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120v Extension Cord Charging

ai4px

Wes
May 2, 2018
447
478
Sumter SC USA
So I'm not quite sure I follow you, but after looking more closely at the Tesla Gen 2 connector that came with the car, I'm realizing I have 20 feet of cord with the Nema adaptor to plug into the 120v wall socket. So is your suggestion to get more of the same kind of cord, use the Tesla adaptor in the wall? Tesla's store doesn't have an extension cord, so I'm not quite sure what kind of cord I'd need to add between Tesla's wall adaptor and the original 20' cord. Sorry for my utter ignorance of electronics I just find it all very confusing!
No problem.... quick charge power makes a J1772 extension cord with a tesla plug on one end and J1772 on the other end. I can't find it on their website now... but I bought a 20 foot extension from them 2 years ago that had tesla plug at one end and J1772 at the other... really top quality cable. Their number is 760-798-0342. No, I don't work for them... but their cable is riding around in the back of my car.

found the invoice in my email...
Qty | Item # | Description | Price Each | Total Price
---------------------------------------------------------------------------------------------
1 | JDPTRSTB | JDapter Stub (Tesla Charge Station Adaptor) | $239.00
JDapter Stub - Select Maximum Length: +$89.00
JDapter Stub - 40 AMP - 20 foot upgrade
---------------------------------------------------------------------------------------------
Subtotal $328.00
Tax $0.00
Shipping (Priority Mail®) & Handling $19.20
---------------------------------------------------------------------------------------------
Balance Due $347.20
 
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Fadiawesome

Member
Sep 8, 2019
153
93
IDAHO
Murrieta CA doesnt spend a ton of time in temps that are actually "cold" ( I live in temecula, on the border of murrieta so am very familiar with the temps here). It does get to low to mid 30s overnight, but when people are talking about "cold" they usually talking about temperatures that are much lower than we see here.
oh I moved to Idaho, I just forgot to update that lol its gets to like 10 degrees here.
 
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jkirkwood001

Supporting Member
Feb 20, 2018
961
2,201
Ottawa, ON
I've been doing this about every second weekend for 2 years, @EmilyLC - summer through winter, with a standard 50 ft. extension, in rural Quebec - and it's worked fine. Like @Gasaraki said, I get ~1 KW / 10 A, but since we come up on Friday and leave Sunday, usually that charges right back up. I'm trying to remember the lowest battery level (I have a long range AWD 75 KWh) when we arrive and what it is when we leave.... Certainly in summer it's back up to 90% by Sunday, but winters, not so quick. This winter I'm travelling 2 1/2 hours to get there vs. 1 hour previous years, so might be short now and require stop on way back. Maybe 20% charged per day in cold winter? Be sure to turn off Sentry Mode.

Also, we have two cottages, and charging off the first has resulted in tripped the circuit (easy reset). The 2nd cottage has never tripped, and nothing has got too hot.
 
Oct 28, 2019
256
222
Texas
What @ai4px said. Avoid using an extension cord, it's not safe. It will likely work, at least for a while, but without monitoring the temperature at the outlet you're creating a ticking time bomb. There is a reason why the UMC has a temperature sensor built in. Going outside and checking the temperature every now and then is just not feasible. If it starts melting, it will happen fast, and you probably don't want to spend your time sitting next to the outlet with your hand on the plug.

From the UMC manual:

do not use a cheap extension cord without proper rating would be the more accurate answer. if you use a UL listed 10 gauge / 15amp rated extension cord it's totally safe... the same stuff you use to plug in demanding power tools....
 
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Fernand

Active Member
Mar 22, 2019
1,493
1,499
Northern california
My Lord, there are some frightened people around. Of course use a quality cable, and thicker is better. 10 Gauge wire is a bit of overkill, but it doesn't hurt. And shorter runs are better. If 25ft is enough, that's the length to get.

