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SAE J2836-2: Use Cases for Communication Between Plug-in Vehicles and Off-Board DC Chargers
SAE J2836-2 is an SAE Information Report that establishes the use cases and general information for communication between plug-in electric vehicles (PEVs) and off-board DC chargers. This standard focuses on conductive DC charging, detailing the communication sequences, inband signaling, and power line communication (PLC) methods used to enable safe and efficient energy transfer. Developed specifically for forward power flow (grid to vehicle), J2836-2 serves as the foundational use-case document that informs the implementation protocol in SAE J2847-2.
Scope and Purpose
The standard applies to off-board DC chargers that supply DC current to the vehicle battery through an SAE J1772 hybrid coupler or SAE J1772 AC Level 2-type coupler on DC power lines. It covers communication over AC power lines, the pilot line, or dedicated lines as described in SAE J2847-2. The purpose is to document general information that must be supported by the recommended practice in SAE J2847-2, including interactions between the vehicle and driver where relevant.
🔍 Important Distinction: J2836-2 defines the what (use cases) for communication, while J2847-2 defines the how (protocol details). Do not use this document to specify implementation protocol; that belongs in J2847-2.
Architecture and Communication Sequences
J2836-2 outlines distinct architectures for AC charging, DC Level 1, and DC Level 2. Each architecture is designed to ensure appropriate communication paths and power delivery. The standard describes two primary communication methods:
- Inband Signaling: Communication over the pilot line, typically using the pilot duty cycle to convey information such as available line current (ALC).
- Power Line Communication (PLC) over Mains: High-speed data communication over the AC power lines using a dedicated PLC modem, as specified in SAE J2931/4.
Sequence diagrams in the standard illustrate the steps for establishing communication and applying power, including inband signaling sequences and PLC-based communication sequences.
| Aspect | DC Level 1 | DC Level 2 |
|---|---|---|
| Communication Path | Pilot line (inband signaling) or PLC over mains | PLC over mains (primary); inband signaling also supported |
| Power Level | Up to 200 A (based on circuit breaker and ALC) | Up to 400 A (higher power DC charging) |
| Coupler | SAE J1772 hybrid coupler | SAE J1772 hybrid coupler with additional pins |
| Use Case Reference | Forward power flow (grid to vehicle) | Forward power flow (grid to vehicle) |
Engineering Design Insight: When designing an off-board DC charging system, ensure that the use cases defined in J2836-2 are fully supported by your implementation. The architecture diagrams emphasize the need to separate AC and DC communication paths to avoid interference. Pay close attention to the sequence diagrams, as they define the required handshake for initiating charging safely.
Relationship to Other Standards and Forward Power Flow
This document references several other SAE standards, including SAE J1772 for the hybrid coupler, SAE J2836/1 for utility grid use cases, and SAE J2847/2 for the actual communication protocol. It is important to note that J2836-2 addresses only forward power flow (grid to vehicle). Reverse power flow (vehicle-to-grid) is covered in other documents in the J2836 and J2847 series.
Frequently Asked Questions
FAQ
What is the difference between SAE J2836-2 and SAE J2847-2?
SAE J2836-2 is an Information Report that defines the use cases and general requirements for communication between a plug-in vehicle and an off-board DC charger. SAE J2847-2 is a Recommended Practice that specifies the actual communication protocol, messages, and implementation details. J2836-2 provides the foundation that J2847-2 must support.
What communication methods does J2836-2 cover?
The standard covers inband signaling over the pilot line and power line communication (PLC) over the AC mains. These methods are used for establishing communication, exchanging status information, and managing power transfer.
Does J2836-2 apply to vehicle-to-grid (V2G) scenarios?
No. J2836-2 specifically addresses forward power flow (grid to vehicle) for DC charging. Reverse power flow (vehicle to grid) is covered by SAE J2836/3 and SAE J2847/3.
How does this standard relate to SAE J1772?
SAE J1772 defines the physical coupler requirements for conductive charging. J2836-2 relies on the J1772 hybrid coupler for DC Level 1 and Level 2 charging, and references J1772 for connector and pilot line specifications.
🛠️ By understanding the use cases in J2836-2, engineers can design DC charging systems that are interoperable and compliant with the broader SAE electric vehicle communication standards.
