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jr-neverjudge avatar image
jr-neverjudge asked

Cerbo GX / Globallink 520 to switch relay based on SOC

Good day, I have different installations with Cerbox GX and the Globallink 520 and whilst I am aware of the possibility to switch loads with the Smart Battery Protect based on Voltage, I would also really like to be able to switch loads based on SOC; i.e. run a little heater but only if SOC is over 95% ... can't use voltage for this because as soon as the sun is up my voltage is over 14V no matter the SOC. Basically I want to do the opposite of load shedding so i.e. charge my batteries first to, say, 75% and then activate the inverter to charge other devices on the 230V circuit. I hope this makes sense, any Idea how to do it? I tried with the Generator output on the Cerbo but that basically is just the other way around ...

cerbo gxSOCBattery Protect
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3 Answers
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matt1309 answered ·

Hi @jr_neverjudge


I personally do this using a shelly smart switch activated by node red running on GX device. They're relatively cheap switches and using them in node red was really flexible in comparison to what i'd heard about doing what you suggested.

In my opinion it's much more flexible in terms of criteria/using multiple loads. The shelly smart switch works on LAN and can be turned on via HTTP request. It's good for 16amps which is fine for most water heaters.


I think there is a way to do it the way you mention using VeConfigure Assistants but not sure if SoC criteria is one of the options (it's far more limited at least), I've not looked into it much after realising that node red + a smart switch worked better for my use case. (You can get really fancy with node red. I have multiple loads ie turn on water heater 1, if that's on already and still have excess power turn on water heater 2 etc.... Then if winter turn on electric heater i have in one of the colder rooms in my house).

Happy to share more node red details if useful.


Edit: Just looked in my node red on cerbo gx and can see relay options for my smart shunt and solar charge controller. So you may even be able to use those instead of an external shelly smart switch (although the smart switch is probably easier for longer distances).




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jr-neverjudge avatar image
jr-neverjudge answered ·

Thanks Matt, I was hoping there is an easy way to do this also with the Globallink but after reading a lot, I guess I need to buy another Venus and go the Nodered-route ... my programming days are long gone but might need to revisit those. It's just a pity I think that all the features are there but it's just not flexible enough to program this easy if-then switch ... I have installed node red on one of the installations and see if I get it to work ... might come back here for more ;-)

Edit ;-) .. yes, I´ve seen those relay controls as well, in theory should be relatively easy to create a conditions based on the shunt and trigger / control the relay ... since most of my installations are a bit cramped for space I try to use as few devices as possible, i.e. use what is there already (Smart Battery Protect being one) ...


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matt1309 answered ·

I'm not familiar with GlobalLink, but you can install venus os large on cerbo gx if you've got one, that comes with node red then.

(personally i use a raspberry pi if you're looking for a more affordable option).

I was similar re-programming, but recently i delved into it and node red is very forgiving. Especially if you have basic criteria/inputs ie SoC > x can maybe even get away with little to no programming then.

If you've ever programmed before (ie understand an if statement). Then you'll find it easy (and if not there's always chatgpt....).


Shout if you do go this route, happy to share functions/snips of node red if helpful.

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