How many AMPs does my alternator have to put out?

**soundman98** · 10-28-2009, 05:30 PM

capacitors are proven to be more of a parasitic load than a battery.

overall, they are at best a bandaid for a poorly setup sound system.

after removing their capacitors, spl competitors are able to get much higher numbers(ask them

)--if capacitors are really so great, it would be the other way around.

**justchat_1** · 10-28-2009, 06:03 PM

Originally Posted by soundman98

capacitors are proven to be more of a parasitic load than a battery.

overall, they are at best a bandaid for a poorly setup sound system.

after removing their capacitors, spl competitors are able to get much higher numbers(ask them

)--if capacitors are really so great, it would be the other way around.

Unless circuit design works for every area of the world except car audio systems I can't see how that could be true. In cases where the alternator is undersized for the current draw then yea without a cap you could overdraw the alternator and potentially make more power (but don't expect the alternator to last very long). For cases where the alternator and capacitor are properly sized it really doesn't make any sense. Yes a capacitor will have resistance and act as a parasitic load (since its series compared to the battery in parallel) but theres no reason a modern alternator shouldn't be able to provide enough power for even the biggest sound systems if done right. The capacitor is designed to stabilize the voltage swings that occur from the alternators voltage regulator trying to compensate for the big changes in current draw, it should only have a minimal effect on total available power.

That said-you know your stuff and I've certainly heard the claim other places so I can't dispute that. Just wouldn't get my vote as being factual.

**HiJackZX1** · 10-28-2009, 08:42 PM

Originally Posted by justchat_1

Yea the dual pulley setup is one i've seen quite a bit. The cool thing about it is if your not going to be blasting your system at 100%, grab a wrench and you can remove the extra belt and save some gas.

I decided to go with my pictured setup. Right now using a serpentine belt makes everything easy. Plus I am concerned with clearance issues.

You seem like you got everything planned out then. Just make sure you use fusible links on the power wires coming out of the amp. I would also recommend either a dual battery setup or at least running each line all the way to the battery instead of daisy chaining. It's probably overkill but I have seen a few people that will never use a single battery with dual alternators. The theory being that since each alternator is producing a rectified sine wave output, if the waves aren't in phase you can get spikes/sags due to interference. How true this is with modern alternators I couldn't tell you though.

I have already thought of this. The problem with the Durango is that Dodge made the PCM (ECU) control and manage the voltage of the alternator. If I add a second, it can in no way interact with the first one, as far as 12V power. Reason being is that the ECU will think that the alternator is putting out to much power and try to drop output so low that it will destroy the alternator and ECU. What ive decided to do is upgrade the stock alternator to the 160 version, with its own battery and thats it. The second alternator will run to its own dedicated battery. and run the car pc and amps strictly. The second alt has its own regulator so its not a big deal. So as far as daisy chaining, Dodge already shot that idea, lol. I think independent systems is much better because if I have power issues with the car, I know its alt 1. If I have power issues with the PC and anything added after the fact, I know its alt 2.

Oh and that reminds me->if you do any SPL contests or similar where you'll be squeezing every ounce of power out of the system, you'll want to up your idle speed. Alternators produce only a portion of their rated power at idle. I think the sweet spot is somewhere around 1100-1500rpm.

Yes, this I know. Thats why I bought the HO alt that I did. At idle it puts out 110 amps, then at 1200 rpm, its putting out the full 220 amps. Thats pretty impressive to me. Other people with dual setups, I see them having to rev the engine so high, that you hear more car then actual music. In defense though, any running dual alternators and up, usually has a insane amount of amps and speakers. Mine is mainly to power the 7 PC units with no hick ups. I think if I add up all the watts, the PC uses about the same power as the AMPS!!!!!!!!

Originally Posted by popi79

How about using a capacitor for the audio system...
this not only will make it sound better, it will stabilize the electrical system of the vehicle.

check: http://www.crutchfield.com/p_120PP10...apacitor&ssi=0

The audio setup isn't what I am trying to power, its the PC setup, and I heard a CAP can damage PC equipment.

Originally Posted by soundman98

capacitors are proven to be more of a parasitic load than a battery.

overall, they are at best a band aid for a poorly setup sound system.

after removing their capacitors, spl competitors are able to get much higher numbers(ask them

)--if capacitors are really so great, it would be the other way around.

