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richhagen

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Ultracapacitor Project
« on: February 10, 2015, 06:35:24 PM »
I have a bank of ultracapacitors which were commercially made.  Most of them are made by Maxwell Technologies, however, I have a few from a company called Ioxus as well.  I have them configured in series/parallel such that I have about 600 Watt hours of storage between a high voltage of 60V and a low voltage of 32V.  I generally consider the bank to be a buffer as 600 Watt Hours does not go very far.

 

The nice thing about capacitors is that they are essentially maintenance free.  They do not suffer damage if discharged to zero volts, I am not sure about reverse polarity, although in testing they seem to have a diode internally or something that limits reverse polarity to about a half a volt.  They can dump an incredible amount of power, in my setup, limited only by the cable and connectors and of course the fuses.  They could put out far more instantaneous power than I could imagine using at this point, all be it for only a short time.

 

They seem to have a higher self discharge per watt hour of storage than batteries, but not to the point that they are not effective at providing power overnight.  They do require some circuitry to ensure that they do not get into an over voltage condition which is reported to damage them.  Because of the series arrangement they have some vulnerability to this if not protected.  I have yet to experience detectable damage, although in testing and temporary set ups I have over charged a few.

 

The downside is that to if you wanted to use them as primary storage, they are way too expensive.  I think that new, each 3000 Farad, 2.7V capacitor would be about $50 US.  In my setup I use 96 of them per 178 Watt Hours of usable energy storage.

 

If only they, or something that could function similarly, could be had at a much lower price.  The commercial units are optimized to provide bursts of power for functions such as regenerative braking in vehicles and other such high amperage usages.  I don't need the ability to put out the massive power that these things can put out, I would only be drawing it at a few thousand watts max at present.

 

The first electric double layer capacitors that  I saw were the button cell units of about a farad at 5.5 volts.  They have activated carbon electrodes separated by an ion permeable membrane and generally used a sulfuric acid solution as the electrolyte.

 

Sulfuric acid tends to be rather corrosive to most metals.  I recalled that Edison chose an electrolyte of potassium hydroxide for his batteries on the basis that it would preserve the battery materials better than an acid.

 

A little checking revealed that there are a few companies making alkaline ultracapacitors, KA Power is one, and they seem to be marketed in packages of about 30 Watt hours and optimized again for high current, and in this case utilized to help truck engines start, especially in cold weather.  They also appear to use asymmetrical electrodes to get more current out of them.

I have done a bit of electroplating in the past as well as built a small unit to generate hydrogen by electrolysis.  I recall that stainless steels can generally withstand a few volts before they pit and corrode due to galvanic corrosion when used in electrolytic cells.

 

So, I got to thinking, why not coat some stainless steel mesh with activated carbon and separate them with a cloth that won't break down in alkaline solution and see what happens.  I searched online to see if anyone else had done this and did notice one fellow had posted a video online along similar lines using a tic tac box and some plaster mesh, which I don't think was stainless.  He reported a 1.2 Volt 400 farad capacitor as his result.

 

Encouraged I drafted my son to help out and we ordered some stuff and set off to the store.  We  bought the following items:

 

Activated Carbon

This is activated carbon sold for aquarium filters, probably not the perfect activated carbon for this project, but it should still yield significant surface area per unit of mass.

Stainless Steel Mesh

It is of a size that would be suitable for a 100 micron sieve, We probably could have used larger wire size but it was what I found on E-bay in 316 grade.

Sodium Hydroxide

Sold as drain cleaner, this was obtained from my friend Paul down at Chiarugi hardware on the end of my block.

Binding Agent

We used Epoxy as a binding agent as I am thinking that if I mix enough carbon in it will make a conductive paste that we can coat with more activated carbon.  We wanted a longer hardening time, but the five minute epoxy was all we found stocked.

Container for a small experiment

We used PVC pipe as it is relatively inert and readily available at the hardware store.  We got one inch size as it seemed about the right size for a small experiment that might fail anyway.

End caps

PVC end caps for the one inch pipe

PVC cleaner

wanted to make a good joint so we got cleaner, as near as I can tell this stuff is mostly acetone.

PVC Glue

PVC glue

So, we started off cutting three inch long pieces of  the three inch pipe. 

