Long Lived Topic Cap

A capacitor basically is just a shock absorber Scott. It will store a bit of extra energy it releases when the system demands it most, before the regulator can kick in and begin charging for the lost power.

If the goal is reduction of dimming due to sub amp draw, sure it helps some. However, if we have ample supply wire (power and ground), and a worthy amp we have no issues. So when we consider both of these factors, we will see that it is mearly a band-aid for an inefficient or insufficient install. We also need to bear in mind that the capacitor when drained, is also another load on an electrical system that is, we assume, overly taxed to begin with.

Large enough power and ground will eliminate excessive drain and heat caused by, and itself creating resistance.

Amps will have some capacitance as well. The better the amp, typically the better the internal capacitance. The capacitance is added to maintain controll of transient responce, and reduced THD. A sudden drop in supply current will increase heat in the unit, adding distortion, and reduce the ability of the unit to react swiftly.

Personally I would add a battery to an install, not a cap, if the sub were the targeted system. By adding a second battery we are increasing reserve capacity, and reducing the load on the alternator by 1/2. Not only that, but the alternator needs available voltage to create current. So we are eliminating the voltage drop making the alternator more effective and reducing the excess heat that would be caised by an available voltage deficiency to the alt. Basically what it boils down to is a doubleing of the alts ability to recover and essencially doubleing the reserve capacity and available current. Hmmm, all that adds up to longer battery life, longer alternator life, and a more efficient overall system. All bonuses .

I would never hesitate to suggest a small capacitor to the front stage however, to aid in transient responce.

Oh, whoever said it would take 22,000 1 Farads to make an 850 CCA batt is talking out their ass. Capacitors do not have the ability to create their own power, but batteries do. It would take 1 850 CCA battery to charge all 22,000 caps maybe , but where the batteries reserve is set in hours, the 22,000 caps are still only worthy of Mili-seconds of reserve. Which would you prefer?

 

SPL competitors don't count.

I dont' have time to do the long reply right now...
But ponder this, in the scope of REAL music (drone-tones don't count, Mr. SPL competitor.. )

The alternator can supply current up to some point.
Beyond that point, the additional current is drawn from the battery, which until that point is fully charged and not functionally present in the system.
When the alternator's current capacity is exceeded, it's voltage drops down from the 14.4v level it usually operates at to the 12v level of the battery, and then both combine to provide the needed current.
Because of this voltage drop to the 12v of the battery, you see your lights dim, because light bulbs are simply brighter at 14.4v than 12v. It's no indication of a problem

Usualy, the overage isn't really all that much, and the battery just recovers (back to full charge) in about the same fraction-of-a-second that you saw the lights dim. No biggie.

But consider that the battery is a relatively slow device, it doesn't give up current instantly, it takes a finite amount of time for it to ramp up it's current flow. Batteries are relatively slow to discharge, and relatively slow to charge. Deep-cycle batteries are worse... their thick plates that make them durable and able to survive deep-discharging for at least several cycles also make them slower to respond to current draw demands, and slower to charge.

So, when this switch-over happens (amp draws so much current that you exceeded the alternator's abilities for a moment), consider that the alternator's voltage is dropping because you exceeded it's capabilities. It reaches the 12v of the battery, and will actually continue to drop below that 12v level, because the battery doesn't begin discharging instantly.

If you had a capacitor installed, it is an inherently lightning-fast device. It is capable of discharging and charging virtually instantly, by nature. Hence why they supply resistors to initially charge a cap with... it would try to draw so much current in such a tiny fraction of a time to charge itself that it could discolor or even weld the terminal to the top of the cap. Powerful stuff, by virtue of speed.

A capacitor also charges up to the voltage level of the vehicle. It'll be charged up to 14.4v.
As soon as the voltage drops below 14.4v, the capacitor begins behaving as a source... more of a current source, than a voltage source though. By nature of it's quick-discharge capabilities, it's able to fill in that gap, supplying current as the alternator transitions downward to the level of the battery, and covering the lag where the battery hasn't ramped up to full discharge. And by the time the battery is up to speed, the capacitor is generally virtually discharged.. fraction of a second.
But that's OK, it recharges just as quickly, when voltage rises back to 14.4v. B)

Helpful?

