GM Charged Up About Li-ion for 2010 ‘Mild’ Hybrids
March 05, 2008

By Bill Visnic

General Motors Corp.’s hybrid electric vehicle engineers announced at the Geneva auto show today they will have advanced lithium-ion batteries ready for the company’s next generation of “mild” hybrids coming in 2010.

The batteries, which GM says are being developed by Japan’s Hitachi Vehicle Energy Ltd., will improve performance and efficiency of the Saturn Vue Green Line and Aura Green Line and the Chevrolet Malibu Hybrid, GM sources say. Fuel economy, for example, will be some 15 to 20 percent better than the same vehicles with conventional gasoline-engine powertrains.

The electrical capacity of the new hybrids means they will be three times more powerful than in the current hybrid variants of the Vue, Aura and Malibu, said Dan Hancock, vice president, GM Powertrain global engineering. He said the new batteries’ extra capacity also will enable higher levels of regenerative braking (which helps to increase efficiency) and should enhance acceleration, as well.

The mild-hybrid system in these vehicles centers on GM’s belt alternator-starter, or BAS, architecture. A more powerful starter-alternator not only can assist the gasoline engine during acceleration, but also enables the recovery of braking energy normally dissipated by the brakes, sending that energy to the battery pack to be used when needed to aid in acceleration.

But perhaps the most important function of the BAS system is the ability to shut off the engine when the vehicle is stationary, such as when waiting for a stoplight. The enhanced starter-alternator can instantaneously restart the engine when the driver's foot is moved from the brake to the accelerator.

Stephen Poulos, chief engineer for hybrid systems, said the new lithium-ion batteries will improve GM’s mild hybrids, models that make the gains of hybridization “very accessible to people at a very accessible price.”

GM engineers cannot, however, say how much more the vehicles with the advanced new lithium-ion batteries will cost compared with today’s models that use less-sophisticated nickel-metal hydride chemistry — but they do say any upcharge is likely to be modest, given the vehicles’ comparatively low price. The current Aura Green Line and Malibu Hybrid — essentially the same vehicle — start at $22,790.

Poulos said by using the new lithium-ion batteries, “We took the same (BAS) system and put it on steroids.” He said the new batteries are 24 percent smaller and have 40 percent less mass, yet provide 33 percent more power.

Somewhat curious, however, is Hitachi’s role in supplying the batteries for this system. GM has awarded contracts to develop advanced lithium-ion batteries for its coming “plug-in” hybrid vehicles and its so-called “extended-range electric vehicles” (E-REVs) — both of which purportedly are scheduled for launch around 2010 — but Hitachi is taking part in none of those efforts. One possibility is the fundamentally different, lower power demands of the mild-hybrid system for which Hitachi is developing lithium-ion.

Poulos said one of the more intriguing possibilities for the new system is as an affordable companion to a downsized, turbocharged engine. There is a considerable movement already under way to employ smaller engines to improve fuel economy, but equip them with turbochargers to deliver the performance of a larger engine when required.

The only problem, say GM engineers, is turbocharged engines still tend to suffer from “turbo lag,” a brief moment at low speed when the engine is slow to respond to the demand for acceleration.

The newly powerful, lithium-ion-backed mild-hybrid system could be the perfect solution, said Poulos, aiding low-speed acceleration for a brief time until the turbocharger is pumping at full power. The electric boost from the BAS-hybrid system “gives you immediate torque response,” he said.

The new system also is adaptable to a wider range of global vehicle architectures, says GM.

The new lithium-ion batteries and BAS system will debut in North America in 2010 and “there’s significant volume growth potential,” said Poulos. GM says it could sell upward of 100,000 units of the new system once production is in full swing. Those kinds of numbers also could help reduce overall cost to the customer, Poulos added.

One thing GM will not be able to claim, apparently, is the world-first use of lithium-ion batteries for a mass-production car. Daimler AG’s Mercedes-Benz announced earlier at the Geneva show it will use lithium-ion batteries for the S 400 BlueHYBRID — a mild-hybrid variant of the S-Class fullsize sedan that will launch in 2009.

The lithium-ion battery developer for the Mercedes BlueHYBRID system is Continental AG, which also has been contracted by GM as one of two suppliers to develop lithium-ion batteries for GM’s advanced “E-Flex” hybrid architecture. The E-Flex system is the basis for the Chevrolet Volt, GM’s high-profile E-REV, which GM hopes will be able to travel as far as 40 miles solely on electric power.

For E-Flex, Continental is reputed to be the systems integrator, and the lithium-ion batteries are a development of Watertown, Mass.,-based A123 Systems. It was not known at press time, however, if the Continental-developed Mercedes hybrid system employs A123’s lithium-ion batteries.

Photo by GM: GM CEO Rick Wagoner makes the automaker's announcement on lithium-ion batteries at the Geneva International Motor Show.

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