Advanced Capacitor Theory

[safe]

Advanced Capacitor Theory

I'm starting to think that the battery as we know it is a dinosaur already. The super high powered capacitor is a better way to go because it never wears out and can be charged very fast without any negative consequences. The only negative about capacitors is that they can potentially be dangerous.

What I want to do here is (like with previous battery discussions) to go through the basics of capacitors and work forwards so that we can attain a level of mastery of the topic.

This is a "learning thread"...

 

[safe]

The Basics

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

Capacitance

The capacitor's capacitance (C) is a measure of the amount of charge (Q) stored on each plate for a given potential difference or voltage (V) which appears between the plates:

Stored energy

As opposite charges accumulate on the plates of a capacitor due to the separation of charge, a voltage develops across the capacitor due to the electric field of these charges. Ever-increasing work must be done against this ever-increasing electric field as more charge is separated. The energy (measured in joules, in SI) stored in a capacitor is equal to the amount of work required to establish the voltage across the capacitor, and therefore the electric field. The energy stored is given by:

 

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Observation

It just looks to me that the most obvious way to get more power is to increase the voltage. The EEStor approach does that and it seems that the higher the voltage the more power you store for the same surface area.

 

[safe]

Series and Parallel

The current through capacitors in Series stays the same, but the voltage across each capacitor can be different. The sum of the potential differences (voltage) is equal to the total voltage. Their total capacitance is given by:

Capacitors in a Parallel configuration each have the same potential difference (voltage). Their total capacitance (Ceq) is given by:

 

[safe]

High Voltage Dangers

Above and beyond usual hazards associated with working with high voltage, high energy circuits, there are a number of dangers that are specific to high voltage capacitors. High voltage capacitors may catastrophically fail when subjected to voltages or currents beyond their rating, or as they reach their normal end of life. Dielectric or metal interconnection failures may create arcing called an arc fault, within oil-filled units that vaporizes dielectric fluid, resulting in case bulging, rupture, or even an explosion that disperses flammable oil, starts fires, and damages nearby equipment, called flash - melt down, Rigid cased cylindrical glass or plastic cases are more prone to explosive rupture than rectangular cases due to an inability to easily expand under pressure. Capacitors used in RF or sustained high current applications can overheat, especially in the center of the capacitor rolls. The trapped heat may cause rapid interior heating and destruction, even though the outer case remains relatively cool. Capacitors used within high energy capacitor banks can violently explode when a fault in one capacitor causes sudden dumping of energy stored in the rest of the bank into the failing unit. And, high voltage vacuum capacitors can generate soft X-rays even during normal operation. Proper containment, fusing, and preventative maintenance can help to minimize these hazards.

High voltage capacitors can benefit from a pre-charge to limit in-rush currents at power-up of HVDC circuits. This will extend the life of the component and may mitigate high voltage hazards.

 

[safe]

EEStor

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

These units use barium titanate coated with aluminum oxide and glass to achieve a level of capacitance claimed to be much higher than what is currently available in the market. The claimed energy density is 1.0 MJ/kg (existing commercial supercapacitors typically have an energy density of around 0.01 MJ/kg, while lithium ion batteries have an energy density of around 0.54–0.72 MJ/kg).

EEStor's technology, described in its patent, involves sintering very small grains of coated barium titanate powder into a bulk ceramic. The process is designed to eliminate the pore space left by sintering. Barium titanate crystals have an extremely high permittivity; however, voids allow current to arc through the dielectric (voltage breakdown), causing the capacitor to self-discharge. By eliminating the voids, the bulk ceramic has properties similar to that of individual barium titanate crystals. To keep costs down, the sintering occurs at low temperatures, enabling the manufacturer to use nickel electrodes instead of more expensive platinum electrodes.

The capacitance in the patent is 31 Farads. To achieve such a high energy density the capacitor has a very high breakdown voltage and uses an operating voltage of 3,500 V. In the absence of dielectric saturation the formula for stored energy of a capacitor is 1/2cv2, which gives a total energy storage of 189 MJ or 52 KWHours.

Critics have suggested that measurements of the permittivity of the Eestor components were made only at low voltage and that permittivity would have been much lower at the operating voltage of 3,500 V due to the phenomenon of dielectric saturation. However, the latest version of the Eestor patent[12] contains measured permittivity at 85°C averaging 19,869 at an unspecified voltage, 19,837 at 3,500 V and 19,818 at 5,000 V, demonstrating that little dielectric saturation occurs below 5,000 V.

 

[Toorbough ULL-Zeveigh]

a battery has the benefit of being non-fiction.
well, some of them anyways.

 

[safe]

a battery has the benefit of being non-fiction.

True, but the idea here was to prepare the way intellectually for where things might go. All the references were from Wikipedia.

