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Info from Tesla - 277v feed to Wall Connector (HPWC) - Which Cars Support It

eprosenx

Active Member
May 30, 2018
2,065
2,485
Beaverton, OR
I have been involved in a number of threads on the forums regarding 277v support via the Wall Connector / HPWC. There seems to be a lack of clarity in what is and is not supported and whether it will require a trip to the service center to "reset" your car if the voltage is too high.

Because of this, I reached out to Tesla for some official answers and they were *very* helpful. I am making the assumption that this is not proprietary here and so I am going to post the information here for the benefit of others. My questions are in black, and Tesla's responses are in Red.

Note that *officially* I think the recommendation is to install them using 240v or 208v, but they were kind enough to give me the skinny on what the cars actually support.
  1. Does the Model 3 support charging at 277v? Yes, Model 3 is capable of accepting a 277 volt AC power supply.
  2. What is the maximum charging voltage on the Model 3 (i.e. a 277v feed may fluctuate above that at times due to grid conditions) We allow for a +/- 10% threshold, so up to ~300v should be okay for Model 3.
  3. What happens if the max voltage limit is hit? Does charging just stop, or can damage occur or does a service center have to "reset" something to allow the car to charge again? Charging will stop if the vehicle doesn’t like the power supply.
  4. Why did Tesla remove 277v from the instruction manual on the Wall Connector? There are places I would like to encourage destination chargers to be installed and in many cases it would be cheapest to just wire directly to 277v rather than require a stepdown transformer. The on-board charger of Model S and Model X are a bit more sensitive to 277v power supplies and can be more prone to rejecting the power supply when there are excessive utility fluctuations. It doesn’t hurt the electronics of the vehicle, but it can lead to unreliable charging experiences. As a result, we’ve largely backed off from 277 volt installations.
  5. What are the voltage limits on the S and X (of the various different versions of charger that have been sold over time)? Do either of them have more constraining limits or need to be taken in for service in an over-volt situation? Model S and Model X can accept a power supply that’s at a true 277v, but a relatively small increase in voltage can result in the vehicle not charging.

Question: I know back in the Model S units there were the 40a units (or double that with two) and now they are 48/72a units.

Do both versions exhibit that sensitivity to 277v or is it more prone on one version or another of the onboard chargers?

Older Model S with the 40A/80A capable on-board chargers are a bit more forgiving with a 277 volt power supply. These vehicles can be most easily identified by the black nose cone, oftentimes referred to as the ‘classic’ or ‘original’ Model S. Refresh Model S (no nose cone) and all Model X are built with the 48A/72A onboard charger hardware, which is a bit more sensitive. These vehicles can potentially reject the power supply if the AC voltage goes above 280 volts.


Question: At 277v will a Model 3 still charge at a full 48 amps (13.3kW), or does it hit some other limit that restricts it?

There is an amperage ceiling and power ceiling to the onboard charger. Model 3 max power input is about 11.5 kW, which matches up nicely with a standard residential power supply (240 volts * 48 amps = 11.5 kW). When the AC voltage is higher the vehicle will draw less current to stay within the max power rating of the onboard charger. I would expect a Model 3 Long Range vehicle to cap out at around 41 or 42 amps when connected to a 277v AC power source (277 volts * 41 amps = 11.3 kW).

The ability for Model 3 to accept 277 volt power supplies was enabled via a firmware update that was pushed a few months ago. Looks like some of the issues in the forums are from May, as long as the Model 3 is on recent firmware it should be able to accept the 277 volt power supply.


So some great information here. This explains various discussion we have seen in the forums (about it working or not working) and also explains why Tesla backed away from 277v support in the HPWC. Original series Model S units could handle it without issue, but then the post-refresh Model S it is right on the borderline (as well as the X), perhaps resulting in poor user experience sometimes depending on grid voltage. Then the Model 3 had it disabled in firmware, but then they pushed an update so that now it works (and sounds like it should be reliable up through like 300v.

