Even if one was not into competition but had a competent, hi-power, after-market car audio set-up, the replacement of the alternator w/a hi-power version can provide near 400Amp, if needed....
...The people involved in car audio SPL competition ("SPL drag racing") often use multiple batteries.
Yet, in the realm of 21st Century EV transportation, I don't know if a thing as an 'alternator' even exists anymore.
[NOTE: From my understanding, most EVs do have a "12V" battery sub-system.]