Above 30V - 50V DC, contact arcing becomes a huge problem. (It's a problem below that, but less huge.)
With AC, the arc will self-extinguish a half-cycle after the switch opens. With DC there is no cycle, and contacts can be completely vaporised in tens of milliseconds.
Commodity switching components are usually rated "30V DC, 250V AC" for this reason.
It is possible to design switches so that even DC arcs self-extinguish, but the result is expensive and not as reliable as one could wish.
If cars had been invented after 1980, they would probably use solid-state switches except for the very high current circuits such as the starter solenoid and headlights. (Transistors were around a lot earlier than that, but engineers are sensibly cautious about new technologies.)
Edit: To answer your question directly: no. Cost is prime.
if we are going to 48V then pretty sure all power switching would use solid state relays/MOSFETs, Any mechanical switch would just be the input to a micro at 5V or lower.
You could also just switch the HV (400V+) bus directly down to 48/60V as all the high current devices motor/ac/power steering etc run off the HV bus and you would just be left with lights, entertainment and servos on the low voltage side. The 12V battery is probably a bit silly when you have a 50KWH main battery and 97% switching conversion efficiency regulators and I am guessing it may disappear in the next 10 years
Yes, my Model Y has a "traditional" 12v lead acid battery. Granted its a small battery as it doesn't have to run any heavy loads (starter motor). Furthermore, it's my understanding that newer Tesla vehicles are being delivered with 12v gel batteries instead of the the lead acid design.
>To answer your question directly: no. Cost is prime
I meant to the customer or owner, over the normal lifetime of the vehicle, not to corporate accountants that translate pennies into millions of dollars.
"More expensive" presumably is a small amount per car; the average new car in the US is over $40K.
With AC, the arc will self-extinguish a half-cycle after the switch opens. With DC there is no cycle, and contacts can be completely vaporised in tens of milliseconds.
Commodity switching components are usually rated "30V DC, 250V AC" for this reason.
It is possible to design switches so that even DC arcs self-extinguish, but the result is expensive and not as reliable as one could wish.
If cars had been invented after 1980, they would probably use solid-state switches except for the very high current circuits such as the starter solenoid and headlights. (Transistors were around a lot earlier than that, but engineers are sensibly cautious about new technologies.)
Edit: To answer your question directly: no. Cost is prime.