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Old 04-26-2008
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Wiring an Amp Gauge

Hi I have a SW marine amp gauge with internal shunt that I'm installing in my boat. It came with no wiring diagram but I found some generic instructions on the web. The instructions I found show one wire to the battery connection at the starter, and the other to the key switch.

I'm wondering if these are automotive instructions and may be different than a multiple battery marine application. (seems like maybe the battery switch should be involved rather than the key?)

btw, this is for a Volvo MD1B with starter/generator unit and two batteries

Thanks.
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Old 04-27-2008
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Safari, which way you wire it depends on what type of gauge you have (+ & - or just +) and what the scale is.

IMHO, if you are using a battery changeover switch, the most useful place to put it would be in the common connection to the battery switch ie. existing switch common wire to guage, new wire from gauge to switch.

I hope this helps.
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Old 04-27-2008
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Internal shunt ammeters can be put in anywhere as long as the current doesn't exceed their capacity. Doesn't really matter if it is in the positive or negative lead as long as the current doesn't exceed it's specifications and the leads are connected in the proper polarity. Use a small test load, like a 5W light and a couple of small jumper wires to experiment with it if you are unsure of the markings. By convention, the external shunt type ammeters are placed in the negative common lead from your battery bank DC common to the loads.

Whatever you do, make sure you place it somewhere where it is protected by breakers or fuses from exceeding its rated capacity. If it is internal shunt chances are it is not rated high enough to measure starting current, or alternator output, and is only suited for measuring house loads. I have two internal shunt ammeters, one measures solar panel output (always less than 5amps) and the other measures house loads (less than 25 amps). Neither is used to measure charging current, and the one high current device I have (the SSB) bypasses the ammeter.

Last edited by sailboy21; 04-27-2008 at 10:23 PM.
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Old 04-27-2008
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Quote:
Originally Posted by sailboy21 View Post
By convention, the external shunt type ammeters are placed in the negative common lead from your battery bank DC common to the loads.
I did not know that. Is there a reason for that?

I connected my ammeter (built into the electric pannel) into positive lead for no reason other than that seemed like a "thing to do".
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Old 04-28-2008
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Quote:
Originally Posted by brak View Post
I did not know that. Is there a reason for that?

I connected my ammeter (built into the electric pannel) into positive lead for no reason other than that seemed like a "thing to do".
..only that, done this way, it will continue to work when the batteries are isolated.

What you have done should work fine. Don't worry about it.
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