Ten years ago, startup lithium-ion battery maker A123 Systems was the darling of business media, poised to enter the big leagues of electric cars after successfully selling its cells to power-tool makers.

Then came the Fisker Karma, U.S. government grants, a factory in Michigan, the economic meltdown, quality-control problems, and ultimately bankruptcy.

DON'T MISS: Electric Cars "Not Viable Markets" For Reborn A123 In U.S., Europe In Next 10 Years, CEO Says

A decade later, the reconsistituted A123--now owned by China's largest auto-parts maker, Wanxiang--sees only 25 percent of its revenue from battery packs for electric vehicles, all of them in China

The rest is from much smaller batteries for start-stop and so-called microhybrid systems, which CEO Jason Forcier sees as a much more promising business.

A123 Systems Employees Perform Quality Check on a Lithium-Ion Battery Pack [source: A123 Systems]

A123 Systems Employees Perform Quality Check on a Lithium-Ion Battery Pack [source: A123 Systems]

In an interview with industry trade journal Automotive News, Forcier notes that market demand for the smaller batteries is poised to explode as carmakers increasingly fit start-stop systems.

Those systems, which switch off the engine when the vehicle is at rest, are already spreading rapidly through Europe and Asia, and are poised to do so in North America as well.

ALSO SEE: Chinese Group Approved To Buy Ailing A123 Systems Battery Firm (Jan 2013)

The reason is that they help to boost fuel-efficiency ratings at far lower cost (albeit lower gains too) than far pricier full hybrid systems with high-voltage battery packs and the associated power electronics and larger electric motors.

Most start-stop systems today use absorbent glass-mat lead-acid batteries, but lithium-ion replacements are expected to replace them slowly as costs fall.

2012 Fisker Karma from the Rogers' Classic Car Museum collection

2012 Fisker Karma from the Rogers' Classic Car Museum collection

Lithium-ion batteries are not only much lighter than lead-acid equivalents--about one-quarter the weight--but aren't damaged by the frequent charging and discharging cycles of start-stop systems.

In the electric-car world, A123 may be best-known for having provided the battery packs for the ill-fated 2012 Fisker Karma range-extended electric luxury sedan.

MORE: New Fisker Karma Details May Come As Soon As This Month

Wanxiang owns Fisker now as well, but Forcier said that while A123 would like to provide the batteries for a projected 2016 restart of Fisker production, the joint ownership "doesn't mean they have to use our battery."

Fisker's new parent is reportedly working to resolve dozens of quality and reliablity issues in the aging Fisker design before its rumored relaunch next year, under the brand name Elux.

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