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Old 01-10-2015, 11:02 AM   #21
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Originally Posted by bayview View Post
If you cant measure specific gravity uncouple all batts wait 24 hours and measure voltage. The one that reads 10.5 volts or so is bad and draining charge.
I did that, and they all tested okay.
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Old 01-10-2015, 11:05 AM   #22
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Originally Posted by Bay Pelican View Post
Installed in line ammeters on my alternators so that I can watch the output. Very useful as the engines vary the output depending on their rpm. Also gives me an immediate gauge if anything is going wrong.

Got any pictures, BP?
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Old 01-10-2015, 11:05 AM   #23
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You may have a popped diode or two in your alternator. I would remove it and have it checked for full output at a good automotive rebuilder (not Autozone) or check it yourself with a load tester. You will want to load test your batteries anyway to discover their condition too.
Having an ammeter can tell you may things about your alternator but it's showing a partial output could mean that it is not capable of full output, that the batteries don't need full output, or that the batteries can't take full output. That's what you have to sort out here IMHO
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Old 01-10-2015, 11:10 AM   #24
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Does anyone know of a "real-time" alternator monitor that would show me, at a glance, what my alternator output is (amps)? In combination with an accurate SOC (volts), it seems like it would be useful to know.
In the old days we called these (dash mounted gauges) "Ammeters".....
http://en.wikipedia.org/wiki/Ammeter

Used to be quite common...Not so much anymore having been supplanted on most cars and boats with a simple voltmeter. Higher end panels incorporate these though. Easy enough to add for basic monitoring of either AC or DC..

Some of the simpler and less expensive gauges available here:
http://search.defender.com/?expression=ammeter&s=1
Many will require adding a shunt.
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Old 01-10-2015, 11:56 AM   #25
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Originally Posted by Lutarious View Post
Does anyone know of a "real-time" alternator monitor that would show me, at a glance, what my alternator output is (amps)? In combination with an accurate SOC (volts), it seems like it would be useful to know.
I know exactly what you are asking and will try (again) to answer that exact question. (Several years ago I had the very same question.)

If you want to know (in real time) what your amps coming from the alternator are, the Victron 602s will tell you that at a glance. Just toggle the + or - button to display what you want to know. If it's an accurate SOC (volts) you desire, the Smart Gauge will tell you that but won't tell you anything about amps. The Victron will also show an SOC value (Volts) but it may be inaccurate. The Smart Gauge is accurate. That is why I have both!

Note in the photo below the difference in values between the Victron and the Smart gauge. They are both showing the SOC for my starter batts. The Smart Gauge value, however, is the most accurate of the two! If I wanted to see incoming amps from the alternator, I would toggle (+ or -) the Victron to show incoming amps & leave the Smart Gauge set on either House batts or starter batts. These two gauges working independently of one another will show you just about anything you want to know about your boat's electrical system. There are many SOC devices on the market but IMO these two tell me anything I want to know about what's going on (electrically) with my boat. (With accuracy.)
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Old 01-10-2015, 12:32 PM   #26
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I have a simple voltmeter on the bridge. I know from the voltage how well charged the batteries are. I also skow that the amps are being adjusted appropriately. This isn't high science. all the SOC meters wont tell you a thing unless they are hooked up individually to each battery. Furtermore measuring volts just like SG is really only accurate after the batteries rest for many hours.


Measuring amps in and amps out is like measuring fuel in and fuel out to a tank that is continuously changing size in an unknown manner.


A simple volt meter will tell you all you really need to know.
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Old 01-10-2015, 01:43 PM   #27
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"These two gauges working independently of one another will show you just about anything you want to know about your boat's electrical system. There are many SOC devices on the market but IMO these two tell me anything I want to know about what's going on (electrically) with my boat. (With accuracy."

Will it show exactly the amperage the alternator is putting out at any given moment maybe, but more to Latarious' question, is the alternator capable of it's rated output against a full load? and are his batteries capable of taking the full output if available?
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Old 01-10-2015, 01:59 PM   #28
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How do I MEASURE Alternator Output.

I phoned Balmar about the installation of the Smart Gauge. They emphasized the Smart Gauge MUST be wired directly to the house bank batteries, not to the buss bar. This would prove difficult in my situation as the house bank is held in two boxes that are cabled as one bank at the buss bar. Balmar confirmed the wiring of the Smart Gauge would be problematic in my situation and recommended that I stay with the Magnum Energy SOC units when I install the Magnum Energy inverter charger.

