[North American] - Home / Residential charging update (using Tesla Universal Wall Charger)

[whitex]

@daveo4EV , when investigating the Macan charging, see if they can measure in the service bay if the car is in fact overshooting by 0.7A (i.e. drawing more sustained current than allowed by the J1772 spec). Besides potentially violating electrical codes in places, which could lead to liability assignment (someone's less than perfect installation burns the house down, they could argue if the Macan only didn't draw the additional 0.7A maybe the fire would not have happened), it could also lead to Macans having issues charging, if the EVSE detects the overshoot and shuts down the charging session for safety.

 

[dgkhn]

@whitex, I'm sorry, but this confuses me. Is there something in the J1772 spec that would limit the current draw to 40 amps in this scenario (I thought the spec limit was higher--80 amps)?

My understanding is there are two factors here: the maximum current permitted by the EVSE (which is determined by a setting within the EVSE, presumably based on the EVSE design capacity, or the allowed wiring circuit ampacity, whichever is lower), and the capacity of the car's built-in charger (which may or may not be 40 amps in the case of the Macan--I don't think this has been firmly determined yet.) The draw should be the lower of the EVSE setting or the car's maximum.

In this case, he EVSE itself should be limiting the draw to 40 amps, not the Macan, is my understanding.

 

[whitex]

@whitex, I'm sorry, but this confuses me. Is there something in the J1772 spec that would limit the current draw to 40 amps in this scenario (I thought the spec limit was higher--80 amps)?

My understanding is there are two factors here: the maximum current permitted by the EVSE (which is determined by a setting within the EVSE, presumably based on the EVSE design capacity, or the allowed wiring circuit ampacity, whichever is lower), and the capacity of the car's built-in charger (which may or may not be 40 amps in the case of the Macan--I don't think this has been firmly determined yet.) The draw should be the lower of the EVSE setting or the car's maximum.

In this case, he EVSE itself should be limiting the draw to 40 amps, not the Macan, is my understanding.

EVSE does not limit (at least it's not required to, and most will not limit, other than a safety fuse which is usually much greater (at least 25%) - such limiting would also be only a shut off in case of overshoot, EVSE has not way to actually regulate the current), it simply communicates the maximum current to the car's onboard charger. The onboard charger is the one which decides on how much current to draw, which should be at or under the limit from the EVSE. EVSE can change than limit when needed, for example I have 3 EVSE's on the same 100A circuit in my garage. They all talk to each other and split the 80A maximum allowed between the 3 of them. So if I plug in my Taycan, the Taycan gets 80A, but if I plug in my wife's Q8 eTron while my car is charging, the EVSE connected to the Taycan will communicate a new limit of 40A, and the EVSE connected to the eTron will also advertise 40A limit. If my Taycan finishes before the eTron, the EVSE connected to the Taycan will see the session has ended, it will talk to the EVSE connected to the eTron, which in turn will allow the eTron to draw up to 80A.

Now, if my Taycan ignored the advertised limit and continued to draw 80A, the eTron would draw 40A (assuming it didn't ignore the limit) and my fused would blow, as they'd be sucking down 120A on a 100A breaker.

The overshoot of the Macan is not huge, but still there. On a 50A circuit the EVSE would advertise 40A max which is the maximum allowed sustained load by electrical code, but it seems the Macan might ignore it. This would be even worse if if completely ignored the limit (say EVSE says 32A limit and Macan continues to draw 40.7A).

 

[krissrock]

I still dont understand the electric stuff.... But could this advertised 11kw be in reference to the DC port and not the AC?

 

[alxman]

EVSE does not limit (at least it's not required to, and most will not limit, other than a safety fuse which is usually much greater (at least 25%) - such limiting would also be only a shut off in case of overshoot, EVSE has not way to actually regulate the current), it simply communicates the maximum current to the car's onboard charger. The onboard charger is the one which decides on how much current to draw, which should be at or under the limit from the EVSE. EVSE can change than limit when needed, for example I have 3 EVSE's on the same 100A circuit in my garage. They all talk to each other and split the 80A maximum allowed between the 3 of them. So if I plug in my Taycan, the Taycan gets 80A, but if I plug in my wife's Q8 eTron while my car is charging, the EVSE connected to the Taycan will communicate a new limit of 40A, and the EVSE connected to the eTron will also advertise 40A limit. If my Taycan finishes before the eTron, the EVSE connected to the Taycan will see the session has ended, it will talk to the EVSE connected to the eTron, which in turn will allow the eTron to draw up to 80A.

