Future Truck Committee Information Report: 2015-3

Issued: XXXXXXX Future Truck Committee Information Report: 2015-3

Exploring the Potential for 48-Volt Commercial Vehicle Electrical Systems

Changing the Electrical/Electronic Face of Trucking

Developed by the Technology & Maintenance Council’s (TMC) Future Truck Committee

ABSTRACT

Regulations for the reduction of greenhouse gases — such as carbon dioxide (CO2) emissions — are becoming more and more stringent, and manufacturers are faced with a difficult mission to meet these goals. The need for an affordable, fuel efficient alternative to existing hybrid vehicles is demanding. In the late 1990s, 42-volt electrical systems were rejected as uneconomical, but today, there is a clear trend towards the introduction of 48-volt systems to achieve the necessary emission targets.

Forty-eight volt electrical systems represent a great potential to save fuel and reduce greenhouse gas emissions. Idle stop-start technology can help save fuel while the vehicle is motionless, and torque assist can also be supplied to the engine for launch and low-speed momentary acceleration. Increased energy storage and recapture of brake energy is also possible through 48-volt electrical/electronic (E/E) technology, further improving on overall efficiency. In addition, there are other possibilities with the use of a 48-volt supply that would not be possible with a 12-volt battery in a heavy-duty vehicle (HDV), such as electronically controlled air-conditioning (A/C) compressors and fully electric power steering.

Since 2011, multiple manufacturers in the automotive industry have announced their intention to integrate 48-volt technology, and there has been a determined push by the trucking industry to follow the development and relevant technology suitable for 48-volts. Initially the systems are likely to be applied to and combined with a 12-volt battery to produce efficient hybrid-like HDVs while retaining the standard power supply, but in the near future we can expect trucks to be fitted with just a single power source providing a 48-volt supply.

Technology & Maintenance Council (TMC) 950 N. Glebe Road • Arlington, VA 22203 • Ph: (703) 838-1763 • FAX: (703) 838-1701 [email protected] • http://tmc.trucking.org

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—1 INTRODUCTION Meeting E/E Demands Before looking at the 48-volt electrical system, Brief History of Higher Voltage Systems it’s good to remember the fundamental reason The concept of a higher voltage for E/E systems why the 12-volt system was originally adopted was under discussion as much as 20 years about 60 years ago. The 6-volt system could ago, when industry explored the potential for no longer cope with the ever-increasing loads a 42-volt system (so named based on the and efficiencies required by the new genera- charging voltage of the system, not the storage tion of vehicles. Sixty years later, the industry voltage), and although the idea was brought to again faces a similar challenge in upgrading the market, the vehicle manufacturing landscape current net power to meet the demands of cur- has changed significantly since then. When rent and future developments in E/E systems higher voltages were first being considered, architecture. With the addition of an assortment the driving factors were primarily providing of high-power parasitic loads, electronic system additional creature comforts within the vehicle. controller(s) (ESC), global positioning system However, today there is a more pressing need (GPS) navigation and media center, engine for electric-driven features in vehicles, and a control module(s) (ECM), etc. Heavy-duty much broader base of powertrain and chas- vehicles currently demand about 5-10 kW of sis functions which could also benefit from a electrical power, and that’s without using any 48-volt supply. functions for the powertrain.

Despite the potential benefits, the 42-volt There is increasing concern over the price of system was ultimately unsuccessful due to diesel fuel and environmental pollution from its the high cost of components, changing ve- use. The federal government continues to pass hicle engineering priorities, and the lack of a increasingly stringent fuel economy and emis- real driving force for development. In today’s sions standards for the trucking industry. This market, the necessary components for imple- will force the development of new technology, mentation have become less expensive, the which will eventually replace mechanical sys- transformative technology has been upgraded tems with open-demand electrical systems. significantly, and the need to reduce greenhouse gas (GHG) emissions has become The reason for a 48-volt solution — and not increasingly important. 24, 36, or 60-volt systems — is the need to

Figure 1: Power Growth Demands

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—2 anticipate future technology and operational demands and the real concern for human physical harm associated with servicing higher voltage systems. Technology always advances exponentially. If the industry is ready to change the architecture of the entire trucking industry’s electrical system, increasing the allowed voltage to its maximum, safe potential is both practical and in best interest of original equipment manufacturers (OEMs). Such a move on Figure 2 a world-wide scale would uniformly advance automotive electronic technology and achieve efficiency and GHG emission standards for for the first time, a global truck design, since heavy-duty vehicles. both the Western European 24-volt system and the North American 12-volt system would Most HDVs are powered by diesel engines likely be superseded simultaneously. that, without pollution controls, can emit high levels of other pollutants that contribute to Challenges to Overcome global warming and local air pollution. For The development of 48-volt systems is very example, uncontrolled diesel vehicles produce much driven by the powertrain, and initial high levels of particulate matter, a fraction of designs must overcome the problem of extra which has a warming effect and nitrogen ox- components, particularly when used alongside ides which are an ingredient of ozone (also a standard 12-volt system. To comply with new known as smog), an important greenhouse vehicle standards, a 48-volt system would gas. These pollutants are associated with have to feature: a 48-volt battery, a 48-volt bronchitis, asthma, and other lung diseases, starter-generator, and an additional (direct and are responsible for millions of premature current) DC/DC converter; and it is important deaths worldwide. In 2013, the World Health to understand how the 48-volt and 12-volt Organization classified diesel exhaust as systems will interact with each other onboard carcinogenic to humans, based on evidence the host tractor and the trailer. of an increase in lung cancer after long-term exposure. It should be recognized, however, that a 48- volt supply with up to a 54-volt charging state Europe, Japan, the United States and other offers both potential benefits and drawbacks developed nations have adopted heavy-duty for other systems onboard the vehicle, such vehicle emission control standards requiring as the chassis and brake systems. the use of new technologies to reduce these pollutants almost to zero. Currently, Western REASONS FOR ADOPTION Europe uses EURO “Stage VI” emission regulations, equal to North America’s “Tier 4 Pollution Control Final” that regulates diesel engines rated 175 The steady growth in freight transport by truck - 750 HP by gram CO2 per ton-mile (gCO2/ presents a challenge to efforts at reducing ton-mi). Systems that are capable of achiev- hazardous air pollution and GHG emissions. ing decreased emissions, for example, include Though, most countries have fuel economy Stop-Start Vehicle (SSV) technology, Exhaust standards for passenger vehicles, as of 2011 Gases Recovery System (EGERS), and Ki- only Japan and the United States have set netic Energy Recovery System (KERS). These

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—3 advanced systems can produce greater CO2 battery Group 31 packs contain approximately reductions with a 48-volt supply and there are 400 Ampere-hours (Ah) if they are in good many other possibilities to meet the increasing condition and at 100 percent state of charge. demand for new inventions with E/E features in That’s an estimate of 4.8kW per hour. That a vehicle. Further reductions are on the horizon means if all hotel loads were able to operate and North America is following the movement without engine operation, for example, the bat- requiring engine and truck manufacturers to tery pack supporting those loads would lose its achieve targets of 15-25 percent less gCO2/ cranking amp potential for starting the engine ton-mile by fiscal year 2020. in less than one hour.

