Homemade long term electrolytic caps. Finding an electrolyte recipe. - Page 1
Forum section: electronics / projects

author: Refrigerator
author_rank: Super Contributor
timestamp: February 05, 2017, 12:49:23 pm
content: Strong winds came and tore my wind generator to pieces so i decided to rebuild the whole thing.I want my generated electricity to be stored in an electrolytic capacitor but over time the generator might produce quite some electricity so big caps would be needed.Big caps are expensive and hard to find where i'm at so i decided to make one.I want my cap to be big so i will have to come up with a jig to wind it. But more importantly i want the cap to last.What determines the lifetime of an electrolytic cap is of course the electrolyte.From what i gathered most electrolytes are primarily made of borax and water/ethylene glycol.I've watched a tutorial by rimstar.org and also tried myself the water+sodium bicarbonate electrolyte and it did function but, as a few articles that i've read indicated, it does completely destroy the electrodes once voltage is removed.Ethylene glycol can be easily found in anti-freeze where it should be around 50/50 mix with water.Polyethylene glycol is also an easy to find chemical used in DOT4 brake fluid but i'm not sure if DOT4 could be used in an electrolyte.Pure water might seem best but during forming water based electrolyte could produce hydrogen gas and cause air pockets between the plates.Some further experimentation might be needed to find out a stable electrolyte recipe that could be made cheaply.Anyways it would be cool to see if anyone here has tried making electrolytic caps.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 05, 2017, 01:15:09 pm
content: Carbonates and borates are quite different, particularly in the way they may interact with vicinal glycols (e.g., ethylene glycol) and aluminum. Why (what scientific basis) did you choose the carbonate route?I suspect you read the Wikipedia article on capacitor electrolytes, so I won't link it here. As general advice, I would put greater faith in studies by capacitor manufacturers, such as Kemet (e.g.,http://www.kemet.com/Lists/TechnicalArticles/Attachments/15/2008-10%20CARTS%20-%20Al-Electrolytes%20for%20Automotive%20and%20High%20Temp%20Applications.pdf) than on YouTube-like demonstrations lacking much basis. Can you give a link to the specific demonstration you followed?John

author: free_electron
author_rank: Super Contributor
timestamp: February 05, 2017, 01:34:08 pm
content: What makes you think you can make a better capacitor,than the existing companies ?They dont use brake fluid as electrolyte...

author: Siwastaja
author_rank: Super Contributor
timestamp: February 05, 2017, 01:41:14 pm
content: No, you are not going to be able to DIY a reliable, long-lasting electrolytic capacitor (especially if you need to ask this kind of question...). A proof-of-concept elcap is possible if you are good with chemical processes.Billions of R&D money at chemistry industry giants have gone into the development of reliable electrolytic caps.Once you realize this, nothing prevents you from doing it, but don't fool yourself into thinking they would be usable in projects.Storing renewable energy in electrolytic capacitors is not viable even in the state-of-the-art technology, and there are no prospect that this would change in near future, even when zillions of $$$ is thrown at R&D of ultracaps all the time.

author: Refrigerator
author_rank: Super Contributor
timestamp: February 05, 2017, 01:54:33 pm
content: @jpanhaltthis video got me interested in DIY electrolytics.@free_electronI'm not here to challenge the big boys but since i haven't found anyone who tried making caps that last for more than just one experiment i thought i'd give it a try.@SiwastajaAfter i make the cap only time will tell if it was usable for my projects.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 07, 2017, 12:31:30 am
content: I am almost as negative as everyone else about making your own capacitors. But there is one little bit of wiggle room. You can relax some requirements that drive the big commercial outfits. Your capacitors, at least potentially, don't have to be space efficient. You may have a spare barn you don't mind filling with your 100 F capacitor. Your capacitors don't have to be transportable, so big glass vats with electrolyte recirculating pumps and automatic top off valves are an option.Things like that might make your capacitor possible, even if it isn't practical in a commercial sense. Do some electrode area calculations and see if you are happy with the results.

