question

The best way I can think of is to run NodeRED on the RaspberryPi and then use a modbus TCP module to read the parameters of the Pylontech battery from the VenusGX.
Then create a NodeRED flow to switch the GPIO outputs on or off as you wish.

It may be better to use the SOC value of the Pylontech rather than Voltage since Voltage does not change very much in the middle 40% or 50% of those batteries.

That's great, thank you for that, I need to do some more research to familiarise myself with the Raspberry Pi and Node-RED and then I will give it a go.

Ok so I have done some research into node-red and the Rasberry Pi and I think I am ready to give it a go. Thank you for your advice about using SOC instead of voltage, that will work better for my application.

Just one more question - Is the Raspberry Pi reliable enough to put into an off-grid system that we are going to be reliant on? Or am I better going for a Branded PLC such as Siemens or Schneider.

I would connect the Raspberry Pi to a UPS and I would of course keep it in a warm/ dry environment.

I would prefer to use a Raspberry Pi purely because of the amount of help and information available online, however, I do question whether a device that costs so little would be up to the job.

Any advice you could give would be greatly appreciated

Many thanks

Jonathan

You don't even need an extra device/Raspberry Pi, if you already have a VenusGX you can install the Venus 'Large Image' FW directly onto it, see https://www.victronenergy.com/live/venus-os:large.

I have very complex Node-RED logic and dashboard working fine on both a CerboGX and a VenusGX.

Even with a VenusGX or CerboGX you can still use Modbus and other protocols to communicate with/control external devices (like a compatible relay board or power regulation device), via Node-RED.

Ok thanks for that, that's even better as I already a Venus GX. Do you have any recommendations for compatible relay boards? I am looking to switch maybe 15 outputs in one location and another 10 in another location on-site (all connected to the same LAN). I have been looking but there are so many to choose from!