Parasitic and Hotel Load Losses One of the main goals for 48-volt E/E system is Every component that is running when it is providing an opportunity of electrifying engine- not required represents a parasitic load on driven accessories and adjusting the power the drivetrain and hence an unnecessary consumption of the new E/E components for consumer of fuel. Currently, DOT-regulated longer performance. Additional parasitic loads drivers are required to take 10 hours rest for from ESCs, ECMs, GPS, electronic logging de- every 14 hours of duty per federally mandated vices (ELDs), etc., make it increasingly difficult Hours of Service (HOS) regulations — down- not to look at higher voltage power sources time that requires a surprising amount of power for countering simple current draw technology for sleeper cab habitability and entertainment. during engine-off applications. Engine idling, which consumes about half to one gallon diesel per hour, is illegal in Califor- Fuel and Driver Economy Mandate nia but remains very routine for many drivers Fuel economy is on everyone’s mind these because cab habitability trumps regulations days — especially fleet owners — and there’s during extremes of weather. Diesel-burning no need to recount the financial benefits to auxiliary power units (APUs), driven by small increasing ton-mile per gallon performance one-cylinder auxiliary engines, are much more of diesel-powered vehicles. Emissions and efficient, but also are noisy and don’t provide fuel frugality has been an increasing concern adequate electrical power to prevent advanced for more than 10 years and since President technological batteries from being drained by Obama directed the National Highway Traffic an increasing array of electrical gadgets. Safety Administration (NHTSA) and the Envi- ronmental Protection Agency (EPA) to develop At idle during hotel load conditions, Class 8 and issue the next phase (“Phase 2”) of me- HDVs on average consume up to 5kW of power dium- and heavy-duty vehicle fuel efficiency from its 12-volt electrical system because of and GHG standards by March 2016, it has heating and air-conditioning, basic engine been even more rigorous. Under this timeline, electrical features, lighting, computer and the agencies are expected to issue a Notice communications, and appliances. Most four of Proposed Rulemaking (NPRM) by March 2015 and the second round of fuel efficiency standards will build on the first ever standards for medium- and heavy-duty vehicles (model years 2014 through 2018). See Table 1.

Adopting higher voltage E/E systems sooner, rather than later, would help anticipate future regulatory mandates for emissions and fuel Figure 3: Hotel Loads efficiency since embracing a more advanced

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—4 TABLE 1: NHTSA/EPA PHASE 2 FUEL EFFICIENCY STANDARDS EPA CO2 (gram/ton- mile) Standard Effective Model Year 2014 Light Heavy-Duty Medium Heavy- Heavy Heavy- Class 2b-5 Duty Class 6-7 Duty Class 8 CO2 Emissions 344 204 107

NHTSA Fuel Consumption (gallon per 1,000 ton-mile) Standard Effective 2014 Model Year Light Heavy-Duty Medium Heavy- Heavy Heavy- Class 2b-5 Duty Class 6-7 Duty Class 8 Fuel Consumption 33.8 20.0 10.5

electrical platform would make implementing and improve fuel efficiency beyond conven- incremental improvements easier for manu- tional efforts that have previously focused on facturers and end users. aftertreatment systems, such as the diesel particulate filter (DPF), diesel oxidation catalyst Adoption of 48-volt E/E systems may help (DOC), and selective catalytic reduction (SCR) industry transition into Phase 2 comfortably systems that use diesel exhaust fluid (DEF). with OEM-compatible technology improve- A higher voltage system could yield potential ments to reduce engine-stressed componentry, benefits such as reduced DPF “regen” opera- as with parasitic loads, and energy systems tions, extended DPF cleaning intervals, and with pollution control. A 48-volt solution would reduced DEF use. diversify industry efforts to control emissions

Figure 4: Carbon Footprint Reduction

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—5 48-VOLT ELECTRIC SYSTEM loads during driver on- and off-duty time and FEATURES AND APPLICATIONS sleeper berth time. Electric turbo-generator Engine components that rely on mechanical compounding (i.e., EGERS) and electrome- motion to operate and function have the op- chanical valve train (EVT) technology are also portunity to be electrically controlled without available opportunities that are enabled by placing added stress to the main powerplant. 48-volt E/E systems. This may permit lighter This would include components as the A/C and materials and fewer mechanical moving parts, air compressor, engine fan, alternator, coolant thus reducing component failure and preven- pump, and the power steering pump. The air tive maintenance procedures. braking system could become partially electric or have fully integrated electronic-controlled Each of these new electrical loads requires braking dependability. power in the range of several hundred watts or higher. Conversion of existing functions and Forty-eight volt solutions also enable regenera- features to electrical power offers valuable op- tive braking and integrated starter-generator portunities for vehicle performance benefits in (ISG) technology that make it both possible and such important areas as fuel economy, emis- practical to lower emissions and increase fuel sions, and driver comfort. Electronics provide a economy. Along with ISG technology are the potent means of adding engineered intelligence availabilities of SSV and the relief of parasitic to vehicle functions so that power is used only

TABLE 2: BENEFITS OF 48-VOLT ARCHITECTURE

Current Technology Benefits of 48 volt Architecture Electric power steering More power, improved fuel economy Electric brakes Redundant power supplies Power windows, locks, seats, power rear Reduced size and mass of motors; cargo doors more efficient operation Heated exhaust assembly treatment Lower emissions; quicker light-off time Heating, ventilation, air conditioning Greater efficiency; smaller/lighter blower motors and cooling fans units; flexible packaging Mobile multimedia More power available for video, mobile phones, navigation systems, audio amplifiers, fax machines Electric water pumps Improved efficiency; longer service life Selected engine management system Reduced size and mass; increased components (e.g. exhaust gas recircu- performance lation valves, ignition systems, control actuators) Fuel pumps Reduced size and mass Heated seats Faster heating, more efficient operation; increased power

