I was trying to buy this cable from the official supplier but they did not have it available. Looking online I could not find a reliable source. I ended up following some guidance from Powerforum.co.za but this was still a bit unclear. Ultimately I referenced the manuals for the battery and the inverter for the pinouts to crimp my own cable.

Canbus uses three cables for communication CAN-H, CAN-L and GND. A common GND is needed to ensure the CAN-H and CAN-L is referenced off a common potential difference. You basically need to connect CAN-H on the battery to CAN-H on the inverter, CAN-L on the battery to CAN-L on the inverter and GND on the battery to GND on the inverter.

From the Sunsynk 5.5kw manual v20

From the pylontech US3000C manual 20CQSV1103

As you can see in these figures both have Pin 4 as CAN-H and Pin 5 as CAN-L and the battery has Pin 5 as GND but the inverter does not specify a GND pin. I scoured forums an documentation and could not get a conclusive answer. Everything pointed to the battery pinouts that are listed in the Sunsynk training manual and list CAN GND on pin 8 but the CAN-H pin is listed incorrectly.

I ended up making a cable that connects Pin 4 - Pin 4; Pin 5 to Pin 5; and Pin 6 to Pin 6 using the oreintation provided in the images from the manuals

This is what the connector looks like on both ends. Colours from left to right White-Orange, Orange, Green. It is important to note that the battery manual stipulates that pins 1 -3 should be left unconnected.

Canbus cable Pylontech US3000C to Sunsynk 3.6kw/5.5kw

Notes

I tested this on SUNSYNK-5K-SG01LP1/SUNSYNK-5K-SG01LP3 but it should also be the same for SUNSYNK-3.6K-SG01LP1/SUNSYNK-3.6K-SG01LP3, SUNSYNK-3.6K-SG02LP1 since they share the same manual. The GND could be completely wrong but I have no clear indication what would be the correct pin. I emailed Sunsynk to confirm this but have yet to receive a response.

End