Batteries that Don't Die
New technologies are transforming an old workhorse, promising all-electric lawnmowers and hybrid military vehicles.
Inexpensive and rugged lead-acid batteries, as everyone knows, can start a car in the dead of winter. But their excessive weight and their tradeoff between power and life – the powerful version in your car doesn’t last more than a few years – have kept them out of hybrid vehicles and prevented their widespread use in all-electric vehicles.
Now the humble lead-acid battery has been gutted and redesigned, cutting its weight, extending its lifetime, and putting it in the same performance category as the nickel-metal hydride batteries used in today’s hybrid cars, according to Firefly Energy, a Peoria IL company that’s developing the new batteries for specific applications.
These new batteries are about one-third to one-quarter as heavy as traditional lead-acid batteries, and can be made about as powerful as nickel-metal hydride batteries without sacrificing longevity, says Mil Ovan, senior vice president and Firefly cofounder.
But the main advantage of the new batteries, he says, is price. Because lead is relatively cheap, and a huge infrastructure already exists to make lead-acid batteries, the company is confident they can produce the batteries at one-fifth the cost of nickel-metal hydrides. What’s more, if hybrid cars become more popular, as expected, the cost-gap could widen as demand for nickel rises. “There’s probably not enough nickel to put into everybody’s car. Lead is more abundant,” says I. Francis Cheng of the University of Idaho, who’s developing advanced lead-acid batteries for the military.
Firefly dealt with the weight and performance issues by replacing the traditional heavy lead grids that collect electrons generated by a battery’s chemical activity with a light graphite foam. The foam increases the surface area for the battery’s chemical reactions, according to Cheng, whose separate work at Idaho uses additives to improve the weight and performance of lead-acid batteries. The increased surface area allows for faster charging and more powerful discharging. When engineers had experimented with increasing the surface area of the old lead grid, it accelerated the deterioration of the battery, forcing them to choose between a powerful battery that failed quickly or a less powerful, but more stable one.
The graphite foam grid is more resistant to the corrosion that eventually causes traditional lead-acid batteries to fail. Thus, it can last longer, allowing it to survive a long winter in a garage, for instance, which is useful in lawnmowers, Ovan says.
Although Firefly is still in the prototype-making stage, it has already caught the attention of several major manufacturers, including Caterpillar, where the core technology was first developed, and BAE Systems, manufacturer of the Bradley Fighting Vehicle. The Swedish corporation Electrolux, whose brands include Husqvarna, Poulan, and Weed Eater, plans to roll out all-electric products based on the battery next year, including lawnmowers and lawn tractors. Also, last month, a U.S. defense bill provided $2.5 million to Firefly for developing the batteries to power electronics on military vehicles while their engines are off during silent surveillance.
This new technology got its start after truck drivers – forced by emissions regulations to turn off their engines at truck stops and to run the air conditioning and television in their sleeper cabs with batteries – started complaining to Caterpillar that their batteries did not last long enough. The company turned to Kurt Kelley, then a Caterpillar materials scientist, and now chief scientist at Firefly Energy, for a solution.
“He had never designed a lead-acid battery before – which was the good news, because he was unconstrained by commonly held wisdom in the battery business about what you should and shouldn’t do to a lead-acid battery,” says Ovan. Kelley’s inexperience led him to find a working form of graphite foam – even though the industry had already judged foam as likely to degrade battery performance.
While the technology looks promising, Firefly is entering a competitive market. Many industry and government insiders believe that a new generation of light-weight, high-power lithium-ion batteries, which are overcoming previous safety, cost, and lifetime concerns, will replace the nickel-metal hydride batteries currently used in hybrid cars. And Firefly will also need to contend with future offerings from others, such as the University of Idaho group.