What's the rated output of a d series alternator?

I also would look at what kind of amps your running is your 900-1kw rated power or actual power?

Most newer alternators put out at least 80-110 amps. 90 *14.4 = 1296watts

Assuming your not running every electrical device in your car at once there is more then enough there to run a stereo.

1kw is what I would say is the border line case.



Modified by nsxxtreme at 7:16 PM 10/12/2006

 

if you want to stop your dimming lights put the capacitor on the lights instead


seriously though?
try a trunk mounted battery. it is the only thing that will really help. all a cap does is put continuous strain on your alternator and will probably eventually wreck your diodes because of the turn-on surge.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote">if you want to stop your dimming lights put the capacitor on the lights instead


seriously though?
try a trunk mounted battery. it is the only thing that will really help. all a cap does is put continuous strain on your alternator and will probably eventually wreck your diodes because of the turn-on surge.</TD></TR></TABLE>

You have that backwards.
extra Battery = extra load on alternator.
Caps load is low compared to an additional battery.


Modified by nsxxtreme at 7:07 PM 10/12/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">What's the rated output of a d series alternator?

I also would look at what kind of amps your running is your 900-1kw rated power or actual power?

Most newer alternators put out at least 80-110 amps. 90 *14.4 = 1296watts

Assuming your not running every electrical device in your car at once there is more then enough there to run a stereo.

1kw is what I would say is the boarder line case.
</TD></TR></TABLE>

D series alt? I think it's 60 amp stock

Amps I was running? Boston GT-24 (900RMS @ 2ohm) and a PPI pc250 (50x2rms).

So to answer your question, yes rated rms power, not actual power, at least not with that alt

 

At 60amps I would invest in a new alternator.
Its capable of 864w not enough to run a 1kw system and your car.

 

System has been stripped to make way for new car. Not a problem anymore

 

I double checked the connections. They're all good. I'm running 4 ga wires for power and ground.

The specs on the cap are:

Capacitance: 1.5 farad
Surge Voltage: 20VDC max
Rated Working Voltage: 16VDC
ESR: less than .00195 at 120Hz 25degrees Celcius

Since it is above the recommended .00175 for the ESR, should I get another cap? Or is the above spec okay?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">I am not sure what you mean by "put the cap between the batt. and amp"

You are correct you want the cap as close to amp as possible, power cable to caps pos.(+) terminal, from caps pos.(+) terminal to amps pos.(+) terminal, ground cap at the same point the amp is grounded to. make sure it is a good ground, [most problems with amps is ground related] where is the amp/cap grounded now?

I also agree with nexxtreme "or a crappy cap", I would test the cap.

Also check batt. connections, and batt. to chassis and chassis to motor/tranny ground connections, definitely "beef up" the batt. to chassis ground.

What gauge is the amps power and ground lead and what kind of fuse are you using on the lead, where is the amp mounted? 94</TD></TR></TABLE>

I have the cap set up next to the amp, which is under the driver's seat. The power wire goes from the battery to the cap, then the cap to the amp. The ground for both the cap and amp is on one of the seat bolts. I sanded away the paint and made sure that good contact was being made. The fuse is a 60amp 30V fuse. I also cleaned the battery terminals.

The lights still have the same flickering effect. I guess the next step is to test out the cap.

Thanks all for the inputs.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by P Nut &raquo;</TD></TR><TR><TD CLASS="quote">
The specs on the cap are:

Capacitance: 1.5 farad
Surge Voltage: 20VDC max
Rated Working Voltage: 16VDC
ESR: less than .00195 at 120Hz 25degrees Celcius

Since it is above the recommended .00175 for the ESR, should I get another cap? Or is the above spec okay?

The lights still have the same flickering effect. I guess the next step is to test out the cap.</TD></TR></TABLE>

plug the ground of the cap into the ground terminal of the amp.

The ESR value if accurate is not bad.

