Whats the differance in super caps and normal caps? - Page 1
Forum section: electronics / beginners

author: yada
author_rank: Frequent Contributor
timestamp: April 29, 2017, 08:37:58 pm
content: Is there a trade off to their small size?For instance thishttps://youtu.be/wSGCqyvzlgs?t=2m25shas a value of 1F which is huge but so does this one:There must be a reason why you would use that huge $80.00 cap over some thing that is the size of a normal 1cm electrolytic.But 1f is 1f is it not? So in theory you could replace that huge cap with a little tiny super cap across your car stereo?I know in batteries (totally different chemistry) you can have the same ratings but they will be very different because one can deliver the power in a quick burst, i.e. a 1Ah lead acid battery can not be replaced by a 1Ah cell phone battery. The cell phone battery wouldn't be able to crank the starter.

author: Neilm
author_rank: Super Contributor
timestamp: April 29, 2017, 09:31:07 pm
content: There is one big trade off - the voltage. I have seen super caps of 220F (yes Farad) but the rated voltage was only 3V. That huge cap in your car stereo is probably at least rated for 24V volts or probably higher

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 29, 2017, 09:44:31 pm
content: Yes, the voltage rating is much lower.To get a supercap with the same rating you would need to put several in series.This will reduce the equivalent capacity which can be compensated by adding even more in parallel.Result: More volume.

author: viperidae
author_rank: Frequent Contributor
timestamp: April 29, 2017, 09:49:49 pm
content: The big ones you put in your car have very low internal resistance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 29, 2017, 09:50:32 pm
content: When is 1F not 1F? When it's a resistor...No component is a pure element. Indeed, necessarily so. Resistors, capacitors and inductors (the physical components) all have complex mixtures of resistance, capacitance and inductance. We merely call them what they are, because that property is dominant over a useful range of frequencies.It's all about frequency range.We must always be careful not to fool ourselves into thinking that property extends farther than it actually does!A supercapacitor is useful at low frequencies: perhaps uHz to 10s of Hz. Below that frequency (down to DC), they look like crappy resistors (leakage current). Above that frequency, they look like crappy resistors again, smaller this time (ESR). At higher frequencies, they look like inductors (probably in the 20nH range).There's also finer structure to each of these components:- The leakage comes with long time constants across it, so that leakage starts out high, then decreases over time (in a way that the rated capacitance cannot account for).- The capacitance itself, even in the range where it's being a "good capacitor", isn't ideal, and has some resistance associated with it, and this resistance varies with frequency. (Supercapacitors use the diffusion of ions in a solution, which is great for value -- you can get a lot of ions in solution; but awful for losses -- ions move slowly and with a lot of "friction". This is distributed over a wide frequency range, because ionicdiffusionis a very gradual process.)- The inductance- And this is all to say nothing of temperature dependency, or aging, which affect all these parameters to some extent. Most notable is ESR (and ionic diffusion losses) vary strongly with temperature, getting particularly bad at low temperatures (until, when the electrolyte freezes, the capacitor stops, uh, capacitating, at all... it's incapacitated, you might say..).A regular electrolytic has the same model, but the frequency range is different -- reflecting the smaller capacitances, lower ESR, and somewhat lower ESL typical of them.So, applying this to the video: the 1F is acting like a low value resistor, at the frequencies being measured. It is not doing a perfect job, by any means -- not nearly as well as a 1000uF electrolytic, or a 10uF film -- but at the scale shown, that's apparently enough.The guy also appears to have much more test equipment than his experience and understanding would suggest to be necessary...As for your case: you get two things with the pictured situation. When the capacitor is near the "AMP", it's able to supply power that the cable would otherwise drop. This is important at modest frequencies (over 10kHz, say), where the cable has equivalent inductance (because, again, nothing is ever just "what it says on the tin", and the cable has resistance, AND inductance, AND capacitance, all depending on frequency; and for frequencies above about 10kHz, the cable will be dominantly inductive).But, this is probably not important to the AMP, because it will also have capacitors inside it already, enough to handle this.So we move on to the next suspect: the battery. A battery isn't quite a capacitor: it doesn't store charge proportional to voltage, as a capacitor does; rather, the voltage tends to remain nearly constant*. But given that adjustment, a battery behaves very much the same as a capacitor, having that equivalent circuit with C, ESR and ESL. But the frequencies are even lower than for a supercap -- batteries are good for ~nHz to ~Hz.(*Precisely, it follows an exponential relationship on the concentration of chemicals that are reacting to generate power. So the voltage falls gradually as you discharge the battery, then when it's pretty much empty, it just tanks (the exponential slope goes, well, exponential).)So if you have a cold, or aging, battery (high ESR, low time constant) that isn't capable of supplying the AMP for short durations, the Capacitor helps.Mostly, though, amplifiers don't consume nearly that much power, even under peaks, and it's a lot of marketing wank. This is reflected in the shitty construction of poorly verified consumer "capacitors", which may often be Matryoshka designs. Smaller example:Youcanget proper electrolytic or "super" type capacitors, in sizes and ratings suitable for supplying a very large amplifier (many kW) from a modest automotive electrical system (battery and alternator, both suitably sized -- at this rate, you may have two or more batteries wired in parallel, and your alternator will probably be upsized a few times from the usual). Beware of poor imitations, though; and, remember this: if you can't tell an objective difference (i.e., measuring the clipping point on loud music), you're better off saving the money.Tim

