Development of lithium-ion (Li-ion) battery cells is a daily newsmaker, and the recent history of nickel/metal hydride (NiMH) in hybrid cars is a statistical fact. However, Johnson Controls Inc., which claims to be the world’s largest automotive battery maker, believes the much-maligned 12-volt lead-acid still battery has a bright future.
JCI sells 120 million lead-acid batteries globally each year, according to Brian J. Kesseler, Vice President/General Manager of the company’s Americas Power Solutions, who said full hybrids, including plug-ins, will be only 6% of the market by 2020.
Additionally, the 12-volt lead-acid type remains the choice in most hybrids for starting, lighting, and some accessories, Kesseler pointed out, and it also is used in microhybrids, vehicles that perform engine stop-restart at traffic lights, in drive-up lanes, and in similar situations.
Microhybrids, he noted, are being widely rolled out in Europe, where they boost fuel economy 5 to 8% at a small cost premium over a conventional automobile. Unlike the more expensive 42-volt mild hybrids, however, they don’t deliver regenerative braking and acceleration assist. JCI sold a total of 1.2 million 12-volt lead-acid batteries for European microhybrids in 2007 and 2008 and expects 1.5 million sales this year.
JCI has hopes that its Optima battery, with its far longer life, including greater capacity for deep cycling and a larger number of cycles possible, will penetrate the microhybrid market. The Optima has the two lead plates with a glass mat between them. The mat absorbs the electrolyte so there is no free liquid, a design called AGM (absorbent glass mat), and the “sandwich” is rolled into a tight, rigid cylindrical cell. Although it has a relief valve, the Optima is essentially a sealed battery.
It is 50% more expensive than a conventional lead-acid but has superior vibration resistance. Pure lead is used in the plates for improved performance, as well as reduced corrosion, for double the life of conventional lead-acid designs with their need for lead-strengthening alloys. These advantages make it a possibility for use in premium microhybrids, possibly in the 2010-2011 time frame.
Optimas weigh 1.8 to 6.4 lb (0.82 to 2.9 kg) less than comparable lead-acid batteries, with the difference varying according to group size, and they are generally understood to contain less lead. However, JCI does not disclose the differences in amounts. An average conventional battery weighs 36.8 lb (16.7 kg) and contains 21.2 lb (9.6 kg) of lead, Kesseler said.
Additionally, he told AEI, research is underway to reduce lead content of conventional batteries, without reducing the electrical capacity. The PowerFrame design, in which the positive plate is stamped rather than cast with molten lead, was one successful effort, he said. It is used by JCI in all its U.S. manufacturing and is being phased in at its plants in other countries (Varta brand in Europe, LTH in Mexico, and Heliar in Brazil).
However, other improvements are being tested, some involving alternative alloying materials (silver and tin currently are most commonly used). “We’re looking at everything in the inner workings of the battery and have designs that challenge the paradigm that you need more lead for more power," Kesseler said.
Control of lead emissions remains an important issue, Kesseler said. Although 97 to 98% of battery lead is recycled in the U.S. and Western Europe, a new U.S Ambient Air Quality Standard, awaiting complementary regulations by the states, requires a 90% reduction in airborne lead emissions, from 1.5 down to 0.15 µg per cubic meter. This would be measured at the plant level, forcing improvements in both recycling and manufacturing processes.
Fortunately, he added, JCI plant emissions are close to the future standard, and the company is tightening further its virtually closed-loop system in which a truck delivers batteries from manufacturing plant to retailer, where it collects used batteries. It brings them to the smelter, where it picks up recycled lead and plastic and delivers the materials to the manufacturing plant.
Although it has been supplying NiMH batteries for hybrid applications, JCI is participating in the move to the far lighter Li-ion for everything from mild to full hybrids and plug-ins, Kesseler said. The company has development contracts for Li-ion batteries for plug-ins from General Motors (Saturn VUE), Ford (Escape), and Daimler AG (Mercedes-Benz Sprinter). JCI also has Li-ion production contracts for mild hybrids from Daimler (2009 Mercedes-Benz S Class), BMW (a 2010 model), and Chery (a 2009 model).
Production is centered at its plant in Nersac, France, a joint venture with Saft Advanced Power Solutions, a French specialist in high-technology batteries. Prismatic (rectangular “pancake”) designs, which have packaging benefits and potential performance and thermal management advantages, currently are being made primarily for heavy-duty applications such as buses. The lower-cost, more-developed, cylindrical cell Li-ion batteries are being produced for passenger cars, although some automobile prismatics are being produced, too.
A 10-year battery life is needed for plug-ins, Kesseler said, which Li-ion does not provide right now. However, he added, there might be an interim marketing solution at the five-year level, following which the battery could be recycled. The recycling costs currently are high, he said, and driving them down requires accepted engineering standards for design of individual cells and how the battery interfaces with the vehicle, he added.