Capacitors

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Originally posted by seanjuan@Dec 15 2003, 08:50 PM
sounds like a damn text book
and i bet no one knows that shit.... I didn't and I've had two years of college phyisics and one year of circuits.... but that was a few years ago so chances are I knew it but just forgot it

I learned that last year in AP Physics (in HS)!
 
Originally posted by CRX-YEM@Dec 5 2003, 08:49 PM
Um I can see there is a lot of mis information here.

A capacitor is not a dead short when it's not charged I can assure you that.
A capacitor is some material of some unit of area seperated by a dielectric. In theory the cap should have no resistance but in fact they do.

When a capacitor is connected to a voltage source it will charge to the source voltage instantaniously which can draw a lot of current (if it's avaliable). in the case of using a car battery to charge the cap the potential to draw upwards of 50 AMPS Quesent current is possible, which could easily be above the ratting of the wires you might be trying to use and in the end actually melt the wires.

So a safe way to charge the battery and to limit current would be to use a series resistor connected to the voltage source and then to the Cap and then connecting the circuit to slow down the charge cycle and limit the current.

Charge Time
T=R*C
T is in Seconds
R is in Ohms
C is in Farads

Imax=V/R
V is in volts
R is in Ohms
I is in Amps

Power=V^2/R
P is in Watts
V is in Volts
R is in Ohms

So to safely charge your capacitor I'd say no more than 1AMP is a good
rule of thumb as a 12 gauge wire will easily be able to carry an AMP

so if your using a car battery the source voltage is 12V. now lets see what resitor will limit your current draw to one AMP

Imax = 12V / 12 Ohms
the problem here is the power dissipated by the resistor is going to be quite high using P=V^2/R, 144/12= 12 Watts
so you'd need a 12 Ohms 12 Watt resistor to safely charge the cap. which won't be easy to come by.

so we need to be a little more conservative and use a larger resistor to lower the power which will increase charge time.

1/4Watt resistors are really easy to find so lets see what's avaliable.

P=.25, V=12, R=? : R=V^2/P : 144/.25 = 576 ohms so double the value and look for at least a 1Kohms 1/4 watt resistor.

The quiesant current that will be drawn at initial charge up will be
I=V/R , 12/1000 = .012 Amps or 12mA this is a much safer limit.

The total time to charge the cap will be
T=RC for one time constant and it take 5 time constants to charge a capacitor to 95% of the source voltage.
so you're looking at T=RC : 1000Ohms * 1 Farad = 1000 seconds
for one time constant so total charge time will be 5000 seconds or 1.4 hrs.


|-------| (---------/\/\/\---------|
| |
|-------+Bat -Bat------------|

The capcitors symbol the | side is positve
+|(-


***** keep in mind do not hook this capacitor up backwards as it had to poles on positive and one negative, if you hook it up backwards you risk the chace of blowing it up *****

reference for symbols

The quiescent current draw of that capacitor would be when it was fully charged, caused by the ESR (equivalent series resistance) of the capacitor. That term does not apply to a charging or discharging state.

Also a capacitor labeled 103k would be a .01uf 10% tolerance.

The capacitor, if manufactured properly, will have a vent. If it is installed backwards in a circuit at or below it's rated voltage it will not explode, but the boiling electrolyte will come spraying out of the vent.

Resistor color chart

Capacitors
 
Originally posted by ktanaka+Dec 15 2003, 09:28 PM-->
@Dec 15 2003, 08:50 PM
sounds like a damn text book
and i bet no one knows that shit.... I didn't and I've had two years of college phyisics and one year of circuits.... but that was a few years ago so chances are I knew it but just forgot it

I learned that last year in AP Physics (in HS)!

:werd:

That was high school for me, along with freshman physics... and that was over 10 years ago (HS physics). I still remember that stuff, you should too!
 
QUOTE (liquid00meth @ Oct 28 2003, 05:13 PM)
Capacitors are wires in series with the regular power input of your amp. You send the power wire from your battery to the capacitor terminal, as well as all the power wires to the amp(s). So they all connect to the same terminal. Connect the ground wire of the capacitor, as well as the ground wire of your amps normally. that's all.


