48V electronic architecture has been looming on the automotive horizon for a few years, and rapid growth is expected over the next five years as manufacturers strive to meet increasingly stringent CO2 emission targets. 48V mild hybrids are considered one of the most cost-effective ways of achieving the targets, which are set to be introduced in 2020 and expected to be further reduced in 2025 and 2030.
Another driver for this change is the more sophisticated electrical architecture found in today’s high-end vehicles. Electrical components in luxury cars are nearing the limit of a 12V power supply, and the step up to 48V is inevitable to support connectivity and advanced electrical functions and safety features. 48V power supply systems have not always been considered cost-effective for series production, but advancing technology and external pressure in terms of emission regulations, has brought development in this sector to the forefront of the industry.
The Latest Developments: Audi Biturbo
Audi recently showcased their latest development on the 48V front, by unveiling a new TT Clubsport Turbo Technology Concept Car at W÷rthersee in Austria, which features an electric biturbo supported by a 48V electrical subsystem. Prof. Dr. Ulrich Hackenberg of Audi’s board for technical development said, "The electric Biturbo signifies a new dimension in driving enjoyment; it boosts sprinting ability and torque and enables high peak power. In our TDI engines, we are close to production readiness with this technology".
Image: Audi
The Biturbo combines a conventional gas-driven turbocharger with a secondary electrically driven compressor. Without the need to rely on energy from the exhaust, the electrically-powered compressor offers several advantages: It revs up to maximum rpm rapidly, and continues to boost charge pressure when too little drive energy is left in the exhaust gas for the conventional turbocharger. The electrical system allows the concept vehicle to cover up to 16 metres over the first 2.5 seconds, which is six metres further than a comparable car without the technology. It also demonstrates Audi’s commitment to 48V technology.
The concept TT can produce 591hp with a 2.5 litre engine, while production cars from other manufacturers today can only achieve similar figures with roughly twice the displacement of the Audi.
Hyundai Tucson 48V Hybrid
Hyundai also showcased new 48V technology earlier this year at the Geneva Motor Show, with the unveiling of the new Tucson 48V Hybrid Concept. The 48V Hybrid combines a 2.0 litre diesel model with 134 hp (100KW) and a six-speed manual transmission along with a 14 hp (10KW) electric motor. Combined system performance is 148 hp (110KW), which boosts system power by 10% while only emitting 109g/km CO2. In comparison to a full hybrid model, the 48V system delivers similar efficiency for a quarter of the cost.
Image: Hyundai
The technology displayed in the show car consists of a Hybrid Starter Generator (HSG), inverter and a low voltage DC/DC converter. The HSG supports the diesel engine with additional output, enables the ISG to restart the engine with practically no noise or vibration, and acts as a generator during deceleration to recharge the 48V lithium-ion battery. In total the hybrid system adds just 20kg to the weight of the vehicle.
Lead-Carbon Batteries
Another interesting development has come in the form of Lead-Carbon Batteries, a technology which is being showcased by the Advanced Lead-Acid Battery Consortium (ALABC). In February this year the organisation displayed three hybrid vehicles as a result of R&D projects, two of which were produced in partnership with leading OEMs, Ford and Hyundai/Kia. The three vehicles were produced to demonstrate the real world potential of lead-carbon batteries in 48V architecture, and exhibit the potential for environmental and fuel efficiency improvements.
The 48V LC Superhybrid is a mild hybrid based on a gasoline-powered turbo-charged 1.4 TSI Volkswagen Passat, enhanced with a Valeo electric supercharger and a CPT Integrated Starter Generator (ISG). ALABC’s first 48V demonstration vehicle, the car showed a 13% reduction in CO2 emissions over the base car in initial testing, and also showed the potential for an extra 5% reduction over the NEDC cycle.
The 48V Kia Optima T-Hybrid was loosely based on the previous vehicle but features the Optima’s existing 1.7 litre CRDi turbo diesel engine, with a Valeo 10KW electric starter generator and electric supercharger, powered by a 48V version of East Penn’s lead-carbon UltraBattery. This powertrain concept enables the vehicle to be driven in electric-only mode when at low speeds and cruising, and recharges the battery during deceleration. It includes stop-start functionality, regenerative braking and enhanced torque and power at low speeds.
