Most cars use a 12-volt system to power their electrical components. But, with more and more electric bits and bobs being added to new vehicles, a dozen volts is looking a bit weak these days. In fact, Audi says that standard 12-volt systems are being stretched "to their very limits." Enter 48 volts.

If used in a car that gets 40 mpg, that would translate to around 43.5 mpg.

Audi is testing a supplemental 48-volt electric system in two prototype vehicles – modified mild-hybrid versions of the A6 TDI and the RS 5 TDI – in order to add in more electric technology (an electric compressor, for example, to improve acceleration) and "convenience systems for dynamic chassis control." Audi says it has more applications in the pipeline, but the overall gist is that the German automaker sees 48 volts as an "important building block in electrification strategy."

As you can see in the picture above (click to enlarge), the RS 5 TDI concept uses a li-ion battery installed in the back of the car and an alternator to provide 48 volts when the engine is off. Audi says that the 48-volt system can save up to 0.4 liters of fuel per 100 kilometers. To put that into US numbers, if used in a car that gets 40 miles per gallon today, that would translate into a bump up to around 43.5 mpg.

The Advanced Lead Acid Battery Consortium (ALABC) is also working on a 48-volt system to improve fuel economy and we've got a deep dive of Audi's electric turbocharger here.
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Even more powerful and efficient – the new 48-volt technology from Audi

Important building block in electrification strategy
More voltage and more power for new technologies
Scalable platform concept suitable for wide-ranging uses

Ingolstadt, August 25, 2014 – Audi is to upgrade part of its vehicle electrical system from twelve to 48 volts. The move represents another technical building block for facilitating the integration of new automotive technologies while increasing the power and efficiency of its cars.

"We are using the full bandwidth of electrification in our drive principles strategy. Running part of the vehicle electrical system at 48 volts plays a central role in this," commented Prof. Dr. Ulrich Hackenberg, Member of the Board of Management for Technical Development at Audi. "It enables us to make more energy available. That paves the way for new technologies with which we can make our cars more sporty, more efficient and more convenient to use."

Audi recently showcased the scope of the 48-volt electrical system with the technology demonstrators Audi A6 TDI concept and RS 5 TDI concept. Both models are fitted with an electrically powered compressor. This operates independently of the engine load and therefore fundamentally improves the acceleration performance. 48-volt technology is moreover ideal for realizing convenience systems for dynamic chassis control. Audi will shortly be unveiling a variety of applications in this field.

The current state of the art technology has taken 12-volt electrical systems to their very limits. Especially at low temperatures, all the various static-load consumers can account for the entire power generated by the alternator, which can deliver up to three kilowatts. The battery power is no longer capable of meeting the demands of new, dynamic-load consumers such as high-performance electric compressors.

The solution is a second subsidiary electrical system running at 48 volts, to complement the 12-volt power supply. The higher voltage means smaller cable cross-sections are needed; this translates into lighter cable harnesses with lower power dissipation. The 48-volt electrical system features new storage technologies and delivers much more power than the 12-volt system with lead batteries. That makes it an important element of the Audi strategy of electrifying various stages of the drivetrain. The Group's developers have already come up with a scalable platform concept, including a version that incorporates the electrically powered compressor.

In currently the highest development version, a compact lithium-ion battery supplies 48 volts as the energy source during engine-off phases; a DC/DC converter integrates the 12-volt electrical system. The lithium-ion battery operates in conjunction with a new, efficiency-optimized alternator that qualifies the drivetrain as a mild hybrid. Within this concept there are diverse ways of starting, controlling and deactivating the combustion engine as needed. The powerful alternator achieves an energy recovery output of ten kilowatts, far more than is possible at present. That adds up to a saving of up to ten grams of CO2 per kilometer (16.1 g/mi), equivalent to around 0.4 liters of fuel per 100 kilometers (62.1 miles).

*The collective fuel consumption of all models named above and available on the German market can be found in the list provided at the end of this MediaInfo.


