Tesla are moving away from 12v. I don't think it'll be that long before most also make the same shift.
Today, 48-V power systems are already helping improve the efficiency and performance of ICE and mild hybrid vehicles, but they will become an essential technology for tomorrow...
www.electronicdesign.com
On paper, 12v/48v wouldn't make any difference to the thread, if the requirement is to have a backup LV battery for safety systems then you'd need a 48v battery alongside the main HV battery.. that would still be able to be flattened..
However, reading that article, it seems they've taken the leap to remove the LV battery entirely "The vehicle's 48 V is derived from the vehicle's primary 400/800-V battery and then sent to 12-V power converters located close to the load points"..
Hmm.. they could have done that now, derived the 12v from the main HV battery, but they chose not to for (presumably) safety reasons..
My M5 has a lithium ion starter battery (standard fit) and it costs a fortune. EBay are selling them second hand for £600. I can’t seem to find the cost of one new in the UK online.
Edit: Just found it’s £840!
From 2022 onwards, Model Y/Model 3 have a 12v li-ion battery (went alongside the AMD Ryzen processor change).. however, since it doesn't need to crank an engine, it's not that large, so looks <£500 new, some are saying the Model S/X Li-ion battery from Tesla was $200..