Following more research Zarch was exactly right - I have a hybrid inverter and all the input/output cables with the exception of a connection to the grid are DC. This means at very best I’ll be able to monitor energy that originated as solar. However won’t be able to split out battery charge/discharge and direct usage.
In contact with Solis to see if they can give me access to their API to get the data correctly. There’s some reports of people online who have been successful. Others not so much. Wish me luck!