How many watts can you run?

[xtremerevolution]

I've spent the last 8 months doing a variety of audio related research and design. I've researched and modified a number of Class D home amplifiers, I've designed complex crossover networks for hi-fi home theater use, and I've designed proper sub and speaker boxes using tools many of you don't even know exist, modeling frequency response, cabin gain, cone excursion, impedance, and a variety of other factors. WinISD basic edition is a child's toy compared to the stuff I've been using.

So here's a writeup that will help some of you design a car audio system properly. This writeup will be focused on power and how much power your car can handle.

Alternators

Most GM cars come with a small variety of 105 amp rated alternators, most commonly the CS130D I haven't been able to find the ratio of the crank pulley to the alternator pulley, but lets assume that in a typical scenario, we're getting 90amps while cruising.

Wiring

Most GMs come with factory 4 gauge copper wiring. This is all well and good for the stock system, but problems can arise when you put greater load on them. More on that later.

Crutchfield actually has a pretty good way to determine if your electric system is capable.

In order to calculate your needed wattage, first determine the RMS power rating of the amplifier you are using. Lets use the JL 1000.1 because its very popular and well rated. This amplifier is rated for 1000W RMS.

Next, double that rating. Why? Because amplifiers (even automotive Class D) are typically 50% efficient. This means that in order to provide 1W of power, it needs to draw 2W of power from the electrical signal. The extra 1W of power is dissipated as heat, which is why amps get hot when run at high volumes. In our case, the JL 1000.1 is at best 50% efficient, so lets use that. According to calculations, we need 2000W total. Now, since wiring is rated by amperage, we divide 2000W by 13.8V to get the amperage. In this scenario, we are left with 145 amps if we are to use to its maximum potential.

The following chart provided by crutchfield.com outlines the size **copper** wire you will need:

.

I say copper because copper clad aluminum does not have the same capacity, and you will typically need to increase wire diameter by 1-2 sizes to compensate.

According to that chart, we would need a minimum of 4 gauge in our engine bay (brand new, not corroded), and 2 gauge running to the trunk.

Now back to the alternator problem. As we remember from earlier, we need 145 amps. However, our alternator only produces ~90 amps at idle at 13.8V. Lets say in a magical scenario we do produce 100 amps at 13.8V. This would allow us to output ~700W from our 1000W amp.

What happens when we try to produce more power than our electrical system is capable of? Our voltage drops, our lights dim, and heat starts to rise in our alternator and our wiring.

So what is a factory system capable of producing? Safely, around 500W. You have to consider that your sound system is not the only component in your car that draws electricity.

[white4d96]

A better bet to determine draw of an amp? Check the fuses. It will never pull more current than what the fuses are rated for.

As for the CS130D's, most I've seen benched did like 30 idle and at most 70 max. They're really inefficient with heat.

[xtremerevolution]

A better bet to determine draw of an amp? Check the fuses. It will never pull more current than what the fuses are rated for.

As for the CS130D's, most I've seen benched did like 30 idle and at most 70 max. They're really inefficient with heat.

I read this recently over on diyma.com:

Fuses in amps are really only for short circuit (fire) prevention the amps have electronic protection built in for, over temp, low impedance, ect. Many high output amps including some from LP require slow-blow fuses. A amp playing music will rarely reach top rated output for any length of time usually just momentary peaks. A slow blow-fuse is designed to handle peaks in current handling up to 10x there rating for several seconds. Most amps will shut-down on over temp before they come close to clearing a fuse after long play with full power peaks.

[white4d96]

The amps I have used did not use slow-blows. I found that out when my stupid self wired one backwards

I do know that ANL fuses are known to be underrated. My 325-amp fuses apparently will not blow until you see almost 400 amps.

[skitchin]

Great info man, this is the info you need to do it RIGHT people. Getting full power to your amp is the most important piece to the puzzle, or your JL will sound like walmart junk.

Any info on auxilliary batteries?

[xtremerevolution]

Great info man, this is the info you need to do it RIGHT people. Getting full power to your amp is the most important piece to the puzzle, or your JL will sound like walmart junk.

