Non-Tesla owner wants to rent a Tesla for a day, but questions...

[HRS2403]

I've just installed a Level 2 NEMA 14-50 receptacle in my garage for a future EV (or arc welder!).

1) I'm thinking of renting a Tesla on Turo for a day. I see from discussions here that if I just want to drive the car, the owner can lend me the keycard. If it's easy for the owner to add me as a driver, that would be fine. Do I have things correct?

2) As far as charging at home, I'd be using my Level 2 receptacle with the owner's Mobile Connector. Can I simply plug the connector into my receptacle, or is it more involved?

Thanks from a possible future Tesla owner...

 

[LoudMusic]

1) Easiest is probably the key card. Hold it against the door pillar to unlock the door. Lay it on the center console to enable driving. If you want the "phone as key" feature you'll need a Tesla account (free) and the Tesla app (free) and they need to invite you to be a driver on their car. It's fairly easy, but takes some patients.

2) They need the NEMA 14-50 adapter for the mobile connector. Your NEMA 14-50 outlet needs to be wired correctly using high enough gauge wire and connected to a 50A breaker.

 

[Sophias_dad]

1) If you have the card, put it against the door pillar a few inches below the camera and hop in and drive. You don't need to lay it on the center console(just behind the cupholders) unless you wait two minutes after opening the door, or get out of the car and back in without lock/unlocking.

2) If you are only renting for the day, you shouldn't need to charge at all. If you do need to charge, the 14-50 outlet only needs to be wired/breakered for 40 amps, since the mobile charger will take a maximum of 32 amps. Not all owners even have the 14-50 adapter.

 

[HRS2403]

Thanks to members LoudMusic and Sophias_dad for their quick answers.

Regarding charging, I do want to test my new setup—6/3 cable wired into a 60A breaker, then to a Hubbell 9450 NEMA 14-50 industrial receptacle. Despite almost a 100’ cable run, I still see 241 volts across the hot leads, which is a lot less voltage drop than I expected.

By the way, having roughed-in the Hubbell in a practice run (before the electrician did the actual installation), and seeing what the issues are with 6 gauge cable, I would never use any other brand. Yes, they’re expensive but the peace of mind is worth the extra few dollars. Alternatively, the Bryant version, identical to the Hubbell, is now available again at Grainger for $45.

 

[srs5694]

If you want to test either phone-as-key or level 2 charging at home, then you definitely need to talk to the car's owner before renting. Some owners may be reluctant to add lessees as authorized to use the phone-as-key functionality; and some may not have the NEMA 14-50 adapter (or even the Mobile Connector at all, since Tesla stopped including them as standard a while ago).

IMHO, testing charging at home isn't worth doing, especially not for a one-day rental, since it's not very interesting; it's like watching paint dry. It's the result you're after, not the experience, and it's not like the time required will vary unpredictably from one site to another, assuming all the locations have outlets with the same capabilities. If your outlet is wired correctly, there should be no problems; and if there are problems, you'd need to correct your wiring, no matter how you'd use it.

The phone-as-key functionality does vary more in reliability, so testing it before purchase might be slightly beneficial, but I'm not sure how much you'll learn, really. Broadly speaking, iPhones and newer Android devices work better than older Android devices. Some people also report problems depending on how they carry their phones. The car's Bluetooth antenna is in or near the left outside mirror, so if you carry the phone in your back pocket (especially your right back pocket), the signal the car receives may be weak, which can reduce reliability. Even when the phone-as-key functionality is unreliable, it's likely to be reliable enough that you might have a hard time judging just how reliable (or not) it is based on a one-day test drive.

Renting a car for a day or two for an extended test drive can certainly be worthwhile before buying, but you'll get more value from a Turo rental by driving the car on a variety of roads than by trying to charge at home or playing with the phone-as-key functionality.

 

[HRS2403]

If you want to test either phone-as-key or level 2 charging at home, then you definitely need to talk to the car's owner before renting. Some owners may be reluctant to add lessees as authorized to use the phone-as-key functionality; and some may not have the NEMA 14-50 adapter (or even the Mobile Connector at all, since Tesla stopped including them as standard a while ago).

