The dark cloud hanging over electric vehicles in the wake of recent Chevy Volt fires may not lift, no matter how much engineers to do improve EV safety. That's because they're up against the gating factor of battery pack cost.
Experts say rising concerns over safety are going to make it tougher for engineers to dramatically cut the costs of lithium-ion battery packs. Already, General Motors is reportedly considering a redesign of its lithium-ion battery pack to help prevent damage during a collision.
"We just don't know how much lower we can go in terms of price," says Donald Sadoway, a battery expert and the John F. Elliott Professor of Materials Chemistry at Massachusetts Institute of Technology. "It's not as if we can stand on the shoulders of all the work that's been done on cellphone and laptop batteries up to now. Laptop batteries don't have to be crashworthy."
The Chevy Volt battery pack caught fire three weeks after a crash test damaged it.
Photo courtesy of GM.
The National Highway Traffic Safety Administration said one Volt fire occurred after a side crash test was performed on it in May. During the test, the vehicle's battery was damaged, and a coolant line was ruptured. The fire occurred three weeks later. Three similar tests in November did not result in fires, though one damaged battery did emit sparks and smoke, the agency said.
Experts are confident that current cooling systems, coupled with improved crashworthiness, will keep electric cars safe. "We will learn how to better deal with the safety issues," says Elton Cairns, a professor of chemical and biomolecular engineering at the University of California-Berkeley and a designer of fuel cells for the Gemini spacecraft program during the 1960s. "After all, any battery that can fit on a vehicle stores much less energy than a tank of gas."
Still, the concern is that lithium-ion batteries are already too costly, and that new safety measures will prevent them from dropping significantly in cost, even as economies of scale kick in. Today about half of the cost of an EV battery pack lies in its "non-cell" portion, according to the National Research Council, and that number could go up if crashworthiness becomes a big issue.
Actually, lithium-ion is today's leader, which is why all the automakers are using it. Lithium-sulfur and lithium-air, two long-range contenders, are so far off that not much has been written about them yet. Here's a starting point on the challenges of Lithium-ion.
Chuck, thanks so much for the link. I want to cover this topic more from the materials standpoint, since there seems to be a lot of research going on, and I want to make sure I focus on what's most useful to our readers.
Many good comments by various folks! Here are my responses to a few:
Alexander: fuel cells are still ridiculously far from being a cost-effective automotive power source (using ANY fuel, but hydrogen is easiest to implement as far as fuel cells go). They are also still very low power density - so they need to be large if you want realistic horsepower. I think we will see some applications in fixed installations long before any automotive applications.
Jerry: I agree completely - while a "miracle" breakthrough battery would be nice...there are many things that can be done to reduce the energy needed to move the car and therefore make it easier to have a practical and cost-effective EV. see: http://www.edison2.com/blog/month/january-2012 These guys won the "automotive X-Prize" usign an ethanol burning engine...but now have an interesting prototype EV version. 114 mile range on 10.5 KWh's. However, I'll also point out that the low weight and drag of their design also gives awesome performance using fuel-burning engines too.
After researching all the related issues deeply, I find myself scratching my head about what problem the EV zealots think they are solving. First, modern engines are more efficient than most articles say - the Prius is ~38% efficient, and future versions will certainly acheive over 40%. That is higher efficiency than the average coal power plant, and in fact higher than the USA average grid efficiency (coal & natural gas to electricity conversion). The "elephant in the closet" is that EV's do not save energy vs. fuel burning cars (although they do shift from oil fuel to coal+natural gas).
A much more practical solution is to create a liquid synthetic fuel that will supercede gasoline, but leverage all the existing infastructure and vehicle technology. In the short-term, this could be synthesized from coal and natural gas (cut out the "middle man" of the power plants). Longer-term, solar-synthesized fuels or biofuels would create a renewable fuel that has all the conveniences of gasoline without the huge trade-offs of EV's.
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