I like the idea of something that doesn't wear out after a few years. If something wears out then you have to include that as a "cost" in the price of the fuel. Basically you want an up front cost that is fixed (the fuel container) and then just have to pay for the fuel which in the case of electricity is pretty cheap.

All the other ideas I've heard (and the battery that I've been using for the last three years) point me towards wanting a true solution to the problem. Seems to me the battery is just a temporary half step.

My SLA battery is dying of old age and not really because of usage. All the chemistries seem to die off after 3-5 years... even the latest stuff is unproven to go beyond that.

"Shelf Life" is far more important than "Cycle Life".

 

[EMF]

OR instead of trying to unravel the mysteries ... we could wait for them to go on sale to the public and buy one. If they ever do.

I doubt that if one came up for grabs at a good price, I'd need to be "prepared intellectually" first.

 

[safe]

OR instead of trying to unravel the mysteries ... we could wait for them to go on sale to the public and buy one. If they ever do.

I doubt that if one came up for grabs at a good price, I'd need to be "prepared intellectually" first.

Well... my observation of how things work is that they will produce certain things that solve some of the problems and over time they will modify them as they learn new things. The "final product" that you might hope for will be years from now after all the "bleeding edge" products have been weeded down to the winners.

It's a Darwinian process like the "Housing Bubble" America just went through where the wise will find ways to have exploited it and the foolish will become victims and be forced out on the streets through foreclosure.

Things never change... they just repeat again and again... the common man usually picks the wrong choice...

If you were to have a choice of investing in batteries or ultracapacitors which would you choose?

Which option is the natural winner if it's technically possible?

If both options are technically possible I don't think there is any doubt that the ultracapacitor is the easy winner...

 

[TylerDurden]

the idea here was to prepare the way intellectually for where things might go.

Keep doing that and you'll go blind.

 

[safe]

The fact that a car will be produced soon that is going to use the EEStor technology means that this is being taken seriously. If there was no activity and nothing but theory then I might agree that this would be nothing but mental masturbation, but I think this is real. This is the way things will need to go because the idea of replacing a $10,000 battery every 5 years in your car is unacceptable.

Think about it...

We've got people who are blowing $1,000 every few years for packs that are just big enough to push a little bicycle around... if you want to scale up to a car you need to either "fix" the "Shelf Life" problem or switch technologies from battery to capacitors.

The only real negative is safety... 3,500 volts is a scary, scary, scary amount of voltage to have in a car and if and when they break open in an accident it's going to be really ugly. But if enough safety is placed into the design of the protective packaging then it's worth it.

I would suggest a "monocoque" design:

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

...because the ultrcapacitor would itself be able to add some structural strength to the frame.

 

[Toorbough ULL-Zeveigh]

The only real negative is safety... 3,500 volts is a scary, scary, scary amount of voltage to have in a car and if and when they break open in an accident it's going to be really ugly. But if enough safety is placed into the design of the protective packaging then it's worth it.

Which is why I will be very surprised if this product will see the light of day.
If it is ever released to the public I would snap it up quick because it will quickly be classed as a dual use commodity.
Meaning that the same hi power source that can move a car can also be applied to labomba.
In fact all of the new battery tech is being held back while they figure out ways that can't be bypassed so it can only be used for it's intended purpose.

Never wondered why after all this time you can't buy LiCo in a convenient grenade size hi rate discharge d-cell?
Saft lists even larger sizes that are supposedly available, but when you approach them they give you an impossible minimum quantity.
Even when you call their bluf & get a group buy together they up the figure into the millions of dollars.
Message is clear, not for public consumption, military/industrial only & neither will ultramegahyper power density caps.
Hope I'm wrong.

 

[mcstar]

Has anyone given any thought as to how we can stepdown/switch 3500V to make it useful to our <100V motors? For that matter, does anyone have any idea how to build a capacitor charger that can step 120VAC mains UP to 3500V DC? I suppose a motor powered Van-de-graff generator could do it, but it might take hours to build up enough charge. Do they even make FETs or similar that can switch voltage that high? It seems to me anything you connected to that capacitor would need to be able to handle insane amounts of current (potentially) and be designed to handle the potential. Anyone how much a 3500V fuse costs? Even at 1000V we are talking about industrial quality power distibution products with very high price points. Not to mention that you need a certified electrician that specilizes in high voltage to even work on the system. Seems a bit far fetched for the average e-Biker.

 

[Link]

Has anyone given any thought as to how we can stepdown/switch 3500V to make it useful to our <100V motors? For that matter, does anyone have any idea how to build a capacitor charger that can step 120VAC mains UP to 3500V DC? I suppose a motor powered Van-de-graff generator could do it, but it might take hours to build up enough charge.