author: drussell
author_rank: Super Contributor
timestamp: February 07, 2017, 12:52:48 am
content: Quote from: CatalinaWOW on February 07, 2017, 12:31:30 amUnless it is some ridiculously high voltage, 100 Farads isn't very much capacity when you're comparing it to a typical battery-type storage system... A farad is only one coulomb of electrons (per volt of charge) for one second.If you could boost-regulate all of it at 100% efficiency, you would need a 3000 F capacitor charged to 120 volts to light a 100 watt bulb for an hour.There is areasonwhy capacitors are not (yet?) a substitute for electro-chemical cells...

author: tautech
author_rank: Super Contributor
timestamp: February 07, 2017, 12:53:57 am
content: Leakage is a factor that will be troublesome and potentially place DIY caps lower than current battery technologies.In a recent thread there was talk of 100 year old batteries still functioning and those old and now suppressed technologies need further investigation and modernisation IMHO. While they may be expensive to build today their /year price compared to much of the muck today might make them attractive.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 07, 2017, 01:17:17 am
content: How about nickel iron batteries... Much easier.. Leaky and self discharge over a few days, but work well in old Trolley Cars and in certain telephone applications. Cheap to build as well, if you like glass or plastic tubes...Steve

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 07, 2017, 03:17:16 am
content: Quote from: drussell on February 07, 2017, 12:52:48 amTotally agree on the practicality. But! Since I am sure a homemade cap won't use the exotic surface treatments in supercaps, several hundred volts is not out of reason. So your 1 hour 100 W bulb is "only" a couple thousand Farads. Again, the point isn't that this is the right way to go, just that it might be possible to build this engineering marvel. It is kind of like the guys building microcomputers with TTL logic, or the ones building Nixie clocks. Those projects are the wrong way to do the job in every way but the art of it. But the art sometimes makes it worth doing.

author: Refrigerator
author_rank: Super Contributor
timestamp: February 07, 2017, 04:52:33 pm
content: What ever you guys say i'm still gonna make the cap.I did some rough estimations and came up with about 0.336C of charge per 10m roll of tin foil.Looking at a roll of foil right now it looks like the cap will be quite small. I do intend to make it fat enough to fill 110mm PVC tube.Forming caps myself is also a quite convenient thing if i can get it right since i want my generator to be high voltage and low current to minimize the resistive losses, and be able to use thinner/cheaper wire. If i can successfully form a cap for high voltage then that gets rid of many problems ( eg. single cell without the need of balancing ).I don't need to make these caps compact since they will be sitting outside zip-tied to the pole that my generator will be on top of, anyways.

author: ConKbot
author_rank: Super Contributor
timestamp: February 07, 2017, 05:16:30 pm
content: Quote from: Refrigerator on February 07, 2017, 04:52:33 pmI don't think you understand how big a 120V 100F electrolytic capacitor will be, regardless of home made or professional. A 25V 1F electrolytic is 4" across and 10" long(talking a Nichicon cap here, not a car stereo one). And you'd need 2500(500 parallel strings of 5) of them to get 120V, 100F. 720kJ total energy, 200 watt hours, assuming you can extract it all.Versus something likehttp://www.batteryspace.com/custom-lfp-26650-battery-pack-25-6v-9-9ah-253wh-16a-rate-with-pcb-23-76.aspxOrhttps://www.amazon.com/ExpertPower-EXP12200-Rechargeable-Threaded-Terminals/dp/B00KC39BE6If you want to play with making your own electrolytic caps, have fun. But don't expect to do anything super useful in terms of energy storage for domestic use.If you do make a 700Kj cap bank, for the love of all that's holy please make a coil gun or rail gun too