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—6 TABLE 3: BENEFITS OF FUTURE TECHNOLOGY OPTIONS Future Technology Benefits Electric supercharging Higher engine efficiency Ride control systems Improve ride, handling and vehicle stability Brake by wire Improved vehicle packaging and vehicle performance Steer by wire Enhanced performance; improved packaging; improved passive and active safety Electromagnetic valve control Lower emissions; optimal power; indi- vidual cylinder control; lower cost Integrated starter/generator Faster starts; quicker charging; design flexibility; low noise and vibration; improved fuel economy when needed, or, on demand as a means of gine and cab as they would operate electroni- saving energy. An excellent example of this cally. A smaller inverter is located inside the approach is electric power steering. Today’s main inverter assembly, via ISG. This inverts conventional hydraulic power steering system a portion of the 48-volt battery DC power into uses an engine-powered, crank-driven pump alternating current (AC), which operates the to generate the necessary hydraulic pressure. A/C compressor. Since the engine is not al- This pump runs continuously, placing a con- ways running, the A/C compressor must still stant power drain on the engine. By converting be able to operate. Through the use of an the steering function from hydraulics to elec- electric inverter compressor (as opposed to a trics, power is applied only when the steering belt-driven unit), the compressor is driven by wheel is rotated, and then only in proportion an electric motor that’s built into the compres- to the amount of the rotation. sor housing and powered by AC voltage from the vehicle’s power supply system. Except Electronically Controlled A/C Systems for the portion that is actuated by the electric The A/C compressor and other pressure- motor, the basic construction and operation related components become very flexible for of this type of compressor is the same as a positioning and mounting throughout the en- scroll compressor.

The electric thermal expansion valve, as well as other regulating components, is controlled by an A/C ESC via a logic program that takes into consideration multiple factors (e.g., sensors, vent actuators, etc.) in order to control the A/C operation. Also, a new heating, ventilation, air-conditioning (HVAC) unit would replace the two separate units used today on most trucks Figure 5: Electronically Controlled with sleeper cabs — one in the dashboard and one under the sleeper cab bunk. The HVAC A/C Systems

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—7 system would combine everything into one Engine Temperature Control assembled, charged, and sealed module that The mechanical fan and coolant pump could eliminates multiple parts and improves vehicle be generally driven directly by the engine via serviceability, which contributes to lower main- a pulley arrangement. This means that cooling tenance costs. air flow and coolant fluid flow would be a function of engine RPM only. Presently, there is no E/E Pneumatics control over the way these components oper- The air compressor is one of the heaviest ate. This leads to over-cooling of the engine crank-driven auxiliary loads that is applied to the during the warm-up phase and under-cooling internal combustion engine (ICE). Its availabil- of the engine during city driving conditions in ity to be operated electronically would reduce which there is no control over the operation friction on the engine load tremendously. This of the bypass valve (thermostat). An electroni- could be possible with 48-volt E/E systems cally controlled system varies coolant pump through an electronically controlled braking speeds based on engine requirements and system (ECBS). With ECBS, actuation of the operating conditions. An Advanced Thermal pneumatic brakes is done through electronic Management System (ATMS) has the poten- messaging and active computer control (i.e., tial to increase the life of the vehicle’s engine ESC), but the motive force for stopping and and cooling system components as well as parking remains air pressure. This would decrease fuel consumption and carbon emis- eliminate oil and excessive moisture build-up sions. Whereas a fullly electric cooling system in the air system that is a current issue with is not viable for a vehicle with a low-voltage failed components and weather related freez- electric system, it can be applied to a vehicle ing conditions. equipped with a 48-volt E/E system.

The air supply and storage can be custom- In the last decade, research has shown the ized to OEM chassis including smaller air benefits of increased electrification and control tanks, fewer pressure regulators, smaller air in the thermal management system. This is drier, as well as allow pressure-on-demand because ATMS allows a reduction of thermal per driver response rate. ECBS also allows transients in the coolant system compared to CAN J1939 (controller area network) to be the on/off switching of thermal components. interconnected with ABS and ISG for optimum The high electrical load that an ATMS will performance during extreme braking conditions place on the vehicle’s electrical system makes and deceleration of the vehicle without brake it more suited to a mild or micro hybrid vehicle pad wear. With ECBS, brake actuation time where the system voltage is 48-volts or higher. is significantly reduced and costly plumbing By removing the mechanical load from the in the HDV is reduced. vehicle drive train and replacing it with con- trollable, high efficiency electric components, the auxiliary load reduction imposed by the

Figure 6: E/E Pneumatics Fig. 7: Engine Temperature Control

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—8 cooling system can be significantly reduced. the ISG can be used to further augment energy Instead of one large mechanical engine fan, efficiency through electro-dynamic braking, it is anticipated for several smaller fans driven also known as KERS. independently by brushless DC motors. The thermostat valve is replaced by an electroni- Electromechanical Valve Train cally controlled valve and the mechanical In a camless engine, electromechanical actua- coolant pump is replaced by an electric one. tors — a set of electromagnets placed directly Control of all the components is implemented on the valves — replace the camshaft. This over the standard SAE J1939 CAN network. technology makes it possible to optimize the The performance of the pump is limited by circulation of gases in the engine, both for the current that can be accommodated in the intake and exhaust, and to deploy operating machine. To achieve a higher pumping power, modes that improve fuel consumption, clean a higher voltage is required. exhaust technology and performance. EVT has long been under study and never executed to Exhaust Gases Energy Recovery System its full potential within limitations of the power EGERS is a water-cooled, switched reluc- needed to operate. tance generator coupled to an exhaust-driven turbine. It is capable of operating in exhaust Over time, the valve train in a conventional die- temperatures greater than 900ºC, at speeds sel engine wears and, if not serviced correctly over 80,000 rpm, delivering a high shaft power according to OEM-specified intervals, severe equal to or greater than the needed 48-volt engine wear and damages will occur. EVT pro- charging power. It is designed to recover and vides multiple solutions to countless wearable recycle exhaust gas energy, this technology components resulting in vehicle downtime for represents a promising means of achieving major repairs. Electromechanical actuators, significant increases in power and efficiency commanded by an ECM, control the movement for 48-volt HDVs. of the valves. There is, therefore, no longer any direct mechanical bond between the valves and With electric turbo-compounding, a high-speed the crankshaft, decreasing more stress on the motor-generator is added to the turbocharger engine and increasing horsepower to focus rotating group. In this way, recovered exhaust on engine performance. Computer controlled energy (heat) not used by the turbine to boost opening and closing of the valves make it pos- engine compression is converted to electricity, sible to improve the various phases of engine which can be stored in the 48-volt battery sup- running. During urban driving and on the open ply or ISG. When needed, this power can be road, both adequate opening and timing of the used to meet electrical demands or routed to valves make it possible to admit a quantity of the ISG to increase engine output. Conversely,

