Alternator Mod Revisited

[Beav]

I've always disliked that title.

Anyway, I used to believe that a bigger 'pipe' couldn't hurt, even though I knew that you can start a car with a 14ga. wire. (It gets DAMN hot, though!)
After reading this well thought-out article I can see the error of my (and more than a few others) well meant intentions:

http://www.madelectrical.com/electri...hreewire.shtml

It's only three pages long. You may ask, "Why am I reading about the difference between 1 & 3 wire installations?" Just stick with it, by the time you finish page 3 you'll understand.

[STORMINORMAN]

I believe, I believe!

But I don't understand, yet!

[Trevor]

Greetings Beav,

Unfortunately this litany is in fact published as a sort of sales gimmick, and few will understand what is in fact the real issue and it certainly is confusing. Be very sure that a bigger pipe/wire will carry more current than a narrow/thinner one, as will several in parallel.

All modern alternators utilise a separate wire to sense voltage direct from the battery, so that the exact fidget is apparent, rather than that which may vary as result of current delivered by the alternator, via the main charging wire/circuit.

This outfit has simply latched onto the fact that an extra wire exists, as a means of promoting their image. They carry on with the suggestion that sensing could be derived from a point in the circuit remote from the battery, and so result in incorrect readings. Such an arrangement would in itself be an error/fault and most certainly would not be part of an OEM system. The SVX is most certainly not affected and correctly has a sensing wire connected at a point very close to the battery and therefore not subject to error.

I have covered what is involved several times when referring to the awful “alternator upgrade,” but not regarding the shortcomings of the mod. in this respect, as the separate sensing circuit is not affected. Those interested in the subject should visit my locker. An extract from the data reads as follows:-


There can be an advantage in having a small resistance between the alternator and the battery, as this can be a form of over current protection for the alternator. What is more any small voltage drop will not effect the as designed alternator output voltage, as the electronic regulator senses battery voltage directly via a separate pilot wire. It could be that Subaru designers had this in mind, as it is hard to accept that they were trying to save on a few strands of copper or were ignorant in respect of basic Ohm's law.


The article is certainly interesting. My comments are in no way adverse in respect of its presentation, and are put forward simply by way of an explanation of what is involved.

[michael]

That article went in one eye and out the other My guess is a 1 wire is a connection from the alt. to the battery. A 3 wire has multiple connections such as at the batt., starter, & main harness? If this is not the case please enlighten me.

[michael]

That heps Trevor. You snuck in before I could post. So you're saying the stock sensor wire of an electrical system is to far downstream of the alt and this kit is supposed to be a fix?

[Trevor]

Originally Posted by michael

That article went in one eye and out the other My guess is a 1 wire is a connection from the alt. to the battery. A 3 wire has multiple connections such as at the batt., starter, & main harness? If this is not the case please enlighten me.

Sorry, I do nor have the time or energy to play guessing games. Go to my locker for answers. The three wire stuff in the article is pure sales bovine manure.

[Trevor]

Originally Posted by michael

That heps Trevor. You snuck in before I could post. So you're saying the stock sensor wire of an electrical system is to far downstream of the alt and this kit is supposed to be a fix?

I am saying nothing of the sort. What "kit" are you referring to ?

[Beav]

I'm not in total agreement re: the voltage drop being as great as the author stated, at least not in respect to a properly functioning circuit, but I can understand his theory.

I believe the placement of the alternator (or generator, as many OEs now prefer to call it) output wire was what the author was trying to explain. His insight is that having the output wire tied directly to the battery while the sensing wire a significant distance downstream is a problem. He is calling the portion of the circuit between the battery and the load/sensing circuit a significant voltage drop. His theory is that if the sensing wire and output wire join the load at this downstream point, a higher voltage will be available to the loads while it tends to be slightly 'buffered' (reduced by the voltage drop of the circuit between the splice point and the battery) by the time it reaches the battery. For years I have wondered why OEs had designed the output circuit as lengthy as he described. I have never witnessed an output wire routed directly to a battery, it always connects to the load/supply splice point. As the author also states, this may explain why a number of owners have had short battery life issues, even though they had "...installed the alternator mod some time ago."

[Trevor]

Hi again Beav,

Although in an OEM system the connection for the sensing circuit will not be right at the battery for very good reason, there will be next to zero resistance between the connection and the battery.

It would be negligent not to connect at a point subsequent to any protective device, e.g. fuse or fusible link. Manufactures strictly guard against fire, in contrast to the instigator of the stupid “alternator upgrade.”

There is no issue in respect of battery life in this regard, as could be applied to the “Upgrade” mod.