Now, if my Taycan ignored the advertised limit and continued to draw 80A, the eTron would draw 40A (assuming it didn't ignore the limit) and my fused would blow, as they'd be sucking down 120A on a 100A breaker.

The overshoot of the Macan is not huge, but still there. On a 50A circuit the EVSE would advertise 40A max which is the maximum allowed sustained load by electrical code, but it seems the Macan might ignore it. This would be even worse if if completely ignored the limit (say EVSE says 32A limit and Macan continues to draw 40.7A).

So that means you have 2 EVSE’s on one 240 volt line with a 100A breaker? I’m just wondering because we have 1 Tesla charger and I need to plan for when I get the Macan. I’m not sure whether to add another circuit which is expensive, use an adapter (which will only allow to charge one vehicle at a time plus plugging/unplugging each vehicle), or use a splitter like the NeoCharge.

 

[daveo4EV]

I still dont understand the electric stuff.... But could this advertised 11kw be in reference to the DC port and not the AC?

11 kW on baord charger is AC

DC charging is upto 270 kW - and my Macan has done 275 kW once…

this has nothing to do with the DC charger.

 

[daveo4EV]

So that means you have 2 EVSE’s on one 240 volt line with a 100A breaker? I’m just wondering because we have 1 Tesla charger and I need to plan for when I get the Macan. I’m not sure whether to add another circuit which is expensive, use an adapter (which will only allow to charge one vehicle at a time plus plugging/unplugging each vehicle), or use a splitter like the NeoCharge.

Tesla Universal Wall Charger Gen3 - you can "share" upto 6 of them "sharing" a single circuit capacity

this is your path forward…multi-EV household charging happiness

enPhase/ClipperCreek also sell "sharable" EVSE's - multiple EVSE's charing a single circuit capacity (they call it "share2")
WallBox I believe can be configured to share a circuit capacity - you can check the website
maybe others?

but the Tesla one's work great…and make for a great home multi-EV setup.

Tesla Wall Chargers Gen2 can also do this but it requires 2-wires between the unit to communicate the shared load - and Gen2 is not sold anymore - so you'd need to find one on eBay…

I have 3 Tesla Universal Wall Chargers sharing a 100 amp breaker, 80 amps of charging capacity - each unit alone can provide 60/48 amps of charging - but when charing more than 1 EV the 80 amp capacity is split based on actual demand from each EV/Hybrid - works slick…

the communication between the TUWC's is all wireless and automatic once configured.

I routinely charge: Cayenne Hybrid, my son's Model Y, and friend's EV's when they are visiting - and charge them all at once…and the TUWC's just "manage" the load for each EV - the Macan is new and so far it has played nice w/Cayenne both of which have departure time charging scheduled for 6 am and 3 pm (3 pm is the end of my "off peak" rates w/PG&E).

the TUWC are also slick in that they support both J-1777/NACS with a well integrated J-1772 adapter.

https://shop.tesla.com/product/universal-wall-connector - $550 each - they "just work"

each TUWC is maximum 60 amp breaker/48 amps charge rate EVSE - but up to 6 units can be configured to share most any size capacity circuit.

you configure the unit's via built-in web-portal talking the EVSE-wifi hotsport via a web-browser - or you can use the TeslaOne app which is a configuration tool for iOS/Android - https://apps.apple.com/us/app/tesla-one/id1625770308

and yes you can mix/match the Tesla Wall Charger (NACS only) $420 - with the TUWC's - but if buying new I"d suggest the TUWC's cause they suport both north american charging types.