author: Refrigerator
author_rank: Super Contributor
timestamp: February 07, 2017, 07:45:06 pm
content: Wait a minute... where did the 100F figure come from ?i'll make a big cap but i won't know the capacity till i'm done with my experiments.right now i'm experimenting with 4x8 cm Al foil plates in different electrolytes.First observation: borax + water = no bueno; 1.135V drop across cap, with 4mA current, no oxide forming even after many hours.The foil is not sanded or textured in any way, but when i have a jig for rolling the cap it will drag the foil over some sandpaper to increase the surface area.I wonder if i could electroplate some aluminum on carbon and then form the capacitor.Basically make an electrolytic-supercap hybrid.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 07, 2017, 07:55:42 pm
content: Quote from: Refrigerator on February 07, 2017, 07:45:06 pmIn your original post you state you want to store wind generated electricity. One of the responses showed that it would take a 100 F capacitor to store enough energy to light a 100 W bulb for 1 hour.That is really not much energy storage, but it is probably the smallest you could realistically think of. By using low wattage LED lights you might be able to find your way around and do a little reading at night for a couple of windless days. (Assuming leakage losses don't cause a problem).Your storage needs may vary, but energy storage always seems to come out needing capacitance measured in Farads. Lots of them.

author: james_s
author_rank: Super Contributor
timestamp: February 07, 2017, 08:40:49 pm
content: The only way you are going to reliably store a reasonable amount of energy in something home made is with a lead-acid battery. Those are actually fairly simple to make, it's still easier and safer to go buy commercial batteries but you can make one yourself that does work about as well as one you can buy although not nearly as convenient.A capacitor? Forget it, sure you can make an electrolytic capacitor at home, maybe a few tens of microfarads and if you're careful it may last a few days or weeks. Something large enough to be useful storing energy from a wind turbine though? No way, it's just not going to happen. Even if it were feasible it would be dangerous, have you calculated how much stored energy there would be? Have you seen what happens when a really big capacitor is charged up and then shorted? Stored energy is dangerous, there's no way around that.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 08, 2017, 12:17:42 am
content: Stored energy is always dangerous. Batteries, pumped water storage, molten salt, capacitors, gasoline you name it. The danger comes from the total amount of energy and the rate at which it can be discharged.I wouldn't be surprised if the ESR and inductance of a very large home made capacitor made the discharge rate low enough to line up in danger with a lead acid battery system, but with much lower total energy. Refrigerator will have to be careful, but the major additional danger comes from the fact that he is travelling a road not often taken so it is harder to benefit from the failures of others. He doesn't have dozens of people warning him of the dangers of hydrogen gas accumulation, acid spills, lead contamination and the like.

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2017, 12:31:53 am
content: That is a good point of course. Still I think it's important to put things into perspective here, I have not done any actual calculations but I'll take a wild assed guess and say that home made capacitor capable of storing as many Watt Hours of energy as an off the shelf deep cycle battery you can get for $100 at Walmart is going to be something around the size of a semi tractor trailer. Chemical batteries have energy density orders of magnitude higher than capacitors, and that's proper mass produced commercial capacitors. Anything that works well enough to be useful will be dangerous, difficult and expensive to build. I'm a big fan of DIY, but one still has to recognize when it makes sense to buy rather than try to build.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 08, 2017, 12:56:15 am
content: Quote from: james_s on February 08, 2017, 12:31:53 amAll true. This only makes sense as art. Like building your own Nixie tubes, or emulating a Pentium in TTL.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 08, 2017, 01:04:51 am
content: In spite of the popularity of the idea, it's hard to come up with a worse way to store energy than a capacitor. First order of business might be to go here-http://www.tinaja.com/etsamp1.shtmland read everything Don Lancaster has to say on energy. A better storage system might be to pump water into an elevated holding tank, or raise a few hundred thousand pounds of concrete a couple feet. Then power a generator as the water or cement comes back down. IMO, it's still fun to try and construct a capacitor. You'll need to etch the foil to get any reasonable value. I think the usual electrolyte formula has you bubble ammonia through the glcol-borate mixture. Maybe something useful in my collection of old Sprague cap notes here-http://conradhoffman.com/lib_item_list.htmYou may find some clues on electrolytes and energy storage if you read between the lines.

author: forrestc
author_rank: Unknown
timestamp: February 08, 2017, 01:08:22 am
content: Quote from: Refrigerator on February 05, 2017, 12:49:23 pmThe correct 'electrolytic capacitor' for this purpose is created with sulfuric acid and lead plates. Or better put - a lead-acid battery. Or maybe some other battery chemistry.As, now I look down the thread some other people have said the same thing.People a lot smarter than you and I have been working on improving lead-acid battery storage for years. So far, there really isn't anything which is better, although lithium-ion batteries are finally giving it a run for the money, and there's some work on various iron (aka edison) batteries as well. Capacitors aren't even close.

