There is little disagreement in the auto industry that the future of propulsion systems includes increasing levels of electrification. At some point in the future, the internal combustion engine will almost certainly fade into history. 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. Despite that, a full spectrum of electrification solutions will make these engines more efficient until we reach that future convergence point.
Recently, stakeholders from both the OEM and supplier sides of the automotive industry came together in a suburban Detroit hotel for the 3-day Low Voltage Vehicle Electrification Summit, which raised just as many (if not more) questions than answers about the potential for intermediate electrification. The statement that can be made with any degree of certainty is that there is no silver bullet on the horizon that will suit every application.
Stop-Start and 48V
Navigant Research’s Stop-Start Vehicles report projects that nearly 60 million vehicles annually will include at least basic automatic engine stop-start functionality by 2024, while the 48-Volt Systems for Automotive Applications report projects that more than 7 million vehicles will have 48V electrical systems over the same timeframe.
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. However, 12V systems are already being 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 the vehicle electronics.
With up to 10 kW available, the additional power capacity provided by a 48V system will enable 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. More importantly, from an efficiency standpoint, 48V systems can enable energy recuperation, sailing at highway speeds, and engine shut-off at higher speeds before the vehicle comes to a complete stop. These enhanced systems can also provide sufficient power for electric superchargers and the electrification of ancillary systems such as oil and water pumps.
Not an Easy Transition
However, the transition is not as simple as installing a bigger battery and generator. Many existing vehicle systems will stay at 12V in order to take advantage of economies of scale, so there must be mechanisms to handle dual voltage. 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 absorbed glass matt and lead carbon are already in use or in development, but they each have their own issues.
There is also the overall cost-benefit analysis as high-voltage electrification becomes more affordable. At what point does it make more sense to skip 48V, which can add $800 to $1,000 or more to the cost of a vehicle, and just go high-voltage?
These questions and many more will be discussed at the PlugVolt Battery Seminar taking place at the Sheraton Detroit Metro Airport Hotel from July 26 to 28. More than two dozen speakers will be on hand to discuss battery chemistry, automotive applications, and grid storage.
Tags: 48V Systems, Advanced Transportation Technologies, Low Voltage Electrification, Stop-Start Vehicles, Transportation Efficiencies
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