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Old 07-27-2012, 04:45 PM   #1
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Alternator issues

I have a Leece Neville alternator, model 8MR2049KA (http://www.prestolite.com/pgs_produc...item=8MR2049KA). It's suppose to give 51 amps but now that I have a Xantrex battery monitor, I can see it's only giving 8-10 amps, confirming my suspicion that it was under charging my batteries. I also have an external regulator (attached picture). I'm wondering if this could be the source of the problem. If my alterntor already have an internal regulator (from the specs I think it does), maybe this thing is useless and causing a big voltage drop. My guess is the regulator was part of a previous installation and the PO didn't bother to take it out when he got the Leece Neville. Any thoughts?
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Old 07-27-2012, 05:26 PM   #2
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If the alternator isn't putting out the amps first check the belt.

Check the simple things first

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Old 07-27-2012, 08:23 PM   #3
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The belt is fine. I've changed it and it's on thight. The voltage output at the battery is only 12.9 when the engine is running.
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Old 07-27-2012, 08:59 PM   #4
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The belt is fine. I've changed it and it's on thight. The voltage output at the battery is only 12.9 when the engine is running.
Try cleaning the alternator and battery connections. Then take a look at the fuse holder between the alternator and battery. Take it apart and clean the contacts with emory cloth.
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Old 07-28-2012, 07:03 AM   #5
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If my alterntor already have an internal regulator (from the specs I think it does), maybe this thing is useless and causing a big voltage drop. My guess is the regulator was part of a previous installation and the PO didn't bother to take it out when he got the Leece Neville

The alts made for auto service have the reg inside and are usually referred to as "one Wire" as that is all that needs to be hooked up.

An alt can be repaired to junk the internal and install an external reg.

A L/N is frequently fitted with an external regulator , that has the same rotten charge profile as a car alt.

Weather internal or external the car brained regulator must be removed for a good 3 stage regulator to function properly.

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Old 07-28-2012, 09:46 AM   #6
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Just some thoughts, are you getting proper RPM at your alt? Most auto electric shops could test it on the bench and/or remove the internal reg if you are wanting to use external only. They could do it for a lot less than a marine shop will.
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Old 07-28-2012, 01:29 PM   #7
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Good idea

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Just some thoughts, are you getting proper RPM at your alt? Most auto electric shops could test it on the bench and/or remove the internal reg if you are wanting to use external only. They could do it for a lot less than a marine shop will.
Another approach would be to run a temporary heavy wire straight from the big terminal on your alternator to your battery bank. This eliminates any potential voltage drops in your battery bank. You can also install a plain old 60a+\ 60a- ampmeter from napa- inline - on this wire. A simple way to see amperage being put out. Of course, you need to remember your batteries " tell" the regulator what to put out.
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Old 07-28-2012, 01:43 PM   #8
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There's a thread here that talks about that "regulator". From the sound of that you would be wise to disconnect it so you aren't tempted to use it but if you leave it alone it likely isn't doing any harm. 8-10 amps sustained is probably all you can count on from the alternator with the existing internal regulator. You may get a brief bump higher than that if your batteries are drawn down but otherwise that's likely as good as it gets. Get a real external regulator or live with the output you are getting.
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Old 07-28-2012, 07:36 PM   #9
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There's a thread here that talks about that "regulator". From the sound of that you would be wise to disconnect it so you aren't tempted to use it but if you leave it alone it likely isn't doing any harm. 8-10 amps sustained is probably all you can count on from the alternator with the existing internal regulator. You may get a brief bump higher than that if your batteries are drawn down but otherwise that's likely as good as it gets. Get a real external regulator or live with the output you are getting.
Thanks Bob for the info. This may be a silly question but why am I only getting 8-10 amps from a 50 amp alternator?

Also, where can I get a good external regulator? Any good brands to suggest?
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Old 07-28-2012, 08:06 PM   #10
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Its a function of the intended usage. Internally regulated alternators are typically used on over the road trucks/cars where they're only called on to replenish the small drawdown on the batteries during starting and keep the lights turned on. So they're a compromise solution - not too high a voltage so they don't boil the battery dry but enough to get the battery recharged under normal usage.

An external 3-stage regulator can control the alternator to match a more aggressive charge regime. I use a Balmar 614 on Gray Hawk. There are other suppliers but that one seems to be well respected. Ultimately the answer to your question is the same answer for most things in this world - money. A little bit of silica inside the alternator is a lot cheaper than an external unit with more robust circuitry and capabilities.
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Old 07-29-2012, 02:25 AM   #11
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Certainly dirty, bad connections can and will cause problems. And there is the question as to which regulator (if there are two) is running things but the fact you are seeing only 12.9 volts might also explain why you are only seeing 8-10 amps. Is there a voltage adjustment on the regulator? Such as what be used to adjust the voltage for various types of batteries?
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Old 07-29-2012, 06:46 AM   #12
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Just to check: at what rpm are you only seeing 8-10A ? Most alternators don't start to work until they are more like 1400rpm...
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Old 07-29-2012, 07:09 AM   #13
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I run the engine anywhere between 1600 and 1900. I will double check all the connections.

