Many Victron products have programmable relays included which can be used to send signals between each other or to control small loads. These ae typically rated as for the Cerbo GX as
DC up to 30 VDC: 6 A
DC up to 70 VDC: 1 A
AC: 125 VAC: 6 A
There have been many reports within the community from people who have burnt out the contacts or welded the contacts closed in the programmable relays in their systems.
This is often caused by connecting the relays to inappropriate loads, sometimes loads that are too large, but more often loads that have an inductive or capacitive load that create large start up or shut down spikes such as motors, relays, voltage converters even though the normal current is within the specification.
If the normal current required by the device connected to the Victron relay is close to or above the rated current, then you must use a larger relay to switch the device on and off. The output of the Victron relay is then connected to the input of the larger relay coil, and the larger relay to the load. See further down for more details on relay wiring.
If the device connected to the Victron relay is a motor that has a current draw more than 1/6th of the rated relay current (1A at <30VDC, 0.15A at 30<70VDC, 1A at 125VAC), then the start-up peak may be higher than the rated current and this should be controlled by a larger relay. It should be noted that motors often have start up currents up to 6 times higher than the rated current.
If the device connected to the Victron relay has capacitors on the input, then this should be controlled by a larger relay.
When wiring up a relay to the Victron device it should be remembered that relays themselves are inductive devices and can generate large reverse voltages when they are switched off (back emf). These voltage spikes can cause short term high currents which could damage the Victron relay. It is best to add a flyback diode or purchase a relay with a flyback diode to eliminate these voltage spikes. The flyback diode is also known as a snubbing diode.
The relay could also be replaced with a solid state relay. High quality solid state relays such as the Victron SolidSwitch 104 or Battery Protect devices have low input current requirements and are suitable for this function and will not cause any damage to the programmable relay. However, budget solid state relays have been known to generate voltage spikes on start up shut down which can cause damage to the switching device.