NACS / Tesla Connector (SAE J3400). Pinout, Wiring, Protocol & Complete Specs

The North American Charging Standard (NACS) is the most unlikely standards success story in the EV industry. Tesla invented it, kept it proprietary for a decade, then in November 2022 published the specification and offered it royalty-free. By 2026 it had become the default DC charging connector for new EVs sold in North America. displacing CCS1 faster than any industry observer expected.

The connector is now officially SAE J3400, standardized in 2023, but everyone still calls it NACS or "the Tesla connector." It ships on every new Cybertruck, Model Y, and Rivian R1T; Ford, GM, Honda, Nissan, Toyota, Hyundai, and virtually every other major automaker committed to it; and the entire Tesla Supercharger network (~50,000 connectors in North America alone) upgraded to support it.

Why did the industry consolidate around a connector designed by an automaker rather than the traditional CCS path? Three reasons: it's physically smaller and handles both AC and DC, it's backed by the largest fast-charging network in the world, and Tesla's royalty-free release removed the political obstacle to adoption.

Physical design

NACS is dramatically smaller than CCS1. The connector body is roughly 27 mm wide × 33 mm tall: compared to the 100 mm+ width of a CCS1 assembly. It fits in one hand like a USB-C plug, not like a brick.

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The two large pins (DC+/AC L1 and DC–/AC L2) are shared. the same contacts handle both AC and DC current. This dual-use design is what makes NACS's small form factor possible; it doesn't need the separate AC pin set that CCS adds below the Type 1 base.

The connector features:

• A latch mechanism on top that locks with a single finger trigger release
• Weatherproofing rated to IP55 (mated)
• A cable retention design that hangs off the side of the charge port rather than sticking straight out. better cable droop management
• Haptic confirmation on the latch on some charger handles

Pin assignments

What "shared pins" actually means

The DC+ and DC– pins are electrically the same whether you're doing AC or DC charging. For AC:

• DC+/AC L1 carries 120V or 240V L1 hot
• DC–/AC L2 carries the L2 hot leg (240V) or neutral (120V)

For DC:

• DC+ is the positive rail of the DC bus (up to 1000V relative to DC–)
• DC– is the negative rail

The EVSE (charger) detects the session type via the CP signal and switches its internal power module accordingly. The vehicle's onboard charger (AC) or the offboard DC charger handles the power conversion.

Control Pilot (CP). dual-mode signaling

The single most elegant engineering decision in NACS is using one signal pin (CP) for both AC and DC sessions. How does it switch?

AC mode: PWM

During an AC session, CP operates exactly like J1772 / IEC 61851-1:

• 12V constant = charger ready, not yet connected
• 1kHz PWM, ±12V = charger energized, communicating current limit via duty cycle
• Duty cycle table (same as J1772):

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This means any J1772 Level 1 or Level 2 station can charge a NACS vehicle using a simple passive physical adapter. no protocol conversion needed. The CP wire carries the same J1772 PWM signal regardless of which type of plug body is on the cable end.

DC mode: PLC (HomePlug GreenPHY)

For DC fast charging, the CP wire switches to Power Line Communication. exactly like CCS. The HPGP modem modulates a 4–28 MHz carrier onto the CP line. The protocol stack is ISO 15118-2 (current) evolving to ISO 15118-20.

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Because NACS DC uses the same PLC stack as CCS, the two standards are protocol-compatible at the software layer. The only difference is the physical plug. This is why CCS1-to-NACS adapters work: they're purely a mechanical + pin-mapping conversion with no protocol translation.

DC charging sequence (ISO 15118-2)

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Power levels

AC charging (on-board charger limited)

Tesla Model 3/Y ships with a 9.6 kW (40A) onboard charger; Model S/X with up to 11.5 kW. Cybertruck has dual onboard chargers (up to 19.2 kW AC). The vehicle's OBC is the limiting factor for AC speed. not the NACS connector.

DC fast charging (Supercharger and third-party)

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The SAE J3400 spec allows up to 900 kW (1000V × 900A). well beyond any deployed hardware. In practice, the best publicly available charging speed in 2025 is 500 kW on Supercharger V4. Reaching 900 kW would require liquid-cooled cables (no standard exists yet) and batteries that can accept that rate.

Wiring specifications

DC power cable

The NACS connector uses the same conductor sizing principles as CCS:

Tesla Supercharger V3 and V4 use liquid-cooled cables: a coolant loop runs inside the cable jacket, chilling the conductors to allow higher current through narrower copper. This is why the V3/V4 cable is surprisingly thin and flexible despite its power rating.

