Technical Alternators/charging and 1 wire

Hey guys, visiting this subject again.

I bought a wire wire for my 40, charges but charges at 14.7 to 14.9. Now I had the same style (internally regulated) installed just recently but that one would charge at 14.9 to 15.2. I am concerned about eventually toasting the battery even at the 14.7/9.

I get these readings with both my analogue and digital meters by checking at the battery and or the back of the alternator.

The battery is brand new 12 volt. Spins the starter over like nobody's business. All wiring to the battery is new as are the cables, etc.

A should I be concerned about this high reading? I checked my Ford explorer and some of the trucks at the shop, they all show readings around 13.4 to 13.8.

B Since the naturally regulated alternator did not read lower nor did the 2 others used ones I had on the self, can I or should I externally regulate the new 1 wire?

Thanks in advance.

 

Where are you measuring the voltage? At the alternator, or the battery? or somewhere else?

 

You should be okay at 14.7 but it is at the top of the range. If you are reading 15 plus that will be an issue. Are the alt new/rebuilt? The 1 wire is internally regulated so maybe in need of a rebuild. I would think if you have an issue it is the voltage regulator.

 

It is also critical for good ground of the alternator with internal VR, as poor ground can cause increased voltage.

 

I just yesterday needed to verify a volt meter I dug out covered in dust. I stuck it on my daily and while running was seeing 14.7 volts.
Daily is an ‘03 Silverado on its 3rd battery. This one is 3 years old.

 

14.2 was always considered to be the ideal full charging voltage. I'd agree that 14.7 would be on the high limit of what you would want for long battery life. Too high of voltage is also going to shorten the life of headlight and tail light bulbs.

I've never been a fan of the one wire alternators except for what they were actually designed for. Diesel powered or gas with a magnito ignition farm tractors and farm equipment. Then street rodders picked up on it because they only had one wire to hide.

I have swapped regulators in regular internal regulator alternators a few times to get a more agreeable charging voltage. That was usually by hunting down a Delco or Napa Echlin regulator. I don't know if that works with the one wire setup.

 

Charging voltages like 13.8 or 14.2 or whatever are normalized for 77°F. I doubt it's that warm in Colorado right now?

It also depends on load, whether a battery is new or old, charged or discharged, etc. The point made about grounding is also a good one.

At idle 13.8 to 14.2 is in the zone. But it also has to work when you drive it. Turn the headlights on HI beam, turn the heater blower fan on HI, the radio, etc., and bring the RPM up to around 2000 or so and hold it there while measuring voltage at the battery posts. It is important to have absolutely clean and tight electrical grounds and connections.

 

An alternator is supposed to be regulated at 14volts. It should put out 14 volts are anything above the excitation RPM and never drop below that unless its amp rating is exceeded.

You didnt say what brand your alternator was, but the ones I deal with have available adjustable regulators. But I only use 2 wire units to retain a charge light on the dash. Bosch is my preference.

 

The voltage output of the alternator is relative to the amp load. You only see the limit of the voltage regulator when the amp load is very low. Saying that another vehicle only shows 13.8 volts doesn't take into account amp load. If the amp load is high, the battery is low or on it's way out, the voltage from the alternator is lower. With that said, I wouldn't worry about 14.9 volts. If it is getting to 15 or above it may present a problem. Back in the 70's some of the Ford systems were set to 15.2 volts, but that's with batteries from the 70's.

 

I completly disagree.

A charging system with an electronic regulator should put out its rated voltage up to the max amount load of the alternator.

The biggest issue with one wire units is the resistance of the wire between the battery (load) and the alternator. If the wire is too small or has excessive resistance the internal regulator will end up under charging at the battery.

A regulator Monitors output voltage and varies the DC voltage it puts into the rotor via the brushes and slip rings. A high output voltage is completly the result of the voltage regulator. Chinese parts etc....

 

Did you install it correctly? The signal wire is supposed to be connected downstream on the charging wire, not at the alternator

 

uh....we're talking about a one wire alternator. There is no separate signal wire.

