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 ( 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 ( 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.

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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