Then we cleaned one end and glued end caps onto one end of each piece.

Next we got a blender (hope we don't get in trouble with a certain someone for what we did with it)


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richhagen

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Re: Ultracapacitor Project
« Reply #1 on: February 10, 2015, 06:41:13 PM »
We loaded in activated charcoal and ground it to a fine powder.  We then used a small screen strainer to sort out any larger particles or clumps remaining.

Next we cut the 316 stainless screen to make our plates for our capacitor.  We found that about a 3.75 inch by .75 inch rectangle with a .5" by 1" notch cut out at the top would fit into our tube, with a tab on the top to poke out a hole in the cap.

We made 12 thinking that we would try to fit four plates in each of three tubes.

Now we were ready for the messy part. 

We mixed a small amount of the epoxy and then added powdered activated carbon until it had the consistency of creamy peanut butter.  This was smeared over both sides of the screen, forming a film, maybe about one sixteenth of an inch.  more powdered carbon was poured over both sides.  I had a couple of pieces of one inch wide by one quarter inch thick bar stock which we wrapped in plastic wrap.  We then put a thin layer of powdered activated carbon on one and set our 'plate upon that, we then covered the plate with another thin layer of activated carbon and placed a second wrapped piece of bar stock on top of that.  This was then clamped tightly.  We used the c-clamp to start, but found it to be uneven in applying pressure, so we switched to using my drill press vise which was conveniently one inch tall. 

This was a bit tedious as we had to make the plates one at a time.
Once hardened, the plates were removed and trimmed to the dimensions of the screen as some of the epoxy/carbon had extruded from the pressing.  (Sorry, we forgot to take pictures of these finished plates)

Three holes were drilled in the cap, two a half an inch apart for the tabs on the screen plates, and an additional hole for adding the electrolyte.

 

For a separator, I used a roofing fabric underlayment cloth, the polyester based cloth was cut to a size slightly larger than the plates and four the plates were alternated such that tow tabs were on each side.  The tabs were fit through the cap and the whole package was carefully inserted into the pvc pipe tube.

 

We did not glue the top caps on, instead they were sealed with petroleum jelly, to seal out the atmosphere, but such that they could be taken apart if needed.  A check was made to see that no current was conducted between the alternating plates.

The electrolyte was carefully mixed.  We used 5 molar solution, as was used in the tic-tac version We had seen posted on Youtube.  In the case of sodium hydroxide, sodium has a molecular mass of 23, Oxygen 16, and Hydrogen 1, so one mole of Sodium Hydroxide would have a mass of 40 Grams.  Five molar concentration would be a liter of solution with 200 grams of sodium hydroxide in it.  We happened to have a 500 mL beaker handy, so we measured out approximately 100 grams of sodium hydroxide (which we measured on a balance against 40 new U.S. pennies because U.S. pennies newer than 1983 weigh 2.5 grams each) I then slowly added this to 300 mL of distilled water in the beaker.  The beaker became hot as the sodium hydroxide dissolved.  We then added distilled water to bring the level to 500 mL.  This was allowed to cool a bit, but not completely because we were a bit impatient to see if this worked.

 

As in the youtube video a syringe was used to add the electrolyte to the pvc tube.  We put in fluid until it over flowed and wiped away the excess.  We wore gloves and goggles while working with the sodium hydroxide.   I would imagine that it would damage your eyes if you managed to get it in them.   Epoxy was then mixed and sealed the three openings.

 

Power was then connected to the leads, using a nickel cadmium rechargeable battery as the power source.

 

At first, when the power was disconnected, the capacitor discharged almost completely.  Over time, however, it began holding more voltage.  By the next day we were able to connect the three in series and light a blue LED.  It would maintain about 3.3 volts.  We rigged two diodes in series to limit the voltage to about 1.1 volts across each cell as a protection measure, as we had over charged one of the caps a bit when charging them in series, but mounting them on the caps with the stainless screen leads proved difficult at this point.  Thus far we have just used jumper leads with alligator clips.  We will have to work on that.  Once it has been run a bit, we will make a measurement of the capacitance.