author: drussell
author_rank: Super Contributor
timestamp: February 08, 2017, 01:21:38 am
content: Quote from: CatalinaWOW on February 07, 2017, 07:55:42 pmYou guys are off by more than an order of magnitude. A 100F capacitor charged to 120 volts would light a 100 watt light bulb for only two minutes, not an hour. You need a 3000F capacitor to get an hour.That is, of course, assuming that your (Batteroo-Brand?) boost converter can slurpallthe energy from the capacitor, over an input voltage range of 0 to 120 volts, with 100% efficiency.A 3000F parallel-plate capacitor with a .001 inch plate spacing, aluminum oxide dielectric (dielectric constant of 8.4) requires about 400 square miles of aluminum foil. Even once you double the effective surface area by rolling it up to use both sides of the plates (200 square miles) and increase the surface area by roughing the surface, I don't see how this idea is even remotely feasible, no matter how close you might be able to make the plate spacing.You need electrochemical cells or pumped storage or something to even begin to be in the realm of being possible. Even thinking about being able to store that amount of energy in an electrostatic field is pure insanity!

author: tautech
author_rank: Super Contributor
timestamp: February 08, 2017, 01:28:18 am
content: Quote from: drussell on February 08, 2017, 01:21:38 amLike a magnetically levitated 100K RPM flywheel ?

author: drussell
author_rank: Super Contributor
timestamp: February 08, 2017, 01:42:45 am
content: Quote from: CatalinaWOW on February 08, 2017, 12:56:15 amLOL, I would love to see a Pentium in TTL.It would probably only take, what, about 75,000 7400-series chips and fill a large building or two. Not sure how someone would power it, though.I'll stick with my still-functioning original Wang 2200 system from the 1970s, thanks... It is made from 7400 series logic, uses 74181 ALUs for the main math functions. That's plenty big enough for me...I really should make some videos of that system sometime.

author: nctnico
author_rank: Super Contributor
timestamp: February 08, 2017, 01:47:04 am
content: If you want a lo-tech solution then lead-acid batteries are the simplest to make and maintain. As long as they are charged and discharged right they can last a very long time.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 08, 2017, 02:08:33 am
content: The nickel-iron batteries referred to above are old tech, but might well lend themselves to a DIY effort. Probably info on them in the old Audel's Electrical Guides and/or similar books.

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2017, 04:30:18 am
content: I'd never heard of nickel-iron batteries, sounds interesting. Nickel is expensive stuff though, isn't that the bulk of the cost of NiCd and NiMH batteries?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 08, 2017, 06:11:52 am
content: Quote from: drussell on February 08, 2017, 01:21:38 amI didn't check the original math or yours, but we agree that lots and lots of Farads are required for meaningful energy storage. But there are other math errors. The effective plate separation for an electrolytic capacitor is the oxide thickness, not the separator thickness. Which for a 500 V capacitor will be on the order of 50 microinches. So now you are down to 10 square miles, without surface etching. Which might get close to another order of magnitude. Still enormous, but maybe doable.As an older guy capacitors are one of those things that make me leary of the word impossible. When I started electronics a 50,000 microfarad capacitor was an enormous device, expensive and impractical for most applications. The largest capacitors used widely were a couple thousand microfarads. Any engineer on earth would have laughed at you if you discussed making capacitors measured in Farads. Now you can buy low voltage capacitors in values of 100s of Farads, and they aren't much bigger than those beasts from the start of my electronics career.Still doesn't make capacitors a good choice for energy storage, except as a stunt with little real use.