But no, you - and your deep cycle batteries - can go back to SPL-land, you blasphemer! :lol:

 

Oh really, no SPL this year?
Actually, I think you DID mention that before.. sorry. :lol:

It's not a band-aid for an alternator, if you don't need an alternator.
It'll help the amp work without real penalty during those headlight-dimming times.
Again, I stress that there's no harm in that alone. That just is a sign that your electrical system is doing what it should.

Audible?
If it was your midrange/tweeter amp causing the dimming... then hell yes!
But since it's usually your sub amp - and since most people can't even hear between 5%-10% distortion in those bottom octaves - it's not likely to be very audible.
But on the same note... what would be your argument for running an upgraded alternator? That certainly won't cause an audible difference, system running at a level causing dimming "before", compared to system running with new alternator raising the threshhold.

I'd personally never install one in my daily driver / SQ system, because it's a HP robber ALL the time, just to provide enough current to stop your headlights from dimming SOME of the time... and if the headlight dimming isn't a problem anyway (your average current draw would need to exceed the alternator's output capacity really, not just your peak current draws ), then why spend the money to lose the horsepower (and gas mileage... just "engine efficiency", really)?

Do you think your average current draw is exceeding your alternator's capabilities? The typical system's average current draw is around 20a-30a.. how are you surviving in there? :lol:

 

And with that the world has come to an end :lol:

 

Not to be a smartass because I always respect your opinions, but isn't the alternator only device in the car that can generate current to create power?

 

No. The chemical reaction in a battery generates it's own power. Doubt it? Put a load on a battery and watch the voltage across the terminals drop. Next, remove the load and watch the battery regain voltage potential.

The alternator in fact cannot generate power without the battery. Remove the power wire from you alternator and tell me how well it charges.

Thereby making my statement 100% accurate, and taking it a step further.

A battery IS the ONLY device on a car capable of creating it's own power.

 

K, educate me a bit more then...

When you say creating, do you mean generating or supplying? It is true the battery supplies the power (voltage x current) within its capacity (incidentally measured in units of power, Ah) but once that capacity is discharged, you do need the alternator to recharge it (ie feed it with current) to keep the current flow out of the battery or am I wrong about it? Otherwise, why would you need the alternator? There must be something to what I am saying since there is a term, battery capacity?

Oh and BTW, power is current x voltage but it is also work/time so there is no reason whatsoever why alternator cannot generate power... Not good for the computerized cars these days but once the alternator starts working, you can disconnect the battery...

 

It is capable of both creating and supplying, however it ability to create is quite limited.

The battery will redevelop a charge to a certain extent as well, through the particulate transfer mentioned above.

Have you ever had a car that wouldn't start and you cranked it untill the battery would not crank it anymore? Then you go inside cursing the car out and come out an hour later, only to find the battery is cranking the car just as well now, 1 hour after you drained it dead, as it did just before you killed it?

However, as we continue to discharge the battery, the loss of lead sulfate from the plates and the absorbtion of the acid in the plates and out of the electrolite goes beyond the capacity required to self-charge, or surface charge. When this happens it needs some help dumping the lead back into the plates and the acid back into the electrolite. That is when a charge is required. And basically that is what the alt is there for. It eliminates excessive losses from the plates and electrolite, as well as maintaining a constant voltage in the vehicle.

As far as removing the battery cable, sure that will work. But why don't you remove the power terminal from the back of the alt? It will not generate it's own power is why. When we start the car we have provided a charge required to get the alternator working and generating power. When we remove the battery cable we still have power recirculating through the system into the alt's supply side. To eliminate outside power supply we would need to eliminate external voltage/current from entering the alt, so we remove the power wire from the alt. Bang, dead... without externally supplied voltage the alt will not generate or supply current.


It is a symbiotic relationship, and one is needed for the other. However, without an outside suppply of power, the alt is useless. Without the alternator the battery is still useful, however on a very limited scale of course.

 

Right, what you are saying is that:

1) a battery can create it's own power (through electrochemical reaction), but really only on a limited basis... and recovering, but not fully recovering.

2) an alternator needs something to be turning it, like your motor. Without something turning it's pulley, it won't make an ampere.

 

Well, kinda... The alternator also needs an applied voltage as well.

 

LOL, I need the input on my thread but I ain't gonna get none since you guys are busy somewhere else... Between both of you I get so much info that I would not get anywhere else but I still need subs...

So I guess I have to run winisd and rely on the results...

 

LOL, I'll go look there Peter. Gimme a second.

 

hey, I just posted there!
This is no time for criticism!