I've seen many people mention that on both Tesla forums, but it's just nonsense. While it is a thing that does exist, almost no one actually has a portable 14-50 to J1772 charging cable. A friend of mine just got a used Fiat 500e electric car, but didn't have anything better than regular 120V outlet charging at his house yet. I wanted to be able to help him out with using my 14-50 outlet for a bit, but we didn't have any charging equipment that could get it to a J1772 plug that his car needed.
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Charging two Teslas at once?
- Thread starter Keith909man
- Start date
Nobody ever said 80 amps! 60 amp breaker max. Loadshare will distribute 48 amps between the two cars. All you will ever need to charge overnight.
whitex
Well-Known Member
That is why in my garage I have 2 NEMA 14-50's, each on its own 50A breaker. One on each side of the garage, and one of them is even connected to the generator backed up part of the house, just in case I have to charge somehow at home during a power outage. Then I have a third 100A circuit for HPWC (currently one, but junction box already wired in for the second HPWC for when I get to installing it). The idea is that cars usually charge from the 100A circuit and the NEMA14-50's are for backup situations.
A year ago my wife got hit by a DUI driver and her 1 year old (at the time) Model S got totaled (while my wife walked away with just some pain and aches). We replaced it with a brand new Model S and that's when we found out its not compatible with the Gen1 HPWC, so we had to use the NEMA 14-50 for few weeks until we got a new HPWC.
For people who have Gen1 HPWC working just fine for their pre-2018 Model S, they can run into problems if they get a Tesla loaner for few days that is 2018 or newer, and they find out they can't charge it.
whitex
Well-Known Member
Not exactly. With HPWC and NEMA 14-50 on a 50A breaker, you can have 2 cars charging at 50A total current for hours, which is not what the circuit is rated for - 40A (80% of 50A). This is a similar problem why Tesla software locked Canadian mobile connectors to 32A (and eventually just made a 32A only mobile connector for all). NEMA 14-50's for dryers are often on 40A circuits, which caused some fires when the mobile connector was drawing 40A for hours at a time (breaker will not trip, but wire will heat up over time).
whitex
Well-Known Member
Not an option for most people. Even in warm weather you won't get more than 40miles range in 12hrs of charging, in the cold winter you might get 20, which will not be enough for people who drive more than 20 miles a day.
whitex
Well-Known Member
50A installation vs. 100A installation is not just $50 in wires. Even wires will cost more unless you're running it <~10ft. Wires require larger conduit and is more difficult to work with, so more expensive installation. Then there is a 100A breaker, which is more expensive, then the safety switch required in most places ($200 plus need to install it, which costs time, therefore money, and you need to find a space for it). A junction box for AWG6 is much cheaper than for AWG2 too, if you want to pre-wire one for a second HPWC in the future too. So no, the difference is not $50.
I think I've seen that before. "640KB ought to be enough for everyone".
Battery capacity grows, charging time shrinks, currents go up. I wouldn't be that confident upon 48A for a lifetime.
Besides, 2 x 14-50 running each on individual breaker will provide higher combined charging rate with much less investment.
Where did I say to go complete 80A setup ?
Safety switch is incremental, breaker can be swapped out easily. What is the deal breaker, is re-running the wire, _especially_ with replacing the conduit (which you can see not everyone is ever using).
Again, no matter what you're installing, even if it's 40A branch right now, there's no single reason to go below #4.
Well, let's see if this applies or not.
Did you stop to think of what impact this has? Let's say someone's usual driving is 60 miles in a day. They have an EV with 200 miles range--140 miles leftover. Maybe 5 or 10 years later, they have an EV with 300 miles--240 miles leftover. Then in 20 years, they have an EV with 500 miles range--440 miles leftover. Do you see now how larger capacity batteries actually mean less need for faster and faster charging speeds, because people will have a lot more spare range to work with? Bigger range cars don't equate to your commute distance to work growing exponentially as well, like in the Bill Gates analogy you are trying to equate this to.
Oh really? This is a Tesla forum, so let's check what Tesla has done in that area. Their maximum current rating of their vehicles has gone from 80A, to 72A, to 48A. Those current capabilities are going down, not up.
This is applicable as far as how many vehicles people eventually replace from gas to electric, so they may need to supply more miles total in the household. We have one electric and one gas car now. We will eventually be replacing the other gas car, so there will need to be some electrical accommodation for that. But we have the more used car and the less used car, as probably many other households do, so people may be able to use a smaller circuit for the car that drives less, or use the higher power connector on it once a week or so to catch it up.