You stated that your stereo worked fine and then started flickering so you added a cap. Have you done "the Big 3" as others have suggested?

I still think you have bad wiring or a bad cap.

Possibly a bad or weak alternator. This can be easily tested by taking it to some place like start smart where they can load test your alternator.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">

plug the ground of the cap into the ground terminal of the amp.

The ESR value if accurate is not bad.

You stated that your stereo worked fine and then started flickering so you added a cap. Have you done "the Big 3" as others have suggested?

I still think you have bad wiring or a bad cap.

Possibly a bad or weak alternator. This can be easily tested by taking it to some place like start smart where they can load test your alternator.</TD></TR></TABLE>

The "Big 3" was my next thing to do on my list for this weekend. I was trying to find a good write-up, but I think it should be all self-explanitory? I mean, all I'm doing is beefing up the wires for the alternator, battery and engine, right?

I'll redo the wiring for the grounding, as well.

 

There is an article someone wrote that is decent. I don't know what it is but you might do a search or maybe someone will come in with the link.

 

So what exactly causes dimming lights, and what's the best way to get rid of it? I thought if an amplifier pulls too much current it would cause light dimming. Heh funny how the other guy isn't responding no more.

Edit: Isn't there a still big debate on if caps work or not?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">No I am actually a real engineer.

Your next step is a waste of time and money. Audio industry loves people like you fills there pocket books nicely.


So simple it flew right over your head.</TD></TR></TABLE>

Priceless response. I actually laughed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">You have that backwards.
extra Battery = extra load on alternator.
Caps load is low compared to an additional battery.


Modified by nsxxtreme at 7:07 PM 10/12/2006</TD></TR></TABLE>


well my reasoning for the battery vs. the capacitor is that the capacitor has VERY LITTLE storage compared to that of a battery. the lights are still dimming with the cap in place because the cap can't keep the charge, right? Right.

In SPL competitions, do those guys load up their trunks with capacitors or batteries? I think it's batteries.

As for which loads a battery more, a cap or battery, that is the least of our worries. We are already loading the alternator with killowatts of power drawn by the amplifiers, while the load imparted by either a cap or battery is nil compartively.

The only thing that would be able to handle the current demands would be a battery.


Let's try a little numerical experiment:

The formula for the charge held on a capacitor is: Q = C*V
where Q is the charge in Coulombs
C is the capacitance in Farads
V is the voltage across the capacitor in Volts

Let's start with a fully charged cap. This implies that there would be a total charge on the capacitor of Q = C*V = 1*13.8V = 13.8 Coulombs

A typical big subwoofer amplfier would have a 50 or 60 Amp fuse. Mine has 90, but it's a class A/B and some of you guys use Class D (don't get me started on that topic) which are more efficient. A typical "bass hit" wouldn't use the full 60 Amps however ... probably more like 20 amps.

Furthermore, lets say that a "bass hit" lasts 0.5 seconds, but it's not full amplitude for the full 0.5 seconds, so let's take half of that. Thus we'll perform our calculation over a period of 0.25 seconds.

The total charge that the amplifier is pulling in the 0.25 seconds is as follows:
20 Amps = X Coulombs / 0.25 sec
X = 5 C (C is for coulombs)

So, we can calculate the voltage on the capacitor after a draw of 5 Coulombs as:
V = V0 - deltaQ/C
V = 13.8V - (13.8C - 5C)/1F
V = 13.8V - 8.8C/1F
V = 13.8V - 8.8V
V = 5 Volts


