# Do capacitors go bad?



## Machine7 (Nov 17, 2010)

I have two .5 farad capacitors that are 15 years old
One was used for a year or two and the other has never been juiced up

Is either one or both in danger of leaking if I start using them now?

I heard that capacitors in electronic devices swell over time - granted the mention was in relation to car receivers that sit too long.


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## UNBROKEN (Sep 25, 2009)

Figure out why you think you need a capacitor...and address that problem. Then throw your paperweights away.


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## Darth SQ (Sep 17, 2010)

From what I understand, you're comparing apples and oranges even though they're called the same thing.

Your caps are not the same as the one's inside amps with the problem of leaking overtime.

Bret
PPI-ART COLLECTOR


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## steffanan (Dec 9, 2010)

ok, i dont know what these guys are saying exactly, so im just going to answer your question. capacitors don't really leak, like you said, they go bad, and very occasionally swell. your only way to test, is to put power into them, put a voltage meter on them, and see if they hold voltage. if they do, use them, if not, throw them away cause they are good for nothing. what amplifier (s) are you using? do you know that you actually need capacitors hooked up, or do you need more power from your alternator, or more reserve power? capacitors are almost always used wrong, because people take them for being an extra battery of some sorts, when all they really do is stabilize the voltage from your battery, or from the left over ac ripple from your alternator. its a common rule of thumb to only use 1 farad of capacity per 1000 watt amplifier, so the chance of you actually needing two is slim.


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## steffanan (Dec 9, 2010)

btw, the chances of the one that has (never had power through it) to be in any better condition than the one that has been used is slim, because it would only help if it literally never had power go through it. most capacitors are tested in the factory before they go out, and can only pass qc if they work correctly


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## Machine7 (Nov 17, 2010)

Ok thanks for the tips- I was more concerned that one that had been used would go bad.

As for why I think I need one:

Headlights/interior lights dim slightly on bass hits

I knew this question was going to cause a stir- people get really upset with the idea of caps... but I have read from what seem to be authoritiative and reputable sources that it makes a difference if lights dim slightly with bass hits. I figured that I have them- why not use one? At least it may even out the strain on the car for now.

I have a plug in voltimeter that goes in the acc socket. I can watch it with the system cranked both with and without the sub and report back... I don't want to damage my car's electrics, but no I haven't added up my fuses and tried to see what is left over for the system. At least not yet... modern cars fuses are everywhere and I loathe to go yanking panels everywhere trying to add em all up. Is there an easier method?

2011 Honda CRV w/heated seats

System:
Pioneer x930 bt
JBL MS-8 driving front tweets
Zapco I-Force 450.4 driving HAT Clarus 6.5's (front stage only)
Kicker 400 watt mono D driving Image Dynamics 12" (I recall two sets of terminals bridged on the sub - so 4 ohm? 8 0hm?)

Thanks for the pointers all


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## Machine7 (Nov 17, 2010)

one more thing...
my sub box is sealed 1.3 cubic feet or so...
and it's not quite sealed- what I mean is that if I push on the sub speaker, I can cause the speaker to compress into the box. At first I feel resistance/push back from the pressure, but then the pressure escapes, and there is only the resistance of the rubber surround and speaker components. When I let it go it slowly fills back up.

I'm sure this could contribute to more power consumption if not some degree of bass response degredation. 

I bought the box and sub used and the seller shipped using brads to tack ferring strips of wood to protect the speaker. I'd have to seal out the speaker terminals (silicone? liquid nails?) and possibly the speaker to box itself... somehow (gasketing sealant?)... and maybe shoot or our polyurethane into the box to seal out any holes left by the brads? 

How important is a perfectly sealed box?


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## steffanan (Dec 9, 2010)

Machine7 said:


> one more thing...
> my sub box is sealed 1.3 cubic feet or so...
> and it's not quite sealed- what I mean is that if I push on the sub speaker, I can cause the speaker to compress into the box. At first I feel resistance/push back from the pressure, but then the pressure escapes, and there is only the resistance of the rubber surround and speaker components. When I let it go it slowly fills back up.
> 
> ...


ill answer this part of the question first, as far as what to do with your sub box.

pull the sub out, and take silicone to the insides where ever there is air leaking through. its good to try to get around the terminal cup where the wires go through, but make sure to not get it all nasty in there, because it will suck to hook wires up to it then. so, once you have sealed the inside of your box, you really need to decide if your sub is mounting to your baffle correctly, like... you need to see if any air is coming out right around your screw holes. last last last resort is to use silicone on the actual sub. a couple ideas, use some carpet or sound deadening around the hole to make a gasket for the sub to mount onto. also, you can get some rubber strips, or foam strips (for example, that are made to seal garage doors) and mount your sub down onto a ring of that stuff. if you had the tools, i would say to basically measure the baffle of the box, cut out a new square, cut a new sub hole, and mount it onto your existing box, to double your baffle, and also the hole wouldn't leak. you could carpet the board before you put it onto the box also. so yeah, its pretty important to get your sub sealed up, but its actually not going to have much to do with your power consumption.