At any rate, the results thus far are promising, but there are a lot of things to work out, optimum screen mesh size, optimum thickness of carbon layer, the efficiency of the device in that what percentage of energy that you put in charging it do we get back, self discharge rate, and probably a better separator as I am not sure that the polyester cloth will survive the long term in the alkaline solution.
 
If we are not now barred from the kitchen, we may make more of these, say 16 total, similar to the three made thus far, to put in series to charge off of a small solar panel to run an LED light at night as a test platform.  Although the energy density is low as is the power density as well, the ingredients are cheap and if it can last a number of years it might prove to be a viable option where space is not a problem.  I can imagine five gallon buckets, say 60 or more in series and a few strings in parallel run as a 48V system where space is not a problem, say for a farm for example.  They would need to have a long service life, but since they are capacitors and not batteries, this may be possible. 

At any rate this was a fun start. 
 
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gww

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Re: Ultracapacitor Project
« Reply #2 on: February 10, 2015, 08:09:47 PM »
Thanks for posting
gww

DamonHD

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Re: Ultracapacitor Project
« Reply #3 on: February 11, 2015, 03:58:22 AM »
Yes, you're getting me all excited about super/ultra caps again!

(This time my excuse is "energy harvesting"...)

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electrondady1

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Re: Ultracapacitor Project
« Reply #4 on: February 11, 2015, 08:20:46 AM »
your post is just a tease .
you post pictures of a jar of Vaseline , glue, and of a blender but not a hint of how you assembled the pieces you made?

 i had thought of attempting a capacitor but it involved rolls of aluminum foil and paper towels

Bruce S

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Re: Ultracapacitor Project
« Reply #5 on: February 11, 2015, 10:22:46 AM »
Rich;
 good seeing you post again!!
Could you give an estimate of the total $$ involved of just those 3?
I had read , that it takes a few full discharge/charges before the caps settle into a known capacitance.
Best of Luck!
Bruce S
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richhagen

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Re: Ultracapacitor Project
« Reply #6 on: February 11, 2015, 05:46:50 PM »
We are planning to make 13 more identical to the first three and I have begun getting the supplies we did not need.  I will try to post pictures of the plate making process, and the layering of the plates and separators prior to putting them into the tube this time.  I think part of the reason I did not get those photos in was that it got messy with the epoxy and the carbon at that point.

I will also try to give a detailed list of the parts and costs.  I think the container is at least half of the cost in this R and D version.  But I'd better get back to work for now so that the R&D department can have the cash on hand for the parts needed.  I will plan to post again within two to three days with photos and some preliminary stats. 

Rich
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bart

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Re: Ultracapacitor Project
« Reply #7 on: February 11, 2015, 06:55:51 PM »
Thread lurking on this project!

richhagen

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Re: Ultracapacitor Project
« Reply #8 on: February 12, 2015, 05:43:43 PM »
I did not make much progress before work today.  I did cut the 1" pipe pieces for the 13 additional units.  I also started measuring the self discharge characteristics of one of the capacitors as I did laundry and other tasks.  It does not seem that encouraging in regard to the self discharge, but I do think there is room for improvement in keeping the plates isolated, any conductivity between them is essentially like having a load resister across the capacitor.  The results are encouraging enough that I have loosened up the R&D budget a bit to see this through.  At any rate, here are the first five hours of data:
8630-0
I will make a similar chart of its discharge under a known load in the coming days which will give me the units capacitance.
I think this may qualify as the cutting edge of low technology regarding super capacitor research, or then again, maybe just the dull edge of low tech. 

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Mary B

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Re: Ultracapacitor Project
« Reply #9 on: February 13, 2015, 04:59:59 PM »
I am following the use of graphene in super capacitors an din batteries. Very promising results.

dnix71

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Re: Ultracapacitor Project
« Reply #10 on: February 13, 2015, 10:14:45 PM »
https://www.youtube.com/watch?v=z3x_kYq3mHM This guy has done a series on replacing automobile start batteries with super caps.
It works.

