Here's my project, I have a large utility trailer that has it's own 12 Volt Battery and a Auxiliary 12 Volt Battery, either can be charged by a AC Charger or Solar panel, all controlled by a panel. I have a two way switch that allows me to chose the Charging source either the AC charger or the Solar Panel; this feeds into a 2nd two way switch that allows me which Battery I want to charge. I have a voltmeter on the 1st two way or Charging source switch; depending on the selection either AC Charger or Solar Panel will show me the voltage that the selected charger is putting out. Here's the problem, the voltmeter works great, when I select the solar panel it will show the voltage (depending on the sun, 4 to 18V). However, when I turn the 2nd two way switch to one of the batteries, the voltmeter will show the voltage of the selected battery. How can I isolate the Voltmeter so it only reads the voltage of the Chargers, not the batteries. I might add, not shown on my diagram; each battery has it's own voltmeter showing what each battery's voltage is.
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