In need of good advice!

Ok, Here we go. I have a 2000 chevrolet silverado, ext cab. I just put in 2-12's in separate boxes facing down under the rear seats, running a kicker ix402 amp that is bridged..It sounds awesome. Nice tight bass. Clean sound. SO my Question is MY LIGHTS ARE DIMMING(lol). I have heard about caps, batteries and altenators....... So what do I do.. Upgrade the alt first, (i think they run at 80 amp output, and i have heard you can go up to 140+...does this hurt anything with that much output.....)then new battery then caps....I would really, Really be gratefull for any info on this .. Anyone who has the same truck and had this problem and resolved it let me know.....Thank guys.


Peter

If you buy a capacitor, you might not need a new alternator...but one of those before u do the rest to see if it fixes it. Even if you need i better alternator, it'd be to your benifit to have a cap anyway,plus it cheap.

You have 120 watts and your lights are dimming? There are only 2 explanations:
1 - your electrical system is shot...completely
2 - your gain is set WAY too high

Don't get a cap, they're a complete waste of money 90% of the time

..a new alt would be your best bet, if your electrical system is just really friggan weak and not busted, caps a crap

upgrade alternator and for future use when you get a proper amplifier I would get a deep cycle battery

People, he has 120 watts! With a properly set gain, he will be drawing AT MOST 15 amps at full draw! There isn't an alternator in the world that can't handle that, hell the headlights and foglights pull that much power from the alternator. Like I said before, either the entire electrical system is completely and utterly shot to hell, or his gain is set WAY too high.

The 2000 silverado has a 105-amp alternator. Now, you didn't say how you had the amp wired, but I'm assuming you have it wired for maximum draw, if not then these numbers will be slightly high. At 120W RMS @ 12V you are pulling 10Amps so at 14.4V you are pulling about 150 W RMS and around 10-11 Amps still. However, when the bass hits and your lights dim, you are placing a sudden current draw on the electrical system and can be pulling significantly more current, Peak wattage. This sudden draw lowers the voltage in the system and causes lights to dim, just like when the AC kicks on and the lights dim for a second in your house.

The alternator charges your battery as you drive down the road. The battery is the source for all your electrical equipment. This power is Not drawn directly from the alternator. What this means it that, while the alternator can deliver up to 105 Amps of continous output, the battery may not be able to burst you the power you need for such a short time when the bass hits. If you have ever messed with disconnecting the battery and see sparks come off the cable as you move it around, you have noticed that the battery still has significant charge left in it even after it has been shorted. This is because the battery has a maximum rate at which it can discharge current which is rather low. A battery is meant to hold a large charge for a long period, with small continous loads connected to it. This is also why it takes a battery a long time to charge.

Enter the capacitor. The capacitor by the nature of its design, usually holds much less charge than a battery, and can hold that charge for a much shorter period. (Yes there are exceptions.) The advantage of the capacitor is that it can discharge most or all of its charge at a fantastic rate (very small fraction of a second). Likewise, it can charge at a similarly quick rate.

Putting the capacitor and the rest of the alternator/battery circuit together, yields a much cleaner and powerful source for your amplifier. Heres how it works: The alternator outputs current to the battery to charge it, based on load, up to 105amps in your case. The battery outputs current to the majority of the electrical system inside the car. The capacitor places a load on the battery until the capacitor is fully charged. When the amplifier suddenly needs more current because of "the bass hitting" it is the capacitor that responds with a short burst of current. Then in the interim before the next time the amplifier needs a burst, the capacitor draws current from the battery to charge itself. This helps keep a fairly steady draw on the charging system (battery & alternator) from the amplifier, rather than a wild flucuation, thus your bass hits stronger because the amplifier gets the current it needs and your lights don't dim because the system voltage and available current stays at fairly normal levels.

