Tesla's proposed North America Charging Standard plug

Tesla announces the North American Charging Standard charging connector

(November 11, 2022) Today, Tesla Motors made an announcement it seems is meant to solve the issue of electric vehicle charging standards in North America. Tesla’s solution is to unilaterally declare their proprietary charging port is now open for all to use, and that it is now to be called the North American Charging Standard (NACS). Further, Telsa claims to be working with standards bodies to “codify Tesla’s charging connector as a public standard.”

Electric vehicle charging station guide

This will only solve the EV charging problem if all other automakers adopt NACS for their vehicles. The problem Tesla is attempting to solve is that, in North America, there are three different incompatible charging connectors used for DC fast charging, and two different incompatible connectors for AC slow charging.

In most regions of the world there is one charging connector in use, the IEC Type 2 connector, and for DC fast charging there is the IEC Type 2 CCS connector. But, in North America no such decision has been made. Instead, for AC charging there is the SAE J1772 connector as well as Tesla’s charging connector, and for DC charging there is the J1772 CCS, CHAdeMO, and Tesla’s connector. Since CHAdeMO is on its way out that effectively means the DC fast charging market is between J1772 CCS and Tesla’s Supercharger.

Tesla should already know this, but the process they’re following (a unilateral declaration) is not how standards are made. Standards are made when a group of industry stakeholders come together and jointly work out details of how a thing works. They are not made by a single manufacturer unilaterally declaring that their product is the standard.

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The claim Tesla makes is surely true – that the NACS (as they now call it) is the most popular charging “standard” in use in North America. The Tesla supercharging network has, according to Tesla, 60% more charging posts than the combined number of CCS posts from all charging network operators. Vehicles with NACS ports – a.k.a. Tesla Model S/3/X/Y – outnumber cars with CCS ports two-to-one.

In other words, Tesla is claiming legitimacy based on market penetration. Tesla is strongly in the lead and all other electric vehicle manufacturers are playing catch-up.

The key, as we’ll see later, is that Tesla is offering the charging connector as a standard. Tesla has not published documentation of the Supercharger protocol. Instead, the end goal may be to run the CCS charging protocol over the NACS plug. If so, this is an immensely interesting proposal.

Source: Tesla

This image is where Tesla makes its technical case. The Supercharger connector is small, light, and sleek compared to the typical CCS connector. Further, this one connector can be used for every charging scenario from low-power AC charging up to 1 MegaWatt DC fast charging. The latter is for use by the Tesla Semi. By contrast, the CCS connector is relatively heavy, the implementation is a little clunky, and the highest power level for retail consumer use is 350 kiloWatts.

Electric vehicle charging station guide

Tesla’s charging connector policy outside North America

In all other markets than North America, Tesla has adopted the prevailing standard connector. In most of those markets, Tesla initially used their proprietary connector (the one now known as NACS) and later switched connectors on charging posts and in the cars.

In most markets that means the IEC CCS Type 2 connector. This image gives an idea of what we’re dealing with:

Source: Types of electric car charging connectors, and compatibility: A Field Guide to electric vehicle service equipment

The SAE J1772 standard is used in North America and a few other places. The SAE J1772 CCS connector added two pins that carry the DC power for DC fast charging. CHAdeMO was originally designed in Japan and is primarily used by the Nissan LEAF. The IEC Type 2 connector was designed in Germany and has been adopted around the world. For the CCS version, the IEC committee did as the SAE J1772 committee did, and added two power pins for DC fast charging.

This is the issue mentioned earlier about the lack of standardization. In North America, the first and third columns of that picture are the connectors in use for EV charging. It means you can drive up to a charging station and be unable to charge because of incompatible charging connectors.

In most of the world, the IEC Type 2 connector is used, meaning that two variants of the same connector are used by all electric car manufacturers. In those countries, Tesla uses the IEC Type 2 connector because it is the prevailing standard.

In my article, Types of electric car charging connectors, and compatibility: A Field Guide to electric vehicle service equipment, there is a complete survey of all electrical charging connectors, as of November 2019.

I think everyone agrees this is a suboptimal situation. It would be fantastic if all electric vehicle manufacturers would line up behind one standard. As we show on the Field Guide page, Tesla has used the prevailing connector for each region. In China, this means supporting two connectors because in China there are two prevailing charging connectors.

