With as much as 60,000 barrels of oil pumping into the Gulf of Mexico every day, it seems like the next generation of alternative-fuel vehicles can't get here soon enough. Much hope has been pinned on forthcoming electric vehicles like the Nissan Leaf to help wean us off fossil fuels. Yet despite all the advances in battery technology, electric-vehicle batteries remain expensive. But why?

To get some answers, we turned to two experts in the field. Bill Reinert is Toyota's national manager for advanced technologies. Toyota builds more hybrid vehicles than any other automaker, and its Prius is the best-selling hybrid on the market. Joe LoGrasso is GM's Global Battery Systems engineering group manager. GM has been developing the plug-in hybrid Volt, which is scheduled to go on sale later this year.

Battery Basics

The third-generation Prius uses a battery pack composed of 168 nickel-metal hydride (NiMH) battery cells making 1.2 volts each. "Nickel-metal hydride batteries are durable and robust, which is essential for automotive use," said Reinert. "To date, Toyota and Lexus combined have global sales of approximately 2.5 million hybrid vehicles using this technology."

"We know how to work with nickel-metal hydride batteries and in hybrid applications, they can last the life of the car. We have a number of hybrid-electric vehicles with more than one hundred thousand miles," he said.

The drawbacks of NiMH batteries, however, include:

  • Limited service life. If repeatedly deep-cycled, (i.e., the charge is completely depleted and then recharged, especially at high load currents), battery performance begins to deteriorate after 200 to 300 cycles.

  • Limited discharge current. Repeated discharges with high load currents reduce the battery's cycle life.

  • Require more complex charge algorithms. NiMH batteries generate more heat during charge and require a longer charge time.

  • Sensitive to high temperatures. Performance degrades if stored at elevated temperatures. NiMH batteries should be stored in a cool place and at a state-of-charge of about 40 percent.

  • Maintenance. NiMH batteries require regular full discharge to prevent crystalline formation.

"In reality, NiMH batteries are considered an interim step to lithium-ion batteries," said Reinert. "It's a question of overcoming the hurdles lithium-ion technology presents."

The Next Step

Lithium-ion batteries (Li-ion batteries, or LIB) are attractive for automotive applications due to their higher energy density and smaller package requirements. Considered a low-maintenance battery, LIB have neither battery-memory issues, nor do they require scheduled cycling to prolong battery life.

Despite its overall advantages, lithium-ion still has some drawbacks. It is not as robust and requires a protection circuit to maintain safe operation. Built into each pack, the protection circuit limits the peak voltage of each cell during charge and prevents the cell voltage from dropping too low on discharge. In addition, cell temperature must be monitored to prevent temperature extremes.

While the requirements to monitor charge and temperature make LIB more expensive to design and manufacture, their material and manufacturing requirements also factor into the cost. "Lithium is found in areas such as Bolivia, China, and Afghanistan, all of which pose not only a long logistics trail, but also certain geopolitical consequences," Reinert explained.

Recent findings of lithium in Afghanistan are so great that one internal Pentagon memo stated the country could become "the Saudi Arabia of lithium." How this discovery will affect the price of lithium remains to be seen, however, and will take many years to become a factor in the marketplace.

Manufacturing facilities for LIB are another part of the price equation. "Lithium-ion batteries and battery packs must be manufactured in hospital-clean facilities," said Reinert. "Building such factories in a size large enough to be efficient is extremely expensive."

Making Brownstown Green

General Motors is tackling the manufacturing issues head-on. Its $43-million investment in an existing facility located in Brownstown Township, Mich., will allow GM to manufacture lithium-ion battery packs for the Volt as well as other extended-range electric vehicles. "The Brownstown facility will be the first lithium-ion battery manufacturing plant in the U.S. operated by a major automaker," said Joe LoGrasso, GM's Global Battery Systems engineering group manager.

"Since GM is not in the business of manufacturing battery cells, we are partnering with suppliers who demonstrate the necessary technological and volume-manufacturing ability," continued LoGrasso. "The Brownstown facility will be capable of taking those battery cells in one door and sending completed battery packs out another."

LoGrasso believes that once cell manufacturing has fully transitioned from overseas to the United States, suppliers will be able to achieve greater manufacturing efficiencies. "As suppliers become more capable, scrap rates will drop, allowing them to realize their full output potential. Prices, as a result, should decrease. By how much, though, is impossible to predict."

There is another factor that may offset the cost of the Volt's battery pack. "The Volt's battery pack can be disassembled for use in stationary applications, thereby extending its useful life and delaying end-of-life issues," LoGrasso explained. "When the battery pack has reached a point near twenty-five percent of reduction in usable range, there is still a lot of life left in the batteries for non-automotive uses."

Some Numbers

When a battery pack does go bad, how much does it cost to replace it once it's out of warranty? To get a sense for this kind of expense, we called our local Toyota dealership, Dunning Toyota of Ann Arbor, Mich., and spoke with service manager Woody Woods.

Woods said that although there are three different battery packs that have been used in the different Prius models over the years, the replacement cost is similar, ranging from about $2,300 to $2,700, without labor (which isn't that much, in this case, adding less than 10 percent to the total).

The Prius battery back has less than two kilowatt hours of capacity, while the forthcoming Volt has 16 kWh capacity. The all-electric Nissan Leaf offers 24 kWh and the electric Tesla Roadster battery pack contains a whopping 53 kWh. So some simple math can give you an idea of how pricey the battery pack can be for a pure electric.

Liquid Fuels Still Rule

Toyota's Reinert doesn't see a time in the foreseeable future when full electric vehicles will achieve price parity with hybrids. "While regulatory action such as a gas tax or incentives for electric vehicles could level the playing field, market-driven forces alone won't make full electric vehicles price competitive," he said.

"The reality is that the internal combustion engine is not the outdated technology that people might think," Reinert continued. "In its most modern iteration, the internal combustion engine is a very efficient powerplant, and there are still great advantages in storing fuel in liquid form. For example, when you take into account tailpipe emissions such as nitrogen oxides, the most advanced low-carbon diesels, run on alternative fuels such as those sourced from algae, can achieve parity with hybrid electrics."

The bottom line: regardless of their cost, electric and hybrid-electric vehicles, while not an end solution, will have supporting a role in transportation. "There will always be other players," said Reinert, "and old technologies will still be worthy of another look."

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