# Wiring dual alt question



## Eastman474 (Jan 8, 2010)

I am needing some help. I mounted my DC Power Dual Alernators and I have one powered and working properly but I am needing to know how to wire the second alternator.
I have a relay that came with it that has the following wires.

Red out of relay clipped
White with ring terminal
Yellow with a plug for the Second Alternator
Red with a ring terminal.








As far as power and ground to batteries thats all easy.


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## [email protected] (Nov 7, 2010)

I can tell you this much:
The red wire with the loop will go to the bolt on the alternator that outputs the 12v.
The yellow plug plugs into the alternator
The white wire gets grounded
The red wire with no connector will control the alternator charging when it sees 12v.

Is one alternator dedicated and isolated just for the stereo?


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## Eastman474 (Jan 8, 2010)

JOey Knapp said:


> I can tell you this much:
> The red wire with the loop will go to the bolt on the alternator that outputs the 12v.
> The yellow plug plugs into the alternator
> The white wire gets grounded
> ...


no its not just for the stereo theyre running together. and thats what i thought however i dont thing that small red wire with the ring terminal can handle 230 amps on the outut stud?


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## [email protected] (Nov 7, 2010)

Ok. In basic terms. The alternator doesn't "push" its amperage, rather, it supplies it when electronics draw it from the alternator. The "draw' in this instance will be the power to energize the alternator and make it charge. That will be a minimal amount of power.

If your thoughts were correct, how could you put a 230 amp alternator in place of a stock one and not have to replace EVERY wire in the vehicle with a 1/0 gauge? 

This idea, along with the concept of the relay are two very important things to learn...


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## Eastman474 (Jan 8, 2010)

Okay I see what you are saying now, and that's true. So even when the battery is trying to pull said 200 amps off the output stud, that small wire to the relay won't be damaged?


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## [email protected] (Nov 7, 2010)

And, to take it a little step further even.. The battery isn't the one pulling 200 amps. The amplifiers are what is pulling the 200 amps. The battery is there to start the vehicle and filter the power. Think in terms of electronics pulling power from the alternator, not the alternator pushing out power...


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## Eastman474 (Jan 8, 2010)

Yes I do know that the amplifiers draw the power I just said batteries because the amps are wired to them :b .. And I do understand what you're saying I was just strugging to understand that even when the alt is supplying 200 amps to the batteries and that small wire is on the output stud, how it couldn't be dammaged but I get what you're saying. Thanks for all the help,


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## j sexton (Sep 19, 2009)

i didnt see anything in that pic that looked like it could handle output either ,looked like alt field control kit to me .curious if anybody chimes in to save this guy.


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## Eastman474 (Jan 8, 2010)

JOey Knapp said:


> Ok. In basic terms. The alternator doesn't "push" its amperage, rather, it supplies it when electronics draw it from the alternator. The "draw' in this instance will be the power to energize the alternator and make it charge. That will be a minimal amount of power.
> 
> If your thoughts were correct, how could you put a 230 amp alternator in place of a stock one and not have to replace EVERY wire in the vehicle with a 1/0 gauge?
> 
> This idea, along with the concept of the relay are two very important things to learn...


and also off the alt it goes to battery and then to the fuse box where every wire in the car is fused to the amperage needed right?


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## Eastman474 (Jan 8, 2010)

Finally got ahold of dc power today, I was right that it doesn't go to the alt output stud, red with ring terminal goes to battery, white is obviously ground, and the clipped red goes to accesory


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## chapdawg1971 (Mar 8, 2010)

If it's like a Mechman alt, they supply you with 1/0 lugs and yes, you will want to have 1/0 power cable run from that stud to your batteries, which i'm sure you were tracking that.

When those amps pull the power from the batteries, what do you think supplies the batteries with their juice? ......and to be honest, what Joe was saying had/has me worried.


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## Eastman474 (Jan 8, 2010)

chapdawg1971 said:


> If it's like a Mechman alt, they supply you with 1/0 lugs and yes, you will want to have 1/0 power cable run from that stud to your batteries, which i'm sure you were tracking that.
> 
> When those amps pull the power from the batteries, what do you think supplies the batteries with their juice? ......and to be honest, what Joe was saying had/has me worried.


yes i knew 1/0 to the batteries from alt , just was confused on that voltage sensing relay. But now its making sense, that output stud would have fried that small wire. But at least he was trying to help me out, thanks guys


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## chapdawg1971 (Mar 8, 2010)

Yeah, found it odd that DC didn't include instructions with that.


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## TREETOP (Feb 11, 2009)

Eastman474 said:


> Finally got ahold of dc power today, I was right that it doesn't go to the alt output stud, red with ring terminal goes to battery, white is obviously ground, and the clipped red goes to accesory


The alternator's output stud also goes to the battery. It doesn't make any difference at all if you connect that ring terminal to the alt's output post, the battery terminal, or anything in between- it simply needs to get a constant +12V so the relay has something to throw to its output when accessory is on. Judging by the length of it, it's most likely designed to be hooked up to the alternator's post rather than the battery directly- electrically it makes no difference but why stretch another wire across the engine bay when you have +12V right at the alt?



Eastman474 said:


> yes i knew 1/0 to the batteries from alt , just was confused on that voltage sensing relay. But now its making sense, *that output stud would have fried that small wire.* But at least he was trying to help me out, thanks guys


Incorrect. The battery isn't charging through that wire, the amps aren't drawing power through that wire, and the relay and second alt turnon aren't going to draw more than 10 amps of current. The relay harness you're showing is _only a turnon for the second alternator_. Technically you don't even need that harness, you can just jump the brown wire from your first alt to the same pin on the second one, but DC Power must have included it for a reason so I guess you might as well use it.



JOey Knapp said:


> I can tell you this much:
> The red wire with the loop will go to the bolt on the alternator that outputs the 12v.
> The yellow plug plugs into the alternator
> The white wire gets grounded
> The red wire with no connector will control the alternator charging when it sees 12v.


This is correct.


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## [email protected] (Nov 7, 2010)

chapdawg1971 said:


> If it's like a Mechman alt, they supply you with 1/0 lugs and yes, you will want to have 1/0 power cable run from that stud to your batteries, which i'm sure you were tracking that.
> 
> When those amps pull the power from the batteries, what do you think supplies the batteries with their juice? ......and to be honest, what Joe was saying had/has me worried.


What did I say that worried you. If anything I said worried you, I would want to guess that maybe you have a misunderstanding of fundamental 12v electronics....


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## [email protected] (Nov 7, 2010)

And.. it makes no sense in the makeup of the harness that they want the red ring terminal wire to go to the battery. It is right next to the plug for the alt. If you hook it to the terminal on the alt, guess what, you have just hooked it to a battery. THAT is where you should put it...


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## chapdawg1971 (Mar 8, 2010)

They assumed you would hook it up at the alternator since it's there with the plug is at and that's why the ring terminal is on it. Not that complex, but he's got it figured out. All of the ones I've seen are just like the one he has.


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## Eastman474 (Jan 8, 2010)

So I think I'm understanding this concept better now, but let me make sure. So say 1/0 gauge wire on the output pose ran to battery is drawing 100 amps, if that small relay wire is on the output post when that 100 amps is being supplied it still won't be damaged because the relay isn't drawing the power, just the 1/0 is. Correct?


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## chapdawg1971 (Mar 8, 2010)

Yes, you will be fine. Look at most other factory alternators, they have small wires hooked into the positive post that connects to the battery as well, same down at the starter too.


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