AUTOMAC Output Low

Maine Sail · Jan 6, 2009

infamous-bob19215 said:
I have an 84 Catalina 30 which came with an Automac that was not connected to the Alternator. I obtained a manual for it, found the field connection (green wire) on my Motorola alternator, and performed the light bulb test to determine the type N or P and whether or not I have the right connection for the field. The book stated that when I get it right the bulb should glow and the amerage should increase. I was using a 10W bulb as told which did glow but did not increase or decrease the amperage. I switch to using my million candle power tourch instead of the 10W bulb and did notice a minimal increase or decrease when touching 12V or Ground. I tested the Automac with a 10W bulb which glowed and dimmed with the rotary knob so I made the final connection.
I was of the impression the Automac should force the Alternator to put out as much as you want it to but all I see ia approximately 2-3 amps improvement over the built in regulator output. My batteries were nearly fully charged when I tried this.
Can anyone tell me if this is normal or do I still have something wrong?

It's probably working as designed. You can only force as much into a battery as it will accept. This is called "acceptance" and it might be a good idea to read up on it so you have a better understanding. Essentially a multistage regulator will force only slightly more into the battery in bulk phase but as you get closer to full (above 80%) it will put out very similar amperage to the stock regulator. If it did not it would and could shorten the life of the batts.

It's also important to monitor the temperature of the battery seeing as these regulators are designed to "force feed" the batts, which is rsistance, and thus heat, which can hurt the batteries. Most good multi-stage regulators have a temp probe feature..

Stu Jackson · Jan 6, 2009

Automac Rheostat

What were you doing with the knob on the Automac amperage panel? Was the switch on the AM panel on? What voltages were you reading? What was the condition of your battery bank (full or empty?) Only way I can help is with this info.

Stu Jackson · Jan 6, 2009

infamous-bob19215 said:
What was the condition of your battery
Anywhere from slightly above the voltage with the Auto-Mac off to approximately 17 volts.
bank (full or empty?)
Batteries were nearly full charge one was slightly lower than the other --
One thing I found particularly disappointing is that the Auto-mac did not seem to compensate for items being switch on, I would have expected with the knob all the way up and more and more items turned on the amperage would have climbed significantly reducing the draw on the batteries.

Bob,

Full batteries will not make ANY alternator work, and any boat load you put on a DC system, even if the alternator is running, will be negligible. And certainly not visible on an analog meter.

Before you give up your system, recognize that your Auto-Mac (and any other) voltage regulator will only show a marked improvement in charging only when your batteries need to be charged.

What you should expect is this: with a discharged bank, say down between 80% to 50%, try the Auto-Mac again. Turn the knob all the way down, switch on OR off. Run the engine at cruising speed (best to have someone else steering) and then turn the knob up switch on to increase the amperage until you reach about 14.2 V. What you'll see is that the Auto-Mac will literally double what you'll get out of the alternator compared to what you'd see if you turned the Auto-Mac off or turned down the knob.

We worked ours with the ammeter on the AutoMac and a separate analog voltmeter on the house bank. You need to watch them both.

What it will do is increase the amperage you'd get out of your stock alternator.

Don't crank it all the way up because until you learn how to use the charging regimen, of keeping the charging voltage limited to the bulk charge rate of your bank, usually 14.2 V, you could fry your batteries. Learn what the setting is on the "trip," (usually 14.0V) but don't depend on it being that, as you know the instructions show how to determine and modify that voltage.

As you charge, the voltage will start rising, so you can then start turning the amperage down to avoid too high a voltage. Be careful not to overcharge (i.e., high voltage by trying to pump too many amps in).

I highly recommend Calder's Boatowner's Guide. Don't know what your background is on system charging.

In addition to Googling acceptance, try a search on this website, we had a recent discussion of just that.

Stu Jackson · Jan 7, 2009

Here's the link to the previous

discussion on acceptance: http://forums.catalina.sailboatowners.com/showthread.php?p=588261

That co.com thread includes another link to our C34 website discussion on alternator use.

What you'll find with your 55 A OEM Motorola alternator is that, depending on your house bank size, you will most likely never reach the acceptance level discussed in those threads, with or without your AutoMac, simply because you'll get nowhere near the 50 A output.

My eight years of experience with exactly your setup on our 1986 M25 engine with the same alternator and the AutoMac gave us a max of 25 A output on a discharged bank of 360 AH after a full day or even two at anchor, using the balance technique of proper (not excessive) voltage. Even if you "over volt" the AutoMac cutout will eventually kick in, not immediately though, which is an issue you should be careful with. Even if you "over volt," not that many more amps are gonna happen. Try it, you'll see. On a limited short time basis, you won't harm anything.

That's what I'd expect you to see, too. Check on back here with us when you give her a run, and let us know. If you do it soon, just add to this thread instead of starting a new one - it'll last here at least five days!

Remember, based on the links provided, that the acceptance discussion began only AFTER we'd removed the OEM alternator and replaced it with a higher output 100A alternator and external regulator and started measuring with our Link 2000.

All the best.