jmt0645 - Didn't you forget to mention the electric chair you have bolted in back there in the bed? I know with the setup you have you must drive around to the prisons "to give them a hand" with some of their "disposal" chores.
With the wiring and alternator you have, there are NO power losses. Things are fine just the way they are. 12.6V no load is fine too, especially if you didn't disconnect the cables from the batteries. With three batteries wired in parallel, the voltage you see will be that of the weakest one.
- Jack