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48 V Technology

in Production Cars

Electrification

in the Aftermath of the

Diesel Scandal

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The first series production cars to incorporate48 V technology in one form or another have hitthe road in recent times, and further integration of48 V architecture is expected in the very nearfuture. The Bentley Bentayga and the Audi SQ7are the first two vehicles to incorporate a highervoltage electrical system, and the industry as awhole is gearing up for further development in thecoming years.

Higher voltage systems are nothing new, of course,some 20 years ago 42V electrical systems wereslated to be the next step in vehicle electronics.However, OEMs quickly discovered that high costsoutweighed the benefits, and instead concentratedon better power management of 12 V systems. Theincreasing demand for power for performance-enhancing, self-driving, and safety technologyrequires new architecture, while regulatorydemands to improve fuel economy and reduceemissions are also key issues.

As we know the CO2 emissions target forEuropean manufacturers is 95 g/km by 2020, andone trend towards achieving that goal is to use48 V systems within an existing powertrainframework to create ‘mild hybrids’ - conventionalmodels with increased electrification for powerhungry sub-systems such as turbo compressorsand active suspension.

Having considered 60 V technology, the big fiveGerman carmakers - Audi, VW, BMW, Porsche andDaimler - agreed in 2011 to use a commonframework for a 48V embedded power supply infuture vehicles. Since then much progress has beenmade in what will be a major change in theautomotive industry, and the technology isexpected to become mainstream very quickly. So,how have these new vehicles implemented 48 Vtechnology, and what developments can we expectto see beyond 2020?

Bentley was the first to market with a 48 Vapplication, introducing its Dynamic Ridetechnology in the new Bentayga. The Bentayga isthe British carmaker’s first SUV and features anelectrically actuated suspension system thatresponds faster than a conventional hydraulicsystem to cope with the demands of both on-roadand off-road driving.

To manage the various demands of differentdriving surfaces, Bentley have split the Bentayga’santi-roll bars and fitted electric motors betweenthe two halves. The system uses planetary gearsets to multiply torque, and can deliver up to 959pound-feet of torque to each anti-roll bar. Whendriving on-road the system is most effective oncorners, where the motors drive the anti-roll barsto press down on the outside wheels and lift theinside wheels to counteract body roll. Whenencountering bumps in the road and unevensurfaces, the motors produce upward force to liftthe wheels, thus reducing the jolt transmitted tothe body. Off-road, the system increases wheelarticulation by decoupling the left and right wheelsand using the motors to increase the compressionor extension of the suspension.

According to Bentley, 48 V architecture wasselected for the Dynamic Ride system because itallows more power and can much more quicklycontrol the ride and roll characteristics. Byconstantly monitoring the steering angle, theposition of each wheel and the lateral accelerationthe motors can react in as little as 0.06 seconds.

The vehicle’s main electrical system remains 12 V,while the componentry for the 48 V system ishoused in the rear underneath the spare wheel. Itconsists of a DC/DC converter which steps uppower from 12 V to 48 V, with the charge beingheld in a pair of super capacitors.

Bentley Bentayga

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The actuators and the electrical systems addapproximately 20kg to the weight of the Bentayga,but Bentley say this is a price worth paying for theincreased performance. The difference may not beexcessive in a large, heavy vehicle like theBentayga, but it is much more of a consideration insmaller passenger cars.

Developing 48 VTechnology

Audi SQ7Another member of the VW Group, Audi, has alsorecently introduced a vehicle with 48 Vtechnology, and it goes a stage further than theBentley system. The Audi SQ7 features a 48 Velectrical sub-system which controls theelectromechanical roll stabilization system(EAWS), and also powers an Electric PoweredCompressor (EPC) to eliminate turbo lag as thefirst turbo spools up.

The similarities between the SQ7 and the Bentaygashould be no surprise, since they are based on thesame MLB platform, but Audi’s use of an additionale-booster shows how 48 V technology can beutilized to dramatically improve performance.

The 48 V architecture is used to power the 7 kWelectric compressor to fill in the torque gap atlower engine speeds. A 0.5 kWh lithium-ion batteryis housed in the rear luggage compartment anddelivers a peak power output of up to 13 kW.A DC/DC converter provides the connection thevehicle’s main 12 V electrical system, which issupplied with 3 kW of power from an optimizedalternator.

