What the Cerbo GX actually is
The Cerbo GX is the brain of a Victron setup. By itself it does nothing useful: no inverter, no charger, no monitoring. Connect it to the rest of the system and it becomes the dashboard, the controller, and the gateway between everything else.
It pulls data from the Multipluses, the shunt, the MPPTs, and any compatible BMS. It exposes that data on a local display, a phone app, or remotely through Victron's VRM portal. It can also schedule things: switch a relay when a tank level drops, fire up a generator when the battery hits a threshold, kick on a heat pump when the battery is full.
Robbert's view: it's mandatory for any Victron-based home battery that has more than one inverter or a non-Victron BMS. Without it the units don't talk to each other.
The hardware tour
| Connection | Purpose |
|---|---|
| Power input | 8 to 70 V DC. No adapter required. Wires straight to the busbar or Lynx Distributor. |
| Tank sensors (1x 8-pin) | 4 sensor pairs. Water level, fuel level, etc. Can trigger a pump. |
| Temperature sensors (1x 8-pin) | 4 sensor pairs. Extra temperature monitoring beyond what the Multiplus and shunt provide. Can drive fans or heat pumps based on configured thresholds. |
| Digital inputs (1x 8-pin) | On/off sensors, max 5 V. Door alarm, smoke detector, fire alarm. |
| 2x relays | Switch external devices. Fans, heaters, generator start. Configured in software. |
| Ethernet | One standard internet port for remote access via VRM. |
| VE.Bus (2x) | Daisy-chains to the Multipluses (each Multiplus has an in and an out). |
| VE.Can (2x) | Connects to the shunt and the MPPTs. A blue terminator goes on the last open port at each end of the network. |
| BMS-CAN (2x) | For non-Victron batteries. Standard UTP cable works fine; Victron's blue cables are optional. |
| VE.Direct (3x) | For smaller Victron devices (shunt, smaller MPPTs). |
| HDMI | Drives an external display. |
| USB (power-only) | Pairs with the display via a combined HDMI+USB cable. |
| USB (data, 2x) | General purpose. Add a hub for more. |
The 7 RJ45 ports all look identical, but only one of them is actual Ethernet. The rest carry VE.Bus, VE.Can, or BMS-CAN traffic, and getting them mixed up doesn't damage anything but nothing will work.
First-time pairing
The Cerbo ships with WiFi access point and Bluetooth on. If they aren't, a small button on the bottom enables them. Workflow:
- Power the Cerbo from any 8 to 70 V DC source. The status LEDs on the top light up.
- Open Victron Connect on a phone. The Cerbo appears in the device list. The pairing password is on a sticker on the side of the unit.
- Pair, then connect the phone to the Cerbo's WiFi access point (SSID and password also on the side sticker).
- From the Cerbo's web interface, scroll to WiFi settings and join the home network.
- Check the firmware tab. If updates are available, run them.
Once on the home network, the Cerbo is reachable from a phone or a browser anywhere. No port forwarding required: Victron's VRM portal handles the remote-access path.
Wiring it into a Victron busbar setup
The Cerbo doesn't pull much current, so the input cable doesn't need to be heavy. Robbert's recommendation against bolting it onto a fuse terminal is about resistance: adding another lug onto a fuse stud means another contact surface and another potential heat source.
Instead, he wires the Cerbo to the small mounting screws on the busbar frame itself, the ones that hold the Lynx Power In busbars in place. That gives the Cerbo a clean 48 V feed from the busbar without an extra lug on a high-current connection. The small lugs needed for this are cut from the supplied cable and re-crimped to fit the smaller screws.
Cable management matters here too. The Cerbo ships with much more cable than most installations need. Trim it to the actual distance from the busbar to the Cerbo's mounting position; coiled excess cable in a trunking run takes space that the Multiplus DC cables will need later.
Connecting to the Multipluses
Each Multiplus has two VE.Bus ports: in and out. Daisy-chain them with standard UTP cables:
- From the Cerbo, run a UTP cable into the first Multiplus's VE.Bus port.
- From that Multiplus's second VE.Bus port, run to the next Multiplus.
- Continue through every Multiplus on the chain.
No terminator is required on the VE.Bus chain. The blue terminator only applies to VE.Can networks (the shunt, the MPPTs).
A standard UTP cable from a PC store works for VE.Bus. The Victron blue cables are pre-tested but functionally identical.
Saving the connector caps
The Cerbo comes with a bag of small connectors for the tank, temperature, digital input, and relay ports. If you don't need them yet, leave them plugged into their respective ports anyway. They're easy to lose and you may want them six months from now when a sensor gets added.
What Robbert flagged for the next step
The cable trunking he chose (60x40 mm) is already filling up before the heavy DC cables go in. Each of the three Multipluses needs a 70 mm² positive and a 70 mm² negative back to the busbar. Six fat cables, on top of the existing AC and signal wiring, won't fit. He's anticipating a swap to a larger trunking size before the next step. That detail matters at the planning stage: trunking sizing is one of those parts of a build that's easier to oversize the first time than to redo later.
Takeaways
- The Cerbo GX is the data and control layer. The inverters, shunt, and MPPTs do the actual work; the Cerbo coordinates them and exposes the data.
- All 7 RJ45 ports look identical and carry different protocols. Label the ports as you wire them.
- Power the Cerbo from the busbar via small lugs on the frame mounting screws, not from a fuse stud.
- Trim the supplied cables to the actual distance. Coiled excess in trunking wastes the room you need for the DC main cables.
- Pair via Bluetooth first, join the home WiFi, then run firmware updates before relying on the unit.