There are two EV manufacturers selling cars in North America which have not adopted the SAE J1772 based charging connector. One is Nissan, whose Nissan Leaf still uses the CHAdeMO standard. In Kia’s case, the Soul EV was sold with the CHAdeMO DC fast charging connector, but for their later electric cars, Kia switched to the CCS connector. Tesla is the other company that has not adopted the SAE J1772 based charging connectors.

For AC charging, Tesla’s charging port (now called NACS) uses the J1772 protocol but through the NACS connector. Unlike what the SAE and IEC committees did, Tesla worked out a method for safely reusing the power pins for either AC or DC charging. Therefore, Tesla’s NACS connector does not require extra pins for DC power.

Analyzing the tech specs Tesla has released

In announcing the North American Charging Standard (NACS), Tesla released some technical documentation. Again, Standards are not made when a company unilaterally declares that something is a Standard. Standards are defined through committees comprising stakeholders from multiple organizations coming to a mutual agreement. At best it is premature for Tesla to call NACS a “standard”, because it has not gone through a standardization process.

Releasing technical documentation and declaring something a Standard is not that kind of process.

Here’s the list of documents Tesla has released:

Screen shot of documentation titles released by Tesla on November 11, 2022

These are:

  • Technical Specification shows detailed technical drawings of the charging connector and charging port, as well as a portion of the charging protocol between the EVSE and the car. This document verifies that Tesla uses J1772 signaling for AC charging, even though it is through the NACS connector.
  • AC/DC Pin Sharing goes over how Tesla manages to use the power pins for either AC or DC charging while doing so safely.
  • The AC/DC Connector Datasheet` are summaries of both connectors.
  • The section marked CAD is data files for CAD software.

Tesla could have taken this information to the relevant standards bodies a long time ago. They did not do so. What’s here is enough for a manufacturer to construct cables. For example, a charging station manufacturer could easily take a level 2 charging station design, and immediately make a version with the NACS connector instead of the normal SAE J1772 connector. No other change would be required in the charging station since for AC charging NACS uses J1772 signaling.

There is, however, a huge glaring omission in the technical specification. Modern EV charging is moving towards using digital data communications between the EVSE and the car for advanced purposes. For example, the ISO15118 standard is being widely implemented to positively identify each car, with one goal being to eliminate the need to scan a charging network membership card to start a charging session. Instead, the charging networks will handle all payments settlement in the background, while you simply drive up to a station and start using it. But, for the car to send the ISO15118 certificate to the EVSE requires something other than simple J1772 analog signals.

The technical specifications Tesla published do not document anything about any advanced data communications.

The behavior of Tesla supercharging stations clearly indicates some advanced data communication happens. The system knows who owns the car so that Tesla can track usage and charge their credit card as needed. Nowhere in the Technical Specifications document is this discussed.

Tesla announces cooperation with standards bodies and manufacturers

Tesla’s announcement opens the door for manufacturers to adopt the NACS plug:

We invite charging network operators and vehicle manufacturers to put the Tesla charging connector and charge port, now called the North American Charging Standard (NACS), on their equipment and vehicles. 

A likely result is for some charging station manufacturers to add cables for NACS charging. That is a trivial task on an AC charging station and would enable charging networks to add NACS charging. That would expand the presence of Tesla-compatible NACS charging ports beyond the Tesla destination charger network.

For a charging network or charging station manufacturer to add support for NACS DC charging requires that Tesla make available the necessary protocol specification. Currently, Tesla has not released this documentation.

The announcement goes on to say:

Network operators already have plans in motion to incorporate NACS at their chargers, so Tesla owners can look forward to charging at other networks without adapters. Similarly, we look forward to future electric vehicles incorporating the NACS design and charging at Tesla’s North American Supercharging and Destination Charging networks.

For the charging network operators, it makes sense to add NACS charging to their offerings. The CNOs can expand their customer base which gives them an opportunity to compete directly with Tesla.

But, does it make sense for vehicle manufacturers to adopt NACS? In 2014, I wrote about how it seems unlikely other automakers would have any incentive to support Tesla’s charging connector. My reasoning is that Tesla’s charging system helps Tesla sell more cars, so why would other EV makers want to help Tesla sell more Tesla cars?