I don't trust stuff like that anyways. Its basically a band aid for people that are too lazy to do the setup right, or in some cases, maybe they have no choice.

In my case, this has never been done, so I am really really nervous. I have only seen one other person do a dual alternator setup, but he had the 5.9 and had to delete his A/C compressor. Me, I am doing this on an engine that hates to messed with (Magnum 4.7 V8), due to its ECU, and no one ever bothers with. So its not like I can go and ask for help. I may be literally the only one to attempt this, and I am scared I will fail. I did order the 2 pulleys that will help to make the belt solid near the 2 alternator pulleys, but now I am so nervous about the company that will be creating the bracket system. I tend to be very short tempered when people do not understand my concepts, and the people I am dealing with, English is their second language, so there is alot of repeating going on, and thats just me asking for the address. Can you imagine once i start explaining this to them? I am wondering if maybe I should build a MDF model, like I did with the first bracket? Problem is, I hate fabricating so much.

**HiJackZX1** · 10-29-2009, 12:00 PM

In the Dakota-Durango forums, a member came up with the idea of a 2 belt system. He said to leave the original belt looping alone, and simply add a second by bolting a second pulley to the current alternator. This would be the easiest to do. Only thing is, to get rid of any other issues, the alternators would have to go right on top of each other. This means it is higher up, and the bulge I have to make in the hood would be higher. Thats not to big of a deal though. Here is a picture of the second layout:

Only hurdle is the fact that I do not think they make belts this short. So I may have to find a longer one, and add a tension pulley to the setup. Once again though, this is still easier then the first one belt idea. I would also have to modify the clutch fan. Right now if I add a pulley, it will knock in the fan. Shaving a few inches off the blade should fix that though.

**soundman98** · 10-29-2009, 01:05 PM

Originally Posted by justchat_1

Unless circuit design works for every area of the world except car audio systems I can't see how that could be true. In cases where the alternator is undersized for the current draw then yea without a cap you could overdraw the alternator and potentially make more power (but don't expect the alternator to last very long). For cases where the alternator and capacitor are properly sized it really doesn't make any sense. Yes a capacitor will have resistance and act as a parasitic load (since its series compared to the battery in parallel) but theres no reason a modern alternator shouldn't be able to provide enough power for even the biggest sound systems if done right. The capacitor is designed to stabilize the voltage swings that occur from the alternators voltage regulator trying to compensate for the big changes in current draw, it should only have a minimal effect on total available power.

That said-you know your stuff and I've certainly heard the claim other places so I can't dispute that. Just wouldn't get my vote as being factual.

i used to have a very nice link to give out for this, but the company has since started selling sound deadener, and has removed/buried the research he did for capacitors on audio systems:
http://www.sounddeadenershowdown.com

when the review had been up, he proved that a capacitor is bad (only from a power standpoint, so it might still improve the audio quality, but i have not seen any data from anyone who has proven it on paper- if anyone can prove it on paper, i will change my opinion) by using at least a volt meter(i thought he used a occilloscope somewhere too), and taking readings from the battery, amp, capacitor terminals, and at high volume and low volume, with and without a capacitor-- the overall readings were 1-3 volts lower with a capacitor installed than without one-- and in a 12 volt environment, that is a huge loss in overall voltage, and output, other than amps like jl's that have switching power rails to compensate, a amp with a 60 amp fuse:

at 12 volts: rms output would be about 470 watts
at 14 volts: rms output would be about 550 watts

and that is just a 2 volt fluctuation-- if the capacitor draws it down to 10 volts: 390rms...
and that is not even factoring in the extra heat that a class a/b amp is putting off at lower voltages as it works harder, which will reduce the wattage even more...

there is also the issues with the charge rate of capacitors-- in a perfect world, a car audio capacitor would discharge, and then immidiatly recharge, ready for the next 'bump', but in the real world, capacitors take a while to charge up again, and that is really what makes them bad for car audio-- they are constantly trying to charge up again as the amp is trying to pull current from them for the next bump, lowering the voltage even more-- because no-one makes their system go 'BOOM' once, and then turns it off...

most capacitors in a normal elctrical environment are used either as a reserve power supply(like the dc-dc adapters on this site- to get the computer to survive crank), or to reduce large, temporary electrical loads (like the capacitor on your homes air conditioner- to reduce the 'kick' when it turns on)--look at car audio like stopping and starting that motor with a cap on it, a couple of times a second-- there is just no time for the cap to recharge enough to fully help.

