Alternator Shunt and Meter

[Stu Jackson]

Originally Posted by a64pilot

One thing I'm curious is at what engine RPM do I have to hold for X current? I don't know, it may be that my 140 amp alternator may only be making 50 amps at 1,000 RPM, and until you measure it, how do you know?

Good research, thanks for sharing.

At the risk of repeating myself, my answer is I use my Link 2000, which is like a Victron 600 --- a NET system amp meter. If my fridge is on, whatever the AO is I just add 5A.

By doing that, I can set the rpms from idle (1000) to 1500 to 2000 and see the differences. And + or - 5A doesn't make a difference in the big scheme of things.

Unless you have an alternator specifically designed and selected for high output at low rpm, all alternators will put out a LOT more at higher rpms.

How much? I just do it with my Link.

I have a 100A alternator with a Balmar MC-612, using a Small Engine Mode switch, not belt manager, for when the bank is depleted to reduce the AO to avoid overheating the alternator. You can search on Small Engine Mode under my name, I've posted links to the concept with photos and all. 390 ah house bank, no solar.

[Dr. Sea]

[QUOTE=Stu Jackson;1926694]
I'd spring all of $150 for a Victron 600, hook it up, read net voltage or turn your fridge off to read the amp output. Why? By the time you cobble something together...

Better yet, if you know what yoru fridge draws, then the math is simple.

I do this all the time with our Link 2000. QUOTE]

Is there a difference in what data the Victron 600 and the Link 2000 provide? How do they differ from the Balmar SmartGauge and the Magnetronic or Mastervolt battery monitors?

[Wotname]

Originally Posted by a64pilot

...
Easiest thing is to add an ammeter to the alternator, alternator output of coursem is not true DC, but pulsed DC, but I assume that's irrelevant?


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You have assumed correctly!
The shunt will faithfully reproduce the varying DC current into varying DC voltage and the meter will read the average value of that voltage.

[Stu Jackson]

Originally Posted by Dr. Sea

1. Is there a difference in what data the Victron 600 and the Link 2000 provide?

2. How do they differ from the Balmar SmartGauge and the Magnetronic or Mastervolt battery monitors?

1. The same deal. Same algorithm in the circuit boards.

2. SG only tells SOC and voltage, no amp hour readings. I don't know about the last two.

[a64pilot]

I got the Smart Gauge based on Maine Sails tests, he says nothing is as accurate for determining SOC. I don't know, but have read his testing methodology on several things and have yet to find a mistake he's made.
Now total amp hours used would be interesting but I don't myself want another battery monitor, and install wise if you can screw in a light bulb, you can install a Smart Gauge.


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[model 10]

Originally Posted by Wotname

You have assumed correctly!
The shunt will faithfully reproduce the varying DC current into varying DC voltage and the meter will read the average value of that voltage.

I must have not paid attention. A shunt does not do anything except act as a resistor and an amp meter is really a millivoltmeter meter that measures the voltage drop across the shunt or resistor.

[Dr. Sea]

A64pilot,

The SmartGauge has received a lot of positive testimony from several different knowledgeable users. And the simplicity you described is rather appealing. Systems on cruising boats can get very complicated.

[Stu Jackson]

Originally Posted by a64pilot

I got the Smart Gauge based on Maine Sails tests, he says nothing is as accurate for determining SOC. I don't know, but have read his testing methodology on several things and have yet to find a mistake he's made.
Now total amp hours used would be interesting but I don't myself want another battery monitor, and install wise if you can screw in a light bulb, you can install a Smart Gauge.

a64,

Absolutely a good choice for determining SOC.

However, you have asked a completely different question in this thread.

All I'm sayin' is unless you can source a shunt and ammeter, and are willing to live with the potential downsides of having it in the AO + and all that entails as detailed by a good response above, then it may be far simpler and perhaps less expensive to just get the shunt that comes with the Victron and slap it in. You don't even have to USE the battery monitor features, just the amps readings, if you so desire.

