This SAE Recommended Practice SAE J2847-2 establishes requirements and specifications for communication between plug-in electric vehicles and the DC Off-board charger. Where relevant, this document notes, but does not formally specify, interactions between the vehicle and vehicle operator.
This applies to the off-board DC charger for conductive charging, which supplies DC current to the vehicle RESS of the electric vehicle through a SAE J1772™ Hybrid coupler or SAE J1772™ AC Level 2 type coupler on DC power lines, using the AC power lines or the pilot line for PLC communication, or dedicated communication lines.
The specification supports DC energy transfer via Forward Power Flow (FPF) from source-to-vehicle.
This is the 1st version of this document and completes step 1 effort that captures the initial objectives of the SAE task force. The intent of step 1 was to record as much information on “what we think works” and publish. The effort continues however, to step 2 that allows public review for additional comments and viewpoints, while the task force also continues additional testing and early implementation. Results of step 2 effort will then be incorporated into updates of this document and lead to a republished version.
The SAE J2847-1 document supports AC or DC energy transfer identifying communications from the utility to the charger. The SAE J2847-2 document supports the additional messages for DC energy transfer. The SAE J2847-3 document supports RPF and this series is based upon requirements jointly developed by vehicle manufacturers, electric utilities, grid operators, technology suppliers, and other stakeholders. These requirements are reflected in SAE Information Report SAE J2836-1™, Use Cases for Communication between Plug-in Vehicles and the Utility Grid. These requirements fulfill the use cases described in SAE J2836-2™, Use Cases for Communication between Plug-in Vehicles and Off-Board DC Charger.
Whereas SAE J2293 focused on communication between the vehicle and local, off-board electric vehicle supply equipment (EVSE) with optional grid interaction, SAE J2847-1, SAE J2847-2 and SAE J2847-3 focuses on communication between the vehicle and grid, with the EVSE playing the role of local intermediary. Additionally, while SAE J2293 included support for SAE J1773-based inductive charging and SAE J1850-based communication, these are obsolete and hence not supported by SAE J2847. In order to maintain information for existing systems, this task force has reaffirmed SAE J2293, preserving that specification at its last revision level.
This specification addresses major changes that have occurred since 1997 (when SAE J2293 was published) in the technologies of electric vehicles, the grid, and information processing, including: (1) support for bi-directional energy transfer between vehicle and grid (FPF and RPF, as defined above); (2) support for new local communications media between vehicle and EVSE (to replace SAE J1850), such as power line communication (PLC), Controller Area Network (CAN), and wireless transports (Zigbee, WiFi, etc.); (3) synchronizing with a major revision of SAE J1772™ which includes new connectors and signals between the vehicle and EVSE, and additional AC and DC power levels; (4) support for new vehicle architectures such as plug-in hybrid (PHEV) and plug-in fuel cell (PFCV) vehicles; (5) support for new rechargeable energy storage system (RESS) technologies and packaging methods; (6) support for vehicle telematic communication transports; and (7) support for new developments in both utility and customer premises equipment, such as advanced metering infrastructure (AMI) and home-area network (HAN) technologies.
The above changes and others require a new approach to vehicle-grid communications and provide the fundamental rationale for this specification.
In the context of this document, the DC Supply is considered an extension of the on-board vehicle systems. For the most part, the DC supply acts in response to vehicle requests; it does not act autonomously. The DC Supply does not contain intelligence about the RESS system or specific vehicle operation. It only mitigates some safety related concerns that it is able to self detect (isolation), and it conforms to the vehicle established charge session limits (from handshaking). Primary control of the charging output is dictated by the vehicle control system.