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Ω rise is way too high..
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Discussion Starter · #1 · (Edited)
No names, but I am through around 2 alternators for this for this upcoming build and am ready to order, but have a few finals thoughts. I have heard stories of direct swaps between 2 brands of alternators, and having voltage increases of upwards of 1.3v. Difference of 13.8v and 15.1 is big. One says computer controls voltage, the other is swapped in for the gain. Is it true that the alternator, built into it's design, controls the voltage? Or is it directed by an external computer? Keep names out of this, the only thing I am interested in hearing support for is facts.
 

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Im not completely understanding what your trying to say.. BUT one company has an adjustable module so you can set your charging voltage to whatever you want. Good if you want to run 14v or 16v batts. I have said brand of alternator coming. And this said brand sets voltage VIA an add on to the actual alternator
 

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Ja Marcus
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Depends on the battery type. AGM I wouldn't set it much higher then 14.4v
 

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14.4 and 18.3v


The few good companies offer external adjustable voltage modules. Most internals are set around 14 and a half.
 

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Ω rise is way too high..
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3,784 Posts
Discussion Starter · #5 ·
But if one alternator is charging low, is that the alternators fault, or the car's computer for having voltage low, I guess is my question. How much do those regulators run? PM me with who makes them, I only know of 1.
 

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Semi-Loud Trunk
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My car's computer doesn't control the alternators output, the voltage regulator does. There's more to it than that, but in a nutshell the answer I think you're looking for is the voltage regulator. Some are internal and some are external. Both can be made to be adjustable either way.

Edit.....

Mine is built in and is adjustable via a potentiometer. I set it cold for about 15.3 and it settles at about 14.7 hot.
 

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Ja Marcus
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Some vehicles are regulated low by the ECM to save fuel.
 

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Semi-Loud Trunk
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Found this on your car.....

The ECM directly controls the generator field control circuit input to the generator. It monitors the generator's generator field duty cycle signal circuit and sends the information to the BCM. The ECM will override the BCM control of the generator when one of the following conditions is met:

The engine cooling fans are on high speed.

There is a high fuel demand.

The calculated ambient air temperature is less that 0 C (32 F)

Body Control Module (BCM)
The body control module (BCM) is a class 2 device. It communicates with the engine control module (ECM) and the instrument panel cluster (IPC) for electrical power management (EPM) operation. The BCM determines the output of the generator and sends the information to the ECM for control of the generator field control circuit. It monitors the generator field duty cycle signal circuit information sent from the ECM for control of the generator. It monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state-of-charge (SOC). The BCM performs idle boost and load management operations.

Your voltage CAN be set higher.
 

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Ja Marcus
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Basically what I said. The ECM controls voltage to conserve gas. My Jeep never got above 13.8-14v even on the highway for 16 hours.
I wil say that sometimes the condition of the battery(ie state of charge) can also effect voltage. the more strain an alt takes to charge the lower the voltage can be.


Send me a PM. Im local so maybe I can help you out when you get things started. I won't screw you over like Chris did:thumbsup:
 

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Semi-Loud Trunk
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I basically told him the same thing, all he needs to do is get one that is adjustable and be done.

I really didn't understand truly what his first post was trying to say, because if you have a regulator go bad, it can sometimes climb into some extreme voltages. Yikes! No ECM can reel that in.
 

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Ja Marcus
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It depends they may not make one for that vehicle. Some will throw a code if the factory ECM doesn't since anything.
 

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Semi-Loud Trunk
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Don't have them on my phone, but the BCM voltages for those cars are lenient.
 

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Ω rise is way too high..
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Discussion Starter · #15 ·
What I am getting at is choosing a better alternator. I have heard one one pumps out lower amps at higher voltage and one low voltage and higher amps. Trying to find the most reliable power source. Audioarensal, PM me your number!
 

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Ja Marcus
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What I am getting at is choosing a better alternator. I have heard one one pumps out lower amps at higher voltage and one low voltage and higher amps. Trying to find the most reliable power source. Audioarensal, PM me your number!

Um thats how they all work. The higher the voltage the less current it takes. The lower the voltage is the higher the amperage will be depending on load.

Say you have an amp that will run on 12/16v. When running at 12v the alt will produce "X" amount of current. But when running at 16v the amp would use less current to do the same job. Therefore the alt would produce less current. Understand?
 

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Stupid Loud
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Um thats how they all work. The higher the voltage the less current it takes. The lower the voltage is the higher the amperage will be depending on load.

Say you have an amp that will run on 12/16v. When running at 12v the alt will produce "X" amount of current. But when running at 16v the amp would use less current to do the same job. Therefore the alt would produce less current. Understand?
This. It has nothing to do with the companies, this is simple electrical engineering concepts.
 

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Ω rise is way too high..
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Discussion Starter · #18 ·
Um thats how they all work. The higher the voltage the less current it takes. The lower the voltage is the higher the amperage will be depending on load.

Say you have an amp that will run on 12/16v. When running at 12v the alt will produce "X" amount of current. But when running at 16v the amp would use less current to do the same job. Therefore the alt would produce less current. Understand?
Exactly, but I'm thinking both 12v systems. I want to make sure I am getting the best I can, so I want to have solid, at least, 14.6. I will keep this updated.
 

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Ja Marcus
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Exactly, but I'm thinking both 12v systems. I want to make sure I am getting the best I can, so I want to have solid, at least, 14.6. I will keep this updated.
That is merely an example. Running 12v charging at 14v your gonna see minimal incresae in effecincy. There is no magic behind any of it. Two alts of the same output ie 270A are going to perform essentially the same way. There won't be any increase in current from one to the other given the same load.
 
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