Gen 3 Charger Power Sharing - who has this working?

[Rocky_H]

If I use the Lectron Tesla to J1772 adapter to allow for non-Tesla vehicles to charge is is going to work? Adapter link
I think the question is really more something like :

• Is the Wall Connector itself discovering the required power of each vehicles
• Is the vehicle supposed to request an amount to "ask" the charger
• Is the charger (Wall Connector) required to actually negotiate with the car to handle power sharing? (In which case, yeah I see using an adapter might be a problem)

The electrician I was talking with seemed to say that using an adapter would prevent the charger to talk with the vehicle and so it would not work, but honestly he did not seem too sure and just wanted to be on the safe side.

Those are good questions, but the answers are kind of unclear and muddy, and unsurprisingly, the problems are because of differences between how Tesla promised the feature would work, versus what it actually does in implementation. It was supposed to be this very active and dynamic and full-featured thing, which would do the following:
Two-way communication with all of the cars to detect their states of charge as inputs.
Shifting the amounts of amps around frequently and dynamically.
Giving priority to refilling the car with lowest state of charge sooner.

But in implementation, people have reported several behaviors that aren't that.
One thing seems to be a limitation in the J1772 protocol that it uses. Any vehicle that is plugged in has 6A allocated to it always, even if it's not being used. So if two cars are plugged in with 48A available, there are 6A set aside not being used for a full car, while the other can only get 42A at most.

The dynamic shifting of amps from more going into the emptier car toward more even split I don't think has ever worked. The best people have seen is just a simplistic 1/N splitting among the N number of wall connectors.

And then I think there are still problems where it won't reallocate once one of the cars hits full and stops charging. So two cars were getting 24A each, but when one car hits full and stops, the other car stays stuck at 24A unless someone goes and unplugs the full car to give a kick to the head to the system to make it look at what it is supposed to be doing again.

However, I would say that if it doesn't honor the splitting of the charge it would be a danger to use and thus I would have to assume it works. Of course, assume but verify

Fortunately, that seems to be a problem it has NOT had. As far as I have heard, all of these behaviors are still honoring the total limit of the entire system, and I haven't heard of any installations of them overshooting that. They just aren't being as cool and smart about the allocation as they were supposed to be.

 

[Fosomo]

I wanted to revive this thread to share my actual experience.

I finally got to have my stuff installed and could confirm compatibility.
Here is my setup :

• One 60A breaker on my panel
• 2 x Tesla Wall Connector Gen3 plugged on the same breaker (all installed by a certified electrician)
• Connectors are setup in Power Sharing mode, 48A (80% of the breaker) available for charging IN THE GROUP
• Plugging a Tesla in either one of the chargers will offer full charge of 48A (yay)
• Plugging 2 Teslas on the chargers will automatically share the load
  • I only saw 24A + 24A
  • I don't know if it will modulate depending on demand, but honestly I don't really care, half charge is good enough for me
• Now the kicker, plugging a Tesla and a Ford Mustang Mach E with a Lectron adapter
  • Works like a charm, I was scared communication would not work and sharing would be controlled by the cars maybe
  • As soon as I plug the Mach E, I see the Tesla drop to 24A
  • All is well

So the setup works, just needs to configure the sharing properly, which is super easy following the documentation.

Hope that helps someone!

 

[brkaus]

@Fosomo Thanks for the update and confirmation! I do feel like an even split is the right answer. Anything else will be "wrong" a good portion of the time anyway.

 

[Rocky_H]

@Fosomo Thanks for the update and confirmation! I do feel like an even split is the right answer. Anything else will be "wrong" a good portion of the time anyway.

I don't agree with that one. Sure, the attempted dynamic shifting up and down might be problematic and wrong a lot, but the wall connector should know if it is literally providing nothing because the car it's hooked up to is asking for nothing. It should be able to signal that it's not being used and let the other one go full power.

 

[STS-134]

One thing seems to be a limitation in the J1772 protocol that it uses. Any vehicle that is plugged in has 6A allocated to it always, even if it's not being used. So if two cars are plugged in with 48A available, there are 6A set aside not being used for a full car, while the other can only get 42A at most.

The J1772 needs to advertise at least 6A, but the EVSE isn't obligated to actually deliver it. I was plugged into the ChargePoint system at the SFO long term garage (shared power) and I saw it advertise everything from 6A to 30A. It never actually advertises less than 6A, however it does actually deliver 0A at times. I always get multiple notifications that "charging was stopped with battery at X%" in my Tesla app when the ChargePoint EVSE cuts power. If I try to go into the Tesla app and "start charging", the app will respond that the car has requested charging but the EVSE isn't delivering, and if I think there's a problem, I should check the EVSE. Of course, charging does eventually start back up, but it does this when the EVSE feels like delivering power again.

 

[The banker 31]

I know this is old, but I wanted to revisit this topic again as there are a lot of miss informations about each wall connector supposed to have its own circuit breaker.

