Oct 1, 2006 (From the CalCars-News archive)
This articles raises some of the questions we recently discussed in our blog, "Thinking About Lithium Batteries and Safety" at http://www.hybridcars.com/blogs/power/battery-safety.
Remember The Pinto
Jonathan Fahey, 10.16.06
You've heard about lithium ion batteries catching fire in laptops. Want one in your car?
If you are worried that a laptop powered by a dozen lithium ion cells may burst into flames, how do you feel about cruising down the highway at 70 miles per hour in a car powered by 6,000 of them?
Automakers are scrambling to get lithium ion batteries into hybrid vehicles, and they are hoping these batteries will make plug-in hybrids and all-electric vehicles possible soon, too. But talk about a public relations problem. The series of laptop computer fires that led Dell and Apple to recall 5.9 million Sony-made battery packs this summer were sparked by those same lithium ion batteries. "Yeah, there's that little thing called safety," says David Hermance, executive engineer for Toyotas Advanced Technology Vehicles.
Hybrid vehicles like Toyota's Prius, which are propelled by both gasoline and electric motors, now use nickel metal hydride batteries to store electricity. But Toyota and other automakers like lithium ion because they can get at least twice the horsepower per pound from the battery. And nickel's price has grown from $2 a pound to $13 over the past five years, making expensive hybrid vehicles more so. Problem is, lithium ion batteries are inherently unstable, so safety systems have to be built in to prevent the batteries from getting too hot from, say, overcharging.
Happily for Toyota, the batteries in hybrid vehicles are never fully charged. They capture energy during braking and release it during acceleration, all within a range from 75% charged to 45% charged. Johnson Controls, the big auto supplier, says coming lithium ion batteries will also have better safety systems. "Our thermal- management systems are orders of magnitude more sophisticated than what they use in laptops," says Alan Mumby, who runs the company's battery program.
But in vehicles that run for long periods on electricity only, like plug-in hybrids and all-electrics, engineers need to fully charge batteries to maximize driving range, the drawback to electric vehicles. A handful of companies, like A123 Systems and Valence Technology, are rushing to come up with safe lithium ion batteries specifically engineered for use in these vehicles. The big automakers won't be selling plug-in hybrids or all-electric vehicles soon, but tinkerer EnergyCS is developing a kit it hopes to sell for $12,000 or so that will replace the nickel metal hydride battery in Priuses with a plug-in lithium ion pack.