Now, to whether or not you need a capacitor. With probably a max current drain of 15amps, I wouldn't think that a capacitor would be required. The first thing I would question, is where you are getting the power for the amplifier, is the amplifier properly grounded, and is the wire that you are using for the power wire a heavy enough gauge to supply 15amps. 8 AWG wire should be sufficient for your needs. It should have a direct connect to either the battery, or the positive terminal on the fuse block under the under, if that terminal can supply 15Amps, depends on the car. I would just give it a direct connection to the positive terminal of the battery with a ring connector. Next, check that you have the correct ground wire gauge and that you are connected to a chassis ground point, that isn't shared with any other high current devices. Again, 8 AWG wire should be sufficient. If you already have done all of the above and your lights are still dimming, then a recommend you purchase and install/have installed a 0.25Farad or 0.5Farad car audio capacitor. This is more effective than upgrading your alternator and battery in your case. The 105-amp alternator should be more than sufficient to supply the current you need for a 15-amp draw, it just can't supply it quick enough for the short bursts the amplifier needs. Same goes for the battery, if its the stock battery. If, once the capacitor is installed, you still experience this problem then either something else in your system (high-powered headunit) is doing it or there might be a problem with your charging system that you need to have looked at. Either way, the investment in a capacitor helps to protect the rest of your electrical componentry in the car from the amplifier's current draw surges, and can extend the life of your alternator.

Long winded, but hopefully informative. Let us know if you have more questions or problems.

I tend to agree with sr20de4evr about caps.(being that they are POS) Now the reason I suggested an alternator is because I assume you have a mass array of lights or something that is causing this problem and therefore pulling the most. The only problem with a cap IMO is that it will put more stress on your electrical system and possibly screw up your alt. Now here is my question, What lights or other electrical things do you have running on that car?

The cap will actually do quite the reverse haibane. The cap will even out the short high burst draws by the amplifier to a more steady and continuous draw from the electrical system. A continuous draw places less stress on the alternator than sudden bursts.

Think of it like this:
When you want to accelerate in your car is it better to slam the gas and pop the clutch in short bursts or to fully engage the clutch and deliver continuous power?
The continuous engagement of the clutch places less stress on the drivetrain, and will produce a much cleaner and faster acceleration time, than slamming the gas and popping the clutch in short bursts.

Also, what exactly do you mean by, its a POS? (and not an explanation of the acroynm) If the capacitor is of sufficient size and quality in construction, and wired into the circuit properly, it will not only place less stress on the electrical system, but it will also deliver more clean power to the amplifier on large current draws (when the bass "hits") giving you more dynamic and powerful amplification.

I'm too tired right now to dissect burly's arguments, but I'll be back later to do that. The fact is that in this case, and just about every single other case there is, a cap will be a waste of money. Yes it CAN help, but there are other things out there that cost 1/5 as much and absolutely WILL help as much as a cap will if not more so.

And again, I repeat, how is your gain set???

[QUOTE=burly]The alternator charges your battery as you drive down the road. The battery is the source for all your electrical equipment. This power is Not drawn directly from the alternator.

NO .... ONCE THE CAR IS STARTED, YOU CAN REMOVE THE BATTERY. THE ALTERNATOR PUTS OUT LIKE 13.8 - 14.4 VOLTS - THIS MEANS THE ALTERNATOR SUPPLIES ALL OF THE CAR'S ELECTRICAL POWER, ONCE THE CAR IS STARTED. IT HAS TO BE THIS WAY, SINCE THE BATTERY FLOATS AT LIKE 12.5 VOLTS. JUST THE LAWS OF PHYSICS, THE CURRENT MUST TRAVEL FROM THE HIGHER POINT OF VOLTAGE TO THE LOWER ONES. THE ONLY TIME THE BATTERY CONTRBUTES ANYTHING (WHEN THE CAR IS RUNNING) IS WHEN THE DRAW IS SO GREAT THAT IT DRAWS THE SYSTEM VOLTAGE BELOW THE BATTERY'S 12.5 VOLT FLOAT VOLTAGE.

What this means it that, while the alternator can deliver up to 105 Amps of continous output, the battery may not be able to burst you the power you need for such a short time when the bass hits. If you have ever messed with disconnecting the battery and see sparks come off the cable as you move it around, you have noticed that the battery still has significant charge left in it even after it has been shorted. This is because the battery has a maximum rate at which it can discharge current which is rather low. A battery is meant to hold a large charge for a long period, with small continous loads connected to it. This is also why it takes a battery a long time to charge.

Enter the capacitor. The capacitor by the nature of its design, usually holds much less charge than a battery, and can hold that charge for a much shorter period. (Yes there are exceptions.) The advantage of the capacitor is that it can discharge most or all of its charge at a fantastic rate (very small fraction of a second).

NOT REALLY, SINCE THE BATTERY TAKES OVER AT LIKE 12.5 VOLTS - THE CAP WILL NEVER DISCHARGE MOST OF IT'S ENERGY. IT IS CHARGED TO LIKE 14 VOLTS AND WILL NEVER GO BELOW SAY 12 VOLTS OR SO. SO IT CAN REALLY ONLY DELIVER ...... (14v - 12V)/14v ... OR MAYBE 1/7 OF IT'S FULL CAPACITY.