Signal wiring

PP (Proximity Pilot) resistor encoding

The PP pin reads a resistor to ground in the plug handle. The vehicle uses this to limit AC charging current below the EVSE maximum if the cable is undersized:

Electrical characteristics

Compatibility matrix

NACS vehicle + NACS charger

Works natively. No adapter needed.

NACS vehicle + CCS1 charger

Requires a CCS1-to-NACS adapter (also called "NACS Adapter" or "CCS Magic Dock adapter"). Tesla sells these. The adapter is passive. just pin remapping and a mechanical body. Protocol is identical (ISO 15118 PLC on CP). Works reliably.

CCS1 vehicle + NACS charger

Requires a NACS-to-CCS1 adapter. Tesla deployed "Magic Dock" at many Superchargers. a CCS1 adapter permanently installed on the Supercharger cable, allowing CCS1 vehicles to use the Supercharger network.

NACS vehicle + Level 2 J1772 charger

Requires a passive J1772-to-NACS adapter. These are widely available (~$30). Since AC mode uses the same PWM control pilot protocol as J1772, the adapter is truly passive. no electronics, just a pin adapter.

NACS vehicle + CHAdeMO charger

No viable adapter. CHAdeMO is CAN bus; NACS is PLC. Protocol translation would require active electronics. Not practical.

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Safety features

NACS inherits all of the ISO 15118 safety stack that CCS uses, plus a few additional Tesla-developed features:

1. PP plug detection: the vehicle's charge port detects the plug before any CP signaling begins. No CP commands are processed without PP present.

2. CP hardware pilot state machine: identical to J1772 states (A through F). Power only flows in state C (diode check) or D (ventilation required). Falls back to safe state on CP open or short.

3. Insulation monitoring: same pre-charge insulation test as CCS. Charger applies low voltage, verifies >100 Ω/V insulation before contactor close.

4. Contactor welding detection: monitors DC bus voltage after shutdown. Flags fault if voltage doesn't decay as expected.

5. Ground fault detection: monitors PE continuity. If chassis ground is lost, charging stops.

6. Inlet temperature monitoring: most Tesla charge ports have thermistors at the inlet. If the pins overheat (contact resistance degradation, partial connection), charging rate is reduced or stopped.

7. Gun retention: the latch mechanism physically prevents unplug while HV is present on the DC bus. Contactors open first, bus voltage decays, then latch releases.

NACS vs CCS1. direct comparison

The standardization story

2012: Tesla ships the first Roadster upgrades and then Model S with a proprietary connector. It's smaller and better than J1772 but closed.

2012–2022: Tesla builds the Supercharger network exclusively for Tesla vehicles. CCS1 becomes the "open" standard for everyone else. Industry has two incompatible DC standards in North America.

November 2022: Tesla publishes the NACS specification and makes it royalty-free. Shock announcement.

May 2023: Ford announces NACS adoption for all future EVs starting 2025.

June 2023: GM follows Ford. Then Rivian, Volvo, Polestar, Nissan, Honda, Acura, Toyota, Mazda, Subaru, Jaguar, Hyundai, Kia, and effectively every major automaker.

July 2023: SAE International begins the J3400 standardization process.

October 2023: SAE J3400 published. NACS is now an open industry standard.

2024: Tesla opens Supercharger network to non-Tesla vehicles with NACS. Magic Dock CCS1 adapters deployed at many stations. Ford, GM, Rivian vehicles start shipping with NACS ports.

2025: NACS is the default new-vehicle port for most North American EV sales. CCS1 becomes the adapter-based option for older vehicles and some fleet purchases.

The speed of this transition. from proprietary Tesla feature to dominant North American standard in under 3 years. is unprecedented in the EV industry. The combination of Supercharger network dominance and a technically superior connector made the outcome nearly inevitable once Tesla opened the specification.

Installation notes

NACS chargers (EVSE) are now widely available from:

• Tesla (Supercharger V3/V4, Wall Connector)
• Third-party DCFC manufacturers (ChargePoint, EVgo, Electrify America, Blink)
• Level 2 EVSE makers (JuiceBox, Wallbox, ChargePoint Home, Grizzl-E)

For commercial Level 2 NACS installations:

• Minimum 240V / 40A circuit for 9.6 kW charge rate
• 240V / 80A circuit for full 19.2 kW (premium installs, fleet)
• NACS inlet on newer vehicles; J1772 adapter handles legacy sites

For DC fast charging (new deployments in North America):

• NACS-native is now the standard for new installations
• Dual-standard (NACS + CCS1 Magic Dock) for legacy compatibility
• V4 Supercharger specs: 480V three-phase input, up to 615A per cabinet, 500 kW per stall

The shift is settled. NACS is what you specify for North American DCFC installations in 2025 and beyond.