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Old 02-19-2016, 05:21 PM
JAcob Nagle JAcob Nagle is offline
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Alternator trouble shooting

Im having charging issue with my alternator. Its the api 55amp/14.5v sold on this site. I don,t understand why I cant have it output 14.5v when running the engine in neutral at anchor. How much rpm should it be going for me to reach the ideal charging ouptut. If it runs in neutral at 1800 rpm it goes to maybe 13.8. Is it possible to reach 14 v at close to iddle speed or do I have rev the engine that high while i charge my battery.

Comming down the icw i never had the probleme because we where motoring a lot. Now we are anchor in the exumas struggeling to keep the battery up. Its a small bank of 2 west marine agm groupe 27 92ah bought a month ago.

What am i missing.?
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Old 02-19-2016, 09:22 PM
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hanleyclifford hanleyclifford is offline
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Since you are at anchor it is not likely there is any shop assistance nearby where you could get an output test on the alternator. I suggest checking all your connections especially the negative path from the alternator case to the battery bank. IIRC that alternator has only one wire, the big one. Where do you have it connected? Also, where are you reading voltage?
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Old 02-19-2016, 09:36 PM
JAcob Nagle JAcob Nagle is offline
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I had it test on a bench in a garage in nassau. It tested perfectly , went up to 14.2 and stayed there.

Output cable goes to starter soleinoid, excitation to coil. I added a strapped from cassing of alternator to main ground, recheck all connection.

One local mecanician came check to check out the system and when he was checking things over he was reading 14.5v on his voltmeter even at iddle. I thought everything was fine then Next day i monitor it and get only 13.2 at iddle and up to 13.8 if i rev up the engine at half throttle. I tripple check with 3 different voltmeter and get same reading.

Reading output at alternator directly
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Old 02-19-2016, 09:51 PM
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Question

When you say "main ground" does that mean the engine block? What sort of cable do you have from the engine block to the battery itself? Can you remember where the mechanic who read 14.5 v had his negative probe or clip? Was he grounding his meter in the same place as you grounded your meter?
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Old 02-19-2016, 09:52 PM
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try running the output directly to the house bank pos. i have the same alternator and thats wheremine is.
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Old 02-19-2016, 09:57 PM
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Originally Posted by Boat View Post
try running the output directly to the house bank pos. i have the same alternator and thats wheremine is.
Interesting thought. The solenoid terminal is the other end of the main positive feed so you must be suggesting there is resistance between solenoid + and batt +?
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Old 02-19-2016, 09:58 PM
JAcob Nagle JAcob Nagle is offline
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When i say main ground i mean boat ground that connects to engine block.

When he was testing it i vaguely remembers, maybe he was probing the ground directly to the battery and the + to the output, i will re check tommorow. If you put outpu directly to battery do you have to fuse it?
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Old 02-19-2016, 10:00 PM
JAcob Nagle JAcob Nagle is offline
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So just to answer original question, alternator should output 14.5 at close to iddle speed? Correct?
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Old 02-19-2016, 10:12 PM
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Quote:
Originally Posted by JAcob Nagle View Post
I had it test on a bench in a garage in nassau. It tested perfectly , went up to 14.2 and stayed there.

Output cable goes to starter soleinoid, excitation to coil. I added a strapped from cassing of alternator to main ground, recheck all connection.

One local mecanician came check to check out the system and when he was checking things over he was reading 14.5v on his voltmeter even at iddle. I thought everything was fine then Next day i monitor it and get only 13.2 at iddle and up to 13.8 if i rev up the engine at half throttle. I tripple check with 3 different voltmeter and get same reading.

Reading output at alternator directly
If your output goes to the solenoid battery terminal and it is also sensing, and meanwhile your excitation wire goes to coil + and you have a resistor in front of coil + I can see a potential problem - not enough "excitation" to satisfy the field requirements. Make sure the excitation wire does not have resistance in front of it.
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Old 02-19-2016, 10:14 PM
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Quote:
Originally Posted by JAcob Nagle View Post
So just to answer original question, alternator should output 14.5 at close to iddle speed? Correct?
Yes, at least just above idle unless some big loads are in use.
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Old 02-19-2016, 10:22 PM
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We could use some input from Neil on this one.
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Old 02-19-2016, 11:27 PM
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That depends.
14.5 volts would destroy my batteries, so no way would I set my regulator that high.
The other issue is the A4 is a poor engine to charge batteries with. The alternator pully is pretty small, so the alternator RPMs are lower than most other engines. You have little power available at idle, so unless the batteries are topped off and there are no loads turned on, you are very unlikely to hit your voltage target at idle.
Make SURE you have a good ground connection. I have a seperate 4 gauge ground wire going from my alternator to the main ground bus. I use 4 gauge and 2 gauge wire from the alternator to the battery as well.
Can you post any photos and diagrams of how you are set up?
Here is what I have:



Quote:
Originally Posted by JAcob Nagle View Post
So just to answer original question, alternator should output 14.5 at close to iddle speed? Correct?