So, our little capacitor dropped to 5 volts from 13.8 volts over a period of time spanning 0.25 seconds with a current draw of 20 amps. Now, of course there is charge flowing into the capacitor while this is happening so the voltage wouldn't actually drop to 5 volts in a real world situation. I just hope this illustrates how little storage there is in a capacitor. I could run my amp off a lone battery at full power for probably a couple minutes at least, but not from a cap.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote">well my reasoning for the battery vs. the capacitor is that the capacitor has VERY LITTLE storage compared to that of a battery. the lights are still dimming with the cap in place because the cap can't keep the charge, right? Right.</TD></TR></TABLE> yes and no, more on this later.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote">In SPL competitions, do those guys load up their trunks with capacitors or batteries? I think it's batteries.</TD></TR></TABLE>
These guys are looking for huge amount of continuous reserve power. Basically they need more power then there alternator could ever produce. A battery is the only place to get large amounts of reserve power. Kinda of like a muscle car, they dont need to go around corners or be reliable they just need to go fast in a straight line.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote">Furthermore, lets say that a "bass hit" lasts 0.5 seconds, but it's not full amplitude for the full 0.5 seconds, so let's take half of that. Thus we'll perform our calculation over a period of 0.25 seconds.</TD></TR></TABLE>
The problem with these calculation is they require that the cap to be "filled" once per bass note. This is not the case, the capacitor is being "filled" by the alternator many thousands of times per bass note. You have a trade of off who is doing the work bewteen the the alternator and the capacitor. Most of the time the work is being done by the alternator. Since the Alternator produces AC its not always doing the work. Now if the continuous current demands needed to produce that bass note exceed your alternators ability the cap wont do you any good.

A good analogy might be a sputtering water hose. If you bought a bucket (cap) and sized it properly so that the bucket would fill in when the water hose was off (sputtering). You would have a nice continious stream of water.

Its usually the instant the bass note hits that you lights flicker. If you have a long bass note that goes on and on and makes your lights go dimmer and dimmer. It doesn't take a genious to figure out you continous current demands exceed your alternators ability to produce current. If you have an 80 amp alternator and you add a cap you still have an 80 amp alternator. But.......that will be a stronger 80 amps because you will not have holes. An amplifier is usually switching at 44kHZ or above. If its sees the voltage drop it is going to pull more current in order to keep its voltage constant. If you have a continious voltage level the power supply will not have to work as hard.



Modified by nsxxtreme at 12:00 PM 10/13/2006

 

he has a cap
the lights are dimming
we can conclude that the cap does not have enough reserve for the bass hits
a battery has more reserve than a capacitor
therefore get a battery


Now, if he hasn't done the-big-three then, yes, that is the first place to start. In my experience this does help dimming issues but does not completely resolve the problem.

Now, you are saying that SPL competitors use amps because they are drawing more per unit time than an alternator can handle. Yes, this is exactly true. However, I stated that they use batteries, not pre-filled capacitors, and that there is a reason for this.

You also stated that "Now if the continuous current demands needed to produce that bass note exceed your alternators ability the cap wont do you any good." This is correct. This is exactly why I dont bother with caps. It's because IN THE NARROW WINDOW OF TIME wherein the amplifier demands huge current it will always exceed the alternators ability + capacitor reserve. In this window of time, the output voltage of the alternator drops (due to its source resistance), and the headlights dim. If you have a big enough reserve (ie, one that DOESNT DROP BELOW 12V) at the power terminals of your amplifier then the alternator's peak voltage will not drop considerably. There would not be as strong a potential across the power wire and thus not as high a current would flow.

I never bothered to check the prices of caps, but a yellow top is cheap IMO, and in my opinion they do a better job at feeding the amp under peak demand.

As with the sputtering hose analogy, envision a vacuum on the end of the hose which is being turned on and off. In the period of time that the vacuum is on, it is sucking so hard that it sucks the bucket dry. In the period of time that the vacuum is off the water supply was not able to fill the bucket enough for the NEXT big suck. So even a bigger bucket wouldn't help because it is the source of the water that is not able to keep up with the incredible demand even though its over a short period of time. Now you may think that just get a DAMN HUGE bucket and let that puppy fill up and that vacuum will NEVER run it dry. Well, if you let it run for an infinite amount of time, it WILL EVENTUALLY run it dry. Then, the problem of light dimming begins

 

Your looking at this narrowly your trying to suck the cap dry. The cap will never be empty so long as the alternator is running and producing up to its current capacity.

