Overview of North American Charging Standards for New Energy Vehicles

Let's take a look at the following:

Released in 1996, SAE J1772 utilizes a five-pin connector, supports 120V/240V AC charging, and has a maximum power of approximately 19kW. CCS1 builds on J1772 by adding a two-pin DC connector, creating a split upper and lower design. The DC side supports a maximum of 1000V/400A, with a power limit of approximately 350kW. Early models from automakers like General Motors and Ford 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: This defines the physical connection interface between electric vehicles and charging stations in North America, known as "Type 1" or "J plug," and serves as the foundation for the subsequent CCS1 (Combo) DC fast charger female connector.
Two power levels: The standard divides AC charging into Level 1 and Level 2. Level 1 uses 120V single-phase mains power, with a current of 12–16A and a power of 1.4–1.9kW, suitable for slow charging at home overnight. Level 2 uses 240V single-phase power, with a maximum current of 80A and a power of up to 19.2kW, suitable for residential or public use.
Five pins: The interface has five pins: L1 (live), N (neutral), PE (protective earth), CP (control pin), and PP (proximity pin). CP and PP together facilitate PWM communication and plug detection between the vehicle and charging station, ensuring that power is only supplied when a secure connection and parameter negotiation are complete.

Full Handshake: Before charging, the 1 kHz PWM signal duty cycle on the CP line represents the maximum current the charging pile can provide. The charging pile switches to "State C" to officially output power only after the vehicle detects the duty cycle and closes internal relay S2. If the signal is lost or the state is abnormal, the system immediately powers off.

Multiple protections: The standard stipulates safety mechanisms such as overcurrent, overtemperature, leakage, insulation monitoring, and anti-incorrect plugging and unplugging. The connector body has dual insurance of mechanical lock and micro switch to prevent live extraction and accidental disconnection.

Through these five elements, SAE J1772 provides a unified, secure, and scalable AC charging framework for North American electric vehicles. It also forms the foundation for the subsequent DC fast-charging combo interface, CCS1 (Combined Charging System 1). Because CCS1 expands upon the SAE J1772 AC interface standard and develops a DC fast-charging specification, it is often referred to as "SAE J1772 Combo."

The core elements of the CCS1 can be summarized as one interface, two charging methods, a seven-pin structure, and unified communications. First, based on the SAE J1772 five-pin AC design, two high-current DC pins (DC+ and DC-) are added side by side below, forming a seven-pin integrated plug, hence the name Combo 1. When used alone, the top half functions as a J1772 AC slow charger with a maximum power of approximately 7.4kW. When the DC charger is fully inserted, the bottom two pins handle DC fast charging with a maximum power of 350kW, 1000V/500A.

Secondly, the communication and control layers uniformly rely on the CP (Control Pilot) pin: PWM signals are used to complete basic handshakes in the AC stage, and power line carriers (PLC) are superimposed on the same pair of CP-PE lines in the DC stage to implement ISO 151118 advanced communication, completing the entire process management including charging parameter negotiation, insulation detection, and fault monitoring.

Regarding safety and compatibility, the PE connector provides grounding protection, while the PP connector uses resistance coding to confirm the torch tip connection status and the cable current limit. A mechanical lock and microswitch prevent the torch from being pulled while powered, ensuring human and machine safety. In summary, the CCS1 uses a "combo connector" to cover both AC slow charging and DC fast charging, utilizing a J1772 female connector, a seven-pin structure, and CP-PLC as a unified communication method. This allows for a fast-charging ecosystem in North America with speeds up to 350 kW.

NACS was originally Tesla's proprietary interface. In 2022, Tesla opened it up and renamed it NACS, which was then adopted by the SAE as the recommended standard, SAE J3400, in 2024. NACS features an integrated, ultra-thin design, sharing a small interface for AC and DC charging. While half the size of CCS, it supports DC fast charging at speeds up to 1000kW.

The core content of SAE J3400 can be summarized into five points:

Integrated interface: The same compact plug integrates two sets of AC and DC contacts, eliminating the need for "splitting" the upper and lower parts like the CCS1. The overall size is about half that of the CCS1 and the weight is lighter.

Power rating: Up to 80A/500V (≈19 kW) in AC mode, with 500A/1000V (≈500kW) already in mass production in DC mode. Specifications allow for upgrades up to 1MW.
Pin and communication: A five-core layout is used for DC positive and negative poles, AC live/neutral, ground, control pilot (CP), and proximity pilot (PP). The communication protocol follows ISO 15118/DIN 70121, making it compatible with existing CCS control logic and enabling direct reuse of vehicle-side electronic control units.

Safety and Certification: Complies with North American mandatory safety and quality systems such as UL 2251, SAE J3400, and IATF 16949. The interface features temperature sensing, mechanical locking, anti-electric shock protection (IP2XB), and IP67 protection.

Market and Ecosystem: After Tesla opened up, more than ten North American automakers, including Ford, General Motors, Rivian, Volvo, and Mercedes-Benz, announced that they would natively adopt NACS starting in 2024-2025. At the same time, third-party charging pile companies also launched UL/SAE-certified NACS charging guns and modules, and North American public networks began to simultaneously deploy NACS and CCS dual-gun or adapter solutions.

Summary
Through the above understanding of these two standards, we can see that SAE J1772 and SAE J3400 share an inherent logical relationship of inheritance and development. SAE J3400 is a comprehensive upgrade and expansion of SAE J1772. SAE J3400 supports not only AC charging but also DC fast charging, with a maximum specified current of 900A. If charging is performed simultaneously using both the on-board charging port and the connector, the maximum current can reach 1000A. Furthermore, it incorporates V2G technology and meets backup power requirements, significantly expanding its functionality compared to SAE J1772. The SAE J3400 standard supports digital communication between the vehicle and the charging device, enabling more efficient information exchange and troubleshooting. For example, it incorporates the minimum error codes used by the ChargeX Alliance for DC fast charging, enhancing the intelligence and reliability of the charging system. Therefore, the current North American market is in a stage where CCS1 and NACS coexist: CCS1 is still used by some models on sale, while NACS is rapidly replacing CCS1 and becoming the mainstream in the future with its higher power, smaller size and wider supercharging network.