SAE releases new J3068 specification for charging of medium- and heavy-duty EVs

SAE International has published its recommended practice for plug-in charging of heavy-duty EVs. The new J3068 standard allows vehicles to fully utilize three-phase AC power.

Presenting a symmetric three-phase load enhances grid stability, especially at high power levels. SAE J3068 standardizes an AC three-phase-capable charging coupler and digital control protocols, offering sufficient power and reliability for the commercial vehicle market.

Existing technology is combined to provide higher power than existing charging solutions from the passenger car sector, with added diagnostics. DC charging on separate contacts with PLC controls is also described, as is limited three-phase AC charging with PWM controls, providing interoperability with J1772 protocols where possible.

SAE J3068 provides for:

  • A higher-power version of an existing charge coupler, for example 133 kW at 480 VAC 160 A three-phase.
  • Bidirectional digital communication between EV and EVSE via single-wire baseband signaling for local control.
  • Grid supply voltage is signaled before the EV and Supply Equipment agree to charge. For example, in Canada 600 VAC is more common than 480 VAC but not all EVs can use 600 VAC.
  • Independent control of current limits on a phase-by-phase basis. For example, this enables the minimum overall de-rate when only one phase leg has the available current restricted by the utility.
  • The EV may signal requested current, to enable a power management system to balance loads better. A minimum power requirement communication option supports fixed loads such as refrigeration, which cannot control current draw other than in an on-or-off fashion.

“This new standard was designed to offer a single vehicle inlet solution for three-phase and single-phase AC and DC charging for a class of vehicles,” said SAE J3068 Task Force Chairman Rodney McGee. “We wanted to combine this new approach for AC charging with 1,000 V DC charging based on existing SAE communication standards.”

“The goals of J3068 include bringing a proven, mass produced three-phase charging coupler to North America, and establishing a low-cost, reliable communication and control protocol for AC with inherently high interoperability,” said Document Sponsor Jim McLaughlin. “High-power AC charging has cost advantages in many use cases, and three-phase charging simplifies balancing of the power grid.”

 

Source: SAE International

  • freedomev

    These vehicles only need 1 plug, a DC. Anything else they have to carry their own charger who’s weight, space, cost is better used somewhere else in these sizes.

    • Olivier Fontaine

      Peoples complaints about the lack of flexibility and amount of chargers, Tesla is about to open to others brands… Good idea but maybe later (DC only). EV vehicule era is just begining, this new standard is filling a gap. At least it is standarized for all North America.

    • jamcl3

      Every EV has an integrated “charger” on board that is used for regenerative braking. It is possible to use the motor controller to charge the battery from the grid instead of the electric machine. It does not add much to weight or cost, but it can complicate the optimization of the design. Off board DC charging adds system cost that is unnecessary, at least theoretically. Time will tell if integrated AC charging will be more competitive. These are early days, there is much innovation yet to come. And in almost every application, regardless of light or heavy duty, AC charging is more important.

      • freedomev

        Very true but they don’t seem to be doing it that way. ACPropulsion did this back in 1997 at least and was with V2G, put into the Ford E Ranger . So certainly not it or V2G are new.
        Many UPS systems work that way, reversible inverter, charger.
        They did limit it to 15kw but likely the limit of the plugs they were able to use then, stove, RV style outlets at 50 amps, 240vac.
        Which I wish they would still use instead of the expensive ones they do use for level 2 charging.
        But having a DC charger offboard that does 100+ kw is as good and only costs more because the makers are greedy.
        I can build a 300kw one for about $4k for instance as DC-DC are not expensive. The Zilla would do the job, an EV racing DC controller, for just $2k retail hand built. Much less without all the EV stuff and mass produced.
        The rest is just case, cord, comm board, contactor and breaker.

  • DIY ev

    Good point in below comment. Reduces the flexibility of charging at any charging station. J1772 will still work best.
    This new version is good for on the premisses charging and that is about it.. Please remember that most chargers are stackable and you can design to plug into multiple J1772 saving tons of money and problems.
    When I use to drive around my all electric 19,500 GVW truck using, 210KW AC liquid cooled motor, 240KW liquid cooled controller/inverter, 140KWH 560VDC powered battery pack, I had a J1772 and I would charge it everywhere.

  • nordlyst

    133 kW? This is a joke.

  • RT McGee

    J1772 passenger car infrastructure can used when needed in the came way Tesla drivers do it, with an adapter.

    But remember trucks and buses don’t really fit into the parking spots for EVs and much as we wanna talk shared infrastructure Chevys Volts will not be charging next to Class 8 trucks very often. Generally these two don’t even occupy the same general area in a parking lot.