Burning 25ft 10/3 cords using my mobile connector in the rain with a 120v outside GFCI outlet

[ucmndd]

Another thought as an interim measure - One reason cords burn or melt is when too much current flows through them. Limit your charging amps with the app. A 115V, 15 amp circuit is likely what you are using. Limit the current to 80% of that 15 Amps, which is 12 Amps. But seriously, you shouldn't be using an extension cord. Buy the Wall Charger.

The 5-15 plug for the mobile connector is limited to 12 amps by design. It will never supply 15 amps.

 

[arnolddeleon]

I'm not sure of all this, but look at it this way:

1. Say you grab your handy 3-wire hair drier (hot, neutral, and safety ground wire) and turn it on. Current flows (more or less) from the hot to the neutral (the two blades on a standard 120 VAC socket), but no current flows on the safety ground. Ye GFCI does not trip because what it's looking for is current on the ground wire and there's none of that stuff.
2. Now, grab the 3-wire hair drier, on or off, and throw it into a full bathtub. Everything gets connected to everything (more or less) and current flows out of the hot and into both the neutral and ground. There'll be significant current on the ground wire, and the Ground Fault CI will detect that, pop open the connection at the socket for the hot and neutral (at least, I think it's just the hot and neutral, but it might be all three) and Saves The Day.
3. Next, consider a Standard House Connection. Down from ye power pole comes three wires: A hot, another hot 180 degrees out of phase, and a neutral. Note: No Ground. Then, as standard practice, the two hots and neutral go through the meter and, at the breaker box, the two hots go to the two hot bus bars and the neutral gets bolted to the neutral/ground bus bar. In Addition, A Big Green Wire gets bolted to that same neutral/ground bus bar, goes out of the house, and gets bolted, securely, to a no-kidding 6-foot copper ground stake that has been pounded into the physical ground. I've actually watched an electrician do this one year with a sledge hammer, starting off by standing on an a-frame ladder, and working the stake down until a couple of inches are left above grade. He then attached the copper wire from the breaker box to the ground stake with a thoroughly tightened clamp.

For what it's worth, all the houses in the area have their own ground stakes, giving the neutral up there on the power pole a kind of distributed connection to ground. Interestingly, despite dirt/gravel/rocks/soil/whatever, the actual resistance, measured with an ohmmeter, between ground stakes is down in the milliohms. What moist or dryish dirt loses by having relatively high resistance compared, say, to copper, it makes up by having the biggest cross-sectional area you've ever seen, and that makes R very, very low in R = resistivity_of_a_conductor/(area of said conductor).​

Now, consider the OP. There's moisture in the junction between the Mobile Connector and the extension cord. For fun, I'm going to claim that the Hot blade is closest to the physical ground (as in, dirt/soil/asphalt), and any moisture between the hot blade and the ground pin is either blocked or evaporated. Let there develop a current between the hot blade, through the ground, through the multitudinous ground stakes in the neighborhood (low resistance) and into the neutral/ground bus bar, and there's your circuit, leading back to city power.

So, yeah, if one gets a case of everything hooked to everything, then the ground wire would conduct, too - but it's not a tub of water where that's guaranteed. Instead, it's hot to (physical) ground, but not hot to the electrical ground wire. If there's no current (or very little current) on the electrical ground wire, the GFCI won't trip.

Now, if somebody stands up and says that a GFCI, besides checking for current on the ground wire, checks to make sure that the current on the hot and neutral are equal, then I take it all back.

GFCI don't work the way you think. The ground wire is irrelevant. Using a GFCI outlet is a code compliant way to replace a two prong outlet (without a ground). A GFCI is simply looking for the difference between the hot and neutral. You can search the internet for an explanation. How do you think a GFCI works with a two-wire cord?

[edited to add a missing word]

 

[arnolddeleon]

My recommendation for the OP. Get one of the plug-in outlet testers that that has GFCI test button. Test that the GFCI outlet trips with from the extension cord.

I think they're on the right track of getting something to keep the connection between the mobile connector and the extension.

I agree with the suspicion that there is current leak. The GFCI should trip if the leak is ground wire or the literal ground. It's also possible the extension is defective, and the leak is between the hot and neutral at the female end of the extension cord. In that situation the GFCI will not trip because the current is balanced between the hot and neutral.

 

[KevinT3141]

Now, if somebody stands up and says that a GFCI, besides checking for current on the ground wire, checks to make sure that the current on the hot and neutral are equal, then I take it all back.

