Alt amp output shunt meter

[joe_db]

A good article on metering is here:

https://www.bluesea.com/support/articles/Metering/550/Strategies_for_Monitoring_DC_Current

Bluesea is a fan of using analog meters for alternator output. This gets around the issues of digital meters not being designed for + side shunts. They are pretty easy to get on FleaBay, example here:

http://www.ebay.com/itm/DC-100A-Round-Analog-Ammeter-Panel-AMP-Current-Meter-DH62-DC-0-100A-with-shunt-/171749372864?hash=item27fd0f73c0:g:PNsAAOSwj0NUdYuH

I have a lot of fun with cheap meters from FleaBay, but I have learned to use some test leads and run a test scenario before mounting them. They are about 10% of the price of "real marine meters", but they are not 100% good. I have got one or two bad ones in the bunch over the years. A car headlight bulb is a good test load for this. Among other things, you can verify the ammeter works both ways if you are using it like that.

[BadaBing]

I purchased a "shunt" amp meter as suggested. Remarkable. I think I was all of $12 through Amazon and I had it less than 36 hours after the order was placed. As my son so often says, "we live in the future"

Question.
Its no surprise that it was made in china or that the directions as a tad vague, at least to me.

.......
Any advise or thoughts are always greatly appreciated.

I installed this today and did my very best to follow the instructions, vague as they are, to the letter . It workith not.

Please take a look for me at the drawing above.

It shows a wire connected before "load" then the shunt with a wire attached on the in and our sides of the shunt.

The first wire seems to be for voltage, per the drawing. The next two wires for amp readings. The last two wires for power to the gauge itself.

First, in my situation, as I am wanting to see alternator output at a given moment, there is no load.

I attached the first wire, which is meant to be before load to a bower buss in the electrical box. I placed the shunt into the wire from the alt to the batteries. and connected the reading wires as directed.
Nada. The unit lights up and reads " -l . " and the -l does not seem to be a -1 just 3/4 of an H with the left leg missing.

Doing a return right now to Amazon but wanted your thoughts on the "load" question.

[BadaBing]

Typically the shunt is mounted in a location where it monitors net amps - the alternator is supplying, and everybody else is using. This net flow is most easily measured in the negative circuit just before the batteries, so every load is factored in. If you put the shunt in the alt + output line you will only measure "input" (amps better not flow backwards thru the alternator). I like to think of the electrical system the same as a plumbing system. Pressure and flow are not constant in either system. But the negative loop just before the batteries does "capture" the net flow. I think Neil could probably explain this better.

could be the issue.

[BadaBing]

I can see the value, I think , of monitoring the negative side. BUT from past experience, which is from long long ago. The charge wire from the alt went first to an amp meter, then to the batteries. Or so it seemed to me. ) = no current moving at all. + ? = amp putting out something, whatever the + reading was, -? = alt not working and current is flowing back from the batteries to feed the electrical needs of the engine. Of course I may be mistaken about it having been that way. But one reason for bypassing the old alt meter was that it required charge current to go through twice as much wire to get to the batteries. In a T30. aprox. 20' from alt to meter, then another 20' to the battery box. Considering the added distance = much added resistance It now goes from alt to selector to batteries, now between qtr. births = 15' to charge batteries.

All this other monitoring is very cool but all I am interested in is monitoring what the alt is pumping out in total.


So I looked up a bunch of similar shunt alt gauges and they all require attachment on the negative side of the system. Every poor diagram I looked at showed the shunt after the load. So I got to thinking, in my case the batteries ARE the load. I was going to return the purchased devise to Amazon so I had to remove it, bummer. Decided I might just as well give it a shot attaching the shunt just off the batteries on the ground side. What do yoiu know but it works, sort of.
At first it was showing 60 or so negative amps. Obliviously not true because as I watched the voltage display on the inverter started climbing, I had intentionally drawn down the batteries to just below 12V. Like 11.9, but a few minutes after stopping the intended draw down they settled at 12.4, where they were at restart. In just a few minutes we were back over 13V on the inverter display, but the new amp meter display was still showing much to much current, at 1800 rpm 60 Amps on almost charged batteries and the reading showed as -60 . Standing there wondering whats up with this I taped on the water circulation pump. Instantly the ampmeter started acting correctly showing 14.5 V, as the inverter was also displaying and 20 ish apms.

Aparently there is a gremlen in the wiring somewhere but for the moment Im calling this a partial victory. Would have prefered seeing the juice between alt and batteries but sometimers half a loaf is bertter than none and, none of this is actually needed to go sailing, be reliable, and have fun.
Thanks

[joe_db]

Make life easy on yourself. Get an analog shunt ammeter and avoid all the + side sensing issues with digital meters.
http://www.ebay.com/itm/DC-100A-Roun...sAAOSwj0NUdYuH for $14 or get a Bluesea meter for more http://www.ebay.com/itm/Blue-Sea-Sys...UAAOSwoBtW4cyI. There is no real way to do negative-side shunts on a normal alternator, it grounds through the case.