Here in the Wall Connector guide it says the following:

Power sharing is ideal for households that need to charge more than one Tesla at the same time, but may not have enough power for multiple electrical circuits. This functionality allows up to four Wall Connectors to share power from one circuit while still allowing your vehicles to receive a sufficient charge.

Wall Connector

The Tesla Wall Connector is the most efficient way to charge a Tesla at home — just plug in your vehicle overnight and wake up to a charged vehicle.

www.tesla.com

I have had Power Sharing working with two gen 3 Wall Connectors connected to one 60amp breaker.

Each Wall Connector is setup to its maximum allowable amp (60 amps for 48amps continuous)

When both cars are connected which ever car has the lowest charge requests more energy. Both Wall Connectors never exceed the maximum supply amp (in my case 48 amps between the two).

As soon as one car is fully charge, the other car gets all 48amps assigned.

Hi Raiden if I may reading your post that is exactly what i was looking to do right or wrong using the same line and splitting 2 ways no sub panel. Now this post dates back some time so how is that working for you. Did you run into any issues or is everything working well between the 2 gen3's? Thx

 

[RudeDude]

So the setup works, just needs to configure the sharing properly, which is super easy following the documentation.

Hope that helps someone!

Thanks @Fosomo your post was helpful. I also went digging into the very newest NFPA / electrical code for 2023 and saw that they rearranged things a bit. At least in part to have code for things like the Ford Lightning providing backup power through an EV charging system. So, yeah, code allows for it as long as you have a way to limit the total current which the Gen 3 will do. The installation manual for the Gen 3 WC doesn't make it clear that it is allowed with their drawings. So, that is why your post was helpful... its not like you wired it up and the WCs talked to each other or interfered with each other about being on the same breaker (branch circuit).

Based on the 2023 code we are supposed to have a label on the supply (breaker box) indicating the max setting and the fact that this circuit has an EMS on it.

For whatever its worth I'll post the section numbers and my summary notes from the electrical code. I am NOT a lawyer and I am NOT a licensed electrician! The sentences are my truncation of the original language!

NFPA free access
NFPA section 70 (National Electrical Code)
Year 2023

NFPA LiNK®

The leading information and knowledge resource on fire, electrical and related hazards.

link.nfpa.org

220 Branch circuit load calculations
220.70 Energy Management Systems (EMSs)
- Re: 750.30, a setting permitted...
- Setpoint of EMS shall be considered a continuous load.

220.57 EVSE load
- Shall be calculated at either 7200 watts or the nameplate rating
- Whichever is larger

Chapter 6: 625 Electrical Vehicle Power Transfer System
Part III: Installation
625.40 Electric Vehicle Branch Circuit
- Each circuit supplying EVSE greater than 16 amp or 130 volt must have its own branch circuit
- Except: 625.42.(A) or (B)

625.42 Rating
- EVSE shall have sufficient rating to supply the load.
- Considered as continuous loads.
- Service and feeder shall be sized for product ratings except 625.42(A) or (B)

625.42 (A) Energy Management System (EMS)
- EMS in accordance with 750.30 for load management
- Maximum of circuit as set in EMS.
- Permitted to be integral to one piece or multi-piece system.
- System shall be marked to indicate load management controls.

625.42 (B) EVSE with Adjustable Settings
- Amp adjustment means to comply with 750.30(C) permitted.
- Allowed amp ratings equal to the adjusted current setting.

750.30 Load Management
- EMS permitted to monitor and control loads and sources with (A) through (C)

750.30 (A) Load Shedding Controls
- EMS shall not override load shedding controls of fire pumps, emergency systems, etc.

750.30 (B) Disconnection of Power
- An EMS shall not cause disconnect of elevators, escalators, hazardous ventelation, etc

750.30 (C) Capacity of Branch Circuit, Feeder, or Service
- An EMS shall not cause it to be overloaded
- Is limiting current sections (C)1 through (C)4 shall apply

750.30 (C) 1 Current Setpoint
- A single value for max amps for:
(1) Calculating connected load per 220.70
(2) For max source current permitted by EMS control

750.30 (C) 2 System Malfunction
- EMS shall automatically cease current flow upon malfunction of the EMS

750.30 (C) 3 Settings
- Adjustable settings shall be permitted if access to settings is one of
(1) Located behind removable and sealable cover
(2) Located behind cover or door that requires tools
(3) Located behind locked doors limited to qualified personnel
(4) Password protected limited to qualified personnel
(5) Software with password protection limited to qualified personnel

750.30 (C) 4 Marking
- Equipment supplying the branch circuit marked with
(1) Maximum current setting
(2) Date of calculation and setting
(3) Identification of loads and sources under control
(4) "The setting for the EMS current limiting feature shall not be bypassed."

 

[rwojo]

For whatever its worth I'll post the section numbers and my summary notes from the electrical code. I am NOT a lawyer and I am NOT a licensed electrician! The sentences are my truncation of the original language!

You rock!