author: Zero999
author_rank: Super Contributor
timestamp: April 30, 2017, 09:29:39 am
content: Quote from: T3sl4co1l on April 29, 2017, 09:50:32 pmYes, car audio capacitors are a load of audiophoolery and do nothing in reality. If it does make any verifiable difference, then the, wiring is too thin, or battery or alternator must be bad. The amount of power taken by a car audio amplifier is nothing compared to the starter motor. The maximum RMS power you can get from 12V into a 4R load is just 18W, so you'd need a lot of speakers to significantly load the car's electrical system. If the amplifier really can deliver more than 18W into a 4R load, then it will have boost converter built-in, which should have sufficient decoupling on the secondary side.

author: BrianHG
author_rank: Super Contributor
timestamp: April 30, 2017, 10:06:45 am
content: What about getting rid of that dimming of all the lights in your car every time the bass drum fires off at 500watts to 1kw. I could have sworn that placing a 10F cap at the high power amp input smooths this out to a flatter load on your car's electrical system.(I don't think the OP is playing in this wattage field designed for those who have systems designed to shake an entire city block like the ones I've seen (oops, heard...) at the CES show in Vegas & the $$$ involved in such a setup would not be looking for alternatives like super-caps...)

author: Zero999
author_rank: Super Contributor
timestamp: April 30, 2017, 10:58:05 am
content: Quote from: BrianHG on April 30, 2017, 10:06:45 amHow do you get that kind of power level?Are you talking about RMS or peak?Assuming 1kW peak, 500W RMS, you'd need any of the following:1) A single 0.144Ohm subwoofer. I've never seen such a beast. The lowest commonly available impedance is 4R.2) An array of 28, 4Ohm woofers. Seems crazy but doable, although most amplifiers aren't designed to drive such a load, so perhaps one amp per speaker.3) A boost converter, to power the amplifier with 63.25V (more to account for losses in the amp) and drive a 4R load.#3 is probably the most sensible, as amplifiers designed to run from these sorts of voltages are widely available and a DC-DC converter is easily doable. As it's not necessary to provide this kind of power continuously, the boost converter needn't be designed for 1kW RMS. It can easily be designed for 500W or less and it should have adequate decoupling provided on the secondary side. It should also continue to supply the same output voltage, in spite of any dips in the input voltage.Lastly, normally car batteries have an internal resistance of under 10mOhm, which should give a voltage drop of 833mV with a 1kW load. When the engine is running, you have the alternator in parallel with that, so the total impedance should be much lower. If the voltage is dropping by significantly more than that, then you need a new battery, alternator or the wiring is poor.

author: Seekonk
author_rank: Super Contributor
timestamp: April 30, 2017, 03:14:21 pm
content: A couple amp charge will get a battery to 14.5 volts easily. That internal resistance is only for the rated battery voltage. So changes in current can dim the lights. Turn them off if they bother you. It doesn't necessarily effect the sound. These systems all use inverters to raise the voltage and though it is unlikely they are regulated, the amp shouldn't care much.

author: BrianHG
author_rank: Super Contributor
timestamp: April 30, 2017, 03:33:51 pm
content: It's peaking during the bass drums.The woofers are 4 ohm, but you already know that the amps have step-up DC-DC converters. Though they regulate and filter the power, they do not have any big caps in them. This means the DC12v side gets nice, counting for losses in the conversion, 100 amp spikes at every strike, or, low frequency bass drive. No 10f cap see the 100 amp sag every beat. 10f cap smooth out the sag to a constant 10amp load, slowly going up to 50 under demanding situations, slowly lowering down. No matter what you think the impedance of the battery and alternator, with the car electronics drawing today around 10 amps, with a 100 amp spike around 60 to 140 shots a minute, you see that dynamic load as the battery goes from 13.8v down to around 12v and back up.It is healthier for your cars battery and alternator to see a smoother 10-25amp load instead of these continuous 100-200amp spikes 60-140 times a second. Even though the amp may still work fine under both situations.And if you don't think people put that much power into cars, attached is a photo of a few more than 2kw subwoofer system, not including the rest of the speakers. Ok, so these guys need additional car batteries and additional alternators.And these systems are small compared to 1 killer 20kw install I saw at CES. It was in a modern station-wagon type car, where all of the rear was nothing but sub-woofers facing vertically up. When running, it lifted the car up&down on it's suspension.The last image is a 2kw car audio amp. As you can see, there is not a lot of room for huge caps.