It is also interesting that there is a cap on total kW that the onboard charger can handle, so wiring things up at 277v may not buy you anything speed wise of charging.
 

quantumslip

Member
Mar 3, 2015
473
494
Houston, TX
Thanks for this. How did you get this info, email support and got someone high enough?

It sucks that 277v is being held back because of the design choice for the charger. Originally I thought it was a cost issue, but if the model 3 can handle it with no issues then I can't see why they couldnt have designed the s and x to do so reliably as well.

My only hope for this later is that when there's enough market saturation with working chargers with newer cars (maybe if they incoroporate the 3 charger into the future S and X redesign) that they bring support back, and have appropriate flags in navigation so that people know what works and doesn't work.
 

eprosenx

Active Member
May 30, 2018
2,065
2,485
Beaverton, OR
Thanks for this. How did you get this info, email support and got someone high enough?

It sucks that 277v is being held back because of the design choice for the charger. Originally I thought it was a cost issue, but if the model 3 can handle it with no issues then I can't see why they couldnt have designed the s and x to do so reliably as well.

My only hope for this later is that when there's enough market saturation with working chargers with newer cars (maybe if they incoroporate the 3 charger into the future S and X redesign) that they bring support back, and have appropriate flags in navigation so that people know what works and doesn't work.

Yeah, I lucked out. I emailed them and I think I wrote the subject and body to be interesting enough (or technical enough) to get the right persons attention. ;-)

I agree that it sucks that 277v was held back. It feels like a product management mistake was made on the new model S and X units to not make that a core requirement of their chargers.

Since there are so many of the second gen Model S units and all the Model X units out there now it seems like 277v support in the future is extremely unlikely as it would cut the old cars off, but yeah, here is to hoping it may again be an option some day.

I think 277v support is important to drive costs down for charging EV's in commercial parking garages and such were 480/277v feeds are the norm. Having to spend money to step it down to 208v seems lame (or 240v if you get creative).
 

David99

Active Member
Jan 31, 2014
4,850
7,023
Brea, Orange County
A few years back I remember reading that Superchargers are actually built from standard Model S chargers. They accept 277 Volt just fine. I believe there are 12 in each. The power between the stalls is switched always in groups of three because of three phase source. I noticed that at Superchargers that you get 36, 72 or 108 kW or full power (which depends on your car). So it's 12 kW per charger. In the classic Model S, the charger is limited to draw 40 Amp from the grid, but the charger actually says 45 Amp. Which makes sense to get 12 kW at 277 Volt, you need to get more than 40 Amps. Long story short, the classic Model S charger (labeled GEN2) is capable of 12 kW at 277 Volt and 45 Amp. But for some reason they decided to limit it to 40 Amps in the car.
 

eprosenx

Active Member
May 30, 2018
2,065
2,485
Beaverton, OR
A few years back I remember reading that Superchargers are actually built from standard Model S chargers. They accept 277 Volt just fine. I believe there are 12 in each. The power between the stalls is switched always in groups of three because of three phase source. I noticed that at Superchargers that you get 36, 72 or 108 kW or full power (which depends on your car). So it's 12 kW per charger. In the classic Model S, the charger is limited to draw 40 Amp from the grid, but the charger actually says 45 Amp. Which makes sense to get 12 kW at 277 Volt, you need to get more than 40 Amps. Long story short, the classic Model S charger (labeled GEN2) is capable of 12 kW at 277 Volt and 45 Amp. But for some reason they decided to limit it to 40 Amps in the car.

Yes, it is my understanding as well that the superchargers use the same modules as the original Model S used.

Your math seems to make sense. I have only supercharged my M3 once and so I don’t have much experience as to what levels it steps down at when “sharing” with another car. I was the only one at the supercharger when I charged.

I am guessing btw that the reason they limit the onboard charger to 40 amps is due to cooling limitations. It is easier for them to cool their supercharger cabinets (have you heard the fans in those things?).
 
