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EEStor Promises Revolutionary Energy Storage Technology for Electric Cars

EEStor Promises Revolutionary Energy Storage Technology for Electric Cars

Written by Bryan Johannsen

What is EEStor?If you follow the growing electric car market you've almost certainly heard the term EEStor before. EEStor is a company out of Cedar Park, Texas that is claiming to have revolutionized energy storage.

In the most general terms EEStor's technology is a replacement for the chemical battery. It is a capacitor that allows for quickly storing large amounts of energy with a short charge time. If it comes to fruition this could eliminate both range and charge time issues for electric cars. Imagine a car that could travel 300 miles at highway speeds and could fully recharged in minutes. The technology also wouldn't have it's storage capacity degraged by deep cycling, time or temperature. Three problems with all current batteries.

EEStor EESU vs. Current Battery Technology

Weight (lbs)3001,7163,646752
Volume (sq. inch)4,57117,88143,0655,697
Discharge Time.02%/30 Days5%/30 Days1%/30 Days1%/30 Days
Charge Time3-6 Minutes3 or more hours3-15 Hours3 or more hours
Life Reduced with Deep Cycle UseNoneHighVery HighHigh
Hazardous MaterialsNoneYesYesYes
Temperature Effect on StorageNegligableHighVery HighHigh

EEStor holds about 20 patents with the US patent office (President & CEO Richard Weir is co-inventor on at least two of them), though to date no energy storage device using the capacitor technology has been demonstrated to the public nor verified to work from sources outside the company. EEStor's EESU (Electrical Energy Storage Unit) launch has been delayed from 2007 to 2008 and now 2009.

ZENN owns 11% of EEStorZENN Motor Company, maker of the ZENN Neighborhood Electric Vehicle, is heavily invested in EEStor and owns nearly 11% of the company. Venture capital firm Kleiner Perkins Caufield & Byers invested $3 million in the company in 2005 but there are no reports of further investments. Adding some validity to EEStor's claims, defense industry giant Lockheed-Martin signed an agreement for exclisve rights to the technology for military and homeland security use. To date Lockheed-Martin has not invested any money in the company.

ZENN has a lot of it's future invested in EEStor, the cityZENN is a highway capable electric car that will be among the first vehicles to use the EEStor system. With an approximate 250 mile range and 3 minute charge time it would completely revolutionize the electric car industry.

Energy Storage Comparison (Prices in USD)

Storage Tech
Energy Density (Wh/kg)
Cost ($/Wh)
Cost for 52 kWh Storage Pack
Nickel Zinc60$0.60$0.67$0.73$31,200$34,580$37,960
Nickel-Metal Hydride80$1.20$2.40$3.60$62,400$124,800$187,200
Lithium Ion140$.050$.075$1.00$26,000$39,000$52,000

Some experts have dismissed EEStor's claims as unrealistic and Jim Miller, a capacitor expert who visited EEStor to evaluate the technology for potential investors, stated he was skeptical because of current leakage seen at high voltages and because there should be microfractures from temperature changes. He stated "I'm surprised that Kleiner has put money into it."

EEStor is keeping everything close to the vest though so until they put on a public demonstration or we see a working prototype of the cityZENN we won't know for sure.

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