BUT, you MUST CHARGE THE CAPACITOR FIRST with a 12v hookup and a 1k resistor. Any stereo shop would probably be able to do this for you.

Here this is just to clarify a bit...




Its really simple.


in that diagram, the cap is in parallel, not series. typo?
 
Just remember that after you charge the capacitor, DO NOT TOUCH BOTH LEADS AT ONCE. If you do, someone will be waking you up later and the cap will be oozing liquid out of both ends.
 
***** keep in mind do not hook this capacitor up backwards as it had to poles on positive and one negative, if you hook it up backwards you risk the chace of blowing it up *****


Caps do some nasty stuff when they are hooked up backwards, on large caps there is usually a small plastic button for safety, if that pops out your in for trouble.
 
I remember reading somewhere on the web from a guy who is an car audio expert that capacitor is really a waste of money. He suggests that your money is better spent at buying a new higher amperage alternator. Upon consideration, I'm thinking about getting rid of my 1 farad cap on my system which pumps about 400 watts RMS. I haven't notice any different after I install the cap. My system is not louder. No problem with the blinking headlights when the bass hits before or after.

Just my 2 cents.
 
Originally posted by bigballer@Jul 23 2004, 05:20 AM
I remember reading somewhere on the web from a guy who is an car audio expert that capacitor is really a waste of money. He suggests that your money is better spent at buying a new higher amperage alternator. Upon consideration, I'm thinking about getting rid of my 1 farad cap on my system which pumps about 400 watts RMS. I haven't notice any different after I install the cap. My system is not louder. No problem with the blinking headlights when the bass hits before or after.

Just my 2 cents.
[post=367230]Quoted post[/post]​


A capacitor will not make you system any louder. that's not why it's used.
A capacitor hooked up in parallel with the battery is kinda like a water storage tower.

Your battry can only charge up to some specify limit, and can only have a draw of some maximum current. w/ the capacitor in parallel the capacitor also charges up to the same potential as the battery. When a larger amount of current is draw and the voltage of the battery drops when a deep bass note is being amplified the capacitor is there as a sort of reserve, allowing the system to instantaneously gain full potential.
In the long run it gets rid of the ripple in the DC line making it cleaner. The only major differnce that can be visual seen is if you had headlights that dimmedwon't as much. audibly you really won't be able to tell. The only time you could tell is if your system was drawing so much power that the cars charging sytem can't keep up. and your amp would actually cut out (no sound ) until the pwer is restored.

So if you say you didn't have a problem in the first place then you didn't need a capacitor. your vehicles charging system was capable of powering the system you have.
 
capacitors are definitley not a waste of money. The battery in your car is not meant to drain extremely quickly, and doing so only wears them out faster. A capacitor can absorb those quick spikes in power consumption, so the battery doesn't see much of a difference.
 
:withstupid: Caps are not a waste of money, even with a good alternator and batt sometimes the lights will still dim. Caps are used in everything from small power supplies to industrial applications for the same type of thing.
 
Capacitors do help a lot if you can't afford a new alternator. I got a 1.5 farad cap off eBay and it has stopped my dimming headlights and made my subs hit harder while the engine is running. This is with an Audiobahn 800 watt amp, so I'm sure if you have a 1200+ watt amp you would need more caps to see a difference. I come home from college every semester now and re-install my system. I used to use a light bulb to charge the cap until I lost it, now I just hook up the power directly to the cap, and it charges within seconds once I connect the battery. I haven't had any problems with melting wire or anything like that, I'm assuming that 4 gauge wire can handle those high currents.
 
im not that up on the tech side of car audio but i do know that some high end amps such as jl audio's have plenty of capacitance built in to them thus they run full power even when the voltage drops.i deduct that you reduce your chance of needing a high output alternator caps or extra batteries with these type amps,
 
Originally posted by acourt@Apr 25 2005, 03:55 PM
im not that up on the tech side of car audio but i do know that some high end amps such as jl audio's have plenty of capacitance built in to them thus they run full power even when the voltage drops.i deduct that you reduce your chance of needing a high output alternator caps or extra batteries with these type amps,
[post=491290]Quoted post[/post]​


Not correct. The JL amps supply constant power because they have power regulation circuits that condition the input power so that the amplifier always has a stable voltage to work with. They're not loaded up with capacitors.
 
