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Old 09-12-2012, 08:46 AM   #21
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"I still am sure an ammeter on the A/C side of my panel is a good idea for all the reason you guys have mentioned. Most especially because it's a pretty easy project that will pay dividends down the road."

Who is going to spend their cruising time observing this?
Being able to determine the current draw (and voltage) of both the AC and DC circuits on a boat would be pretty valuable if you're not one of the "turn the key and drive until it breaks" kind of people.

And as RickB pointed out, a lot like engine temperature and oil pressure gauges.
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Old 09-12-2012, 11:41 AM   #22
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OK guys, here's a little money saving trick...

The doughnut thing is called a Current Transformer, or CT.
Every CT will put out 5 amps at full load. For Example if its a 100 amp CT then 100 amps flowing through a wire going through the doughnut will equal 5 amps on the leads of the CT.
Every amp meter is really a 5 amp meter.

So, To save money...

Find a CT on ebay in the range you're looking for,IE 50 or 100 or even 200 amps.
Find an ammeter on Ebay. the amperage is irrevelant.
Make up a new ammeter "face" using whatever software you want, or buy one. Make the face match the CT you bought and space the numbers out evenly, and you're there.
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Old 09-12-2012, 01:06 PM   #23
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OK guys, here's a little money saving trick...

I'd rather spend the $31 for a 50A meter and CT and skip the hassle of taking the meter apart and kludging a homemade scale onto it.

But if you do find a dirt cheap 100:5 CT (if $6 isn't cheap enough) just run the hot lead through it twice and it becomes a 50A CT.

It's not like you are going to save $1000.
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Old 09-12-2012, 05:15 PM   #24
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I'm thinking if you can't afford a proper ammeter, you probably can't afford the electricity you're planning on measuring.

And if you try to cobble one up from spare parts, you're going to have to buy or borrow a "real" one just to make sure your cobbled meter is accurate.
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Old 09-12-2012, 05:21 PM   #25
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Wasn't the first successful airplane built from bicycle parts???

The forum is about sharing ideas...while some may not use all of them....some people do enjoy the budget ideas that are brought up here...

Not everyone stops by West Marine for coffee and parts every day....
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Old 09-12-2012, 06:00 PM   #26
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Its funny because when you order an ammeter, someone pops the plastic face off and inserts the "scale" with the numbers on it, then ships it out.

Its not using spare parts, non standard stuff, thats just how ammeters work.
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Old 09-12-2012, 06:12 PM   #27
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An ammeter is a very simple device and what someone linked to is "proper". What BlueSea has done is make something simple, complex and pricey. The $250 device I was looking at had voltage readings, high and low alarms for voltage and amperage, big LED display, and measured Hertz. I just don't need all that. I thought I did at first, but now I see it's just fluff. I am happy with $40 off eBay or $80 off Grainger.
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Old 09-13-2012, 06:40 AM   #28
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"a lot like engine temperature and oil pressure gauges. "

These are easily available with adjustable settings to trigger an alarm , so the watch stander does not need a great scan. Murphygauge.

My point is with automatic load shedding there is NO monitoring.

Usually its only the HW heater that is the problem , so a single relay and a single control wire from the Air cond makes the noisemaker load regulation automatic.

Works great at a dock with crap power.
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Old 09-13-2012, 07:23 AM   #29
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It seems that my genset (NextGen Power) wants to overheat if I load it to near capacity. It's only a 3.5KW and I need it to last (i.e. I can't afford a new one right now). I have looked at most of the usual suspects for overheating issues short of pulling off the heat exchanger.

I want to put an amp meter on the generator to monitor the load we put on it. I'd like to have a 2" round gauge to go next to my new battery monitor. Any suggestions?

Tom-
Can you access or see your house AC breaker panel from where you want to locate the amp gauge? Ours is within visual distance from our circuit breakers. If we're monitoring loads, it's when we're at anchor or at the dock and with breakers close by, I can see what I want or don't want to run.

An other source for gauges is: Manufacturer of Quality Electrical Control Panels and Assemblies
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Old 09-13-2012, 08:33 AM   #30
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An ammeter is a very simple device and what someone linked to is "proper". What BlueSea has done is make something simple, complex and pricey. The $250 device I was looking at had voltage readings, high and low alarms for voltage and amperage, big LED display, and measured Hertz. I just don't need all that. I thought I did at first, but now I see it's just fluff. I am happy with $40 off eBay or $80 off Grainger.
It's not "fluff" just because you don't need the other information. Other people may well make use of the other measurements and warnings.

