Nema 14-50 to L6-20?

[RVD98072]

I have a Tesla coming and my home has an existing L6-20 outlet in the garage. I know that it's not great since it's only 240v 20 amps so it will only charge at around 16 amps but it's a lot better than 120v charging. It worked out well for me when I had a Nissan Leaf.

I'd like to at least start by trying it out before paying to get a real 14-50 outlet installed.

Any advice? I was thinking of buying or building a 14-50 to L6-20 adapter (evseupgrade sells one for around $60) but then I'd have to make sure to manually set the amps in the car to 16 amps. I probably won't forget by my wife probably will forget and don't want to cause any problems or trip circuits to frequently.

Of course I'm guessing it's more dangerous but I can rewire the receptacle from L6-20R to 14-50 but then I'd also have to make sure that nobody else inadvertently tries to charge 40 amps from that outlet. This would be cheaper than buying or building an adapter.

Is there any way to put a limiter (resistor) to limit the jack to only output 16 amps no matter how much the charger is trying to pull?

The wires are too thin gauge to simply replace the circuit to 50 amps and would be costly to upgrade as it runs a good 25 feet+ up the ceiling, etc.

 

[swaltner]

First, DO NOT SIMPLY REPLACE THE OUTLET WITHOUT REPLACING THE UNDERLYING WIRE AND BREAKER! You are asking for trouble doing that. You won't pass an inspection and you would give your insurance company reason to deny a claim for fire damage it you simply replaced the outlet and didn't bother with an inspection.

You don't say if you're using a Model S/X or Model 3 mobile connector.

If you're using an S/X adapter: I'd suggest making an L6-20 plug to 5-20 socket adapter and then using the NEMA 5-20 adapter from Tesla. Be sure to mark this adapter as "Tesla Charging Only". You wouldn't want to plug a 120V only device into the 240V outlet.

For the Model 3 mobile connector, make an L6-20 plug to 6-20 socket adapter and get the Tesla 6-20 adapter.

There's a long thread here somewhere about making these adapters.

Personally, I don't like any adapter that lets you plug a high-amperage device into a low-amperage upstream outlet. Anytime you do this, there is added risk. It's a manageable risk, but it is there. You may be aware of the issues related to using those adapters, but will your spouse/children/grandparents/friends all understand the nuances of using the adapter (always reduce the amperage)? Forcing the use of the standard Tesla adapters makes it so you or someone else can't forget to do that critical step one time.

 

[TexasEV]

What worked for you with a Leaf doesn’t necessarily translate to having a Tesla. A car with 250 or 300 mile range is a different experience, and you’re not going to be able to take advantage of that difference (which you’re paying high 5 figures or six figures for) unless you can charge your car fully overnight. I suggest you bite the bullet and have a 14-50 outlet installed. Just consider it as part of the price of buying the car.

 

[SSedan]

I believe the car will GPS remember the amperage setting so you don't have to set it every time.

 

[TexasEV]

I believe the car will GPS remember the amperage setting so you don't have to set it every time.

Until it doesn’t.

 

[RVD98072]

Thanks! I'll explore the route of going L6-20 to 5-20 and then using a Tesla adapter.

I'd like to try this and think that it might work because my office has free charging so I can charge at 240v 6.6kw all day long for free. Because of this perk, the only time I actually charged at home was on weekends.

This is for the model X mobile charger.

 

[Rocky_H]

Thanks! I'll explore the route of going L6-20 to 5-20 and then using a Tesla adapter.

Yes, that is a really good solution to this problem. The Tesla charging cable and onboard chargers will thankfully adjust to whichever voltage level you're giving it, but for good safety practice, it is a very good idea to adapt using the same current level, so something doesn't accidentally reset and try to overdraw the circuit.
As to the charging speed, the 240V 16A will give you about 11 miles per hour (maybe 10, being a Model X). 90 miles overnight is pretty good for having almost no installation costs. I tend to disagree with some of the people *ahem* who tell people they need big high power circuits. This is all dependent on what your real miles of driving situation is. If 90 miles a day is more than your usual, then it's fine. If you occasionally do go for 120 or 150 miles or whatever on a particular day, keep in mind that you don't need to refill that all in one overnight. You'll catch up over the next two or three nights, and then you're back up to your 80 or 90%. I am skeptical of trying to use 5-15 outlets for regular use, since the 3 miles per hour rate is REALLY low, but most 240V levels are pretty good.

 

[SSedan]

I put on 15-30 miles a day and charged on 110volt standard circuit for a few weeks before putting in a 30amp 240volt circuit. As said long as your "average" trip can be comfortably accounted for overnight and the weather isn't extreme causing hard climate control use occasional trips to long to recoup overnight are not a problem.

My P85 came with the 30amp 240volt adapter as I understand it they reduced the number of adapters in the kit and this isn't included anymore. This is a "dryer" outlet and in many parts of the country you can find them in garages or very near which can help when visiting friends and family.

