Thanks @Mark_T, I’ll give that a go. I have a similar setup with Zappi, Octopus etc.Not yet had to worry about the 'Fleet' API as I'm not trying to connect to a Tesla vehicle at this time, just the PW2...
So I'm using the standard Tesla Powerwall integration and the Tesla Custom integration just for setting the battery reserve.
The only bit that needed a little effort was obtaining the current PW2 SoC as the custom integration no longer gets that data after one of the recent changes to the API, but it isn't hard to approximate it from the SoC data in the standard Tesla integration as that can return the total SoC for each PW2 pack in your system.
Not sure how useful my automations would be though as they are driven from the Zappi API and the Octopus API so they are a bit specific, but happy to answer any questions if you are having problems with your particular setup...
I haven’t tried the Tesla Custom Integration yet. I didn’t know Powerwall was not subject to Fleet API.