got my Tesla that looked very thick and well made, but when I read the imprinting on them, they were both just 16 gauge wire!! So I will always recommend at least 12 gauge wire thickness, and within that, get whatever length or deal works for you.
Good point. I have a Dewalt 10 gauge 50ft cord. 100% at least 12 gauge for charging use. Great thing about all the under storage of the Tesla, you never see it :D
 
Just don't purchase a cheap cord :D

I notice you made no mention at all of what thickness of wire gauge you are using. That makes FAR more difference than any warnings of "Don't purchase a cheap cord".
Yes, the wire gauge is key, but I have yet to see a cheap cord with heavy gauge wire. Copper is far more expensive than plastic, and the good cords that are designed to carry current without dropping the voltage use heavier gauge wire and are more expensive. People get sticker shock and get the one next to it on the shelf that looks just as good but has half the copper.
 

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