Future 4WD's - Mild Hybrids
Why Safiery has Invested in 48V Systems
Electric and hybrid vehicles are largely aimed at meeting the stringent CO2 emissions targets being implemented beyond 2020? The mild hybridization of conventional cars with 48V battery has emerged as the most viable answer to this challenge in the near term.
The current 12V electrical systems in conventional internal combustion automobiles are reaching their 3kW power limit due to the ever-increasing demand for more electrical devices such as powertrain control, infotainment, and advanced driver assistance systems (ADAS). A secondary subsidiary electrical system running at 48V can complement the traditional power supply by offering the advantages of hybridization without the complexity associated with electric and hybrid vehicles. The mild hybrids are not electric vehicles because the wheels are not driven electrically. They are also significantly cheaper and can be added to traditional powertrains relatively easily by car OEMs. They add torque to the the 4WD's.
Moreover, higher voltage translates into smaller cable cross-sections, which in turn makes powertrain architecture lighter and contributes a lot less power and torque than a high-voltage hybrid system. The plug-in hybrid electric vehicles operate at a voltage system higher than 60V.
Delphi Automotive, a tier one automotive supplier, claims that mild hybrids can offer nearly 70 percent of the benefit of a more traditional hybrid — like fuel efficiency and CO2 reduction — at about 30 percent of the cost.
Delphi asserts that the 48V battery system will cut emissions in common cars by 10 percent.
Dodge RAM's 48V eTorque mild-hybrid system delivers improved fuel efficiency for both 3.6-liter Pentastar V-6 upgrade and 5.7-liter HEMI V-8 configurations. The eTorque mild hybrid system replaces the traditional alternator on the engine with a belt-driven motor generator unit that performs several functions. The motor generator unit works with a 48-volt battery pack to enable quick and seamless start/stop function, short-duration torque addition to the engine crankshaft in certain driving situations and brake energy regeneration, which improves responsiveness and efficiency.
With the engine running, eTorque’s motor generator unit feeds 48-volt current to a 330 watt-hour lithium-ion Nickel Manganese Cobalt (NMC)-Graphite battery. The battery pack includes a 3-kilowatt Buck Boost DC-to-DC inverter to maintain the battery’s state of charge and convert 48 volts to 12 volts to power the Ram 1500’s accessories and charge its conventional 12-volt lead-acid battery.
BMW has announced that it will add a 48V mild-hybrid system to its 7th generation 5-Series with six cylinder engines.
Energy recuperation is enhanced only when the Driving Experience Control switch is set to Sport mode, and the system specifies gathers energy to powers the lights, steering, power windows, ventilation, audio system and seat heating, although stored energy can be fed back to the 48V starter-generator to provide an electric boost effect when the car is accelerating. Indeed, when the Driving Control is set to Sport, the XtraBoost feature offers an additional 40bhp for up to 10 seconds.
The Audi S6 and Bentley Bentagya both use 48V mild hybrid.
How 48V works
A dual 12V/48V system uses a low-voltage, conventional lead-acid battery and adds a 48V lithium-ion battery to it with a separate 48V network. The 48V mild-hybrid system comprises of a lithium-ion storage battery, a Buck Boost DC/DC converter that integrates the 12V electrical system, controllers for the battery, and hybrid powertrain; and an electrically driven turbocharger.
The 48V electrical system doesn’t replace the car’s standard 12V electrical system; instead, it’s connected to the 12V system via a Buck Boost DC/DC converter. That’s because accessories in conventional cars have been designed to run on a 12V system. The mild hybrids working at 48V battery only run a portion of the vehicle’s electrical system.
The initial 48V systems are mostly being designed around the powertrain, which leaves the rest of the electrically driven components to continue to operate on a 12V electrical architecture and conventional lead-acid battery. However, once that dual-voltage system is in place, carmakers can start moving more electrical components onto the 48V system.
Future electric driven devices which need the power of 48V systems include electric super chargers and electric anti-roll systems.
The 12V network will mostly likely continue to handle traditional loads like lighting, ignition, entertainment, audio systems, and electronic modules. On the other hand, the 48V network will support devices such as active chassis systems, air conditioning compressors, and regenerative braking.