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2017, 06:19:47 am
content: Sure but I think it would take an exceptionally dedicated hobbyist to hand build a capacitor equivalent to the average off the shelf electrolytic cap available back then. Something comparable to a 1950s electrolytic capacitor might be feasible. The modern compact high value stuff is the product of billions of dollars of R&D and state of the art factories.

author: NMNeil
author_rank: Contributor
timestamp: February 08, 2017, 02:51:23 pm
content: Google Robert Murray-Smith, he's working on similar experiments.Draw your own conclusions on their validity, but his video's are fascinating a lot of people.

author: albert22
author_rank: Regular Contributor
timestamp: February 08, 2017, 05:51:19 pm
content: Quote from: drussell on February 08, 2017, 01:42:45 amI would love to see the wang 2200 videos. I started my career as a technician servicing wang 2200T, VP, MVP and VS. Brings back good memories. I still have manuals and parts from that time.Best regards

author: drussell
author_rank: Super Contributor
timestamp: February 08, 2017, 06:24:30 pm
content: Quote from: albert22 on February 08, 2017, 05:51:19 pmNot to hijack the capacitor thread, but I always find it interesting to find another person who "cut their teeth" so to speak on the 2200. It was certainly the first computerIever used, before my aunt and uncle got their PET and many years before we got our first home computer (a TI-99/4A.) My father's business used the 2200 MVP well into the 1990s (we even had the terminal emulator package for a couple of XT-class PCs to use instead of 2236 terminals) and I could have kept it running for much longer but we moved offices and wanted to downsize the physical space requirements away from the Wang equipment and went to PCs with thin coax. I can't recall if we kept using the band printer for a while at the new office or not...I have a working 2200 LVP (well, the 8 meg Shugart works, I haven't been able to get the 8" floppy drive to work for many years, need to look into that) and a working 2200 MVP that used to have an 14" 80 meg CDC Phoenix connected to it which I dismantled many years ago for parts (a high school student at the time, my parents said I could only keep it if I dismantled it for parts) but still have the fixed platters stored in a sealed box and about 6 of the removable disk packs for it, in case I ever find another Phoenix.) The band printer was also a "keep if you dismantle for parts" deal. I also have a stalled long-term project on the go for an IDE disk interface card (good ol' parallel IDE, none of this SATA rubbish) for the 2200 series that I would love to find time to finish.I only have a couple of 2236 terminals left and the foamies in the keyboards are going to need some kind of refurbishment very soon but are otherwise operational. I also have a working 2235 dot matrix printer and some other miscellaneous pieces for 2200s and some remnants of one of the word processing systems or somesuch that uses the twin coaxial connections. I never saw that operational, I just grabbed it in a big load of Wang stuff many, many years ago and they're still in the horde.I have the (5 meg ?) 14" drive for that system but it just throws a fault light and won't even load the heads. I don't think there was ever an interface for that style drive to the 2200, though, so it is pretty useless to me, I guess.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 08, 2017, 10:56:27 pm
content: The actual amount of Ni in a modern Edison cell would be a fraction of what Thomas's technicians would have used. By the Time the Edison Battery Company started, Thomas had many contract researchers, with a rule about his name going on the patents...Plate it on a iron substrate or use the course powder or flake only on the electrode surface, job jobbed....Yes, it would be expensive initially, but no where near what its going to cost to make a high current density connection to to Al foil, or roll or pack capacitors.Ni-FE is nearly indestructible if cared for.Steve

author: carl_lab
author_rank: Frequent Contributor
timestamp: February 08, 2017, 11:07:24 pm
content: @RefrigeratorI'm sure you're wasting your time.You will never reach capacity or lifespan of recently available supercaps, probably not even conventional electrolytic caps.Supercaps/Ultracaps are used if you need high charging/discharging current in a short time.https://youtu.be/EoWMF3VkI6UThe benefit of supercaps compared to accumulators is high current ability and very high cycle number (500000) - not high capacity (Wh).Here is an overview of available maxwell supercaps:http://www.maxwell.com/images/documents/Product_Comparison_Matrix_3000489_2.pdfBiggest singe cell of these is 3400F - 2.85V - 3.84Wh, max. current 2000A (!). Dimensions d=60mm , L=138mmYour 100W bulb can be powered for 3.84Wh/100W=0.0384h=2.3min by one of these 3400F/2.85V supercaps.If you want to power it for 1h, you need n=60/2,3= 26 of these caps.I think these are about 45 US$ per piece, so your cap battery is about 26*45US$=1170US$ ...You can buy 23 lead-acid car batteries (12V/36Ah/432Wh) for that money!And the car battery has 4.32x the energy of your maxwell supercap battery.So supercaps are about 23*4.32=100 times more expensive per Wh.Some more random web finds:http://www.altenergymag.com/article/2015/06/ultracapacitor-usage-in-wind-turbine-pitch-control-systems/20392/https://gigaom.com/2011/07/12/how-ultracapacitors-work-and-why-they-fall-short/http://www.angliac.com/epcos/literature/EPC690037600.pdfhttp://budgetlightforum.com/node/33167https://youtu.be/8miq6sDy0wA