I mentioned on the other thread that anyone interested in this should see if Telsa can provide guidance on installation on the same branch with the new clarified NEC 2023 rules, as it goes against their manual which hits 111.3(B) saying which says "Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling."

 

[RudeDude]

I agree with @rwojo . I'm not sure what path to try and reach Tesla on this topic but their manual makes it pretty clear that they are talking about one branch per TWC but newer electrical codes mean you can share a branch. I'm just glad the two TWC's didn't do their line tests and freak out having detected the shared branch or something . Now that I have my Model 3 I can show data (if someone wanted to see it) where I can pull 48 amp from Model-Y *or* 32 amp from Model-3 *or* some blend of the two, namely 24A plus 24A.

 

[rwojo]

I agree with @rwojo . I'm not sure what path to try and reach Tesla on this topic but their manual makes it pretty clear that they are talking about one branch per TWC but newer electrical codes mean you can share a branch. I'm just glad the two TWC's didn't do their line tests and freak out having detected the shared branch or something . Now that I have my Model 3 I can show data (if someone wanted to see it) where I can pull 48 amp from Model-Y *or* 32 amp from Model-3 *or* some blend of the two, namely 24A plus 24A.

How does it work when a car is fully charged? It still requires the 6A or whatever per connected EV right?

Any limits on the network load limit? Can you enter 44A and will it negotiate 44A to a single car for example (for NB-B that can't do full 48A).

 

[brkaus]

How does it work when a car is fully charged? It still requires the 6A or whatever per connected EV right?

Any limits on the network load limit? Can you enter 44A and will it negotiate 44A to a single car for example (for NB-B that can't do full 48A).

It has the same limits as a standard WC. 44a is not one of the options.

 

[RudeDude]

When setting up the master / slave TWC and the shared circuit limit I believe I could have entered any integer for circuit total amp limit. I entered 48 (60 amp breaker, 80%). Therefore the two TWC's with two cars plugged in will self limit to 24A each if both cars are trying to pull max.

Yes there is also an assumed 6A minimum required draw from each TWC. I did also find that they will "re-balance" dynamically but slowly. The test I did was both cars were pulling 24A. I stopped the Model-Y charge but left it plugged in. The Model-3 slowly ramped up its draw from 24A to 32A (its own max).

 

[rwojo]

Hmm, so either any integer or the same options. Which one is it?

 

[brkaus]

Hmm, so either any integer or the same options. Which one is it?

Well, the manual says to follow the basic commissioning procedure on one WC first. And the basic commissioning feature specifies breaker size.

But it also mentions a network max and doesn’t say if it’s breaker based.

So the answer maybe both???

 

[RudeDude]

If you are setting up a single TWC then you choose the setting from the UI. When setting up power sharing (on what now becomes the master) you use a different part of the UI to set max amps for the shared circuit. This is where you can type an integer of your choice. The theory here (according to the manual which doesn't acknowledge sharing a branch) is that all the TWC's in one panel / sub-panel might overload the system not the branch breaker(s). So, I never really completed the "stand alone" setup for what became the slaved TWC. At least I don't clearly recall logging in and doing the provisioning... maybe I did.

Once you scan the photo of the secondary unit and send it to the primary unit then you can no longer really login to the commissioning GUI of the secondary.
Or, if you can, it wasn't working well for me.

 

[rwojo]

That is interesting. I read that you can set each unit, e.g. a slave unit matching the breaker it is on. Example:

Network: 48A
Master: 48A
Slave: 40A
Slave: 48A

In that case you'd have to set the slave units individually to match the breaker in the sub-panel.

Not going to matter for me since I'm planning on splitting a single branch so all units will be at the same max amperage.

 

[brkaus]

That is interesting. I read that you can set each unit, e.g. a slave unit matching the breaker it is on. Example:

Network: 48A
Master: 48A
Slave: 40A
Slave: 48A

In that case you'd have to set the slave units individually to match the breaker in the sub-panel.

Not going to matter for me since I'm planning on splitting a single branch so all units will be at the same max amperage.

I’ve read this as well. And there is also an option to set a max for the group.

 

[rwojo]

Hopefully someone is willing to document a re-commission of their units or new setup so we can have a little more clarity. I'll make sure to do it once I get another WC

 

[rwojo]

So one interesting scenario with 6/2 MC.

80% of the rated 65A @ 75C for the 6/2 MC results in 52A. Can I set the network limit to 52A, and the units left at 48A?

Not sure if it helps though with two cars connected. The minimum is 6A for each car connected to a HPWC, leaving 46A for the other car which may not even be a valid negotiation option? Will it downgrade to 40A which is the nearest "standard" value?

 

[rwojo]

Another aside is using power sharing with just one unit lets you squeeze out 4A more because you can set the unit to 48A but the network to 44A to match code for 6 NB-B. Neat.

UPDATE: You can't do this with one unit, I just tried. Power Sharing requires another unit to set up, so I have no option to set 44A for a single unit. Well darn!