I am standing up to say that it doesn't check the current on the ground wire, it only checks that the current in the hot and neutral are equal. That's exactly why it will work on that 2-wire hair dryer.

If you have 15 minutes to spare, watch this:

 

[petercc9]

Another thought as an interim measure - One reason cords burn or melt is when too much current flows through them. Limit your charging amps with the app. A 115V, 15 amp circuit is likely what you are using. Limit the current to 80% of that 15 Amps, which is 12 Amps. But seriously, you shouldn't be using an extension cord. Buy the Wall Charger.

12 amps is the max the car will let you on 110V

 

[petercc9]

What is the distance from the outlet to the charge port,?

Exactly the max length of the mobile charger cord if you suspend it midair and like playing limbo games and putting unneeded strain on the wires.

hmm i see they make 10 ft extension cords.

 

[MP3Mike]

12 amps is the max the car will let you on 110V

Not true. You can use the 5-20 adapter and draw 16 amps on 120v.

 

[petercc9]

Speaking as an engineer: If you've got char marks on the ground, then I agree with the other posters here that you likely had arcing between the cord and ground.

I'm making a bet that when you have the car charging, the junction between the plug of the Mobile Connector and the socket for your extension cord are lying on the ground. This is wrong on so many levels it's hard to count.

No the connections never touch the physical ground. I ALWAYS make sure the actual junction is suspended. The wires themselves may be touching the ground but the connection itself is always 6 inches above it. Sometimes when in a rush I don't adequately cover the connection and water may be infiltrating. The GFCI trips and will refuse to work with the cord. Will work with the mobile charger plugged in directly without cord. Inspection shows blackness on the ground wire (3rd wire) in the extension cord. That's an immediate "no more questions asked" throw away cord scenario for me.

I'm sure the GFCI outlet is as plastic as the homebuilder could get. House built in 2005. GFCI outlets in front and back of house. Using back outlet. The front outlet has the buttons and nothing plugged in. Mobile connector can reach by itself if fully stretched and floating midair. Too much strain on wire and of course the wire going in opposite direction of the plug so you'd need a 180 direction turn at the outlet which of course is unacceptable. Just need a few more extra feet of wire so things aren't straining. Using 10 gauge.

I'm guessing the issue is where the two cords connect..it could be at the charger door..but then it would be a commonly seen problem.

Last time it happened it was charging all night fine. It was raining. I unplugged my charger from the car. Put it facing face down suspended. did an errand. Came back and plugged it back in. I hadn't touched the area where the two cords connected. Within 15 minutes it was dead. No lights on mobile charger. Pressing GFCI button had no affect. Mobile charger no green lights. Pressing GFCI buttons not sending power to mobile connector (no greens) through extension cord. Only when plugging in mobile connector directly could i see green lights. Having had this happen before I looked at the 3rd prong on the extension cord (clear connector color so i could see inside) and it had blackness.

 

[ewoodrick]

I am standing up to say that it doesn't check the current on the ground wire, it only checks that the current in the hot and neutral are equal. That's exactly why it will work on that 2-wire hair dryer.

If you have 15 minutes to spare, watch this:

And so, if it escapes to physical ground it wouldn't be equal and should trip?

 

[ewoodrick]

No the connections never touch the physical ground. I ALWAYS make sure the actual junction is suspended. The wires themselves may be touching the ground but the connection itself is always 6 inches above it. Sometimes when in a rush I don't adequately cover the connection and water may be infiltrating. The GFCI trips and will refuse to work with the cord. Will work with the mobile charger plugged in directly without cord. Inspection shows blackness on the ground wire (3rd wire) in the extension cord. That's an immediate "no more questions asked" throw away cord scenario for me.

I'm sure the GFCI outlet is as plastic as the homebuilder could get. House built in 2005. GFCI outlets in front and back of house. Using back outlet. The front outlet has the buttons and nothing plugged in. Mobile connector can reach by itself if fully stretched and floating midair. Too much strain on wire and of course the wire going in opposite direction of the plug so you'd need a 180 direction turn at the outlet which of course is unacceptable. Just need a few more extra feet of wire so things aren't straining. Using 10 gauge.

I'm guessing the issue is where the two cords connect..it could be at the charger door..but then it would be a commonly seen problem.

Last time it happened it was charging all night fine. It was raining. I unplugged my charger from the car. Put it facing face down suspended. did an errand. Came back and plugged it back in. I hadn't touched the area where the two cords connected. Within 15 minutes it was dead. GFCI tripped. Mobile charger no green lights. Pressing GFCI buttons not sending power to mobile connector (no greens) through extension cord. Only when plugging in mobile connector directly could i see green lights. Having had this happen before I looked at the 3rd prong on the extension cord (clear connector color so i could see inside) and it had blackness.

