Howard, my Ferrari has a battery isolator switch fitted as standard but I've never really had battery issues with it.
Funnily enough, I bought my second Tesla a couple of weeks ago and when I arrived home from collecting it the diagnostic warnings system told me the 12V battery was failing and needed replacing! I had only driven 140 miles from the showroom to my house. Anyway, took it to the more local Tesla store in Birmingham and they swapped it out.