The fellow with Compass Marine explains why Amp hour counters are problematic to calibrate. It really is worth a careful read...

http://www.pbase.com/mainecruising/smart_gauge


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Old 01-10-2015, 04:12 PM   #29
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There is good and bad info in this thread...without getting into details...I suggest a lot of external reading before sifting through threads like this to get to the pearls.

I have the Balmar Smart Gauge ....it even needs a certain amount of tweaking and correct installation to get the best info like JDCAVE posted.
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Old 01-10-2015, 09:33 PM   #30
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Lutarious,
I would really suggest reading the electrical book I posted about at the beginning of this thread, it will be very helpful and should let you get to the bottom of this, or at least know for sure where the problem isn't.

If all you want to do is test the alternator output use a clamp on meter on the cable.

Lastly, the test you performed on your batteries only tells you that the active material remaining in the cells is viable. It says nothing about how much of it is left within a wide range. You need a load test or a capacity test. Before you can claim that the batteries are ok. Also you said that you let them sit for 24 hours, the manual states that for AGMs they should sit for 48 or more for the open circuit test you performed.
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Old 01-10-2015, 09:38 PM   #31
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Ok let's make this really simple, you need a shunt and ammeter TO measure JUST alt output.
https://www.bluesea.com/products/823..._-_500_to_500A

The link below has a shunt and meter.
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Old 01-10-2015, 10:19 PM   #32
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Ok let's make this really simple, you need a shunt and ammeter TO measure JUST alt output.

https://www.bluesea.com/products/823..._-_500_to_500A



The link below has a shunt and meter.

Finally😎
The reason you seldom see an analog amp meter in your gauges is that old school ampmeter requires the "work" being performed downstream to pass THROUGH the gauge. Imagine the potential voltage loss on a circuit that routes to your flybridge.
Using a shunt gives you a value of the amps passing it, and a low voltage signal is sent to the meter that partners with it. A volt meter doesn't require large amounts of amperage to get a reading.

Our techs occasionally use an old school meter, with a short wire and clamp on the + and- terminals. I built them, (then dipped the rear of the rig in the plastic stuff you can get for dipping plier handles in for insulation) to use on the hard to solve charging problems you occasionally see. You remove the large "battery" wire from the rear of the alternator, then clip the amp meter "in line" to see the amps produced and confirm no loss if running headlights, etc.



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Old 01-11-2015, 12:58 AM   #33
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Measuring amps in and amps out is like measuring fuel in and fuel out to a tank that is continuously changing size in an unknown manner.


A simple volt meter will tell you all you really need to know.
Actually, it doesn't!
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Old 01-11-2015, 01:01 AM   #34
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Will it show exactly the amperage the alternator is putting out at any given moment (yes!)maybe, but more to Latarious' question, is the alternator capable of it's rated output against a full load? and are his batteries capable of taking the full output if available?
He didn't ask that.
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Old 01-11-2015, 12:40 PM   #35
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Just a thought the last 2 boats I've had I have built a hard top bimini on the flybridge loaded it with solar panels. Battery power no problem. on St Christopher (where we spend 6 months a year) we have 4x235watt panels providing over a KW per hour good day. We run a household stand up fridge, a wine fridge continious plus lights music etc. My wife cooks with 110vac skillets for lunch etc. Wonderful feeling to watch 40-60 amps going in while your sipping cool wine on the bridge, with no generator running!
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Old 01-11-2015, 01:03 PM   #36
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Wonderful feeling to watch 40-60 amps going in while your sipping cool wine on the bridge, with no generator running!
What device do you monitor the amps with?
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Old 01-11-2015, 01:27 PM   #37
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To the OP: There is a lot of stuff posted, most of it pretty good, but it is a lot to digest.

To make things simple, get a portable digital voltmeter and put probes right on battery terminals. Turn off any charger or inverter that might be charging batts. Start main engine up and rev to say 1500. Look at meter reading. It should start at 12-13v depending on where batts were prior to start. Volts should slowly climb as alt does its thing. Should top out in the mid 14's and stabilize.

Then go to main engine and check temp of alternator case. Cold means it is dead. Blazing hot means it has a problem or is overloaded. Warm to medium hot, say 150-200F or so, and volts 14.2-14.5 at batts means all is well.

