I have the voltage chart that RoyB shows printed and one copy taped near my batteries and a second inside near a volt meter.
I bought a DC and a AC meter on ebay for $5 each including shipping. They have a blue light to them. I mounted them just inside my entry door because I had a 12v source from the O2 alarm and a 120v receptacle to power the AC meter. I wired in on/off switches. I now leave the DC on all the time. After 10 days my batt were still at 12.68 volts with the only draws being the radio's memory and the DC meter.
I have my battery status right in my face, every time I enter the rig.