I am one to belive that a cap is nothing but bad news to your cars electrical charging system. All the things said before are true, it does help dimish the power spikes when your at a stop light, or like situations. With out a resistor to limit the amount of current drawn then it will essentially be depleted after a long red light and will be getting charged, and uncharged, to feed the amp at the same time. Thus causing a larger drain on your electrical system. Of course this is just my opinion as to why I will never have a cap in my system.

What I would/ have done in my cars is:
1. Get a new/better battery. Optima red or yellow tops are usually preferred, depending on your desired result
2. Upgrade 'The Big 3'. This includes increasing the size of the wiring A. between the battery(+) and the alternator(+) B. between the battery(-) to the body or frame and C. the chassis to the engine block
3. Do all of the above with the larger then stock wiring.

More on upgrading the big three can be found here.

have fun
 
Quoted post[/post]]
I am one to belive that a cap is nothing but bad news to your cars electrical charging system. All the things said before are true, it does help dimish the power spikes when your at a stop light, or like situations. With out a resistor to limit the amount of current drawn then it will essentially be depleted after a long red light and will be getting charged, and uncharged, to feed the amp at the same time. Thus causing a larger drain on your electrical system. Of course this is just my opinion as to why I will never have a cap in my system.

What I would/ have done in my cars is:
1. Get a new/better battery. Optima red or yellow tops are usually preferred, depending on your desired result
2. Upgrade 'The Big 3'. This includes increasing the size of the wiring A. between the battery(+) and the alternator(+) B. between the battery(-) to the body or frame and C. the chassis to the engine block
3. Do all of the above with the larger then stock wiring.

More on upgrading the big three can be found here.

have fun

Holy bring an old thread back. But an alternator is the best upgrade because it supplys the entire car with power. It is what charges the battery, charges the cap and the rest of the electrical system when the car is running.
 
Quoted post[/post]]
I am one to belive that a cap is nothing but bad news to your cars electrical charging system. All the things said before are true, it does help dimish the power spikes when your at a stop light, or like situations. With out a resistor to limit the amount of current drawn then it will essentially be depleted after a long red light and will be getting charged, and uncharged, to feed the amp at the same time. Thus causing a larger drain on your electrical system. Of course this is just my opinion as to why I will never have a cap in my system.

What I would/ have done in my cars is:
1. Get a new/better battery. Optima red or yellow tops are usually preferred, depending on your desired result
2. Upgrade 'The Big 3'. This includes increasing the size of the wiring A. between the battery(+) and the alternator(+) B. between the battery(-) to the body or frame and C. the chassis to the engine block
3. Do all of the above with the larger then stock wiring.

More on upgrading the big three can be found here.

have fun


Caps are very beneficial in daily driven systems... they help smooth out voltage just as they do in any other electrical system...

the only case when they hurt is in the case of a competition system.. where you are playing test tones, which do not give the cap sufficient time to recharge.. and this makes them simply another drain as most mics now wont register anywhere nearly as fast as that capacitor will discharge...


<------ iasca, dbdrag, slap competitor since 2001..
 
caps are not a bad idea but typically, I dont' recommend them. No one here has really named their #1 benefit. Sure they stabilize voltage to a point, they help give extra power in short bursts when needed but they really help more so with ground loops and other feedback errors. For everyone saying they give x amount of watts... BS! They don't make power, they store power. In extreme competition (as stated above) they're more hurting than helpful because they try to recharge and end up pulling power away from the amps instead of giving more power to them. But in daily driving cars, they work for a small storage bin but I still believe a second battery will be 20 times better. Get a quality SVC or Optima battery and you'll get fast enough response that you'll be happy to listen to your 50 cent albums... with the occasional bass cd's.

I just realized how old this thread is but my point still stands. :D
 
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