Model 3 RWD with Tesla Mobile Connector?

[user47592]

Just had my RWD for a week now.

Charging with the 5-15 for now.

I'm a little confused. Thought I would need to get a NEMA 14-50 outlet installed in the garage. But the RWD handles only 32 amps max for charging.

Do I go with the 14-50 because I'm under the impression that it feeds 40 amps continuously?

Thanks.

 

[jjrandorin]

Im not sure of the question. A 14-50 is a power outlet, just like any other power outlet in your home (although this one provides more power). The device being plugged in determines what amount of power it needs. The fact that a 14-50 can provide 40amps, but the car can only take a max of 32amps doesnt mean you cant use a 14-50.

You go with whatever power outlet you want to install, that fits within the amount of power available in your panel.

 

[DuncanM]

Just had my RWD for a week now.

Charging with the 5-15 for now.

I'm a little confused. Thought I would need to get a NEMA 14-50 outlet installed in the garage. But the RWD handles only 32 amps max for charging.

Do I go with the 14-50 because I'm under the impression that it feeds 40 amps continuously?

Thanks.

A 14-50 is still a good choice for supplying a continuous 32 amps. However, if your 5-15 is being fed via 12-2 wire and a 20amp breaker, you could replace the outlet with a NEMA 5-20 and with the correct TMC connector to charge at 120v/16amps. Alternately, if the 5-15 is being fed via 12-2 wire and is the only outlet on that circuit you could replace the breaker with a 20amp 240v breaker and the outlet with a NEMA 6-20 and then charge at 16amps/240v. I opted to add a 20amp 240v breaker in our vacation home garage subpanel and then run 12-2 wire from the subpanel to a NEMA 6-20 outlet. This only cost me ~$70 in parts.

 

[Cosmacelf]

Just had my RWD for a week now.

Charging with the 5-15 for now.

I'm a little confused. Thought I would need to get a NEMA 14-50 outlet installed in the garage. But the RWD handles only 32 amps max for charging.

Do I go with the 14-50 because I'm under the impression that it feeds 40 amps continuously?

Thanks.

Yes, the Mobile Connector only handles 32A even though it has adapters for 50A receptacles. And the Model 3 RWD can only charge at a max of 32A as well.

So to get your full 240V charging speed, you would indeed install a NEMA 14-50 receptacle.

 

[Tronguy]

OK, there's a little confusion here.

First off: The Tesla Mobile Connector has never supported doing more than 32A @ Any_Voltage.

But there's a bit more to it than that. Take the following with a small grain of salt.

If one looks through the list of available NEMA connectors one will notice that there's 15A connectors, 20A connectors, 30A connectors, and 50A connectors. There are, notably, no 40A connectors.

As it happens, there are objects like clothes driers and electric stoves that need 40A.

There's this general NESIC (That's the National Electric Code standard) rule: The amperage of a breaker in a breaker panel, the gauge of the wire used to convey that amperage, and the socket must match. It's actually legal to have a wire gauge larger than what's required, but not smaller.

The problem: Copper Costs Money. If one has an electric stove with a 40A requirement and one has to use a connector that can supply 40A, a 50A connector is all that one has. And that means, generally, using wire that has a 55A rating. (For various reasons, there's no copper available that's dead-on 50A.) Electricians hate spending money on copper. So, somehow, into the NESIC came this exception: If you have a 40A load, you can use a 40A breaker, 40A wire... and a 50A NEMA14-50 connector.

I don't know the full details. I'm guessing that the socket has to be labeled that it's a 40A load only, even if it does have that 50A look to it. But electricians Far and Wide have gotten really used to the idea that, when faced with a 40A load, they use 40A wire, 40A breaker, and that NEMA14-50.

Just to finish this off before we start the fun: If one has a constant, heavy load (hello, electric range and Tesla car!) one is not allowed to suck down more than 80% of the breaker/wire/socket rating. So, for a 50A circuit, this means a maximum of a 40A load. For a 40A circuit, this means a maximum of a 32A load.

So, imagine Tesla's problem: They have Zero Idea as to whether that NEMA14-50 one has plugged the Tesla Mobile Connector into has a 40A breaker and wire backing it up or a 50A breaker and wire backing it up. So, fairly obviously, they went for the Safe Option: Don't draw more than 32A on a 50A socket.

Couple more points, just so you know what you're working with, here. Amperage limits on wire are all about the heat. Power dissipated in a hunk of wire goes as Current*Current*Wire_Resistance. Note the "square" factor here. That goes into thermal energy. Which makes the wire warm. Heat energy flows away by radiation (hello, infrared!) and conduction, where conduction can include air circulation and physical contact. People with tons more experience and PhDs than any one of us here have placed wire in conduit, typical wall construction, and what-all and measured the temperature that the copper wire gets up to. Warm enough and it makes the insulation and such degrade. Degrade enough and insulation stops being an insulator, and Fires R Us. Ambient temperature and industrial vs. residential matters.

Finally.. that breaker in the breaker box is there for an emergency. Run 120%, 200%, 400% more than what said breaker is rated for and it'll pop and save the day. Running it right at its limit is frowned upon because, in almost all breakers, the widget that trips the breaker is thermal in nature: that is, it expands and pops the breaker. Even if a running 40A through a 40A breaker might not pop said breaker right off (or after an hour or so), it certainly is going to make that thermal element flex. Enough flexure over time and, well, in the case of a real emergency, said thermal element might not work. So, one needs to respect that 80% limit, they're not kidding.