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FlatSix911

Porsche 918 Hybrid
Jun 15, 2015
6,538
5,946
Silicon Valley
I have been involved in a number of threads on the forums regarding 277v support via the Wall Connector / HPWC. There seems to be a lack of clarity in what is and is not supported and whether it will require a trip to the service center to "reset" your car if the voltage is too high.

Because of this, I reached out to Tesla for some official answers and they were *very* helpful. I am making the assumption that this is not proprietary here and so I am going to post the information here for the benefit of others. My questions are in black, and Tesla's responses are in Red.

Note that *officially* I think the recommendation is to install them using 240v or 208v, but they were kind enough to give me the skinny on what the cars actually support.
  1. Does the Model 3 support charging at 277v? Yes, Model 3 is capable of accepting a 277 volt AC power supply.
  2. What is the maximum charging voltage on the Model 3 (i.e. a 277v feed may fluctuate above that at times due to grid conditions) We allow for a +/- 10% threshold, so up to ~300v should be okay for Model 3.
  3. What happens if the max voltage limit is hit? Does charging just stop, or can damage occur or does a service center have to "reset" something to allow the car to charge again? Charging will stop if the vehicle doesn’t like the power supply.
  4. Why did Tesla remove 277v from the instruction manual on the Wall Connector? There are places I would like to encourage destination chargers to be installed and in many cases it would be cheapest to just wire directly to 277v rather than require a stepdown transformer. The on-board charger of Model S and Model X are a bit more sensitive to 277v power supplies and can be more prone to rejecting the power supply when there are excessive utility fluctuations. It doesn’t hurt the electronics of the vehicle, but it can lead to unreliable charging experiences. As a result, we’ve largely backed off from 277 volt installations.
  5. What are the voltage limits on the S and X (of the various different versions of charger that have been sold over time)? Do either of them have more constraining limits or need to be taken in for service in an over-volt situation? Model S and Model X can accept a power supply that’s at a true 277v, but a relatively small increase in voltage can result in the vehicle not charging.

Question: I know back in the Model S units there were the 40a units (or double that with two) and now they are 48/72a units.

Do both versions exhibit that sensitivity to 277v or is it more prone on one version or another of the onboard chargers?

Older Model S with the 40A/80A capable on-board chargers are a bit more forgiving with a 277 volt power supply. These vehicles can be most easily identified by the black nose cone, oftentimes referred to as the ‘classic’ or ‘original’ Model S. Refresh Model S (no nose cone) and all Model X are built with the 48A/72A onboard charger hardware, which is a bit more sensitive. These vehicles can potentially reject the power supply if the AC voltage goes above 280 volts.


Question: At 277v will a Model 3 still charge at a full 48 amps (13.3kW), or does it hit some other limit that restricts it?

There is an amperage ceiling and power ceiling to the onboard charger. Model 3 max power input is about 11.5 kW, which matches up nicely with a standard residential power supply (240 volts * 48 amps = 11.5 kW). When the AC voltage is higher the vehicle will draw less current to stay within the max power rating of the onboard charger. I would expect a Model 3 Long Range vehicle to cap out at around 41 or 42 amps when connected to a 277v AC power source (277 volts * 41 amps = 11.3 kW).

The ability for Model 3 to accept 277 volt power supplies was enabled via a firmware update that was pushed a few months ago. Looks like some of the issues in the forums are from May, as long as the Model 3 is on recent firmware it should be able to accept the 277 volt power supply.


So some great information here. This explains various discussion we have seen in the forums (about it working or not working) and also explains why Tesla backed away from 277v support in the HPWC. Original series Model S units could handle it without issue, but then the post-refresh Model S it is right on the borderline (as well as the X), perhaps resulting in poor user experience sometimes depending on grid voltage. Then the Model 3 had it disabled in firmware, but then they pushed an update so that now it works (and sounds like it should be reliable up through like 300v.