You've got at least me confused then,

Going back to your initial statement.

and then see a black mark on the ground on the female side of the extension cord.

Are you saying on the physical ground (like dirt or concrete), or on the ground socket on the plug?

And if you said it did it during the rain, and the plug was not weather protected, then simply yes. That's the way electricity works. Get a drop of water in the wrong place and electricity will find it, use it, and evaporate it.

 

[petercc9]

You've got at least me confused then,

Going back to your initial statement.



Are you saying on the physical ground (like dirt or concrete), or on the ground socket on the plug?

And if you said it did it during the rain, and the plug was not weather protected, then simply yes. That's the way electricity works. Get a drop of water in the wrong place and electricity will find it, use it, and evaporate it.

The third wire is the "ground" wire. The female side of the extension cord is clear plastic so you can see the wire connections inside.

I don't have the wire anymore to snap pictures. It may have been more than just the 3rd wire. It was obvious something had happened and so that was that and i didn't inspect it more closely and threw it away so it would never be accidentally used again.

This was a 25ft 10 gauge wire. The one below. Not exactly a cheap wire.

https://www.amazon.com/gp/product/B0B7CGPZWD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Previously I had fried a 10 gauge Yellow Jacket wire but it was more than 25 feet (50 or more..can't remember..had it for years..rarely used) and I figured it was simply a too long of a cord length issue so i switched to 25.

I have been home charging since May 2023 and now on my 3rd extension cord (25ft 10/3 gauge wire from Iron Forge)

 

[Tronguy]

The third wire is the "ground" wire. The female side of the extension cord is clear plastic so you can see the wire connections inside.

I don't have the wire anymore to snap pictures. It may have been more than just the 3rd wire. It was obvious something had happened and so that was that and i didn't inspect it more closely and threw it away so it would never be accidentally used again.

This was a 25ft 10 gauge wire. The one below. Not exactly a cheap wire.

https://www.amazon.com/gp/product/B0B7CGPZWD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Previously I had fried a 10 gauge Yellow Jacket wire but it was more than 25 feet (50 or more..can't remember..had it for years..rarely used) and I figured it was simply a too long of a cord length issue so i switched to 25.

I have been home charging since May 2023 and now on my 3rd extension cord (25ft 10/3 gauge wire from Iron Forge)

For what it's worth, the SO and I had tried using a $RANDOM extension cord from our garage and, like many others, discovered that the voltage drop along the wire was big enough to trip the Tesla's Save-The-Day function, where it drops the current being drawn to a level that, presumably, won't cause burns and such.

The idea here is that a Tesla can't tell the difference between a faulty socket/bad wiring job/etc. and an extension cord whose wire gauge is Just Too Darn Small. So in the interests of not burning the house down, the current gets reduced from (with a NEMA5-15) from 12A to 8A or so. Since power dissipation goes as the square of the current (I*I*R), that reduces any potential heating by a ratio of 8*8/(12*12) = 44%. It's guessed that it does this by sampling the voltage at the car with no current drawn; then sampling the voltage with current drawn, comparing, then doing the save-the-day reduction. I guess that if the voltage drop is humongous, the Tesla will simply refuse to charge.

So, feeling somewhat bloody minded after the SO was unable to charge on a trip to a friend's house, far away, I showed up at Home Depot and started looking very carefully at what they had for sale. It was interesting: A lot of big text all over their extension cords for sale saying HEAVY DUTY, but not a darn thing about what wire gauge was in there. I got the impression that Heavy Duty, at least at Home Depot, simply meant Lots of Plastic Insulation. Copper being a lot more expensive than plastic.

The next step was a trip to Harbor Freight, a place known to sell to contractors and the like. It was an eye-opener. If they said that they had a 15A, 25' extension cord, it really was one of those things, cost a lot more than the Home Depot Specials, and the gauge was printed on the package. Further, if one bought (say) a 50', 15A cord, it was a lot more expensive than the 25-footer, presumably because, when one is trying to control the voltage drop, a 50' cord needs a lot bigger gauge wire to keep the voltage drop under control. They also had 20A 120VAC extension cords of various lengths and Even More Expense, complete with the right-angle blade one sees on a NEMA5-20 connector.

