question

tpwchr avatar image
tpwchr asked

How to use both Cerbo GX relays?

Hello everyone.

I need to use one relay for the Genset to switch ON when the battery bank (Pylontech) SOC goes down to 20% (lets say). and stop when the batteries get charged.


I also need a second relay for a device that needs to know the battery charge, ie that it will turn ON only when the batteries are full.It just needs the signal. How do I program this? In the comparisson table (https://www.victronenergy.com/live/venus-os:start#comparison_table) it says that the Cerbo has 2 x NO/NC.


Is this enough for what I need? (genset+the other device)


Thanks a lot

cerbo gxGeneratorRelay
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1 Answer
wkirby avatar image
wkirby answered ·

Relay 1 can be programmed for a generator start / stop between lower and upper states of charge.
Relay 2 is manual control, no progammable options.

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How can I do it if I need a second realy for it?

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Are there any other components in your system which have a relay or load output?

A BMV can have its relay programmed to switch at a certain SOC, likewise the smaller MPPT controllers have the load output which is programmable.

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Hi. Yes, the MPII has an Aux. Relay. I've been checking and I can use the relay in the MPII to start/stop the genset (https://www.victronenergy.com/live/ve.bus:virtual-switch-generator-start-stop) but I think if I connect the genset this way, I can not choose the generator to stop when the SOC reaches 95%. In the manual above I have only found that It allows you to start when SOC is xx% but only stops when it reaches a voltage or a time. Am i correct?


If I go this way, I would have available the relay in the cerbo gx for the purpose I need. Also reading that the relay closes when batteries reach XX% and opens when reaches YY% (and this value must be higher than the XX), so I would need to invert this option with some additional device because the cerbo is not capable of doing it by software. Do you know what type of device i need?


EDIT: Johannes Boonstra replied the following some time ago: yes, but as the VenusGX has the Nc-COM-No relay terminal to reverse the signal by wiring it the other way around.
so the reverse relay the ccgx needs is not needed here.

https://www.victronenergy.com/live/ccgx:generator_start_stop#conditions


Therefore is it possible to do what I want? I want the relay to close and send the signal to a device from another brand when the SOC is 90%-99% Basically I want this to derive the excess PV power to a water heater, and this device needs to know the SOC basically. I think I could do it through the realy 1 of cerbo, using the option start generator when SOC goes from 90% to 99% and wire it the other way around

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