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SAE J3068/1: Enhancing AC Charging with Vehicle and Supply Equipment Identification
Overview and Communication Architecture
SAE J3068/1, published in 2023, is an optional addendum to the SAE J3068 standard for conductive AC charging of electric vehicles. It introduces Protocol Version 3, which defines signals and logical rules for the identification of vehicles and supply equipment, as well as their affiliation in physically secure environments such as home charging or fleet facilities—often referred to as “behind the fence.” 🔍 This enhanced communication protocol also adds monitoring and diagnostic data fields and enables the exchange of information needed to ensure a vehicle has sufficient energy for its next planned departure.
Protocol Version 3 builds upon the existing SAE J3068 framework, extending the LIN (Local Interconnect Network) based communication with new frames and schedules. The standard defines a comprehensive set of signals for vehicle identification (EvEVCCID), equipment identification (EvEMAID), driver identification (EvDriverID), and various diagnostic and monitoring parameters.
| Field | Description |
|---|---|
| EvEVCCID | Unique identifier for the electric vehicle communication controller |
| EvEMAID | Unique identifier for the electric vehicle supply equipment (EVSE) management entity |
| EvEnergyForDeparture | Target energy required by the vehicle for the next planned departure |
| EvCrc32 | Cyclic Redundancy Check for critical field integrity |
| EvCrcStatus | Status indicator for CRC validation |
| EvHVESSHealth | Health status of the high-voltage energy storage system |
| EvFirstIDPage / EvLastIDPage | Indicators for multi-page identification data transmission |
A key aspect of this standard is its reliance on physical security. Since it is designed for “behind the fence” scenarios, the protocol does not mandate cryptographic authentication, simplifying implementation while assuming that the communication link is protected by physical security measures.
Design Insight: When implementing Protocol Version 3, ensure that the LIN schedule timing is configured to accommodate the additional frames for identification and diagnostics. The standard specifies schedules that alternate between essential charging data and the new identification payloads. Also, payloads like
EvEnergyForDeparture must be computed based on the vehicle’s planned departure time and current state of charge, requiring integration with the vehicle’s navigation or scheduling system.Implementation Considerations and Common Pitfalls
Adopting SAE J3068/1 requires careful attention to several engineering aspects. Backward compatibility with base SAE J3068 must be maintained: devices that support Protocol Version 3 should be able to fall back to earlier versions if the peer does not support the new features. Additionally, the LIN bus schedule must be properly configured to include the new frames within the available time slots.
Common Mistakes ⚠️
- Implementing identification features without ensuring the physical security assumptions (e.g., in public charging stations) can lead to affiliation spoofing.
- Misconfiguring LIN schedule timing can result in incomplete data exchange or communication errors.
- Overlooking the requirement to support Protocol Version 3 if the equipment claims J3068/1 compliance.
- Failing to properly handle extended diagnostic fields such as
EvCrc32may cause incorrect monitoring data. - Assuming that all vehicles support the same set of signals; many fields are optional.
One of the most valuable additions is the ability to communicate departure energy requirements. The field EvEnergyForDeparture allows the EVSE to adjust charging power to ensure the vehicle reaches a target state of charge by a user-defined departure time. This feature is particularly beneficial for fleet operations where duty cycles are predictable.
🛠️ For engineers integrating this standard, it is essential to validate the cyclic redundancy check (EvCrc32) when processing identification and diagnostic data. The standard uses this CRC to protect critical fields, and failure to check it could lead to using corrupted data.
Frequently Asked Questions
1. Can Protocol Version 3 coexist with older versions of SAE J3068?
Yes, SAE J3068/1 is designed to be backward compatible. Devices implementing Protocol Version 3 must support version negotiation and fall back to earlier protocol versions if the counterpart does not recognize the new version. This ensures interoperability in mixed environments.
2. What physical security measures are needed for the identification and affiliation features?
The standard assumes a physically secure environment, such as a private residence or a gated fleet depot. Implementers should ensure that unauthorized physical access to the charging equipment and vehicle communication ports is prevented. If deployed in a public setting, additional security layers (e.g., cryptographic authentication) may be necessary.
3. How is the EvEnergyForDeparture field computed and used?
This field is set by the vehicle based on its planned departure time, current battery state, and anticipated energy consumption. The EVSE uses this information to optimize charging, for example, by delaying charge or reducing power to manage grid load while still ensuring the vehicle reaches the target energy level by the departure time.
4. What diagnostic information is available through the new signals?
J3068/1 adds extensive diagnostic data including battery health (EvHVESSHealth), temperature readings, cell balancing status, and diagnostic trouble codes (EvJ2012Dtc). These fields enable proactive maintenance and fleet management by providing real-time insights into the vehicle’s high-voltage system.