MattM

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Re: Ultracapacitor Project
« Reply #11 on: February 14, 2015, 12:00:04 AM »
I would be looking for a guy with a stomp shear and a sheet of mill finish aluminum or stainless.  Cut you a bunch of square blanks for your project.  Aluminum that is painted would work, too.  You can buy rolls of the stuff at a hardware store and cut it yourself if you cannot find the stomp shear.  (Any aluminum stock below .040 can be scored with a box cutter and it will snap on the cut when you fold it on the line.)  Keep it simple.  Keep it stupid.  Most of all keep it working.

richhagen

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Re: Ultracapacitor Project
« Reply #12 on: February 14, 2015, 10:19:12 AM »
Morning, Dnix, I wouldn't want to accidentally leave the dome light or the accessory radio on for a few minutes with only a few 350 Farad Boostcaps in series.  You don't have much stored energy in that pack.  The ones I have here do not compare very well with those Maxwell units.  This is definitely a lot lower in both power and energy density than their unit. 

I believe that sheet metal would work, I am not sure about the long term adherence of the carbon, also, aluminum would not work with a sodium hydroxide electrolyte that I have in this one as they would react, though stainless could work and would probably be more conductive than the mesh. 

Here are updated self discharge parameters for the initial design.  This will need improvement, but I do have some ideas on this regarding the separation of the plates. 
8631-0
This does not look as bad once you get below .9 volts or so, but when you consider that the stored energy is proportionate to the square of the voltage, the issue becomes a bit more clear. 
8632-1
I have a bit of time to push this project forward, so back to work for me. 

 
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electrondady1

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Re: Ultracapacitor Project
« Reply #13 on: February 14, 2015, 03:10:26 PM »
it doesn't seem to bad for something home made for the first time.
50 % after  25 hrs.

dnix71

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Re: Ultracapacitor Project
« Reply #14 on: February 14, 2015, 05:50:35 PM »
Piggybacking a boost cap array to a lead acid battery would allow a weak lead battery to start a vehicle. Even 10 volts is enough to start a car if the current is there.

It would also be a good place to put regenerative braking energy from a hybrid or plugin electric, or use as a start battery for vehicles that shut off at a stop to save fuel.

richhagen

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Re: Ultracapacitor Project
« Reply #15 on: February 14, 2015, 06:42:42 PM »
I would agree Dnix, I think it would work wonders to help an almost dead battery that can no longer put out the current to start the vehicle. 

Electrondady, that 50% or better was actually my initial target for a solar cycling.  It would probably be pretty poor in comparison to batteries at that level, but I could make it function with solar lights and such.  In looking at some old research I found online, which was on mostly acidic electrolyte super caps, they tend to break the self discharge down to three categories, conductivity between the poles, impurities in the carbon, and impurities in the electrolyte.  I did use distilled water that I distilled in borosilicate lab equipment I have here, but the lye and the activated carbon were just off of the shelf.  I am pretty sure I have some issues with stray carbon particles adding to conductivity, and my separator, which was snow roof systems contouring seam tape, is porous enough for the ground up carbon particles to lodge or probably even pass through. 

I am working on the next 13 to make a series string of 16 or so, but I will probably change the design of one or more to test the changes.  Progress is slow in that I had to distill a batch of water today.  I will try to photograph the plate making and stacking process I used as I missed those parts the first time around.  I have acquired some hepa vacuum bags that are made with a polypropylene fabric that I am thinking might make a good separator and help reduce conductivity between plates that might be caused by stray carbon particles without impeding ion transport.  Anyway I will give it a shot. 
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MattM

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Re: Ultracapacitor Project
« Reply #16 on: February 15, 2015, 12:11:25 AM »
Why not just use tool dip?  You can get it at hardware stores to either dip or brush on a coating.  That way you can be sure that the electrons only pass via induction.  One $10 can would be enough for more than one project.

MattM

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Re: Ultracapacitor Project
« Reply #17 on: February 15, 2015, 12:30:40 AM »
I guess my recollection of how capacitors work is faulty.  I thought the idea was to keep the plates separate from the anode, which made them bi-directional for lack of a way to stop flowing back out the way it originally entered.  I need to relearn what is going on here.

richhagen

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Re: Ultracapacitor Project
« Reply #18 on: February 15, 2015, 11:04:16 AM »
Matt, in a basic standard capacitor you do have two plates separated by a dielectric where a static charge can build up on the plates without arcing across.  This one that I have been working on is an electric double layer capacitors.  In an electric double layer capacitor this separation of charge is at the interface between the surface area of each pole and the electrolyte. 