author: TimFox
author_rank: Super Contributor
timestamp: February 08, 2017, 11:35:35 pm
content: Note that the energy stored in a capacitor is (1/2) x (charge) x (voltage), but the energy stored in a battery is (1) x (charge) x (voltage). As you discharge the battery over its useful range, the voltage does not sag (much), but the voltage across the capacitor sags proportional to the charge removed.Note that this is true independent of the series resistance in the capacitor circuit.Therefore, I second the recommendations above to use an appropriate storage battery rather than a capacitor.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 09, 2017, 12:13:12 am
content: Mogami cable company has some fun puzzles. Here's one-http://www.mogami.com/e/puzzle/pzl-03.htmlBack up one level on the URL to see the rest.

author: carl_lab
author_rank: Frequent Contributor
timestamp: February 09, 2017, 12:40:21 am
content: Quote from: TimFox on February 08, 2017, 11:35:35 pmYou're right.You need a DC-DC converter with wide input voltage range for (halfway) efficient use of the stored charge and for stabilization of output voltage.Using an accumulator (lead-acid or lithium) is more simple, much cheaper, simply better solution for storing energy of a wind generator.

author: JPortici
author_rank: Super Contributor
timestamp: February 09, 2017, 08:58:12 am
content: Quote from: james_s on February 08, 2017, 06:19:47 amhe coulse resell them to audiophools thenThere is nothing like the sound of an handmade capacitor. only the best salts for electrolytes, not that goop the commercial units get to use."My grandma was from russia, where she used to work in a chemistry lab as a cook. She passed down this recipe she spent a lifetime on perfecting"Joking aside, i've been followig the topic these days. very cool project

author: Refrigerator
author_rank: Super Contributor
timestamp: February 09, 2017, 02:09:36 pm
content: Quote from: NMNeil on February 08, 2017, 02:51:23 pmI've been watching his videos for over a year now.

author: newbrain
author_rank: Super Contributor
timestamp: February 09, 2017, 03:21:42 pm
content: Quote from: JPortici on February 09, 2017, 08:58:12 amYou might be joking...Butthis guymight not...andthesedefinitely are not.The combination of some morals and the impossibility to keep a straight face is for sure limiting my money making possibilities.

author: JPortici
author_rank: Super Contributor
timestamp: February 09, 2017, 04:56:34 pm
content: that doesn't surprise me at all.i find these people that begs at you to be scammed to be somewhat fascinating.. and i laugh inside when they "find out" they were scammed

author: Nerull
author_rank: Frequent Contributor
timestamp: February 09, 2017, 10:43:26 pm
content: Capacitors are intended for temporarily storing small amounts of energy for rapid use. Why on earth would you want to hook one up to a generator?A device intended to store large amounts of energy in a relatively small space for use at a later time already exists. It's called a battery.I used to work for a medical device company which manufactured defibrillators. They used a battery to charge a couple of pretty massive foil caps up to 2000V, then dump this energy into a set of electrodes. A high energy shock is about 300J. A single AA battery stores 40 times more energy and you could fit a whole lot more of them in the same space.

author: newbrain
author_rank: Super Contributor
timestamp: February 09, 2017, 11:21:43 pm
content: Quote from: Vtile on February 09, 2017, 09:38:50 pmAnd they'd better do,at >350$ a pop (after discount!).Sorry for derailing the thread...but I think the OP got their answer: batteries.