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How Fast - Home Charging
- Thread starter JWinter
- Start date
aesculus
Still Trying to Figure This All Out
Of course in real life it’s way less than that. You’re not usually going to be arriving home with the battery depleted, and you’re not usually going to charge to 100%.
nwdiver
Well-Known Member
aesculus
Still Trying to Figure This All Out
The minimum for 72 amp continuous charge is 90 amp breaker. But if you have a longer wire run or smaller gauge wire you could need a larger breaker.
You will need to consult wiring charts to see what the amperage is for a given conductor size, material type and distance. Then figure that you can only get 80% of the rated capacity for continuous power draw. So in the example you quoted the conductor did not come into play in the calculation at all.
eye.surgeon
Active Member
The reality is that it doesn't matter how long it takes as long as it's less hours per day than you sleep.
You can't upsize the breaker for smaller wire - you'll overload the wire and could cause a fire. For a long wire run, you'd want to upsize the wire, but not the breaker - the load through the breaker won't change.
eprosenx
Active Member
The Wall Connector will take up to a 100a breaker and up to 3 AWG copper wire. To do the full 100a you need 3 AWG copper wire and I think of a type rated for 75c insulation (which rules out NM style romex cable since it is only rated to 60c) - you need to run THHN style wire in conduit or MC / Flex cable/conduit to use the 75c rating.
So yeah, that is the best way to "max" the ability of the HPWC. Now none of the currently sold Tesla's will draw more than 72a, so they don't need more than a 90a circuit (older dual charger model S units could take up to 80 amps on a 100a circuit).
You can do up to four of the new model HPWC units on a single circuit and they can work together to manage load so it is kept under the limit for that circuit at all times. If you think you might install more linked HPWC units in the future this might be a reason to do the full 100a circuit.
I should also call out that you need to do load calculations to ensure your main service feed can handle whatever size breaker you end up going with (and what setting you make during the install of the HPWC for max current). Your existing electrical feed to the house may not be able to support 80 amps of charging on a 100a breaker...
To others points though: When charging at home, typically you just need to be able to fully charge overnight... So generally you will get at least eight hours a night. Even if you one day came home from a long trip where you were fully empty and then had to turn around to go to work in the AM, would it be the end of the world if you only got up to 70% or so overnight? How often would you really need to come home fully empty one day and then turn around the next day and need it to 100% by the AM?
I am a fan of having the fastest charging available to me as possible, but from the reality side of things, my commute is 30 miles total, so I don't need a ton of charging speed.
FlatSix911
Porsche 918 Hybrid
Texas
Member
I have the dual chargers on a 2015 Model S with a 85 kWh battery. The breaker is 100 amps, the maximum draw is 80 amps 240v, which adds 52 miles of range per hour, exactly as shown on the chart. When your Tesla wall unit is installed, be sure the electrician reads the instructions - the settings must be set properly to permit the output you expect. When my unit first went in, it wouldn’t budge above 40 amps until we reworked the settings.
What’s beautiful is a dual charger Model S on a 277 volt wall connector. 22 kW!
roblab
Active Member
And, for balance, I charge at 24-32 amps, simply because I don't need to charge fast. Most cars only drive an hour or less a day, leaving 23 hours a day to charge.
Then there are those who will drive twenty minutes each way to a supercharger and sit in their car for another 20 minutes. I don't get it. You can charge on 110 at home. Oh, yeah, supercharging is free.
What's the hurry? We lived for six years with only one car, our Model S. Charging was never an issue or a problem. Full every morning, roughly 27,000 miles a year.
Then there are those who will drive twenty minutes each way to a supercharger and sit in their car for another 20 minutes. I don't get it. You can charge on 110 at home. Oh, yeah, supercharging is free.
What's the hurry? We lived for six years with only one car, our Model S. Charging was never an issue or a problem. Full every morning, roughly 27,000 miles a year.
eprosenx
Active Member
Yeah...
It is sad that they seem to have discontinued 277v support going forward. Reports are that existing HPWC units at 277v don't work with the Model 3, and the Wall Connector instructions no longer provide 277v as an option.
I am curious why they made the design decision to cut that as an option. Seems like it would have been a great option for commercial installs of the Wall Connector.
sammyfan711
Member
I keep hoping against hope that Model 3 gets a 72 amp option - it would be a real sick one
eprosenx
Active Member
Nah, won't happen. The 48 amp charger *is* the fast one. The 32 amp one will be the slow one. Since the car takes less energy per mile 48 amps gives it tons of range per hour of charging.
Nearly nobody needs that fast of charging at home or at work. They build cars for the mass market (especially the Model 3), not the .01% that have some weird use case.
Do you have a need for a faster charger than the 48 amp one? If so, maybe you should just buy a supercharger. ;-) (I wonder if they would even sell you one?)
Canuck
Well-Known Member
72? The HPWC puts out 80. Why waste 8 amps? But otherwise, I thought the same thing. It's disappointing how slow it charges. I still can't believe Tesla makes a HPWC that puts out 80 amps but makes no vehicles to take advantage of it.
I couldn't make it to my cabin and back in one day, which I often do, without dual chargers at 80 amps and a HPWC there
.
Plus. for destination charging, we will often arrive with a low battery at a hotel, and while we unpack and shower we have enough range for the night out, then charge fully overnight, and skip going to supercharger altogether.
I'm taking a trip from BC to Osoyoos then to Oroville, WA State's side of the lake, and there's no superchargers after leaving Hope, BC along the number 3 highway. There's a lot of Chademos but that's no good with the 3. Plus, a lot of 70-80 amp Sun Country and HPWC's -- and I need to drop my daughter off and come back same day -- but with the 3 I can only take advantage of 48 amps. I would have gladly paid extra to have that upped to 80! It's huge to some of us.
Even if you don't use it much, when you do need it, you usually really need it, at least in my view -- and after having that happen. So when I read your post I can't help but chuckle because I really want to take my 3 on this upcoming trip -- but may have to take my S -- because of the 3's undersized charger.
On the bright side, superchargers are planned for Princeton, and Osoyoos, but not until 2019, and even then I still want 80 amps for the other reasons.
eprosenx
Active Member
This is a good callout, but I don't think most folks realize what is really in a HPWC. I would not use the terminology "puts out" since the HPWC is not a charger, it is simply a glorified extension cord (with some important safety features).
The original HPWC units were 80 since that is what you needed if you had dual 40a chargers (the default was a single 40a charger).
Really the HPWC (EVSE) is just a Ground Fault Circuit Interrupter, and a "contactor" to turn on and off the power so you are not inserting a connector that is energized, and a small microcontroller to detect the presence of a car plugged in and to tell the car what amount of power it is allowed to draw. That is pretty much it. So the delta in cost between a 48, 72, or 80 amp unit is pretty negligible since all the same components are necessary.
So I would say you are outside of the average user with the "to the cabin and back in one day" use case. Your other use case of the hotel I think would be fine on a Model 3. Arrive empty, charge for an hour, get 44 miles of range. I suspect that is enough for most dinner trips!
I trust that ChaDeMo charging will have to be solved for the Model 3. There are many here in Oregon too, so I want to be able to use them! I assume it is just a software thing...
Note that a Model 3 at 48 amps gets 44 miles of range per hour and a Model S at 72 amps only gets 52 miles of range per hour. So the economy of the car helps make that gap smaller (but yeah, you have 80 amps of charging which none of the new vehicles do).
More Superchargers of course will also solve this issue.
I just don't think we will see a faster in a M3 for some time. Though I would love to be proven wrong! I would not be shocked if they want to keep this as a product stratification thing between the M3 and the MS.
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