Alternator Shunt and Meter

[btrayfors]

a64pilot,

You asked a good and logical question at the beginning of this thread. Many folks who responded don't seem to understand what you were intending to do, and why.

I did, because I've had such a setup on my boat for many years (pics), i.e., a simple analog ammeter which directly measures alternator output. It is via a shunt in the positive output cable.

The meter is named "Phoenix" (I tend to name many of my boat's equipment pieces).

I've found it to be extremely useful to give an indication of alternator performance at various RPMs and stages of battery charging. It also gives a good indication of how well the regulator is functioning (in my case, the Balmar MC-612).

Paired with a good digital voltmeter, I've found it's all I need....no need for an "amp counter".

It's mounted where it can be easily seen from anywhere in the cabin, and the analog needle is all I need to see.....don't have to squint to try to read digital numerals in sunlight as I might have to with a digital ammeter. The digital voltmeter shown in the second picture is an illustration of this....you can't read it because of the glare.

Ditto for the two analog meters shown below in the second pic. These are AC volts and AC amps from the diesel generator.

FWIW,

Bill

[Wotname]

Here is what I use and the FWIW, the ammeter is in the positive side.

Tells me what is going into or out of the battery but as I only have alternator charging, whatever is going in must be from the alternator .

[Wotname]

Originally Posted by btrayfors

…...

It's mounted where it can be easily seen from anywhere in the cabin, and the analog needle is all I need to see.....don't have to squint to try to read digital numerals in sunlight as I might have to with a digital ammeter. The digital voltmeter shown in the second picture is an illustration of this....you can't read it because of the glare…….

An often overlooked point IMO.

[Tikka]

On most boats the house battery a bit further than in the car. In most cases the plus wire from alternator to battery can be use as a shunt.
Ideal would be micro amp meter with a couple of resistors for calibration .
No charging is affected and no weakness introduced.

[svlamorocha]

Originally Posted by Tikka

On most boats the house battery a bit further than in the car. In most cases the plus wire from alternator to battery can be use as a shunt.
Ideal would be micro amp meter with a couple of resistors for calibration .
No charging is affected and no weakness introduced.

Wonderful idea!

Sent from my GT-I9192 using Cruisers Sailing Forum mobile app

[HappyMdRSailor]

Originally Posted by Tikka

On most boats the house battery a bit further than in the car. In most cases the plus wire from alternator to battery can be use as a shunt.
Ideal would be micro amp meter with a couple of resistors for calibration .
No charging is affected and no weakness introduced.

Smartypants!

[Colin A]

I have used several hall effect DC meters in the past they work well the ones I tested fell within about .075 A (usually better) of the reading on the shunt meter on my workbench running from 0-50 amps. I believe the Maretron pickups works this way and several other digital monitoring systems. We talked about it for out panels but we decided to stick with shunts for now mainly due to cost and known reliability. On some of commercial ships board we used some by CR magnets but they are insanely expensive. We also built out own little board using a honeywell transducer but even that ended up quite a bit more expensive then a shunt.

[exMaggieDrum]

Blue Sea has several shunts and meters available. One of them should work for you. https://www.bluesea.com/search/results/shunt

[daveNZ]

Cable length.
As an aside, I assume it does not matter if the shunt is wired via an extra e.g. an extra 2 metres of cable, for the house battery negative to shunt and back to starter battery -ve.

I want to get the shunt out of the engine bay as the Victron 700 has some exposed electronics on a small PC board. Also this would create a large -ve post, it would be next to the 2 x (+ve lead) battery switches, and so I would have an accessible place to temporarily connect a battery charger, or jumper leads (I have no Emergency Parallel switch, so carry some heavy duty jumper leads)

[14p]

Im confused here, I bought a cheap digital volt ammeter batt moniter, and it flat out says negative cable shunt only, well all 3 shunts in my boat, both alt shunts and the batt shunt are in the positive cable. I bought this cheap 14$ meter to use only as a digital ammeter, to try to figure out why one alternator only picks up the load if I turn the other alternator off. It refuses to share the load. Anyway my question is regarding the shunt being placed in the positive cable, maybe I am missing how the internal dig ammeter works and am wrong about being able to wire it in the pos cable, but from what I can see all you have to do is swap the ground power input to the battery and place the positive power input on the shunt, the load side of the shunt if using as alternator ammeter. Am I missing something, it seems simple... here is a crude, very crude drawing of what I am trying to say here, and also attatching the instructions from the meter how to wire it on the neg side.

The round spotted thing at the bottom is my led bulb using as a load

Thanks

[14p]

Well I tried to edit that last message to delete that crude blue and red draawing and add this one here, but it wont let me edit it. This drawing I have the shunt in positive line instead of negative like the instructions say it must be wired, also has wires color coded to match wire colors of battery gauge instructions. Disregard that blue red drawing. All I did was swap the gauge power wires so instead of the gauge ground connection being tied to the shunt, the red power wire is on the shunt load side, and the gauge ground is now connected to the battery. I dont see why this wont work, but looking for input before I smoke my cheap 14$ gauge.
Here is the gauge https://www.amazon.com/gp/product/B07KXCF8F8
Thanks

[14p]

Here is a better picture of the imstructions that say it cannot be wired with shunt in pos cable, I just dont see why it cant be wired and work with the shunt in pos cable like my drawing. Power is being wired to the gauge correctly.. just dont see why their directions say it cannot be wired this way?

[smac999]

Why are you replying to a 6 year old thread.
Where is the report button gone.

[14p]

Ok I will post a brand new thread with the same question if that will make you happy.

[goboatingnow]

Most of what’s written is this thread is quite frankly rubbish by the way

High speed hide sensing , which is the current term , has traditionally been more expensive , because the electronics have to cope with a non grounded sense voltage , however these days you can easily get the required high side sensing amplifiers ( still reLatively expensive )

Most cheap dc powered ( ie powered from the system they are sensing ) can’t sense high side properly , so be careful ( primarily because the internal op amps can’t handle common mode voltages at or above the supply voltage

High side is always better , if you can do it

I’m in the process of converting all my sensing to high side , so I can extract separately all my charge source currents and my consumption currents