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## steffanan (Dec 9, 2010)

Machine7 said:


> Ok thanks for the tips- I was more concerned that one that had been used would go bad.
> 
> As for why I think I need one:
> 
> ...


well, the reason that it causes a stir, is because capacitors are almost used incorrectly as a band aid, or as a battery. they don't really do either job very well. technically, with proper installation, with a good factory battery, alternator, and proper wiring throughout, a capacitor shouldn't do anything at all to help the system as far as the dimming lights goes. however, since there are so many variables, sometimes they do help dimming lights. what i can tell you though, is that you for sure don't need them both hooked up. and you are correct in the theory of "if i have it, why not use it" AS LONG AS: the capacitor is 100% healthy and can hold its voltage for a long time. so the way to test that, is to hook it up to 12 volt power for say 10 minutes, and then unhook it, and put your voltage meter on it. it should say 12.9 or something, and check back in 10 minutes, and see how much it drops. basically, if your capacitor can't keep a higher voltage than your amps are seeing at all times, it becomes one more thing for your alternator to have to charge, while its also trying to power a full system. a bleeding cap takes in power and doesnt give it back, just like amplifiers do.


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## Swanson's Performance (Mar 27, 2011)

While just skimming the surface of knowledge of some people on here, let me give my take:

Capacitors resist a change in voltage potential. This capacity (ha!) is measured in farads, and basically the bigger the number, the longer it can resist voltage droop. This helps to smooth out small ripples on the feed, but a continuous drain that is larger than the supply will pull the voltage down, and cause an increase in current (Ohm's law). I'd guess the thinking is, increase your supply to have enough in reserve and exceed any possible requirements, and eliminate the capacitor entirely. But, then again, I only have 13 posts here.

FWIW, broken down into it's simplest idea, a capacitor is only two conductors with a dielectric between them that can hold (maintain) a static charge. The dielectric can be oil, air, or many other materials, so whether or not yours can "blow up" is highly dependent on what type they are. Sorry that's not really descriptive.


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## dragonrage (Feb 14, 2007)

Swanson's Performance said:


> While just skimming the surface of knowledge of some people on here, let me give my take:
> 
> Capacitors resist a change in voltage potential. This capacity (ha!) is measured in farads, and basically the bigger the number, the longer it can resist voltage droop. This helps to smooth out small ripples on the feed, but a continuous drain that is larger than the supply will pull the voltage down, and cause an increase in current (Ohm's law). I'd guess the thinking is, increase your supply to have enough in reserve and exceed any possible requirements, and eliminate the capacitor entirely. But, then again, I only have 13 posts here.


When the capacitor does get drained - which will be VERY quickly - it will then act as a near-short to the alternator, which will then present an even greater load to the charging system and make things even worse.

To the guy who suggested silicone above: Note that you must let it cure completely before letting your subs come in contact with the box. It outgasses and it is bad for your subs.


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## Machine7 (Nov 17, 2010)

dragonrage said:


> When the capacitor does get drained - which will be VERY quickly - it will then act as a near-short to the alternator, which will then present an even greater load to the charging system and make things even worse.
> 
> To the guy who suggested silicone above: Note that you must let it cure completely before letting your subs come in contact with the box. It outgasses and it is bad for your subs.





dragonrage said:


> When the capacitor does get drained - which will be VERY quickly - it will then act as a near-short to the alternator, which will then present an even greater load to the charging system and make things even worse.
> 
> To the guy who suggested silicone above: Note that you must let it cure completely before letting your subs come in contact with the box. It outgasses and it is bad for your subs.


Ok with my 12v multimeter plugged into the acc socket I'm reading 14.15 or so volts at idle with seat heaters, blower fan and headlights on. It drops momentarily to 12.97 when heavy bass hits on a demanding track (lots of mid and constant bass hits). With a/c on (defrost) and rear defroster I'm in 11.6 territory. Yikes!