ALTERNATIVELY, have you looked into Blue Sea? I know they sell ammeters, and they may have them with remote shunts.

You could also try Radio Shack.

Good luck, whatever you choose to do.

[Stu Jackson]

a64,

Too easy:

https://www.bluesea.com/products/801...00A_with_Shunt

They make a series of these in different amp maxs. Search there on "shunts."

[Frankly]

I am missing something here. I have a old Link 10 with a shunt installed in the negative return (3 sets of golf cart batteries). 100 Amp Balmar, Freedom 1000 I/C, bow thruster, and the normal assortment of small 12 Volt loads. I can determine what current is going in or out of the battery bank, ahrs, Voltage, ect. If I am motoring and want to actually know the alternator output, I typically just subtract approximate draw of what is on. If I couldn't handle all that math, just turn off all loads and then the alt is all that is left.

An old analog ammeter will work with a shunt in the positive leads, just have to protect the small sense wires as others have pointed out. Digital voltmeter maybe, maybe not.

Net in or out (Amps or ahrs) is typically what is important to me.

[socaldmax]

I don't see why these things have to be so expensive. I bought a nice digital 4 digit V and A meter with a compact display and shunt for about $12, delivered from Ebay. 0-100v, 0-200A, down to .01v and .001A. I measured accuracy at 13.6v and 10A with a calibrated DVM and it read within .01V and .01A, so that's close enough for me, especially for $12.


If you want to connect it to the positive side of your alternator, just make sure to swap the + and - so the meter is powered correctly, the shunt itself has no polarity. You can even measure current at the alt and voltage at the battery if you want to run the wire.


0 100V 200A DC Digital LED Voltmeter Ammeter Amp Volt Meter 200A Shunt 12V 24V | eBay

[Colin A]

The company I work for offers several different amp meters you can PM me if your interested. Most are designed for 100 amps max but we do have some 200 amp ones in stock as well.

[a64pilot]

I'll try to answer best I can as much as I can
It's apparently only the digital ammeters that won't work on the pos side without spending more money, and while I thought at first I wanted digital as they look nice and modern, it's apparent that it costs two or three times as much and it's just not worth the money to me.

Reason to not add a battery monitor is again, cost. Your looking at close to $200 and for an ammeter, that is more than I want to spend.

I'll likely go the Blue Sea analog route as I believe they match what's already there and cost is pretty reasonable.

But Frankly's post has me thinking, why not put a shunt in the neg side, and if you could find a 200 amp ammeter that shows both discharge and charge, then of course you would know the total number of amps either going in or out of the bank? You know the kind of meter where O is at the top, but the needle swings left for discharge, and right for charge.
Right now I have an ammeter that came with the boat that shows discharge only, I was going to add one that showed charge only, but logically it would seem one meter should be able to show both?

[Frankly]

Double pole, double throw, center off toggle switch will solve your meter polarity problem.

[jeepbluetj]

Originally Posted by a64pilot

...

But Frankly's post has me thinking, why not put a shunt in the neg side, and if you could find a 200 amp ammeter that shows both discharge and charge, then of course you would know the total number of amps either going in or out of the bank? You know the kind of meter where O is at the top, but the needle swings left for discharge, and right for charge.
Right now I have an ammeter that came with the boat that shows discharge only, I was going to add one that showed charge only, but logically it would seem one meter should be able to show both?

That's what I've got on my cheap boat. A cheap Chinese (smakn) 1-100A meter/voltmeter combo. It came with a shunt IIRC. The shunt is between the battery banks and my panel's neg bus. All current on the boat flows through that bus.

Meter shows + current during charge. Shows - during discharge. Works well enough that I can guess pretty accurately SOC. It's how I know how much the solar puts out, how much the fridge draws, etc... I can tell I'm out of enough solar to run the fridge when it goes - during the day. It works, was cheap, accurate enough after I calibrated it, etc...