Any info on auxilliary batteries?

Great if your amplifier is drawing more power than your alternator can produce. 10x better than a capacitor for storing energy.

I did look up the fuses on a JL 1000.1, and it has 3 35a fuses for a total of 105A. As I mentioned before, you have other things drawing power from your car (plus your alternator won't be running at 105A continuously at idle or cruise RPM), and those fuses are there more as a short circuit protection, not to limit how much power it draws.

I still maintain that 600W is about the most you can safely pull from your system before upgrades are necessary.

[white4d96]

I also forgot to mention, if you have voltage issues, GROUNDS GROUNDS GROUNDS!

If you have bad grounds your stock stereo will cause voltage drop, as will your turn signals, brake lights, wipers, everything. Go through and beef up your grounds.

I gotta do this today as I have voltage drop out of the blue Either that or I need to charge my huge battery. I think the front batt may be pulling it down.

[Garrett Powered]

I have failed to power the jl1000/1 many many times. you really need to throw every trick in the book at it or it will not have enough juice. I had a RV deep cycle AGM battery and a 1 farad cap for awhile and it really took the load off my alt. which I have a cs130d by the way. no its not stock on my car, and yes it is difficult to custom fit one, but I had to. I have a real small pulley and it cranks out 165 amps and idle charges while staying cool. You cant just go buy one for my 90 tgp that uses a cs130, I looked. maybe not hard enough though so if they have em, someone post a link and we can go from there...

I am hoping to save weight on my next build using a 1000/1 though and just plan on using a stock battery up front along with a 3.5 farad cap in the trunk. I will not bump the system with the car off though for more than a minute. driving around will be sustainable power with no significant dimming of the lights. I have not proven it yet in real life, but I intend to try powering it this way with a single battery, a 140 amp isolator for a two battery system equipped with an "e" post for use with "cs" series delco whatever alts, ANL fuse on a 3.5 farad cap used as a battery. I used 1/0 hyperflex to the cap.

if its not enough reserve then I can mount the lifeline rv battery back in there or get a racing battery. the cap I am confident will be enough for moderate listening levels and short bursts. I never used to have ANL fuse technology back in the day either so that makes a huge difference in my opinion. you had these crappy glass fuses with gold caps, yuck.

[xtremerevolution]

Not sure what the hyperflex is, but as long as its copper and not cca, its fine.

As for capacitors, they're worthless. Extra batteries are what you need, which you mentioned. With good electrical wiring, a good alternator, and a good battery or pair, you should have no electrical problems.

As for the cs130d, I'd like to hear how you got more output on it. Those have a cutoff as far as how much current they produce, and after a certain rpm, it makes no difference unless you modified the internals. A smaller pulley will only help your idle and cruise output.

Sent from my HTC Awesome using Tapatalk

[Garrett Powered]

caps cushion the blow to the alt, you can not do quick bursts without one or at very least a racing battery to cushion the alt. what are you saying caps are worthless for?

I have custom internals built into it and custom case for it. my first CS130D cost me $350, and my second one set me back over $400. they were both custom assembled and modified extensively with new parts from a catalog. first one dynoed at 165 amps redline. second one is same thing.

[white4d96]

Caps are just an extra draw on the alt. Only time they're useful is if you have no voltage drop and you want to ensure consistent voltage to the amp (reducing spikes and dips on transients.) I only hear of widespread use of them in SQ setups, and even then it's not some $150 3.5-farad whatever, it's like a $400 big ol' thingamajig.

[AWeb80]

I hate electricity....this thread hurts my head.

[xtremerevolution]

caps cushion the blow to the alt, you can not do quick bursts without one or at very least a racing battery to cushion the alt. what are you saying caps are worthless for?

I have custom internals built into it and custom case for it. my first CS130D cost me $350, and my second one set me back over $400. they were both custom assembled and modified extensively with new parts from a catalog. first one dynoed at 165 amps redline. second one is same thing.

