Not sure where Mex's solution would fit in with this scenario, but meanwhile, looking at alternator protection, there is some idea here that a surge could come from a broken cable. Not clear to me-anybody comment?
https://www.sterling-power-usa.com/SterlingPower12voltalternatorprotectiondevice.aspxLooking into their DC-DC gizmo to see what it does re 24-12 with a 12v engine battery. Will post if find anything.
EDIT--found it! they are actually 12-12. BB does have the 12-12, but on page 2 of their "shop" (didn't see that before). Anyway this blurb (long) explains the regen alternator system in new vehicles and how that can wreck your House batts unless you use one of these gizmos.
https://www.sterling-power-usa.com/BBW1260-60amp-sterling-power-probattc-batterytobatterycharger12vto12v.aspx