A bit more. If one has a Tesla Wall Connector or the equivalent from $RANDOM_MANUFACTURER, it is presumed that one is not an idiot and is not using the wrong gauge wire for what one is doing. I happen to have a Gen II TWC in the garage; it's hardwired to a 60A circuit (breaker and wire), and so I can get the Teslas in the garage to charge at 48A, no problem. (48A being 80% of 60A). Likewise, if one has a 50A circuit, it's no problem setting the TWC (or equivalent) to that amperage value and charging at 40A. And so on.

Questions? We got answers.

 

[davewill]

OK, there's a little confusion here.

First off: The Tesla Mobile Connector has never supported doing more than 32A @ Any_Voltage.

...
Questions? We got answers.

Actually, the Tesla Mobile connector Gen 1 supports 40a charging on 50a outlets. Also, the Tesla corded wall connector, which still seems to pop up on the Tesla store, also supports 40a on a 14-50.

To make things more confusing, in Canada, after supporting 40a on 50a outlets for years, Tesla decided to change their adapters to be limited to 32a, and even swapped out existing adapters for people. We can only speculate on the reasons, but the prevalence of 40a circuits with 50a outlets is likely a contributor.

 

[Tronguy]

Actually, the Tesla Mobile connector Gen 1 supports 40a charging on 50a outlets. Also, the Tesla corded wall connector, which still seems to pop up on the Tesla store, also supports 40a on a 14-50.

To make things more confusing, in Canada, after supporting 40a on 50a outlets for years, Tesla decided to change their adapters to be limited to 32a, and even swapped out existing adapters for people. We can only speculate on the reasons, but the prevalence of 40a circuits with 50a outlets is likely a contributor.

I stand corrected, somewhat.

 

[davewill]

I stand corrected, somewhat.

In general, I agree with your post. I wouldn't have replied at all if you hadn't said "never" with emphasis.

Going one step further, for those of us who have 40a circuits on 50a outlets, the older mobile connector was kind of a non-starter as you couldn't get an adapter that would work with your outlet. (Later on, third parties popped up with modded ones.)

 

[Cosmacelf]

In general, I agree with your post. I wouldn't have replied at all if you hadn't said "never" with emphasis.

Going one step further, for those of us who have 40a circuits on 50a outlets, the older mobile connector was kind of a non-starter as you couldn't get an adapter that would work with your outlet. (Later on, third parties popped up with modded ones.)

Yeah I remember when Tesla changed the mobile connector to only draw 32A and everyone was up in arms about not being able to draw 40A. But it was absolutely the right move for the reason you stated, and also most 50A receptacles are garbage and can’t handle even 40A continuous when being used every night.

 

[davewill]

Yeah I remember when Tesla changed the mobile connector to only draw 32A and everyone was up in arms about not being able to draw 40A. But it was absolutely the right move for the reason you stated, and also most 50A receptacles are garbage and can’t handle even 40A continuous when being used every night.

I agree, although I always thought the move had as much to do with making the Gen2 TMC smaller and lighter as it did with any safety concerns.

 

[Cosmacelf]

I agree, although I always thought the move had as much to do with making the Gen2 TMC smaller and lighter as it did with any safety concerns.

That too! They did add some more expensive safety features though like thermal monitoring in the plug, and the adapters themselves cost more in raw materials. But there's no doubt they manufacture cost optimized the gen2 to make it cheaper to build even with all that extra stuff. Hugely increased volumes and probably bringing some of it in-house no doubt also helped.

The Mexico gigafactory isn't only going to be used for vehicle production, I expect it'll also be used for a lot of these other parts.

 

[3sr+buyer]

most 50A receptacles are garbage and can’t handle even 40A continuous when being used every night.

Probably not most in terms of available brands/models, but one very common brand/model tends to have poor conductivity at the plug contacts (which are half size steel instead of full size brass), leading to excess heat generation. That brand/model may be common due to its compact size which avoids requiring a larger or special outlet box.

 

[BSparx]

Interesting discussion about 70 amps vs 50 amps vs 40 amps vs 32 amps, all at 240 volts.

Bottom line is that most owners will not notice the difference when charging overnight. The car will be ready to go at the designated go time tomorrow morning.

So to the OP, when you get that new charging circuit installed choose any of the 240 volt options. Keep in mind a big piece of the installed cost is the labor. For that reason I would go for the biggest amp rating my electrical panel can handle as the incremental cost of bigger wire and breakers may be small. Talk to your electrician about this. Also keep in mind future proofing. You might well want another EV the future that can charge at higher rates than the current M3.

 

[user47592]

Thanks guys! Lots of great information here. I'm sure others will find it useful as well.

I ended up opening up a 15amp outlet thinking there's a chance the 20amp breaker was wired to there. But upon opening, I saw white wiring. I was told white is for a 15amp circuit and yellow is for 20amp. It would have been nice if it was yellow wiring and I could have changed out the outlet to get just a bit of a boost.

I go with getting the 14-50 installed. Unfortunately, the electrician that I want to go with isn't available for a few months. Luckily, I can get by with the 115v for now.