Ammeter goes where?

[Golfdad75]

Since you guys are the smartest people I know maybe someone can tell me this. I have two ammeters on my boat. I assume one tells me how much is going out and one tells how much is charging. I want to trace the wires to see if I can get them working. Anybody know where I should start? I have been told the battery switch (draw) and the alternator for the charge. Any ideas would be appreciated. I am off for a couple of weeks and I would like to get this done.
Thanks

[Al Schober]

Well, you don't need two. I've got a battery monitor, and all current in and out of the battery goes through it.
What it does not monitor is any load that the alternator is supplying directly, ie: not coming from the battery.

[joe_db]

Some photos and diagrams might help.
There is a LOT to choose from here!
Direct reading meters - the full current goes through the meter.
Shunt meters - the current goes through a shunt and small wires go to the meter.
Hall Effect meters - the sensor is a small doughnut type thing the goes through and does not touch.
Analog meters can be 0-full scale or center 0 with + and - amps. Some digital meters can show reverse current and some cannot.
Meters can measure current at various places. I have one that measures alternator output and one that measures current in and out of the battery. Meters that measure current being used by the loads on a DC panel are common too.
The standard A4 wiring from the factory had a horrible implementation of a center-0 meter that actually did not measure anything on the negative side and had a lot of relatively thin wire for an alternator.

Original equipment type direct reading meter:


Analog shunt meters:



What a shunt looks like:

[joe_db]

Hall Effect sensor:


Digital meters can run from a shunt sensor or Hall effect, depends on the meter:

[romantic comedy]

Originally Posted by Al Schober

Well, you don't need two. I've got a battery monitor, and all current in and out of the battery goes through it.
What it does not monitor is any load that the alternator is supplying directly, ie: not coming from the battery.

I use two ammeters. One uses a shunt and, I am guessing, is wired like yours. It tells me the current to the battery. It matches the alternator output and reads to 100 amps. Basically it tells the alternator output.

The second ammeter is direct wired and goes to 25 amps. It tells me the house loads. I just want to know how much power is being used by the boat. If the loads go over 25 amps a breaker trips. I have it wired so I can by bypass the meter in the case of greater then 25 amps load. Dont remember that happening yet.