Alternators - What's the Difference ?

[DeepFrz]

We use Bosch 120amp alternators, 1/3 the price of Balmars, because of gearing can only pull about 80 amps

That is great if you only need 80 amps. Probably internally regulated as well. Okay for a small battery bank with low power demands.

I guess you use two alternators putting out a combined 160 amps.

[motion30]

I bought a delco single wire alt 100 amp from a local rebuild shop, I have over 600 hrs on it and it still performs fine I paid $100 same pully size as the former 55 amp model

[Nauticatarcher]

Originally Posted by DeepFrz

That is great if you only need 80 amps. Probably internally regulated as well. Okay for a small battery bank with low power demands.

I guess you use two alternators putting out a combined 160 amps.

Alternator is externally regulated and as when we are motoring it is more than sufficient as our main battery charging is done on Genset using 150amp charger in inverter, I dont beleive in running an expensive main engine purely for battery charging

[GordMay]

Delco-Remy Electrical Spec Guide (Alternators & Starters):
http://www.delcoremy.com/LiteratureD.../SpecGuide.pdf

[Cheechako]

I bought a delco single wire alt 100 amp from....... Is "one wire" externally regulated?

[motion30]

No, the one wire is internally regulated. Just has a self excited field circut Check with you alt shop perhaps they can make it that way BTY my research found 100amp is the most one can spin with a single 1/2'' belt

[Cheechako]

yea up to 100 amp should work with one belt in my experience. Your not getting near the output with that std internal regulator though. That's only an issue if you are sitting anchored and want to run the engine as little as possible. With a good 3 step regulator 100 is really max for one belt (and you get a lot of black dust on the engine!)

[over40pirate]

I used a Delco 17SI alternator on my Perkins 4-107 for 7 years of cruising. It is a 108 amp, large case, internal regulator, model. I believe it was from a mid 1980's Olds. and other GM cars.
I talked to an anternator rebuilder who sold them for use on sailboats. I bought one at a scrap yard and rebuilt it with a heavy duty rectifier and regulator, which he said he put in the ones he sold.
It worked great. I mostly used it with a manual home built controller to charge the batteries fast.
It worked fine with a single belt.

[Wainui]

I have a Motorolla 105 amp on my perkins 4108. If I drain my house batts down about 130 amp hours and then charge, it puts out about 67 amps but the belt will start slipping so I have to increase rpms slowly

[hellosailor]

Basically, a "one wire" alternator has had the voltage sensor tied back internally--so it is not reading the voltage at the battery, and not regulating the output of the alternator. It is simply "tied back" to itself so that there is 14.4V at the alternator output, with no adjustment for the wiring losses or battery condition.

A very inefficient way to go--but since many boats with dual batteries do not bother to run the voltage sense cable to the batteries, or switch it when they switch the batteries, no worse than typical on many production boats. A good way to encourage battery sales and engine hours though!

Gord-
Nice find on the Delco-Remy document! It must be fairly new. Do bear in mind that when "Delco" split, there was/is also the "AC-Delco" division, and IIRC they have still other "Delco" alternators.

[motion30]

Originally Posted by hellosailor

Basically, a "one wire" alternator has had the voltage sensor tied back internally--so it is not reading the voltage at the battery, and not regulating the output of the alternator. It is simply "tied back" to itself so that there is 14.4V at the alternator output, with no adjustment for the wiring losses or battery condition.

A very inefficient way to go--but since many boats with dual batteries do not bother to run the voltage sense cable to the batteries, or switch it when they switch the batteries, no worse than typical on many production boats. A good way to encourage battery sales and engine hours though!

Gord-
Nice find on the Delco-Remy document! It must be fairly new. Do bear in mind that when "Delco" split, there was/is also the "AC-Delco" division, and IIRC they have still other "Delco" alternators.

So are you saying these alt. are not regulated? Yes the voltage is 14.4 but viewing my amp meter the current does drop off as the motor is run and the battery become full. At any rate, does a much better job at charging my 500ah battery bank then the old 55amp mototola alt My amp meter only reads to 60amps and after drawing the batterys down the alt will peg the gauge for 20 minutes or so

[DeepFrz]

Originally Posted by motion30

So are you saying these alt. are not regulated? Yes the voltage is 14.4 but viewing my amp meter the current does drop off as the motor is run and the battery become full.