Because of this, if the electrodes are made of a very porous material with great surface area, a much larger amount of charge can be stored upon it, orders of magnitude above that of a similarly sized traditional capacitor.  Activated carbon is used in a majority of commercial designs because it has a very large amount of surface area per unit of volume or mass. The interactions between the ions in the electrolyte and the surface of the electrode result in a more complex charge and discharge cycle, but it is still much more reversible and much quicker than the chemical reactions within a traditional chemical battery.  Commercial versions can typically survive over a half a million cycles. 

One of the major limitations is that the breakdown voltage of the electrolyte limits the operating voltage of these capacitors, traditionally to around two volts with aqueous electrolytes, about 2.5 - 2.7 volts for organic electrolytes, although Maxwell has a 3400 Farad unit at 2.85 volts available now.  Since the stored energy in a capacitor is proportionate to the square of the voltage it is charged to (E = 1/2*C*V^2), any increases in the working voltage of such capacitors is significant in increasing their energy density.  Much research in this area among academics and manufacturers of such devices is ongoing at present.
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richhagen

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Re: Ultracapacitor Project
« Reply #19 on: February 15, 2015, 11:10:09 AM »
This is different than a traditional parallel plate capacitor.  A separator in a capacitor of this type must allow for the movement of ions across it.  An impermeable plastic separator will not work for that reason.   
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richhagen

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Re: Ultracapacitor Project
« Reply #20 on: February 15, 2015, 03:19:21 PM »
Ok, I ran a discharge test on one of the capacitors.  I left the capacitor connected to a bench supply at 1.2 Volts approximately overnight, actually about 20 hrs.  I measured the voltage at 1.177V just before disconnection.  I allowed the capacitor to stand for 1/2 hour and then connected two 15 ohm 5% resistors that I happened to have in my box in parallel across the capacitor for one half hour measuring the voltage at various intervals.  After one hour I disconnected the load resistors.  The results were a bit surprising to me, I am still trying to sort them out as a bit more than simple capacitance appears to be going on here.  Maybe someone here might have a better interpretation at the moment than I for what the results show. 
8636-0
There is a fast drop off when the load is connected, kind of like a surface charge on a battery, and there is also a bounce or recovery after the load is removed.  It seems to take an hour or so before it resumes a curve like the self discharge profile.

If I look just at the area between 2640 seconds and 3600 seconds where it approximates a linear power dissipation, with a starting point of .0257 Watts and an ending of .0192 Watts, the total power under that is approximately 25 Joules.  If we plug that back into 1/2 * C * (V1^2-V2^2) where V1 is the starting voltage and V2 is the ending voltage, we get a value for C of 483 Farads or so, but I don't think the assumptions hold for the whole curve there and I haven't thought it all out yet.  Ideas?
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richhagen

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Re: Ultracapacitor Project
« Reply #21 on: February 15, 2015, 03:23:53 PM »
*'total power under that curve' should be total energy under that curve because the area is power multiplied by time, and hence the output in Watt seconds, or Joules. 
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DamonHD

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Re: Ultracapacitor Project
« Reply #22 on: February 15, 2015, 03:54:30 PM »
Part of that fast drop and recovery bounce will be ESR I imagine.

Though this is a very non-linear beast that you have constructed.

Rgds

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MattM

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Re: Ultracapacitor Project
« Reply #23 on: February 15, 2015, 04:27:01 PM »
I did a little reading this morning to catch up on what your super/ultra capacitor is compared to what I thought they were.  Much higher densities I see.

The PVC looks like it would be more suited to rolled type of construction.


Mary B

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Re: Ultracapacitor Project
« Reply #24 on: February 15, 2015, 05:16:59 PM »
Capacitors will exhibit some voltage recovery when a load is removed. Very high voltage oil filled capacitors like I use in ham radio amplifiers ship with a shorting wire for this very reason. Not fun to brush across a couple thousand volts when unpacking!

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Re: Ultracapacitor Project
« Reply #25 on: March 09, 2015, 09:08:25 PM »
Interesting cap.   I wanted to mention one thing with it.   I'm not sure, but you may be happier with carbon plates, rather than the aquarium filter media.  Carbon is conductive, so any form should be good. 

