How do I MEASURE Alternator Output.

I know about checking battery voltage and then running the motor to see that the Alternator is actually working, but I'm curious to know how to measure the amps being produced by the Alternator at any given time.

I have a bank of 5 AGM house batteries charged by a single alternator only Starboard Volvo. There's a Blue Seas ACR in line to serve the starting battery on that side, and a Xantrex freedom 10 inverter/charger on that bank too. I have a No. Lights 8kw genset which hasn't ben working lately... More on that later.

A bit of history....

At one point, I ran the house batteries down quite low. Low enough that I got a warning of low voltage from the display on the VHF while I was out at sea. I believe that the switch for the ACR was in the off position. I can't be sure. I kicked on the generator and got them back up, but in an odd coincidence, the genset suffered a mechanical catastrophe. Luckily, we got to shore, where we found a blown 150 amp fuse between the ACR and the house bank. Replaced that one, charged up and made it home without the genset, but the Xantrex remote was reading 12.0v for the entire three day trip. So, the problem seems to be that the alternator is charging, but after a couple hours under way, the house bank gets down to 12-volts just hangs there. They don't drop real low, but they never get up to 13-13.5 that I would like. Even when they are connected to the shore power the Xantrex can only get them up to about 13. Maybe that's not a problem, but it seems weird that they run down to a certain point and then kinda hang like that forever.

Quickest way to measure amps will be with a clamp style meter.

Have you a copy of Nigel Calders "Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems" Extensive troubleshooting guides in there

Are you sure your batteries in question are good?? Charger/alternator will not charge bad batteries. You'll get just a surface charge and then they will stop charging.

Take a look at this recent post in this section "A path to redemption for an electrical idiot"
There is a link to a PDF of "Boatowner's Illutrated Electrical Handbook" that has good sections on batteries & alternators along with troubleshooting guides.

Are there any diode type isolators in the charging circuits?

One surefire way to confirm your alternator output is with a State of Charge (SOC) meter. Mine monitors two banks for voltage and one bank for amps in/out and AH remaining. My house bank get the full monitoring and voltage-only on the start battery. It's enough on the start battery to see that it's getting alternator charging and to spot check the voltage during anchoring.

Ammeter

One of the most useful pieces of equipment I've owned has been a clamp on DC ammeter. You can buy one from sears for about $60. Extech also make a good cheap one. I have owned both over the years and they have saved me many headaches. Just clamp on a wire and it will show the amperage going down the wire. JUST MAKE SURE it's a DC NOT AC clamp on meter!

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.

I'm hoping someone can either corroborate or correct me on this. I definitely have much to learn with regards to electric systems.

1. Batteries not getting past 12V for three days while running without the genset. Sounds to me either the engine alternator is too small to handle boats load AND charge or there's an issue with one of the batteries.

2. Batteries not fully charging under shore power point to either a problem with the batteries themselves or the charger either perhaps being incorrectly setup.

One thing may be important that is unknown is where are these measurements being taken. They could be measured at the charger, at the battey or someplace else such as at a bus. It could partly be a voltage drop issue caused by a cable being sized wrong.

In any event load testing the batteries sounds like a solid first step.

Having recently moved from the sailing side, the difference in electrical system complexity is a learning curve for me. Any critique of my thoughts would help me learn and maybe the OP troubleshoot.

No Mast said:

I'm hoping someone can either corroborate or correct me on this. I definitely have much to learn with regards to electric systems.

1. Batteries not getting past 12V for three days while running without the genset. Sounds to me either the engine alternator is too small to handle boats load AND charge or there's an issue with one of the batteries.

2. Batteries not fully charging under shore power point to either a problem with the batteries themselves or the charger either perhaps being incorrectly setup.

One thing may be important that is unknown is where are these measurements being taken. They could be measured at the charger, at the battey or someplace else such as at a bus. It could partly be a voltage drop issue caused by a cable being sized wrong.

In any event load testing the batteries sounds like a solid first step.

Having recently moved from the sailing side, the difference in electrical system complexity is a learning curve for me. Any critique of my thoughts would help me learn and maybe the OP troubleshoot.