IMHO, testing charging at home isn't worth doing, especially not for a one-day rental, since it's not very interesting; it's like watching paint dry. It's the result you're after, not the experience, and it's not like the time required will vary unpredictably from one site to another, assuming all the locations have outlets with the same capabilities. If your outlet is wired correctly, there should be no problems; and if there are problems, you'd need to correct your wiring, no matter how you'd use it.

The phone-as-key functionality does vary more in reliability, so testing it before purchase might be slightly beneficial, but I'm not sure how much you'll learn, really. Broadly speaking, iPhones and newer Android devices work better than older Android devices. Some people also report problems depending on how they carry their phones. The car's Bluetooth antenna is in or near the left outside mirror, so if you carry the phone in your back pocket (especially your right back pocket), the signal the car receives may be weak, which can reduce reliability. Even when the phone-as-key functionality is unreliable, it's likely to be reliable enough that you might have a hard time judging just how reliable (or not) it is based on a one-day test drive.

Renting a car for a day or two for an extended test drive can certainly be worthwhile before buying, but you'll get more value from a Turo rental by driving the car on a variety of roads than by trying to charge at home or playing with the phone-as-key functionality.

Thanks for the detailed response.

It looks the key card, by itself, is the likely way an owner would rent out his/her Tesla. That’s fine by me.

I just want to get a feel for the Tesla (whatever model is available). I’d have it overnight, so I would be charging it, whether needed or not to return the car, because I do want to see what the charging rate is and, frankly, just to try out what I just had installed. I’ll be sure to rent a car with the Mobile Connector included, with the NEMA 14-50 adapter.

 

[Watts_Up]

Thanks for the detailed response.

It looks the key card, by itself, is the likely way an owner would rent out his/her Tesla. That’s fine by me.

I just want to get a feel for the Tesla (whatever model is available). I’d have it overnight, so I would be charging it, whether needed or not to return the car, because I do want to see what the charging rate is and, frankly, just to try out what I just had installed. I’ll be sure to rent a car with the Mobile Connector included, with the NEMA 14-50 adapter.

You could rent a Model 3 or Model Y, or even Ford Mack-E and Polestar 2, from Hertz.
Using Hertz should be cheaper than Turo, however those EVs are mostly only available from major US international airports.
I recently rented a Model Y from SFO (San Francisco) for $375 a week and unlimited miles (after taxes and two drivers was $500.)
I used my own car insurance, and you only need to return thecar with 10% of charge.

I undestand that you will be able to charge at home, but would recommed installing on your phone some App such as
"ChargePoint" "PlugShare" "Volta" "EV Charging Points" "SemaConnect" .....
to find some L2 chargers around the places you park your car during the day or at night.
Typically, using an L2 charger you will get about 10% or 30 miles of charge for an hour of charging.
Note: Some L2 chargers are free (see "Volta") but often limited to 2 or 3 hours.

Get familiar with A Better Route Planner (ABRP), the Web page and the phone App.
This App will give you a good idea of finding super chargers during a trip.
- I you want to spend less time for charging, drive unil you reach 20% and don't charge more than 60%
- However, I prefer having a lesser number of charging stops and charge for a longer time,
so I try finding a Supercharger with amenities and restrooms.
Otherwise, instead of using ABRP, you need to seat in your car to use the Tesla navigation.
But the Tesla navigation works only from your current parking location.

 

[HRS2403]

That's a great option, but I don't live near a major airport. I've seen Teslas on Turo as low as $100/day, so that's likely my best choice.

 

[Sophias_dad]

I still see 241 volts across the hot leads, which is a lot less voltage drop than I expected.

Unless you actually had a >significant< load on it at the time, you should see essentially zero voltage drop.

 

[HRS2403]

Unless you actually had a >significant< load on it at the time, you should see essentially zero voltage drop.

You're right. In using a voltage loss calculator, 240V @1A @100' would have almost no voltage loss. 240V @50A @ 100', for instance, would calculate to a 1.88% loss, or a little less than 5 volts. I think the Tesla's screen would show the charging voltage, correct?