So can a 1 farad cap help me?? Lol jk

Hmm... So I need a bigger alternator??! 
At least I know I've got good power wires!

At 4k rpm I'm hardly dropping south of 14v so just drive fast and/or raise idle speed! ha ha

I noticed that once I brought the system to more of where I tend to listen to it, and particularly while driving, it never went below 12.9

So would a .5 farad cap be of help for my more normal listening experience? It seems it would, but then do I run the risk of more greatly straining the cars electrical components if I am at idle and do crank the system?


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## steffanan (Dec 9, 2010)

if you wouldn't mind paying for a new alternator, yeah, thats great, get that, but usually people don't want to do that for such a small system (no offense lol). i would say that if that capacitor is good, go ahead and use it, but yeah, those voltage drops will still happen, and that capacitor will still only do the job of capacitors, and won't change that. what i would reccomend, is to get a battcap or seprate battery in the back, or even in the front if you can. If you hammer on your system for long amounts of time, the battery will only work for a while, but usually, since stock alternators are only made to power the vehicle and the vehicles factory components, the alternator technically isnt sufficient for ANY aftermarket stuff. so TECHNICALLY, everyone to ever get an amplifier should probably get a new alternator. but in real world application where people don't have crazy amounts of money, and where people don't rail on their system long enough to drain the battery at one time. also, to the guy above, i dont know what type of silicone you use, but nothing i use is so strong that its gases can break apart any thing on a sub. i think thats a little crayzay! no offense


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## Machine7 (Nov 17, 2010)

Thanks for the advice gang... This idea of a cap causing a "near short" effect in relation to the alternator has me concerned. 
What are acceptable voltage drops for running a stereo and other accessories?
And how do i determine the severity of a near short condition?


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## steffanan (Dec 9, 2010)

Machine7 said:


> Thanks for the advice gang... This idea of a cap causing a "near short" effect in relation to the alternator has me concerned.
> What are acceptable voltage drops for running a stereo and other accessories?
> And how do i determine the severity of a near short condition?


ok, so did you ever test how it holds voltage like i mentioned above? did you hook it up to power for a while, and then see if the voltage slowly drops? you keep doing voltage tests in your vehicle to determine wether you need more power, and thats not really related to the cap. all these scary things we are saying about capacitors, only apply if the capacitor is bad. so, do what i say, and check if its bad lol!


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## dragonrage (Feb 14, 2007)

That's a pretty big voltage drop. You can't band-aid that sort of drop with a capacitor (at least not in the wintertime). If the voltage drop is bad enough to measure with a DMM (Inexpensive DMMs are *MUCH *slower than scopes!) You might be able to with a good battery like Deka Intimidator, Odyssey, Kinetik, XS Power, etc., but an alternator would be best.


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## bhammer (Dec 9, 2011)

Machine7 said:


> It drops momentarily to 12.97 when heavy bass hits on a demanding track (lots of mid and constant bass hits). With a/c on (defrost) and rear defroster I'm in 11.6 territory. Yikes!


Down to 11.6? With everything powered off, what is the static battery voltage of your battery?


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## Machine7 (Nov 17, 2010)

Static voltage with engine and stereo off is 12.9 or so. At more normal listening levels, with less aggressive bass tracks and the engine at idle I'm hangin around 13.5-14 so I think I'm alright for now... 

I just read a couple of thorough topics on here regarding capacitors. I have a much better understanding now of the dynamics of powering a system. No wonder so many amps are sold with what I consider a relatively low wattage. With higher wattages, there is greater current demand (in addition to potential for rattles).

Right now I have to get my front stage into better form before everything else I think.

I want to run a rear stage, but obviously can't if I'm going to lack alternator strength. 

I'm running an MS8 with 6.5 clarus speakers and the tweets are too bright, the stage too narrow and low, the mids don't kick hard enough for my liking. I have to play with a set of scan speak tweeters, different tweeter axis, and consider splitting the amp back to 4 channel to power em seperately so I can dial em down and allow the midrange to come up a bit to counter the effects of the MS8 cutting gain to the mids to balance the MS8 powered tweets.

This is all kind of fun up to a point, now it's kinda a pain... it requires more fiddle time than I have!

Add to that I think I may have a blown sub (it squeeks at anything above mid volume level) and I think a better quality sub amp would help (better internal capacitors and power delivery).


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