AC Junction Box and Outlets

Last updated: October 10, 2024

Overview

Cybertruck is not only able to charge on Alternating Current (AC) but is able to supply AC voltage through the charge port and various power outlets built into the vehicle. Power is supplied from the High Voltage (HV) battery to electric appliances using 120V or 240V 60Hz AC, which is generated using a bidirectional Power Conversion System 2 (PCS2). This operating state of the PCS is also referred to as grid forming. Appliances are connected to Cybertruck using outlets inside the cabin or the bed or through the charge port using a new bidirectional Gen 2 Universal Mobile Connector (UMC) with a new UMC pigtail adapter that connects like an outlet to the UMC.

In order to route AC power from the charge port to the PCS during charging and from the PCS to the outlets or charge port when supplying AC power to appliances, the AC terminals of the PCS are connected to a new device called AC Junction Box (ACJB). The AC Junction Box contains a set of relays, voltage sensors, current sensors, and ensures that power is routed the correct way between the charge port, PCS, cabin outlets, and bed outlets.

Ancillary Bay with AC Junction Box In Top Left Corner

AC Junction Box, Harnesses Connected

AC Junction Box, Harnesses Disconnected

While the AC Junction Box contains a microprocessor, it is not connected to Controller Area Network (CAN) and does not represent its own electronic control unit (ECU). Instead, it is connected to the High Voltage Controller (HVC), which sends commands to the AC Junction Box and provides it with low voltage (LV) power.

For electrical safety, the AC Junction Box further contains a Ground Fault Circuit Interrupter (GFCI) that senses whether any differential current occurs on the lines supplying the outlets. If the differential current exceeds a certain threshold, it indicates that the current is leaking through an unsafe path. In response, the PCS will disable its AC grid forming.

Specifications

Electrical diagram

Electrical Diagram

Electrical specifications

• Maximum AC charge current: 48A
• Maximum AC current cabin outlets: 20A combined
• Maximum AC current bed outlets:
  • NEMA 5-20: 20A combined
  • NEMA 14-50: 40A
• Output voltage:
  • Cabin outlets: 120V 60Hz AC
  • Bed outlets:
  • NEMA 5-20: 120V 60Hz AC
  • NEMA 14-50:
    • Line to line: 240V 60Hz AC
    • Line to neutral: 120V 60Hz AC

Operation

System states

AC power can be routed in the following ways:

Charging:

• Charge port to PCS

Note

All outlets are disabled whenever AC charging.

Vehicle to load:

• PCS to cabin outlets
• PCS to cabin outlets and bed outlets
• PCS to cabin outlets and bed outlets and charge port
• PCS to cabin outlets and charge port

Outlets

Cybertruck features 5 outlets to supply AC power to electric appliances.

Cabin outlets

There are 2 NEMA 5-20 outlets inside the cabin. One is located in the front center console. The other is located at the rear of the center console, underneath the second row display. Both outlets combined can supply up to 20A continuous at 120V 60Hz.

Front Cabin Outlet Inside Center Console

Rear Cabin Outlet At Rear End Of Center Console

Bed outlets

There are 3 outlets in the Cybertruck bed. The outlets are located on the left-hand side behind a little flap close to the tailgate. There are 2 NEMA 5-20 outlets and 1 NEMA 14-50 outlet. The NEMA 5-20 outlets can supply combined up to 20A continuous at 120V 60Hz. The NEMA 14-50 can supply up to 40A continuous at 120V/240V 60Hz.

1. NEMA 5-20 outlets 2. NEMA 14-50 outlet
Bed Outlets and Outlet Door

Overcurrent detection and response

Overcurrent detection is implemented in order to protect conductors from thermal damage. PCS features built-in overcurrent detection meaning AC grid forming will be disabled if current above 40A is detected.

Because the conductors to the NEMA 5-20 outlets are sized for 20A, AC Junction Box features additional current sensors on the related circuits. If one of these sensors senses overcurrent on the corresponding conductors, the PCS will also disable AC grid forming.

After AC grid forming has been disabled, PCS will retry three times to restore grid forming. If all retries are expired, the user will have to reset the outlets using the reset button on the vehicle UI.

Cabin Outlets HV Harness

Bed Outlets And Harnesses

Serviceability

These are the only parts that can be replaced:

• AC Junction Box
• Bed outlets
• Bed outlets door
• Cabin outlets

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