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Enhance Your Victron Cerbo GX with Node-RED

Originally published: 2024-03

The Victron Energy Cerbo GX is the brain of many RV, boat, and off-grid systems — and with Node-RED it becomes programmable. The killer application: smart generator control. Instead of tripping a generator with oversized AC loads, a Node-RED flow watches the generator state and adjusts the inverter’s AC input limit on the fly. This guide walks through how the detection works, why dynamic input limits matter, and how to get Node-RED running on the GX.

Quick answer: Under Venus OS Large, the Cerbo GX runs Node-RED natively. A flow reads a generator signal — via an IO input or a digital sense wire from the transfer switch — and dynamically adjusts the inverter’s AC input limit so large loads never overload the generator. The result is seamless generator integration without manual settings changes.

Watch: smart generator control on the Cerbo GX

The video walks through the full build: wiring a digital sense wire from the RV’s auto transfer switch to the generator contactor, configuring the Cerbo GX to recognize generator activation through an IO input, activating Node-RED under Venus OS Large, and writing the flow that adjusts the AC input limit in response. Watch how the system reacts the moment the generator starts — that transition is the whole trick.

How does the Cerbo GX detect generator operation?

Two common detection paths exist, and the video uses both concepts:

  • Digital sense wire: a wire from the auto transfer switch’s generator side to the generator contactor gives the Cerbo GX a direct electrical signal that generator power is present.
  • IO input signal: the GX’s programmable inputs can be configured to recognize the activation signal, so the system knows the generator is running before any load logic kicks in.

Once detection is in place, the GX can react automatically — that is the foundation everything else builds on.

Why adjust AC input limits dynamically?

Large systems have a mismatch problem: an inverter can pass more AC load than a generator is rated to supply. Static input limits either waste generator capacity or risk overload. A Node-RED flow solves this by watching the generator signal and raising the AC input limit when the generator is running and pulling it back when it is not — so heavy loads are only ever offered to the generator it can actually carry. That protects the generator, the inverter, and the batteries from the classic overload cascade.

How do you enable Node-RED on a Cerbo GX?

Node-RED ships with Venus OS Large, Victron’s firmware branch for advanced users. After activating it, flows run directly on the GX and talk to the system over its local interfaces — subscribing to system data and writing settings such as the AC input limit. The video’s walkthrough covers activation and the first flow from scratch; the official Venus OS documentation (linked in the sources) documents the current setup steps.

What else can you automate once Node-RED is on the GX?

Generator load management is only the start. The same flow patterns extend to generator start/stop on battery state of charge, load shedding when SOC drops, and custom alerts. For remote visibility, Victron’s VRM portal complements the local logic: it aggregates system data in the cloud, while Node-RED handles the fast, local decisions. Together they cover both sides — local control and remote monitoring.

Adding buffer capacity: generators are not the only answer

Anyone running a Cerbo GX already lives with batteries — and sometimes the smarter move is adding buffer capacity instead of generator runtime, especially for remote sheds, trailers, or quiet hours. When comparing portable power stations for that role, look past the marketing watt-hours: measured usable capacity and real runtime at your actual load are what count, and a runtime calculator makes the math honest before you spend. Our portable power stations compared on measured runtime page collects exactly those numbers.

If you buy through links on the sites we recommend, we may earn a small commission.

Frequently Asked Questions

Does enabling Node-RED affect my Victron warranty?

Venus OS Large is Victron’s official firmware branch that includes Node-RED, so running flows is a supported path. As with any advanced firmware, keep backups of your configuration and update deliberately.

Can I use these flows without a generator?

Yes. The same IO-input and flow patterns work for shore power detection, load shedding on low state of charge, or any rule you can express as “when signal X, change setting Y”.

Where can I monitor the system remotely?

Victron’s VRM portal aggregates Cerbo GX data in the cloud and works alongside local Node-RED automation — local logic for fast decisions, VRM for history and remote alerts.

Further reading

Sources

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