I have read the page showing lithium battery compatibility at https://www.victronenergy.com/live/battery_compatibility:start, but still don't understand why you cannot use an unapproved lithium battery?
My understanding of lithium batteries is that most have an onboard BMS, that manages individual cell voltages and charging rates. If this is the case then what benefit do you get if the GX device can communicate with the onboard BMS? Is it just so that you can read the individual cell voltages through the VRM?
Any clarity would be much appreciated!