Your making a situation where no power level is enough. In your situation your battries would run dry also. Your "sucking" more power then you can produce. It doesn't matter how many batteries you add they will eventually run dry. Plug an extension cord into your car a drive around and you will never go dry.

A proper electrical system is one in which you use the power you produce and can reliably reproduce. You should think of it as a complet sytem not as a single piece. Unless you are going after a specific task. A drag car tries to get to the end of the street as fast as it can, they carry maybe 2-3 gallons of gas. SPL competitor tries to go as loud as they can and aren't worried about running for extended periods of time.

Alternator, Cap, wire, Battery all work hand in hand to produce a reliable energy source. A good battery is an essential piece to the electrical system but its not the only piece. I would not go out and get a second battery unless I was looking to run for long periods of time with my car off.

A battery produces 12V an alternator produces 14.4V there is a 2.4V difference if you are running on the battery your lights are definetly flickering.

We must also remember that a alternator has a voltage regulator. It monitors the output voltage and corrects for any change in voltage. This takes time to do. The Cap will allow for a buffer for the voltage regulator to react to the change in voltage. You can think of the capacitor as a shock absorber.

When it comes to "increasing" sound quality or "spl" I would agree that a cap is not the solution. Most amps are regulated switching power supplies. They will pull more current for any drop in voltage. But for flickering lights it will help, but depends on the amount of flickering.

What is the voltage drop of a 100A sytem being driven entirely by your yellow top?


Modified by nsxxtreme at 4:50 PM 10/13/2006

 

I see the cap debate rages on, I agree with nsxxtreme

I have been a car audio installed for 30+ years, and have been installing caps on amps before there where "car audio caps", long before Stinger, Monster, EFX and others started wrapping their labels on caps and charging through the nose for them, even before there was car audio amps and suppliers like Stinger, Monster and EFX.
A properly installed cap will get rid of dimming lights every time, [assuming everything else is good] I have done this 100s if not 1000s of times and it has worked every time.
So from shear experience of doing it so many times, I know it works, anybody that says it does not, doesn't know what there talking about or has never done it properly. 94

 

yea my water analogy wasn't really correct. as time tends to infinity the battery would run dry also.

at least you recognized that caps do not have sufficient storage for SPL competitions and thus they use batteries.

and as for the voltage drop of a system running completely from the battery?

well, it wouldn't be running completely from the battery. there would be 2 batteries, plus the alternator. if you insist, the voltage drop (at the amplifier's terminals) would be equal to the the product of the current and source impedance + transmission impedance. i know that the source impedance of a battery is higher than that of a capacitor, but if you're comparing ONLY 1 cap to 1 bat then the cap will drain sooner. period. (unless you have a cap that is big enough that the storage is equal to that of the battery). anyway ... i don't know what you're getting at here.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote"> i don't know what you're getting at here.</TD></TR></TABLE>Who, me?

 

no nsxxtreme when he asked "What is the voltage drop of a 100A sytem being driven entirely by your yellow top?"

 

The ESR of the battery you mentioned is .0046 ohms.

So the battery produces 12v. 100*.0046=4.6V 12-4.6 =7.4V!!!

2 batteries would halve the impedence you still end up with a 2.3 voltage drop. And you will add a large load to the alternator. Current that could be used running your system is being used to charge the second battery.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote">at least you recognized that caps do not have sufficient storage for SPL competitions and thus they use batteries.</TD></TR></TABLE>
They serve no purpose in SPL competitions. You dont care about brief voltage drops in SPL competitions. This is a situation where you have a specific task and your optimizing your equipment to get the best results.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote"> but if you're comparing ONLY 1 cap to 1 bat then the cap will drain sooner. period. (unless you have a cap that is big enough that the storage is equal to that of the battery). </TD></TR></TABLE>
Your trying to compare a capacitor with a battery. Throw that thought out, they serve two different puposes. Lets go back to our water analogy. You have a 4000 gal tank of water 100 feet from your house. The tank has enough water to supply your house but it sits 100ft away. Now when you turn your water on you have to wait for the water to travel 100 ft before it start comming out of your spout. Even if we add a second 4000gal tank we still have to wait, but now we have two tanks to fill.

