Cerbo GX

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Refit 2024

The Victron Cerbo GX is the brains behind the Victron Ecosystem. It is actually a customized Raspberry PI running the Victron Venus OS.

The Cerbo GX is designed to also monitor/ manage up to 4 tanks (Fresh, Grey and /or Black), monitor up to 4 digital inputs (relay based triggers), up to 4 hardwired temperature sensors (LM335 temperature Sensor), USB based inputs (GPS, Bluetooth Temp Sensors) as well as managing the Victron ecosystem.

There is a tremendous amount of functionality built into this device and SV Unladen Swallow is using quite a bit of it. The diagram below shows how it is currently configured.

Cerbo GX Buses/ Protocols

VE.Direct is a point-to-point unbalanced serial connection where as VE.Can (aka CANbus) is a balanced (RS-485) multi-drop connection. I think VE.Direct came first in the Victron world.

VE-Direct requires a connection on Cerbo, etc. for every device and at most there are 3 ports. You can extend this by using a VE.Direct to USB adapter cable.

VE.Can is physically different from CANbus. VE.Can uses ethernet cabling, looping through each device. CANbus uses a unique connector with “taps” to go to each device. You can interconnect VE.Can to CANbus with the appropriate adapter. The entire network is terminated at both ends with a 120 ohm resistor. VE.Can/CANbus is limited to about 100 devices. VE.Can/CANbus operates at one of several baud rates and in the Victron world, this rate must be the same for all devices on the same port. Additional VE.Can ports can be added to Cerbo via a USB to CANbus adapter.

As best as I can tell – lots of opinions out there, but the bottom line appears to be the BMS.Can ports are intended to hook 3rd party BMS’s into the Victron environment. There are some mentions about Galvanic Isolation and specific protocols but it get pretty cryptic. Since my environment is all Victron devices, these ports appear to be superfluous.

VE.CAN Ports

Lynx BMS

The Lynx BMS connects to the Cerbo GX via the VE.Can bus

NMEA 2000 Interface

This is a special dongle connected to the 2nd VE.Can bus port.

This allows the Victron ecosystem data to be visible on the Garmin MFDs and also consume data generated from elsewhere in the N2K ecosystem (e.g. GPS)

VE.Bus Ports

Quattro (Inverter/ Charger)

This connects via the VE.Bus. It also connects to the external Digital Remote Console on the same bus. The bus must be terminated at each end (????)


not used

USB Interfaces

The Cerbo GX is configured with 3 USB ports – note Port 3 is power only and is intended to power the remote display.

Since we are using more than 2 USB devices, each port hosts a powered USB Hub

  • USB 1 – Hub 1 (This will be a powered hub – 5 VDC via a buck converter)
    • MMPT 1
    • MMPT 2
  • USB 2 – Hub 2 (This will be a powered hub – 5VDC via a buck converter)
    • External Bluetooth adapter
    • GPS Receiver
    • External Relay Bank
  • USB 3 – Power Only
    • Power the external Display


This is the display output for the external Display

MicroSD Card

The Cerbo GX has some internal storage, but if the VRM connection is lost for more than a day or so, data is lost. A 128 GB microSD card holds several years worth of data and provides a backup to the cloud based VRM data.

Tank (1-4), Temperature (1-4), Digital Input (1-4)

The boat’s fresh water and fuel tank levels are integrated via the ActiSense analog to N2K converter. We may use one of these inputs to home the Black Water tank level at a future date.

The Temperature inputs use the LM335 temperature Sensor standard. This is a European standard and the US based standard is incompatible with it. The Ruuvi Bluetooth sensors provide a very capable alternative so the hardwired ports are not used.

The 4 digital inputs are generally intended to collect state data (on/off) from other systems to drive error conditions. At this point, this is the 3rd input alternative for this type of data. Given other alternatives, we likely won’t use these ports.

Relay 1

We are going to wire COM to ground and then use NO as the output to signal a general error condition (alarm) for the Cerbo GX to the master alarm panel

Relay 2

We are going to wire COM to ground and then use the NO as the output to signal a temperature alarm to the master alarm panel. Configuring this relay for temperature is a software setting. The Ruuvi Temp Sensors in the Refrigerator, Freezer and the Engels will feed this logic.

12 VDC

The Cerbo GX is going to take it’s power feed from the Lynx BMS AUX power port (+/ -)

WiFi and Bluetooth and RJ45 Ethernet

The Cerbo GX is configured to operate on the “Unladen Swallow” TCP/IP network on the boat. The “Unladen Swallow” network is hosted on an internal Router which hosts a VPN client so all “Unladen Swallow” network traffic flows through the VPN tunnel generally back to a USA based proxy.

Since the internal Bluetooth transceiver is known to be lower power, best practices are to add a USB based higher power Bluetooth transceiver. This makes working with the Victron Connect app on while onboard more reliable. It also enables better communication via bluetooth with other non-hardwired victron devices.

The RJ45 LAN port is not used at this time. The Cerbo GX cannot act as a router and will default to the RJ45 if connected. Normally this port would provide a direct connection to the GarminNet to support the Victron App on the Garmin MFDs. However, if this connection is used, the Cerbo GX cannot easily connect to the broader internet which is being accessed via the Cerbo Gx’s WiFi port. (There are people who have used static IP addressing and routing to make this work, but it’s a significant amount of work). Since the VRM connection is a priority and the Victron based digital data is made available to the N2K ecosystem which is available to the Garmin MFDs, this connection to GarminNet is not as useful.

Victron Remote Management (VRM)

The Cerbo GX will push data to Vitron’s data management and storage cloud solution called VRM via the WiFi connection through SV Unladen Swallow’s Starlink Internet. This will allow remote management and monitoring of the energy environment as well as other data points.

Signal K Server

This is the other part of the remote data aspect of the Cerbo GX server. Since the Cerbo has access to the N2K data feed, it can host a remote N2K feed to support Open CPN or other external data feeds.

Our big plans here are to make all of the data available to our Garmin MFDs available to remote devices (not on the boat) using something like Open CPN. This will allow us to share in “near real time” our chart plotter based information while we are underway. This will allow others to see what the boat is doing as we travel.

Node Red

This is the other component that is available with some reconfiguration of the Cerbo GX and loading the Large OS version of the Venus OS. The Node Red environment looks like it is a highly customizable programming and control environment that will allow us to interact with any parameter available in the N2K/ Victron/ Garmin ecosystem. It will then allow us to control external devices via USB based Relays. I have ordered a external non-Vitron device that contains 8 additional relays.

Some examples are found here

So the first project is:

Hot water with Excess Solar Power

This will hopefully allow us to do things like turn on the water heater when we have excess solar power. The basic idea is to trigger on battery State of charge combined with time of day. If the SOC is greater than say 98% and we are after 12 noon and before 5pm, then let’s use the excess solar capacity (the batteries are full) to power the electric hot water heater.

I will publish detailed instructions on how this works once it’s working.

Some additional software packages to extend our Cerbo GX Function:

GuiMods –

GUI MODS, or Graphic User Interface Modifications, are third-party software that allows users to customize the display of their Cerbo GX or other Venus GX device. GUI MODS can be used for:

  • Customizing the home screen
  • Tying up information in the display
  • Making additional SmartShunts appear on the front page of the display
  • Getting AC voltage information

Some advantages of GUI MODS include: More intuitive operation and Easy interaction. 

Some disadvantages of GUI MODS include: A more crowded screen. 

GUI MODS provides even more details in one screen, such as voltage, frequency, and amperage at both the source side (Shore) and the inverter output side. The enhanced Hub overview includes voltage, current, frequency, and input current limit values. 

You can also check out this video: