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FHWA announces RFI on updating federal standards for EV charging; specifically looking at NACS

The Federal Highway Administration (FHWA) announced a Request for Information (RFI) to solicit feedback from stakeholders on updating FHWA’s minimum standards and requirements for electric vehicle EV charging stations to allow for new technology and continued innovation.

The RFI focuses on the types of connectors used at federally-funded EV chargers. Current federal requirements allow for alternative types of connectors on all federally-funded DC Fast Chargers so long as there is also a Combined Charging System (CCS) connector.

SAE International has begun the process of developing a standard, SAE J3400, based on Tesla’s North American Charging Standard (NACS) connector. In December 2023, SAE International released the SAE J3400 Technical Information Report, and expects the final standard to be published sometime in late 2024. (Earlier post.)

Many automakers have announced they will adopt this connector standard on vehicles beginning in 2025, with adapters available for current owners as soon as spring 2024. The RFI will help inform how FHWA can best incorporate new technologies and innovations such as J3400 into its minimum standards and requirements for federally funded EV charging stations, continuing to ensure that the national EV charging network serves consumers well now and into the future.

Through the RFI,  in coordination with the Joint Office of Energy and Transportation and the Department of Energy, FHWA is seeking information in several key areas:

  1. expectations surrounding market availability for J3400 within EVs and EV chargers;

  2. technical compatibility of J3400 with existing regulations;

  3. considerations regarding challenges and benefits of the implementation of J3400 at charging stations;

  4. market demands for the continued availability of Combined Charging System (CCS) and J1772 connectors; and

  5. potential options for performance-based standards that can reduce the need for future regulatory updates or changes as technology evolves.

Comments must be received on or before 5 April 2024.



There is a discussion of charging losses here:


Bottom line is that plugging into a wall socket without a wall box is very lossy.

Not much discussion there on the varibility of charging losses at different temperatures, which I would have thought substantial.

Batteries have a tough time where it gets very cold much of the time.


Yes, charging from a single phase 120V socket in North America is very lossy, but it's not a common thing. It would also take a very long time, given the typical 15A 120V circuit in the US (with a safe limit of around 1500W continuous). It's something you might do in an emergency, to get just enough "juice" to move a car to a real EVSE. Maybe some new EV owners might charge on 120V during the short interim before they install a 240V circuit.

It goes without saying that other fuel sources have similar losses via evaporation, spillage, etc. I read an estimate that up-to a quarter of the BTU content of natural gas escapes (untreated) between the wellhead and the end-user. Gasoline extraction is equally wasteful, with horrendous environmental consequences. Hydrogen could potentially be worse, since it's inherently inefficient to produce, and more prone to leakage than natural gas. A mere 10% loss for EV charging starts to look quite good when you consider the alternatives.


NEC should require circuits that are likely to be used for EVSE at 120V have oversized conductors.
I charge at about half the capacity on my 240V EVSE so that results in 1/4 the losses (I^2 x R).



Circuits that are likely to be used for EVSEs should never be 120V, although arguably all outside plugs should be 20A circuits since they are likely to be used for high-demand loads like lawn mowers and other electrical tools.
240V is the default power feed in North America, although 208V is sometimes used in three-phase commercial and apartment buildings. Any EVSE circuit should be 240V, just like other large consumers (AC, water heater, stove).

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