Safety and Standards
Safety is essential when dealing with the high voltage electricity required to charge EVs. This includes new nationwide building and electrical standards and codes which specify where equipment can be placed, and details the standard safety features required of EV charging systems and supply circuit requirements. The United States National Electric Code (U.S. NEC), shown in Appendix A, must be followed when designing and installing EVSE. Charging equipment has undergone rigorous testing to establish the durability and safety for the consumer. In addition, considerable training and outreach materials have been established to ensure that EV infrastructure installed statewide meets the safety standards established (20).
An important safety and standard aspect of EV charging is the connection between the supply equipment and the EV. The Society of Automotive Engineers, SAE International, has developed SAE J1772, model shown in Figure 38. This is a North American standard for electrical connectors for EVs which is titled “SAE Surface Vehicle Recommended Practice J1772, SAE Electric Vehicle Conductive Charge Coupler”. It covers the general physical, electrical, communication protocol, and performance requirements for the EV conductive charge system and coupler. The intent is to define a common EV conductive charging system architecture including operational requirements and the functional and dimensional requirements for the vehicle inlet and mating connector (21). The connector is designed for single phase electrical systems with 120V or 240V such as those used in North America. It is designed to support electrical current up to 70A. The round 43 mm diameter connector has five pins and will support communication over power lines to identify the vehicle and control charging. The connector is designed to withstand up to 10,000 connection/disconnection cycles and exposure to all kinds of elements. Approximating one connection/disconnection cycle daily, the average connector’s lifespan should be just over 27 years.
Figure 40: SAE J1772 Connector
However, this connector does not work for a three-phase DC fast charge. There are currently no international standards for voltages and currents or connectors for plug-in vehicles; however, standards should come soon (22). According to SAE International, the SAE J2293 – Energy Transfer System for EVs will be used for DC fast chargers and is still in the process of being finalized (23).