I'd take the time to explain this for the 100th time to people, but instead I'll copy and paste what someone else said on diyma very accurately.

you need to fuse your power wire within 18" of the battery and every time you change gauges, like using a distro. as far as caps, someone posted this on here a long time ago and it's the easiest explanation i have ever seen.

After studying a little history on large 1 Farad capacitors in car audio, you'd be amazed that they even sell at all. How useful are they? What do they really do? Will a Cap 'improve' my sound quality? Will it Prevent my lights from dimming? Will it audibly affect my audio system in any way?

Before you get the truth to any of the above questions, chances are, you've probably spent $100 or more on one of these devices. However, let's study a little history regarding this issue.

A long time ago, in a land far away, 2 elves...Ok, Richard Clark & Wayne Harris (Carsound magazine and the inventor of DB Drag, respectively) separately came up with a solution to preventing their lights from dimming.

WHO WERE THESE GUYZ?

As you may know, Richard Clark is one of the founders of autosound2000 Tech Briefs, Carsound magazine, and a published author of the industry of mobile electronics. In SQ competitions, he posted a record of 1234 1st place finishes, and only ended up NOT 1st in his first event. I've heard that he had minor system problems, but judging by his record, he must have corrected it. (evidently, he needed a Capacitor )

Wayne Harris was previously a leader at Rockford Fosgate in their development. Later, in his free time, he created the organization we call DB DRAG. Wayne was the first SQ World Champion from the organization we know as IASCA (International AutoSound Challenge Association).

Both of these gurus are both legends, and considered the leading experts in the field. During their competition days, both guyz came up with a way to assist in the prevention of voltage drops. In SQ competitions, the look of your system is actually more important than the sound, and having your lights NOT dim under high playing levels is a competitive advantage.

As you may know, amplifiers are made up a bank of little capacitors, resistors, etc. What has been common engineering knowledge is that capacitors store energy, and more or bigger ones assist in balancing the power supply.

Wayne came up with the idea of putting several dozen 'little' (approx 100uF) capacitors on a circuit board to 'extend' the power supplies storage. At about the same time, or shortly afterward, Richard came up with the idea of one huge mondo capacitor (I believe it was 800,000uF or 0.8F) to do the job.

Eventually, Richard won. The large cylindrical tubes won over the complicated 48 caps strapped to a circuit board. However, what did this really accomplish? Let's start here:

WHAT IS A CAPACITOR?

Basically, capacitors are an energy storage device. Large, 1 Farad or more
capacitors store energy (electrons) between their plates. Capacitors differ
from batteries because batteries store energy in the form of chemical
energy--and rely on acid and lead plates, as the place of storage. For a more detailed
description of a capacitor, go here:

http://www.eatel.net/~amptech/elecdisc/caraudio.htm

Then on the right hand side, scroll down to CAPACITOR. Keep in mind the use
of capacitors in an audio system.

WHY DO PEOPLE BUY CAPACITORS?

The number 1 reason would have to be because their lights dim when their
system is playing HARD. In car audio, we are told that a capacitor is
designed to prevent the voltage drop associated with your lights dimming.
The number2 reason is that it is rumored to 'improve' sound quality or
'stiffen' the power supply/source.

WHY DO MY LIGHTS DIM?

Headlights brightness is in direct proportion to the source voltage. For
instance, if your car is running, system voltage is ~12.5 -14.4 VOLTS. Your
lights will be much brighter than when your car is turned off--where battery
voltage is ~12V. Most car alternators put out between 75 to 120 amps of
current. When this current draw threshold of the charging system is
exceeded, system voltage will drop as power demands are now shared by the
alternator and the storage devices (battery & cap). We are using battery
reserves beyond this point until the demand lessens

When playing your system really hard. Your lights dim because your
alternator can't keep up it's charging voltage (around 13.5V) and therefore,
demand exceeds output. When this happens, your electronic devices are
dipping into the power storage of the battery. Since the battery stores
power at ~ 12-12.5V, there is a 1.3 to 1.8V drop in voltage available. This
in turn is why your lights dim down.