I also suspect the way things are wired. From what I can see, the wire going out from the alternator goes to the amp meter on the lower instrument panel, then to the amp meter on the flybridge before going to the electric panel positive bus bar to feed the battery. I'm guessing I'm loosing a lot of voltage with such a long path to the battery. I should probably just hook the alternator directly to the battery selector switch and see if I gain anything by doing that. The amp meters on the instrument panels are pretty much useless anyway, especially now that I have a battery monitor.
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Old 07-29-2012, 08:08 AM   #14
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It would certainly be unusual for the alternator to be wired to amp meters in series before getting to the batteries...are you sure there isn't a shunt involved?? In any case, I agree with Bob at post #10....on boats like ours, alternators should be externally regulated to optimize their charging. Take the alternator off the engine (easy job) and along to your local automative electrical shop. They can bench test it and if it is fine, at the same time they can remove its internal regulator and wire it ready to take an external, programmable regulator. Like Bob, I'd recommend a Balmar unit. Even the cheapest of these can be programmed for the battery type you have (and you can re-program it if you change battery technology in the future). You will be amazed at how much faster your batteries are re-charged.
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Old 07-30-2012, 06:12 AM   #15
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"It would certainly be unusual for the alternator to be wired to amp meters in series before getting to the batteries...are you sure there isn't a shunt involved??

55A car alt will seldom use a shunt.

My question is the wire that runs from the alt FAT enough to handle what sounds like 25 ft and 55A? #6 would be nice tho #4 would be better.
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Old 07-30-2012, 07:37 AM   #16
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"
My question is the wire that runs from the alt FAT enough to handle what sounds like 25 ft and 55A? #6 would be nice tho #4 would be better.
it's one of my concerns all well. Looks like it's a #10.
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Old 07-31-2012, 02:04 AM   #17
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25' of #10 will definitely produce a voltage drop. A run from the alternator to the lower helm station to the upper helm station and back to the batteries may be in the 40' range, even worse.
You can check for undersized wires or corroded terminals by checking the voltage at the alternator terminal and comparing it to the voltage at the batteries. Any appreciable difference indicates a need for a larger wire size or cleaning all the connections in the run.
One way to approach the issue would be to run a heavy (#4 or #6) wire directly from the alternator to the batteries, retain the wiring to the helm stations, and change the helm station ammeters for voltmeters wired appropriately.
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Old 07-31-2012, 06:40 AM   #18
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A Shunt is cheap , so might cost less and do less damage than rewiring with real wire.

My favorite is a shunt(in a SOC meter) with a dash Volt meter .

The alt output should be run to the starter feed , and the volt meter should read from there.

When starting you can monitor the actual ,at the starter voltage ,

and the starter feed wiring is always big enough to send a lpuny 50-150a BACK TO THE BATT SET.

10+V = on cranking , fine, about 14V charging , fine.

Use a SOC meter to check the charge amps , and tell when the house is full, done.



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Old 08-29-2012, 04:15 PM   #19
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Thought I would update this post to let you know how I solved the issue.

After further investigation, I came to the conclusion that the wire coming out of the alternator was indeed going to the lower helm amp meter than to the upper one before coming back to the electric panel selector switch. I got rid of the external regulator and it didn't change a thing (so that thing was totally useless). Next, I unplugged the wire from the alternator and ran a new #8 wire directly from the alternator to the positive bus bar right besides my batteries (about 10 feet). The results? On start up I got around 35 amps for a few seconds than slowly going down to stabilize around 15 (my batteries were almost full). As for voltage, it was at 13.8. Before, I got about 10 amps on start up stabilizing at around 6 and the voltage never got higher than 12.8! Now this is just from a few minutes of testing at the dock, I have yet to go out for a weekend and see what happens but I think I solved my problem for the price of a short piece of wire.
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Old 08-29-2012, 04:32 PM   #20
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Thumbs up

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Thought I would update this post to let you know how I solved the issue.

After further investigation, I came to the conclusion that the wire coming out of the alternator was indeed going to the lower helm amp meter than to the upper one before coming back to the electric panel selector switch. I got rid of the external regulator and it didn't change a thing (so that thing was totally useless). Next, I unplugged the wire from the alternator and ran a new #8 wire directly from the alternator to the positive bus bar right besides my batteries (about 10 feet). The results? On start up I got around 35 amps for a few seconds than slowly going down to stabilize around 15 (my batteries were almost full). As for voltage, it was at 13.8. Before, I got about 10 amps on start up stabilizing at around 6 and the voltage never got higher than 12.8! Now this is just from a few minutes of testing at the dock, I have yet to go out for a weekend and see what happens but I think I solved my problem for the price of a short piece of wire.
Well done
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