Leave plugged in outside for a week?

[duanra]

The extension cord will cause slowier charging as far as I know...

 

[Vines]

The simple point is that the UMC detects insufficiency circuit gauge by detecting an increase in resistance, which will spike as heat increases.
An extension cord simply adds length to the existing wiring. It its gauge is sufficient then it’s no problem. If it’s gauge is not sufficient then the UMC will act exactly the same as if it were plugged into sub-code household wiring.
On other words, it’s “rubbish” to say that an extension cord bypasses the UMC shut-off mechanism, which was the content of my post.

Its my understanding that both a resistance check and a temperature check are part of the UMC circuitry. While they are related, I do not believe they are the same sensor. YMMV
I do believe there is a good reason why Tesla says not to use the extension cord. If you know better that's your prerogative.

 

[TexasEV]

The extension cord will cause slowier charging as far as I know...

Only if the gauge is inadequate and you have to turn down the amps. Use a 10 or 12 gauge cord for 120V 15A circuits and you won’t have any problems as long as the car still lets you draw 12A.

 

[duanra]

It is something i noticed. I plugged once with about 10m extension and it slowed down the charging. Than I tried a 5 m extension and it was less significant. What i notice is that the length of the cord was affecting the voltage number. Does it make sense ?

 

[jerry33]

It is something i noticed. I plugged once with about 10m extension and it slowed down the charging. Than I tried a 5 m extension and it was less significant. What i notice is that the length of the cord was affecting the voltage number. Does it make sense ?

Yes, unless it was a heavy extension cord. Resistance increase with length of travel for a given size wire. A too light extension cord will either cause the charging to slow down or stop it altogether (activating the red light on the UMC).

 

[Shock-On-T]

Its my understanding that both a resistance check and a temperature check are part of the UMC circuitry. While they are related, I do not believe they are the same sensor. YMMV
I do believe there is a good reason why Tesla says not to use the extension cord. If you know better that's your prerogative.

Tesla knows better than to recommend an extension cord to the general public, because an inescapable percentage of them are clueless.
If Tesla has sold 500,000 cars, then 5,000 of those cars are being driven by the dumbest 1% (that's Science, people!).

The UMC doesn't measure line resistance, but rather voltage. The voltage sags as resistance rises. The resistance rises as the line gets warmer. If it gets too warm, the voltage falls below a cut-off and the UMC shuts down. Nice and safe. If you use correctly gauged extension cords there is no danger, no more than plugging in a fan heater.

In fact a fan heater would be much more dangerous than a Tesla, because the fan heater will keep merrily pulling current through a burning socket as long as it can, whereas the UMC will shut down as it gets warm.

As a fun experiment the next time you are in your garage, check your charging voltage at 1 amp, then check it again at max amps. This will tell you how good the wiring is from your meter box to your garage. If it drops more than about 3% then your house wiring is only barely adequate.

 

[centikel]

Plugged in Tesla is a happy Tesla. That being said, lol, I don’t charge every night. If you use an extension cord don’t be cheap. Use a heavy duty extension cord, as short as possible. Some Ridgid models have an integrated fuse.

Excellent suggestion for a cord! Thanks!

 

[centikel]

Tesla knows better than to recommend an extension cord to the general public, because an inescapable percentage of them are clueless.
If Tesla has sold 500,000 cars, then 5,000 of those cars are being driven by the dumbest 1% (that's Science, people!).

The UMC doesn't measure line resistance, but rather voltage. The voltage sags as resistance rises. The resistance rises as the line gets warmer. If it gets too warm, the voltage falls below a cut-off and the UMC shuts down. Nice and safe. If you use correctly gauged extension cords there is no danger, no more than plugging in a fan heater.

In fact a fan heater would be much more dangerous than a Tesla, because the fan heater will keep merrily pulling current through a burning socket as long as it can, whereas the UMC will shut down as it gets warm.

As a fun experiment the next time you are in your garage, check your charging voltage at 1 amp, then check it again at max amps. This will tell you how good the wiring is from your meter box to your garage. If it drops more than about 3% then your house wiring is only barely adequate.

Can’t wait to test this out!

 

[tga]

Tesla knows better than to recommend an extension cord to the general public, because an inescapable percentage of them are clueless.
If Tesla has sold 500,000 cars, then 5,000 of those cars are being driven by the dumbest 1% (that's Science, people!).

The UMC doesn't measure line resistance, but rather voltage. The voltage sags as resistance rises. The resistance rises as the line gets warmer. If it gets too warm, the voltage falls below a cut-off and the UMC shuts down. Nice and safe. If you use correctly gauged extension cords there is no danger, no more than plugging in a fan heater.

In fact a fan heater would be much more dangerous than a Tesla, because the fan heater will keep merrily pulling current through a burning socket as long as it can, whereas the UMC will shut down as it gets warm.

As a fun experiment the next time you are in your garage, check your charging voltage at 1 amp, then check it again at max amps. This will tell you how good the wiring is from your meter box to your garage. If it drops more than about 3% then your house wiring is only barely adequate.

You missed the point. There are two things being measured. Total voltage drop as the current ramps up, and temperature at the plug. A circuit that is otherwise OK but has a loose connection at the outlet could cause enough localized heating to cause outlet damage/fire without causing enough of a drop to trip the voltage drop alert. The voltage drop detection has reduced, but not eliminated, outlet fires; we still see reports of outlet fires on TMC. Using an extension cord in this case separates the temp sensor in the plug from the defective outlet, preventing the temp sensor from tripping.

 

[Rocky_H]

Only if the gauge is inadequate and you have to turn down the amps. Use a 10 or 12 gauge cord for 120V 15A circuits and you won’t have any problems as long as the car still lets you draw 12A.

Tesla is better off telling people to not use them. Wire gauge is so vital and something that most people just aren't familiar with. They see cords that are "heavy duty" and "outdoor" and "thick", and they think those should be good. I had a 10 foot and a 50 foot extension cords at home, and they both were really thick, so I thought one of those would probably be solid enough to use for charging, but I checked the gauge stamped into them, and they were both 16 gauge!

 

[TexasEV]

Excellent suggestion for a cord! Thanks!

No it wasn’t. “Heavy duty” is meaningless. That’s why numbers were invented and wire is measured by gauge. Use a 10 or 12 gauge cord only.