Finally, the announcement said this:

we are actively working with relevant standards bodies to codify Tesla’s charging connector as a public standard. 

Why doesn’t Tesla give the name for the standards bodies in question? And, why do they say “standards bodies” (plural)? And, this statement only covers the charging connector. What about the protocol that drives the Supercharger stations?

What Tesla could have done

Tesla could have chosen a different path, one which would have put Tesla in charge of the largest electric vehicle charging network in North America.

On this path, Tesla would have implemented J1772 CCS connectors on their cars, and on Supercharger stations, just as Tesla has done in most markets where Tesla sells cars. Tesla would need to create an adapter so that existing cars could use the redesigned Supercharger stations.

Another step on this path is to allow anyone with a J1772 CCS car to use Supercharger stations. This would require some kind of authentication so that EV owners can identify themselves to Tesla. The simplest might be to paste QR Codes on each Supercharger station, which would be scanned by a smartphone application, in order to start/manage charging sessions.

At that point, Tesla would be able to earn revenue from the EV owners with J1772 CCS charging ports. Also, Tesla EV owners would be able to use any J1772 CCS station with no adaptor, just as Tesla EV owners in other markets can use IEC Type 2 CCS stations without requiring an adaptor.

The most likely result of Tesla’s NACS announcement

Documents released by Tesla document:

  • The shape of connectors and charging inlets
  • For AC charging they use the J1772 analog signals
  • How to safely reuse power pins for either AC or DC

As we noted already, level 2 charging station manufacturers can add NACS-compatible charging cords with no other change. It’s extremely likely for NACS support to start rolling out among charging networks next year.

But, what about DC charging on public charging networks? Since Tesla has already implemented the CCS protocol, that raises an interesting possibility. DC charging station manufacturers can also add a NACS plug for DC charging, and then it’s a simple matter for Tesla to support CCS over the NACS plug. The charging station manufacturer doesn’t have to implement the Supercharger protocol since it can simply use CCS over this new plug.

In other words, the NACS plug could be used for any charging protocol.

How Tesla could open the Tesla Supercharger network to CCS cars

The theorizing in the previous section raises another possibility. Since Tesla knows how to implement the CCS protocol, it could add CCS charging support to the Supercharger network. This would require additional work:

  • Tesla adds both CCS charging and ISO15118 support to Supercharger stations.
  • Manufacturers add ISO15118 support to their cars — which they are already doing.

In such a case, a CCS car supporting 15118 could connect to a Supercharger station, Tesla would recognize the 15118 identification, and Tesla would then contact their preferred charging network with all fees being settled behind the scenes. For CCS cars that do not have a NACS port, it may be possible to construct a simple adapter between the NACS plug and the SAE J1772 CCS charging port.

In other words, Tesla may well be planning to do what was said in the What Tesla could have done section above.

Summary

Why do we expect electric vehicle makers to also own charging networks? This is not how gasoline car refueling is handled.

For gasoline cars, there are standardized nozzle shapes allowing anyone to refuel at any gasoline station. The car companies do not own refueling stations. Instead, there is an open market for all companies to participate.

Why should electric vehicle charging be any different?

There has been a discussion since at least 2014 between Tesla and other automakers about charging standards. For example, it was reported in June 2014 that BMW, Nissan, and Tesla held talks about Supercharger network collaboration. In 2017, JB Straubl (at the time Tesla’s CTO) said the company was working with other automakers on charging network collaboration.

Remembering these older announcements makes one wonder about the behind-the-scenes discussions leading to Tesla making this announcement.

I started this article griping about Tesla unilaterally bypassing the standardization process, and unilaterally announcing its proprietary charging plug as a standard. But, after looking carefully at this announcement it looks extremely interesting.

The NACS plug is clearly more attractive and user-friendly than either the CCS or CHAdeMO plugs. The key to making the NACS plug attractive to the rest of the industry is to realize that it can be used for implementing other charging protocols. We theorized earlier that NACS could be used by the CCS protocol for DC Fast Charging, making it possible for both public charging networks and Tesla’s Supercharger network to implement CCS charging over the NACS plug.

So long as Tesla will not monopolize the charging networks, then the adoption of the NACS plug will be very good for electric vehicle adoption.

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.

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