Our house only has a 125A main feed, so we're not going to be able to just keep adding extra 50A circuits. We may go with just a 120V regular wall outlet for the secondary car that doesn't get used much and top it up from the 14-50 as needed if it drives farther for some reason.
whitex
Well-Known Member
If you run AWG#2 the wires will not fit into a 50A breaker. If you put a 100A breaker, you have to have a safety switch in most places. Safety switch is not incremental as you say, as it requires you to break the current conduit to add it, even if you didn't put it inside the wall, you can't just add a safety switch on top of a already place conduit - there won't be enough wire slack when you just cut into a conduit, so if you plan to go above 50A or 60A, you need the safety switch installed. Running AWG4 doesn't give you much. If all you need is NEMA 14-50 (40A charging), AWG6 is plenty sufficient, cheaper and easier to work with. The only low incremental cost thing I can think of is putting in a larger conduit, so if you do want to upgrade in the future, you just replace the wire with larger one and cut into the conduit to add the safety switch at that time.
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whitex
Well-Known Member
The bottom line is how many miles per night can your system deliver for you. Unless you think EV's are going to get less efficient over time, let's use a 3 rated miles per KWh for simplicity (most Teslas rated range is more efficient than that already). Let's use your 48A example, so 48A/240V will deliver roughly 415 rated miles per 12hr overnight session. Add even severe winter issues, and you still get ~250 actual miles of range per day, which is sufficient for most 2 car households. For emergency charging you go to a 120KW supercharger. Our cars are charging at 48A+40A today, I am consolidating to shared load-balanced 80A capacity (100A circuit) and I am not at all worried that it won't be enough.
That's very true. And how many you drive, too.
I think they will get less efficient. Just two things to consider: Tesla Pickup Truck and cabin heating.
And then, if Tesla wants to penetrate more markets, going for longer daily mileage is also inevitable.
Each of those factors can easily double today peak energy use in just couple years. Charging rate will need to follow.
Overnight charging session of 12 hrs sounds quite generous. In AZ, charging window on EV plan is 6 hrs.
whitex
Well-Known Member
So planning should be done based on your expected driven miles, with some room for near term expansion (e.g. you will buy another EV). If 6hrs is the cheapest energy calculate for that, or figure out how much it would cost to charge outside that window and compare that cost to installing a faster charger (which may or may not require you to upgrade your service, which may add more cost than occasional higher priced charging). Either way, get what you need and what you foresee you will need in the near future - don't overbuild just because someday, maybe in 20 years, possibly, you just might want to buy 2 Tesla pickups. Partial overbuilding, like running AWG#4 instead of AWG6 just adds unnecessary cost, and if you do get your two Tesla pickups you will realize you need a AWG2 wire anyways and put in a new run with a safety disconnect anyways.
I do foresee that in a meantime I'll move to 100..120KWh vehicle, supposedly with higher current onboard charger. Then it will take me just an hour to change 14-50 to HPWC @ 80A. Something tells me that it's quite probable scenario for many.
whitex
Well-Known Member
Not unless you already ran AWG2 (maybe AWG3) all the way to the NEMA 14-50, left some wire slack (you cant just twist AWG2's together to join them), and have the safety disconnect already wired in. Still, if you did you had to micky-mouse the 50A breaker because an AWG2 will not fit into a 50A breaker (and possibly the NEMA 14-50 either). If you spent all the money on a 100A setup, why not just put in an HPWC from the getgo?
I get the feeling you are speaking academically, based on some theoretical thought experiments and/or what you're planning to do, but you're missing the practical aspect of such project.
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This is exactly what the whole topic is about.
I don't see any point of tossing another $500 into HPWC right now, to get negligible 20% increase against Gen 1 UMC, as in either event I get my P85 charged overnight. The OP seems to have similar dilemma, just with two cars.
Same thing - I don't see the point of prematurely capping HPWC at 50A (or even 50A per two units !) as there currently are cars which can pull 72/80A, and with high chance the need for higher power charging will grow as EV technology develops.
I've pictured my setup above.
Not from Tesla, certainly. They keep lowering the current of their onboard chargers. I don't know why you think they will be higher.
Clarification: there are still older cars that had those capabilities. Tesla discontinued those and doesn't even offer the 72A charging at all anymore in the cars they build now.
I don't know why you continue to try to believe this. It has been demonstrated that the opposite is happening. You seem to have not read my previous explanation of this.
Tesla seems to be going toward the model of having the onboard chargers be more toward a medium level for overnight use, and for people's faster charging needs, having people rely more on fast DC charging as that infrastructure continues to be built out more and become more widespread.
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