I think the confusion is that it’s only visible in Service
Mode, not in the regular Service
menu.
To enter Service Mode, you go to the
Software menu, press and hold the word "Model" for 3 seconds, then type in "service" as the access code and hit ok. Here’s
one vid showing the process.
Once you’re in Service Mode, battery temps are viewable in 2 places:
Here’s the
TMC thread where I got the above images.
The main weakness of this is that you have to be in Park to enter Service Mode, so you can’t see battery temps while driving this way.