The power-hungry EPC provides the necessaryboost in less than 250 milliseconds and spins at upto 70,000 rpm. This helps the SQ7’s twin-chargedV8 diesel engine produce 320 kW of power and900 Nm of torque.

The 2.3 tonne SUV can travel from 0-100 kph in 4.8seconds, and Audi has demonstrated itscapabilities with marketing ploys such as a fakedrag race with a fighter jet. The vehicle has beenwell received, and in May 2016 was rewarded asAutocar magazine’s Innovator of the Year for itssignificant contribution to future car technology.

While the e-charger has been all aboutdemonstrating increased power in this initialsetting, it is expected to be used to help meetefficiency and emission quotas as targets becomestricter. Audi says it can be used as a performancebooster and an efficiency gain. Fuel efficiency canbe improved by making the gear ratio longer, and inmost cases, as Audi rolls out similar systems, thereis expected to be a combination of performanceboosting and efficiency gains.

Both vehicles demonstrate the benefits of 48 Vtechnology, but it really is just the starting point asfar as the industry is concerned. Electronics supplierDelphi estimates that some 8 million vehicles with48 V architecture will be produced worldwide in2025, and it is emissions regulations that will leadthe charge. 48 V powertrain systems are estimatedto be able to provide 70% of a mild-hybrid’s fueleconomy at 30% of the cost to OEMs.

Earlier this year Delphi announced a 48 V vehiclesolution, which was showcased in a Honda Civic 1.6liter diesel car. The customized architecturemaximizes the use of 48 V electrification tominimize demand on the engine, improvingperformance while lowering CO2 emissions by up to10 %. Meanwhile, an e-charger increases low endtorque by up to 25 %. Delphi has confirmed that it isworking with two global automakers, andproduction could start as soon as within the next 18months.

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msSummaryADEPTIn other news, Daimler has recently revealed that itwill invest more than seven billion Euros in greentechnology in the next two years, including a 48 Von-board power supply system which will beintroduced in 2017. Meanwhile, reports in themedia suggest that VW is planning to release astand alone electric vehicle based on 48 Varchitecture that will have a range of 186 miles.This may be part of the manufacturer’s strategy tomove towards electrification in the aftermath ofthe diesel scandal, and the VW Group alreadydemonstrated its expertise through Audi andBentley.

Europe is likely to lead the way in 48 V mildhybrids, as emission targets come into force by2021, and the next few years promise a host of newconcepts and ideas, as 48 V technology becomesmainstream in series production cars.

Another research project that is nearingcompletion is the Ricardo-led ADEPT program,which has applied advanced mild hybridtechnologies with 48 V ‘intelligent electrification’to a Ford Focus demonstrator.

The project partners include Ford Motor Company,the Advanced Lead Acid Battery Consortium(ALABC), Control Power Technologies (CPT),Faurecia Emissions Control Technologies UK, andthe University of Nottingham. The final results ofthe project have been presented in September.

The aim of the project was to demonstrate anadvanced 48 V mild hybrid powertrainarchitecture, capable of delivering near full hybrid-scale diesel fuel efficiency and reduced CO2emissions. Key features of the vehicle includeCPT’s water-cooled SpeedStart switchedreluctance belt starter generator (BSG), capable ofdelivering in excess of 12 kW of regenerativebraking. Near instantaneous and near continuoustorque assist levels of over 7 kW enable significantengine down-speeding, and highly capable start-stop functionality. Further recovery is achieved viaCPT’s exhaust-mounted 48 V turbine integratedexhaust gas energy recovery system, known asTIGERS.

The ADEPT powertrain includes a range ofelectrical ancillaries powered from the 48 V systemrather than the engine, such as the vehicle airconditioning compressor. The 48 V architecturealso provides significant levels of torque assistfrom the BSG to offset fueling to the engine forimproved fuel efficiency, and to increase overallpowertrain torque capability for enhanced vehicleperformance.

Cover image © LaCozza - fotoliahttp://media.daimler.comhttp://www.ricardo.com/http://delphi.com/https://www.audi.co.uk/about-audi/latest-news/audi-sq7-tdi-is-autocars-innovator-of-the-year.htmlhttp://www.bentleymotors.com/en/models/bentayga/bentayga/model-features/performance.htmlhttps://www.bentleymedia.com/release/675

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