Jason,
Are you charging your batteries with your inverter/converter (commonly just called an inverter), or are you using a off the self stand alone battery charger? If you are using an inverter/converter with a good 3 stage battery charger, you never turn off the charge function unless there is a maintenance issue. However, if you are using a stand alone automotive charger, it depends upon its quality and whether or not it has an automatic float charge function. If it is a good quality 3 stage charger with an automatic float charge function, you can leave it on as long as you are on shore power, but if not it will overheat/overcharge and damage your batteries. So you will have to answer your question depending on what you are using for a charger. If you are using a standard automotive charger, you turn on the charger at about 12.1 volts and off at about 14.2 volts.
As for the voltage reading on your command center, there is no adjustment and repairs will be expensive if you can find someone who is willing to work on a 27 year old electronic panel. The gauges in your command center are the old analog design that have a questionable accuracy rating at best. As I always tell owners who question the accuracy of their analog dash gauges, "They are for entertainment purposes only". If you want to know what the voltage of your house batteries is, look at the remote control on your inverter, and if you do not have one, get one.
Gerald