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    • 1 Second Ago
  • 17 Comments
      Anderlan
      • 3 Months Ago
      If this hastens the end of lead acid, I'm all for it!
        BipDBo
        • 3 Months Ago
        @Anderlan
        What's wrong with lugging around a big box of heavy lead and corrosive acid? /s
      danfred311
      • 3 Months Ago
      makes pigs fly
        DaveMart
        • 3 Months Ago
        @danfred311
        Hi Dan. How's your prediction that German companies would never actually build a BEV or a PHEV going?
          danfred311
          • 3 Months Ago
          @DaveMart
          Dave, I made no such prediction as Paul correctly corrects you. I have always said they will join us or die. You may have made the wrong conclusion because I often say fresh lies from a german automaker. They lie a lot like the soulless corporate douches they are. If it was up to those nitwit douches they would never make an electric car. But it's not up to them. My comment reflects their lameness and that this pos news item of course wont do at all. But unfortunately things are moving very very slowly. It's battle of the nitwits. Like a bunch of drooling Stephen Hawkings duking it out. There is not a relevant electric car on the market anywhere in the world yet and none on the horizon. Because they are universally morons and you sheep don't task them. I refer to the facepalming statue in France again.
          danfred311
          • 3 Months Ago
          @DaveMart
          Dave, you're a massive tool. You don't have to be in such a hurry to say dumb things. It's entirely optional. Maybe reevaluate your life.
          DaveMart
          • 3 Months Ago
          @DaveMart
          Wow! I must have seriously misread umpteen comments that electric cars were a head-fake by the German manufacturers which they had no intention of bringing into production, and if they did only in compliance vehicle numbers. Unfortunately Dan, prophets develop a track record and people notice when the end of the world does not happen on schedule, although said prophets invariably try to re-write history.
          DarylMc
          • 3 Months Ago
          @DaveMart
          Hi Dan I would like to thank you for pointing me to the face palm statues. It was quite funny. But I don't think it is those who criticise that change the world. It's the people who are actually out there doing it.
          paulywesterberg
          • 3 Months Ago
          @DaveMart
          It was the Audi CEOs who said they would never build BEV or PHEV. Audi Chief Calls Chevy Volt “A Car For Idiots” http://gas2.org/2009/09/03/audi-chief-calls-chevy-volt-a-car-for-idiots/ Dan's prediction that they build electric or die seems spot on.
          DaveMart
          • 3 Months Ago
          @DaveMart
          I did not know Audi were the only German company, Paul. I must have been mistaken about the nationality of BMW and VW. A prophet is often without honour in his own country. Especially when he talks complete rubbish.
      BipDBo
      • 3 Months Ago
      "the RS 5 TDI concept uses a li-ion battery installed in the back of the car and an alternator to provide 48 volts when the engine is off." What? Am I the only one who does not understand that statement? Instead of "alternator" should it say DC/DC converter?
      DaveMart
      • 3 Months Ago
      This is part of their recently announces deal with LG Chem for batteries, worth 'hundreds of millions' over an unspecified time period.
      Tweaker
      • 3 Months Ago
      ""the RS 5 TDI concept uses a li-ion battery installed in the back of the car and an alternator to provide 48 volts when the engine is off. "" This article makes no sense. They show two separate systems except there is no source for 48v. And why have a dc-dc converter when you already have a complete 12v system?
        DarylMc
        • 3 Months Ago
        @Tweaker
        Hi Tweaker The articles often make no sense. If you check out the press release and the images you will see that the system is mainly designed to implement an electric turbo/supercharger. They can't do that well on a 12v system. Stop start systems, electric power steering and others could also benefit by a higher than 12v battery system.
        HVH20
        • 3 Months Ago
        @Tweaker
        Boost 12v to 48v.
      David Murray
      • 3 Months Ago
      I remember hearing 20 years ago that cars were going to switch to 48V and it has yet to happen. I think most of the systems in the car are happy to run at 12V, especially since a lot of the lights are starting to switch to LED. But I definitely think it is time to ditch the alternator design and have everything become a "mild hybrid" so that the same motor that starts the car also generates power. There should be no belts, everything should be electrically driven to increase longevity and decrease maintenance and friction. So A/C pumps should all be electric too.
        CeeJayABG
        • 3 Months Ago
        @David Murray
        David: I remember this movement beginning, too. The Lucas company was still around as an entity and was a huge advocate. They also predicted a wave of automotive-based electronics finding its way into aerospace, particularly in power control/conditioning. They had it right (BTW, I was no fan of Lucas, so don't mistake my recalling them), but too early -- being right early is often the same as being wrong. What was needed was a significant improvement in the yield and cost of power electronic components, which happened somewhat of its own, and also as a result of the start of production-scale auto electrification (e.g, hybrids). What's interesting today is to see the incredible synergies of sensor, computation, and power control/conditioning handing off back and forth between EV and ICE. It's hilarious to hear the purists on each side who apparently do not see the ascending confluence of improvement for both propulsion strategies. If you are simply a fan of better, more efficient mobility solutions, you are ecstatic. I agree with everything you have to say about improvements to ICE through electrification -- the "beltless" engine module. Toyota was the first to "reach beyond their grasp", and it seemed that the European companies would never get there. Now I'm beginning to think Audi is going to take the lead, particularly as they have come to embrace the electric supercharging solution. The benefit from designing the optimum turbine and compressor solutions without being bound by the compromises of a shared shaft is enormous. Adding in the immediate response and system optimization from ultracaps doubles the possibilities. BTW, something that seems OT but isn't. The news last week that Infineon is buying International Rectifier should be big news to all of us. The combination of a world-leading auto computation designer/manufacturer/packager along with a best-of-breed power electronics company is going to further drive out cost and create some extraordinary value. The commoditization of auto electrification is about to take a quantum leap, and it is primarily Europe-focused. Congrats to all future drivers; it's gonna be great.
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