[NiHaoMike]

48v has been a standard in server rooms and telecommunications for many years. However, almost no electronics operate directly from that voltage. Therefore, it would make little sense to implement a 48v system in a car. Instead, the current solution appears to be a high voltage electrical system for the main and a standard 12v system for backwards compatibility. 12v happens to be a common intermediate voltage for running logic from high voltage power. (In many AC powered electronics, including most modern PCs, the AC power is first converted to 12v and then into whatever voltage the logic chips need.) The high powered stuff (drivetrain, HVAC, etc.) and the DC/DC converter for 12v are run from the high voltage system. If 48v at a significant power level is needed for whatever reason, use a DC/DC converter running from the high voltage.

BTW, I have heard a story where some amateur radio engineers managed to satellite upload at 38Mbps in a vehicle moving at typical highway speeds. They used an array of antennas and amplifiers driven by a DSP-based controller. The total RF power was well into the thousands of watts, so the amplifiers were run from DC/DC converters that tapped power from the high voltage system in the hybrid vehicle. I can easily see that as being useful for HD "camera cars" for news reporting, etc. (I wonder how long it would be before someone develops some insane car audio system that runs from the high voltage...)