WSLM,
I think you need to check your meter or your converter.
Without knowing the manufacturer/model of the converter, the only thing anybody can do is GUESS.....
Some converter chargers used to grab the house circuit and supply it separately while it was charging the house bank.
If this is the case with yours, you have a problem. Are the interior lights real Bright??
If no, check your meter.
Check your car battery when it has been sitting a while.
That should be real close to 12.6V
Unplug at least the converter and let things sit for a while.
That should be real close to 12.6V - too.
If the converter is really putting 16V to the house bank, it will kill it by over heating it and drying out the cells.
Matt