These are the first checks I would do if I was hired to troubleshoot your boat. Next steps would be based on findings from above.
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Old 01-11-2015, 02:06 PM   #38
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SKI summed initial testing nicely.

I will post my tome regardless.
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I’ll try to answer some of your questions without consideration of various SOC systems.
A question or so first:
- Did your system work before?
-Is this problem only recent or have you had some trouble before?
-What size is the alternator? Amperage output? What type and mfgr.?
-IS the alternator controlled by an internal regulator or has the alternator been fitted to be controlled by an external 3 stage regulator?
-How do you use the boat and has that use pattern changed recently?

If you want to monitor the actual alternator output in amperage you must install an ammeter in the alternator output line only. It is not practical nor is it good practice or safe to install an inline ammeter permanently. Rather what is used is called a SHUNT type ammeter. The shunt is a highly accurate, very low resistance resistor which at max ammeter capacity will produce a 50mV drop which the ammeter [really a voltmeter scaled to read out amps] then reads. They must be suitable for each other, ie. a set. Between the shunt and the ammeter gauge, quite small wires are used, usually 16AWG. The ammeter can be placed almost anywhere, on the panel or close by since it does not usually require constant monitoring.

For battery condition, ie. Charge state, that is where a SOC meter comes into play for continuous monitoring. I will not get into the argument about which mfg. or type is best. That won’t help now until your problem is repaired and until the problem is resolved and should be ignored at the risk of clouding YOUR issue.

The ‘test’ of your batteries that you did, terminal voltage after a charge and rest period, will tell you ONLY that the batteries are in fact charged. That test though cannot tell you about the actual battery condition. Even a battery with a failing cell, note: not dead, will show a DMM near perfect voltage. The reason is the DMM needs a tiny current to make it read, on the order of 1 or 2 micro amps. That current is so tiny that it will not affect the battery readout as even the failing cell can produce that level of current. At some point it will show but then almost always other troubles have shown up.

To truly test and assess a sealed battery condition, AGM or GEL, a proper LOAD test must be done or test by the use of a Conductance meter of good quality.

I asked about the alternator since it could simply be too small. It may have been OK for running under light load conditions and/or light recharge conditions. But if your running loads are heavy , the batteries are down substantially, and the alternator is not big enough, once the needs of the running loads are met there may be very little current going to battery recharge. In cases like this many, many, many hours of running will be needed and possible shutting off some loads so less current goes to the loads and more to the batteries.
This situation is often not of great importance if you are basically weekenders and then go back and plug the boat in. However, if you have changed your habits and are multi week holidaying or serious cruising then what was ok for week ends becomes a real problem for longer term cruising where you depend upon the alternator to do a serious recharge of the batteries and handle the running loads.

If the alternator is damaged it cannot produce what it should. That’s why I asked about the alt. capacity AND if the system worked ok before. There are several ways that can happen. Failing diodes, failing regulator or alternator damage to the windings from overheating.
Failing modes:
-diodes can fail open meaning no current from that diode which can actually cause a substantial reduction or current.
-diodes can fail closed/shorted meaning the same as above, allow some AC through which is bad, and leak backward when the alternator is off.
-brushes can get sticky or worn out causing poor, intermittent or no output.
-connections inside can come loose or break.

The alternator should be pulled off and taken to a good alternator rebuild and test shop where they can actually load it up and make it work for a while to also test for heating problems.

Alternator types also can come into play. ALL alternators lose output when hot, some by as much as 25% which may produce inadequate performance. Some alt. are built better than a standard alt. to survive without burning up. They can run hotter, have better fans for better cooling and are rated more conservatively so they can run for long periods and survive.

But first find out if the batteries are good, and the alternator that you have is good.

If what you now have is actually working as it should then you may need to assess the entire system for your current useage. A lot of people do not understand that the batteries get recharged by whatever current is LEFT OVER after running all the other loads.:
-Electronics – vhf, plotter[s], computer, refridgerator, freezer, gauges, stereo, radar, AIS ANYTHING that is turned on while running.
-Inverter/charger – will draw current to run itself unless truly turned off. If on standby it still needs some current.
-Engine – yes that alternator itself will possibly use some of its own produced current especially if controlled by a 3 stage aftermarket regulator. An internal reg. will steal current but you won’t see it at the output wire as it is gone before that. Any electronic control for the engine require power. Fuel solenoid energized to run.
-Lighting, heating. Even if run from the main engine or a generator the controls often draw off your battery system which means the alternator when running.
-Even your ACR/combiner uses some current to operate., for the sense function AND to operate the relay.
-When the ACR operates what current was going to the house batteries may be split even further.
-Literally any electric item that is NOT run ONLY by the generator.

