Your Year Model Newmar. AS others stated, the 13.8 is actually the Converter putting out the needed 12 volt power. IF you have charged the batteries and they do NOT read at least 12.6 or more the batteries are bad. Most likely a dead cell. Have you checked the Battery water? Now, your year, have you pushed the USE button on the Disconnect panel when plugged into shore Power? Newmar's wired their RV'
s a little different and you will get the volt reading on the INtellitec panel even if the Battery Disconnect is OFF. If you push STORE, the red LED will remain ON, but the batteries will be disconnected from the Converter charge system. So, if you had new Batteries a year ago and you were plugged into shore Power, BUT THE BATTERIES WERE DISCONNECTED AND YOU DID NOT REALIZE THAT DUE TO THE RED LED ON THE DISCONNECT PANEL, Your batteries would go dead after 2 or 3 weeks, as Newmar connected the LP/CO detector's direct to the batteries and not thru the disconnect system and that would kill the batteries. Doug