This meter isn't one of the high dollar meters, you just read your 6volts from the 4.8 side, no big deal. Irun two batteries and one battery, 6 volt and 4.8 volt. Sort of what kind of mood I'm in when I'm building and setting up a plane. With two batteries you want two switches and batteries of the same volt and mah. Ieven run one 6 volt battery with two leads going into two different switches. Most the time it's the switch that fails and not the battery. In this case it's a big sub C pack with very high mah with the battery being double wired.
So much has beer writen about batteries and it comes down to the pilots choice. Horizon has come out and stated you should have a 6 volt system in your plane if you are running there digital servos and 2.4., they only give you the 4.8 though.