author: Zero999
author_rank: Super Contributor
timestamp: April 30, 2017, 03:53:32 pm
content: Quote from: BrianHG on April 30, 2017, 03:33:51 pmOh with that much power, it's definitely plausible there will be a dip in voltage, enough to make the lights dim. Another thing that could be done is use lamps with regulated PSU, such as HID or LED, so there's no dimming.I doubt the suspension thing, someone probably connected their adjustable suspension system to the stereo, for effect.Do people ever run those killer stereos when driving with the volume turned up?

author: BrianHG
author_rank: Super Contributor
timestamp: April 30, 2017, 04:05:58 pm
content: Quote from: Hero999 on April 30, 2017, 03:53:32 pmIn my old neighborhood, there were 2 different rich kids competing. I'm sure the cops were called.The systems were so loud, they must be driving with ear-plugs. My house windows & paintings would shake when they really wanted to show off and they were a few houses away at the end of the street.

author: yada
author_rank: Frequent Contributor
timestamp: April 30, 2017, 07:08:23 pm
content: The car stereo comment was just an example. My car stereo is just fine and I value my hearing; when I was a kid I had car amps that had their own 1F caps (not all "marketing wank", for this set up, the car would stall on big base hits without them, and I killed the alternator in a month, the battery was in the trunk and wired with 4ga wire) this was in the 1990s before super caps, when everyone was upgrading their tape decks to CD players because the DIN shape was universal. I know for a fact I damaged my hearing; the bass dB was measured over 100, tweeters could go to 130. I would blow 60 Amp fuses so I know you can pull some AMPs.So you could replace the whole 1F electrolytic with for example 1F @3V caps (is $5.00USD a real price?) if you had 15 of them ($75 is still less then a good brand name electrolytic); five in series then three banks of five wired in parallel? I don't know what they cost but the size savings and the ability to run very short leads to the amp seems like it would be worth it. Seems crazy to put 1F of energy over those little leads. The electrolytics would weld/explode stray bits of copper wire, not much thinner then those leads, when the terminals were crossed by accident.

author: Zero999
author_rank: Super Contributor
timestamp: April 30, 2017, 07:37:27 pm
content: Quote from: yada on April 30, 2017, 07:08:23 pmA 15V rating for a car electrical system is marginal. I'd go for 20V or more.Still, I'd look at using thicker wire, upgrading the battery (perhaps another one in parallel with the amp?) and alternator before adding a capacitor.What's the ESR of those super capacitors? It has to be less than that of the car battery and the wiring to make any difference.A big, industrial PSU filter capacitor is probably your best bet, rather than those crappy audiophool ones with LEDs on it.Low ESR will probably be better than more capacitance. Looking at what TDK, Kemet and Vishay have to offer. I'd go for a 25V 0.47F unit with 3mOhm.http://www.farnell.com/datasheets/2045972.pdf?_ga=1.141165815.47418993.1417808164http://www.farnell.com/datasheets/2259605.pdf?_ga=1.173632486.47418993.1417808164http://www.farnell.com/datasheets/2280822.pdf?_ga=1.173682662.47418993.1417808164

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2017, 07:20:11 am
content: Ok, if you want to use super caps, say they are 3 v and for safety, you only balance charge them to 2.7v. Now, you need at least 18v clearance as stated above (20v), that's 7 caps. This means you will need 7x 10 farad caps in series to get just slightly better than 1f. Now, you also need super low series impedance since the caps are added up in series.Say something like this:https://www.digikey.ca/product-detail/en/eaton/TV1030-3R0106-R/283-4668-ND/6071917But, with 26mohm, in series x7 = 182mohm, + loss in wire leads & solder, you are at 69.23$ + shipping.You also need balancing circuits to prevent over-charge, for 7 caps, add another 10$.1 Single high quality Aluminum electrolytic 25v 1f cap is beginning to sound worth the price with only 5mohm series resistance, it roasts the supercap's 182mohm solution with 18-20v support.