 

[swaltner]

Correct. You’ll see something very close to 240V on the screen as you first plug in. As the amperage increases, the voltage will drop by a few volts. The amperage is displayed on the screen as “current/maximum” (for the station you are plugged into or that your car supports). Something like 0/32, 20/32, 32/32, 40/40, 48/48, ….

Owner’s Manual: Model 3 Owner's Manual | Tesla

Charging Instructions: Model 3 Owner's Manual | Tesla

 

[HRS2403]

Thanks, swaltner, for the additional info.

 

[Rocky_H]

I do want to test my new setup—6/3 cable wired into a 60A breaker,

That is wrong and a code violation. The rating of the circuit breaker MUST NOT be higher than the rating of the outlet. That is a 50A outlet type, so the breaker must be no higher than a 50A. It won't do anything bad to the car, but it's a safety hazard. If something goes wrong, and too much current starts flowing, the wires can overheat while it might not trip the breaker yet because it's rated too high.

 

[HRS2403]

Yes, I hear you and had the same question for the electrician. He said it was OK since the 60A would derate by 80% to 48A courtesy of the charger, the maximum a Tesla Wall Connector can be set to deliver.

 

[Sophias_dad]

Yes, I hear you and had the same question for the electrician. He said it was OK since the 60A would derate by 80% to 48A courtesy of the charger, the maximum a Tesla Wall Connector can be set to deliver.

Maximum rating of 6AWG in an NMB cable is 55 amps, and that has to be derated to 44 amps for use with an EV charger. You are not supposed to be using it with a 60 amp breaker.

If it were 6AWG in conduit, or I suppose SOME prebuilt cables, it would be considered 65 amp capable, downrated to 52 amps for EV use.

 

[HRS2403]

Thanks again.

Well, it's 6/3 exposed Romex from the panel, about 75' to the garage wall. Then, at the wall exit point, about 12' of the cable unbundled to its individual wires in 1" metal conduit (so there's lots of air in the conduit volume for heat dissipation).

What I understand about the NEC (2017 here) is that, in my case, the 55A limit can rounded up to the next available breaker size, 60A.

 

[Sophias_dad]

What I understand about the NEC (2017 here) is that, in my case, the 55A limit can rounded up to the next available breaker size, 60A.

Not allowed to use that when you know for sure you'll be overloading the line continuously with an EV charger.

The 75' of romex makes that a 55 amp line, since you gotta go with the minimum rating. A few feet in conduit doesn't override the 75' of romex. Also, you aren't allowed to strip romex and put its individual wires through conduit.


Note: the NEC numbers are extremely conservative, but it doesn't mean that the insurance company will pay out if your house ever DOES burn down. All that said, I've been using my 48A HPWC on a 50 amp breaker and 6AWG romex for years without any issues(!)

 

[Rocky_H]

the maximum a Tesla Wall Connector can be set to deliver.

Wait, wait, what?! Why are you mentioning the wall connector? Earlier you said this was a 14-50 outlet:

I've just installed a Level 2 NEMA 14-50 receptacle in my garage

I've been basing my assessment and advice on this beginning statement, where you said it's a 14-50. So which is it? Is it a 14-50 or a hard wired wall connector?

OK, now to the rest of this electrical junk from the so-called "electrician. It's frustrating how many of these very black and white issues a professional is getting wrong.

Yes, I hear you and had the same question for the electrician. He said it was OK since the 60A would derate by 80% to 48A courtesy of the charger, the maximum a Tesla Wall Connector can be set to deliver.

This is worthy of a big ole FACEPALM. That is not at all how that works. This is thinking that you derate it to 48 and THEN apply it, saying, "Oh, 48 is less than 50. That's fine, right?" No, it isn't. Here's how the wording and the application of it actually works:
People usually do the ratio as 80% of the circuit rating, but the wording in NEC is actually done in reverse. It says you look at the constant current load (48A) and then you have to make the rating of the circuit be 125% of that. So then you have to make the circuit rated a full 60A if you are running it at 48A. There is no place for a 50A rated receptacle in this.

What I understand about the NEC (2017 here) is that, in my case, the 55A limit can rounded up to the next available breaker size, 60A.