The current will drop off because the internal resistance of the battery increases as the charge level rises. A regulator will decrease the voltage after the battery is charged so as to not overcharge it.

Your alternator may do okay unless you do a lot of motoring after the battery is charged. You may find that it is over charging the battery bank, causing off gassing and water loss and damage to the plates, resulting in low battery life. It may also burn out if your battery bank becomes overly discharged and the alternator tries to maintain 14.4 volts while pumping out more current than it is rated to handle.

[motion30]

Originally Posted by DeepFrz

The current will drop off because the internal resistance of the battery increases as the charge level rises. A regulator will decrease the voltage after the battery is charged so as to not overcharge it.

Your alternator may do okay unless you do a lot of motoring after the battery is charged. You may find that it is over charging the battery bank, causing off gassing and water loss and damage to the plates, resulting in low battery life. It may also burn out if your battery bank becomes overly discharged and the alternator tries to maintain 14.4 volts while pumping out more current than it is rated to handle.

OK so is it possible to fit a regulator to this system ? OR best to shop for a 3 wire 100 amp unit
Now that I think of it, if the batterys are fully charged at the dock, at start up the amp meter reads very low about 10 amps. I sure would hate to kill over $1000 worth of 8d lifelines though.

[hellosailor]

"So are you saying these alt. are not regulated?"
No, I'm saying something quite the opposite. A 1-wire "generator" or "integral alternator" (the names change every few years) is fully internally regulated. BUT. That regulation is accomplished by taking the output voltage sensing wire, and connecting it directly to the output terminal IN the alternator itself.

This means that the alternator will be very precisely regulated--but it will also substantially ignore the external load and the external voltage drops and the battery condition. And, you often will need to goose the engine (i.e. to 2000 rpm for a few seconds) to make the alternator turn on, as the excite circuit also is tied back internally. If you just start to idle speed--it may not turn on for quite some time.

It is a great way to make a robust, simple, cheap circuit. It is not a very nice way to treat your batteries, or optimize your run time, or much of anything else. That's why it is relegated to some industrial, off-road, and cheap OEM setups.

On boats that were set up with two batteries form the factory, it can make sense because two batteries require TWO sense leads and a means of switching them, and instead of running one or two sense leads all the way to the battery compartment, the builder just ties the sense lead back to the output lead on the "side" of the engine someplace, i.e. at the starter connection, effectively knee-capping a 3-wire system and making it into a 1-wire anyway.

You could certainly break out the wiring on a 1-wire, or bypass the internal regulator and add an external. And Blamar and all will gladly show you how to fit an external regulator that can be switched in/out so the internal one can be used if the external one fails.

But no, I wouldn't use a 1-wire to start with, there's just no excuse for it in this application.

There are many ways to design a charging system, and drawbacks to many of them. For instance, if you read the Delco specs, some of the new alternators have avalanche diodes in them to clamp spikes to 40VDC. A great idea, to protect electronics from the normal spikes caused by alternators and starters, right?

Well...yeah, but those are consumable parts (the avalanche diodes) and what happens next is that when they DO fail, the alternator fails. Pick an alternator that's older and cruder and doesn't have them--and it just can't fail that way. (The spikes remain a separate issue but at least the alternator doesn't fail that way.)

ALL conventional internally regulated alternators are designed mainly for car use. That is, to provide one brief shot of high power to make up for what the starter consumed, and then to run all day without overcharging the battery! They are not designed to recharge deep cycle batteries, they are designed to "not cause damage from overcharging".

So unless you match up charing systems and battery capabilities very neatly...an external regulator (which IS usually set up to provide bulk charging for longer periods and IS often programmable to optimize what it does) can cut your run time dramatically. Worth the money, if you plan to really be using the boat, and the batteries, more extensively.

And personally, I hate lugging batteries, I'd rather lug them fewer times, even if replacing them was free! Every time I get near a wet cell battery, it winds up costing me some piece of clothing from acid damage. Or the carpet in the car. Or something.

[motion30]

I am with you on lugging the batterys. The lifelines weigh 158lbs each. I installed the one wire alt cause it was in my budget and so far have over 600 hrs on it in two seasons, Am I undercharging my batterties? I don't know. A typical day running the icw is 8 -9 hrs in the fall and 12- 14 hrs in the spring. Is resting battery voltage the best measurement of charge state?