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2017, 07:32:05 am
content: Quote from: evb149 on April 30, 2017, 05:40:47 pmDAMNCant find the photo. I saw a small truck, (pretty much your idea) when you open the rear, a servo driven sub-woofer which was at least 6 feet wide (not an array, 1 diaphragm) like in back-to-the future scene, but, it was real and functional for outdoor concert events which was being developed at DIYaudio.com 10 years ago for rental. We are talking 25kw, 2.5hz response. To make the thing work off of the 240v mains, the engineer had access to 1000X1f75vcaps. Yes, you are reading right. It took minutes to charge up slowly before going on. His excuse was he needed to storage to go cleanly through the bass and difficult parts of the music without exceeding the maximum breaker load on the fuse boxes & extension chords from the power sources at his disposal at such events.Can someone do the math on how many Joules 1000 1F caps can short out at. I know it was done on the DIYAudio site back then...You should have seen the photographs of the huge copper sheets around 1/2 inch thick he used to bolt the caps together and the stud mount diodes in series and parallel. I think his amp supply targeted +&- 480v.

author: Augustus
author_rank: Regular Contributor
timestamp: May 01, 2017, 10:29:29 am
content: Quote from: evb149 on April 30, 2017, 05:40:47 pmWell, next step would be a proper bass truck

author: SeanB
author_rank: Super Contributor
timestamp: May 01, 2017, 11:43:57 am
content: I used to travel by bus, and decided to skip one one afternoon, when I heard it coming from 1km away. Caught another that was coming 5 minutes later.You can do a lot with a bus, especially if you take out the rear 2 rows of seats and make it a bass box, and inside as many 12in woofers as you can fit there, and take the overhead racks and turn them into one long reflex box down each side, and have a 30W midrange and tweeter per seat row, driven by a whole wall of car audio power blocks that occupied the seat row directly behind the driver, in an acrylic enclosed block which had it's own set of blowers to move air through it. Must have had another big alternator and battery bank along under the chassis for that alone, just saw it one day in town parked at the rank.

author: yada
author_rank: Frequent Contributor
timestamp: May 01, 2017, 12:15:12 pm
content: Quote from: Hero999 on April 30, 2017, 07:37:27 pmTwo batteries rarely helps like a cap does. I tried that once, it was just big, heavy, and more expensive. Plus mounting it wasn't easy, took up lots of space and you have to make sure you have a place for it to leak onto. Replacing the wires with thicker ga can be a nightmare with the complexity of car wiring harnesses and trying to make things fit through holes that are already filled with wires. Upgrading the alternator is going to cost a few hundred assuming a bigger one could be just bolted on, most cant be and will require machining parts and possibly rerouting belts. Putting a cap in the trunk is just two wires and tie strap. Always try the cap first, do what easiest and cheapest before getting overly complex. No offense but have you ever worked on automotive electrical or installed a high current system in a car? It seems super simple just +12V and gnd, how hard can it be? But making everything look stock and having it fit all nice an neat with no panel gaps while balancing space and sound is a challenge. Also trying to keep down alternator noise and rattles/ rod noise can also be a huge head ache when you are trying for very accurate sound.And anyways the car audio comment was just an example to compare size in an application. I have no plans to alter my stock car stereo, unless you are telling someone else to upgrade their wires?

author: X
author_rank: Regular Contributor
timestamp: May 01, 2017, 12:24:55 pm
content: Quote from: Hero999 on April 30, 2017, 03:53:32 pmYes.

author: skarecrow
author_rank: Regular Contributor
timestamp: May 01, 2017, 01:47:02 pm
content: Quote from: Hero999 on April 30, 2017, 10:58:05 amSorry, but I have to correct you there. 4Ohm is actually the HIGHEST commonly available for mobile audio, as just about all mobile audio electronics are designed for speakers of 4 ohms or less. Home audio, on the other hand, is usually designed for 8ohm speakers. When you get into competition grade speakers you can find them as low as .5ohm (possibly even lower) per coil with as many as 4 coils per subwoofer. High current amps can often power .25ohm loads without a problem. Back when I used to compete in dB Drag and USAC events I had 1200 watts RMS pushing a .75ohm load. Automotive voltage is actually around 14.4v, not 12v.I do agree, for the most part, with your previous comment about wires being too thin. Definitely the first/best upgrade for large systems is a high output alternator and the "big 3" wire upgrade. As another user posted though, sometimes that's easier said than done. Also, if you are competing certain upgrades might bump you into a higher class, but adding a cap usually doesn't. In a perfect setup a cap shouldn't be necessary, but there will never be a perfect setup unless you wired up 100% of the vehicles electrical system with top priority on supplying massive power to amps leaving everything else in the background.Even if you did have the perfect setup and a cap wouldn't be of any use, at least it wouldn't hurt anything either.Sent from my XT1565 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: May 01, 2017, 06:49:10 pm
content: Quote from: skarecrow on May 01, 2017, 01:47:02 pmYes, the unloaded voltage on a car's electrical system is 14.4V, when the engine is running. It will be much lower, with the engine off or with a large load.Where do you get drivers with such a low impedance from? I've had a Google and can't find much below 4Ohm.Quote from: yada on May 01, 2017, 12:15:12 pmI take your points regarding wiring and space. . .Unfortunately talking about audio always invokes a debate here.If it isn't for audio then why do you want a large capacitor?Different capacitors have different applications. Small super capacitors aren't designed for high power applications. Much larger super capacitors are available for high power applications but they're more expensive, than the little ones.

