Having just gone through something like this. Get your volt meter check the voltage out of the converter, then check the voltage where the converter line comes into the electric pannel. Check the voltage line going out of the pannel. Once done with that disconnet the battery cables and check the voltage there. All of the readings should be about the same. My factory spec. told me 13.8 max with 13.5 min. If all readings are good then your battery needs to be replaced. Or maybe something as simple as the disconnet switch was not engaged all the way.