 

Really!! Tell that to my 10 year old, 20,000+ mile $60.00 rebuild from O'Reillys. And it is on a [gasp] 12V "upgrade" on a BUICK. "course, there is a 8ga wire from the alternator to the battery.

Ben

 

Look at a wiring diagram for the one wire alternator. Be sure if is correct

 

The alternator connects to the battery, with one wire. Pretty hard to go wrong there.

 

@Stonehenge In your original post you mentioned a couple different alternators, plus a couple more on the shelf. Are they all the same (ie, one wire) or are some internally regulated with a sense wire? Where are you measuring the voltage?

Here's the deal: If you have a three-wire Delco 10si/12si and it is wired correctly with the voltage sense lead wired to the battery the voltage at the alternator will be higher than the ideal charging voltage, as it is using the sense lead to determine how much voltage it should charge at. Basically it is taking into account the voltage drop between the output of the alternator and the voltage where the sense lead is connected.

A one wire alternator does not have this capability, and is regulated to the voltage at the output of the alternator. It has no way of knowing what the voltage is at the battery.

I consider one wire alternators to be the easy way out, and a less than ideal solution. Wiring a three wire alternator properly is not difficult at all. I live next door to one of the village idiots, and he was able to set up a three wire charging system correctly. He mentioned that it was intuitively obvious to even a casual observer how it should be done.

 

38Chev454>>>It is also critical for good ground of the alternator with internal VR, as poor ground can cause increased voltage. >>>

This. Install a separate ground strap to a good ground. That's what this threaded hole is for. The alternator mounting points sometimes don't provide a good ground to the alternator's aluminum body. Then quit monitoring & fretting over the alternator's output voltage with your multimeters. Your battery will be fine. Jack E/NJ

 

Don't know how I screwed that up, but here is my response to Fabulous 50's.

You are somewhat correct, except that alternators are rated by amperage output not voltage. The rated voltage is 12 volts not the high voltage limit of the regulator. To check alternator maximum output in amps, you can load the system with a carbon pile to pull the voltage down to 12 volts, then read the amperage at the alternator output wire.

With a properly sized alternator, you will see the voltage go down as loads are applied to the system. A 30 amp alternator will be near 12 volts if you add a 30 amp load. The voltage regulator will be full fielding the alternator at that time. Take the load away and the voltage will go up and the regulator will begin limiting field current.

 

I wonder where you got 12 volts from? I think you'll find lead acid batteries like to be over 13, when they're in a system doing work (ie the engine is running). If the system is at 12 volts, the battery is either discharged a lot, or will be soon.

And that "ground strap" threaded hole on the back of the alternator, is for a mounting bolt, it's not for a ground strap. I've never seen an instance where a securely mounted alternator is not getting a good ground, unless perhaps it's one of the oddball ones that has vibration isolation mounting bushings. But then it would not be a 10SI alternator.

 

It's definitely a bit of a moving target, and some manufacturers have different ideas on what the ideal voltage "set point" is. Imports tended to be higher than domestics, at least years ago. There will always be some voltage sag under heavy load.

Basically any battery needs about 2 volts above and beyond its open circuit voltage applied to approach a full charge. This takes a long time to get to that point, most batteries spend hours just soaking up current in what's called the "bulk phase".

 

If you connect that charge indicator wire, it ain't a one wire alternator any more, eh? And that's not the one that tells it the battery voltage, anyways.

 

The 12 volts comes from the alternator manufacturers. I agree that you need at least 0.5 volts over battery voltage to charge a battery, but what I'm saying is that is how Delco Remy rates their alternators. It is not at the voltage regulator limit. Leece-Neville was the same when I worked at a fleet that ran them. Delco used to stamp the rating and voltage on their alternators. It was XX amps at 12 volts. The testing procedure came directly from Delco, but it was really the same as the old Sun test procedures.

 

oh, you're talking about testing conditions, not operating conditions. That explains it.

 

If you've got a alternator with a powder-coated case and/or the mounting brackets are coated or even if it's all painted, it's possible to have a poor ground.