Ugh, damn it. This mistake comes up over and over and over again. That principle gets used wrong so many times. There are a couple of reasons why this is wrong. "the 55A limit" is a limit on the capacity of the WIRE. It is not allowed to round up the capacity of the wire. That round-up provision is only for breaker sizes.

But now here's the other part. Someone gets this idea, where they say, "55 rounds up to 60", but then there is this knee-jerk reaction where they immediately get it in their head that someone has just waved a magic wand, and that every other part of the circuit is magically fully rated to 60A. That's not true. The rating still has to be limited by the lowest limit of any of the components. The cable is still only 55A limit rating, so it's still just a 55A circuit, so you can't run it as if it's 48/60. It's not a 60A circuit.

Good luck finding any charging equipment that you can actually configure as a 55A circuit, running at 44A continuous. So for almost anything you buy, you're probably going to have to choose for either a 50A or 60A rated circuit, and the 55A limit 6 gauge Romex just can't be used as if it's a 60A circuit.

 

[HRS2403]

Not allowed to use that when you know for sure you'll be overloading the line continuously with an EV charger.

The 75' of romex makes that a 55 amp line, since you gotta go with the minimum rating. A few feet in conduit doesn't override the 75' of romex. Also, you aren't allowed to strip romex and put its individual wires through conduit.


Note: the NEC numbers are extremely conservative, but it doesn't mean that the insurance company will pay out if your house ever DOES burn down. All that said, I've been using my 48A HPWC on a 50 amp breaker and 6AWG romex for years without any issues(!)

Well, I've done a little more research and you are correct. NM-B ("romex") cable's ampacity is in fact 55A. See the calculation below.

I'm going to get the electrician back to swap out the 60A breaker for a 50A.

 

[HRS2403]

Wait, wait, what?! Why are you mentioning the wall connector? Earlier you said this was a 14-50 outlet:

I've been basing my assessment and advice on this beginning statement, where you said it's a 14-50. So which is it? Is it a 14-50 or a hard wired wall connector?

OK, now to the rest of this electrical junk from the so-called "electrician. It's frustrating how many of these very black and white issues a professional is getting wrong.


This is worthy of a big ole FACEPALM. That is not at all how that works. This is thinking that you derate it to 48 and THEN apply it, saying, "Oh, 48 is less than 50. That's fine, right?" No, it isn't. Here's how the wording and the application of it actually works:
People usually do the ratio as 80% of the circuit rating, but the wording in NEC is actually done in reverse. It says you look at the constant current load (48A) and then you have to make the rating of the circuit be 125% of that. So then you have to make the circuit rated a full 60A if you are running it at 48A. There is no place for a 50A rated receptacle in this.


Ugh, damn it. This mistake comes up over and over and over again. That principle gets used wrong so many times. There are a couple of reasons why this is wrong. "the 55A limit" is a limit on the capacity of the WIRE. It is not allowed to round up the capacity of the wire. That round-up provision is only for breaker sizes.

But now here's the other part. Someone gets this idea, where they say, "55 rounds up to 60", but then there is this knee-jerk reaction where they immediately get it in their head that someone has just waved a magic wand, and that every other part of the circuit is magically fully rated to 60A. That's not true. The rating still has to be limited by the lowest limit of any of the components. The cable is still only 55A limit rating, so it's still just a 55A circuit, so you can't run it as if it's 48/60. It's not a 60A circuit.

Good luck finding any charging equipment that you can actually configure as a 55A circuit, running at 44A continuous. So for almost anything you buy, you're probably going to have to choose for either a 50A or 60A rated circuit, and the 55A limit 6 gauge Romex just can't be used as if it's a 60A circuit.

See my response to Sophias_dad above. I was misinformed by the electrician that a 60A breaker would be allowed. I'm going to revert to a 50A.

It's a NEMA 14-50 now, with 6/3 gauge NM-B. I was thinking ahead to the possibility of changing out the NEMA for a Tesla Wall Connector, with its max 48A charge current. (60A 80%-derated to 48A). Yes, the electrician should have known better.

So, it's back to a NM-B-compliant 50A breaker, and a 40A max charge rate with the Wall Connector.