If memory serves, they also had 100' extension cords with eye-watering prices. I've since heard around here that when running, say, a circular saw, said saw can be damaged if there's too much voltage drop, but there are people who know lots more about that than I do.

In any case, snagged one of the heavy ones, 25' I think, took it to the garage at home, and did an A vs. B comparison. The $RANDOM extension cord caused current reduction: The Harbor Freight didn't. One each of the HF ones live in the wells of each of the trunks of the M3 and MY in the garage.

Now.. Don't know where you got your extension cord, but "clear plastic" sounds, well, a little.. suspicious. The ones at HF look like the rugged ones that get dragged through undeveloped lots and all. Is it possible that you got your 10 Ga. wire, but the actual construction of the female socket wasn't up to snuff?

If something Didn't Work at a contracting site, I imagine that an irritated contractor would show up at HF with Words; that won't happen very much with an Amazon knock-off.

 

[petercc9]

For what it's worth, the SO and I had tried using a $RANDOM extension cord from our garage and, like many others, discovered that the voltage drop along the wire was big enough to trip the Tesla's Save-The-Day function, where it drops the current being drawn to a level that, presumably, won't cause burns and such.

The idea here is that a Tesla can't tell the difference between a faulty socket/bad wiring job/etc. and an extension cord whose wire gauge is Just Too Darn Small. So in the interests of not burning the house down, the current gets reduced from (with a NEMA5-15) from 12A to 8A or so. Since power dissipation goes as the square of the current (I*I*R), that reduces any potential heating by a ratio of 8*8/(12*12) = 44%. It's guessed that it does this by sampling the voltage at the car with no current drawn; then sampling the voltage with current drawn, comparing, then doing the save-the-day reduction. I guess that if the voltage drop is humongous, the Tesla will simply refuse to charge.

So, feeling somewhat bloody minded after the SO was unable to charge on a trip to a friend's house, far away, I showed up at Home Depot and started looking very carefully at what they had for sale. It was interesting: A lot of big text all over their extension cords for sale saying HEAVY DUTY, but not a darn thing about what wire gauge was in there. I got the impression that Heavy Duty, at least at Home Depot, simply meant Lots of Plastic Insulation. Copper being a lot more expensive than plastic.

The next step was a trip to Harbor Freight, a place known to sell to contractors and the like. It was an eye-opener. If they said that they had a 15A, 25' extension cord, it really was one of those things, cost a lot more than the Home Depot Specials, and the gauge was printed on the package. Further, if one bought (say) a 50', 15A cord, it was a lot more expensive than the 25-footer, presumably because, when one is trying to control the voltage drop, a 50' cord needs a lot bigger gauge wire to keep the voltage drop under control. They also had 20A 120VAC extension cords of various lengths and Even More Expense, complete with the right-angle blade one sees on a NEMA5-20 connector.

If memory serves, they also had 100' extension cords with eye-watering prices. I've since heard around here that when running, say, a circular saw, said saw can be damaged if there's too much voltage drop, but there are people who know lots more about that than I do.

In any case, snagged one of the heavy ones, 25' I think, took it to the garage at home, and did an A vs. B comparison. The $RANDOM extension cord caused current reduction: The Harbor Freight didn't. One each of the HF ones live in the wells of each of the trunks of the M3 and MY in the garage.

Now.. Don't know where you got your extension cord, but "clear plastic" sounds, well, a little.. suspicious. The ones at HF look like the rugged ones that get dragged through undeveloped lots and all. Is it possible that you got your 10 Ga. wire, but the actual construction of the female socket wasn't up to snuff?

If something Didn't Work at a contracting site, I imagine that an irritated contractor would show up at HF with Words; that won't happen very much with an Amazon knock-off.

Looking at the Harbor Freight site it looks like many of their 10 gauge cords also have "transparent" cord ends. This is pretty standard.

I'm using a 25ft 10 gauge extension cord on a 15 amp outlet which as somebody pointed out is overkill because even the wiring behind the outlet to the electrical box isn't even 10 gauge wire (it's thinner 14 gauge) and it is far longer. 10 gauge is even overkill for those 20 amp outlets with the T prong holes which you see in jam packed office buildings (12 gauge wires). I intentionally picked 10 gauge because it is so much overkill which would be important when dealing with car charging and fire risks. There should be minimal electrical loss over that 25 feet of thick wire. Plus the Mobile connector has adapters for higher amp plugs so it can also handle much higher loads. So all this heavy duty stuff should not cause an issue on a measly 15 amp line. Even when charging it won't go over 12amps. I think 10 gauge is rated to handle 30amps. As I recall the danger is always on the end furthest from the electrical box. That will be the part that heats up the most. However if that end is super thick then there should be no issue.

