I contacted my electrician today and asked him to request the Modbus register list from BYD. I have a Fronius SYMO Gen24 10.0 Plus Inverter with automatic Backup funstionality in case of a power outage, but since BYD Batterypacks are currently unobtanium I want to use a different one idealls with a controller just like what you are building. the Fronius Iverter is ily certified for the BYD HVS/HVM systems. Communication is over Modbus RTU using the SunSpec registers. I have received a list of the inverter registers from Fronius, but so far lack the registers for the BYD.I already, saw this document, and if I am right it has been in this thread.
Unfortunately this description does not match to the measurements and logs I did.
Baudrate is matching but the header is differently, the CRC calculation is done in an other way and even the numbers are representated in an other format.
In my logs, the numbers are transfered as IEEE floats, in the linked document they are transfered in mV, mA oder 1/10 V, so as integers.
There is also A guy in Finland working on basically the same thing.
and furhter Videos describe hie Progress in bringing a broken BYD batterypack back to life, his final goal is to replace it with used Nissan leaf batteries, since he refurbishes them for a living - if I understoof him correctly that is. If you get your design working I would be very interested in one for my Projects, and also more than happy to cooperate. My background is mainly in Linux system management and High availability, with some knowledge in mechanical engineering and electrical engineering (as part of my school/Uni curriculum, not as a licensed electrician).