CATERPILLAR REINVENTS THE LEAD-ACID BATTERY

Lead-acid batteries haven’t changed much since 1859.

Lead-acid batteries haven’t changed much since 1859. The chemistry is well understood, production costs are low, and there is an established recycling infrastructure. On the other hand, the batteries are heavy and the lead grids break down. Heavy-equipment maker Caterpillar (Peoria, IL), tired of in-the-field failures and excessive warranty costs, set out on a two-year mission to find a supplier with a better technology, and—having failed—turned to its R&D staff to come up with a better solution. The result was exciting enough to convince Caterpillar to transfer the scientists and all rights to the budding technology to a jointly funded company, Firefly Energy (Peoria, IL; www.fireflyenergy.com). Its partners in this venture include BAE Systems, Electrolux, and the State of Illinois.

“Kurt Kelley, an advanced materials scientist, got the assignment, and he began by taking a lot of lead-acid batteries apart,” says Mil Ovan, senior v.p. and co-founder of Firefly. “His first idea was to put a carbon nano layer on a lead grid to delay the corrosion effect on the plates, but the corrosion still won.” That’s when he spotted the piece of black graphite foam sitting on a fellow researcher’s desk. Caterpillar had gotten the foam from one of the national labs and was investigating it for a next-generation radiator. Kelley, however, envisioned using it as a replacement for lead grids. “Flowing the lead throughout the porous structure of the foam increased the surface area about 2,000 times when compared to a typical lead grid,” explains Ovan. “Plus, the foam is stronger and lighter than lead plates, and the increased surface area means you need less of it to give the same power.” The real upside, however, is the fact that the graphite foam doesn’t sulfate like lead grids do, which means the negative plates don’t get covered in an electrically impenetrable coating if left to sit for any length of time. 

There are other benefits as well. The electrolyte in a lead-acid battery is a big resistor due to the distance the ions must travel between the grids. In the Firefly battery, this space has been reduced from millimeters to microns. As a result, the ability to both send out power and recharge is claimed to be dramatically better. “The Firefly battery has about seven times the recharge speed of a typical lead-acid battery, and its output doesn’t diminish if it is left discharged for any length of time,” says Ovan. This means the technology has potential for use in hybrid vehicles.

To find out more, you’ll probably have to do what the partnering companies have, which is to invest heavily and sign a non-dis-closure agreement. One reason is that the numbers associated with battery technologies are suspect at best. Or, as Ovan puts it in a Mark Twain-like quote: “There are liars, damn liars, and battery companies.” To get a true comparison, it’s necessary to look at the number of cells, temperature range, application, discharge rate, and other parameters that influence how a technology performs. And Caterpillar, Electrolux and BAE Systems have been given performance numbers based on applications they chose.

However, there is one area Ovan is sure his company’s technology has everyone else beat: cost. “What people don’t appreciate is that the cost of the cobalt used in lithium-ion batteries has jumped from $40,000 to $60,000 per ton, and the nickel-metal chemistry has jumped from $10,000 to $14,000 per ton in the last 18 months due to China’s increased demand for stainless steel,” he says. Lead, on the other hand, has risen from $500 to $1,000 per ton. So while the Firefly battery may be slightly more expensive than a conventional lead-acid design in terms of dollars per kilowatt-hour, prototype units use half the lead. The next generation will use ¼ the amount.

Electrolux—it owns Husqvarna, Poulan, Weed Eater, and makes lawn and garden tractors for Sears—is the first customer for the Firefly battery, and is focusing its efforts on lawn and garden applications. In addition, says Ovan, “a couple of car companies are interested, and we expect to be making samples they can test.”—CAS