It is also interesting that there is a cap on total kW that the onboard charger can handle, so wiring things up at 277v may not buy you anything speed wise of charging.

Well done :cool:
 

David99

Active Member
Jan 31, 2014
4,850
7,023
Brea, Orange County
I posted about it here How pairing at Supercharging works

I’m just wondering what they are using these days in superchargers. The cars have not been using these chargers for a while. But maybe they still produce a version of these just for superchargers.


Yes, it is my understanding as well that the superchargers use the same modules as the original Model S used.

Your math seems to make sense. I have only supercharged my M3 once and so I don’t have much experience as to what levels it steps down at when “sharing” with another car. I was the only one at the supercharger when I charged.

I am guessing btw that the reason they limit the onboard charger to 40 amps is due to cooling limitations. It is easier for them to cool their supercharger cabinets (have you heard the fans in those things?).
 

Tress

Member
Sep 20, 2018
79
77
Houston, TX
If you are in the Houston area, you can test out a 277v HPWC at the Tesla Gallery in The Woodlands. They have approximately 6 chargers and plugshare has some screenshots of the charge rates.
 

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quantumslip

Member
Mar 3, 2015
473
494
Houston, TX
If you are in the Houston area, you can test out a 277v HPWC at the Tesla Gallery in The Woodlands. They have approximately 6 chargers and plugshare has some screenshots of the charge rates.

I may have to trek out there to try it myself...

PlugShare - Find Electric Vehicle Charging Locations Near You

I did see one entry on plugshare showing a Model 3 charging. Indicated rate was 281V @ 45 amps. That implies the onboard charger has a cap of ~ 12.6 kW
 
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eprosenx

Active Member
May 30, 2018
2,065
2,485
Beaverton, OR
Well I made the trek and here are the results...
View attachment 337836
View attachment 337837
View attachment 337838

Generally seeing 277V @ 46amps, 47-48mph of range gained. (I have AWD). Implies power limit of approx 12.7kW (could be off due to rounding).

Awesome! Thanks for testing this! It adds additional information to what we know!

It is a bummer that they are recommending folks not install Wall Connectors at 277v. Max charge speed is awesome! (though 11.5kW at 240v is not much less than 12.7kW so speed is not that big a deal - the primary advantage would be not having to have stepdown transformers from 480/277v to 208/120v)
 
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cellogig

Model X..Model 3
Feb 14, 2018
310
298
Near the BP oil spill

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eprosenx

Active Member
May 30, 2018
2,065
2,485
Beaverton, OR
I have some test results also.
With lowering the amps from 46 down to 42 on board of the vehicle will this help not going over the cap limit when there is a voltage surge?

No, if anything, dropping the amps down will increase voltage not decrease it because with less load on the line the resistance is lower.

Is that a Model 3? If so, it should have no issues with 277v even if the voltage drifts nominally higher than 277v. It is the post redesign "S" units and "X" units that might be somewhat touchy. But I think it sounds like all it will do is interrupt charging, so not really a risk to use it. (though it would be very annoying if you can't get it to charge due to too high voltage)
 
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Fiver

Active Member
Apr 10, 2015
1,853
1,544
Utah
Why all the concern about using big transformers to drop all the way to 208? A small 2kVA 32v buck transformer is all that is needed here. 277v-32v is 245v. Good to know that the model 3 does support 277 natively though.
I know for a commercial HPWC I helped setup through the destination charging program, a large portion of the install costs came from having to put in the transformer to step down to 208v from 277v.
 

wws

Member
Aug 11, 2014
926
947
Northern California
Maybe this question should be the subject of a separate thread, but what would be the possibility the SAE could modify some future J1772 revision to include 277v charging? I'd imagine they would insist on some additions to the signalling protocol. Maybe while at it, they could add 20 and 24 amp charging at 120v. (Which Tesla also already allows.)
 

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