Figure 8: Recovery System Fig. 9: Electromechanical Valve Train

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—9 air limited to the requirements of the engine extension of engine stop phases by using mixed with a mass of burned gases purposely recovered energy from the E/E power supply retained in the engine. This strategy could system. Braking energy recovery systems have replace the exhaust gas recirculation (EGR) been in use for some time now through hybrid circuit and ensure reduction of fuel consump- automotive and trucking technology and it will tion and polluting exhaust emissions. be going forward the standard for achieving zero emissions and better fuel economy.

CO2 Reductions by Regenerative Braking Truck emissions are a contributor to poor air Regenerative braking systems recapture quality, but all-electric heavy truck drivetrains some of the vehicle’s kinetic energy when the seem unlikely for a long time. Even so, electric brakes are applied and store this energy so assist could improve performance while reduc- that it can be used to reduce the engine load ing fuel consumption. Heavy trucks waste a lot when the vehicle accelerates. It is widely used of fuel climbing hills, braking down hills, and in in electric vehicles (EV) and hybrid electric stop and go traffic. Even large diesel engines vehicles (HEV) that already have batteries burn a lot of fuel pulling a load to build mo- to store the recaptured energy. Regenerative mentum from a dead stop, and current engine braking has minimal impact on fuel economy braking and air brakes waste vast amounts of during highway driving, but it can significantly energy during deceleration, especially down improve the fuel economy of vehicles that are hills. In addition, the need for driver cab and driven primarily in city traffic. In HDVs that bunk power during down time when the truck make frequent stops (e.g., garbage trucks), is stopped unnecessarily uses fuel either by regenerative braking systems can improve truck engine idling or by an auxiliary motor. fuel economy substantially.

Through E/E system innovation, 48 volts can Regenerative Braking Alternatives provide regenerative braking, E-boost assist, EVs and HEVs typically employ motor-gen- and emission-free “sailing” effects with the erators that can convert electric current into

Figure 10: Regenerative Braking

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—10 Figure 11: Hybrid Hydraulic Alternative torque (like a motor) or torque into electric pressure is used to aid in acceleration. Another current (like a generator). When the brakes means of mechanically recapturing braking are applied, the motor-generator provides the energy is the use of a flywheel, commonly resistance necessary to slow the vehicle as it referred to as KERS. The energy is conserved supplies current to the battery. In the event that in the form of a rotating mass and is therefore the motor-generator cannot slow the vehicle efficient, as there is no electromechanical con- fast enough, a torque coordinator module will version. Both hydraulic and flywheel systems apply traditional friction brakes to the extent boast higher efficiency than electric battery necessary. Regenerative braking has certain storage systems, but are primarily implemented limitations. In emergency braking situations, only in commercial vehicles due to their size regenerative systems can neither provide the and noise of operation. These systems still necessary stopping power nor handle the require a significant amount of electronics to amount of electricity generated from a maxi- regulate the energy transfer and to apply the mum deceleration stop. Regenerative brakes friction brakes as needed. also lose their stopping power and efficiency at lower speeds. A mild form of regenerative braking can be achieved in non-electric vehicles by adding a Some regenerative braking systems store the clutch to the alternator. The clutch engages recaptured energy mechanically, typically by when the vehicle is coasting or braking caus- pumping hydraulic fluid into an accumulator ing the alternator to help slow the engine as where the energy is stored in a compressed it charges the battery that powers the starter gas. When the accelerator pedal is pressed, motor and other electric devices in the vehicle. the direction of fluid flow is reversed, and the This type of regenerative braking is relatively

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—11 to do so as well through its inverter during most non-driving phases. The 48-volt battery pack has enough power to supply energy to the A/C compressor to keep the cabin cool (even with the engine is off) and still have enough power to propel the vehicle down the road at low speeds for a limited Figure 12: Integrated Starter-Generator distance. inexpensive and easy to implement in existing vehicles. 48-VOLT /12-VOLT (‘HYBRID’) Integrated Starter-Generator SYSTEM APPROACH The ISG is the micro- and mild-HEV propulsion Mild and micro hybrid vehicle technologies system that improves fuel economy and emis- are the two design directions that the truck- sions with potential coasting (“sailing”) effects ing industry would likely consider if 48-volt is it induces to the engine for engine-off driving implemented to solve its emission control is- capabilities. The ISG configuration is attractive sues. Hybridized diesel engines using 48-volt would benefit from lower nitrous oxide (NO ), because one electric machine can be used x CO , and particulate matter (PM) emissions. to propel the vehicle, to start the engine, and 2 to function as a generator. The performance, Not only do these designs overcome techni- efficiency and peak torque characteristics cal and organizational challenges, they also of the motor-generator is possible through create an overall system design as the basics switched reluctance motor-generator technol- for 48-volt requirements of components. Using ogy. It is widely used in HEV design between one of the two approaches is also an essential the transmission and engine and is positioned way of designing the maximum efficiency of with an auto-clutch design on the same shaft a 48-volt vehicle electrical system, via micro- as the electric motor and the transmission. The mild HEV. auto-clutch is used to connect/disconnect the engine from the powertrain. The vehicle can Mild HEV be propelled by the engine, the electric motor, Mild HEV uses the engine for primary power, or both at the same time. The electric motor with a torque-boosting electric motor (i.e., ISG) and the 48-volt battery are sized to meet the connected in parallel to a largely conventional maximum power required in the EV mode, if powertrain. EV mode is only possible for a very applicable. limited period of time, and this is not a standard mode. Compared to full HEV, the amount of Since the AC produced by the ISG can’t be electrical power needed is smaller, thus the stored in a DC battery, the generator’s second size of the battery system can be reduced. The job is to rectify AC to DC, in order to recharge electric motor-generator, mounted between the the 48-volt battery. Also inside the ISG is an engine and transmission, is essentially a very additional three-phase AC inverter for the elec- large starter-motor, which operates not only tric A/C compressor used for the electronically when the engine needs to be turned over, but controlled A/C system. The ISG supplies AC also when the driver accelerates and requires voltage for the A/C compressor during most extra power. The electric motor may also be driving phases and allows the 48-volt battery used to re-start the ICE, deriving the same

