Picture caption: The
Advanced Diesel-Electric Powertrain project known as ADEPT, is a
ground-breaking 48V mild hybrid under development by some of the UK's leading
automotive technology companies and academia, led by Ricardo and Ford joined by
CPT, EALABC, Faurecia and the University of Nottingham. Phil Williams (far right) chief engineer for
control and integration at Ricardo discusses the technology with delegates
attending the 2nd International Conference on Advanced Automotive 48V Power
Supply Systems in Düsseldorf.
Controlled Power Technologies (CPT), a major sponsor of the
recent 48V hybrid vehicle conference in Germany, together with leading car
makers and tier 1 suppliers, discussed the need for an internationally agreed
48V electrical standard. This is required by the global automotive industry to
achieve the economies of scale demanded by original equipment manufacturers. Organised
by IQPC Automotive, the 2nd International Conference on Advanced Automotive 48V
Power Supply Systems was held in Düsseldorf in Germany from November 18-20, November
CPT, together with
other sponsors, including AVL and Ricardo, is in the vanguard of 48V mild
hybrid developments being driven by ever tightening European CO2 regulations
and potentially a new and more aggressive test cycle.
According to a press release, keynote speaker Florian Kühnlenz,
responsible for series development of low voltage energy systems at Volkswagen
AG, set the scene with a presentation of the electric and electronic
architecture requirements of dual voltage power supplies in vehicles at 12
volts and 48 volts; with initial steps already having been taken for the
adoption of the proposed LV148 standard suggested by Audi, BMW, Daimler,
Porsche and Volkswagen.
Kühnlenz’ outlook is that the introduction of a second
voltage at 48 volts addresses new challenges for automotive electrical and
electronic systems, but that most issues have now been identified with
preliminary solutions already developed for introduction during the ramp up to
the 95g/km CO2 requirement by 2020. The
displacement of high wattage loads to a more efficient 48 volt network is
expected to be the next step in the development of a new generation of low
voltage mild hybrid vehicles.
“Other global carmakers will have to decide whether they
want to embrace 48 volts,” says Paul Bloore, product validation manager for
CPT’s hybrid product group. Commenting
on the need expressed by tier 1 suppliers for an international standard when
introducing low voltage hybrids and their note of caution should this not
happen, he added that “it makes sense to have a common global standard, because
48V hybrids are currently the most cost-effective way of meeting stringent CO2
emissions being introduced in 2020, compounded potentially by a shift from the
current NEDC test to the more aggressive WLTP test, with further 25 per cent
reductions anticipated in 2025 and 2030.
Moreover, a consensus of global forecasts suggests that 48V hybrids will
soon come to dominate the market, so clearly that’s what the vehicle
manufacturers are expecting to happen. A
common international 48V standard would be a smart move.”
Dr Salah Benhassine, a specialist in electromagnetic
compatibility (EMC) at PSA Peugeot Citroën, set out the French carmaker’s
approach to 48V mild hybridisation by focusing on one of the specific technical
challenges. He similarly concluded that
collaboration between automotive industry and suppliers is essential.
Robert Eriksson, senior technical leader for electric
propulsion architecture at Volvo Cars, concluded that there were several
opportunities for building scalable and modular solutions with different
attributes in the mild hybrid category, commenting on the recuperation
possibilities with expanded 48V architecture, thereby achieving the goal of
less than 95g/km of CO2 levels after 2020.
Ulf Stenzel, lead engineer for new battery technologies,
hybrid and electric powertrain systems at AVL Schrick GmbH, which is heavily
involved with CPT and the European Advanced Lead-Acid Battery Consortium
(EALABC) in the development of the ‘LC Super Hybrid’ gasoline powertrain,
discussed the development by Hyundai and Kia of a 48V mild hybrid diesel
powertrain, commenting that its combination with an electric supercharger
offered ‘realistic potential in terms of performance increase and further fuel
CPT’s contribution to the debate is as an independent,
clean-tech company, based in the UK, Germany and USA. CPT specialises in the development of
cost-effective CO2 reduction measures for the global automotive industry that
avoid the high cost of a major redesign of the powertrain – as currently
observed with high voltage hybrids and battery electric vehicles. Its core competencies include low voltage
power electronics, advanced control software and the application of low voltage
electrical machines to gasoline and diesel engines.
