Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
Slow down guys!
You are both right and wrong for different reasons.
One wire and three wire alternators both require a regulator, what is different is where the regulator resides and where the regulator senses the output voltage. The one wire alternator has the regulator built in and it's voltage sense point is at the alternator's output terminal. The three wire alternator regulator is external and can, within reason, be mounted anywhere on the car. Further it's sense point can also be any where you want on the wire path between the alternator and the battery.
So Stern is correct to specify attaching the headlights directly to the alternator IF IT'S A ONE WIRE ALTERNATOR. However if it's a three wire alternator the optimal connection is where the voltage regulator does it's sensing - ie at the number one splice.
On my '70 Fury the number one splice ties one end of the ignition ballast resistor and the regulator sense wire to the #12 connection on the bulkhead. On the dash side, #12 goes to another master splice which feeds a bunch of things including the fuse distribution panel. In other words the wire between these two splices is where regulated voltage will be found and it where virtually all the car's electrical load is connected.
Someone commented that measuring voltage at different points on the wire between the alternator and the battery would not read different values. True ONLY if the current in the wire is very low, otherwise the readings will vary from spot to spot. All wire has some resistance and anytime current passes through a wire you will get a voltage drop. The bigger the current, the bigger the voltage drop.
This is Ohm's Law and it says Volts = Current X Resistance. Picking an easy figure, assume there is 1 ohm of resistance in the path between the ammeter and the battery. If you send 1 amp down the wire, you will lose 1v along the way. If you send 12 amps down the wire, you will lose 12 volts. See the problems you get with dirty connections!
This highlights another problem, fusible links. A fusible link is a piece of resistance wire designed to drop voltage and generate heat as the current climbs. At some design limit, the wire melts to completely isolate the circuit. This is somewhat different than a fuse and completely different from a circuit breaker. A circuit breaker is triggered by a resistance wire, but that wire is not in series with your load so you do not see a voltage drop across the breaker. A fuse is in series but it is very short and fairly fragile so it doesn't generate much of a voltage drop before it fails. A fusible link however is longer and tougher and does introduce a significant voltage drop before it melts. Our three wire systems make use of this voltage drop to ensure the battery never gets full voltage at high charging currents.
Question, if a fusible link creates a built in voltage drop, why do people want to use them then instead of breakers or fuses? Seems to me using a fusible link on a high current load like headlights will guarantee the headlights never see full voltage.
Now here is the thing about batteries, a fully charged cell is 2.1v to 2.13v making the battery 12.6v to 12.8v. If you over charge you get gassing, sulfation and battery damage. Interestingly, starting batteries are not designed to have their charge continuously topped up, as is done in virtually all automotive applications. Used properly they should be fully recharged and then stored disconnected from the circuit until they are needed again to start the engine. Anyways, I'm wandering off topic. Suffice it to say, because of the fusible link, your battery will never get even 12v while it is drawing heavy current from the alternator. So connecting high current headlights directly to the battery is a poor idea.
Joined: Thu Feb 12 2009, 02:56AM
Location: Portland OR
Posts: 690
I would venture to say that if I proved it to you with a Factory technician saying the words for me you would still say Im wrong so as I said b4 Ill agree to disagree BUT THIS ARGUMENT IS OVER!!!! I will no longer reply to any of your posts. Thanks and have a nice day.
Joined: Thu Feb 12 2009, 02:56AM
Location: Portland OR
Posts: 690
That is what ive been saying Thx FURY440. But the real disagreement is in what is now being referd to as a "fusible link" I guess I over explained its purpose, maybe your simpler way of putting it will end this VERY UNPRODUCTIVE disagreement. Thanks again
Joined: Mon Oct 10 2005, 12:45PM
Location: Albany NY area
Posts: 606
no one agreed that there is a special reistance wire used to reduce charging voltage to the battery. <span class='smallblacktext'>[ Edited Wed Feb 25 2009, 06:20PM ]</span>
VIP driver wrote ... The main battery cable that goes to the starter itself is not the one in talking about. Just the little one boing to the starter relay, that should be the resistance wire. Like I said it sounds hokey but it is true.
Why is this resistance wire there and what is it's purpose?
Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
Actually that is part of the reason why the battery charging current passes through the fusible link.
Anyways, calm down guys, life is too short to get into battles over terminology!
Things "electrical" and "electronic" seem to attract urban legends like a dead rat attracts flies. After all, how can something so simple as electricity be made to sound so complicated? Well sometimes it just is and what you think you see happening, really isn't whats going on at all. This is the case in a three wire alternator charging system.
Joined: Sun Feb 26 2006, 08:46PM
Location: Kingston,Ontario
Posts: 5622
VIP driver wrote ...
VIP driver wrote ... NO that is not correct!!!! The battery is wired to the starter relay with a special RESISTANCE wire. the alternator is wired thru the amp guage in the stock harness not strait to the battery. get out your prints and please verify this as I am sure I am correct. NEVER connect anything in a NON 1 wire alternator setup directly to the battery. In regards to MR Sterns advise on his site he is not being specific to our needs and is correct in his statements if it were a 1 wire internally regulated alternator. Not trying to insult anyone but the facts are the facts. Thanks
Also I am 100 % positive 68CBARGE will confirm I am correct. So dont just take my word for it if you are the type to never be satisfied. !drive
Huh? I am lost here.What happened to this thread.Ey Yi Yi. !stars VIP,I am sorry but you must have misunderstood what I was saying.There is no "special resistance" wire from the battery to the starter relay.You may have got that mixed up from the fusible links that I stress using when doing the wire upgrades I suggested. Anything you add to the battery stud at the relay I install fusible links for easy location and repair.
<span class='smallblacktext'>[ Edited Wed Feb 25 2009, 07:04PM ]</span>
Joined: Sun Feb 26 2006, 08:46PM
Location: Kingston,Ontario
Posts: 5622
drchallenger1 wrote ... so how come its common practice to run a wire from the alternator directly to the starter relay? in 20+ yrs i have had no battery exlposions.
I never experienced any battery explosions at all with this wire upgrade. The only time I seen batteries explode is when they are frozen from extreme cold temperatutres and was on a battery charger. The bypass wire uprade has been applied for over 15+ years by Richard Ehrenberg of Mopar Action.If it was NFG he would never had written and article about it. I have been driving my cars over 9 years with the wire with no problems.It really does take the load off the ammeter guage--kinda like a piggy back. VIP,relax.No need to get in a tither.You are reading too much into it.
<span class='smallblacktext'>[ Edited Wed Feb 25 2009, 07:15PM ]</span>