rosslewis48 Thank you, it’s the password to connect the inverter dongle Wi-Fi.
The inverter dongle should be advertising its own wifi hotspot. Is that the password you're looking for ? Unfortunately, that will have been set by your installer. Ideally they'd have told you, but my installer didn't tell me, so there's a good chance they didn't.
It might have been set to the serial number of the battery. Mine was set to either 12345678 or 123456789.
It's actually simpler to change your new router to use the same AP name and password as before - ideally your broadband provider would have done that as part of the switch, but I guess not. Do you still have the old router? Again, I'm guessing not.