In a traditional ultracap, that permittivity is given a rating of 20 to 30, while EEStor’s claim is 18,500 or more–a phenomenal number by most accounts. “This is a very big step for us,” says Weir. “This puts me well onto the road of meeting high-volume production.”
Jim Miller, vice president of advanced transportation technologies at Maxwell Technologies and an ultracap expert who spent 18 years doing engineering work at Ford Motor, isn’t so convinced.
“We’re skeptical, number one, because of leakage,” says Miller, explaining that high-voltage ultracaps have a tendency to self-discharge quickly. “Meaning, if you leave it parked overnight it will discharge, and you’ll have to charge it back up in the morning.”
He also doesn’t believe that the ceramic structure–brittle by nature–will be able to handle thermal stresses that are bound to cause microfractures and, ultimately, failure. Finally, EEStor claims that its system works to specification in temperatures as low as -20 °C, revised from a previous claim of -40 °C.
“Temperature of -20 degrees C is not good enough for automotive,” says Miller. “You need -40 degrees.” By comparison, Altair and A123Systems claim that their lithium-ion cells can operate at -30 °C.
Burke, meanwhile, says that there’s a big difference between making powder in a controlled environment and making defect-free devices in a large quantity that can survive underneath the hood of a car.
“I have no doubt you can develop that kind of [ceramic] material, and the mechanism that gives you the energy storage is clear, but the first question is whether it’s truly applicable to vehicle applications,” Burke says, pointing out that the technology seems more appropriate for utility-scale storage and military “ray guns,” for which high voltage is an advantage.
Safety is another concern. What happens if a vehicle packed with a 3,500-volt energy system crashes?
Weir says the voltage will be stepped down with a bi-directional converter, and the whole system will be secured in a grounded metal box. It won’t have a problem getting an Underwriters Laboratories safety certification, he adds. “If you drive a stake through it, we have ways of fusing this thing where all the energy is sitting there but it won’t arc … It will be the safest battery the world has ever seen.”
Regarding concerns about temperature, leakage, and ceramic brittleness, Weir did not reply to an e-mail asking him how EEStor overcomes such issues.
Nonetheless, the company has some solid backing. Its board has attracted Morton Topfer, former vice chairman of Dell and mentor to Michael Dell.
The company is also backed by Kleiner Perkins Caufield & Byers, a venture-capital powerhouse that has an impressive track record: it made early and highly successful bets on Google, Amazon.com, and Sun Microsystems, among others. Whether EEStor can translate that success to the energy sector remains to be seen.
“I’m surprised that Kleiner has put money into it,” says Miller.
Weir maintains that his company will meet all of its claims, and then some. “We’re not trying to hype this. This is the first time we’ve ever talked about it. And we will continue to meet all of the production requirements.”