Not a question as such. Posted in case it helps someone else in the future.....
I have two Pylontech 12VRT12100G31 batteries in parallel and I am running Venus OS version 3.20 on a raspberry pi. I did have an issue initially as I bought the two batteries from different vendors and the battery firmware on the second one was older than the original. Consequently they wouldn't talk to each other. I think the older firmware was v1.3 the current version is v2.1
This wasn't a deal breaker as my can hat on the raspberry pi controlling this had two channels. However I contacted Pylontech support who sent me an update program and the firmware binary file. The batteries come with a spare cable adapter as well as the link cable. I used a length of cat 5 cable and wired this up as ethernet 586B ie orange to pin 2 ground, brown white to pin 7 RS485A and brown to pin 8 RS485B. I used an RS422 to usb adapter like this https://tinyurl.com/52k9xp2s it worked perfectly and now I can connect both batteries in parallel and both show as online.