Likewise, it can charge at a similarly quick rate.

Putting the capacitor and the rest of the alternator/battery circuit together, yields a much cleaner and powerful source for your amplifier. Heres how it works: The alternator outputs current to the battery to charge it, based on load, up to 105amps in your case. The battery outputs current to the majority of the electrical system inside the car. The capacitor places a load on the battery until the capacitor is fully charged. When the amplifier suddenly needs more current because of "the bass hitting" it is the capacitor that responds with a short burst of current. Then in the interim before the next time the amplifier needs a burst, the capacitor draws current from the battery to charge itself. This helps keep a fairly steady draw on the charging system (battery & alternator) from the amplifier, rather than a wild flucuation, thus your bass hits stronger because the amplifier gets the current it needs and your lights don't dim because the system voltage and available current stays at fairly normal levels.

THE CAP CAN OFTEN HELP ... BUT YOU HAVE MISSED IT TOTALLY. THE REASON IS BECAUSE THE AMP DOES NOT PULL DC FROM THE BATTERY, IT PULLS PULSED DC. WHAT IS MOST IMPORTANT FROM THE POWER/ GND WIRES IS THEIR INDUCTANCE - THE CAP CAN ADD CAPACITIVE REACTANCE TO THE EQUATION. IT'S WHY THEY WORK IN SOME INSTALLS AND NOT TO WELL IN OTHERS. ALSO, SOME AMPS NEEP IT MORE THAN OTHERS.

The alternator part you are correct on. I actually second guessed myself on that afterward and then check my wiring diagram, and saw that most things have a path directly to the alternator when on, however, it doesn't really change things a whole lot. As long as his car is on, then he'll have ~14.4V and the reactance of the alternator.

However, saying that the capacitor only makes up the difference from 14-12V is not exactly true. First of all, the battery and the alternator act as independent Voltage sources, meaning they adjust current as quickly as possible to maintain a constant voltage. Neither source however, is ideal. Therefore it can only adjust its current to a finite level. If a load for more current than the source can supply is placed on the system, the source will no longer act as an independent source, and the system voltage will drop. This is like when the AC kicks on in the house and the lights dim. The sudden current draw lowers the voltage in the home's circuit, which means that instead of a light getting 110V, it gets 95 or 100, so it draws less current and doesn't light up as bright.

Capacitive reactance is the opposition to current flow and is defined by the equation:

Xc = 1/(2*pi*f*C) where f is frequency and C is capacitance.

From the equation, we see that capacitive reactance is decreased as the capacitance is increased. What this translates into is that when the system encounters a sudden change in load that tries to take the source out of independence, the capacitor reacts to "pull up the slack". So while yes, it may only have an operating range of Vmax to 12.5V, where Vmax is in this case around 14.4V, this translates into a very real difference in current. If the capacitor isnt there, the system voltage could drop down to 12V or less for an instant. This means there is a 2-2.4V drop in system voltage, which is about a 12-15% drop in voltage. Depending on the reactance of the amplifier, it could mean anywhere from a 12% (ideally) to 30% (worst-case) drop in Power. This is a very real drop. The capacitor works to maintain system voltage, helping to isolate the dynamic load of the amplifer, from the independent source (either the alternator or battery, depending on whether the vehicle is running).

What really makes a difference in the equation is whether or not the amplifier is reaching clipping. If it is clipping, then the MOSFETs (though some amplifiers use JFETs or BJTs, but same problem) enter saturation, and huge and in the scope of things Long duration current draws can be placed on the system. If an amplifier is operating in saturation it is much more likely to pull the independent source out of linearity and cause all sorts of problems.

As far are the DC pulse train, that created Inside the amplifier, in order to raise the voltage to a level necessary for amplification. The car's system (battery or alternator) delivers continous power. This is connected to the primary coil on a transformer that has high speed switching MOSFETs wired to it, to create a high speed switching DC power supply. This creates an AC signal on the secondary coil which is then rectified to produce a higher voltage DC signal. But the battery and alternator do not act as a switched power supply.

Also, I agree that some applications call for capacitor, some don't, and those that do call for different sizes. However, based on the facts hes given, his charging system should be able to deliver the power he needs, but it does not have the reactance to do so. His options are to lower the gain and produce less power (assuming hes not operating in saturation to begin with) or try a capacitor.