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—12 Figure 13: Micro-Hybrid Technology benefits from shutting down the main engine continue to run on electrical power while the at idle, while the enhanced battery system is engine is off. Furthermore, the lubrication used to power accessories. The electric motor systems of ICE’s are inherently least effective is a generator during regenerative braking. immediately after the engine starts; since it is upon startup that the majority of engine wear Micro HEV and SSV The micro HEV is essentially a vehicle with an oversized starter-motor; allowing the engine to be turned off whenever the car is coasting, braking, or stopped, yet restarted quickly and cleanly. This is also the definition of a start-stop vehicle. During restart, the larger motor is used to spin up the engine to operating rpm speeds before injecting any fuel. As in other hybrid designs, the motor is used for regenerative braking to recapture energy. But there is no motor-assist and no EV mode at all.

Some provision must be made for accessories such as air conditioning which are normally driven by the engine. Those accessories can Figure 14: Micro-Hybrid Battery

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—13 occurs, the frequent starting and stopping of close to the cab. The 12-volt battery(s) would such systems reduce the lifespan of the en- stay located on the outside of the frame rail gine considerably. Also, start and stop cycles or behind the cab under the deck plate for may reduce the engine’s ability to operate at serviceability. Other battery technologies are its optimum temperature, thus reducing the in the works to compete with the up and com- engine’s efficiency. ing electrical driven automotive industry such as lead-carbon, lithium-polymer, and carbon 48-Volt Battery nanotube battery technology. Depending on The first component that is thought of ina the 48-volt method used, it could consist of a 48-volt electric vehicle system is the battery. 48-volt battery source and E/E system, one The battery or battery pack can be a single 48-volt battery source and one 12-volt battery 48-volt battery or four 12-volt batteries con- source with two E/E systems, or one 48/12- nected in series. Four Group 31 commercial volt battery source combination and two E/E 12-volt batteries connected in parallel is the systems. common battery pack in the average Class 7 and 8 heavy-duty vehicle today. Battery types Wiring Renovation range from valve regulated lead acid (VRLA), After batteries come wiring and the changes absorbed glass mat (AGM) type, and gel-cell are even more substantial thereafter. The type batteries all of which are “sealed” and 48-volt electrical system is being considered maintenance free. The 48-volt direction is in for many reasons, but most especially for its lithium-ion (Li-Ion) technology, which has had power output. The average 12-volt heavy-duty an impact in many consumer technologies E/E system powers around 5 to 8kW whereas today such as cell phones and electric hand the 48-volt E/E system could power around 20 tools. A single HDV 48-volt Li-Ion battery is to 30kW. Current and voltage are proportional larger than one Group 31 style battery but to equal high power outputs; therefore, cur- smaller and lighter than four AGM type bat- rent may be decreased to formulate correct teries connected together. amounts of power needed in the electrical system. Lower current allows the wiring sys- The 48-volt battery compartment, otherwise tem to be much lighter-duty than the wiring known as the power electronic carrier (PEC), systems today allowing reduced cost on rare would consist of the Li-Ion battery(s) and bat- earth metals, fewer routing complications, and tery controller(s) and would be located on the weight restriction relief. inside rail of the frame usually underneath or

Figure 15: Cable Thickness vs. Maximum Power

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—14 There are many different types of wiring in a to a vehicle speed that the ISG can’t comply heavy-duty vehicle, ranging from those that with, the auto-clutch turns the engine over for transmit signals from switches or sensors and operational speeds. carry almost no current to those that provide power to large electric motors and carry lots The 48-volt battery is charged by the ISG, of current. The amount of current that a wire regenerative braking and EGERS technology. can handle depends on its length, composi- Forty-eight volts is the voltage power for the tion, size, and how it is bundled. A 12-volt, 12 A/C system and blower motors, except for the American Wire Gauge (AWG) wire, typical for HVAC controls as well as all cab related electri- head lights, can become as small as 28 gauge cal functions (e.g., power windows and mirrors, size AWG with 48 volts. The wiring, connectors, interior lighting, media center, etc.) which stay and fuses decrease in size by more than half, at 12 volts. Additional DC/DC converters are staying in consistency with power and current applied where and when necessary for parasitic to all electrical functions. and hotel load conditions.

48-Volt /12-Volt System Design The air compressor as well as ECBS is also OEM specifications will dictate the design and powered by the 48-volt E/E system but the ABS E/E architecture for any proposed change. The system will stay 12-volts. Other than trailers, 48-volt /12-volt system design replicates the all exterior lighting will be 48 volt as well as already configured automotive plan and exist- all previous mentioned engine auxiliary loads ing heavy-duty parallel HEV. It would consist of (e.g., coolant pump, power steering, etc.). the micro-mild HEV platform (ISG design) with All 48-volt wiring and componentry will be the Li-Ion 48-volt PEC containing the 48-volt separated schematically from 12-volt systems /12-volt DC/DC converter. Like a hybrid, the and secured safely by element dimension ISG starts the engine only when the 48-volt bat- except DC/DC converters. All related ECMs tery decreases to a specified charge amount, and ESCs will be powered by their appointed depleted during driver start-up and amount electronic function voltage levels and be de- of accessories used. Then, before increasing signed without confusion thereof. Also, the

