I wish my 2020 Prime charged the battery like my 90’s Toyota truck. I am having to trickle charge the Prime all the time practically as I drive short distances each day. The truck charges fast and tapers the charge, so much better system. I wonder if other ev’s slow charge the 12 v? I know a Tesla owner who said he has never charged his model 3 12 volt and has left it sit three weeks not driven. He didn't even know why I was talking about the 12 volt being charged.
'Smart' alternators are designed to reduce the load on the engine, in order to improve fuel economy. - I am not sure what they do to the 12v battery. I have never had one to 'play' with.