The three day conference revealed technological advances
being achieved by the European industry in the development of 48V mild hybrids,
providing CPT with the opportunity to discuss its ground-breaking development
and commercialisation of switched reluctance motor-generators for automotive
applications, with the numerous environmental benefits including the
elimination of rare earth permanent magnets from an electrical machine.
“It was appropriate at this conference to present the latest
details of our SpeedStart technology, because a belt-integrated starter
generator (B-ISG) is typically the first step towards 48V hybridisation,” said
Bloore. “CPT’s highly responsive B-ISG
helps to reduce the sensitivity to different real world driving styles and test
cycles of B-ISG based mild hybrids; especially as we move by 2020 if not
beforehand from the New European Drive Cycle (NEDC) to the Worldwide harmonized
Light vehicles Test Procedures (WLTP).”
The EU goal is to introduce the WLTP by 2017 if possible and
no later than 2020 to coincide with the 95g/km requirement. The WLTP defines a global harmonised standard
for determining the levels of pollutants and CO2 emissions, fuel or energy
consumption, and electric range from passenger cars and light-duty commercial
vehicles – therefore it becomes even more important for the industry to agree
beforehand a global electrical standard for the 48V mild hybridisation of its
One of the issues for the industry to confront in moving away
from the NEDC test is that the WLTP typically halves the measurement of CO2
reduction gained from first generation stop-start systems, which
characteristically reduce CO2 emissions on the NEDC by 5 per cent. This reduces to 2.5 per cent when measuring
the same vehicle on the WLTP.
“The WLTP cycle will be much more challenging than the NEDC
and the CO2 effect of a simple stop-start system will be halved,” says
Bloore. “Car makers will have to further
optimise their control system strategy, which can be aided by a B-ISG with a
fast transient response to maximise the recuperation and boosting potential
over the WLTP test cycle, or under real world driving conditions. Moreover, any electric boosting using energy recuperated,
rather than lost in friction from the brakes, not only reduces CO2 and NOX
emissions, but can also have a positive impact on vehicle performance and
“The WLTP is significantly more dynamic with faster
acceleration rates,” adds Bloore. “This means that in addition the power demand
is more difficult to achieve with engine downsizing and transmission
Thermal management of the electrical machine is another
critical factor, because the duration of the boosting and energy recovery
operating modes directly impacts fuel economy and emissions. Hence the trend towards liquid cooling of
electrical machines, which can be achieved by tapping into the engine coolant
system, ensuring their performance including any integrated electronics is
independent of ambient temperature.
“Stable thermal characteristics achieved through liquid
cooling allows better utilisation of torque assist and longer recuperation
opportunities, since both modes generate heat,” says Bloore. “It is how we manage to deliver peak recuperation
in excess of 12kW and peak torque assist in excess of 8kW for extended
durations of typically 20 seconds or more.
The recuperation potential in the NEDC test cycle allows use of electric
assistance in accelerations up to 30km/h and potentially to provide torque
assist at other road speeds including during engine-off coasting.”
“The bottom line of course is that cost is the most critical
factor when setting out to achieve CO2 compliance, particularly in the high
volume sector of the market,” says Bloore.
“Until we have a really significant breakthrough with battery chemistry
or fuel-cell technology, the high voltage approach to hybridisation and pure
battery electric vehicles will remain too expensive for universal application
across high volume vehicle platforms.
“Low voltage hybridisation on the other hand, for a new
class of 48V hybrid vehicle, provides an affordable compromise between
efficiency and cost. And it’s
cost-effective because it’s an evolution of existing powertrain architecture
rather than a completely new propulsion system.”
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