Help thinking through new Model 3 charging options

[FastEddieB]

My wife and I should be taking delivery of a Model 3 LR in the next month or so.

As background, we've been driving a 2018 Honda Clarity PHEV for over 3 years and now have about 62,000 trouble free miles on it. With an average of 47 miles EV range, almost all our local driving is all or majority EV. Road trips in hybrid mode yield about 42 mpg, which is great for a car this size. We can usually top off the battery overnight on a standard 120v receptacle, even at a rate of about 4 mrph.

But we have a 240v 30A receptacle we can plug our stock EVSE into via a home made adapter, which draws 16A and ups the mrph to about 10. It's a twist-lock generator receptacle which normally powers a hangar door.

That way in a power failure we can still get the hangar door open by plugging the door into our 240v generator. Here it is charging the Clarity:

I plan on using this feed for the Tesla. I'm considering "piggy-backing" a 240v 30A receptacle onto the existing generator receptacle, just being careful never to operate the hangar door while charging. Or possibly putting a selector switch in, though that introduces a lot of new failure points. These are the two receptacle styles I'm considering:

A couple questions:

1) Anything to make either the 10-30 or the 14-30 preferable? Clearly on the 14-30 one blade would remain unused.

2) There are only 3 wires running to the location, 2 hots and a ground, no neutral. Clearly the Tesla EVSE doesn't need a neutral, since there are adapters for several 3-prong plugs in their lineups. But the 10-30 receptacles I'm seeing say "No Ground Contact".

Am I right is assuming that it will work OK wired with 2 hots and a ground? Sure seems like it should.

I know a lot of what I'm proposing might not be to code. I just want to be sure I'm on the right track and not proposing anything unsafe.

As an aside, short term I could use the adapter below and continue as I've been doing, unplugging the hangar door when using the receptacle to charge, but it seems kind of inelegant.

And as a further aside, we do have 2 14-50 receptacles on RV panels about 100' from the house, and could always use one of those on the very rare occasion we needed an even faster charge.

Thanks in advance - I know that was a lot!

 

[jjrandorin]

I cant provide you any technical assistance, but in general I would say "whatever you are currently doing to charge the current plug in hybrid should work for this car as well".

 

[davewill]

Are you planning to use it for charging every day? If so, I'd run a new circuit rather than use any of those workarounds, personally. I definitely wouldn't do anything that wired two outlets onto the one circuit.

You're right that none of those outlets (the original twist lock or the two you're considering) are correct for a 3 wire grounded circuit. The correct outlet would be a 6-30 (or L6-30 for twist lock), but Tesla doesn't make an adapter for it. EVSEadapters.com does though.

 

[Rocky_H]

Damn. All my internet points today to @davewill for telling you that none of the options you're considering are decent at all.

You never even told us directly what your original outlet is, but then indirectly showed that L14-30 adapter. That is dangerous having any 14-XX type of outlet with missing neutral, so what you've got right now is wrong.

10-30 isn't an option, because NEC hasn't allowed any new 10-XX series outlet to be installed since 1996.

And 14-30 has the same problem your existing L14-30 has. It's a 14-XX with a missing neutral, which you should never have.

You should do a 6-30, which is exactly what outlet should be used with three wires of hot, hot, and ground. It's dumb that Tesla doesn't sell an OEM adapter for that, but EVSEAdapters does, so I would get one of theirs.
(Oh, ugh. You said you need to keep that outlet to use a generator output to drive into it. If your generator has a L14-30 output, why did you put in an incorrectly installed L14-30?)

Are you planning to sell that Honda Clarity with that charging cable along with it? Because if you're keeping that too, you could just not change anything at all, and keep using that same charge cord for both the Honda and the Tesla. All Teslas come with a little snap-on adapter for J1772 charging handles, like that cord has.

 

[FastEddieB]

Thank you for the replies! I’ll do my best to post a detailed response some time tomorrow.

 

[Gauss Guzzler]

I'm not sure it's dangerous to have an outlet with a missing neutral. I think it'd just be frustrating if you plugged in a multi-voltage appliance and it didn't work.

Otherwise, I agree with the folks above, 6-30 is the right outlet, and it's dumb (but fine) that you have to go aftermarket for the adapter.

The only thing you proposed that *is* dangerous is the plan to unplug/swap frequently with the door. Kick that idea off your back burner. And as far as code compliance goes, I think you're fine-ish. Code requires EV circuits to be dedicated and also requires new circuits to be GFCI protected, but just daisy-chaining a 6-30 onto your code-violating L14-30 is kinda fine.

 

[davewill]

A missing neutral is dangerous. For example, if you plug an RV or some other adapter that splits into 120v plugs into it, current can flow through two 120v appliances that are plugged into the opposite hot legs and the shared, but unterminated neutral wire. With the shared neutral floating at whatever voltage, you can damage the appliances, or end up with a hot chassis, creating a shock hazard.

 

[Rocky_H]

I'm not sure it's dangerous to have an outlet with a missing neutral.

A missing neutral is dangerous.