Figure 16: 48-Volt/12-Volt System Design

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—15 EVT would be powered by the higher voltage ture being considered for heavy-duty vehicles system for ample delivery of power to operate is the same design that is used in the heavy- the strong electromagnetic actuators variable duty hybrid parallel powertrain. Modern hybrid valve timing. HDVs and 48-volt systems are very similar due to the fact that both have 12-volt systems BARRIERS TO ADOPTION and both are being developed for the same Development of the 48-volt system is very much reasons of adoption (emissions, fuel economy, driven by the powertrain, and initial designs etc.). Therefore, both systems use the same must overcome the problem of extra com- technology. Forty-eight volt technology offers ponents, particularly when used alongside a HEV-like features, which is the reason why standard 12-volt system. The increased space mild or micro HEV is so named for 48-volt sys- requirements and isolated system manage- tems. The SSV costs are much less expensive ment for the dual system become barriers to while providing functions on the engine to be adoption. Among the additional components removed and made more resourceful reducing will be a 48-volt battery, a 48-volt starter- loads on the engine which induce stress and generator and additional DC/DC converters takes away horsepower (also kW). just to name a few, and it is important to understand how the 48-volt and 12-volt systems The dual voltage system requires space and will interact with each other. isolation of components that is new for its environment in a mobile habitat. New E/E com- Dual Voltage System ponents and existing technologies are going The most efficient dual voltage system architec- to need to be mounted and secured in specific locations throughout the chassis for operation

Figure 17: Dual Voltage System

Identification by color code, like high voltage componentry in HEVs is identified by the color orange, will have to be modeled and mandated by OEMs. Blue was the color that was in con- junction with the 42-volt E/E system when that was in the works 20 years ago. Existing components like the automatic transmission or transmission clutch combination will need to be redesigned to fit such 48-volt mechanisms like an ISG, extra wiring and connections, and hybrid control module(s) (HCM). The service- Figure 18 ability and access to these and other certain parts have to be designed for technician pro- tions and below 54-volts before overvoltage vision also. wear is impacted on the loads. Important limits are below 24 volts for under voltage, above 54 48-Volt Limitations volts for over voltage, and 60 volts or above for The base architecture, depending on the focus shock protection voltage. In addition, Chart LV of the OEM in CO2 reduction or performance 148 provides some properties where require- enhancement, involves the unchanged 12- ments can be derived from, as: volt E/E system, which is powered by a DC/ • Electrical shock protection is not required DC converter in the power class of 5 kW, for DC voltage < 60-volts [No high volt- and the portion of the 48-volt system in the age interlock system (HVIL) is required to power range of 20 kW for energy generation, protect humans against electrical shock] acceleration support and recuperation plus a (e.g., heavy-duty connections.) storage device. Electrical propulsion in HEVs • A single malfunction must not lead to a operate on a high voltage level between 150- short circuit between 48-volt and 12-volt volts and 650-volts. At this voltage level a high E/E systems. Such a short circuit between effort for protection against electrical shock is the voltage levels without connection to legally required. For this reason, it is planned ground might destroy the complete 12- to supply high power functions on the 48-volt volt system due to permanent overvolt- level in heavy-duty vehicles the same. Currently age. the only official specifying document for 48V is • There is a common ground (chassis) with “Chart LV 148,” issued by German OEMs (see potential for both 12-volt and 48-volt, Figure 18). Chart LV 148 specifies all the volt- which is connected by spatially divided age levels of a 48-volt E/E system. The usual wires and ground terminals. Loss of com- operation range is between 36- and 52-volts mon ground might lead to reverse voltage where a 48-volt system is at nominal operat- on the 12-volt side and thus destruction ing range. Following are areas with functional of 12-volt electronics. restrictions for lower operating range, between • No component may lead to a transition 36 and 24 volts, and upper voltage operating into the overvoltage level (54-volt) due range, between 52 and 54 volts. Just as the to load dump or resonance step-up. This charging limits of a 12-volt system may reach is a very important statement, as this up to 14-volts, the 48-volt system can charge at requires special measures at inductive a maximum 52-volts without functional restric- loads and limits the effects of arcing.

With these facts from Chart LV 148 and lines as a result of conducted electrical tran- regulations from International Electrotechnical sients. Electrical disturbances generated by Commission (IEC) 60038 and United Nations disconnecting inductive loads, sudden power Economic Commission for Europe (ECE) cutoff in the main circuit, or switch bouncing are R-100 to enforce its content, it can be derived commonly referred to as inductive switching. that no electrical shock protection is required Disconnecting an inductive element causes or any voltage below 60 volt can be treated as a high inverted overvoltage on its terminals. 12 volts. But there are some effects at higher Positive high voltage transients may occur at voltages such as 48 volts which might require the supply lines after the ignition key cuts the additional system protection measures for battery-supply circuit. In this case, the ignition technical reasons. circuit continues to release disturbances until the engine stops rotating. One critical effect is arcing. If arcing occurs, the surrounding materials might be set on fire Fast input transients can present a serious due to the high temperatures. Wiring smaller problem for 48-volt devices due to low dynamic than 12 AWG has a greater chance of being impedance of the components themselves. pinched, cut, pulled apart, and worn through The driver circuitry must provide very fast input due to normal driving conditions. Such wear supply rejection to protect the devices from and tear conditions raise the point of arching, high peak currents that could be potentially creating heat, and produce electromagnetic destructive. Both the power topology and the interference (EMI) with which the industry is control scheme of the 48-volt drivers must be not familiar. Wiring not only carries current carefully selected in order to ensure reliable to some components but also conducts heat operation of the devices. In addition, dual volt- away from connections and provides the cir- age devices are expected to survive continuous cuit’s physical integrity. Other serious failures application of +24 V/-12 V (12-volt systems) or by many constituent problems involve short to +96 V/-48 V (48-volt systems) during a jumper ground, loss of common ground, voltage short start. Garages and emergency road services circuit, and broken wiring. have been known to utilize 24-volt sources for emergency starts, and there are even re- Truck Transient Conditions ports of 36-volts being used for this purpose. Under normal vehicle operation, voltage at Higher voltages such as this are applied for the supply lines range between 9 and 16 volts up to five minutes and sometimes with reverse (12-volt system), or between 36 and 60 volts polarity. Thus, HDV 48-volt driver devices are (48-volt system). However, a substantially required to: wider range of voltages of both positive and • operate from a wide input-supply voltage negative polarity may appear along the supply range.

