EEStor Issued a Patent For Its Supercapacitor

An anonymous reader sends us to GM-volt.com, an electric vehicle enthusiast blog, for the news that last week EEStor was granted a US patent for their electric-energy storage unit, of which no one outside the company (no one who is talking, anyway) has seen so much as a working prototype. We've discussed the company on a number of occasions. The patent (PDF) is a highly information-rich document that offers remarkable insight into the device. EEStor notes "the present invention provides a unique lightweight electric-energy storage unit that has the capability to store ultrahigh amounts of energy." "The core ingredient is an aluminum coated barium titanate powder immersed in a polyethylene terephthalate plastic matrix. The EESU is composed of 31,353 of these components arranged in parallel. It is said to have a total capacitance of 30.693 F and can hold 52.220 kWh of energy. The device is said to have a weight of 281.56 pound including the box and all hardware. Unlike lithium-ion cells, the technology is said not to degrade with cycling and thus has a functionally unlimited lifetime. It is mentioned the device cannot explode when being charge or impacted and is thus safe for vehicles."

Comments

Much better than a battery for cars.

[Joce640k]

A capacitor has the ability for almost all braking energy to be fed back into it.

In stop-go traffic this could make a massive difference in mileage compared to a conventional battery.

Re:Cannot explode but can be used in cars?

[vlm]

Now its good that this thing allegedly won't explode while being charged

Welcome to the wonderful world of internal resistance.

Wikipedia files it under output impedance, although no one outside of maybe textbooks refers to it that way.

http://en.wikipedia.org/wiki/Internal_resistance

In summary, no perfect current or voltage sources exist. All power supplies can be modeled as a "perfect" supply with a series resistance.

In practice the difference can be huge. Short out an old fashioned 10 aH zinc copper gravity cell and nothing particularly interesting occurs due to its high internal resistance. Short out a 10 aH nicad, and good luck dodging the shrapnel.

Another amusing comparison, when NiMH batteries were very new, like in the late 80s, RC car racers like myself were impressed that they held around twice the charge of the old NiCd technology. However, the internal resistance was so high, that they didn't go so fast. I guess in the intervening decades NiMH now has a low enough resistance to use in RC cars, but that sure wasn't always the case.

Internal resistance has always been the problem for supercapacitors. I remember being quite disappointed when, as a kid a few decades ago, I bought one of those newfangled carbon based super caps, like 0.1 farad at 5.5 volts, and expected if a couple thousand uF made a shower of sparks when shorted out, 0.1 farad should make like an atomic explosion when shorted, however the internal resistance of the cap was like multiple ohms so it didn't even spark. I vaguely remember that once charged it ran a LED a long time though.

The problems super caps always had (until now?) is you need a ultra high conductivity for the plates to get a low internal resistance and a ultra low conductivity for the dielectric (not dialectic, that's another story) to get low leakage currents, and both have to be compatible with each other (from an electrical standpoint, sodium metal foil and ultra purified water sounds like a good capacitor design, but from a chemical standpoint, maybe not so good. Chlorine is probably an even better insulator than water in this application). Finally it would be nice if it were made without toxic waste like PCBs or beryllium oxide insulators (both of which have been used in electronics applications in the past). And then there's minor little things like mechanical stability, manufacturing problems, and material sources like tantalum. Their claim to have worked around all those problems is what makes this patent very impressive, if true.