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Old 03-28-2019, 09:53 PM   #1
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Amp meter installation

OK so I have sorted my battery problems out all all are charging well and holding phew.
I would now like to install an amp meter to monitor amp usage at a glance in a 12 volt system what amperage gauge would I need and how should it be installed.
Only concerned with monitoring my house batteries which are 2 x 130amp hour batteries.
Advise appreciated.
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Old 03-29-2019, 01:06 AM   #2
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Blue Seas has some amp meters with shunts. They make nice stuff.
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Old 03-29-2019, 05:25 AM   #3
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We have one of these. Works well
https://www.amazon.com/Victron-Energ...68428369&psc=1
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Old 03-29-2019, 05:38 AM   #4
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If you are like me, a 30 amp boat, electric stove and microwave, get an analog Amp meter installed in the galley. Otherwise, you, like me, will be making many trips to the breaker panel when preparing a big meal. LOL
I like the analog meters so you can watch the trend and start turning things off as you approach the upper limits.
I have put the microwave on switchable power. I move the power to the microwave to the inverter as necessary
It is just a personal preference for analog meters and gauges but I am stuck with digital meters and gauges.
Other things need attending before that.
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Old 03-29-2019, 06:21 AM   #5
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Hall-Effect Sensor for DC Ammeter -- no shunt

Quote:
Originally Posted by Phil23 View Post
OK so I have sorted my battery problems out all all are charging well and holding phew.
I would now like to install an amp meter to monitor amp usage at a glance in a 12 volt system what amperage gauge would I need and how should it be installed.
Only concerned with monitoring my house batteries which are 2 x 130amp hour batteries.
Advise appreciated.
Back in the day, the only way to do this was with a shunt, which is a very low-ohm resistor, and an "ammeter" which is really a millivolt meter measuring the voltage drop across the "shunt" (resistor).

The problem with the shunt is that you are now cutting and terminating your main circuit feed to put the shunt inline. If the wiring is larger than 10AWG (and it typically is), these terminations require special crimping tools and connectors. If (for whatever reason) you overload your shunt it will burn up and turn into a "fuse". For this reason, you cannot install a shunt in areas that could contain flammable vapors.

The more modern solution is to measure the magnetic field around the wire, which increases in direct proportion to the current flowing. The problem is that Hall-Effect sensors that can do this used to be very expensive -- but no more.

Here is a DIY version for $20, way less than the shunt based systems that cost >$200 and take half a day to install. Also, it's a digital voltmeter.

https://www.amazon.com/bayite-Digita.../dp/B01DDQM6Z4

Just feed the wire(s) through the ring, connect it to power and you're done.

Other nice features of this approach (aside from price):

- it shows you the amount and the direction of the current flow (charging vs discharging).

- You can feed multiple wires through the ring, with current flowing either way in each wire, and the meter will display the sum of the currents. For example, if your charger/alternator is putting out 60A and you are using 50A, this unit will tell you that your charge rate is 10A.

- Works equally well when used on the positive or negative wire.


Enjoy!
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Old 03-30-2019, 06:38 AM   #6
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The above device is great for monitoring amp flow , but most folks simply want a gas gauge ,,how full are my house batts? ,,to know when to get underway , or crank up the noisemaker.


It would seem to be a great device for trouble shooting a DC setup.
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Old 03-30-2019, 07:42 AM   #7
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Get a Victron SOC (State Of Charge) gauge. It will show you amps in, amps out, voltage, remaining percentage of battery bank capacity, and a number of other things. Works off a shunt in the negative battery cable.

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Old 03-30-2019, 08:48 AM   #8
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As mentioned above, get a Victron BMV-712 battery monitor. That particular model can be monitored from your phone.
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Old 03-30-2019, 10:03 AM   #9
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Ditto on the Victron state of charge gauge. It provides much more info than just how many amps you are using. It was one of the easier things that I have installed.
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Old 03-30-2019, 10:26 AM   #10
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A voltmeter tells you what you need to know, like the one on your electrical panel, or plug a $2 digital meter in a (used to be called) cigarette plug. Same for 120 volts, if the voltage drops from your ambient charge (i.e. less than 118 volts in my marina or 120 on my genset) you are overloading.
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Old 03-30-2019, 11:40 AM   #11
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Quote:
Originally Posted by FF View Post
The above device is great for monitoring amp flow , but most folks simply want a gas gauge ,,how full are my house batts?

You mean like this?

https://www.amazon.com/AiLi-Battery-.../dp/B07D35MFBQ


OP here simply asked for recommendations on an ammeter. With that and a voltmeter, you would know your SOC, but for $10 bucks more, you can have that too...and still no shunt.
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Old 04-09-2019, 11:18 PM   #12
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OK I have a 30amp analogue amp meter with a built in shunt where do I take the positive wire and the negative wire to and should I include a fuse in either of the lines.
Thanks
Phil
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Old 04-09-2019, 11:36 PM   #13
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That type of meter must be installed so ALL current to be measured goes through it. THat means depending upon where you want to mount the ammeter then you must feed all the house current through that meter with long, LARGE GUAGE wires to and from the batteries + to the meter then back to the boat wiring.