I can see the value, I think , of monitoring the negative side. BUT from past experience, which is from long long ago. The charge wire from the alt went first to an amp meter, then to the batteries. Or so it seemed to me. ) = no current moving at all. + ? = amp putting out something, whatever the + reading was, -? = alt not working and current is flowing back from the batteries to feed the electrical needs of the engine. Of course I may be mistaken about it having been that way. But one reason for bypassing the old alt meter was that it required charge current to go through twice as much wire to get to the batteries. In a T30. aprox. 20' from alt to meter, then another 20' to the battery box. Considering the added distance = much added resistance It now goes from alt to selector to batteries, now between qtr. births = 15' to charge batteries.

All this other monitoring is very cool but all I am interested in is monitoring what the alt is pumping out in total.

Thanks

[BadaBing]

Make life easy on yourself. Get an analog shunt ammeter and avoid all the + side sensing issues with digital meters.
http://www.ebay.com/itm/DC-100A-Roun...sAAOSwj0NUdYuH for $14 or get a Bluesea meter for more http://www.ebay.com/itm/Blue-Sea-Sys...UAAOSwoBtW4cyI. There is no real way to do negative-side shunts on a normal alternator, it grounds through the case.

This is exactly what I should have done. hindsight is 20/20

[romantic comedy]

The positive wire from my alternator goes to the battery select switch. I have the shunt in the wire between the alternator and the switch. It measures all the current from the alt.

[BadaBing]

RC
I expect I will add that guage as well.. I would justnditch the digital meter but i had already cut a hole to install it in. The round meter you have shown will fit nicely where the old amp meter lived. I need to back away, starting to have too many quages. This isnt the Starship Enterprise. The amp monitoring started as an unanswered question about what my qlt was putting out andntook on a like of its own before I could stop myself. The display on the inverter kept me updated that the t was putting out, and doing so adaquetly, just one unguarded questiin and I slid down the rebbit hole. oh well,it looks cool, and is another remindernthat the ignition key it tuned on.

[romantic comedy]

Bill, I dont recall posting a picture of my ammeter. I think mine is rectangle and analog.

I am sure you will work it out.

[ndutton]

Good on ya Bill

Bill,
Good on ya for taking a deep breath and having a realistic look at this. I have never seen any other boat system attract as much sphincter pucker as charging a battery and once on the slippery slope it seems there's no turning back. Aficionados monitor as many parameters as the San Onofre nuclear power plant and equipment purveyors work hard to convince you that you need a hairpin wound alternator that puts out a gazillion amps at idle, a serpentine belt kit to go with it, a multi-stage smart charger replete with temperature sensing, computerized battery monitoring systems with data link to a PC and don't forget automated battery combiners because us idiot boat owners are incapable of turning a battery switch. I'm not kidding, I've seen internet experts strongly recommend such a system. Approximate cost as described = over $3600.00 excluding tax, shipping and professional installation.

Dude, it's only a battery and folks have been cruising successfully for well over 50 years with electrical systems replenished with basic fixed point non-monitored charging systems that are consistently criticized by today's experts.

[hanleyclifford]

Make life easy on yourself. Get an analog shunt ammeter and avoid all the + side sensing issues with digital meters.
http://www.ebay.com/itm/DC-100A-Roun...sAAOSwj0NUdYuH for $14 or get a Bluesea meter for more http://www.ebay.com/itm/Blue-Sea-Sys...UAAOSwoBtW4cyI. There is no real way to do negative-side shunts on a normal alternator, it grounds through the case.

However, if you have an alternator with independent ground, such as a Balmar, just cable from the (-) post to the shunt and then to the engine block and you can accomplish your goal.

[joe_db]

True. A word of warning: Plenty of alternators, our Motorolas among them, have negative connections and are NOT case-isolated.

[hanleyclifford]

True. A word of warning: Plenty of alternators, our Motorolas among them, have negative connections and are NOT case-isolated.

There will be points for the member who figures out how to isolate the negative side on a Motorola and feed it out thru an isolated terminal. (Ready, Jerry?)

[BadaBing]

Bill, I dont recall posting a picture of my ammeter. I think mine is rectangle and analog.

I am sure you will work it out.

Must have been in my head. I went back lookimg for it and no it to be found. but we are on the same page

[sastanley]

True. A word of warning: Plenty of alternators, our Motorolas among them, have negative connections and are NOT case-isolated.

Just when I thought I was getting a handle on 12v DC, this statement is totally baffling me...at least as far as our 35amp Motorola's are concerned.