If the alternator is not a H.D. unit and not big enough then what actually gets to the batteries may be far less than you think.



Your steps should be:
Pay attention to Ski's suggestions first and report back.

A real load test of the batteries

An alternator check, [Brooksie]

If all the above checks out then an assessment of your system for suitability/capacity may be needed.

Consider the alt. output ammeter and/or SOC meters only later. They would be a good addition but should not take your attention off the real problem untill that is solved.
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Old 01-11-2015, 02:37 PM   #39
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Wow, how to keep this simple. Fundamentals I guess. First, Nigel Calder wrote about the best book out there that talks both about fundamentals but specifically in the context of boats. There are many other things accurate things you could read, but none I know of that put it more succinctly.

There are two fundamental measurements you can take on an alternators output. They are voltage and amperage. Knowing one does not tell you the other. Knowing the voltage won't tell you conclusively whether the alternator is operating fully as a couple blown diodes could be limiting its output while the voltage looks normal. I also suspect you may have a partially blown alternator.

Using a multimeter to check voltage is easy as you can just put it across the positive and negative terminals. While most multimeters also measure current (amperage), there are two issues that prevent you from using it directly. The first is that they must be put inline to the circuit, meaning you have to alter the circuit, not just touch two terminals. For example, you might need to unbolt the positive lead and attach it to one terminal of the meter, then wire the other side of the meter back to where the positive terminal had been bolted. The meter would be literally in the circuit. However, the problem with this is that your average multimeter is only rated to about 10 amps. Even if you take the time to wire it correctly, you would blow it's fuse or destroy the meter by trying to measure an alternators output that may be 50 to a hundred amps or more.

There are two primary ways to handle the high current issue. The easiest is to use a clamp style meter as you can simply clamp them around a lead and don't have to break the circuit to insert them. A bit more cost to buy, but a good tool to have. The second method is to purchase a shunt. A shunt gets inserted into the circuit you want to measure as described, but is sized to handle the full current flow. The meter then is attached to the shunt and can be used to measure the current. Permanent current measuring devices typically use a shunt.

If you want a more permanent installed current meter, then you also have to decide where to install one. Typically the most useful location is to insert a shunt as the first device after your batteries, this way you see the total amps being consumed by the boat. This can effectively be used to immediately see the output of an alternator, but there is one catch. Let's say your boat is consuming 20 amps of load from your batteries. Next, we start the engine and the alternator is putting out 80 amps into the batteries. Because we located the shunt at the battery, we see the net of the two competing loads, or 80 amps in minus the 20 being consumed would have the current measurement as 60 amps. Since you knew the loads being consumed before starting the alternator, it's not really a problem extrapolating what the alternator is really doing. Of course, you can also intentionally shut nearly all circuits off to get a more pure alternator reading. Having a centrally located shunt that helps you see both loads and charging currents is a good strategy.

You could of course place a shunt inline to the alternator output as well. The only downside is the time/cost/complexity of doing so. Since an extrapolation is both easy and effective, most don't do this.

Who makes these current meters with shunts. Almost everyone. Now that you know what it is, just review devices for current measuring capability and see if they ship with a shunt. I like the Victron battery meters, but there are many others.

So, to summarize the most easy way to quickly check an alternators output, buy a clamp meter. For a permanent install, highly recommended, install a shunt in a strategic location.

Lastly, remember the cheapest option is to simply remove the alternator and have it bench tested in isolation for free almost anywhere.
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Old 01-11-2015, 03:27 PM   #40
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simple things made complicated. Watch your voltmeter if it rises the batteries are getting charged if not they are not and the cause is a bad battery or bad alternator, most likely battery.


If the batteries have started to use a lot of water they are nearing end of life. If the voltmeter reads 12V or less with alternator off they are bad or very discharged.


In all my year of boating watching the voltmeter, and doing an occasional SG test, told me what more exotic and expensive stuff merely confirmed.
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