 

[jbcarioca]

As to the charging speed, the 240V 16A will give you about 11 miles per hour (maybe 10, being a Model X). 90 miles overnight is pretty good for having almost no installation costs. I tend to disagree with some of the people *ahem* who tell people they need big high power circuits. This is all dependent on what your real miles of driving situation is. If 90 miles a day is more than your usual, then it's fine. If you occasionally do go for 120 or 150 miles or whatever on a particular day, keep in mind that you don't need to refill that all in one overnight. You'll catch up over the next two or three nights, and then you're back up to your 80 or 90%. I am skeptical of trying to use 5-15 outlets for regular use, since the 3 miles per hour rate is REALLY low, but most 240V levels are pretty good.

I have 208/30 at home, and often the actual is 199/19 or so. Especially because the OP really needs this only for weekends I think it will work out fine for the cheapest choice, so long as the amperage setting is correct. If overnight will be at least ten hours you'll have at least 100 miles added. If that is enough there is no reason for faster charging.

Some people go with:
-some is good,
-more is better'
-only too much is enough.

Nonsense. In practice it is nice to the battery to be connected, charging, pretty much all the time. As Tesla said long ago "a plugged in Tesla is a happy Tesla".
I often set my amperage at 5 amps, the minimum, when I expect to be parked for a couple of days or more. That is still 3-4 mph of charge, normally plenty for me.

For a long time when I had no approval for my 208/30 connection I was plugged into a 110v normal household outlet. That would have been fine, but it is less efficient than is 220 so higher voltage does save electricity.

 

[brkaus]

Agree with the 5-20 suggestion. It’s safe and most people can charge fine on that current/voltage.

You could also use an HPWC and set the current switch inside for 20a circuit.

 

[jbcarioca]

Agree with the 5-20 suggestion. It’s safe and most people can charge fine on that current/voltage.

You could also use an HPWC and set the current switch inside for 20a circuit.

Apart from the cost for the HPWC that seems to me to be the best solution. Zero mistakes, zero adapters, zero complexity. Further installation can be via a plug to L6-20.
The L6-20 male plug is really expensive:
P&S L620-P : TURNLOK PLUG 3-WAY 20A 250V | Gordon Electric Supply, Inc.

$8.39 from Gordon.
The ideal solution clearly will be a native NEMA L6-20 male plug.

HPWC are available on eBay if you don't want to pay the Tesla price:
tesla HPWC | eBay
cheapest one right now is $525.

That will give you a permanent solution, foolproof and simple to use.
Because you'll plug the HPWC in your installed outlet it could not be much simpler. The initial setting of the HPWC amperage and installing the plug will be it, though you'll need to mount the HPWC somewhere.

 

[TexasEV]

My P85 came with the 30amp 240volt adapter as I understand it they reduced the number of adapters in the kit and this isn't included anymore. This is a "dryer" outlet and in many parts of the country you can find them in garages or very near which can help when visiting friends and family.

The charging kit provided with new cars hasn’t changed from day 1. It’s NEMA 14-50 and 5-15 adapters for the UMC and the J1772 adapter. It never included a 30A adapter. What changed is sometimes the 30A adapters were available to order and sometimes they weren’t.

 

[brkaus]

HPWC are available on eBay if you don't want to pay the Tesla price:

Currently $500 from Tesla. Free shipping, tax would be added.

Model S/X/3 Wall Connector

Benefits -
- high quality
- EVSE can stay in car
- with proper wiring, can go up to 80a
- can install multiple to share a circuit if limited.

Cons -
- cost


I just installed one. Looks nice, works well. Probably would have stuck with the 14-50, except utility picked up half the cost

I did have it set to 40a due to utility rates, but had it wired for 48a just in case.

 

[Cosmacelf]

Yes, making a 5-20 to L6-20 adapter is the way to go. Here's a page that provides pin out charts, etc. to make it easier.

CarCharging.us

I personally would buy a short 5-20 extension cord, cut off the male end, and then wire it into an L6-20 plug.

 

[Rocky_H]

I often set my amperage at 5 amps, the minimum, when I expect to be parked for a couple of days or more. That is still 3-4 mph of charge, normally plenty for me.

For a long time when I had no approval for my 208/30 connection I was plugged into a 110v normal household outlet. That would have been fine, but it is less efficient than is 220 so higher voltage does save electricity.

I think you're misunderstanding this; you're being just as inefficient. 120V at 10A and 240V at 5A are still the same power. The low power is what is making it inefficient, not the voltage. The source of the inefficiency is that the charger in the car consumes about 300-400W just to run the charging process. If you're only giving it 1kW, you're losing 1/3 of your power for the many MANY hours that it's running. Give it 10kW, and you're only losing 4% of your power to that overhead, and it runs for a much shorter time.

 

[Cosmacelf]

Yes, Rocky-H is right. Put another way, the wasted overhead for charging (car's computer power) stays almost the same whether you are charging at 120V/12A or 240V/40A, but when charging at 120V/12A, you are charging for a lot longer time, so the overall electricity (energy) wasted to overhead is much higher.

That's the reason why when you only have 120V, charging at 16A with the 5-20 adapter actually puts 42% more electricity (energy) into the car rather than the 33% boost you'd expect going from 12A to 16A. Which is why I always tell people when charging at 120V to find a 20A receptacle somewhere, it is more energy efficient (and 42% faster).

I would never advise to charge at 240V/5A since it wastes energy.