V2X Communication Protocols to Enable EV Battery Capacity Measurement: A Review

The US EPA and the California Air Resources Board (CARB) require electric vehicle range to be determined according to the Society of Automotive Engineers (SAE) surface vehicle recommended practice J1634 - Battery Electric Vehicle Energy Consumption and Range Test Procedure. In the 2021 revision of the SAE J1634, the Short Multi-Cycle Test (SMCT) was introduced. The proposed testing protocol eases the chassis dynamometer test burden by performing a 2.1-hour drive cycle on the dynamometer, followed by discharging the remaining battery energy into a battery cycler to determine the Useable Battery Energy (UBE). Opting for a cycler-based discharge is financially advantageous due to the extended operating time required to fully deplete a 70-100kWh battery commonly found in Battery Electric Vehicles (BEVs). This paper provides a review of the communication protocols enabling V2X (Vehicle to X, where X can be grid, vehicle, building, etc.) power transfer and the tools required to initiate, control, and terminate the vehicle testing procedure as per SAE J1634. The primary focus is on the series of ISO 15118 standards for road vehicles - vehicle to grid communication interface and SAE J2847/2 (Surface vehicle standard for communication between plug-in vehicles and off-board DC chargers).