So how can you fix this? Lets say we add a 2 gallon tank right near your spout. So as soon as you turn the water on it instantly begins to flow. Now you no longer need to wait for your water. As long as the water from the 4000 gal tank reaches the 2 gal tank before it runs dry you will never notice an interuption in your water supply. The 4000Gal tanks has more then enough water to re-fill the 2 gal tank and keep supplying your house needs.

One of these days if I get time I will try to run some of my own tests. I'll have to make it a cut and paste document so I dont waste my time re-writing and posting each time this topic comes up.

 

^ very good explanation

 

I going to speak on everybody last thought.

We do not know the condition of the op car or charging system. A cap installed in a system thats not up to par in the first place is a band-aid. I not going to get tech because nsx summed it up 100% and there is no need to say it again. People need to take a look at there charging system before any sound upgrades. I had to may people want sound but there alt is only putting out 8-10 volts. go figure. Then wonder why there car is stuck on the side off the road. The problem on his car can be a bad battery. Now the alt has to run the car and the soundsystem. Or it can be both. Hell a loose alt belt. Bad termminals. All which would cause the problems that he has with a cap installed. Oyea check the block and tranny ground. You will be surprized how many times this has fixed so many problems

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">The ESR of the battery you mentioned is .0046 ohms.

So the battery produces 12v. 100*.0046=4.6V 12-4.6 =7.4V!!!

2 batteries would halve the impedence you still end up with a 2.3 voltage drop. And you will add a large load to the alternator. Current that could be used running your system is being used to charge the second battery.
</TD></TR></TABLE>

riiiiigghtt ... and when would a full 100A of current be pulled from a battery from an audio system? Even instantaneous, I don't know if it would ever happen because a lot of current would come from the alternator and the other battery under the hood.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
One of these days if I get time I will try to run some of my own tests. I'll have to make it a cut and paste document so I dont waste my time re-writing and posting each time this topic comes up.</TD></TR></TABLE>

Yea I was thinking the other day of performming the same experiment. I don't exactly have the means right now as my car was written off a couple months ago and am using my Dad's leased car. I would like to perform the experiment using a high-power real-world system (ie, don't just use load resistors). I don't exactly have access to a high-speed datalogger either, which I feel would be necessary to compare the voltage and current of the two systems. How about you?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote"> Even instantaneous, I don't know if it would ever happen because a lot of current would come from the alternator and the other battery under the hood.</TD></TR></TABLE>
My point here was, by adding 2 batteries you are saying "run the system off the battery because it can hold more current" In a running car the system never runs off the battery. If it only ran off the battery those are the voltages you would see. While the car is running the battery is constantly under charge. So it is consuming current not supplying it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by substrate &raquo;</TD></TR><TR><TD CLASS="quote">
Yea I was thinking the other day of performming the same experiment. I don't exactly have the means right now as my car was written off a couple months ago and am using my Dad's leased car. I would like to perform the experiment using a high-power real-world system (ie, don't just use load resistors). I don't exactly have access to a high-speed datalogger either, which I feel would be necessary to compare the voltage and current of the two systems. How about you?</TD></TR></TABLE>
I have this equipment although I dont think you need a data logger, an oscilliscope would work just fine.
I already know what the results would be. I started posting pictures earlier. I then deleted them because I dont have time to argue and finish these tests. On this forum things that are posted one week are lost the next, so it's somewhat of a waste of time.

I work a full time job as an electrical engineer and I just recently started going back for my Masters so I dont have much spare time.



Modified by nsxxtreme at 9:22 AM 10/17/2006