Last edited by joe_db; 02-19-2016 at 11:34 PM.
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Old 02-20-2016, 12:18 AM
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The first question I have is why are you reading voltages different than the mechanic even with multiple testers? I suspect poor tester probe technique. Wherever you place your test probes they should be "drilled in" to minimize or eliminate paint/rust/oxidation/corrosion resistance on the metal surface. Push in the point of the probe with gusto while twisting it. This is especially important on a boat.

Secondly, I'd advise against charging at idle even if the alternator is producing at such a low RPM. Charging at idle doesn't provide much air flow from the cooling fan and if your batteries are discharged deeply (sounds like they are) your alternator will be working pretty hard with very little cooling. According to Dan Pires of Lewco Electric in Newport Beach, internal alternator temps of around 200°F begin to damage the insulation on internal windings and the death spiral ensues.

Finally, AGM's do not fare well with fixed point charging. Here is an excerpt from a bulletin by Cadex Electronics http://batteryuniversity.com/learn/a..._glass_mat_agm
Quote:
As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (14.4V) and higher is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (13.5 ~ 13.8V), summer temperatures may require lower voltages. Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive.
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Last edited by ndutton; 02-20-2016 at 09:18 AM. Reason: added link to Lewco Electric
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  #14   IP: 72.194.223.130
Old 02-20-2016, 12:46 AM
JOHN COOKSON JOHN COOKSON is offline
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Quote:
Originally Posted by JAcob Nagle View Post
One local mecanician came check to check out the system and when he was checking things over he was reading 14.5v on his voltmeter even at iddle. I thought everything was fine then Next day i monitor it and get only 13.2 at iddle and up to 13.8 if i rev up the engine at half throttle. I tripple check with 3 different voltmeter and get same reading.
Fresh new batteries in each of the volt meters I presume?

TRUE GRIT
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Old 02-20-2016, 06:43 AM
JAcob Nagle JAcob Nagle is offline
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Ok will trouble shoot a lot today.

But to answer some of the question, batterry are discharged a lot this morning, 12.02 V.

I had replace battery in the voltmeter and I am scratching the paint of the alternator when probing ground.

Some question that i will try to answer while trouble shooting today.

Is there resistance at the excitation wire. What is the best way to test that?
There is a ballast resistor connected between the + side of the coil and my fresh water cooling pump. Can it be the cause?

I will try to bring the battery to a full charge see if after that the target voltage is easier to acheive. When mecano came to the boat , battery where near full charge after being plug to shore overnight.

I will also try to connect output directly to battery terminal.
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Old 02-20-2016, 09:48 AM
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While you're troubleshooting the immediate problem you may want to consider the bigger picture regarding AGM's. It takes more than simply replacing the batteries, a complete new charging system is required too. Here is a little more reference material on the subject:
http://www.knowyourparts.com/three-m...agm-batteries/

I tried AGM's a while back, did not make any charging system changes from my original flooded cell system (fixed voltage @ 14.0V). My experience was poor at best. After researching things a little more I decided the benefit of AGM's was not worth the trouble and expense of changing the entire charging system to first regain the performance of the original flooded batteries before realizing the further benefits claimed in the advertising copy. For me and my boat usage it just wasn't worth it. It took only one Catalina weekend on AGM's to reach the decision. It was an expensive lesson.

FYI, that single Catalina weekend's experience was eerily similar (dare I say exactly?) to what you reported in your opening post.
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Last edited by ndutton; 02-20-2016 at 10:24 AM. Reason: added charging voltage spec
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Old 02-20-2016, 10:36 AM
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Quote:
Originally Posted by JAcob Nagle View Post
Ok will trouble shoot a lot today.

But to answer some of the question, batterry are discharged a lot this morning, 12.02 V.

I had replace battery in the voltmeter and I am scratching the paint of the alternator when probing ground.

Some question that i will try to answer while trouble shooting today.

Is there resistance at the excitation wire. What is the best way to test that?
There is a ballast resistor connected between the + side of the coil and my fresh water cooling pump. Can it be the cause?

I will try to bring the battery to a full charge see if after that the target voltage is easier to acheive. When mecano came to the boat , battery where near full charge after being plug to shore overnight.

I will also try to connect output directly to battery terminal.
I do not like the idea of the excitation wire sharing the circuit with the ignition, let alone with the fresh water pump in the mix. Try putting that pump on a different source where it does not influence the ignition. Resistors change voltage and pumps with motors also draw down the voltage locally. Edit: Before changing anything, test your voltage at the excitation wire, hot and running thru the rpms.