I was playing with water electrolysis cells for a while (hint: they don't work as claimed).  I sourced my carbon from a few places.  The first few were the cores of D cell and 6V lantern batteries.   Then I ordered carbon rods.  Then I wanted more surface area for cheap, so I switched to carbon plates.

Search McMaster-Carr for "graphite rod", "carbon plate" and/or "welding carbon plates".    They were cheapest when I was looking a few years ago.

I'm not sure if you need density or surface area.   Obviously powder gives you more surface area, but can migrate.   Plates give you more density.

Even if you just want powder, it may be cheaper to get in another form like the plates, and smash it up with a hammer. :)

richhagen

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Re: Ultracapacitor Project
« Reply #26 on: April 02, 2015, 04:34:41 PM »
I am still working on this.  I have something to show once I get a chance to type it out and post pictures.  I have a string of home built capacitors built into Ball mason jars that I am going to install with a small panel and an LED light at a property I own.  Instead of the plates (which would allow for higher currents) that I used before, I used stitched bags with a bit of stainless steel wool stuffed with ground activated carbon with a threaded stainless rod for each electrode and 4M magnesium sulfate solution for the electrolyte.   The electrolyte is not as good of a conductor as KOH, but it is more tolerant should it be exposed to atmospheric gases over time.  I soldered two 3 Amp diodes in series such that it will begin to conduct at just over 1.2 Volts as an over voltage protection to prevent electrolytic corrosion of the stainless, I also put one  backwards to limit the reverse bias to around .6 volts should the polarity be reversed during discharge.  In the installation I think I will put an inline AGC fuse of about 2 amps as a protection for the diodes.  It is by no means a high current device, but it will keep one of my little high power LED lights lit all night and I am thinking it will be very stable over time plus the ingredients are relatively inexpensive.  Still testing.  Rich
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Mary B

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Re: Ultracapacitor Project
« Reply #27 on: April 02, 2015, 05:34:10 PM »
Maybe use a graphite sheet and roll everything?


richhagen

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Re: Ultracapacitor Project
« Reply #29 on: April 02, 2015, 11:26:36 PM »
Interesting, it is a bit pricey for what I would want though.  There would be advantages to using carbon conductors and I have looked at carbon welding electrodes as there would be no different metal ions or interactions.  With the MGSO4 electrolyte, you could dump the contents in your garden as soil amendments.  Actually a truly impermeable carbon layer over a good conductor like copper would be ideal, as the resistance of the carbon, and the stainless I am using is an issue.  While that can be compensated for by area of the conductor to some extent, that as well adds cost penalties.  I would still need the activated carbon as the amount of charge stored is a function of the surface area, at which activated carbon excels.  A plate design puts more of the surface areas of each pole in close proximity, which since this type of capacitor does rely on ion mobility allows for higher currents, but for now I am thinking that I will overcome current limitations by paralleling units for a larger setup, as for any significant storage many paralleled units of the size I have made would be needed.
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richhagen

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Re: Ultracapacitor Project
« Reply #30 on: April 23, 2015, 05:06:29 AM »
Ok, so here is an iteration of the electric double layer capacitor that I am thinking of deploying in a test for an outside light at a building I own.  I have been affectionately calling them tea bag capacitors. 

These were made in quart size ball mason jars.  I did have some plastic screw on lids which I thought would be more corrosion resistant than the metal lids with separate bands that are normally used with these types of jars.  The poles were made identical to each other.  I took some sno-coat roofing four inch contouring seam tape, which is really a cloth material, and cut ten inch lengths.  These were folded in half and a seam was sewed on each side with polyester thread to make a bag with an open top. I also grabbed some stainless steel wool and cut a 3 inch piece of 1/4-20 threaded stainless steel rod. 