Don't know about down, but charging up could easily be done with loads of different things. Voltage multipliers and flybacks come to mind. HV is not that hard to get, really.

Down could be perhaps done with charge series of caps/discharge in parallel sort of thing.

Do they even make FETs or similar that can switch voltage that high?

Good point. I haven't really looked, but I don't think they make a lot of them. EEStor might have to have them made.

Anyone how much a 3500V fuse costs?

A quick Googling brings up some Bussman fuses for between $17 and $140. But even the $17 is rated for 8A and 27kV. We don't need that much.

Even at 1000V we are talking about industrial quality power distibution products with very high price points. Not to mention that you need a certified electrician that specilizes in high voltage to even work on the system. Seems a bit far fetched for the average e-Biker.

Perhaps, but they aren't ridiculously expensive (and price would come down if sold en masse), and generally aren't disposable parts.

And I'd be working on it, anyway. Assuming the thing is totally discharged when you're working on it, you should be fine.

Meaning that the same hi power source that can move a car can also be applied to labomba.

*dances*

Para bailar la bamba!

 

[Dalecv]

This is pure speculation but I doubt that EESTOR would put a product on the market that would allow a bunch of amateur hobbyist, without bypassing safeguards, to blow themselves up and generate negative press on the product. I would think such a high voltage capacitor system would be put on the market with built in electronics so that the charging input would be 110 or 220 volts and the output voltage would be appropriate to the equipment that it is to be installed in.

This also may be why A123 batteries are less expensive when purchased in an assembled product.

 

[safe]

It might be interesting to do the math on an electric bike and see exactly how much is required.

How about a six pound, 2650 volt, one Farad capacitor?

I finally got around to running the math...

If you increase the capacitor size from one to ten then the voltage of the capacitor goes to 830 volts.

Energy equals one half the capacitance times the voltage squared.

 

[fitek]

Anyone here tried to BUY a super capacitor? They cost an arm and a leg. Then you need electronics to charge and discharge. Charging a capacitor is inefficient without some work.

 

[Link]

Anyone here tried to BUY a super capacitor? They cost an arm and a leg. Then you need electronics to charge and discharge. Charging a capacitor is inefficient without some work.

Technically. I have a couple lying around. Yah, they cost me quite a bit, relatively. Something like $400w/hr last time I figured.

But, charging is VERY easy. I just hook it up with two slightly discharged NiMH batteries. Physics takes care of the rest :wink:.

Getting stable output is another matter, though. You need either electronics that can take a wide voltage range or a way to modulate the output voltage. I am very interested in what exactly EEStor uses to take care of this problem.

 

[safe]

Oops... managed to garble my older post... oh well... :?

How about a six pound, 2650 volt, one Farad capacitor?

I finally got around to running the math...

If you increase the capacitor size from one to ten then the voltage of the capacitor goes to 830 volts.

Energy equals one half the capacitance times the voltage squared.

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

 

[Toorbough ULL-Zeveigh]

sorry to pollute advanced capacitor theory with basic capacitor theory (there's 22 volumes of it), but are you familiar with the discharge profile on a cap?
Give you a hint, it's not flat.
You (safe) have posted that you hate it when the voltage drops off on your SLA's.
You're gonna like it even less on a capacitory.

BTW 3 kg is 6.6 lbs.
But what's a little cheating amongst friends.

 

[Link]

How about a six pound, 2650 volt, one Farad capacitor?

How is that safer than 3500V now?

If I'm gonna take a dangerously high voltage capacitor, I'm gonna at least pick the smaller, higher-voltage one.

 

[safe]

...are you familiar with the discharge profile on a cap?

BTW 3 kg is 6.6 lbs.

Well that's something we all want to know about. Obviously EEStor has some way to slowly release the energy and we all want to know more. If anyone finds an article about what is probably a closely guarded trade secret be sure to post a link.

As for the round off... yeah, the kg was 2.80 and the lbs value was 6.16.... rounded off it's 3 and 6....

 

[safe]

How is that safer than 3500V now?

You would have to increase the capacitance by ten times to get the voltage down to 830 volts. Basically think of it from the power-to-weight standpoint... the higher the voltage you use the less material is required to hold the energy, but the higher stress that material must handle.

In some far off "Star Trek" kind of reality one might hope for insanely high voltages like 10K volts packed into something really small... power-to-weight... with the capacitor you can tweek it.

Imagine people back in the 1920's looking at the turbocharged power that has been produced in one liter engines. They tried doing things like that back then but it wasn't until recently that they set such high levels of performance. (and then banned it in Formula One in 1989)

 

[Link]

How is that safer than 3500V now?

You would have to increase the capacitance by ten times to get the voltage down to 830 volts.

:lol: How is that much safer than 3500V now?