The ADEPT (Advanced Diesel Electric Powertrain) concept produced in partnership with Ford also improves on the technology from the first vehicle, with the aim of reducing current class-leading C-segment CO2 emissions by a further 15-20%. Based on a Ford Focus, the vehicle is projected to cut CO2 to 75g/km, and will indicate a pathway to 70g/km at a cost/emissions reduction ratio superior to that of a full hybrid vehicle.
ALABC has used these vehicles to demonstrate the potential of lead-carbon batteries as opposed to Lithium-ion batteries. They have several key advantages for use in hybrids due to their performance in high-rate partial state of charge operation, their ability to operate in sub-zero conditions, cost advantage over Lithium-ion batteries, high recycling rates, and the lack of need for a battery cooling system. The automotive industry continues to show an interest in the technology.
Legislation, Standardization and Industry Trends
Consumer demand is still low for electric vehicles, and these trends are certainly not customer-driven. The key driver behind 48V systems is the regulatory environment – particularly in Europe. The emissions goal for passenger cars is less than 95g/km CO2 after the year 2020. 48V hybrid vehicles are increasingly seen as the most cost-effective way of achieving those targets.
The EU also has plans to introduce Worldwide harmonized Light vehicles Test Procedures (WLTP) by 2017 or by 2020 at the very latest. The aim is to introduce global standards for determining the CO2 emissions, fuel consumptions and electric range of passenger vehicles. The WLTP will be more accurate that the current New European Drive Cycle (NEDC), and will present automakers with more challenges.
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For example, first generation stop-start systems typically command a 5% reduction in emissions under the NEDC tests, but new testing under the WLTP would only afford a 2.5% reduction for a similar system. It’s important for the industry then that electrical standards for 48V architecture can be agreed before the introduction of the new legislation; to that end, the big five German auto-manufacturers, Audi, BMW, Daimler, Porsche and Volkswagen proposed the LV148 standards, and are already taking steps to adopt them.
It is the regulations in Europe which means the continent will lead the way in 48V technology according to a Frost and Sullivan report, ‘The 48V Power-net Market in Europe and North America’. The report suggests that the Volkswagen group will lead the way in 48V automotive systems, predicting that the manufacturer will have 48V volumes in excess of 1 million across Europe and North America combined by 2025. The research consultancy predicts that Audi and PSA will lead the charge in Europe from 2017, and development in the USA will predominantly be led by German OEMs. The report also suggests that Europe will lead the way from 2020 through to 2025 due to stricter regulations, while the USA will lag slightly behind due to more lenient CO2 targets and a lack of American OEMs taking an interest in 48V architecture.
Growth in Asia
Other forecasts from Navigant Research predict a slow and steady uptake of the technology over the next five years to 2020, but a sharp rise in vehicles with 48V sub-systems at the start of the next decade, with sales predicted to reach 13.5 million vehicles worldwide by 2023. It’s notable that the research shows that the Asia Pacific region will account for approximately 60% of sales by 2023, and it is a market on the verge of sustained growth.
Japanese automakers continue to dominate the hybrid market, accounting for 85% of the global market in 2012, with the Toyota Prius leading the way. Demand is high in Japan, and companies such as Toyota and Hyundai are investing heavily in 48V systems with an eye on the Chinese market as well.
The Chinese automotive market is vast, but repeated attempts by the government to encourage the uptake of electric vehicles have fallen short of targets. When this market is opened up, sales of 48V hybrid vehicles in Asia could easily outstrip Europe and the USA.
The Chinese government expects fuel usage to decrease and the share of non-fossil fuels to increase by 11.4% in 2015 and 15% in 2020. CO2 reduction targets are 17% per unit GDP. It has also put in place a number of incentives for the development of BEV and HEV technologies, with over 10,000 automotive companies receiving purchase subsidies, research and development incentives, and tax exemptions to help achieve the targets. One of the key barriers in China has been the lack of a charging infrastructure, but the government has determined to build a complex infrastructure to support electric vehicles by 2022, and once this is in place growth can be expected.
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