The stainless steel wool was stretched out a bit and stuffed into the bag made with the contouring seam tape, to this activated carbon was slowly added a bit at the time and the bag was shaken to allow the carbon particles to settle without crushing the stainless steel wool.  once the bag was full, the carbon was pushed down and a bit more steel wool was added along with some more carbon.  Once the bag was full, a stainless steel rod was inserted, and worked into the material.  I had threaded two stainless steel nuts with a lock washer between them onto the rod, such that the top of the top nut was 2.1 inches from the top of the rod when the two nuts were tightened against each other.  The rod was inserted into the bag such that I could hand stitch the top of the bag closed over the two nuts, which makes it a bit more difficult for the rod to be pulled out, or slip out of the bag.  I then threaded two more nuts with a lock washer onto the stainless rod over teflon thread sealing tape, commonly used in plumbing applications to seal water pipes.  These nuts were tightened against each other over the sealing tap e such that the top of the top nut was three quarters of an inch from the top of the rod. 

These bags were checked to ensure that no stainless steal wool strands were sticking out such that they could puncture a second bag and short the capacitor.  The bags were then crammed into the quart jar.  This was tedious as the bags had to be worked into the jars.  I had only had regular mouth jars on hand as opposed to wide mouth jars which would have had a larger opening.  The lids were drilled with three holes through which gromets were fitted.  two of the holes were three eighths of an inch in diameter and spread apart as far as I dared with having to fit a rubber gromet into them and still be able to close the lid on the jar.  The third hole was bigger and a grommet was fitted for the purpose of inserting a fermentation trap to allow gases to escape without allowing atmospheric air in.  On later designs I left the third 'vent' opening off. 

The lids were fitted over the tops of the threaded rods and the lid was worked down.  The lid was tightened onto the threaded rods with a flat washer, a lock nut and another nut, all stainless.  The lid was then tightened onto the jar.  The jar itself was then filled with the electrolyte.  For the electrolyte I used magnesium sulphate solution.  This solution was made by dissolving four and a half pounds of Magnesium Sulphate pentahydrate, commonly sold as Epsom salt into one gallon of distilled water.  This takes quite a while to dissolve.  The electrolyte was added to the jars with a syringe through the opening in the larger grommet added to the lid for the fermentation trap.  the electrolyte was added to a level above the bags, leaving a bit of head space in the jar.  The fermentation traps were then added. 

Simple over voltage protection was made from three diodes.  The diodes were common 3 amp silicon diodes, type 1N5408, with two connected in series with the negative sides of the diodes toward the wire connecting to the negative terminal of the capacitor, which was chosen arbitrarily.  Another diode was connected across these two diodes in the opposite direction.  These diodes serve to limit the voltage to about 1.2 volts in the forward direction and .6 in the reverse.  The reality is that there is a bit of spring in the diodes forward voltage drop as the forward current is increased, so the voltage could go a bit higher in use. 

This package was then assembled and tested.  At first I used a bench power supply to charge them individually and then in series.  I made several with slightly different compositions to test.  I also made one with just the metal components and no activated carbon to make see what metal reactions might be occurring.  I also ran the voltage up on one to see what happened and found that electrolysis of the water occurs and significant galvanic corrosion of the stainless occurs as one nears and exceeds 2 volts.  I made 12 of this size and tested them with a 12V panel and LED lights.  The second six were constructed with the metal two part lids which actually made assembly a lot easier.


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richhagen

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Re: Ultracapacitor Project
« Reply #31 on: April 23, 2015, 05:25:35 AM »

Here six of them in series are powering an LED light, these were made with a small amount of steel wool, and the carbon was Calgon brand highly activated carbon, commonly used for water filtration which I had ordered online. 

The brightness of the light decreases as time passes, but the light will remain on all night at reasonable brightness.  I still have to measure the actual capacity of these.
I plan to use 12 of these on the first implementation, a small outside light at a building I own.  They will be charged directly by a small solar panel which won't be able to put out more current than the diodes can handle.  I plan to build a small light switch with a cadmium sulfide light variable resistor a transistor and a fet along with a few resistors to turn the light on at night only. 
Next on the agenda is to measure the actual capacity and to make a larger version, here is one in a half gallon jar, undergoing its initial charging. 

This is one in a half gallon size jar, of similar construction undergoing the initial charge, or forming process.  Initially these do not hold much charge, they have to be charged and held at voltage for a time.  This one initially took about an amp of current which decreases as it charges.  These are low current, slow charge and slow discharge, high capacitance capacitors.  I intend to continue to develop these as well as test these for their actual electrical properties with an emphasis on the charge and discharge efficiency and the long term stability of this basic structure. 
A Joule saved is a Joule made!