Lead-Acid Could Challenge Lithium-Ion in Hybrids 23115

With disenchantment in lithium-ion technology on the rise, lead-acid batteries may be poised to play a bigger role in green vehicles.

Automakers are said to be taking a closer look at lead-acid, in hopes that the century-old chemistry could serve in future vehicles that employ mild hybrid and start-stop powertrains. "When I conceived of this company two-and-a-half years ago, the interest in lead-acid technology was zero," Subhash Dhar, founder and CEO of Energy Power Systems (EPS), maker of a new lead-acid battery chemistry, told Design News. "Today, on a one-to-10 scale, it's a seven."

Several major automakers are now said to be looking at EPS's version of lead-acid, mainly because it could offer a huge cost advantage, without concerns of overheating. By today's measures, lead-acid's cost is approximately one-seventh that of a liquid-cooled lithium-ion battery, Dhar told us. And its safety performance is well known and widely accepted.

"There is huge dissatisfaction with lithium-ion right now," said Dhar, who co-developed the nickel-metal hydride battery for the Toyota Prius in the 1990s. "Years ago, we in the battery industry promised that lithium-ion would get down to $250/kWh. But here we are, 10 years later, and the number is still north of $700/kWh."

Dhar, whose company makes an enhanced lead-acid chemistry, believes his product could be especially important in start-stop vehicles, which turn off their engines and restart them at traffic lights and stop signs as a means of reducing fuel consumption. There, the energy density of the battery is relatively unimportant (because the vehicle runs on gasoline), while power density and cost are critical. As a result, lead-acid could be a good fit for mild and micro-hybrids. "In the first-generation start-stop systems, cost is going to be the big issue," Rob Martin, director of engine electrical engineering for Denso International America, which makes start-stop systems, told us. "So lead-acid makes sense there."

If lead-acid does make successful in-roads in such applications, it could be a big step for the old technology. By some estimates, start-stop could be incorporated in 50 percent of vehicles by 2020. And some start-stop cars could employ two batteries apiece.

In contrast, many experts are forecasting poor sales ahead for pure electric cars, virtually all of which use lithium-ion. "The pure electric car is now almost universally seen as a bit player," David Cole, chairman emeritus of The Center for Automotive Research (CAR), told Design News. "The heads of the big car companies see it as a technology for small vehicles, delivery vans, and a few mega-cost cars, whereas, mild hybrids and start-stop cars will be everywhere."