Overview of North America’s New Energy Vehicle Charging Standards

1. SAE J1772 and CCS1

SAE J1772 was released in 1996, adopting a 5-pin connector supporting 120V/240V AC charging with a maximum power of about 19 kW. CCS1 adds two DC terminals to the J1772 design, forming a vertically split structure. The DC side supports up to 1000 V/400A, with a power limit of around 350 kW. Many early models from General Motors, Ford, and other automakers adopted this standard.

The core elements of the SAE J1772 standard can be summarized as "one interface, two power levels, five pins, full handshake, and multiple protections."

• One interface:
  Defines the physical connector interface between electric vehicles and chargers in North America, called "Type 1” or "J plug.” It also forms the basis of the CCS1 (Combo) DC fast-charging inlet.
  
  
• Two power levels:
  AC charging is divided into Level 1 and Level 2.
  – Level 1 uses 120V single-phase household electricity at 12–16A, delivering 1.4–1.9 kW, ideal for overnight home charging.
  – Level 2 uses 240V single-phase electricity, up to 80A, with a maximum power of 19.2 kW for residential or public charging.
  
  
• Five pins:
  The connector includes five pins — L1 (line), N (neutral), PE (protective earth), CP (control pilot), and PP (proximity pilot). CP and PP enable PWM communication and connector detection, ensuring power is delivered only after secure connection and parameter negotiation.
  
  
• Full handshake:
  Before charging, the CP line sends a 1 kHz PWM signal whose duty cycle indicates the charger’s maximum available current. The vehicle detects the duty cycle and closes internal relay S2, after which the charger switches to "State C” to deliver power. If the signal is lost or abnormal, the system disconnects immediately.
  
  
• Multiple protections:
  The standard includes overcurrent, overtemperature, leakage, insulation monitoring, and anti-misconnection protections. Mechanical locking and microswitches prevent live unplugging and accidental disconnects.

Through these five elements, SAE J1772 provides a unified, safe, and scalable AC charging framework for North American EVs and serves as the foundation of the later DC fast-charging Combo interface — CCS1. Because CCS1 is an extension of the SAE J1772 AC interface for DC fast charging, it is often called "SAE J1772 Combo."

CCS1

The core aspects of CCS1 can be summarized as one interface, two charging modes, a 7-pin structure, and unified communication.

Based on the 5-pin J1772 AC design, two high-current DC pins (DC+ and DC–) are added below, forming a 7-pin Combo 1 connector. When only the upper section is used, it functions as a J1772 AC connector with a maximum of about 7.4 kW. With the full connector, the lower two pins provide DC fast charging up to 350 kW at 1000 V/500 A.

Communication and control rely on the CP (Control Pilot) pin:
– AC charging uses PWM for the basic handshake.
– DC charging uses PLC (Power Line Communication) over the same CP-PE lines to implement ISO 15118 advanced communication, performing parameter negotiation, insulation checks, fault monitoring, and more.

PE provides grounding protection, PP uses resistor coding to detect connection status and cable current limits, and mechanical locks plus microswitches prevent live unplugging, ensuring safety.

In summary, CCS1 uses one Combo interface to support both AC and DC charging. With the J1772 inlet as its base, a 7-pin structure, and CP-PLC unified communication, it forms a fast-charging ecosystem of up to 350 kW in North America.

2. NACS / SAE J3400

NACS was originally Tesla's proprietary connector. In 2022, Tesla opened the standard and named it NACS, and in 2024 it was adopted by SAE as recommended standard SAE J3400. NACS uses an ultra-slim, integrated design, combining AC and DC into a single compact connector — about half the size of CCS — while supporting up to 1000 kW DC fast charging.

The core elements of SAE J3400 can be summarized in five points:

• Integrated interface:
  AC and DC contacts are integrated into one small connector, unlike the stacked design of CCS1. The overall size is about half that of CCS1 and is significantly lighter.
  
  
• Power capability:
  In AC mode, up to 80A / 500V (~19 kW).
  In DC mode, mass-produced hardware supports 500A / 1000V (~500 kW), with the standard reserving room for upgrades to 1 MW.
  
  
• Pins and communication:
  DC positive/negative, AC line/neutral, ground, control pilot (CP), and proximity pilot (PP) share a 5-conductor layout. Communication follows ISO 15118 / DIN 70121 and is compatible with CCS control logic, allowing reuse of existing vehicle ECUs.
  
  
• Safety and certification:
  Meets UL 2251, SAE J3400, IATF 16949, and other North American safety and quality requirements. The connector incorporates temperature sensing, mechanical locking, anti-shock protection (IP2XB), and IP67 sealing.
  
  
• Market and ecosystem:
  Since being opened by Tesla, automakers such as Ford, GM, Rivian, Volvo, and Mercedes have announced native NACS adoption starting from 2024–2025. Third-party charger manufacturers have also introduced UL/SAE-certified NACS connectors and modules, and public charging networks are deploying NACS+CCS dual-connector or adapter solutions.

3. Summary

From the comparison above, we can see that SAE J1772 and SAE J3400 share a logical progression of inheritance and development. SAE J3400 builds upon and expands J1772, supporting both AC charging and high-power DC fast charging. Its maximum regulated current reaches 900A, and when using both the vehicle-side and connector-side conduction paths simultaneously, it can reach up to 1000A. It also introduces V2G technology and meets backup power requirements, greatly expanding functionality compared with SAE J1772.

SAE J3400 supports digital communication between vehicles and charging equipment, enabling more efficient information exchange and fault handling. It incorporates minimum error-code requirements used by the ChargeX Alliance in DC fast charging, enhancing the intelligence and reliability of the charging system.

Therefore, the North American market is currently in a stage where CCS1 and NACS coexist: CCS1 remains in use for some models still on sale, while NACS — with higher power capability, smaller size, and access to Tesla's extensive Supercharger network — is rapidly becoming the future mainstream.