DO NOT DO IT. It is too small a capacity for the house batteries and it will not take long to blow it. It itself will become a fuse.

That is why the external shunt types are used so the major power wiring is disturbed as little as possible and not materially changed except for the shunt installation itself. Then from the shunt two light guage, likely #16 or # 14 AWG leads are run to the meter. These external shunt types only use , usually up to 50millivolts and 50 or so milliamps to make them work.

That meter is simply not suitable.
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Old 04-10-2019, 04:56 AM   #14
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Hi C lectric what is your opinion on the above mentioned meter mentioned by Riverguy ex Amazon.
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Old 04-10-2019, 05:27 AM   #15
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A SOC meter measures volts and amps going or coming from the batt set.

IT counts and remembers all the electron movement and will show a reading of what is currently remaining in the battery set.

A volt meter or amp meter shows an instant condition , has no memory.

If you need a "gas gauge" for the house batts the SOC meter is the simple way of knowing.

Here is one with a good reputation.

TriMetric Battery Monitor - - Bogart Engineering

www.bogartengineering.com/products/trimetrics.html
○Measures battery % full, based on amp hour measurements for accurate information on state of charge (SOC). This method is more accurate than monitors ...

[PDF]INSTRUCTIONS FOR - Bogart Engineering

www.bogartengineering.com/.../TM2030-Technical%20Manual%2006%202017REF....

IMPORTANT: The wiring installation for this meter, especially the shunt installation ... For warranty service, please email bogart@bogartengineering.com. ...... cause the “charge setpoints” to be achieved with a lower state of charge than ...
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Old 04-10-2019, 06:07 AM   #16
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An ammeter alone won't tell you anything other than the current flowing through the shunt at any given point in time.

Unless you are keen on fiddling / programming, in order to keep a traditional Ah counter accurate for SOC, the Balmar Smartgauge (SOC only) or the new Balmar SG200 are both of the "self-learning" type. They can remain accurate without fiddling, re-programming or getting out-of-sync with the bank due to PSOC partial state of charge usage or batteries that age and lose capacity. The new SG200 also works with LiFePO4 for those interested..

If you think you're interested in a traditional Coulomb or Ah counter you may want to read the article below so you can keep it dialed in better.

Making Your Battery Monitor More Accurate

Also the correct installation of any shunt based battery monitor is pretty critical.

Installing A Shunt-Based Battery Monitor




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Old 04-10-2019, 10:13 AM   #17
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Quote:
Originally Posted by Phil23 View Post
OK I have a 30amp analogue amp meter with a built in shunt where do I take the positive wire and the negative wire to and should I include a fuse in either of the lines.
Thanks
Phil
See attached schematic from the Blue Sea 8005 internal shunt analog (25A) ammeter. Your 30 amp unit will be essentially identical.

On the presumption that the circuit you are measuring already has overcurrent protection at it's source (please verify), and that overcurrent protection is sized correctly for the wiring between the source and the load, then you do not need to add additional OCP just for the ammeter.

Put the ammeter AFTER the OCP device and before the load(s) you want to measure.

re: (from the O.P.) "I would now like to install an amp meter to monitor amp usage at a glance in a 12 volt..."

Your 0-30A analog ammeter will do exactly that...but with zero extra effort, you could use one of the hall-effect type digital devices, which don't require you to cut any wires. Given these are only about 20-30 bucks, and can tell you much more than a 0-30A analog meter, I'm not sure why you wouldnt choose that route instead.
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Old 04-10-2019, 10:33 PM   #18
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Ok I can build boats, plumb boats and a 30 year veteran in marine coatings and associated resin systems however I am a complete "Bunny" when it comes to this electrical game.
Some quesions:
If I only wish to monitor my house batteries with my amp meter (I have purchased it so would like to use it if at all practical) would my house bank isolating switch be my load point or is there a reisk when both House and Start are run together, if so where would be my load point.
How do I ascertain I have over current protection at what ever load point I decide upon.
How do I ascertain the correct wire size to use and the fuse size.
Can I use my earth terminal from my batteries to the switch board as my negative connection

Thanks guys
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Old 04-11-2019, 08:25 AM   #19
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Quote:
Originally Posted by Phil23 View Post
Some quesions:
If I only wish to monitor my house batteries with my amp meter (I have purchased it so would like to use it if at all practical)

We're really going to need a bit more than this to go on, such as brand, make, model and amperage rating of shunt...
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Old 04-11-2019, 09:17 AM   #20
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I am a Magnum BMK user. Likely similar to the ones mentioned and not terribly expensive. And I do love it!!
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