Capacitors, and why we dont need them

Discussion in 'General Car Audio Discussions' started by Willy D, Dec 12, 2006.

  1. Hautewheeler

    Hautewheeler Full Member

    viking just loves talking about capacitors..
    I'm starting to think that a capacitor stole your lunch money when you were in school or something.. - (just kidding:) )

    so vik, say that you did not have a "taxed or overloaded electrical system", and you wanted to put capacitors on your system to "smooth out the spikes". can you ever see agreeing that this is not the anti-christ of all ideas? I have plenty alternator, plenty battery, and big enough power wire that I could scrap the wire and buy a new HU.., my amp gets plenty power, and puts out plenty power (it's got all kinds of caps in it).

    I have two 3farad capacitors and they are great.. my lights don't dim and my other electronics don't bitch about them, and the amp loves them. three years and I don't have any complaints except that the power wire fittings sometimes rattle loose from the vibrations, but that's it.

    I would not suggest that anyone use caps if they have not upgraded the electrical system, but after you have covered your bases, why not put them on.. if nothing else, the display is much more accurate than the voltmeter/ammeter on your dash, so you can keep a good eye on how your charging system is doing.:p
  2. TheViking

    TheViking Well-Known Member


    Bottom line, I wont use them...the money spent on a cap could be used towards an alternator, 2nd battery, etc.....

    They WILL not benefit a sytem enough to make a difference!!!! Do they Help? NO!!! Do they eliminate lights from dimming? maybe....BUT the ROOT CAUSE OF THE ISSUE is the lack of capability of the electrical sytem!!! That is the key element.

    Caps are an odd device really...... i like charging up the 1 farad jobs and blowing holes in the lids of Copenhagen cans!!!

    If a guy wants caps.....solder them to the board of the amp.....THAT is where they will benifit the most!!!!
  3. Hautewheeler

    Hautewheeler Full Member

    I absolutely agree that your money is best spent on alt, batt, wiring, quality amp, etc.. but after that is done, it is really not harmful to add a cap.

    plus they look cool, and you can do some interesting things with them for custom installs.
  4. TheViking

    TheViking Well-Known Member

    Interesting things huh?

    You like the caps in the shape of a butt plug?:lol:
  5. psycho_maniac

    psycho_maniac Full Member

    Id rather have a 2nd battery then install a cap. Mostly because they cost a lot more then it would cost to install a 2nd battery. Also when i first got my capacitor it looked like a giant double AA battery lol. I was like WTF!!
    Last edited: Apr 15, 2007
  6. mrmizcue

    mrmizcue Full Member

    i currently live in Indonesia ans there are not any alt's above 120 amps and that's what i had o get. Everyone here only uses 4 ga. power wire so when i wanted 1/0 took the shop 2 weeks to get it. I have a 3.0 cap and lights still dim- RF T10001bd So now i wait for a 200 amp relay to be found here (too expensive to have anything imported..shipping cost and 35% import tax) to have 2nd battery installed.
  7. pedro quiroga

    pedro quiroga Well-Known Member

    couldnt you double up on the 4 gauge if you had too?
  8. aznboi3644

    aznboi3644 Full Member

    two runs of 4 gauge is equal to one run of 2 gauge...but since you don't have the means of getting a huge alternator...use as much 4 gauge as you can
  9. mrmizcue

    mrmizcue Full Member

    i DID get the 1/ just took 2 weeks...but thanks...i was going to go with 3-4 runs of 4ga if 1/0 was not available. But before that i was going to try a welding supply store. multi runs was the last resort
  10. geolemon

    geolemon Full Member

    Seems like the real failure isn't what caps "do", but rather what the thread starter expects them to do. ;)

    After all - caps do what caps do.
    There's no scam in the electronics world... (what's next - impotent inductors? Scandalous semiconductors? lol) Really... you can't argue that they don't do what they do.
    The question is - what do you EXPECT them to do? ;)

    Arguing that money is better spent elsewhere has to follow that understanding, and this thread hasn't had any argument that used any discussion of what caps do - at all. None (scroll up!).

    Alternators turn mechanical rotation into current... which can be used to supply current to hungry amps, or discharged batteries.
    BUT - they have their limits.

    Batteries store current... which can charge, and alternately discharge when the limits of the alternator are reached (they pitch in the difference!).
    BUT - batteries are very slow, in terms of transient response.