author: skarecrow
author_rank: Regular Contributor
timestamp: May 01, 2017, 07:09:19 pm
content: Quote from: Hero999 on May 01, 2017, 06:49:10 pmSoundqubed used to have a build-your-own-subwoofer thing where you could customize everything about your sub. The amount of coils, coil material, dust cap, coil rating, etc. Their mobile site doesn't seem to offer that anymore. Lowest I can find on their site right now is dual 2 ohm. A quick search foundhttps://www.parts-express.com/audiopulse-ax12q1-axis-12-quad-coil-subwoofer--293-620had quad 1 ohm subs.I'll admit .5ohm subs have never been popular, but they ARE out there. 1, 2, and even 1.5 ohm subs are easy to find.Sent from my XT1565 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: May 01, 2017, 10:22:19 pm
content: Quote from: skarecrow on May 01, 2017, 07:09:19 pmIt says it's rated for 2500W RMS but for how long?There's no way you can put that much power into something that size continuously, with no cooling fan and not cook it.Why can't they be honest about the specification?

author: skarecrow
author_rank: Regular Contributor
timestamp: May 01, 2017, 10:43:51 pm
content: Quote from: Hero999 on May 01, 2017, 10:22:19 pmYeah, I wouldn't trust the specs on that speaker. I've never even heard of that brand, and the magnet is pretty small. Was just the first one I found doing a quick search. I used to use 1st generation JL Audio subs. They were rated for 225 watts RMS IIRC, but could easily handle more than double that.Sent from my XT1565 using Tapatalk

author: BrianHG
author_rank: Super Contributor
timestamp: May 02, 2017, 06:55:26 pm
content: Quote from: Hero999 on May 01, 2017, 10:22:19 pm'Now I'm not saying that these woofers are properly specked'. Quad 1 Ohm, is that a 0.25 ohm woofer wired in parallel?Don't sub-woofers self cool, I mean they produce such a breeze within them if you have a small enough bass-reflex rear to open air for a cool breeze?

author: Zero999
author_rank: Super Contributor
timestamp: May 02, 2017, 07:42:21 pm
content: There will be some cooling of course but 2500W worth in such as small package? Highly unlikely. It also depends on the enclosure. You're right, a bass reflex enclosure will have some cooling but I still doubt it's enough. The driver might be able to handle that power level in the open air for a short length of time but that's not practical.

author: GoneTomorrow
author_rank: Regular Contributor
timestamp: May 02, 2017, 11:25:07 pm
content: Quote from: Hero999 on May 01, 2017, 10:22:19 pmProbably about 2ns.Pretty much everything in car audio is advertised by its peak power, continuous is probably an order of magnitude less.

author: mmagin
author_rank: Frequent Contributor
timestamp: May 02, 2017, 11:31:07 pm
content: Quote from: GoneTomorrow on May 02, 2017, 11:25:07 pmSounds like the same marketing people write this stuff as the copy on the boxes of handheld power tools. "3 HP peak" ... too bad that's more power than you can get from a 120V 15A outlet.

author: yada
author_rank: Frequent Contributor
timestamp: May 03, 2017, 11:07:01 pm
content: Quote from: mmagin on May 02, 2017, 11:31:07 pmI like the tools that say 2000W for use on 115VAC. They must not teach math in marketing school.1,000,000 RPM! 10,000 kw! 5,000 Amps! 900Hp! Diamond tipped titanium blades, micro processor smart motor! Can't wait to see that on the newest blender made in China. Insides a 20watt DC brush motor with stamped sheet metal blades and bridge diode for a micro processor.They do this because no one calls them on their shit or hey just look at the box and see that this number is bigger then this one, so it must be better.