Yeah, max CV charging voltage is ~14V, max charging C rate is ~0.2C, open circuit voltage at 100% is that 13.x range. And lead acids like to stay at 100% unlike Li-ion which likes 50% +/-30%, so "12V" ICE cars just use a bus voltage of 13-14V and wire the battery there. At any given moment, the car's "12V" bus voltage MUST be above 13.x and below 14.4(absolute max).

It's a bit perplexing that those lead acid systems are referred to as "12V" systems when that figure is effectively the 0% voltage, whereas 3.7V for single Li-ion cell is the 50% voltage.

e: also, ICE transients can be in kV range, coming from ignition mechanisms. I've heard that you can literally measure engine RPM by selecting 1/dt on an oscilloscope and dividing that by cylinder count.