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—18 • provide immunity to input voltage tran- promote corrosion. On a rainy day, there are sients. few places where the wiring system will not get • include protection from input overvoltage wet. Water has the potential to cause shorting and undervoltage conditions. between adjacent conductors or initiate cor- • include input reverse polarity protec- rosion processes due to the presence of very tion. small amounts of salt, wash agents or other dissolved materials. Forty-eight volt systems Recent advances in higher voltage systems more than quadruple the rate of corrosion open new horizons in trucking applications. activity in a worn or open connection, as well However, optimal solutions for driving 48- as the potential for arcing damage. volts in the trucking environment are needed. Immunity to conducted transient emissions is Corroded connections will frequently occur one of the key requirements that must be ad- at regenerative braking components and dressed by OEMs. The right choice of a power depending where DC/DC converters, motor- topology and a control scheme for the 48-volt generators, and ECMs are placed, will uncondi- driver circuit becomes critical for meeting these tionally corrode because of moisture and road requirements. chemicals. The entire higher voltage system will have to have a solid connectivity eminence Corrosion Control to it and an extra casing or wrapping of each Corrosion prevention has always been a prob- component for additional corrosive resistant lem in the electrical system for the trucking support. Insulated surroundings would have industry. Commercial vehicles drive to some to be implemented throughout the system for of the most exotic areas on earth and back, anti-arching and fire prevention (i.e., HVIL). and anti-icing and deicing chemicals build up No longer could electrical tape or easy butt- under the chassis and on every component connectors be used to repair wiring in a 48-volt possible. There has been little work done on system. Wiring harnesses may have to be the effects of a 48-volt system in a truck and replaced entirely and connections from part-to- what potential corrosive damages can prompt part would have manufacturer specifications on new failure modes. Particular geographic areas how to properly maintain contacts. These type of concern include the northern hemisphere of barriers will have a heavy impact on service and Pacific and Atlantic coastlines. All of providers and either will burden the trucking these are exposed to saltwater and chemical industry or encourage new countermeasures environments during the year which tend to to come about.

Figure 20: Potential Damage Caused by Corrosion

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—19 48-Volt Precautions emit a more intense lighting effect for clearance, To work successfully with the new higher marker, turn signal, and head light proportions. voltage, fuses and circuit breakers must be OEMs are attracted by the potential reduction redesigned to avoid harness fires. Alternators in energy consumption as well as the space will need enclosed interior and exterior con- savings realized by smaller lighting fixtures. nections to avoid corrosion induced failures. High-brightness LEDs offer substantial benefits Connectors will have to be redesigned to make in truck lighting applications, but they require unfailingly tight connections, as those that are power conversion that can function over a wide loose will quickly burn open. This requires a range of input and output voltage and provide complete redesign of the electrical system and immunity to electrical transients. will provide solutions to the heavy-duty electrical system that have not been available for the 12- TO 48-VOLT GAPS problems in 12-volt E/E systems. Trailers, on Standardization is an essential part of develop- the other hand, are an entirely different mat- ing componentry for a higher voltage system. ter when discussing dual and higher voltage The battery industry is well organized through constraints. Lighting and brake systems would IEC and Society of Automotive Engineers be easiest to stay at 12-volts, omitting the (SAE), which should enable future battery de- combination vehicle issue and keeping higher signs specific to 48-volt systems that regulate voltage where it is needed — at the engine. its terms of use. When developing standards This will allow the J560 seven-pin electrical for EV programs, the automotive industry connector to stay the same or be improved discovered that safety considerations were only by new higher voltage contingencies. necessary for the manufacturer, the occupant, the rescue crews, and technicians in the field. Direct 12-volt system or DC/DC converter It is essential that special training programs from a 48-volt system will supply the trailer be developed for each of these stakeholders, with lighting, ABS, and possible liftgate opera- particularly those that are the least expecting. tions. If 48 volts were to be connected to the The 48-volt system provides enough voltage trailer, the seven-pin connector will no longer in some cases that will involve shock hazard; tolerate wear and spray incursion. It would even though research indicates that risk is low, have to be tight and secure by new means of it still remains. connect/disconnect or it will either weld itself shut or burn up if connected and disconnected Dual Voltage Dare improperly. Also, all lights will have to be long- Before 48-volt systems can be adopted lasting light-emitting diodes (LEDs) which isn’t widely, many engineering problems must be an issue since that’s the movement towards addressed, including the engine/electrical exterior lighting as it is. LEDs eliminate shock system architecture and a migration strategy impact and water intrusion damage as well as (dual 12/48-volt systems vs. straight 48-volt systems). Short-term challenges associated with dual voltage systems include more wiring, extra weight, and added complexity. Regard- less of migration path, suppliers need time to develop new components and a part identification system that distinguishes between 12-volt and 48-volt parts.

Figure 21: Dual-Volage Connection

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—20 Evaluation of Electrical and Electronic Component and Conductor Arcing Components Relay, switch, and conductor arcing is another While 48 volts is not far from 12 volts in physi- problem that must be addressed. Its potential cal terms, real world issues are a cause for for serious damage is greatly increased in concern. Current 12-volt designs won’t auto- 48-volt systems. Recent research shows that matically work at 48-volts; even simple fuses 48-volt arc energy is 75 to over 100 times will not migrate, let alone dimmers and active higher than in a 12-volt system. Such arcing load controllers. Some fuse panel and har- can generate temperatures up to 1800°F, ignite ness makers have found that common 12-volt fuel vapors, start a fire in plastic insulation, and mini- and maxi-fuses do not behave properly even melt metal. Simply redesigning relays, at 48 volts. They can fail to interrupt excessive switches, and fuses for higher voltage and currents properly, causing serious overload using flame-retardant materials is not a total conditions. Also, interconnection technologies solution; these component designs should have evolved for optimal cost and perfor- suppress arcs. The same is true for other mance in a 12-volt environment. The present connections, particularly those that could be design of connectors, circuit breakers, and opened during replacement of fuses, batteries, relay contacts may not be optimal at 48 volts. and other components. Mechanical design Therefore, manufacturers must re-evaluate features must ensure that electrical terminals component suitability for the higher voltage. are correctly seated and locked; therefore, Tests can range from simple continuity tests to increased use of clips, clamps, and shields full electrical characterization of a component's may be required. functional performance at 48 volts. Industry Constraints Reliability and Safety Issues Multiple voltage systems increase the possibili- At 48 volts and higher power levels, many ties of cross voltage system wiring mistakes, components, such as wires and relays, experi- which can lead to component damage and ence electrical stress that is four times higher potentially fires. For the dual voltage design, than before. With higher stress, components where do the 12-volt systems end and the tend to break down more often. Therefore, 48-volt system begin? Each OEM differs from component and module manufacturers have one another and they will continue to build to perform more reliability testing, such as equipment accordingly. There is a long list of burn-in and accelerated stress tests, to ensure electrical loads on a truck and if OEMs do not adequate service life. comply with one another, the technician and

