BuciboLebo

Tried to no avail, all options show a time out. I have asked Solar Assistant support for a cable pinout diagram to ensure the RX and TX are correct as WatchPower doesn't pick up anything on COM5.
DessMonitor with the Dongle seems to work fine for all 3 of them in parallel 

My friend got one working by setting it to as a Growatt - worth a try

That's an Axpert-style screen,but Fivestars can be iffy (other poster noted it may read as a Growatt)
You'd likely have to remove the Dongle and connect a serial-to-usb cable to a Solar-assistant Pi to read it

The man is asking how, given that there is no apparent BMS Comms port on the inverter itself. Just because the option is available in the software interface does not mean that it's it will with, especially since we know fivestar are Hodge podge clones

Perhaps try what Solar Assistant suggests on this page first.
Axpert Kodak Mecer MPP Solar Phocos RCT Richsolar (2.4kW, 6kW and 6.5kW) etc.
"If you have any issue, please try the official WatchPower or SolarPower application from a laptop. If it works with these official applications, then it should work with SolarAssistant."

https://solar-assistant.io/help/voltronic/configuration

The recommendation is that you use batteries that are of the same size, manufacture, age and chemistry. Due to practical considerations sometimes one ends up mixing batteries of different ages (replacing a dud battery for instance) or mixing batteries of different capacity 232Ah and 236Ah from the same manufacturer (the difference is essentially minimal).
I would however never mix batteries from different manufacturers or different chemistries.