The alternator part you are correct on. I actually second guessed myself on that afterward and then check my wiring diagram, and saw that most things have a path directly to the alternator when on, however, it doesn't really change things a whole lot. As long as his car is on, then he'll have ~14.4V and the reactance of the alternator.

However, saying that the capacitor only makes up the difference from 14-12V is not exactly true. IT WILL ONLY DRAIN "DOWN HILL" .... WHEN THE VOLTAGE SAGS, ALL OF IT SAGS, THE VOLTAGE ACCROSS THE ALTERNATOR, BATTERY AND CAP. THE ONLY WAY TO COMPLETELY DRAIN A CAP IS TO SHORT IT OUT - OR PROVIDE A SMALL RESISTANCE TO GROUND.

First of all, the battery and the alternator act as independent Voltage sources, meaning they adjust current as quickly as possible to maintain a constant voltage. Neither source however, is ideal (NO SOURCE IS IDEAL)

. Therefore it can only adjust its current to a finite level IT'S NOT REALLY THE LEVEL, IT'S THE SPEED OR FREQUENCY.

If a load for more current than the source can supply is placed on the system, the source will no longer act as an independent source, and the system voltage will drop. This is like when the AC kicks on in the house and the lights dim. The sudden current draw lowers the voltage in the home's circuit, which means that instead of a light getting 110V, it gets 95 or 100, so it draws less current and doesn't light up as bright.

Capacitive reactance is the opposition to current flow and is defined by the equation:

Xc = 1/(2*pi*f*C) where f is frequency and C is capacitance.

From the equation, we see that capacitive reactance is decreased as the capacitance is increased. What this translates into is that when the system encounters a sudden change in load that tries to take the source out of independence, the capacitor reacts to "pull up the slack". So while yes, it may only have an operating range of Vmax to 12.5V, where Vmax is in this case around 14.4V, this translates into a very real difference in current. If the capacitor isnt there, the system voltage could drop down to 12V or less for an instant.

NOW YOU'RE ON TO SOMETHING HERE, THE PROBLEM IS THAT THE MOSFET "CHOPPERS" OPERATE AT A FREQUENCY OF AROUND 50K-60KHz - AND THE BATTERY/ ALTERNATOR COMBO CANNOT AND WAS NEVER DESIGHNED TO HANDLE THAT TYPE OF LOAD.

This means there is a 2-2.4V drop in system voltage, which is about a 12-15% drop in voltage. Depending on the reactance of the amplifier, it could mean anywhere from a 12% (ideally) to 30% (worst-case) drop in Power. This is a very real drop. The capacitor works to maintain system voltage, helping to isolate the dynamic load of the amplifer, from the independent source (either the alternator or battery, depending on whether the vehicle is running).

What really makes a difference in the equation is whether or not the amplifier is reaching clipping. If it is clipping, then the MOSFETs (though some amplifiers use JFETs or BJTs, but same problem) enter saturation, and huge and in the scope of things Long duration current draws can be placed on the system. If an amplifier is operating in saturation it is much more likely to pull the independent source out of linearity and cause all sorts of problems.

As far are the DC pulse train, that created Inside the amplifier, in order to raise the voltage to a level necessary for amplification. The car's system (battery or alternator) delivers continous power. This is connected to the primary coil on a transformer that has high speed switching MOSFETs wired to it, to create a high speed switching DC power supply. This creates an AC signal on the secondary coil which is then rectified to produce a higher voltage DC signal. But the battery and alternator do not act as a switched power supply.

THIS IS ALL GOOD, BUT THE FIRST THING IN THE 12VDC PATH (IN THE AMP CIRCUIT) ARE THE CHOPPERS - SO WHAT THE BATTERY/ALTERNATOR "SEES" AS A LOAD FORM THE AMP IS A PULSED DC LOAD OPERATING AT LIKE 60KHz.

Also, I agree that some applications call for capacitor, some don't, and those that do call for different sizes. However, based on the facts hes given, his charging system should be able to deliver the power he needs, but it does not have the reactance to do so. His options are to lower the gain and produce less power (assuming hes not operating in saturation to begin with) or try a capacitor.

I THINK EVERY SHOP THAT SELLS CAPS SHOULD HAVE A DEMO MODEL WIRED UP IN SUCH A WAY THAT IT WOULD BE EASY TO TEST HOOK UP IN A CAR. A QUICK 5 MINUTE TEST WOULD REVEAL IF IT WILL WORK OR NOT.