GM Mild Hybrid System To Return In 2011, On Steroids

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2009 Saturn Vue Hybrid

2009 Saturn Vue Hybrid

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As Mark Twain is supposed to have said, "Reports of my death have been greatly exaggerated." (Although, sadly, he actually didn't say it.)

In this case, the "my" is the General Motors mild-hybrid powertrain, sometimes known as the Belt-Alternator-Starter or BAS system. And it will return for 2011, in a far more powerful form.

Mild hybrid, minimal numbers

Like most mild hybrids, the BAS system essentially shuts off the engine when the car stops, and quickly restarts it as the brake pedal is lifted. It also provided some electric assist to the engine at speed, but no all-electric running.

The BAS system is fitted to a 2.4-litre EcoTech four-cylinder engine. It comprises a 5-kilowatt motor/generator, a pump added to the automatic transmission that keeps up pressure when the engine turns off, and a nickel-metal-hydride battery pack that puts out 36-Volt power. The EcoTech engine also retains its standard 12-Volt starter, which averts any starting problems when the engine is cold.

The BAS mild hybrid was offered in the 2007 Saturn Vue Green Line (the old square one), the 2007-2009 Saturn Aura Hybrid, the redesigned 2008-2009 Saturn Vue Hybrid, and the 2009 Chevrolet Malibu Hybrid.

None has sold in huge numbers; Chevrolet's website cites "very limited availability". With Saturn about to depart the GM fold, the future of the Saturn mild hybrids is unclear.

GM hasn't yet worked out the specifics of its arrangement with the Penske group that is buying Saturn, but it will provide Penske with at least some Saturn models through December 2011. It's unclear whether the Vue Hybrid and Aura Hybrid will be among them.

The BAS hybrid is also used in a Buick LaCrosse EcoHybrid sold only in China; GM plans to discontinue that model sometime this summer.

US sales of the BAS system were never expected to be huge--across all four vehicles, volume likely never reached more than 15,000 per year--but they were crippled just as gas prices hit their high of $4/gallon last summer.

Leaks in a few Cobasys nickel-metal-hydride battery packs required the recall of roughly 9,000 mild-hybrid Saturns. Some packs had developed hairline cracks in plastic modules inside the outer case, and GM chose to replace every pack.

That severely limited the launch of additional models (mostly the Malibu Hybrid) using that pack as well.

2009 Malibu Hybrid: limited sales

The latest death notices started when Automotive News said the Chevrolet Malibu Hybrid would only be available for fleet sales in 2010, given the large number of unsold hybrid 2009 Malibu models.

That technically confusing story spawned a legion of "GM Kills Hybrid" stories, including our own on

Many accurately noted that the base 2009 Chevrolet Malibu fitted with a 2.4-liter four-cylinder engine and six-speed automatic achieved mileage (22 mpg city / 33 mpg highway) almost as good as the Malibu Hybrid (26 mpg / 34 mpg) for roughly $2,000 less.

Indeed, analysts suggest that fewer than 5,000 Malibu Hybrids have been sold in the 14 months since it went on sale in April 2008. At least some of those Malibu Hybrids have shown up as New York City taxis and in other fleet uses.

There's a big "but", though. GM had already revealed technical details of its second-generation BAS system more than a year ago, at the 2008 Geneva Motor Show. GM called it both more technically advanced and far more cost-effective than the current generation.

BAS 2.0 on the way

The revised system uses a lithium-ion battery pack with cells from Hitachi Vehicle Energy Inc., delivers 4 times as much power (up to 120 Volts versus the current 36 Volts), and is 24 percent smaller and is 40 percent lighter.

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