At idle when testing the voltage of my battery my multimeter shows about 14.4 volts. This is confirmed by a voltmeter plugged in to the cigarette lighter socket. I'm installing 2 voltmeters for my dual battery set up. I have 2 different sets/brands of voltmeters. When I hook up one of the voltmeters to the main battery it shows 14.4V at idle. Both of the second brand of voltmeter show a little over 12V. Same wiring. I'm thinking the brand that shows the same as my multimeter is correct. My question is regarding the brand that is only showing 12V. Is a voltmeter smart enough to measure the state of a battery minus the charge going into it when idling? In other words, is the rest state of my battery really only 12V and the voltmeter that indicates 12V smarter than the one that shows 14V at idle? Hope this makes sense.