Mitmat

Over the years I've read through many posts on Powerforum while trying to problem solve my own installation "bugs". I hope I can give a fraction of that useful info back.
I've seen a lot of posts relating to inverter/ battery comms. frustration. 
I recently installed a Growatt SPF3000TL-48V with a  Pylontech US3000C battery and had what seems to be the expected battery/ inverter comms cable issues. Using the RJ45 type comms cable supplied with the cable kit, I got warnings "04" (low battery) and "20" (BMS communication error) on the inverter.
But the first problem was actually the the baud rate DIP switch on the Pylontech US3000C, - which in this case was installed upside down. Below is a picture of the correct settings (binary 1000) for 9600 baud, which I think is the standard RS485 baud rate for the Growatt BMS port.

 
Communication cable solution:
In the Growatt user manual on page 8 are the pin allocations for the inverter side of the cable.

In the Pylontech US3000C manual also on page 8 are the pin allocations for the battery side of the cable.

As this inverter doesn't have a CAN port we are only interested in the righthand column, - below the heading B/RS485.
According to the info in the manuals, we need to connect the following together:
Pin #1 on the inverter side  to  pin #8 on the battery side.
Pin #2 on the inverter side  to  pin #7 on the battery side.
Pin #3 on the inverter side  to  pin #6 on the battery side (GND).
I didn't have a RJ45 crimping tool and plugs, so I used the short battery link cable that came with the battery. I cut it in half and stripped the outer insulation off.
This is just to get you up and running until you have the proper cable made.

Cables to be soldered together as follows:
Inverter side Orange/white (pin #1)  to  battery side Brown (pin #8)
Inverter side Orange (pin #2)            to  battery side Brown/white (pin #7)
Inverter side Green/white (pin #3)     to  battery side Green (pin #6)
My battery was right under the inverter so I didn't need to extend the 3 cables, but in most cases you will need to.
Insulate the solder joins with heatshrink or tape.
Plug the cable into the inverter BMS port on the inverter and the RS485 port on the battery, make sure it is the correct way around. ie. Inverter side to inverter and battery side to battery.
Inverter settings:
Don't turn on the mains utility suppy or connect the solar panels to the inverter yet. You don't want there to be any chance that the inverter will attempt to charge the battery until the settings are correct.
Go to menu #5 and select Li for battery type and push enter.
The inverter will automatically take you to menu #36 for communication protocol, select L02 and press enter.
 
This is tried and tested, - you should have no more problems.