If you want/need a simple ammeter, yes, buy just that, a simple ammeter. Figure your total possible current draw (in amps) and buy a meter with a range as close (but above) to that as possible.
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Old 09-13-2012, 09:57 AM   #31
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buy a meter with a range as close (but above) to that as possible.
The most accurate reading on any analog meter or gauge is in the middle third of the scale. Ideally, the "normal" reading should be at the center of the range.
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Old 09-15-2012, 10:35 AM   #32
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We have this setup from Marinetics Corp. The meters show both legs of the source selected by a separate selector switch ie: 50A shore power, 220V genset output or as shown the 110V inverter output. Works great for monitoring or switching which legs feed which devices.
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Old 09-15-2012, 11:02 AM   #33
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The most accurate reading on any analog meter or gauge is in the middle third of the scale. Ideally, the "normal" reading should be at the center of the range.
Fine, but the maximum current cannot exceed the maximum rating of the meter. For a 30 amp system, he will probably have to use a 50 amp meter and let the "normal" current fall wherever it falls. Of course, a digital meter would be best and would read accurately at any current within it's capacity.
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Old 09-16-2012, 01:34 PM   #34
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Fair enough, Ron, but I don't think absolute accuracy, like to the 1/10 of an amp, is needed.
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Old 09-16-2012, 09:03 PM   #35
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My analog 115 volt AC gauges for volts and amps are accurate. On the DC side my analog gauges read .4 volts higher than the digital gauge for the inverter. Measuring at the batteries my multi gauge tester agrees with the digital. That's what I go by. I have a 50 amp shore service that will run everything, so don't need to watch power usage too closely. The generator is 12 kw NL.

At anchor on the inverter power is when battery levels have to be watched carefully. I will probably add a SOC meter.
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Old 09-17-2012, 10:26 PM   #36
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OK, I have been checking out some state of charge (SOC) meters. With an accurate digital read out of the house battery bank is one really necessary? It seems to me that if 12.2 volts is a 50% state of charge, the object is to never let it go below that. Any ideas as to why this is not enough information?

The charger compensates for temperature variations. The plan is to upgrade the 80 amp alternator dedicated to the house bank to a small frame 120 amp unit with a 3 stage voltage regulator, or would the 80 amp with an upgraded voltage regulator be large enough? When under way about 25 amps DC is the most the inverter would use.
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Old 09-18-2012, 07:39 AM   #37
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OK, I have been checking out some state of charge (SOC) meters. With an accurate digital read out of the house battery bank is one really necessary? It seems to me that if 12.2 volts is a 50% state of charge, the object is to never let it go below that. Any ideas as to why this is not enough information?

The charger compensates for temperature variations. The plan is to upgrade the 80 amp alternator dedicated to the house bank to a small frame 120 amp unit with a 3 stage voltage regulator, or would the 80 amp with an upgraded voltage regulator be large enough? When under way about 25 amps DC is the most the inverter would use.
Don: I guess it depends on what you want to look at. Our SOC meter, in addition to DC volts, also lets us see how many amps are going in and out of the house bank. I like to monitor what our DC loads are and what is going back into the batteries from the charger or alternator.

I would would keep the 80 amp alternator and just upgrade your voltage regulator. An 80 alternator only requires a single belt. Depending on who you talk to, a 120 amp alternator may require 2. If the batteries aren't getting fully charged when motoring, then I would consider the upgraded alternator.
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Old 09-18-2012, 07:42 AM   #38
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OK, I have been checking out some state of charge (SOC) meters. With an accurate digital read out of the house battery bank is one really necessary? It seems to me that if 12.2 volts is a 50% state of charge, the object is to never let it go below that. Any ideas as to why this is not enough information?

The charger compensates for temperature variations. The plan is to upgrade the 80 amp alternator dedicated to the house bank to a small frame 120 amp unit with a 3 stage voltage regulator, or would the 80 amp with an upgraded voltage regulator be large enough? When under way about 25 amps DC is the most the inverter would use.
From my experience...the voltage reading has to be done at just the right time and with a no load condition...one where there is no inflated voltage from a recent charge....waiting for that to happen and not using any DC while waiting for it is a bit difficult when cruising.

Much like knowing the amperage of my AC electric and amount of fuel left...I prefer the old time "know what was running for about how long" and you should be able to figure the rest...not as accurate but accurate enough if you have it down pretty well.

The bottom line is neither voltage or a SOC really can tell you the health of the battery...only a load tester (I think) can.
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Old 09-18-2012, 08:36 AM   #39
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Fair enough, Ron, but I don't think absolute accuracy, like to the 1/10 of an amp, is needed.
Of course it's not for general purpose on a boat. The argument was made that an analog meter would be most accurate in the middle of its range. I think for our purposes here, the accuracy of an analog meter at any point in its range would be just fine, but if one were to try to measure loads in the one to two amp range with a 100 amp meter, it would be pretty difficult to read. That's why we have different "ranges" on most analog VOMs and that's why I made the suggestion that I made.
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Old 09-18-2012, 10:25 AM   #40
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Thanks, guys. I think the simple, inexpensive thing is the first to try. So, it will be the 3 stage voltage regulator. The 80 amp alternator is already driven by a double belt set up, so the 120 amp alternator would probably be just a bolt on addition.

Reading the battery voltage is a tricky thing. I have noticed that when there is a load of any kind on the batteries the read out will be about .2 volts lower. When only a small load the voltage read comes back up. So, I take it that the light load reading is more the true state of the batteries. The batteries have been tested under load and show as new.
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