Last edited by hanleyclifford; 02-20-2016 at 10:45 AM.
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Old 02-20-2016, 12:02 PM
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I used gels for years, went AGM, hated them, and went back.
One issue with AGMs on an A4 powered boat is they take a LOT of charge when low. The small alternator at low RPMs on an A4 is looking at what is close to a dead short and can't get the voltage up to the setpoint for hours when charging a big bank. BTDT
BTW - GET SOLAR!
I spend a week or two at anchor for sailing class every year and a solar panel cut my engine run times by about 2/3s

Quote:
Originally Posted by ndutton View Post
While you're troubleshooting the immediate problem you may want to consider the bigger picture regarding AGM's. It takes more than simply replacing the batteries, a complete new charging system is required too. Here is a little more reference material on the subject:
http://www.knowyourparts.com/three-m...agm-batteries/

I tried AGM's a while back, did not make any charging system changes from my original flooded cell system (fixed voltage @ 14.0V). My experience was poor at best. After researching things a little more I decided the benefit of AGM's was not worth the trouble and expense of changing the entire charging system to first regain the performance of the original flooded batteries before realizing the further benefits claimed in the advertising copy. For me and my boat usage it just wasn't worth it. It took only one Catalina weekend on AGM's to reach the decision. It was an expensive lesson.

FYI, that single Catalina weekend's experience was eerily similar (dare I say exactly?) to what you reported in your opening post.

Last edited by joe_db; 02-20-2016 at 01:51 PM.
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Old 02-20-2016, 08:32 PM
JAcob Nagle JAcob Nagle is offline
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Ok after some testing this morning, it turns out the alternator output goes up as the battery is charging, i was on the impression that it needed to go to 14V right away. So after 2 hours of charging at close to iddle speed voltage slowly rises until it stopped at 14.2v.

I checked voltage at coil and it went up along with the alternator.

So in retrospect when mecano came to my boat since battery where close to 100% the output went straight to 14.5. Dont know if it's standard? I find voltage drop between output and battery. 0.11 v. Is it normal.

Thanks for your help, battery are getting charge it just takes longer. Will wait until we are in dominicaine republic before doing any major change.

Im learning boat system as i go , unfortunatley i bought these 2 agm cause i uad a good deal. Maybe later down the road i will look at other kinds.

I also have a 130w solar next on my trouble shooting list.
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Old 02-20-2016, 09:10 PM
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A voltage differential of 1 volt between alt+ and batt+ is quite normal and acceptable, and the difference will vary a lot depending on state of charge and loads in use. BTW, as the battery charges the voltages will rise but the output (amperage) should decline. For a cruiser like you it is valuable to have both voltmeter and ammeter on line.
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Old 02-21-2016, 12:25 AM
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Jacob,

I suspect you are actually reading battery voltage rather than alternator output. Unless you have a three stage regulator, the alternator output voltage strives to remain constant. As Joe explained, the discharged battery bank is likely drawing down the system voltage even during charging due to the low internal resistance and therefore high amperage demand of the AGM's coupled with reduced alternator output (in amps) due to low RPM.

Several years ago during a regulator-ectomy and replacement by a pro shop I had them test my alternator on a dynamometer. At an arbitrary 2000 RPM my 100 amp alternator produced around 60 amps. This is an example of the reduced performance due to low RPM Joe was talking about.

Your 0.11V drop between alternator and battery is excellent. It calculates to roughly 7/10ths of 1%. Nowhere in your engine electrical system should you have greater than a 3% drop so in this portion of the circuitry you're good.
Quote:
A voltage differential of 1 volt between alt+ and batt+ is quite normal and acceptable
Uhh, no it's not. That is a 7% voltage drop, over twice the allowable 3% standard specified by the ABYC. The corrective action is a shorter wire run, larger wire gauge or both.
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Last edited by ndutton; 03-01-2016 at 12:46 AM.
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Old 02-22-2016, 07:56 AM
smosher smosher is offline
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There's a sensor input for the voltage. I connect this to my common on the AB Switch. For my installation this means the common will be at 14.2 and the
excitation, connected to the coil+ is 14.5

The Alt will monitor the sensor wire, if its left floating I believe
it would monitor the excitation wire. Which probably reduces the vdc at the battery depending on the loss in the path.

The best thing I did was to install a 20 watt solar panel, Battery is always charged.

Steve
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Old 02-22-2016, 08:16 AM
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Originally Posted by smosher View Post
There's a sensor input for the voltage. I connect this to my common on the AB Switch. For my installation this means the common will be at 14.2 and the
excitation, connected to the coil+ is 14.5

The Alt will monitor the sensor wire, if its left floating I believe
it would monitor the excitation wire. Which probably reduces the vdc at the battery depending on the loss in the path.

The best thing I did was to install a 20 watt solar panel, Battery is always charged.

Steve
Steve - Is your alternator internally regulated? Does your alternator have 3 wires - output, excitation and sense?
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Old 02-22-2016, 03:01 PM
smosher smosher is offline
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Hi Hanley, Yes Internally regulated with the sensor and output

Just the stock api 55 amp alternator.

I found this thread on wiring the alternator.

http://www.moyermarine.com/forums/ar...hp/t-4065.html
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