Alternator producing too much voltage

Tunajoe · Jun 15, 2016

So on my return trip from Catalina last week, I had an alarm go off and after looking around saw that my voltage gauge was pegged at around 16 volts.
So I backed off the throttle, and the needle on the gauge bounced around and then settled on about 14 volts.
Over the course of close to an hour, it set off the alarm several times before finally settling to around 14 volts ( which I assume is close to normal).
This was on a 270 HP Cummins 6BTA 5.9.
I'm assuming it's the voltage regulator?
Is it built in to the alternator? Could it be my battery going bad?
Any suggestions?

Thanks!

O C Diver · Jun 15, 2016

Yes the regulator is built into the alternator unless you have an aftermarket setup such as an external 3 stage regulator. You can also have a wiring problem which may cause this. Simply, the regulator has to sense the battery voltage to regulate the alternators output. Some boat setups utilize a multiple battery charging isolator. A loose wire or failing diode may keep the regulator from sensing the batteries voltage and triggering an increase in voltage output. If your setup is pretty standard, I would start by removing the alternator and have it tested at a shop that specializes in rebuilding starters and alternators.

Ted

FF · Jun 15, 2016

If finding a loose wire does not fix it and you have to remove it , take it to an alt shop not just a big box shop that will test if for free.

If the V reg is shot have the tech remove the built in reg and lead the field wire out.

Then purchase a 3 or 4 stage regulator from a boat source and the batts may charge in 1/2 the time , and you can control the charge.

IF the alt is a large frame , just get a new truck unit 135A,, $135.00 as it already has the wire for an external regulator.

sunchaser · Jun 15, 2016

Assuming your alternator is removed and diagnostics show it is kaput, nothing the matter with replacing it in kind. External regulators are not free nor do they necessarily assure an improvement. Millions of internally regulated alternators are installed every year in a variety of highway vehicles and driven blissfully ignorantly by the masses.

If you have a real need for more charging amps then by all means consider the more expensive and additional wiring alternatives. Be prepared for some surprises if you stray from existing setup. Not all of us have a need to change for change sakes. Just my 2 cents worth.

Tunajoe · Jun 15, 2016

thanks guys for the info.
The alternator is whatever came stock with the boat in 2004. I have 725 hours on the engine, and 1.5 years ago replaced the start battery.
It was flat calm on my trip to Catalina, both coming and going. So it's not like a wire was jarred loose. Although I guess engine vibration could have done it.
I have had no problem with how the batteries are being charged, so I'll probably just replace it with what is on there.

bayview · Jun 15, 2016

before fixing something measure the voltage at the battery and compare to your bridge reading.

kelbylinn · Jun 15, 2016

Same problem with my alternator on the port engine a couple weeks ago. Bad built in regulator so just replaced the whole unit. Will see about repairing old one for a spare.

FF · Jun 16, 2016

"Millions of internally regulated alternators are installed every year in a variety of highway vehicles and driven blissfully ignorantly by the masses.'

True, but few autos have a house bank of 400A to perhaps 1200A in size, that they are hoping to charge before shut down.

The 3 or 4 stage regulator is worth the effort for folks that may be operating the engine a short time , a few hours,

No matter how large the alt is it will only charge at the rate the V red decides is proper.

The single wire auto V regulators expect to keep the voltages up for power accessories and do almost no charging.

They expect to find a batt down 2% , not 60%.

The 3 & 4 stage V reg attempt to put the max charge the batts will take, as soon as the power is available, that's why the better ones have a batt tamp sensor.To not overheat the batts under heavy charge.

Running from Marina to Marina the auto brained single wire units are just fine.

The non marina cruisers will usually require the smarter regulators.

Bruce B · Jun 16, 2016

FF said:
"Millions of internally regulated alternators are installed every year in a variety of highway vehicles and driven blissfully ignorantly by the masses.'

True, but few autos have a house bank of 400A to perhaps 1200A in size, that they are hoping to charge before shut down.

The 3 or 4 stage regulator is worth the effort for folks that may be operating the engine a short time , a few hours,

No matter how large the alt is it will only charge at the rate the V red decides is proper.

The single wire auto V regulators expect to keep the voltages up for power accessories and do almost no charging.

They expect to find a batt down 2% , not 60%.

The 3 & 4 stage V reg attempt to put the max charge the batts will take, as soon as the power is available, that's why the better ones have a batt tamp sensor.To not overheat the batts under heavy charge.

Running from Marina to Marina the auto brained single wire units are just fine.

The non marina cruisers will usually require the smarter regulators.

This is exactly correct!
AGM batteries are expensive and if cared for properly they can last a long time with lots of capacity and voltage... The price of a good regulator is small in comparison to premature battery replacement.
Bruce

sunchaser · Jun 16, 2016

FF

I well remember the many posts where you cite KISS. I agree, where applicable.

Alternators with built in regulators are very long lived. I am amazed at how well they do under the hood of a car merrily whirring away in extreme heat, dirt, rain, sub zero etc. Then throw in the alternators under the cowl of a haul truck, dozer, grader or locomotive and the robustness of the internally regulated alternator becomes obvious.

The OP has a need for replacing a simple device that seems to have performed well in its current application. Most likely sitting for days on end in a salt water environment did it in. Tough duty for all sorts of things marine. Unless there is a new need, I can't see complicating it with a non applicable offering from Balmar or others.

MurrayM · Jun 16, 2016

sunchaser said:
FF

I well remember the many posts where you cite KISS. I agree, where applicable.

Alternators with built in regulators are very long lived. I am amazed at how well they do under the hood of a car merrily whirring away in extreme heat, dirt, rain, sub zero etc. Then throw in the alternators under the cowl of a haul truck, dozer, grader or locomotive and the robustness of the internally regulated alternator becomes obvious.

