MOTOR Magazine

A MOTOR Magazine Newsletter
July 5, 2016

Contributed by Bob Chabot
48V Systems Gain Ground

New electrical architectures address power constraints

Few in the auto industry disagree that the future of propulsion systems requires increasing levels of vehicle electrification. Environmental concerns, including upcoming stringent regulatory emission targets in Europe in 2021 and the United States in 2025 are just one of many drivers.

At some point in the future, the internal combustion engine (ICE) will likely fade into history, yielding to all-electric propulsion, however the power is derived. However, between now and that indeterminate future time, the comparatively low cost and incredible convenience of using liquid fuel-burning vehicles will ensure that they remain the most common form of transportation.

"The most important feature of Delphi's mild hybrid 48V electrical architecture is its proliferation throughout the complete vehicle architecture. Delphi engineers designed a system that partners the nearly two miles of wires throughout a car with an additional electrical power source, without dramatically altering existing designs or adding much weight. And the system is relatively inexpensive, roughly a $600 per vehicle net cost to an OEM. (Video — Delphi Automotive LLP)

12V System Capacity is Nearly Maxed Out
In the interim as we approach that future convergence point, is it possible for a car to pollute less without sacrificing power, decreasing engine size or installing an electric propulsion system? "Yes!" say companies like Delphi Automotive LLP, other suppliers and automakers.

"There's not one global automaker that isn't actively looking today for a 48V solution," shared Mary Gustanski, Delphi's vice president for Engineering. "You need a motor, you need a battery, you need some power electronics … but the real enabler is 48V electrical architecture. Delphi's 48-volt mild hybrid system bridges the gap between conventional fuel-powered vehicles and electric vehicles."

It serves as an intermediate step on the path from current 12V to future full 48V systems. The associated innovations and technologies help stretch the viability of internal combustion engines. Two come readily to mind: 12V Stop-Start vehicle systems and 48V electrical architectures.

Typically, 12V stop-start systems implement some of the rudimentary technologies and features that were first developed for full hybrid vehicles, such as regenerative braking and electric power assistance.

A Lower Cost Solution for OEMs Facing Power Constraints
Stop-start vehicle systems are becoming common in many regions of the world. Stop-start capability with 12V electrical systems has already become relatively ubiquitous in Western Europe, and deployment is expected to expand rapidly in North America in the next several years.

Recently, OEMs and supplier stakeholders gathered at the Low Voltage Vehicle Electrification Summit, to discuss concerns and solutions to them that could move near term vehicle electrification forward. Attendees reached consensus that the current 12V electrical system itself is becoming a limiting factor due to its low practical power limit.

In large part, current 12V systems are already stretched to their limits with all of the power-drawing features and amenities included in today's cars and trucks. With a practical power limit of 3 kW from a 12V system, the actual use of stop-start is often limited by the need to maintain power levels for essential systems such as vehicle electronics and infotainment.

Tier 1 suppliers (such as Delphi and AVL) and market research firms (such as IHS Automotive and Navigant Research) project that by 2025, one out of 10 cars sold globally — more than 10 million units per year — will feature 48-volt, mild hybrid electrical. This volume would lower CO2 emissions by more than 10 percent, saving more than four billion gallons of fuel over the life of the fleet of vehicles in operation.

48V Architectures Spur Smart Electrification
Delphi's solution addresses this by integrating a small battery to capture energy typically lost during braking and reuse that energy for acceleration and to augment accessories traditionally powered by the vehicle engine. With up to 10 kW available — more than three times the conventional 12V power supply — this 48V system processes data faster and reduces the burden on the engine. That's engaged interest from several automakers.

The intermediate solution does more than allow energy recapture, cruising at highway speeds, and engine shut-off at higher speeds before the vehicle comes to a complete stop. It also:

  • Allows engineers to deploy more capable semi- and fully-autonomous systems, which can draw up to 4 kW for the actuators under peak load transient conditions.
  • Provides sufficient power for electric superchargers and the electrification of ancillary systems, such as oil and water pumps.
  • Utilizes the extra battery power capacity to efficiently power advanced driver assist, air conditioner, engine cooling and other systems.
  • Lowers emissions and increases fuel economy by up to 15 percent in direct injection engines.

"The air will be cleaner thanks to 48-volt, mild hybrid systems, but there's no reason to fear your car will limp back into gear after a stop," Gustanski noted. "The 48V technology leverages an 'e-charger' (an electric turbocharger) to improve vehicle launch when the engine is re-started once the light turns green. This is a win-win for automakers looking to meet regulatory requirements without significantly raising cost and their customers looking to reduce their carbon footprint without slowing down."

Conversion from 12V to 48V electrical architectures provides automakers with the means to transfer the accessory load off the engine, improve fuel economy, reduce emissions, heat up vehicles at start-up faster and other potential benefits.

Evolving to Full 48V Electrical Architectures Will Take Time
The transition to 48V systems is not as simple as installing a bigger battery and generator. Many OEMs will opt to stay with existing 12V vehicle systems as long as possible in order to take advantage of economies of scale, but they will also need to install mechanisms to handle dual voltage as consumers install power-drawing products and services.

There is also the question of the best type of energy storage to use. Lithium ion batteries are lighter but more expensive and have poor cold engine start characteristics. Various types of advanced lead batteries, such as absorbed glass matt, lead-carbon and other are already in use or in development, but they each have their own issues.

Look also for batteries to ramp up in price and power to accommodate emerging consumer demands for onboard amenities, while also being environmentally friendly. Some new batteries are in the $1,000 range already. Finally, there is also the overall cost-benefit analysis as high-voltage electrification becomes more affordable over time. For instance, as vehicle electrification continues to ramp up, at some point might it make more sense to skip or transition from 48V systems, which can add $600 to $1,000 or more to the cost of a vehicle, and adopt even high-voltage architectures.

The days of just replacing a relatively inexpensive battery with a new one to remedy some problems are near over. With automakers and suppliers focusing more attention on batteries, technicians and shops will have to prepare for new inbound battery technologies, both in terms of the service knowledge and competencies required.

Like Kermit the Frog sings, it isn't easy being green. Nor is embracing change.

[Editor's note: For the latest diagnostic and automotive service insights, read MOTOR Magazine's July 2016 issue.]

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