Here's one way where someone could get a shock from a neutral if it's supposedly there, but the connection gets broken somewhere.

But this is more of the situation that applies here, which is what @davewill mentions:

If someone plugs in something that is expecting the neutral so it has the two separate 120V circuits what happens is that you get two sides with 240V across it, but nothing in the middle to anchor that to keep it even at 120V on each side. If the resistances are different on the two sides, the voltage on them can swing wildly, so you may get 200V on one side and 40V on the other side, for example. Some regular appliances made for only 120V may spark or melt with an unexpected very high over-voltage.

 

[FastEddieB]

Thanks for all the feedback. A lot to think about. Fortunately My EDD is currently 2/19 to 3/19, so I still have time to digest.

I want to make clear how I arrived at my Clarity charging options...

All this precedes charging an EV. Our Hangar/Home has a 42' hangar door. It's powered by a 240v, 30A circuit (though it says 230v Single Phase - I always get confused by the 220/230/240 and 110/115/120 nomenclature that seems almost randomly interchangeable).

It consists of two "hots" and a ground, and was installed as hard-wired. The door came with an emergency hand crank that seems ridiculous - it would take a LONG time and a lot of muscle to crank it up, and the crank is on the motor that goes up with the door as it opens, necessitating cranking from a ladder to a a height of 10-15'! Not really practical.

So I came up with the idea of getting a generator capable of 240v out at enough output to open the door in an emergency. The company said 10kW should be more than enough, so that's what we got. It's 240v output is via an L14-30 twist-lock receptacle. So, I had the idea to remove the hard wiring to the hangar door and instead to route it to the L14-30 receptacle show in my first post. I then installed to the hangar door a cable long enough to reach the generator and put an L14-30 plug on it. The scenario is: power failure, unplug the hangar door from the wall mounted L14-30 receptacle, plug it into the generator and, voila', door comes up - and it works. Again, the L14-30 expects a neutral, but none is used or needed for the hangar door, so it's not hooked up. I put the warning label on it to remind anyone that thought the receptacle might appear to contain a neutral, that it doesn't. Certainly not to code, but as long as its just being used for the hangar door by us, no conceivable safety hazard.

Sorry if that was long winded. I'm going to take a break and then try to make clear how that same receptacle came to be used for charging our Clarity @ 240v.

As an aside, this is our hangar/home. We have 1,350' of living space, which is more than enough for just the two of us.

We normally charge with the Clarity in front of the smaller garage door, plugged into either 120v or 240v depending on how fast we need to charge.

 

[Rocky_H]

Whoa, that is a cool house setup.

The company said 10kW should be more than enough, so that's what we got. It's 240v output is via an L14-30 receptacle.

I'm just not a fan of having non-compliant outlets installed in a building. So what I would lean toward is more of switching the outlet in the building to a compliant 6-30 and getting a little pigtail adapter cord to fit it to your generator. Here's an example of what I mean.

StackPath

It's an L14-30 receptacle on one end and a 6-30 plug on the other end. So that could basically stay permanently on the end of your generator cable.

And EVSEAdapters sells a 6-30 plug for the Tesla cable.

NEMA 6-30 Adapter for Tesla Model S/X/3/Y Gen 2 – EVSE Adapters

www.evseadapters.com

Or of course you could go with the locking L6-30 on both of those adapters if you wanted.

 

[miimura]

Whoa, that is a cool house setup.

I'm just not a fan of having non-compliant outlets installed in a building. So what I would lean toward is more of switching the outlet in the building to a compliant 6-30 and getting a little pigtail adapter cord to fit it to your generator. Here's an example of what I mean.

StackPath

It's an L14-30 receptacle on one end and a 6-30 plug on the other end. So that could basically stay permanently on the end of your generator cable.

And EVSEAdapters sells a 6-30 plug for the Tesla cable.

NEMA 6-30 Adapter for Tesla Model S/X/3/Y Gen 2 – EVSE Adapters

www.evseadapters.com

Or of course you could go with the locking L6-30 on both of those adapters if you wanted.

I will second the suggestion to change the plug for the hangar door and the outlet to NEMA L6-30.
This is the correct adapter to plug the hangar door into the generator after the conversion:

StackPath

This is the Mobile Connector adapter for the L6-30:

L6-30 Adapter for Tesla Model S/X/3/Y Gen 2 – EVSE Adapters

www.evseadapters.com

 

[FastEddieB]

Whoa, that is a cool house setup.

I'm just not a fan of having non-compliant outlets installed in a building. So what I would lean toward is more of switching the outlet in the building to a compliant 6-30 and getting a little pigtail adapter cord to fit it to your generator. Here's an example of what I mean.

StackPath

It's an L14-30 receptacle on one end and a 6-30 plug on the other end. So that could basically stay permanently on the end of your generator cable.

And EVSEAdapters sells a 6-30 plug for the Tesla cable.

NEMA 6-30 Adapter for Tesla Model S/X/3/Y Gen 2 – EVSE Adapters

www.evseadapters.com

Or of course you could go with the locking L6-30 on both of those adapters if you wanted.

