The ammeter must be wired thru a shunt
It depends on what you want to read with the ammeter. If you want to know the charge and discharge rate of the battery the ammeter shunt would be in series with the charge line from the converter to the battery. When on shore power and the battery is being charged the ammeter would read in the + (positive) direction. When on battery power, if you turn on a light or run the pump the ammeter will read in the - (negative) direction.
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