Heat can build quickly in an RV electrical compartment when an inverter, solar charge controller, and other components are working hard. Victron relay outputs can automate cooling fans so airflow increases when the system needs it.
Where relay control may be available
Depending on the installation, relay outputs may be available on a Victron solar charge controller, inverter, or GX device such as the Cerbo GX. The available conditions and configuration choices depend on the exact model and firmware.
What NO, C, and NC mean
- NO (normally open): the contact remains open until the programmed condition is met.
- C (common): the shared relay terminal.
- NC (normally closed): the contact remains closed until the condition changes.
Fan-control circuits commonly use NO and C so the fan stays off until the selected trigger occurs.
Use an external relay for fan power
Do not run the fan's operating current through small dry contacts unless the equipment documentation specifically allows that load. Use the Victron contact to trigger an appropriately rated external relay, and let that relay switch the fan power. Match the fan and relay coil voltage to the 12V, 24V, or 48V system.
Useful trigger choices
A solar charge controller can activate a fan based on power output, providing airflow while the controller is producing and often when daytime temperatures are highest. Compatible inverters may offer relay logic related to charging or load. A Cerbo GX can provide another control point and may allow remote manual control when connected.
Some Big Beard Battery systems reserve Cerbo relay 1 for generator auto-start, leaving relay 2 as a practical option for ventilation. The correct choice depends on the complete system design.
Plan the airflow path
A fan is only useful when air has a clear way into and out of the compartment. Use suitable overcurrent protection, keep wiring secure, and follow the manuals for every connected device.
Need help planning your RV power system? Complete our System Design Form, and the Big Beard Battery team will help you determine the right batteries, inverter, solar, and supporting components for the way you travel.