Why? because thinner wire has more resistance per foot, and the longer it is, the more resistance you end up with. So you waste some energy. Instead of getting 120v, you might get 118v. Where does the lost energy go? It warms the wire a little. No, it won't melt it, unless it's a truly dinky Christmas lights Dollar Store extension cord with very thin wires. It's like plugging in any power tool or bigger appliance. Or a hair dryer. It's not rocket science, and this is a backup for you. Don't let them drive you crazy.
.
 
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Andy7

Member
Dec 16, 2019
64
36
NJ
As mentioned above, do not leave the cables coiled. Coiling, unless I am remembering incorrectly, generates back EMF (electromagnetic force), a current in the opposite direction of the normal current flow, and this causes less current to your car and heating of the wire. Of course, if you leave it uncoiled someone will probably trip on it in the snow!

My car has occasionally given me a warning that I was using an inappropriate extension cord when I was not using an extension. From the comments here, I wonder if it was commenting on my outlet.
 

M3BlueGeorgia

Active Member
Dec 10, 2018
1,350
1,077
Atlanta, GA
do not use a cheap extension cord without proper rating would be the more accurate answer. if you use a UL listed 10 gauge / 15amp rated extension cord it's totally safe... the same stuff you use to plug in demanding power tools....

10 gauge is definitely overkill, unless you are trying for 100ft (30m)

The optimum combination of gauge, cost and amperage for 120v/15A household connection is 12 gauge. That should be good at 15 and 25 feet and maintaining 12A continuous.

Nowadays, after borrowing extension cords from relatives and being disappointed, I carry always a 15 ft 12 gauge extension cord.

BTW: Don't get tricked by weasel words such as "heavy-duty" when buying an extension cord. Look specifically for 12 gauge.
 

timk225

Active Member
Mar 24, 2016
2,031
1,057
Pittsburgh
OP, I posted this a while back, showing actual voltage loss from extension cords of different lengths and gauges, compared to no extension cord. Now I have a 12 gauge 25 foot cord in the trunk.

 
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phobos512

Member
Dec 31, 2018
8
9
Earth
As mentioned above, do not leave the cables coiled. Coiling, unless I am remembering incorrectly, generates back EMF (electromagnetic force), a current in the opposite direction of the normal current flow, and this causes less current to your car and heating of the wire. Of course, if you leave it uncoiled someone will probably trip on it in the snow!

My car has occasionally given me a warning that I was using an inappropriate extension cord when I was not using an extension. From the comments here, I wonder if it was commenting on my outlet.

A coiled cable will generate a static magnetic field. Remember wrapping a wire from a 12 volt battery around a nail as a kid and making an electromagnet, and if you did it for long enough, permanently magnetizing the nail? Same idea. It won't hurt electronics; you need a changing / moving magnetic field for that.

The reason why it's a concern in this case is the coiled cable will have less surface area exposed to air / surface it's sitting on, which means it'll be less able to dissipate heat to the surrounding environment, which could mean melting cables or fires. A thinner (numerically higher gauge) cable makes this a bigger concern.

Finally, "EMF" = Electromagnetic field (less common) or Electromotive Force.

IAAEE (or rather, IHABSiEEbibaltsIhdaEE; "I have a BS in Electrical Engineering but it's been a long time since I have done actual Electrical Engineering").
 
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ai4px

Wes
May 2, 2018
447
478
Sumter SC USA
As mentioned above, do not leave the cables coiled. Coiling, unless I am remembering incorrectly, generates back EMF (electromagnetic force), a current in the opposite direction of the normal current flow, and this causes less current to your car and heating of the wire. Of course, if you leave it uncoiled someone will probably trip on it in the snow!

My car has occasionally given me a warning that I was using an inappropriate extension cord when I was not using an extension. From the comments here, I wonder if it was commenting on my outlet.

if you coiled one wire, yes you are correct. But with the extension cord there are two wires and the current "coming" and "going" cancel each other out. The reason to not coil up extension cords is because of heat.
 
