Another new powertrain technology may be poised to bring major change to the auto industry by delivering the advantages of hybridization without some of the complexity.
This technology, known simply as 48V, combines a dual-voltage setup with the well-known advantages of start-stop technology. By doing so, it more effectively captures a vehicle's braking energy, provides more power for a growing list of electrical loads, and simultaneously boosts fuel efficiency -- possibly by as much as 15 percent.
"We believe that, by the end of this decade, 48V will become a significant part of the market," Craig Rigby, vice president of product management strategy for Johnson Controls Inc. (which has developed a 48V product), told us. "It's probably the next technology after start-stop that will make sense for the mass market consumer."
Employing a dual-voltage architecture, Johnson Controls' Micro Hybrid battery system would use a low-voltage lead-acid battery and a 48V lithium-ion unit. The system could boost fuel economy by 15 percent.
(Source: Johnson Controls Inc.)
If you're a bit skeptical because you think you've heard some of this before, you're not alone. During the late 1990s, auto industry executives talked up a technology known as 42V. After a few years of contentious debate, however, 42V died an inauspicious death. But suppliers say this technology is different; unlike 42V, it could offer a big jump in fuel economy. Moreover, the regulatory environment has changed, and battery technology has improved.
The 48V configuration, supported by a number of automotive suppliers, calls for a conventional 12V network using a lead-acid battery like those employed in most conventional vehicles. However, it adds an extra layer: a 48V lithium-ion battery with a separate 48V network. The 12V network handles traditional loads: lighting, ignition, entertainment, audio systems, and electronic modules. The 48V system supports active chassis systems, air conditioning compressors, and regenerative braking.
One of the keys to 48V is lithium-ion battery technology, which wasn't available at the time of the ill-fated 42V systems. Engineers say lithium-ion technology offers about three times as much energy density as lead-acid chemistry. "There's a size and weight advantage to using a lithium-ion battery," Rigby said. "Back in the '90s, we were looking at stringing three lead-acid batteries together to get that voltage."
More importantly, the 48V lithium-ion battery has more charging capability, making it a better candidate for capturing regenerative braking energy. "It really comes down to the notion of regenerative braking -- harvesting the kinetic energy from the vehicle during deceleration and storing it in the battery."