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Old 09-03-2014, 12:12 AM   #21
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Brooksie,

Take a look at this link discussing charging regulators. It does a great job of explaining what our regulators are doing and why.

There's a video at the bottom of the page that I'll paste below. It's the best description of the charging process I've come across. If your battery voltage is up to its 14.x V absorption threshold, the current (amps) will be limited to avoid exceeding the voltage target. This is illustrated very well at about 4:00 in the video.



It very well might be that your alternator is doing exactly what it needs to do in recharging your batteries. It might be that the only time you'll see max output is when your battery bank is very low with the resting voltage below 12.2V and the regulator is pushing max current into the battery to get the battery to its 14.x V threshold. Once that voltage is achieved, the current ramps down to maintain the fixed voltage.

Question: Did your alternator formerly exhibit different charging characteristics than it now exhibits? If so, maybe your battery capacity is reduced due to battery age. If it never showed full current during even the most aggressive charging events, maybe your cabling is undersized for the current.
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Old 09-03-2014, 06:43 AM   #22
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>I can't think of anything internal to the alternator that would allow partial output other than diodes.<

A bad diode or two can be noticed by watching to see if lights bounce, go bright and dim at low rpm.
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Old 09-03-2014, 09:15 AM   #23
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The tester would be draining the battery while the alternator was trying to pump enough current to bring the voltage across both devices up to a certain level. If that voltage was above the full charge rate set voltage of the alternator it would cut back. It is the voltage at the terminals that decides the charge rate so if you did the test again you could measure that and look at what current the regulator should allow at that load voltage. Full charge is probably at a very low voltage.
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Old 09-03-2014, 09:18 AM   #24
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Al's posted video shows why battery voltage while in use should not be used to judge state of charge. The good news is that if you charge under these conditions at 12.2 volts (about 50% SOC) you would err on the conservative side. I did that until installing a SOC meter.
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Old 09-03-2014, 09:34 AM   #25
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Quote:
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Al's posted video shows why battery voltage while in use should not be used to judge state of charge. The good news is that if you charge under these conditions at 12.2 volts (about 50% SOC) you would err on the conservative side. I did that until installing a SOC meter.
Which is why a SOC or BMK type device with their various data readouts is a worthwhile gift to your boat. We have them on both house and engine start battery banks.

In this era of great boat application of solar as waxed eloquent by Deck Officer, Twisted and now and then Reuben Trane (we are indeed lucky to have him show up) all sorts of neat measurement devices are available to provide information on battery and charging device health.
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Old 09-03-2014, 01:13 PM   #26
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Balmar quote:

"Forget the rumor that an oversized alternator will destroy your batteries ... the truth is that the acceptance rate of your batteries will dictate how much amperage the alternator will provide."
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Old 09-03-2014, 05:21 PM   #27
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Brooksie,
Question: Did your alternator formerly exhibit different charging characteristics than it now exhibits? If so, maybe your battery capacity is reduced due to battery age. If it never showed full current during even the most aggressive charging events, maybe your cabling is undersized for the current.
Yes, as I said in the begining, I would formally notice it charging away @ 60-60A after an overnight with the reefer on. Now it never exceeds 25A (or 45A with the 150A load tester on it)

B/4 I start messing about with my expensive, and here-to-for trustworthy, 3 step regulator; I will take the alternator off and have it checked at the local autoelectric shop. I think they will do it the same way I did... but we shall see. If I gain any knowledge there I will relate same back to the forum. But I won't be doing it right away.
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Old 09-03-2014, 05:36 PM   #28
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Check your cabling for a loose ground while you're at it. The increased resistance through a degraded alternator ground could inhibit current flow like an undersized cable would.

How old is your house bank?
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Old 09-03-2014, 05:57 PM   #29
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Check your cabling for a loose ground while you're at it. The increased resistance through a degraded alternator ground could inhibit current flow like an undersized cable would.

How old is your house bank?
All connections good, originally crimped and soldered, #4 tinned wire, seperate #4 ground from alt case to starter bolt the 2/0 cable to bat-. House bank 2007, 2-T105's
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Old 09-03-2014, 06:13 PM   #30
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Take it to an alternator shop, not AutoZone or O'Reilleys. Most alternator shops will test it for free.

Saves a lot of time and frustration.

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Old 09-03-2014, 07:29 PM   #31
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A 7 year old pair of GCs as the house bank might be approaching the end of their life expectancy. If your batteries are weak, they won't be able to accept the charge available. It's the acceptance rate of the batteries that will determine the current flow. If the batteries are sulfated, they will suffer a reduced acceptance rate.

Have you noticed reduced battery capacity during extended periods on the hook? Do you have a SOC meter?
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Old 09-03-2014, 07:43 PM   #32
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Old 09-03-2014, 09:42 PM   #33
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Take it to an alternator shop, not AutoZone or O'Reilleys. Most alternator shops will test it for free.

Saves a lot of time and frustration.

Bob
That's what I am going to do.
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Old 09-03-2014, 09:50 PM   #34
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A 7 year old pair of GCs as the house bank might be approaching the end of their life expectancy. If your batteries are weak, they won't be able to accept the charge available. It's the acceptance rate of the batteries that will determine the current flow. If the batteries are sulfated, they will suffer a reduced acceptance rate.

Have you noticed reduced battery capacity during extended periods on the hook? Do you have a SOC meter?
I did a load test on the batteries first and they were good. That's when I decided to "load test" the alternator. My reasoning: each load I turn on, pumps lights reefer causes a rise in the output of the alternator, so why not turn on the 150A load tester and see if the meter will go up to the 90A set point I put on the regulator.No, no SOC meter, never saw the need. How would one help in this situation?
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Old 09-03-2014, 10:07 PM   #35
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No, no SOC meter, never saw the need. How would one help in this situation?
It would give you a good picture of the health of your house bank. Not a perfect picture, but a good one.
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Old 09-04-2014, 06:16 AM   #36
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One hassle to remember when having the shop bench test an alt is the unit will be cold.

Many light duty auto style will loose 25% to 50% of their charge ability when Hot
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Old 09-04-2014, 08:18 AM   #37
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I think we have a winner now that we know the batteries may be getting long in the tooth.
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Old 09-04-2014, 08:32 AM   #38
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I think we have a winner now that we know the batteries may be getting long in the tooth.
Could very well be, I plan to replace them this winter anyway. I may just continue on and finish the season out b/4 doing anything.
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Old 09-04-2014, 08:37 PM   #39
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Reporting back...
I did take my alternator to a shop to have it checked and no it was not putting out full amperage nor even the 90A that I had set on my regulator. It was. however, putting out correct voltage.

And yes, my method of putting the battery load tester on it was correct, it should act just like any other load you switch on and cause the ammeter to jump up just like a pump or light does.

By the way, I bought it from Alterstart in TX in 2007 for $100 and it has worked well for all these years.

I'll report again on the shop's findings.
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Old 09-05-2014, 01:39 AM   #40
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That's good info about how you used the load tester for added draw.


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