Using Ultra Capacitors to Replace Batteries

D from BC wrote in news: snipped-for-privacy@4ax.com:

Depends...capacitors can have high power density (they can deliver large amounts of current for a short time) but only very small amounts of current for longer periods. Batteries have high energy density, delivering small to medium (and sometimes high) currents for much longer periods.

If the current drain is >very< small, they can replace batteries in some instances; otherwise they can supplement batteries. Capacitors, properly designed and used, can endure constant and high charge/discharge rates, which batteries don't like.

If ultracaps could operate at substantially higher voltages, they could store much more energy but probably never as much as batteries. Both capacitors and batteries are improving, so I think we'll see more of both being used, often in tandem.

--Damon

The energy density of a common alkaline battery is 1000 times higher, and the cost is 100 times lower.

Only as a short term power source.

:)

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

Good answer.

D from BC wrote in news: snipped-for-privacy@4ax.com:

Maybe. Either for backup, or where their discharge is not critical. I have seen them used for RTCs, and in some shake flashlights.

Nope. Li-Po batteries can do those.

Yes and no. They cannot store as much energy, but they can charge and discharge much faster. There are certainly applications where an ultracapacitor could replace a battery. I have considered using them for a low drain application where they could be instantly recharged by plugging (very) briefly into an automotive power supply. It would require a capacitor with a low leakage current. A more come design would be to use both. Alkaline batteries can lose their charge very fast if they are subjected to a heavy current drain even for a short period of time. Using a capacitor along with the battery can extend the battery life since the capacitor can handle the large but short high current requirement.

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Gary Reichl>

It has been a few years since I used ultracaps, so somebody please correct me if this is no longer true, but when I used them the ESR was *very* high and thus the available current was quite low. The combination of a large capacitance and a high ESR made it so that I couldn't put a newly-built PWB on a test fixture and test the board's ability to hold data during a power failure -- the test was over before the ultracap had time to charge. I had to add a test to the burn-in fixture. Likewise on the discharge; short it out for a minute or so and find that it is still charged.

Wikipedia has an interesting energy density chart: [

A few selected items from the list:

ENERGY DENSITY IN MJ/kg:

------------------------------------------------------- Spring...........................................0.0003 Capacitor........................................0.002 Supercapacitor...................................0.01 Ultracapacitor...................................0.02 Lead-acid battery................................0.09?0.11 EEStor Ultracapacitor (claimed capacity).........1.0 NiCd Battery.....................................0.14-0.22 NiMH Battery.....................................0.22 Zinc-air Battery.................................0.40-0.72 Lithium ion battery..............................0.54?0.72 Wood.............................................6.0?17.0 Flywheel........................................l0.5 Lignite coal....................................14-19 Cowdung/Cameldung...............................15.5 Methanol........................................19.7 Ethanol.........................................30.0 Anthracite coal.................................32.5 LPG.............................................34.39 Diesel fuel.....................................45.8 Gasoline........................................46.9 Hydrogen.......................................143 Uranium-235 (nuclear fission)...........90,000,000 Hydrogen (nuclear fusion)..............300,000,000

That's what I would have said a few months ago. But a friend gave me a heads-up. They are now competing with batteries for things like electric cars.

Known for storing a short-lived jolt of electricity essential to the successful operation of electrical circuits in devices and appliances ranging from PCs to microwave ovens, cell phones, and televisions, the capacitor is in the midst of a major, ongoing upgrade of its energy storage capabilities. After nearly two centuries in which batteries have been the obvious choice for storing usable amounts of energy, high-end capacitors, known as ultracapacitors, are poised to challenge them in a growing range of applications.

A breakthrough technology is holding forth the promise of charging electronic gadgets in minutes, never having to replace a battery again, and dropping the cost of hybrid cars. Indeed, the technology has the potential to provide an energy storage device ten times more powerful than even the latest batteries in hybrid cars -- while outliving the vehicle itself.

Has anyone actually had a production or product sample from EEStor. I hear about this "unbelievable" capacitor technology they "have", but I am wondering at what stage of developement these guys really are in.

I have a product that desparately needs their device (if it works as rumor says), but have yet to see anything concrete from them. They don't even have a web site. Dave

Another EEstor Ultracapacitor story.

Please watch your attributions. I did not write any of the above.

Best regards, Spehro Pefhany

Sorry, I thought I had done so... You quoted AZ, and I quoted you quoting him (I think).

I could not access the original post, so I replied to yours.

Anyway, sorry for any confusion.

Ultra-caps can replace a car battery and start a gas burning auto engine, no problem!

Marc

mmmm....

10Farads/5 = 2Farads..

Isn't it something like 100Amps applied for about 1 second to start a car...??

D from BC

Why not. It would take somewhat 60000 capacitors like that to replace the standard 45A/h battery. This bunch will fit in a box size of a refrigerator and the cost will be the mere 1.8M$ :-)

Actually, it is a known fact that a big capacitor (>100,000uF) helps cranking if the battery is weak. The initial surge current required to shift the crankshaft from the dead stop is in the kiloamp range. So the capacitor supplies for it. However why messing with capacitors if you just need a good new battery.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

I don't know if this counts for "outperform" but a super/ultra cap is certainly capable of "replacing" the battery:

"T> Ultra capacitor example:

Pete Klammer, P.E. / ACM(1970), IEEE, ICCP(CCP), NSPE(PE), NACSE(NSNE)

Because maybe you're in the Arctic (where the cranking capacity of your regular battery is drastically reduced), and your armored personnel carrier needs to start *now* because you're under fire from an enemy. The few thousand dollars for a booster cap will seem like a real bargain.

Best regards, Spehro Pefhany

Maybe in Alaska.

The last I heard they were remarking on the purity of the materials they were producing.

Robert