Why not use high potential capacitors?

In summary: Higher energy density capacitors would require a higher dielectric constant, which is not possible with the currently available technologies.
  • #1
dE_logics
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I mean like...20KV or above...I've seen their energy density and specific energy is pretty high compared to batteries (I hope I'm right)...so why not use them for battery replacement in vehicles?
 
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  • #2
dE_logics said:
I mean like...20KV or above...I've seen their energy density and specific energy is pretty high compared to batteries (I hope I'm right)...so why not use them for battery replacement in vehicles?

Why not you post a link to a currently available 20kV+ capacitor that has energy storage capacity anything close to current battery technology.

Here's a link to some available high voltage capacitors. http://www.hivoltcapacitors.com/page1.html

Let's look at the largest in their 25kV range, part number PMR 250-504. It's volume is over 3L and its rating is 0.5uF 25kV DC working voltage.

Max energy storage is 1/2 C V^2 = 156 Joules.

For comparison LiPo batteries currently have volume energy densities around 300 W-h / L, so you'd store over 3000000 Joules in the same volume as the above capacitor!

Sure lower voltage supercapacitors will have higher energy density than the 25kv capacitor I linked, but even those currently have only about one tenth the energy density of what's available in batteries. The higher charge/discharge rate of the supercapacitors does give them some advantages which makes then useful in conjunction with a battery (as in a battery/supercapacitor hybrid).

Any dE_logics, please post a link to the currently available 20kV+ capacitor that you claim to have such good storage capacity compared to batteries. You've made the claim so please substantiate it. Personally I'll believe it when I see it.
 
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  • #3
dE_logics said:
I mean like...20KV or above...I've seen their energy density and specific energy is pretty high compared to batteries (I hope I'm right)...so why not use them for battery replacement in vehicles?

Perhaps you were thinking of high power density? http://www.nytimes.com/2008/01/13/a...ed=1&ref=automobiles&oref=slogin&oref=slogin" describes a hybrid electrical car that combines lithium ion batteries with ultracapacitors:
The ultracapacitors take up about as much space as the lithium ion batteries, although they store a total of less than one kilowatt hour. [...] In use, the capacitors function much like the water tank on a toilet. That reservoir let's the toilet get by with a small supply pipe, yet still delivers a large volume at once for flushing.
 
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  • #4
dE_logics said:
I mean like...20KV or above...I've seen their energy density and specific energy is pretty high compared to batteries (I hope I'm right)...so why not use them for battery replacement in vehicles?
The dielectric used for capacitors, especially supercaps, breaks down at high voltages.
So unfortunately you can't increase the capacity (by CV^2) by simply upping the voltage
 
  • #5
Ok...we don't have such capacitors...I was wrong.Thanks for clarifying.
 
  • #6
Worse than that - it's pretty much a fundamental feature of dielectrics that as the dielectric constant goes up the breakdown voltage goes down.
 

1. Why are high potential capacitors not commonly used in electronic devices?

High potential capacitors are not commonly used in electronic devices because they have a higher risk of failure and can be more expensive compared to lower potential capacitors. Additionally, many electronic devices do not require high voltage capacity and can function perfectly fine with lower potential capacitors.

2. Are there any advantages to using high potential capacitors?

One advantage of high potential capacitors is their ability to store and discharge larger amounts of energy, making them useful in certain applications such as power transmission and high voltage circuits. They also have a lower self-discharge rate, meaning they can hold their charge for longer periods of time.

3. What are the potential dangers of using high potential capacitors?

The main danger of high potential capacitors is the risk of electric shock. High voltage can be lethal, and proper precautions must be taken when handling high potential capacitors. There is also a higher risk of damage to the surrounding circuitry if the capacitor were to fail.

4. Can high potential capacitors be used in place of lower potential capacitors in all electronic devices?

No, high potential capacitors should only be used in applications that require high voltage capacity. Using them in place of lower potential capacitors in devices that do not require it can lead to unnecessary risks and costs.

5. How do I know if I need to use a high potential capacitor in my circuit?

If your circuit requires a higher voltage than what a lower potential capacitor can handle, then a high potential capacitor may be necessary. It is important to carefully consider the voltage requirements of your circuit and consult with a professional if you are unsure.

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