Thanks for the compliment on our hangar/home. We call her “Wingin’ It” since the final result was drastically different from our original plan, which was to throw up a simple “pole barn with a bathroom” and later building a freestanding 1,200+ sq ft home. In the end it did work out really well.

Your first link was to a 15A adapter, so that wouldn’t meet our needs.

But I am intrigued with the idea of switching out my existing receptacle and hangar door plug with more appropriate ones designed for 2 hots and a ground, and making an adapter for the extremely rare instance of needing the generator to power the door.

I did go ahead and order the 14-30 twistlock to Tesla EVSE adapter to use at least initially. I‘m aware of the undesirability of plugging/unplugging on a regular basis, but at least over the last 2 years or so that’s what I’ve been doing to no ill effect. Yet.

Decision, decisions.

 

[3sr+buyer]

Could you just get an electrician to install a 14-50 or 6-50 outlet on a 40A or 50A circuit near where you charge the car (separate from the hangar door outlet)?

Then get the 14-50 or 6-50 adapter for the mobile connector EVSE that will come with the Tesla and hang the mobile connector EVSE in the garage to charge the Tesla. Perhaps add a Tesla->J1772 adapter ( 5 Best Tesla to J1772 Adapters that easily charge non-Tesla EVs • Expert Guide ) if you also want to charge the Clarity with it.

Between 14-50 and 6-50, 6-50 may be slightly less expensive (one fewer wire), but 14-50 appears to be more common as an EVSE plug, and is also the same as what are probably the most common RV park outlets.

 

[Rocky_H]

Your first link was to a 15A adapter, so that wouldn’t meet our needs.

Oh, whoops, I clicked a Google link that said 6-30, but when it opened, and I copied the page, I didn't look carefully to notice that it had the wrong product type there and was a 6-15--sorry.

Could you just get an electrician to install a 14-50 or 6-50 outlet near where you charge the car (separate from the hangar door outlet)?

I don't see any reason at all to need to run new wire for an entirely new line. He already has a totally fine 240V 30A circuit. It's perfectly usable, and there's no need to add an extra circuit.

 

[FastEddieB]

I don't see any reason at all to need to run new wire for an entirely new line. He already has a totally fine 240V 30A circuit. It's perfectly usable, and there's no need to add an extra circuit.

Especially since we have two 240v 50A 14-50 receptacles on RV pedestals about 100’ from our house in a fenced RV yard. Not real convenient, but there for the rare occasion when 30 mrph would provide a benefit over the 20 or so we expect from our 240v 30A hangar door service.

Also, conveniently I have a friend with 2 Tesla’s who’s pretty sure he has an extra 14-50 Tesla adapter I can just have. If it’s free, it’s for me!

 

[Rocky_H]

Also, conveniently I have a friend with 2 Tesla’s who’s pretty sure he has an extra 14-50 Tesla adapter I can just have.

I'm not sure if you are aware or your friend is aware of the older and newer mobile connectors. The adapters are different, so if he has an older cable, that adapter wouldn't fit your newer cable. But if his cars are fairly new, like about 2018 or newer, then that should have come with the newer Generation 2 cable like yours, and the adapter would work. If you look in Tesla's store, you can see what the Gen1 versus the Gen2 adapters look like to know if what he has will fit yours or not.

 

[FastEddieB]

Are you planning to use it for charging every day?

Good question.

With our PHEV Honda Clarity, we charge daily, so as to always start out with a full battery. Though running out of EV range in a non-event, our goal is to run electric as much as possible.

Our usual driving pattern is less than 40-50 miles a day when local, running errands, going to soccer games, that sort of thing. Though we won’t be locked into any particular charging regimen, 2 come to mind…

1) Charge daily to 80% or so. With our driving habits that could easily be done overnight even with a standard 120v outlet.

2) Just drive during the week. It would be rare to drive more than 100 to 200 miles over the course of a week. Then, just choose a weekend day to overnight charge @ 240v 30A to get back to 80%.

Either one would work. What’s your guess as to what pattern we‘ll fall into?

 

[Rocky_H]

Either one would work. What’s your guess as to what pattern we‘ll fall into?

Likely some hybrid between the two, just because human nature. We do pretty low miles per day, maybe 15 or 20. I just don't want to bother with it every single day for such trivial amounts, but I also don't want to be too low, where something comes up and I need more. So we'll go two or three days sometimes, and when it's down around 120-130ish rated miles, that's around half full on ours, and we'll plug it in again.

 

[Gauss Guzzler]

You only have about 150 miles of range within the comfortable 20%-80% battery state so with your usage you'd likely want to charge every 3-4 days, not every 7.
And if you bring that up to every 2-3 days you might even be fine on 120V.

 

[davewill]

My feeling is that if you don't charge every day, sooner or later, you're going to want to take a longer trip and find yourself short of battery without enough time to charge up. If you have Supercharging available to supplement that might not be a deal breaker (but it's definitely annoying). For myself, I consider a 240v 20-30a daily plug in to be a minimum requirement.

If you are trying to make 120v work, I would expect you should be plugged in every minute you are home.