HOW MUCH POWER DOES A CAPACITOR STORE?

1 Farad = 100 joules or 100W/second
850cca battery = ~2,200,000 farads

For storage purposes, you'd need ~2,200 1 Farad capacitors to equal the energy of your battery.

Due to its impedence (ESR & ESL), a cap's energy is only 50% available. What's worse, is that in order for a 1 Farad cap to discharge, first the alternator output must have maxed out, and the voltage must have dropped around 1.5 volts. But I thought a cap was supposed to prevent that (voltage drop)!!!!!????? Yep, you got the point.


IF A BATTERY = 2,200 CAPS, THEN WHY BUY A (PUNY) CAP?

My question exactly. Marketing is the reason why people buy caps. In many cases, upgrading wiring will help your system get the maximum transfer of current. Once that has been reached, adding a capacitor may have a minor effect on your system. 50W over the course of a second is not a lot of power considering an amplifier may draw 2000W to put out 1400 watts. Let's look at the situation from a resources standpoint.

Alternator 80 amps
Car accessories (minus stereo) 40 amps
A large Car Audio system (DRAWS ) ~200 amps AT FULL OUTPUT

In this case, you have 240 amps of draw, but only 80 amps of current from the alternator. In your case, you need 160 amps x 12 volts or or let's say 1920 watts of energy. Since a cap stores 50W, how much of a difference do you think it's going to make? A cap is basically a peashooter. W+e need a Howitzer cannon here, to do the job well.

Also, Once a cap is discharged, where does it get it's power from? The alternator, which is already overloaded. Once a cap is discharged, it's worthless. Like SWEZ says, ・.The cap already shot its wad, an does limp til recharged・ I知 not so certain I will allow him to babysit my kids, but you get the drift. (I never said it quiet like that... and oh...I'm great with kids!)

SO, WHAT IS A CAPACITOR GOOD FOR?

1. Audio Jewelry- impress chicks with large cylindrical shiny thingy
2. Extra weight in winter time
3. A very POOR... BUT expensive distribution block
4. A projectile in the event of a crash
5. Rolling pin--for cooking purposes
6. A neat thing to tell your friend, "..Hey man, lick the top of this..


Please do not try # 6. New hairstyles are always refreshing, but if you are wearing railroad tracks across your teeth, you might have one big filling after it痴 over.

HOW CAN CAPACITORS IMPROVE SOUND QUALITY?

They can't. Sound quality is not dependant upon the presence of large bulky 1 Farad capacitors. How many 1 Farad Capacitors do you think the Boston Pops, Aerosmith, or Snoop dog use in the recording studio?

IN A NUTSHELL.......

When Richard, our fearless inventor, became World renown for winning every competition under the sun, people began copying what he did. Soon, every 'serious' competitor had a 'stiffening' capacitor--not to be confused with the 'loosening' capacitor.

WHY?

In the late 80s, people began sticking out their tongue when dunking the basketball because Michael Jordan did. Did sticking out your tongue improve your dunking ability? Same here with adding a capacitor to your electrical system.


In a final note, Richard relayed a quote regarding battcaps as, "..The audio industry is the only place i know of where you can publish specs that show your product is useless and still be able to sell them------and whats worse is that technically ignorant people will argue against the math!!!!!!!..............RC.." when referring to the product. This also relates to most digital readout capacitors, and I wish my Archie Bunker skills could have said it better myself.

[Garrett Powered]

wait, I do not need an explanation from that guy to know my cart benefits form them. so are you saying they are good or bad, I cant understand you?

[Garrett Powered]

Caps are just an extra draw on the alt. Only time they're useful is if you have no voltage drop and you want to ensure consistent voltage to the amp (reducing spikes and dips on transients.) I only hear of widespread use of them in SQ setups, and even then it's not some $150 3.5-farad whatever, it's like a $400 big ol' thingamajig.

I have a Boss 3.5 farad cap with digi display. it ensures there are no voltage drops. the only time that is useful is all the time.

being they are for SQ cars I will not dispute. $400? that must be a good one.