    Capacitors aren't a voltage source, like batteries and alternators are.
    So - the question is - why would you confuse a capacitor with a voltage source?
    (the question is begged, since so many people have said "I'd rather buy another battery than a capacitor, for example)

    Capacitors use current (like any electronic device or semiconductor does), but in a different way. They charge - but NOT like a battery. They store current, but NOT like a battery. Maybe that's the source of confusion?

    Where batteries have a very high current discharge capability and a very slow transient response (speed to begin discharging), capacitors have a tiny current discharge capability and a very fast transient response.

    Where batteries charge to, and maintain a set voltage (which in our cars is lower than our normal operating voltage), capacitors charge to whatever the current peak or operating voltage the system is at at the moment.

    Those two facts define both what a capacitor can do for you in your system, and why capacitors and batteries work so WELL together in a car. ;)

    Namely - in the event that your system has a peak that demands more current than your alternator can supply - then the battery is called into action. But in order for that to happen, the voltage must drop from 14.4v to 12v. And then the battery must rise to action - it's transient response isn't quick.
    Consider the cap to simply help that hand-off happen. It can (and will) discharge, immediately as soon as voltage starts to drop from 14.4v, and while the battery is rising to respond.
    ...Sub-second stuff, yes - but that's why you see an (undeniable!) impact on dash and headlight dimming - voltage is only dropping from 14.4v to 12v - not below that because the battery is slow to respond... THAT "below 12v drop" IS abusive to your battery and electrical system, and a cap can help cushion that blow.

    Consider it a cushion, a shock absorber.
    Don't consider it a battery.
    Comparing it to one, or saying you'd be "better off with..." is simply ignorant! No denying a battery is nothing like a cap. ;)
  11. geolemon

    geolemon Full Member

    IMO, an electrical system should have:
    1) an alternator
    2) a battery
    3) a capacitor
    4) the "magic 3" upgrade
    5) possibly a second battery, if running tons of power
    6) possibly an upgraded alternator, if average current draw exceeds the rating of the alternator...

    ...but also be aware that "average current draw" depends on use: everything from average volume, your music selection, and amp efficiency. The louder you turn it up, the more current is drawn - and since the sub amp is most of the culprit, the more bass / longer the bass notes, the more current is drawn. And it's drawn actually only when the bass is hitting - as you can witness, watching your own headlight/dash light dimming.
    SO - a good way to measure is to note whether the lights are dim more than 50% of the time. If not, the batteries have enough time to recharge in between!

    (and technically, charge time is a bit longer than discharge time)
  12. Chasnsx

    Chasnsx New Member

    In 1992, when I put my first "high end" system (300 watts with 100 watts to four 8" subs) into a 1989 Civic, I started the car at night with the headlights on, and cranked it. I noticed that the headlights flickered a little bit on each bass transient. This was listening to rock, not the sub crushing hip hop we have now.

    Back then, hardly anyone made capacitors specifically for car audio use, so I scurried to the electronics surplus store and bought the biggest capacitor I could find (300,000 mfd, 20 volt) and wired it into place. Problem solved.

    A capacitor is a necessity on any single battery system to smooth out inherent current fluctuations. As far as their use in a dual battery system, let the debate rage on.

  13. adam_rockn

    adam_rockn Full Member

    this was really helpfull man, i didnt know that stuff
  14. manutdfan7

    manutdfan7 Full Member

    you guys are all so freaking smart its not even funny!!!!!!!!!!
    great posts
    great posts
    is all i can say
  15. Grasmo

    Grasmo Member

    Some very good points in here as stated earlier, some very smart people who know how to present their knowledge in a way that is easy for the common man to grasp.
  16. tadung

    tadung New Member

    Hi all, nice to see you all here.
    Hope that i can learn something interesting in this forum

    Have fun
  17. pedro quiroga

    pedro quiroga Well-Known Member

    caught you.. :cool:
  18. wallyjr

    wallyjr New Member

    I'm new here and I came across this thread and I have to add to it that my Dad had a 2000 Chevy CK2500 Pickup truck that he used for plowing our restaurant parking lot. He upgraded his truck with a rockford fosgate system of 2 ten inch woofers and four door speakers. When he tried to plow with it with the stereo on it would nearly kill the entire electrical system in the truck. The plow could barely pick itself up and the lights would shut off. He then added a pair of capaciters to his truck and he could plow with the stereo on and none of the side effects I mentioned. How did this work?
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    bridge0116 Guest

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