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Yea, NoMast, I had the same thoughts, which is why I originally asked about measuring Alternator output. I have been testing the batteries both from the remote, which reads the charge from the xantrex unit, and also with a multi meter at the batteries directly. I recently tried charging them for 24 hours with no loads, disconnecting them from each other, and testing them individually with the full charge and 12 hours later - still completely disconnected. No one battery showed a significant loss of charge, leading me to believe that they are probably okay.

The entire system, is new within a couple of years, and the wire sizes, fuse sizes, etc are all correct. It was done by a certified electrician who did it very much by the book.

At this point, I think load testing the batteries and taking the alternator in to the genius is the best bet. Im still going to buy or borrow a clamp type meter and see what that tells me before I surrender to the professionals though.

Isn't a battery monitor sufficient?

Weather a battery is charged is best done with a hydrometer , although a SOC meter will work.

Just looking at voltage will not tell the state of the battery , only weather it is being charged.

Sounds like you ran the batts to low and now one or more cells is shorted so the bank will not charge.

Low cost check is a portable charger , disconnect the bat from the boats electrics and charge over night.

13.5 V at charge finish , 12.8 sitting disconnected after a day or two, is what you need. Check them all, one at a time.

FF said:

Weather a battery is charged is best done with a hydrometer

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He has AGM batteries I believe. Which are sealed. So that option is out.

To the OP, is your charging system properly tuned for AGM batteries? The higher fix float voltage used with flooded batteries can shorten the life of AGMs.

From what I remember, to properly test these batteries in this circumstance the open circuit test already performed is insufficient to determine the batteries are fine. What is needed is either a load test or a capacity test on them.

Another question also is when your batteries are charging have you monitored their temperature? At the posts?

Markpierce: I'm reading that AMP hr meters are "incapable of accurately reflecting this ever changing efficiency factor and need some form of periodic recalibration to bring them back in line with the actual state of charge of the Battery. Between calibrations the meter will tend to become less and less in sync with the battery's state of charge." - Nigel Calder
-- news to me

No Mast said:

Markpierce: I'm reading that AMP hr meters are "incapable of accurately reflecting this ever changing efficiency factor and need some form of periodic recalibration to bring them back in line with the actual state of charge of the Battery. Between calibrations the meter will tend to become less and less in sync with the battery's state of charge." - Nigel Calder
-- news to me

Click to expand...

I've done some reading on this. Review the Balmar Smartgauge. Seems to be the solution to accurate SOC with no need for calibration:

Smart Gauge Battery Monitoring Unit Photo Gallery by Compass Marine How To at pbase.com

Heron said:

I've done some reading on this. Review the Balmar Smartgauge. Seems to be the solution to accurate SOC with no need for calibration:

Smart Gauge Battery Monitoring Unit Photo Gallery by Compass Marine How To at pbase.com

Click to expand...

The Smart Gauge only gives you "voltage" data .......no amp values.

I have a Victron for "Amps" and a Smart Gauge for "Volts".

Codger2 said:

The Smart Gauge only gives you "voltage" data .......no amp values.

Click to expand...

No it doesn't...But seems the most accurate gauge available for measuring SOC which was what I was referencing in the quote in my post..Like a gas gauge for your housebank..

As you mention, having both will give you the most info..

[QUOTE
As you mention, having both will give you the most info..[/QUOTE]

Although the Victron will show a "Voltage" value, it often is not accurate. It does show you amps in, amps out and total amps consumed The synchonization for the Victron can be done by simply holding the + & - buttons simultaneously for 3 seconds.

The Smart Gauge, as Steve has mentioned, does give you accurate "Voltage" values but no amp info. No synchronization is necessary with the Smart Gauge.

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 like the simple % SOC feature of the Balmar and it's accuracy....when it hits 50% on your primary housebank, time to recharge or run the risk of shortening battery life and the beer getting warm!
My boat has very simple systems...Refrigerator and lighting so I know how long I can hang on the hook before I need to re-charge the system.
For best battery life don't drop below 50% before recharging...

Here are some relative Voltages VS. SOC. From the reading I've done, the "Gel" scale is pretty close to AGM numbers..

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.

bayview said:

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.

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I did that, and they all tested okay.

Bay Pelican said:

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.

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Got any pictures, BP?

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

Lutarious said:

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.

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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.

Lutarious said:

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.

Click to expand...

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.)

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.

"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?

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


Jim
Sent from my iPad using Trawler Forum

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.

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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