 

[daveo4EV]

So that means you have 2 EVSE’s on one 240 volt line with a 100A breaker? I’m just wondering because we have 1 Tesla charger and I need to plan for when I get the Macan. I’m not sure whether to add another circuit which is expensive, use an adapter (which will only allow to charge one vehicle at a time plus plugging/unplugging each vehicle), or use a splitter like the NeoCharge.

from the Tesla site…

https://www.tesla.com/support/charging/wall-connector/power-management

Group Power Management
Group Power Management is a feature that allows up to six Gen 3 Wall Connectors to share power and charge multiple vehicles at once. Power is distributed across multiple Wall Connectors to minimize charge time for each vehicle while making sure total power being drawn from your panel or a single circuit is within safe limits.
How It Works
Group Power Management wirelessly monitors and controls the total amount of power used by multiple Wall Connectors. All Gen 3 Wall Connector variants are compatible with Group Power Management, and you can use multiple variants in the same Group.
Why It’s Useful
This functionality is ideal for households that need to charge more than one electric vehicle at the same time but may not have enough power for multiple electrical circuits. Installing a single circuit to power multiple Wall Connectors may be the most cost-effective installation, especially when the distance between your parking location and electrical panel is significant.
How to Set Up

• View how to set up Group Power Management in the Tesla One app

 

[alxman]

from the Tesla site…

https://www.tesla.com/support/charging/wall-connector/power-management

So informative! Very much appreciated!

 

[dgkhn]

EVSE does not limit (at least it's not required to, and most will not limit, other than a safety fuse which is usually much greater (at least 25%) - such limiting would also be only a shut off in case of overshoot, EVSE has not way to actually regulate the current), it simply communicates the maximum current to the car's onboard charger.
....
The overshoot of the Macan is not huge, but still there. On a 50A circuit the EVSE would advertise 40A max which is the maximum allowed sustained load by electrical code, but it seems the Macan might ignore it.

So you're saying that if my EVSE is set to 40 amps, and the car tries to draw more, the EVSE will let it? Or even worse, if I have a 16 amp EVSE and hook it to my Macan, and there is some communication error, the EVSE would let the car draw more? That does not seem like a safe design to me.

 

[Dragon Tourniquet]

So you're saying that if my EVSE is set to 40 amps, and the car tries to draw more, the EVSE will let it? Or even worse, if I have a 16 amp EVSE and hook it to my Macan, and there is some communication error, the EVSE would let the car draw more? That does not seem like a safe design to me.

That is what will happen, but at that point the breaker upstream from the EVSE should trip if it goes over that limit, or if it runs hot long enough.

The communication of what charging rate the EVSE supports to the car is just based on resistance, with more resistance meaning less allowed draw. So in theory if something is going to break, the resistor would blow out and then provide infinite resistance, so the car would then "know" it's not allowed to pull any juice at all. Here's a decent page describing it.

 

[daveo4EV]

So you're saying that if my EVSE is set to 40 amps, and the car tries to draw more, the EVSE will let it? Or even worse, if I have a 16 amp EVSE and hook it to my Macan, and there is some communication error, the EVSE would let the car draw more? That does not seem like a safe design to me.

yes - EVSE are more like a water valves (think automated irrigation controllers) and less like a water filters - they do not modify the electrical current/flow/voltage - it’s up to the car and its software to behave! The power from the grid simply flows "through" the EVSE but it's not manipulated or adjusted, filtered, cleaned, modified, folded, spindled, or mutulated - the EVSE's jobs are:

1. report maximum possible current flow to the vehicle to avoid circuit overload
2. guarantee there is no power flowing if it's not plugged into a vehicle - do not electrocute the owner - the charging cord is "Inert" when it's unplugged from the vehicle.

EVSE's do no do much other than the two items listed above - the default North American EV charging standard for AC power L1/L2 is J-1772 - https://en.wikipedia.org/wiki/SAE_J...own as,J1772, SAE Electric Vehicle Conductive

most EVSE's and most EV's speak J-1772 as a common language so that you can using any charger in North America to charge your EV - there is also an ISO standard - and there are EV's and EVSE's that have extended/adjusted the J-1772 standard in various ways, but they all revert to the basic standard if they don't recognize each other (one such example extension is the reporting of current battery % back to the EVSE for display on a screen on the EVSE - this is not part of the J-1772 standard,, but many EV's and EVSE's will provide/display this information if the two parties recognize the extension).

ultimately it’s the circuit breaker that prevent gross over current not the EVSE

the EVSE is simply a glorified on/off switch under control of the car - they do not CHARGE anything - they simply let AC power "fly" or not if the car request they close their circuit to let power flow…what happens after the circuit is closed and power starts to flow I the car's job to deal with - the EVSE is a passive bystander watching it all go by…

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