Safe distribution of 48-volt power throughout a heavily optioned HDV also is a challenge. In the first place, the 48-volt standard was established because higher voltages create human safety issues. For example, 50-volts can stop a human heart, and anything higher than 60-volts requires more heavily insulated wires and connectors, which add weight. To prevent fires, electrical distribution designs must allow for jump-starting at the higher voltage, and provide protection if battery connections are reversed. Figure 22

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—21 service provider that are not in the dealership components will be redesigned or replaced. In concept will make costly mistakes. The Mas- many cases, suppliers will be asked to make sachusetts Right to Repair Act (and similar them lighter, more efficient, and less expensive. legislation) will be critically burdened and the This probably means that semiconductors will cost of information will be as advanced as 48- replace electromechanical designs in some volt technology. switch and relay applications. This will call for higher power devices, such as metal-oxide Manufacturers will once again recreate a bat- semiconductor field-effect transistors (MOS- tery and voltage system structure that would FETs) in higher voltage packages. innovate the future of trucking industry as automotive did 60 years ago. Just as the HEV While basic designs of existing assembly and research and development ignited through- test equipment should be adequate for 48-volt out the automotive industry into the trucking components, the higher voltage will require industry, 48-volt E/E systems would have the some modifications. For instance, additional same effect through dual voltage systems. production testing may be required to verify The problem with implementing this type of arc suppression and EMI compatibility compli- higher voltage now, rather than 20 years ago, ance. To design the new 48-volt components is because there are more electronics onboard properly, HDV manufacturers and their sup- HDVs than there ever has been. pliers must understand critical engineering and performance issues. As a result, there The number of parts and part suppliers in the will be increased research and development trucking industry is considerable and to decom- activity involving the electrical characterization mission any amount of it — say half of 12-volt of devices and their designs. Typically, this systems — stresses the industry in such a entails electrical measurements under vari- way that it may not be up for the challenge nor ous load conditions, insulation resistance and the expense. The future 48-volt infrastructure high-potential testing, and very low resistance would have to be built from the ground up to measurement of relay contacts and connector meet proper testing, material handling, cost terminals. logic, and OEM specifications. Also, there are a number of aftermarket companies and GOALS independent shops that would suffer through Return on investment (ROI) is the absolute this transition. After all, 80 percent of fleets and main goal for any type of technology improve- independent shops use aftermarket service ment, even if it involves competing with gov- and parts for their availability, quality, and price ernment regulations. Anyone who purchases to factor in an additional level of provision. anything extra from its original investment wants the value of that extra cost to be returned Extensive Test Requirements and New in a minimum amount of time and repeatedly Manufacturing thereafter in financial savings. The 48-volt E/E Implementation of 48-volt systems will affect system is meant in the near possible future the design, manufacturing, assembly, and to become the standard in everything mobile testing of most electrical and electronic com- that requires electrical power. If the 48-volt ponents. Electromechanical components such revolution comes to pass, there will no longer as alternators, motors, and starters may require need to be an ROI for the sake of complete more time on field coil winding machines to trucking manufacturer change. It will become get the same number of ampere turns (given the adopted source of natural ROI because that the current and wire gauge will be one- its purpose is to save fuel and leave less of a quarter of what it was for 12-volt devices). Other carbon footprint.

© 2015— TMC/ATA TMC Information Report (2015-3) DRAFT—22 Price and Benefit fleets will select different technology pathways The cost of new higher voltage platforms will depending on their application, emission re- be of greater expense than the modern com- quirements and fuel efficiency needs. mercial vehicles today because with advanced technology arises an advanced price tag. HEVs Outlook market the same way, although for mild or There is potential long-term merit in exploring micro HEVs the value will almost be the same 48-volt E/E systems for more than just fuel and the cost will be mild as compared to a full economy improvements. It is likely that the HEV. In the trucking industry, fuel efficiency ultimate value of higher voltage systems will lie gains and acquisition costs always increase with its potential empowerment for advanced together and for whichever HEV is decided technologies that constantly suggest a superior by OEM specification preference will meet or way of HDV improvements. For example, new surpass the emission standards. Compared engine technology, such as multi-fuel turbines, to 12-volt conventional Class 8 heavy-duty is in development that will completely redesign vehicles, micro HEVs with 48-volt E/E systems the HDV engine by removing piston and valves are expected to return fuel savings of up to and implementing a turbine rotor that oper- 15 percent in city driving and 15 percent less ates by flex-fuel. Benefits in current areas of emissions; mild HEVs are expected to return consideration go beyond regenerative braking fuel savings of up to 25 percent in city driving as by significantly increasing foundation brake and 25 percent less emissions. Full HEVs life. This has always been an inhibitor for fleets that have been experimented with reportedly and will ultimately reduce maintenance costs. return fuel savings of up to 40 percent. The Significant driveability enhancement can aid in fuel economy trend could almost equal the driver retention and improve safety by possible increased price difference from a conventional increase in driver workload. HDV. The problem is fleets expect payback in 24 to 36 months since the average turnaround Fleets, OEMs, and suppliers are eager to of a truck is 3 to 5 years before warranty and participate in the “green revolution,” but there residual value is depleted. are significant challenges that will take time to overcome. Development of economical, Although mild and micro HEVs have great reliable energy storage (batteries) is foremost potential in the stop-start areas of operation, in this lineup. As with other initiatives, such it isn’t of great importance to long distance as electronic engine controls and electronic freight carriers that rarely operate in heavy stability controls, this journey will likely take traffic conditions. Therefore, the rest of the 10 to 15 years. With E/E technology always at 48-volt potential is of significance when con- an exponential rate of improvement, there will sidering the amounts of horsepower and fuel almost never be a solid base architecture for mileage that is gained from engine mechanical the constant ever changing trucking industry mounted components changed to electrical improvements. Model results are promising, powered loads. When an engine’s main goal but the case has yet to be made in real world is to run at maximum efficiency, any available operations. This is not a market to jump into HEV technology used onboard is decreased lightly, but for those companies in it for the long driving over 60 mph. Fleets are all different haul, it’s a journey worth making. and each fleet has different goals. Therefore,

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