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ai4px

Wes
May 2, 2018
447
478
Sumter SC USA
My Lord, there are some frightened people around. Of course use a quality cable, and thicker is better. 10 Gauge wire is a bit of overkill, but it doesn't hurt. And shorter runs are better. If 25ft is enough, that's the length to get.

Why? because thinner wire has more resistance per foot, and the longer it is, the more resistance you end up with. So you waste some energy. Instead of getting 120v, you might get 118v. Where does the lost energy go? It warms the wire a little. No, it won't melt it, unless it's a truly dinky Christmas lights Dollar Store extension cord with very thin wires. It's like plugging in any power tool or bigger appliance. Or a hair dryer. It's not rocket science, and this is a backup for you. Don't let them drive you crazy.
.

Yes, the voltage drop on extension cords is an issue... but the BIGGER issue is that of a loose/corroded / poor condition receptacle on your house. This is why the EVSE (UMC) measures temperature.
 
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Kevin-rf

Member
Oct 12, 2018
102
87
New England
Not a great picture, but this is coiled extension cord the kido melted plugging in a space heater. If look on the edges you can see how melted the inner part of the coil is. What was a working cord is fused to the spool and melted enough to be a dead short. Thank goodness the breaker tripped.

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It has since been adopted by the local high-school for show and tell.

Point is get a good cord and don't let heat build up by coiling.
 

Andy7

Member
Dec 16, 2019
64
36
NJ
if you coiled one wire, yes you are correct. But with the extension cord there are two wires and the current "coming" and "going" cancel each other out. The reason to not coil up extension cords is because of heat.
Obviously I am not an electrical engineer, but you mean the heat generated from coiling is due only to the resistance in the wires and their proximity without the ability to dissipate the heat and not due to back EMF? I'm remembering high school physics (1961) wrong? Thanks.
 

Kevin-rf

Member
Oct 12, 2018
102
87
New England
Yes, the net magnetic field from the two wires inside the cord running current in equal and oposite directions cancel each other out.

That said, since opposites attract. The two wires in the cord pull towards each other. Melt the insulator and the wires are free to pull together and short.
 

UncleCreepy

Member
Mar 29, 2020
201
322
Lunenburg, ON
Ok, not that it matters in terms of the OPs question, but since there are a few wrong statements here, I'd like to clear that up.

The force between two conductors is attractive if the currents are in the same direction, repulsive if they are in opposite directions. Neutral and ground are normally at 0 Amps, so it's all about the two hot wires. Obviously the currents are in the opposite direction which means the two conductors will not pull towards each other.

Even if they did, the force would be about 9 mN/m at 48 Amps (that is assuming that the conductors are 5 mm apart, ymmv). That's the force you would get from less than 1 gram or 0.033 ounces evenly distributed over the length of a meter. That's not even worth mentioning.

And once again, the voltage drop on the extension cord is not really a problem. As pointed out before, the potential problem is that sockets wear out, so there is a potential risk that a bad connection between the socket and the prongs causes a significant voltage drop and therefore heat. That doesn't have to happen, but it can happen.
 
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byeLT4

Member
Feb 16, 2017
697
641
Texas
Just above 40 last night and so I let my pets have the garage and my car sat outside. Parked at 10% and a few hours later once cold it was down to 7. Didn't plan on it going this low and started getting warning messages. My intention was to get it back in the garage today once it warmed up and charge on 240 but.... I swapped the adapter for the 120 outlet and used a cheap 100 foot extension cord (all I had), which I really only needed about 10 feet of... I watched the voltage and it seemed to drop with 9-10 amps so I set it at 7, felt cables after about half an hour and seemed ok. Car gained @2 MPH going from 18 miles around midnight to 34 at 8am. Only thing strange was my normal 29x range at 100% was only showing 254 when plugged into 120v. After charging up to 50+% later I noticed all is back to normal.
 

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