10 Gauge Extension Cords - Harbor Freight Tools

Harbor Freight buys their top quality tools from the same factories that supply our competitors. We cut out the middleman and pass the savings to you!

www.harborfreight.com

example:

 

[petercc9]

I was under the impression using an extension cord is strongly advised not to do. I just had someone install an outlet closet and deleted the one that would reach

That's probably because Tesla knows no matter what they say people will attempt to use some thin 16 gauge $5 cord and burn their house down. So they just tell people don't do it at all.

 

[petercc9]

Could a product like this be helpful? Amazon.com

No, unfortunately the mobile connector is at a right angle. This cover is expecting a straight connection. Won't fit.

 

[petercc9]

Another thought as an interim measure - One reason cords burn or melt is when too much current flows through them. Limit your charging amps with the app. A 115V, 15 amp circuit is likely what you are using. Limit the current to 80% of that 15 Amps, which is 12 Amps. But seriously, you shouldn't be using an extension cord. Buy the Wall Charger.

12 is the Max the app will allow on a standard 3 prong US wall plug. Well within 15. To get more than 12 you would need a 20amp outlet with the T shaped Mobile adapter connector or the other oddball ones.

 

[petercc9]

If the plug is leaving burn marks on the ground, my first guess is that the GFCI is faulty. AFAIK, it should NEVER do that. That's an example of a LOT of stray electricity floating around. And that's deadly.

A plug cover should help as @boones suggested or something like https://www.amazon.com/Waterproof-Weatherproof-Electrical-Connection-Decoration/dp/B08CMQHYLL/ref=sr_1_4?crid=ZS4UPR6QBHZM&dib=eyJ2IjoiMSJ9.wjH4M-ZDMg-8NczNakCBeUB3tMR5OlZEjaIFJXHdDEUQq9TGtDkn6chp0xRC6QlWzp9s6dKIpEh4fOO8jNl5OayJx9Sg9I4E_r751PGCgxeO0vuLw0sSkpZ6PIjf3TqL8bQMV3Y-uUYVs0Or7VReA9HgMMjL7yzwaI2roTZoN_sXFYbf9SDl9l3SkB6KuDVHnpSKC0d6BGZ3tFgLsM7KN38qbn7VvKU2sPNgUjxt0mo.eDfQAXubeGXX6Rarhh-LYKkktZj-ZyQhycFV28mczsA&dib_tag=se&keywords=extension+cord+cover&qid=1709216747&sprefix=extension+cord+co,aps,199&sr=8-4&th=1

Come on you guys you have to remember the mobile connector plug is at a right angle to the wire. These covers are for straight connections.

 

[Jim R]

12 amps is the max the car will let you on 110V

If the cord is melting, it's possibly because of high current. It's not wrong to try to find out why. Check what the car is drawing. We all know it only draws 12 Amps when everything is working properly. But something is not working properly. One thing to check is what current is shown when you are charging.

 

[walla2]

The GFCI sounds like it's faulty to ewodrick's comment above. Replace the outlet and make sure the housing is properly installed and has all of the gaskets in place.

This shouldn't happen, the outlet should have tripped before it burnt the cord. Extension cords are used all of the time on power equipment drawing lots of amps on construction site. A Tesla Mobile charger will draw 12amps (really 11amps) on 120v. A 25ft 10ga extension cord can handle 20amps with no issues. Even at a 100ft, a 10ga extension cord can handle 20amp with a 4% drop in voltage. The issue most likely lies with the outlet and keeping the connection out of a standing puddle of water. Just my thoughts.

That's assuming it is a quality cable and not a "10 gauge" cable that is really a 14 gauge cable due to quality.

 

[walla2]

Driveway distance from outlet exceeds mobile connector cord length so using heavy 10 gauge 25ft extension cord.

Anybody else burning out extension cord wires?

But I still manage to fry cords. I'll get a notice the car has stopped charging and then see a black mark on the ground on the female side of the extension cord. The extension cord connector is clear so you can see the damage.

Lower the amps by 10%.

Check your outlet with an outlet tester. It may not be grounded or wired properly.

Check your GFCI. If not installed or working, add one at that outlet.

Use an outside box to seal the connection and to store your Mobile Charger like this one:

Amazon.com

Make sure your Mobile Connector adapter is clean and undamaged. Test Ohms / resistance with a multimeter.

Be safe.