btw: i found a nice post about determining rms amp values for anyone interested: http://audioforum.termpro.com/cgi-bi...6;t=000505;p=0

**HiJackZX1** · 10-30-2009, 02:44 PM

Yesterday I went to AutoZone. They had short belts, but not short enough. I had to revise my setup, once again. In order to accommodate the new setup I have to delete the clutch fan. Its a fan that is connected to the water pump. I have never liked the d@mn thing anyways, so I do not mind. It does mean I have to change out the thermostat from 195, to 180, not a big deal. I will also have to eventually change out the electric A/C fan for a heavy duty electrical fan. A lot of Durango users recommend switching to a Dodge Viper electric fan system, which I am not sure about because alot have to be swapped out to get it in there.

The new belt setup will now look like this:

The alternator is now to the middle of the engine, and on the area that was over the water pump, goes the pulley to make the belt tight (tensioner). I ordered an alternator pulley to weld onto the 1 st alternator pulley and the tensioner. They were some what expensive to me. The alt pulley was $24.00 and the tensioner was $20.00. The belt ran me $15.00. Only thing I have to figure out is the pulley on alt one. I have to make it in such a way, that if I replace alt 1, I can get the future dual pulley off to put on the replacement unit. I think they use a special tool to do that, but I have to make sure this new setup is friendly to that tool. Other then that, I think this may work, and once its out the way, I can move forward. I have stopped all work on the Car PC, just so I can finish the engine mods.

**HiJackZX1** · 11-01-2009, 01:56 PM

I had to take the clutch fan out in order for my new belt setup to fit. It was really stuck in there. Basically the clutch fan is connected to the water pump pulley which turns the same way that I have to turn the nut to get it off. I tried to do this by using screw drivers in the holes to jam the pulley. This of course failed badly. I then decided to go to home depot, by the rod that Turbo287, a user from dakota-durango forums, used. Drilled holes, added bolts and that was that. The clutch bolt was really jammed on there. I had use all of my body weight to turn it. Then after that I had to really use strength to get it off. I am glad I found this thread because the tool was very helpful.

Thanx so much for the useful info.

I live in Miami FL, so I thought it would be in my best intrestest to change the thermostat to a 180. I did so and the car actually runs cooler then when I had the clutch fan and 195 thermostat in. Before the temp was alittle less then half from the middle. Now though it sits closer to the white line near the cold side. I will change the fan in future, but for now it doesnt seem to be needed.

**JuniorGeezer** · 11-09-2009, 07:17 PM

If your maximum power is 2300 Watt and mostly for music, the average will likely be less than half, well within the ability of your current alternator.

It will also be insanely loud and your passengers will sue you for inflicting them with tinnitus.

Wouldn't it be wiser to beef up the alternator when everything else is installed and running at whatever volume you think is loud enough?

I get the impression it's an entertainment system, not for SPL competition.

**HiJackZX1** · 11-09-2009, 07:28 PM

Originally Posted by JuniorGeezer

If your maximum power is 2300 Watt and mostly for music, the average will likely be less than half, well within the ability of your current alternator.

It will also be insanely loud and your passengers will sue you for inflicting them with tinnitus.

Wouldn't it be wiser to beef up the alternator when everything else is installed and running at whatever volume you think is loud enough?

I get the impression it's an entertainment system, not for SPL competition.

You are exactly right, it is 100% for entertainment. The problem is I am running alot of computers. I just want a nice crisp sound, thats loud, but not so loud that its heard 2 blocks away. Thats why I bought speakers capable of only 100RMS, which is still pretty loud. My issues is all the screens, and the 3 PSUs I have to power. Not to mention other devices. I basically want to take any device not made for the car, and put it on its own battery and alternator. That way alternator one can focus on lighting, alarm, and other stuff that helps to improve the car.

I think 220 amps should be enough to run all the amps and PC

**justchat_1** · 11-09-2009, 10:49 PM

We've already gone over how unnecessary this is I thought....your average high end carpc is using 5amps, your average screen uses only about an amp. Not to mention most stock 25w(Peak) audio systems are loud enough for normal listening - you probably will never exceed 30w rms with your system. But no-ones gonna talk you out of the project...you wanted to move forward ->we'll help you