ISO 15118-20 works to smooth some of the current stumbling blocks with EV connectors.

 

By Caitie Romano

The EV industry is relatively new and still evolving. That creates challenges of compatibility and interoperability for EV and EVSE manufacturers, related to both the data interface and the various connectors.

However, the ISO 15118-20 standard, which is an interface between the vehicle and charging provider, works to eliminate many of those challenges as it facilitates charging features.

 

Defining Communications

The ISO 15118 standard defines the power and communication interface between a battery-powered electric vehicle (BEV) or plug-in hybrid electric vehicle (PHEV) and the electric vehicle supply equipment (EVSE), the charger or charging station. The ISO 15118-20 standard, an update of the ISO 15118-2 standard, defines the communication protocol between the EV and the EVSE.

Key features in the standard that facilitate convenient, secure and efficient charging include:

  • Plug and charge (PnC) seamless authentication and billing, which allows automatic identification, authentication and billing.
  • Secure communication using encrypted data exchange prevents user information from unauthorized access.
  • Bidirectional energy flow, so energy goes to the vehicle for charging and back to the power grid for load balancing and energy storage.
  • Dynamic power management enables the EV to request a specific charging power based on the state of the battery, the power capacity of the EVSE and demand on the grid.
  • Smart charging for load management, which includes charge scheduling and modifying the charging rate based on grid conditions and use of renewable energy to optimize energy use and reduce costs.
  • Cross-manufacturer compatibility provides interoperability between different manufacturers’ EVs and charging stations.
  • Support for fleet operations allows for centralized control over multiple vehicles’ charging sessions and roaming across different charging networks.
  • Scalability and extensibility enables future updates and new features, including new types of vehicles, charging methods and energy services.

 

EV Charging Connectors

Now that the communication interface is being addressed, what about the connector? The two need to have compatibility to achieve the full capabilities.

There are multiple standards that define the connector requirements for EV charging, as each manufacturing region has its own connector standards. Those standards enable the implementation of the features described in ISO 15118-20.

ISO 15118-20 communication protocols between the charger and the EV BMS regulate the charging process. Communication ensures safe and efficient charging by monitoring the battery’s state-of-charge (SoC), temperature and other parameters.

User and EV safety features include overcurrent protection, insulation monitoring and ground fault protection.

 

AC Charging Stations

In the mid-2000s, the Society of Automotive Engineers (SAE) developed a specific connector for AC EVSEs. The SAE J1772 standard defines a type 1 connector with five connections.

The J1772 type 1 connector for single-phase AC charging can support charging power up to 19.2 kW, delivering 240 V @ 80 A. The average charge rate in a Level 2 charging station can be as much as 25-30 miles of range/hour. This connector is primarily used in North America and Japan.

Some basic J1772 Level 2 chargers have limited ISO 15118 integration in commercial applications, though that is rare.

 

DC Fast Charging

The primary push in the retail charging and in many commercial use scenarios is Level 3 chargers that use DC fast charging technology. This is where ISO 15118 integration comes to the forefront.

DC fast charging enables high power delivery, which significantly reduces the time needed to charge an EV battery. Factors affecting charge time include the power rating of the charging station, the charging rate that the vehicle’s battery management system (BMS) will allow and the battery capacity. Typically, DC fast charging stations can charge an EV to 80% of full charge in 20 to 40 minutes.

 

The NACS Connector

Due to its market leadership, Tesla developed its own connector for EVs and EVSEs in the North American market. The SAE is standardizing the connector under SAE J3400. The connector is called the North American Charging System (NACS). This is currently becoming highly competitive with CCS.

Since Tesla charging stations are considered the most reliable and are the most prevalent in the North American market, most commercial EV charging station manufacturers have adopted the Tesla NACS connector. The NACS connector is smaller than the CCS Type 1 connector and can support AC charging at up to 80 A and 277 V. With DC fast charging, the connector can support up to 1000 V and greater than 650 A.

 

Caitie Romano is the marketing and communications manager for BTC Power, a manufacturer of electric vehicle charging systems in North America.