askii avatar image
askii asked

Off grid system. Switching in extra load when SOC 100%

We are designing and off grid system with a solar array though a couple of Smart MTTPs. There is almost certainly a Cerbo GX in the system. During the day when the SOC reaches 100% we would like to be able to send any further solar energy to a simple DC heater. This would need to switch out when the MTTP were no longer exceeding the normal system load.

We hoped to program the Cerbo relay to control a high power relay. Is this possible. Or is there another way. I noted the Cerbo info state "diverts excess (solar) power to self-consumption" but fail to find an explanation.

Many thanks for all contributions


cerbo gxESSoffgridRelay
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
tozz avatar image
tozz answered ·

The Cerbo has outputs you can use. Those are not high power relay outputs, but you can use a relay to switch bigger loads.

You can use the "stop/start generator" relay function in the Cerbo to switch your heater. If you set relay 1 to "stop/start generator", you can then configure

"Use battery SoC to start/stop" -> on

"Start when battery SoC is lower than" -> eg 90%

"Stop when battery SoC is higher than" -> eg 98%

You will have to invert the relay's output, but that should be no problem since you'll have t use an external high power relay anyway. The Cerbo's relay are not suitable for high power loads.

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Rob Duthie avatar image Rob Duthie commented ·


You can use a assistant in the inverter. as it will free up the Cerbo relay as genset control.

May be Victron if they listern that the second relay in the Cerbo should have this added as function instead of only a simple temperture control?

As this function works very well in sites i have set up, but if was in the Cerbo it would much easy for the client to change than trying to add a assistant.

programmable relay (size:30)

*) Use primary programmable relay.

*) Set relay on

*) when SOCHigher than 99%.

programmable relay (size:30) 1

*) Use primary programmable relay.

*) Set relay off

*) when SOClower than 95%.


Rob D


0 Likes 0 ·