48V Vehicles

[trikkonceptz]

It has been a couple of years now, but I recall a buzz some time back about the future of the automobile and its conversion to a 48V system. From what I recall doing so would reduce the weight of the vehicle by using smaller lighter weight electrical cables, since they would not have to be of such heavy gauge.

In fact I remember seeing companies like Alpine developing car stereos that could support the 48V systems. Anyone know what happen to this idea? I have since not heard anything about it. I thought it would be a perfect fit for vehicles like the Volt, Aptera, next gen prius etc, yet no mention of it.

[Frank Lee]

My solution for electrical cable/component weight: don't load all that crap in there in the first place.

[Clev]

Originally Posted by trikkonceptz

It has been a couple of years now, but I recall a buzz some time back about the future of the automobile and its conversion to a 48V system. From what I recall doing so would reduce the weight of the vehicle by using smaller lighter weight electrical cables, since they would not have to be of such heavy gauge.

In fact I remember seeing companies like Alpine developing car stereos that could support the 48V systems. Anyone know what happen to this idea? I have since not heard anything about it. I thought it would be a perfect fit for vehicles like the Volt, Aptera, next gen prius etc, yet no mention of it.

That was the 42V system. Technically, it's a 36V system, but the alternator/generator puts out about 42V (14V x 3). I think that there was probably too much pushback from the aftermarket, since 12V parts are so commonplace and cheap. Additionally, the UL has set 30V to be the "safety limit" for wet locations/conditions, so manufacturers are probably uneasy about having higher voltages underhood.

[MazdaMatt]

Yeah, i think you're getting into the range that you can shock yourself, no? 12V can't be felt, but 120 sure as hell hurts... never touched high V DC though..

[Formula413]

I read that another reason for switching to 42V electrical systems was that it would produce enough power to operate a camless (solenoid actuated) valvetrain. Which would be the bomb if it actually comes to pass before the ICE only exists in history books.

As for the ouch factor, I know AC is much nastier than DC volt for volt.

[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...)

[Formula413]

Originally Posted by NiHaoMike

(I wonder how long it would be before someone develops some insane car audio system that runs from the high voltage...)

Aftermarket audio amplifiers for cars typically have inverters with step up transformers which feed rectifiers to create higher DC voltages for more power.

Good point about simply stepping the 42/48V back down to 12V to run low power accessories for backwards compatibility, seems like an obvious thing to do now that I think about it.

[NiHaoMike]

Originally Posted by Formula413

Aftermarket audio amplifiers for cars typically have inverters with step up transformers which feed rectifiers to create higher DC voltages for more power.

Good point about simply stepping the 42/48V back down to 12V to run low power accessories for backwards compatibility, seems like an obvious thing to do now that I think about it.

Except they're not doing it with 48v; they're doing it with even higher voltages. For example, the Prius uses 200v for the main electrical system.