I know that Ford used a separate ground wire from the alternator case to the regulator case on their externally-regulated units to prevent this very problem...

 

GM alternators, before the internal regulated type came along, had a ground stud on the back. I can understand having a ground reference for an external regulator. But I still have not encountered an alternator that was having trouble grounding the case to the engine.

 

I used a 10si on a ‘42 Ford I converted to 12v. I jumped one wire on the alternator to another and then ran a wire through a bulb to ground. I found the diagram on MadElectrical I think. Been several years why I’m hazy on it. Worked fine, light would be on when I first started the truck, let it idle for a few minutes then take the engine up to about 700/800 RPMs, light would go out and alternator would charge.
Guess it was a way to make it a 1-wire alternator?
Anyways, wish my memory was better

 

If the 2 terminals are jumped to each other, won't the alternator produce full charge all the time?

 

With a one wire alternator your battery "might not" be fine. You need to have appropriately sized conductors that carry the current between the alternator and battery.

Let's use an exaggerated example using the following information:
1. Ideal lead acid battery float voltage 2.3 volts per cell, 13.8 volts for a 6 cell battery
2. Ideal fast charge voltage 2.45 volts per cell, 14.7 volts for a 6 cell battery
3. Load on the alternator is 20 amps
4. Ronnie Rodder thinks wire is wire, and has a total of 5 feet of 14 gauge wire in the charging circuit
5. One wire alternator, so no sense lead.

In that short piece of wire you will have a voltage drop of 0.6282 volts. The float voltage at the battery is 13.172 volts, or 4.55% less than it should be. This assumes no additional loss in connections, poor crimps, off-shore copper, etc.

Let's make it worse. Ronnie Rodder ran his copper fuel lines along his exhaust pipe and past one of the exhaust manifolds. His fuel was cheap crap that boils at 154°F, and he was running hard up Dromedary Road to Camelback. Naturally that shit boiled and he had a bad case of vapor lock. He cranked and cranked until the battery was just a hot plastic case full of lead, lead dioxide, lead sulfate and sulfuric acid. Ronnie Rodder fiddle-farted around for about 40 minutes and finally figured out that he might be able to start the car by coasting down the slope, slip the trans into 2nd, and let the clutch out. Sure enough, there was just the tiniest bit of current available in that battery to make a spark and the car fired up. Now he's got a battery that needs a real good charge. Ronnie has a 30 amp one wire, and the battery will take as much current as there is available. Let's keep in mind that it's a one wire alternator, no sense lead. He has to rev the engine in order to get that one-wire alternator excited and creating current. Now we've got a 0.9424 volt drop between the alternator and the battery. No sense lead, alternator doesn't know what's going on at the battery, and it never gets fully charged. The battery sulfates to the point of uselessness, and Ronnie has to put a new one in his hot rod every 2 years.

None of you need to point out that a 14 gauge wire is too small, and will likely burn up. I know that. Use 12 or 10 or 8 gauge, the effect is less but the fact remains that a one wire alternator isn't an ideal solution. Ronnie probably doesn't understand electricity, and there are enough examples of Ronnie on the HAMB that this scenario probably happens more than we think it does.

None of you need to point out that you've used a one wire alternator for 29 years, and are still using the battery that came in your grandfathers 1957 Packard. Good for you. A one wire alternator is not an ideal solution. (Did I say that already?)

The moral of the story: LEARN HOW TO WIRE A 3 WIRE ALTERNATOR, AND DO IT!!

Voltage drop can be calculated using the following formula:

voltage drop VD = (M × K × I × L) ÷ CM

“M” = phase multiplier: Use 2 for a single phase or DC circuit and 3, or 1.732, for a three-phase circuit.

“K” = direct current constant: Use 12.9 for a copper conductor and 21.2 for an aluminum conductor. This is equal to the resistance of a conductor that is one thousand circular mils and one thousand feet in length.

“I” = current: This is the current of the circuit in amps.

“L” = length in feet: This is the one-way length of the conductor in feet.

“CM” = cross-sectional area: This is the cross-sectional area of the conductor in circular mils.