The OP has a need for replacing a simple device that seems to have performed well in its current application. Most likely sitting for days on end in a salt water environment did it in. Tough duty for all sorts of things marine. Unless there is a new need, I can't see complicating it with a non applicable offering from Balmar or others.

Hamilton Ferris PowerMax LT Small Case

Tunajoe · Jun 16, 2016

MurrayM said:
Hamilton Ferris PowerMax LT Small Case

thanks for the link!

FF · Jun 16, 2016

Weather 3 or 4 stage regulator is an advantage is mostly a matter of TIME.

If the house batt set is down to 50% a 3-4 stage will get the charge done in the least amount of TIME.

IF time is a concern to the operator the added complexity of a smarter regulator is worth it.

Battery life depends on a full 100% charge after a deep cycle event.

For a boat that seldom sees much battery use the single wire does work just fine.

For deep cycle batts a slight over charge before dropping to float is now recommended by many mfg for wet batts.

For some mfg it is instead of an equalizing charge.

This can be done with a smart 3-4 stage V reg , although its better done by a smart solar regulator with a solar panel.

Some new shore power batt chargers have adjustable charge profiles that can also equalize or do a slight overcharge.

clyde · Jun 16, 2016

i`ve had external 3 step regulators for yrs, tried the balmar for 5 yrs, and they had to replace them every yr! went to the ample power V3 for the last10 yrs, had a few loose wire problems, which at times made me almost cross eyed, taking off, and putting on for testing purposes, a 45Lb leece neville 130 amp alt, on the wrong side of the engine, over and over, checking voltages also over and over, gets old after 4+ months! so...i got rid of the one that had diode/brush problems, had #2 changed to internal regulation, now is my spare, and bought a new leece neville 160 amp, 14v to 14.25v, internal reg, pos/neg wires only! also went to 2.75" pulley`s, that will give me 20+ amps when trolling @ 600 rpm! leaving next week for our fishing grounds halfway to alaska, near bella bella, bc, for 2 months, to fill our freezers...will let the forum know how my new system works in september...clyde [will also miss our friend 'ron' who we always met up with!]

Paul M · Jun 16, 2016

Having sailed for long distances for as much as 12 days and also living on the hook in the Caribbean, FF's advice on what regulators do and don't do and what is appropriate for a particular style of cruising is "spot-on".

MurrayM · Jun 16, 2016

Tunajoe said:
thanks for the link!

No problem. You may want to contact them for information though.

When I installed it our SmartGauge wasn't happy and gave an error reading because the alternator was giving 15.45 volts.

Turns out it settles down to 14.something volts after about 5 minutes or so, then it's "situation normal" as far as the SmartGauge is concerned.

Don't know if it bulk charges at 15+ volts yet as I haven't had the batteries depleted enough. We have golf cart wet cells, so I'll keep a close eye on fluid levels for a while.

Long term plan is to install a Sterling Alternator to Battery Charger which, according to the manufacturer, lowers the voltage and performs some Voodoo magic to shorten charging times, so I'm not too concerned about the 'high' charging voltage for the time being.

Then again, if I had an audible alarm I might be more motivated to find an answer...

Tunajoe · Jun 18, 2016

So I went down to the boat today and took a serious look at the alternator.
When I jiggled the 3 wire plug going into the alternator, I was surprised to see that it was loose.
So I pulled it off (easily) and noticed some rust/corrosion.
I scraped the prong with a thin sharp knife and plan on going back and using some sandpaper to clean it.
Any other suggestions?
I didn't have any schematics handy, so I really couldn't ID what the wires are for.
Anyone know?

FF · Jun 18, 2016

Voltage regulator or tachometer would be my guess.

DavidM · Jun 18, 2016

The drawing attached is courtesy of Tony Athens on boatdiesel. One of the connections to that plug is the battery voltage sense wire. If it is loose it will cause the alternator to fluctuate and output high voltage. Clean up the terminals, spray it with WD40 and your high voltage problems will be gone. You may need to crimp the spade connectors with needle nose pliers to make better contact.

David

sunchaser · Jun 18, 2016

For over a century the Prestolite Electric company has made auto alternators and generators. They purchased Leece Neville, Motorola and Lucas decades ago. I have internally regulated PLs on my engines and after a dozen years are still whirring away. When cruising they push the house (eventually) and start banks to 100% according to the BMKs.

Oh, the PL alternators cost less than a some of the external regulators. Not to mention fighting the not uncommon issues Clyde on Skookum raises. His findings will indeed be interesting.

Again, I am not anti external regulators when they are needed. On short hop boats that may be a good add on to consider. Or just a bigger Prestolite Alternator. They make up to a 120 amp 12V single belt unit.

MurrayM · Jun 18, 2016

Good sleuthing

If that connection is badly rusted, there may be others. Our Yanmar wouldn't start one day and it turned out to be corrosion on the ignition wire connection on the starter (found it 5 minutes with the help of the trouble shooting section in Nigel Calder's book) so it seemed to make sense to check & spray all electrical connections.

Hope it's that simple!

bayview · Jun 18, 2016

Once you get it clean a little dielectric grease will reduce future corrosion.

sdowney717 · Jun 18, 2016

You can pull the connector out and examine its condition, usually a little prong must be depressed on the wire side. The connector could be loose and corroded on the inside. High resistance makes these overheat, then the metals loose spring tension.
Cleaning the outside wont do much.

Usually these are tin coated, I have cleaned some of these with white vinegar, which can strip the tin. Then you can grease it or spray it with some oil.

Alternator producing too much voltage

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